Drug-MembraneInteractionsSignificanceforMedicinalChemistry.pdf

See discussions, stats, and author profiles for this publication at: https://www.researchgate.net/publication/42608077
Drug-Membrane Interactions: Signiﬁcance for Medicinal Chemistry
Article in Current Medicinal Chemistry · March 2010
DOI: 10.2174/092986710791111233 · Source: PubMed
CITATIONS
72
READS
888
3 authors, including:
Some of the authors of this publication are also working on these related projects:
Drug profiling View project
NanoAgeless View project
Marlene Lúcio
University of Minho
93 PUBLICATIONS 1,566 CITATIONS
SEE PROFILE
All content following this page was uploaded by Marlene Lúcio on 01 July 2014.
The user has requested enhancement of the downloaded file.

Current Medicinal Chemistry, 2010, 17, 1795-1809 1795
0929-8673/10 $55.00+.00 © 2010 Bentham Science Publishers Ltd.
Drug-Membrane Interactions: Significance for Medicinal Chemistry
M. Lúcio*, J.L.F.C. Lima and S. Reis
REQUIMTE, Serviço de Química-Física, Faculdade de Farmácia, Universidade, do Porto, Rua Aníbal Cunha, 164,
4099-030 Porto, Portugal
Abstract: Generally drugs can act on the level of different biological membranes as well as inside the cells that are lim-
ited by membranes. Even in the latter situation, drugs must still interact with the membrane in order to cross it and reach
their targets. For this reason, the efficiency of drugs to interact with the membranes constitutes one of the most important
pharmacological features playing an essential role in their biological activity.
Membranes are the gathering place of many proteins and lipids, and are the structures where most cellular activities occur.
Although drugs bind to proteins and regulate their activity, the membrane lipid phase is no less important. Great part of
compounds studied induces structural changes in the lipid phase resulting structural defects, which in turn disturb mem-
brane function and indirectly modulate membrane proteins.
This paper reviews the clinical significance of drug-membrane interaction studies with a special focus in the lipidic com-
ponents of the membrane and reinforcing the importance of these studies in the field of medicinal chemistry since they
constitute stimulating opportunities for understanding drugs mode of action and toxic effects and cannot be overlooked
during drug design and synthesis.
Keywords: Drug-membrane interactions, lipid membrane, lipidomics, multidrug resistance.
1. INTRODUCTION
All living cells are separated from the surrounding envi-
ronment by a membrane that provides more than just a sim-
ple barrier. Indeed, biological membranes maintain the es-
sential differences between the cellular and extracellular-
environments and grant structural framework for important
cellular processes (e.g. biochemical, metabolic, signalling,
genetic, detoxifying, sorting, biosynthetic, lytic and recy-
cling processes). The current view of biological membranes
emphasizes the dynamic coupling between the structure and
function of membranes [1]. Structurally, membranes are
complex supramolecular liquid-crystalline assemblies mainly
composed of phospholipids. These phospholipids form a
bilayer matrix in which other biomolecules such as proteins
and cholesterol are embedded [2-5]. Structural integrity of
membranes ensures their protective and transport functions
which belong to the most important membrane roles. Mem-
brane protects the cell, among others, against various adverse
external factors, in particular against toxic chemical com-
pounds and xenobiotics in a more general sense. This func-
tion is closely associated with the transport function that
consists in controlling substance selective permeation across
membranes.
For their important role in life maintenance, biological
membranes are the subject of interest of many different natu-
ral sciences. Basic research has been performed by biolo-
gists, biochemists and biophysicists, where as more applica-
tion oriented research is conducted by the medical and phar-
maceutical sciences, namely in the context of medicinal
chemistry and drug research developments [6-8]. Of special
interest are studies on the structure and function of mem-
brane proteins since they perform various active life func-
tions, such as the conduction of chemical reactions and many
*Address correspondence to this author at the REQUIMTE, Serviço de
Química-Física, Faculdade de Farmácia, Universidade, do Porto, Rua Aní-
bal Cunha, 164, 4099-030 Porto, Portugal; Tel: +351-222078966; Fax:
+351-222004427; E-mail: mlucio@ff.up.pt
biophysical processes. With the assumption of the leader role
of membrane proteins in the regulation of cellular processes,
drug discovery and development has typically considered
interactions between the ligand (drug) and molecular target
(e.g., protein receptor) [8-10]. According to this, currently
most clinical drugs are developed to interact directly with
proteins and it is increasingly common that new molecular
entities for clinical use are designed to modulate the activity
of membrane proteins [11]. Therefore, it is probably fair to
say that the protein component of the membrane has cast a
long shadow for quite some time over the lipidic membrane
content. In turn, the lipid phase has been often treated as an
inert, structural element of the membrane that supports the
proteins and acts as a passive surrounding environment [12,
13]. However, this passive view of the membrane is progres-
sively changing by recent discoveries showing that mem-
brane lipids are involved in crucial cell functions that justify
the presence of many different types of lipids. Increasing
evidences argue in favour of the lipidic central role in regula-
tion of a myriad of cellular processes proving that lipids are
not only the structural backbones of cell membranes and
sources of metabolic energy [11, 14]. Actually, lipids are
essential cellular constituents that have multiple and distinct
roles in cellular and metabolic functions (see [1, 15-17] for
reviews). Briefly, besides constituting a physical scaffold for
membrane proteins and forming barriers that isolate and de-
fine cells and organelles, lipids participate in the interaction
of proteins with the cell barrier and also regulate the distribu-
tion and localization of peripheral proteins to membrane do-
mains where they can interact with other signalling proteins
[11, 18]. Moreover, the alterations in membrane-lipid com-
position and structure appear to be related to the develop-
ment of numerous diseases [2, 11, 18].
The facts described highlight the prominent role of lipids
in cells and suggest that they might constitute novel targets
for drugs whose pharmacological effects would be associated
with the modulation of the physicochemical properties of
membranes [2, 11, 18]. Since the activity of membrane pro-
teins can be regulated by lipids, it is conceivable that drugs

1796 Current Medicinal Chemistry, 2010 Vol. 17, No. 17 Lúcio et al.
that are capable of influencing lipid organization could
modulate the activities of these membrane proteins and/or
associated signalling mechanisms.
Therefore, drug–membrane interactions represent a wide
and complex field in medicinal chemistry and can involve
studies of drugs that are capable of influencing the protein
function both directly and indirectly via lipid modulation.
The protein regulation achieved by drug-membrane interac-
tions can finally induce changes in cell signalling and gene
expression, which might serve to reverse the pathological
state.
The literature on drug-membrane interactions is vast and
multifaceted. In view of this, the present review will be re-
stricted to clinical relevant examples of applications of drug-
membrane interaction studies to medicinal chemistry focus-
ing on the effects of compounds over the membrane lipidic
content, since this aspect is most times overlooked.
2. DRUG-MEMBRANE INTERACTIONS: WHERE
AND HOW CAN BE STUDIED?
The lipid components of natural membranes belong to
three principal groups: phospholipids, glycolipids and ster-
ols. Cholesterol is a major eukaryotic membrane component
from the sterols group that strongly affects the molecular
organization of membranes as well as the function of many
membrane processes, including membrane transporters and
membrane transport itself [19, 20]. The protein components
of the biomembrane can differ in a great extent according to
the cellular function [2]. Additionally, membranes are also
composed of carbohydrates which locate mainly in its exter-
nal surface covalently bonded to proteins (glycoproteins) and
lipids (glycolipids).
The perception of biomembrane organization has con-
tinuously changed since Singer and Nicholson first intro-
duced the fluid mosaic model in 1972 [4, 5, 21]. At present,
biological membranes are pictured as solid domains with
segregated regions of structure and function coexisting with
fluid membrane lipids [22-25]. These domains can present
distinct compositions and physical features at varying length
scales resulting from lipid/lipid or lipid/protein interactions,
or can be cholesterol enriched domains with an accumulation
of membrane proteins (rafts) [26, 27].
Despite of the structural complexity of biomembranes
and even if the exact proportion of membrane components
changes with the type of membrane, the chemical basic
structure of a membrane can be defined as a lipidic bilayer
where proteins are inserted. However, the specific influence
of lipid molecules on the activity of membrane proteins is
poorly understood. To identify the effect of the lipid bilayer
structure on the function of proteins whether integrated in or
associated with biological membranes, suitable model sys-
tems are indispensable [3, 28-30]. Indeed, model membranes
with only a few components can provide valuable insights
into the properties of more complex biological membranes.
These models can be created in various forms (micelles,
liposomes, supported lipid bilayers and monolayers) and by
different methods according to the aim of the study.
Micelles are colloidal aggregates of amphipathic mole-
cules, which occur at a well-defined concentration called the
critical micelle concentration. In polar media such as water,
the hydrophobic part of the amphiphiles forming the micelle
tends to be oriented within the cluster and away from the
polar phase while the polar parts of the molecule (head
groups) tend to be exposed to the polar micelle solvent inter-
face. Despite the fact that micelles are composed of single
lipid or lipid-like layers rather than bilayers, and their sur-
face curvatures are significantly higher than those encoun-
tered in real cellular membranes, micelles have been exten-
sively used as biomimetic systems for membrane environ-
ments and for deciphering structural features of drug-
membrane interactions [29, 30].
One of the advantages of micelles for studying drug-
membrane association has been the observation that such
assemblies have: rapid molecular tumbling in aqueous solu-
tions; facilitated structural characterization of the incorpo-
rated drugs and their interactions with lipids and proteins can
be studied using important bio-analytical techniques such as
high-resolution nuclear magnetic resonance (NMR), Fourier
transform infrared spectroscopy (FTIR), and circular dichro-
ism (CD) [30]. According to the type of amphiphiles used, it
is also possible to prepare micelles with different surface
charges, and interpret the electrostatic effects of drug binding
to these membrane model systems. Furthermore, micellar
systems have the unique property of being able to solubilise
both hydrophobic and hydrophilic compounds. For that rea-
son they are used extensively in industry for detergency and
as solubilising agents [29].
The hydration method of a lipid thin film generates dis-
persions and causes bilayer formation. Lipid bilayers that
surround an aqueous space are generally designated as
liposomes. These can be multilamellar as well as unilamel-
lar. Spontaneously formed liposomes are usually multilamel-
lar (MLVs) and inhomogeneous in shape. However, various
techniques can be used to reduce the size of vesicles and the
number of bilayers (e.g. by ultrasound, so-called sonication
and extrusion through polycarbonate membranes [31, 32]) in
order to obtain unilamellar vesicles. Despite their size het-
erogeneity, the use of MLVs has been essential in varied
solid-state nuclear magnetic resonance (NMR) studies of
drug-membrane interactions. Indeed, lipid multilamellae
provide sufficient sample quantities and acceptable signal-to-
noise ratios, but also, critically, maintain a favourable time-
regime for the solid-state NMR (31
P and 2
H) experiments
which allow the study of structure, dynamics, and orientation
of drugs in membranes regarding their insertion into the hy-
drophobic interior of the bilayer and the extent of headgroup
disruption, which can in turn establish drug action and/or
toxicity relationships. Similar to NMR, differential scanning
calorimetry (DSC) and small angle and wide angle X-ray
scattering analyses (SAXS and WAXS) require relatively
large sample quantities for probing modifications of the lipid
phase transitions induced by the drugs interacting with
membranes. These techniques have been applied to probe the
ordering and molecular packing of lipid bilayers within
MLVs prior and following interactions with drugs. Several
studies utilizing these methods in model lipid systems have
yielded quantitative information on the effects of drugs on
membrane structure, as well as on drug localization within
the lipid bilayer [33-47]. Specifically, DSC has been applied
in multilamellar phospholipid systems to probe the thermo-

Drug-Membrane Interactions Current Medicinal Chemistry, 2010 Vol. 17, No. 17 1797
dynamic profiles of the lipid assemblies and the conse-
quences of drug interactions in term of ordering and coopera-
tive properties of the bilayers [41, 48].
Unilamellar vesicles are classified according to their size:
small unilamellar vesicles (SUVs) have a diameter below
100 nm; large unilamellar vesicles (LUVs) have higher di-
ameters [3, 31, 32]. Recently, giant unilamellar vesicles
(GUVs) of a comparable size to the lipid biomembranes (in
the m scale) have become a popular tool to study mem-
brane organization and interactions [49]. Unilamellar vesi-
cles have been widely used for studying membrane processes
in general and drug-membrane interactions in particular.
This is due in most part to the fact that conceptually such
vesicles mimic a cell assembly – in which the lipid bilayer
forms an enclosed volume separated from the external solu-
tion. Larger-size vesicles have been generally preferred as
model systems for studying membrane processes since their
curvature more closely resembles actual cells [50, 51]. In
view to this, unilamellar vesicles have been used in combina-
tion with spectroscopic techniques to evaluate membrane
association and permeation by drugs, and to correlate the
biophysical data with the pharmaceutical activities of the
drugs. Circular dicroism (CD) spectroscopy has been an im-
portant tool for probing secondary structures of vesicle-
associated enzymes and to study the changes in protein con-
formation induced by drugs [52-54]. Electron spin resonance
(ESR) experiments have usually employed spin labels cova-
lently attached to the membrane lipid acyl chains at various
positions being an important tool for studying drug insertion
into the bilayer and the resultant modification of bilayer flu-
idity and lipid motion [43, 55]. Furthermore, a large number
of studies have employed fluorescence leakage techniques to
probe the effect of drugs on the membrane. In such experi-
ments the changes in the fluorescence of probes entrapped
within unilamellar vesicles are monitored following interac-
tions of the drugs with the vesicles. Specifically, pore forma-
tion or complete bilayer destruction by the drugs may result
in leakage of the encapsulated fluorescence dyes, thereby
significantly modifying [increasing or reducing] their fluo-
rescence emission [56, 57].
Besides monitoring dye leakage, numerous fluorescence
experiments have recorded the emission of trypthophane
residues within enzyme sequences, either Trp residues within
the native sequences or inserted intentionally. The method is
based on the high sensitivity of the spectral position and in-
tensity of the fluorescence peak to the hydrophobicity of the
Trp environment, thus providing a measure of the depth of
bilayer insertion of the peptide [58, 59]. Binding studies of
the drugs to enzymes are also possible by analysing the
quenching efficiency of the Trp fluorescence using adsorp-
tion models like Langmuir isotherms or Scatchard plots [58,
59]. Other fluorescence techniques have used dyes embed-
ded within the lipid bilayer, either physically incorporated or
covalently bound to the lipid moieties. Such experiments
were similarly designed to evaluate the penetration and bi-
layer localization of the drug by fluorescence quenching
studies [47, 60-65]. Another fluorescence technique particu-
larly suited to measure the interaction of molecules in mem-
branes is the Fluorescence Resonance Energy Transfer
(FRET). In this case, a direct transfer of energy from a fluo-
rescent donor to an acceptor fluorophore occurs upon donor
excitation through a non-radiative mechanism. The effi-
ciency of the energy transferred is strongly dependent on the
distance between donor and acceptor [1, 58]. Because of
smaller distances required between donor and acceptor,
FRET possesses the clear advantage of quantifying distances
well below the resolution limit of fluorescence microscopy,
thus measuring dynamic interactions with membranes at the
molecular scale by FRET will be highly relevant in the fu-
ture.
In all bilayer systems, the physical phase state of the
membrane is mainly determined by lipid composition, tem-
perature and water content. Monolayers at the air/water in-
terface constitute a different approach to obtain model mem-
branes with well defined physical phase states. Monolayers
mimic only one leaflet of biological membranes. Neverthe-
less, since the thermodynamic relationship between mono-
and bilayer membranes is direct, monolayers are often used
to study lipid/protein interactions under specific conditions
[66]. The Langmuir film balance setup allows the lateral
surface pressure as well as the molecular area within the
lipid monolayer to be adjusted. The ability to know and con-
trol this precise structural information is the most significant
advantage of this system as compared to the bilayer model.
Furthermore, planar systems generally model the phosphol-
ipid ordering within cellular membranes, and can be also
designed to mimic the lateral organization of cell surfaces
[67]. In many instances, physical analyses of monolayers are
conducted by thermodynamic methods (pressure-area iso-
therms). Pressure-area isotherms allow studying the interac-
tion of drugs with lipids using two different approaches. One
approach consists on spreading a lipid monolayer on the wa-
ter/buffer surface and compressing it to a surface pressure of
30 mN/m by applying lateral pressure. At this surface pres-
sure, lipid packing density is similar to that of a cell mem-
brane, and the lipid monolayer mimics the outer surface of a
cell membrane. By maintaining the lipid area constant,
changes in surface pressure are recorded upon addition of
drugs to the subphase. Alternatively, a lipid/drug is spread
over a subphase (usually a buffer with pH 7.4 is used to
mimic biological systems) to form a monolayer in a Lang-
muir trough. The monolayer is then compressed, and the
pressure-area isotherms of the pure lipid and the lipid with
drug are compared. With this method is also possible to
evaluate the phase transitions of the lipid monolayer and how
are these phase transitions changed upon the interaction of
drugs which may have a rigidifying or a fluidizing effect and
thus it is possible to evaluate the drug-induced biophysical
changes of the membranes [46, 57, 68-75]. Apart from
physical studies, changes in lipid morphology at the air-
water interface can also be studied using microscopic tech-
niques: atomic fluorescence microscopy (AFM), Brewster
angle microscopy (BAM) and cryogenic scanning and
transmission electron microscopy (cryo-SEM and cryo-
TEM) [72, 76-78]. Moreover, recent developments have en-
abled the application of surface-sensitive X-ray like grazing
incidence X-ray scattering (GIXD) and neutron scattering
techniques for characterization of molecularly membrane
structure sheets constructed via Langmuir monolayers and
for the study of the effects of drugs on membrane biophysi-
cal aspects like lipid order and tilt angles [46].

Monolayers can also be transferred to solid supports. The
vertical transfer on a hydrophilic substrate produces Lang-
muir-Blodgett (LB) films [79]; the horizontal transfer on a
hydrophobic substrate yields Langmuir-Schaefer films [80].
In a similar way, bilayers, can also be either supported by a
solid substrate or free-standing like black lipid membranes
(BLM) [81]. Together they constitute the solid-supported
lipid monolayers and bilayers which are also popular
biomimetic membrane systems since they allow examining
peptide interactions at the lipid/water interface while at the
same time limiting lipid motion through surface immobiliza-
tion. Limiting lipid mobility in supported lipid layers might
turn such systems in a more realistic model compared to
Langmuir films since this better resembles lipid dynamics
within real membranes. In addition, supported bilayers on
solid substrates have become particularly useful for measur-
ing secondary structures and orientations of peptides and
drugs in lipid environments by using spectroscopic tech-
niques such as attenuated total reflection Fourier transform
infrared spectroscopy (ATR-FTIR) [82].
More recently, alternative models made of lipid bilayer-
modified microbeads and nanomaterials [54] have been use-
ful. The microbeads and nanomaterials-supported lipid bi-
layers (nanoSLBs) somewhat mimic the native environment
for membrane-associated biomolecules. Thus, from a bionic
point of view, they can be considered as curved lipid mem-
branes with high structural integrity [54]. Compared with
other lipid membranes, an attractive feature of nanoSLBs is
that some states of mimetic biomembranes could be moni-
tored by tracking the changes of some intrinsic properties of
the nanomaterials. Thus, the nanoSLBs could be used as a
biomembrane model studying some membrane properties
and biological functions, such as the fluidity of membranes,
and the interaction between proteins and membranes [54].
3. RELEVANCE OF THE DRUG-MEMBRANE
INTERACTION STUDIES FOR MEDICINAL CHEM-
ISTRY
3.1. Contribution for the Research and Development of
New Drugs
The pharmaceutical industry is coming under increasing
economic pressure to bring greater efficiency to the drug
discovery process. To avoid bigger investments in drugs that
might not be effective it is required a rapid identification of
potential problems relating to administration and transport of
a candidate compound. Therefore, the assays selected for
pharmaceutical profiling should provide information on how
the compound performs at a barrier. In this way, the medici-
nal chemist can envision how a structure can be modified to
improve properties that optimize the passage through a bar-
rier. A compound encounters many barriers on its path to the
therapeutic target. The barrier might be physical (mem-
brane), physicochemical (solubility, pH) or biochemical (me-
tabolism). Each barrier attenuates the amount of compound
reaching the therapeutic target [83].
A rational drug design for pharmaceutical purposes must
thus consider that inside our body there will always be recip-
rocal interactions between drugs and membrane barriers.
Therefore, it must be recognised that the characteristics of
drugs may affect their penetration and/or location within
membranes. Furthermore, the effects on membranes, which
can arise from the presence of drugs, can vary from changes
in lipid conformation, microviscosity and surface charge to
phase separation and channel or domain formation. These
effects correlate with further consequences like alterations of
membrane permeability with resultant cell shape changes or
membrane fusion [84] and ultimately may be responsible for
severe changes in the performance of the cell, including the
function of transmembrane receptor proteins and proteins
responsible for signal transduction which, in turn, are inti-
mately related to the molecular-level mechanisms of action
(or side effects) of the drugs [43].
On the other hand, biomembranes can be rather different
depending on their physiological function (e.g. membranes
which have higher metabolic activity contain higher portions
of protein), or even their state of functionality (e.g. some
diseases affect membrane structure, composition and surface
charge) and these different structural, biophysical and
chemical aspects of membranes can influence the way as
drugs or other compounds penetrate or interact with mem-
branes thereby modulating also their pharmacological activ-
ity or their undesirable side effects Fig. (1).
A major question to understand the above-mentioned
drug-membrane interplay is the nature of diffusion and
transport of drugs across cell membranes. Indeed, as most
drugs are administered orally, their ability to transport across
the intestinal epithelium, a monolayer of cells that line the
interior of the intestine, is an important issue. Concepts of
membrane transport and diffusion have evolved with the
increased understanding of the structure of cell membranes
[4, 9, 10]. The movement of species across the membrane is
accomplished either by passive diffusion across the mem-
brane or by some facilitated transport process, which may be
associated with a membrane protein or a smaller transport
molecule. Although mediated transport processes are espe-
cially important to the normal functioning of the cell, these
transport processes are frequently not available for the mem-
brane movement of added therapeutic agents. Therefore,
transmembrane passive diffusion is the primary process of
membrane translocation for many drugs from the blood
stream into various regions of the body including the brain
[85, 86].
Elucidation of the mechanisms affecting the passive dif-
fusion of compounds through the lipid membrane is thus of
primary importance in drug development. Accordingly, the
physical-chemical properties of drugs, namely their pKa (de-
termining the ionization state at several physiological pH)
and their hydrophilic/lipophilic balance (determining their
water/lipid solubility and distribution) are usually fundamen-
tal features that should be considered when designing drugs
for pharmaceutical applications [6, 7].
Based on the abovementioned, efforts have been con-
ducted to develop predictive models that can be used for
screening drugs that will be mostly effective in vivo. These
models include suspended monolayers of human intestinal
epithelial cell lines (Caco-2) that can be used to predict ab-
sorption in vivo and to identify drugs that are not well ab-
sorbed. These cell line studies have the advantage of needing
only small amounts of drugs. However, differences in the

absorption properties of different regions in the gastrointesti-
nal tract cannot be considered. Furthermore, when studying
slowly absorbed drugs, the model often deviates from in vivo
results [10, 87].
Besides cell lines, a physicochemical high-throughput
screening system (PC-HTS) using a parallel artificial mem-
brane permeation assay (PAMPA) for the description of pas-
sive absorption processes has been developed [10, 88].
PAMPA is based on a 96-well microtiter plate assay, with a
hydrophobic filter material in each well working as a support
for bilayers of lecithin. This process allows measuring the
permeation through the lipid layer of hundreds of com-
pounds per day. Several related assays have been developed
based on this approach (see [89, 90] for a review)
Very recently, a so-called “surface plasmon resonance”
(SPR) biosensor technique has been developed that allows
the differentiation and prediction of the degree of transcellu-
lar (t), paracellular (p) and actively absorbed (c) drug frac-
tions from the human intestine [10, 91]. The method uses
liposomes attached to a surface sensor. The interaction be-
tween drug and liposomes is directly measured by SPR
which is sensitive to changes in refractivity index at the sen-
sor surface produced by changes in mass.
Other fast screening tests for evaluation of the drug-
membrane permeability include biochromatography. Accord-
ing to this, drug-membrane interactions can be simulated by
introducing biomembrane-mimetic systems into a chroma-
tographic system. This is the basis for the immobilized artifi-
cial membrane chromatography (IAM) and immobilized
liposome chromatography (ILC) [10, 92].
These short term in vitro assays have been the mainstay
of drugs screening methods and new molecules are beeing
developed on the basis of results obtained in studies explor-
ing the interactions of the parent compound with membranes.
Some examples can be found in the literature, like the studies
of parent anti-parasite drugs, such as dapsone or atovaquone,
which by chemical derivation originate other effective com-
pounds against Pneumocystis pneumonia, like pentamidine
and its analogues [93]. The same type of drug-membrane
studies was conducted in phenothiazines and thioxanthenes,
recognised as powerful in reversing anticancer drugs resis-
tance in carcinomas. The influence of molecular alterations,
made on those parent compounds, was analysed on their
ability to reverse doxorubicin resistance in carcinoma and
leukemia cell lines [94-97]. These studies have reached to
the conclusion that there are several molecular structures of
Fig. (1). Schematic representation of drug-membrane interaction studies as novel tools for clarifying molecular-level mechanisms of action
(or side effects) of the drugs. Drug-physical chemical properties and membrane properties influence drug-membrane interactions with resul-
tant effects of drugs on membranes (effects on membrane structure, surface charge, fluidity) and effects of membranes on drug molecules
(effects on drug location and partition between aqueous and lipid phase).

phenothiazines and thioxantenes found to be essential for
drug resistance-reversing activity, and thus new compounds
should be designed accordingly.
New antibiotic drugs are also emerging from the conclu-
sions obtained from the studies of drug-membrane interac-
tions. Recent studies have evidenced that PMBN, a cationic
peptide, is able to disrupt or disorganise lipid membrane
structures, being able to perturb the outer membrane of bac-
teria. Therefore, PMBN and other cationic fusogenic pep-
tides can be developed to increase antibiotic susceptibility in
resistant bacteria strains by increasing their membrane per-
meability [98].
3.2. Development of Drug-Delivery Systems
Effective disease targeting represents an enormous bio-
medical challenge in the treatment of cancer and other seri-
ous illnesses since the lack of selectivity of current therapeu-
tic agents’ results in numerous severe side effects, including
organ and tissue damage. In fact, for an increasing range of
modern drugs, toxicity towards key organs resulting from
indiscriminate delivery can lead to significant and sometimes
lethal side effects, thus greatly limiting their therapeutic
value.
Lipids of various types have been extensively studied for
drug delivery by different routes of administration.
Liposome is one such example of drug delivery system in
which, amphiphilic lipids reorganize into circular lipid bilay-
ers enclosing an aqueous phase, and it has been widely in-
vestigated for drug, protein and gene delivery [99]. By opti-
mizing the lipid composition, liposomal size, membrane flu-
idity, surface charge, and steric stabilization, it is possible to
extend the therapeutic index of liposomal carriers over that
of the corresponding conventional formulations. Actually,
bioavailability, drug delivery efficiency, and high selectivity
strongly depend on the diffusion of the encapsulated drug
across the liposomes walls, which in turn is determined by
optimizing the liposome formulation [41].
Likewise, when designing novel cationic lipids for gene
therapy, their ability to mediate transfection relies on numer-
ous physical factors, including the spontaneous condensation
of the DNA due to electrostatic interactions, the net positive
charge of the system that may promote association with
negatively charged cell surfaces, as well as the fusogenic
properties of the lipids which can destabilize the plasma
membrane or endosomal compartment. Finally, the rationale
behind the use of liposomes for immunization purposes can
be attributed to their capacity to deliver an antigen into se-
lected immune cells and to stimulate an immune response
[100].
In the case of drug delivery systems applied to transder-
mal drugs, penetration of drugs remains an even greater con-
cern. The effectiveness of transdermal drug delivery depends
on the ability of drugs to penetrate the skin in sufficient
amounts to reach therapeutic levels. However, skin consti-
tutes an important barrier to exogenous chemical absorption
being comprised of corneocytes embedded in multilamellar
lipid domain [101, 102]. To counteract this, it is generally
agreed to use penetration enhancers in drug formulations,
since they may increase the permeability of drugs by affect-
ing the intercellular lipids of the skin via extraction or fluidi-
zation [103] and/or by increasing the partitioning of the drug
into the skin [104] and/or changing conformations within the
keratinized protein component [105]. Drug-membrane inter-
action studies are thus fundamental while exploring bio-
medical applications of drug delivery systems for in vivo use
especially to optimize the different kinds of carriers. Moreo-
ver, the complex process of cellular uptake and intracellular
trafficking of these nanosystems also demands great knowl-
edge of interactions with membranes. In fact, studies have
shown that the interfacial properties of nanocarriers signifi-
cantly affect their interactions with the biological environ-
ment [106]. Furthermore, the size and hydrophobicity of
nanomaterials used play important roles in their uptake by
the cells of the mononuclear phagocytic system and their
eventual clearance by the reticuloendothelial system [107,
108]. In this matter, the interaction of drug delivery systems
with the membrane should be the first step to be studied
since understanding the biophysical interactions of nanocar-
riers with cell membranes is critical for developing effective
systems for drug delivery applications. Finally, it is also es-
sential to be aware of any characteristics of nanomaterials
that might cause toxic effects [109-111].
3.3. Understanding Therapeutic and Toxic Effect of
Drugs
Studies in cell culture and in vivo have shown that drug-
lipid interactions play a significant role in the pharmacoki-
netic properties of drugs, influencing their transport, distribu-
tion, and accumulation. Ultimately, drug-membrane interac-
tions control the effect of the drugs used since it frequently
results from interference with cellular function. In fact,
membrane receptors for the recognition of endogenous trans-
mitters are obvious sites of drug action. Moreover, drugs can
affect cell function by altering the activity of transport
systems. Drugs may also directly interfere with intracellular
metabolic processes, for instance by inhibiting or activating
an enzyme. In all of these cases, the effect of drugs can result
from a direct interaction with the proteins working as
receptors, transport systems or enzymes, or may simply
result from a membrane perturbation leading to changes in
membrane curvature or to phase separation and, thus, to
changes in protein conformation. In contrast to drugs acting
from the outside on cell membrane constituents, agents
acting in the interior of the cell need to penetrate the cellular
membrane. Therefore, understanding the role of membrane-
drug interactions on the pharmacokinetic properties of drugs
is critical to understand drugs mode of action or even their
toxicity. Depending on the composition of the membrane and
the structure of the drug molecules, the interaction can
favour or prevent drug pharmaceutical activity or toxicity.
Fortunately, as already mentioned, most of the perturbations
that can occur in complex biological membranes upon
interaction with drug molecules can be studied and simulated
in vitro and quantified by available physicochemical
techniques and using model artificial membranes.
A variety of drugs from different therapeutic classes
(anti-inflammatory, antibiotics, antifungal, anti-parasite, car-
diovascular, antipsychotic, anticancer, anticonvulsive and
anaesthetics) have been investigated for their interaction with
lipids using different chemical and biophysical techniques on

Table 1. Examples of studies Covering the Interactions of Model Lipid Membranes with Drugs of Different Therapeutic Groups.
Some Representative Lipid Alterations and their Relation with Therapeutic/Toxic Effect of Drugs are Presented
Therapeutic group Main conclusions References Relation with therapeutic/toxic
effects of drugs
NSAIDs :
Flurbiprofen Interactions with membranes are dependent of cholesterol content. [139]
Salicilic acid (SA) SA locates at the lipid-water interface region neighbouring the glycerol
moiety and increases fluidity of the headgroup region of the membrane.
[35, 40]
Nimesulide,
Indomethacin,
Acemethacin,
Piroxicam,
Tenoxicam,
Lornoxicam,
Meloxicam
NSAIDs increase membrane fluidity in cells and liposomes in the fluid
phase.
Piroxicam has membrane fusogenic properties and increases membrane
permeability.
Membranes in the gel phase have shown to be differently perturbed
according to the NSAID tested.
NSAIDs locate in the membrane both in the hydrophobic core and in the
membrane surface with the ionized carboxyl group neighbouring the
polar group of the membrane.
[46, 52, 140]
Tolmetin Tolmetin is located at the membrane surface. [47]
Interactions of NSAIDs with lipid
bilayers are expected to play a
major role in guiding the inhibition
of the membrane-associated en-
zymes (COX) which are the princi-
pal targets for these drugs in con-
trolling pain and inflammation.
The ability of NSAIDs to bind to
surface-active phospholipids, as
well as their effect on the lipid
dynamic properties of membrane
models may relate with the effects
of these drugs compromising the
integrity of gastric mucosal barrier.
Anticancer drugs:
Gemcitabine Gemcitabine does not perturb the biomembranes while their acyl deriva-
tives exert destabilizing effect on biomembranes.
[37, 41]
Arrylchloroethylureas
(CEU)
CEU has a rigidifying effect on membrane model and locates with the
aromatic ring in the polar surface and the radical between the acyl
chains.
[36, 44]
Ellipticine (ELPT) ELPT presents higher incorporation into mixed cholesterol systems. [141]
Doxorubicin (DOX) DOX changed membrane microviscosity. [55]
Polynuclear platinum
drugs
Interactions of drugs with phospholipids is dependent of charge and
occur in two steps in which the non covalent interaction is the first
stage.
[39]
Taxol Taxol has a fluidifying effect on saturated phospholipids in the gel phase
and has a slight rigidity effect on unsaturated fluid lipids.
[142]
These studies have demonstrated a
correlation between the cytotoxic
activity of different antitumor
agents and their location within
membrane or their effect on mem-
brane fluidity, which also depends
strongly on lipid composition.
Antimicrobial drugs:
Antifungals (Ampho-
tericin B and deriva-
tive: MF-AmB)
AmB binds to model membranes with high affinity and spans the mem-
brane. MF-AmB has stronger affinity with ergosterol compared to the
affinity for cholesterol.
[38, 143-
148]
Fluoroquinolones
(Ciprofloxacin, Moflo-
xacin)
Depending on the chemical structure of the drug, it interacts with the
headgroups of phospholipids and does not penetrate in the bilayer or
penetrates more deeply on the bilayer.
[33, 149,
150]
Macrolides
( Azithromycin - AZT)
In membrane models AZT increases fluidity and leads to erosion and
disappearance of gel domains, but does not alter permeability. These
effects are dependent of lipid composition.
[56, 151-
153]
Membrane interactions, as a part of
the mechanism of action and expla-
nation for toxicity, are shown for
antimicrobial drugs:
Stronger affinity for ergosterol
compared to cholesterol justifies the
lower toxicity presented by an
antifungal drug.
Interactions of Fluoroquinolones
with membranes have implications
in the efflux of drugs from bacteria
and can clarify cellular accumula-
tion and intracellular activity.
The undesirable toxicity of macrol-
ides and aminoglycosides seem to
be related with their membrane
effects.

(Table 1). Contd…..
effects of drugs
Aminoglycosides Aminoglycosides bind to the acidic phospholipids which accumulate
into the brush border of renal cells during hypoperfusion or ischemia.
The accumulation of aminoglycosides into lysosomes changes the prop-
erties of lysosomal membranes leading to formation of myelin bodies
and eventually to phospholipidosis which may be a cause of nephrotox-
icity.
[130, 154]
Antipsychotic agents:
TFP and CPZ affect zwitterionic monolayers only to a small extent.
Large effects are seen at the phase transition, cooperativity and mor-
phology of negatively charged monolayers meaning that changes in a
large number of lipids extend far beyond the site at which the drug is
bound.
[75]
CPZ has higher interactions with monolayers of acidic glycerophospho-
lipids which can be related with the same lipids in nerve cell membrane.
[68]
Trifluoroperazine
(TFP) Chlorpromazine
(CPZ)
CPZ binds rapidly to phospholipid bilayers disturbing molecular order-
ing of phospholipids and causing membrane disruption as reported in
haemolysis and changes in erythrocytes morphology. At low concentra-
tions CPZ penetrates on the bilayer. At high concentrations the drug
disrupts the lipid bilayer and induces aggregation.
[81, 155]
The mechanism of antipsychotic
drugs and their pharmacological
efficiency is related to non specific
interactions with the membrane.
Higher interactions of these drugs
with acidic or negatively charged
lipids may explain the effect in the
same type of lipids that exist in
nerve cell membrane and ultimately
may explain the indirect effect on
proteins involved in signal trans-
duction.
Interactions of these drugs with
membranes are dependent on
concentration and may also relate
with the toxic effects.
Cardiovascular
drugs:
-blockers (Propra-
nolol, Carvedilol)
A concentration dependent partition coefficient between lipid and water
media was derived. Drug-membrane interactions were pH dependent.
[156-160]
Angiotensin antago-
nists ( Losartan)
Losartan interacts with phospholipid membranes by affecting transition
temperature and molecular mobility.
[42, 43]
Calcium channel
blockers
(Nimodipine, Am-
lodipine, Verapamil)
Amlodipine locates at the bilayer surface and in the hydrophobic part of
the lipid membrane. Nimodipine appears to be randomly dissolved in
the hydrocarbon layer with no interactions with the membrane head-
groups. The partition of Verapamil into phospholipid membranes was
examined.
[42, 43, 45,
161]
Anticoagulant
(Dipyridamole)
Binding is the same for neutral form of the drug independently on the
charge of the micelle suggesting a nonspecific hydrophobic binding.
[162]
Knowledge of the ionization state
of membrane-embedded cardiovas-
cular drugs and Kp determination is
important regarding drug accumula-
tion in tissues and drug attraction by
certain lipids in the vicinity of
membrane proteins. This may also
clarify the mechanism of action of
drugs binding to specific receptors
(e.g. -adrenergic or Angiotensin)
which are located in membranes.
Membrane location of Verapamil
and Dipyridamole could also be
related with their capacity regulat-
ing PgP.
Anti-epileptic and
anti-convulsivant
drugs:
Phenytoin (PHN),
Carbamazepine (CBM)
Both drugs interact with membrane model systems.
Drugs are inserted in the outer layer of the erythrocites’ membrane
inducing a disordering effect on the polar head groups and acyl chains.
[163]
Valproic acid (VPA) VPA causes membrane disordering effects and makes flip-flop across
plasma membrane of the neurons.
[164]
In the case of CBM and PHN the
cytotoxicity at cell membrane level
can be evaluated by the interaction
of these drugs with membranes. In
this context, the use of erythrocites’
membranes provide an explanation
of haematological alterations in-
duced by CBM, since the alteration
of the normal red blood shape to a
spiculated form increases erythro-
cyte resistance entering capillaries
and thus decreases blood oxygena-
tion.
These studies support the assump-
tion that VPA has no specific bind-
ing site, and thus may act directly
on the plasma membrane, possible
as membrane-perturbing agent.

(Table 1). Contd…..
effects of drugs
Anti-parasite drugs:
Miltefosine (HePC) Penetration of HePC was more difficult in monolayers with smaller
contents of unsaturated lipids and lower fluidity similar to membranes in
parasites resistant to HePC.
[165]
Quinine Association of quinine with liposomes is controlled primarily through
electrostatic attractions and in lesser extent by hydrophobic forces.
[166, 167]
Anti-parasite drugs’ activity in-
volves the interaction and further
intercalation into the membranes of
parasites. In this matter, evaluation
of electrostatic and hydrophobic
interactions plays a crucial role in
both the quinine-membrane affinity
and the location of the drug. Fur-
thermore, interactions of HePC with
membranes permitted to conclude
that the cases of drug resistance
occur because the penetration of
drug in membrane is more difficult
since the membranes of these resis-
tant parasites are less fluid.
Anaesthetics drugs:
Local anaesthetics
(LA)
Disrupting effects of LA in membranes are mainly an effect of hydro-
phobic interactions, since most LA are relatively hydrophobic ionisable
amines that undergo partitioning into lipids.
[168-171]
General anaesthetics Purely hydrophobic anaesthetics will preferentially be located in the
lipid membrane hydrocarbon core, while amphipathic molecules may
distribute preferentially to the membrane interface.
Anaesthetics can have several effects on membranes: thickening mem-
branes and increasing their surface tension; changing lateral pressure
profiles in membranes; decreasing the phase transition temperatures of
bilayer membranes and thus increasing fluidity; altering lipid order and
domain formation; producing lateral phase separation; changing mem-
brane electrical properties such as membrane dielectric constant or sur-
face dipole potentials.
[172-175]
There is a long standing evidence of
action of anaesthetics in lipid phase
as well as new information about
the nature of the interaction.
Effects of LA on the structural and
dynamic properties of the mem-
brane could be responsible for some
of the toxic effects caused by these
drugs.
Studies on anaesthetics have sug-
gested a strong involvement of a
nonspecific impeding action of
these compounds on the lipid bi-
layer in their neurological effects.
Furthermore these drugs alter the
biophysical properties of membrane
affecting membrane dynamics in
living cells.
model membranes. Table 1 shows a summarised list of some
important examples of how drug-membrane interactions can
modify certain membrane properties and affect their biologi-
cal functions and how this can be related with the therapeutic
actions of some therapeutic classes of drugs, or even with
their toxicity.
3.4. Understanding Mechanisms of Multidrug Resistance
The term “multidrug resistance” (MDR) is used to de-
scribe the ability of cells exposed to a single drug to develop
resistance to a broad range of structurally and functionally
unrelated drugs [95]. Such resistance can be achieved by
cancer cells as well as by bacteria and yeast. In all cases
MDR constitutes a major obstacle in the (chemo) therapy of
a disease. Several mechanisms are involved in the MDR
phenomenon: interference with apoptosis, overexpression of
transport proteins that exclude drugs from the cell or altera-
tion of enzyme activity. Among these mechanisms, the over-
expression of P-glycoprotein (PgP) on the plasma membrane
is frequently observed in drug-resistant cancer cells leading
to the failure of chemotherapy [112-114]. PgP is an integral
membrane protein that also modulates drug absorption,
bioavailability, tissue deposition, and excretion. Therefore,
not only anticancer drugs but also several other drugs are
known to be efficiently pumped out from the cell by PgP
which thus plays an important role in compromising AIDS
chemotherapy and other drug-treatable diseases [115-117]. A
common conclusion emerging from the studies performed
about the MDR modulation was that the interaction of drugs
with the lipid bilayer was a primary determinant for substrate
recognition of PgP. Consequently, substrate binding to PgP
should be considered in two steps, the initial partitioning of
drugs to the lipid bilayer followed by binding to transmem-
brane region of the enzyme [114, 118-121]. Despite this
knowledge, conventionally, drug-lipid interactions are ne-
glected, either as a possible explanation for increased intra-
cellular concentration of the substrate in studies of PgP func-
tion, or as a way of finding inhibitors of the PgP. Indeed,
apart from the interaction of MDR modulators with trans-
porter proteins their interaction with plasma membrane lipids
may also contribute to reverse the molecular mechanisms of
multidrug resistance. According to this, if a drug is able to
induce alterations of bilayer properties, especially altering
fluidity and permeability, should play an essential role in the
processes of multidrug resistance modulation. Hence, most
of the MDR reversing agents are preferentially soluble in
lipids and they may also exert the influence on physical
properties of lipid bilayers [122-124]. For example, phe-
nothiazines, considered as MDR reversing agents affect the

properties of lipid bilayer causing phase separation in mem-
branes containing lipid microdomains of sphingolipids and
cholesterol [123]. These induced changes in the lipid envi-
ronment of membrane transporters like PgP can affect either
drug export or import [123].
In conclusion, perturbation of lipid phase of cell mem-
brane by modulators seems to be important for potentiating
the anticancer drug therapy and other therapies which effi-
cacy is affected by MDR mechanisms [123].
3.5. Controlling Enzymatic Inhibition
Thousands of cellular proteins (enzymes or receptors) in-
teract with membranes in different ways. Integral (trans-
membrane) proteins are embedded in the lipid bilayer and
their activity is sensitive to changes in the lipid environment
[18]. Peripheral (amphitropic, extrinsic) proteins bind to
membranes in a reversible manner and their activity is regu-
lated by membrane-lipid organization [125]. A growing body
of evidence has shown that lipid-bilayer structure and dy-
namics play a key role in membrane functionality by indirect
disturbance of protein functionality [126]. Hence, the lipid
disturbance by the uptake of drugs, can lead to changes in
many membrane properties which then can induce severe
alterations in the performance of the enzymes and receptors.
In fact, binding of drugs to membrane lipids can lead to al-
terations in the function of proteins as shown for phospholi-
pase A2 [127], 5-lipoxygenase [128], cytochrome c oxidase
[129], lysosomal phospholipases, phosphatidylinositol speci-
fic phospholipase C, sphingomyelinase [130], and protein
kinase C [131]. For instance, it has been reported that the
inhibitory effect of the mycotoxin Fumonisin B1 on cerami-
de synthase activity might not be a typical enzyme–inhibitor
type direct interaction, but a consequence of mycotoxin-
induced changes in the dynamic organization of the lipid
phase [132].
Consequently, in addition to specific interactions be-
tween drugs and enzymes, drugs that act as enzymatic inhibi-
tors are also likely to modify the bulk physical properties of
the membrane. The mechanism of these effects on membrane
biophysics is an area of current interest and therefore justi-
fies the increasing interest to study drug-membrane interac-
tions [133].
3.6. Controlling Cellular Signalling
In recent drug-membrane studies regarding the drug de-
velopment and search for novel therapeutic compounds, the
hegemonic status of membrane proteins in relation to their
lipid constituents has begun to change. Whether the aim is to
purify and characterize a novel membrane protein or to initi-
ate efforts at rational drug design receptor, the lipids and the
proteins must now be considered as partners involved in a
complex molecular relationship [13]. These recent advances
have created a recent research field called lipidomics cou-
pled with the recognition of the role of lipids in many
physiological conditions and metabolic diseases such as obe-
sity, atherosclerosis, stroke, hypertension and diabetes [11].
This rapidly expanding field [134-136] complements the
huge progress made in genomics and proteomics, all of
which constitute the family of systems biology.
One of the most important physiological roles of mem-
brane lipid composition and structure is their pivotal partici-
pation in cell signalling. Membrane lipids contribute in dif-
ferent ways to signalling: they constitute a selective barrier
to hydrophobic hormones and hydrophilic signalling mole-
cules; they are able to control the activity of membrane sig-
nalling proteins by keeping a certain composition and fluid-
ity; they influence the interaction of signalling proteins by
maintaining a net negative surface charge at the inner leaflet
of the membrane provided mainly by phosphatidylserine and
they provide many of the important cell signaling molecules
via phospholipases and lipid kinases. Key is the role of
phospholipase C in hydrolyzing phosphatidylinositol
bisphosphate (PIP2) to release diacylglycerol that activates
protein kinase C (PKC) and inositol triphosphate (IP3),
which mobilizes intracellular Ca2+
, central to so many regu-
latory processes. The phosphorylation of PIP2 at the 3-
position to produce PIP3 promotes vesicular trafficking and
other cellular processes. Phospholipase D releases phos-
phatidic acid, and phospholipase A2 provides arachidonic
acid, which is converted into prostaglandins, leukotrienes,
and lipoxins; these ligands in turn bind to unique families of
receptors as does platelet activating factor (PAF). The more
recent recognition of the importance of sphingolipids and
ceramide in signaling and the discoveries of the unique lys-
ophosphatidic acid and sphingosine phosphate families of
receptors has sparked the search for other new receptors for
lipids.
Among these different contributions of lipid membrane
in cell signalling, we will focus on the effect of the mem-
brane structure on the interaction of key signalling proteins
such as G proteins with membranes. These proteins are cru-
cial for cell communication, as they propagate messages
received at the plasma membrane towards inner cell com-
partments. Thus, they are active players in adaptations of
cells to environmental messages and in the complex re-
sponses that involve both changes in protein activities and
gene expression. G protein-coupled receptors (GPCRs) con-
stitute about 80% of the known receptors for neurotransmit-
ters, hormones and neuromodulators and about 5% of the
genes in eukaryotic organisms [1]. They propagate the mes-
sages received through peripheral G proteins [1]. When an
agonist ligand binds to a GPCR, a G protein molecule is then
activated. The intracellular G protein, in turn, acts as a signal
transducer that regulates the activity of ‘effector proteins’
(e.g. adenylyl cyclase, guanylyl cyclase, phospholipase C,
ion channels, etc.) which produce a second messenger (that
may propagate the signal to further messengers). To generate
the G protein pool around GPCRs required for the cell sig-
nalling process it is important the accumulation of non-
lamellar forming lipids like phosphatidylethanolamine (PE).
Indeed, the pseudo-conical shape of lipids such as PE fa-
vours its organization into HII phases and such non-lamellar
propensity was first shown to increase the binding of hetero-
trimeric G proteins. The binding process of G proteins to
GPCRs is terminated when lamellar regions (e.g. lipid rafts)
provoke a rapid exit of G proteins from the receptor envi-
ronment. This mobilization of the G protein a subunit away
from GPCR-rich membrane domains may facilitate its inter-
action with effector proteins (e.g., adenylyl cyclase) that
might be present in other regions of the membrane [1, 2, 11,
137].

Malfunctions of GPCRs can be linked to diseases such as
certain forms of blindness, obesity, inflammation, depres-
sion, cancer and hypertension, among others. In view to this,
most drugs under pharmaceutical development are targeted
at GPCRs, because of the great variety of functions they con-
trol and their involvement either in the aetiology of diseases
or in reversion of pathological states. Although GPCRs have
gathered the attention of medicinal chemists to delineate
therapies, G proteins themselves have not been on the focus
of the design of therapeutic drugs. The possibility to regulate
G protein activity through modulation of their lipid environ-
ment has been recently used to develop drugs for treatment
of cancer, obesity, hypertension, etc. [1, 2, 11, 137, 138].
Thus, changes in the membrane lipid structure and/or com-
position may regulate the interaction and activity of these
and other peripheral proteins and their corresponding signal-
ling pathways. This approach, called membrane-lipid therapy
[1, 2, 11, 137, 138], aims to develop drugs that are capable of
influencing lipid organization through principles of struc-
ture–function, inducing a concomitant modulation of mem-
brane-protein localization and activity. This type of modula-
tion can finally induce changes in cell signaling and gene
expression, which might serve to reverse the pathological
state. Some insight already exists into the effects of dietary
lipids [1, 2, 11, 137, 138] or certain drugs (e.g. anesthetics
and alcohols) [1, 2, 11, 137, 138] on membrane structure and
function. Furthermore, the activity of various anticancer
drugs is being associated with their ability to alter the mem-
brane lipid structure. Indeed, daunorubicin, hexamethylene
bisacetamide and minerval all alter the nonlamellar- phase
propensity of membranes [1, 2, 11, 137, 138]. Moreover,
edelfosine and miltefosine are also targeted to membranes [1,
2, 11, 137, 138].
Other membrane-lipid therapies are related with the
modulation of heat shock proteins (Hsp). Indeed, ageing and
other pathological states or even subtle alterations in mem-
brane lipids (by causing ‘membrane defects’) may influence
membrane-initiated stress-signalling processes by changing
the global fluidity, the membrane thickness and the local
organization of microdomains. The formation of ‘defects’ in
response to stress within the membrane microdomains is
causally linked to the dysregulated expression and, at least in
part, to the abnormal intra or extracellular localization of
specific Hsp. In this context, membrane microdomains repre-
sent new therapeutic targets. In fact, a targeted and distinct
reorganization of membrane microdomains with drug candi-
dates acting according to the principles of ‘membrane-lipid
therapy’ [1, 2, 11, 137, 138] best represented by the lipid-
interacting hydroxylamines, has been shown to be coupled
with the simultaneous normalization of the dysregulated ex-
pression and cellular localization of Hsps in such prominent
disease states as type 2 diabetes and amyotrophic lateral scle-
rosis [1, 2, 11, 137, 138].
4. CONCLUDING REMARKS AND FUTURE
PERSPECTIVES
The current understanding of lipids, their active role in
cellular processes and the biophysical and chemical proper-
ties of membranes are the result of many years of intensive
research. The following years present stimulating opportuni-
ties for the study of membranes, in which many issues that
remain unclear are likely to be elucidated, thanks to the de-
velopment of increasingly powerful experimental techniques.
In this context, the interactions of drugs with membranes
were reviewed herein, providing examples of applications of
drug-membrane interaction studies in a medicinal chemical
perspective. In fact, the effects of drug-membrane interac-
tions is reflected in the possibility to apply the knowledge
gathered in such research studies to develop therapies against
several diseases, including cancer and other diseases that
may benefit from drug-induced membrane-lipid perturbation.
As a result, the studies reviewed offer iconic examples of
drug-membrane interactions and can be considered as start-
ing points for further exploration mainly directed to re-
searchers working in the field of lipid membranes in biologi-
cal and model systems. Hence, studying the interactions of
drugs with different membrane proteins; membrane compo-
sitions, levels of hydration and pH, as well as studying inter-
actions of drugs with the lipid microdomains are fertile fields
for future investigation and can provide useful information to
understand the therapeutic effects of drugs in addition to,
their different selectivity, and toxicity. Ultimately such stud-
ies may prove valuable in the design of novel drugs formula-
tions with increased efficacy and reduced side effects.
ACKNOWLEDGEMENTS
Partial financial support for this work was provided by
Fundação para a Ciência e Tecnologia (FCT – Lisbon),
through the contract PTDC/SAU-FCF/67718/2006.
REFERENCES
[1] Vigh, L.; Escriba, P.V.; Sonnleitner, A.; Sonnleitner, M.; Piotto, S.;
Maresca, B.; Horvath, I.; Harwood, J.L. The significance of lipid
composition for membrane activity: new concepts and ways of
assessing function. Prog. Lipid Res., 2005, 44(5), 303-344.
[2] Escriba, P.V.; Gonzalez-Ros, J.M.; Goni, F.M.; Kinnunen, P.K.J.;
Vigh, L.; Sanchez-Magraner, L.; Fernandez, A.M.; Busquets, X.;
Horvath, I.; Barcelo-Coblijn, G. Membranes: a meeting point for
lipids, proteins and therapies. J. Cell Mol. Med., 2008, 12(3), 829-
875.
[3] Simons, K.; Vaz, W.L.C. Model systems, lipid rafts, and cell mem-
branes. Annu. Rev. Biophys. Biomol. Struct., 2004, 33, 269-295.
[4] Singer, S.J. Some early history of membrane molecular biology.
Annu. Rev. Physiol., 2004, 66, 1-27.
[5] De Weer, P. A century of thinking about cell membranes. Annu.
Rev. Physiol., 2000, 62, 919-926.
[6] Avdeef, A. Physicochemical profiling (solubility, permeability and
charge state). Curr. Top. Med. Chem., 2001, 1(4), 277-351.
[7] Di, L.; Kerns, E.H. Profiling drug-like properties in discovery
research. Curr. Opin. Chem. Biol., 2003, 7(3), 402-408.
[8] Seydel, J.K.; Velasco, M.A.; Coats, E.A.; Cordes, H.P.; Kunz, B.;
Wiese, M. The Importance of Drug-Membrane Interaction in Drug
Research-and-Development. Quantitative Structure-Activity Rela-
tionships, 1992, 11(2), 205-210.
[9] Seydel, J.K.; Coats, E.A.; Cordes, H.P.; Wiese, M. Drug Membrane
Interaction and the Importance for Drug Transport, Distribution,
Accumulation, Efficacy and Resistance. Arch. Pharm. (Weinheim),
1994, 327(10), 601-610.
[10] Seydel, J.K.; Wiese, M. Drug-Membrane Interactions: Analysis,
Drug Distribution, Modeling. Wiley-VCH Verlag: Weinheim,
2002.
[11] Escriba, P.V. Membrane-lipid therapy: a new approach in molecu-
lar medicine. Trends in Molecular Medicine, 2006, 12(1), 34-43.
[12] Przestalski, S.; Sarapuk, J.; Kleszczynska, H.; Gabrielska, J.;
Hladyszowski, J.; Trela, Z.; Kuczera, J. Influence of amphiphilic

compounds on membranes. Acta Biochim. Pol., 2000, 47(3), 627-
638.
[13] Gouaux, E.; White, S.H. Lipids lost, lipids regained. Curr. Opin.
Struct. Biol., 2001, 11(4), 393-396.
[14] Bittman, R. The 2003 ASBMB-Avanti Award in Lipids Address:
Applications of novel synthetic lipids to biological problems.
Chem. Phys. Lipids., 2004, 129(2), 111-131.
[15] Dowhan, W. Molecular basis for membrane phospholipid diversity:
why are there so many lipids? Annu. Rev. Biochem., 1997, 66, 199-
232.
[16] Alessenko, A.V.; Burlakova, E.B. Functional role of phospholipids
in the nuclear events. Bioelectrochemistry, 2002, 58(1), 13-21.
[17] Roberts, L.J. Introduction: lipids as regulators of cell function. Cell.
Mol. Life Sci., 2002, 59(5), 727-728.
[18] Lee, A.G. How lipids affect the activities of integral membrane
proteins. Biochim. Biophys. Acta, Biomembr., 2004, 1666(1-2), 62-
87.
[19] Rog, T.; Pasenkiewicz-Gierula, M.; Vattulainen, I.; Karttunen, M.
Ordering effects of cholesterol and its analogues. Biochim. Bio-
phys. Acta, 2009, 1788(1), 97-121.
[20] Hilgemann, D.W. Getting ready for the decade of the lipids. Annu.
Rev. Physiol., 2003, 65, 697-700.
[21] Wisniewska, A.; Draus, J.; Subczynski, W.K. Is a fluid-mosaic
model of biological membranes fully relevant? Studies on lipid or-
ganization in model and biological membranes. Cell. Mol. Biol.
Lett., 2003, 8(1), 147-159.
[22] Lommerse, P.H.; Spaink, H.P.; Schmidt, T. In vivo plasma mem-
brane organization: results of biophysical approaches. Biochim.
Biophys. Acta, 2004, 1664(2), 119-131.
[23] Brown, D.A.; London, E. Structure and function of sphingolipid-
and cholesterol-rich membrane rafts. J. Biol. Chem., 2000, 275(23),
17221-17224.
[24] Frankel, D.J.; Pfeiffer, J.R.; Surviladze, Z.; Johnson, A.E.; Oliver,
J.M.; Wilson, B.S.; Burns, A.R. Revealing the topography of cellu-
lar membrane domains by combined atomic force micros-
copy/fluorescence imaging. Biophys. J., 2006, 90(7), 2404-2413.
[25] Jacobson, K.; Mouritsen, O.G.; Anderson, R.G. Lipid rafts: at a
crossroad between cell biology and physics. Nat. Cell Biol., 2007,
9(1), 7-14.
[26] Mukherjee, S.; Maxfield, F.R. Membrane domains. Annu. Rev. Cell
Dev. Biol., 2004, 20, 839-866.
[27] Shaikh, S.R.; Edidin, M.A. Membranes are not just rafts. Chem.
Phys. Lipids., 2006, 144(1), 1-3.
[28] Thormann, E.; Simonsen, A.C.; Nielsen, L.K.; Mouritsen, O.G.
Ligand-receptor interactions and membrane structure investigated
by AFM and time-resolved fluorescence microscopy. J. Mol. Rec-
ognit., 2007, 20(6), 554-560.
[29] Fendler, J.H. Micro-Emulsions, Micelles, and Vesicles as Media
for Membrane Mimetic Photochemistry. J. Phys. Chem., 1980,
84(12), 1485-1491.
[30] Jelinek, R.; Kolusheva, S. Membrane interactions of host-defense
peptides studied in model systems. Curr. Protein Pept. Sci., 2005,
6(1), 103-114.
[31] Lasic, D.D. Liposomes - from Physics to Applications. Elsevier:
New York, 1993.
[32] Jesorka, A.; Orwar, O. Liposomes: Technologies and Analytical
Applications. Annu. Rev. Anal. Chem., 2008, 1, 801-832.
[33] Grancelli, A.; Morros, A.; Cabanas, M.E.; Domenech, O.; Merino,
S.; Vazquez, J.L.; Montero, M.T.; Vinas, M.; Hernandez-Borrell, J.
Interaction of 6-fluoroquinolones with dipalmitoylphosphatidylcho-
line monolayers and liposomes. Langmuir, 2002, 18(24), 9177-
9182.
[34] Rosa, S.M.L.J.; Antunes-Madeira, M.D.; Matos, M.J.; Jurado, A.S.;
Madeira, V.M.C. Lipid composition and dynamics of cell mem-
branes of Bacillus stearothermophilus adapted to amiodarone. Bio-
chim. Biophys. Acta Mol. Cell Biol. Lipids, 2000, 1487(2-3), 286-
295.
[35] Panicker, L.; Sugandhi, V.; Mishra, K.P. Interaction of keratolytic
drug, salicylic acid with dipalmitoyl phosphatidylethanolamine
vesicles. Phase Transitions, 2008, 81(4), 361-378.
[36] Cronier, F.; Patenaude, A.; Gaudreault, R.C.; Auger, M. Membrane
composition modulates the interaction between a new class of anti-
neoplastic agents deriving from aromatic 2-chloroethylureas and
lipid bilayers: a solid-state NMR study. Chem. Phys. Lipids., 2007,
146(2), 125-135.
[37] Castelli, F.; Sarpietro, M.G.; Ceruti, M.; Rocco, F.; Cattel, L. Char-
acterization of lipophilic gemcitabine prodrug - Liposomal mem-
brane interaction by differential scanning calorimetry. Mol.
Pharm., 2006, 3(6), 737-744.
[38] Matsuoka, S.; Ikeuchi, H.; Umegawa, Y.; Matsumori, N.; Murata,
M. Membrane interaction of amphotericin B as single-length as-
sembly examined by solid state NMR for uniformly C-13-enriched
agent. Bioorg. Med. Chem., 2006, 14(19), 6608-6614.
[39] Liu, Q.; Qu, Y.; Van Antwerpen, R.; Farrell, N. Mechanism of the
membrane interaction of polynuclear platinum anticancer agents.
Implications for cellular uptake. Biochemistry, 2006, 45(13), 4248-
4256.
[40] Panicker, L.; Mishra, K.P. Nuclear magnetic resonance and thermal
studies on the interaction between salicylic acid and model mem-
branes. Biophys. Chem., 2006, 120(1), 15-23.
[41] Castelli, F.; Raudino, A.; Fresta, M. A mechanistic study of the
permeation kinetics through biomembrane models: Gemcitabine-
phospholipid bilayer interaction. J. Colloid Interface Sci., 2005,
285(1), 110-117.
[42] Zoumpoulakis, P.; Daliani, I.; Zervou, M.; Kyrikou, I.; Siapi, E.;
Lamprinidis, G.; Mikros, E.; Mavromoustakos, T. Losartan's mo-
lecular basis of interaction with membranes and AT(1) receptor.
Chem. Phys. Lipids., 2003, 125(1), 13-25.
[43] Theodoropoulou, E.; Marsh, D. Interactions of angiotensin II non-
peptide AT(1) antagonist losartan with phospholipid membranes
studied by combined use of differential scanning calorimetry and
electron spin resonance spectroscopy. Biochim. Biophys. Acta,
Biomembr., 1999, 1461(1), 135-146.
[44] Gicquaud, C.; Auger, M.; Wong, P.T.T.; Poyet, P.; Boudreau, N.;
CGaudreault, R. Interaction of 4-tert-butyl-[3-(2-chloroethyl)
ureido] benzene with phosphatidylcholine bilayers: A differential
scanning calorimetry and infrared spectroscopy study. Arch. Bio-
chem. Biophys., 1996, 334(2), 193-199.
[45] Bauerle, H.D.; Seelig, J. Interaction of Charged and Uncharged
Calcium-Channel Antagonists with Phospholipid-Membranes -
Binding Equilibrium, Binding Enthalpy, and Membrane Location.
Biochemistry, 1991, 30(29), 7203-7211.
[46] Lucio, M.; Bringezu, F.; Reis, S.; Lima, J.L.F.C.; Brezesinski, G.
Binding of nonsteroidal anti-inflammatory drugs to DPPC: Struc-
ture and thermodynamic aspects. Langmuir, 2008, 24(8), 4132-
4139.
[47] Lucio, M.; Nunes, C.; Gaspar, D.; Golebska, K.; Wisniewski, M.;
Lima, J.L.F.C.; Brezesinski, G.; Reis, S. Effect of anti-
inflammatory drugs in phosphatidylcholine membranes: A fluores-
cence and calorimetric study. Chem. Phys. Lett., 2009, 471(4-6),
300-309.
[48] Lewis, R.N.; Tristram-Nagle, S.; Nagle, J.F.; McElhaney, R.N. The
thermotropic phase behavior of cationic lipids: calorimetric, infra-
red spectroscopic and X-ray diffraction studies of lipid bilayer
membranes composed of 1,2-di-O-myristoyl-3-N,N,N-
trimethylaminopropane (DM-TAP). Biochim. Biophys. Acta, 2001,
1510(1-2), 70-82.
[49] Dimova, R.; Aranda, S.; Bezlyepkina, N.; Nikolov, V.; Riske,
K.A.; Lipowsky, R. A practical guide to giant vesicles. Probing the
membrane nanoregime via optical microscopy. J. Phys. Condens.
Matter, 2006, 18(28), S1151-S1176.
[50] Matsuda, R.; Kaneko, N.; Horikawa, Y. Presence and comparison
of Ca2+ transport activity of annexins I, II, V, and VI in large
unilamellar vesicles. Biochem. Biophys. Res. Commun., 1997,
237(3), 499-503.
[51] Kahya, N.; Pecheur, E.I.; de Boeij, W.P.; Wiersma, D.A.; Hoekstra,
D. Reconstitution of membrane proteins into giant unilamellar
vesicles via peptide-induced fusion. Biophys. J., 2001, 81(3), 1464-
1474.
[52] Chakraborty, H.; Chakraborty, P.K.; Raha, S.; Mandal, P.C.;
Sarkar, M. Interaction of piroxicam with mitochondrial membrane
and cytochrome c. Biochim. Biophys. Acta Biomembr., 2007,
1768(5), 1138-1146.
[53] Rocha, S.; Lucio, M.; Pereira, M.C.; Reis, S.; Brezesinski, G. The
conformation of fusogenic B18 peptide in surfactant solutions. J.
Pept. Sci., 2008, 14(4), 436-441.

[54] Zhang, Y.H.; Dong, L.J.; Li, J.Z.; Chen, X.G. Studies on the inter-
action of gallic acid with human serum albumin in membrane mi-
metic environments. Talanta, 2008, 76(2), 246-253.
[55] Marezak, A.; Kowalczyk, A.; Wrzesien-Kus, A.; Robak, T.; Joz-
wiak, Z. Interaction of doxorubicin and idarubicin with red blood
cells from acute myeloid leukaemia patients. Cell Biol. Int., 2006,
30(2), 127-132.
[56] Berquand, A.; Fa, N.; Dufrene, Y.F.; Mingeot-Leclercq, M.P. In-
teraction of the macrolide antibiotic azithromycin with lipid bilay-
ers: Effect on membrane organization, fluidity, and permeability.
Pharm. Res., 2005, 22(3), 465-475.
[57] Brockman, H.L.; Momsen, M.M.; Knudtson, J.R.; Miller, S.T.;
Graff, G.; Yanni, J.M. Interactions of olopatadine and selected an-
tihistamines with model and natural membranes. Ocul. Immunol.
Inflamm., 2003, 11(4), 247-268.
[58] Lakowicz, J.R. Principles of Fluorescence Spectroscopy. 3rd ed.
ed. Springer: New York, 2006.
[59] Sulkowska, A. Interaction of drugs with bovine and human serum
albumin. J. Mol. Struct., 2002, 614(1-3), 227-232.
[60] Ferreira, H.; Lucio, M.; de Castro, B.; Gameiro, P.; Lima, J.L.F.C.;
Reis, S. Partition and location of nimesulide in EPC liposomes: a
spectrophotometric and fluorescence study. Anal. Bioanal. Chem.,
2003, 377(2), 293-298.
[61] Ferreira, H.; Lucio, M.; Lima, J.L.F.C.; Matos, C.; Reis, S. Effects
of diclofenac on EPC liposome membrane properties. Anal.
Bioanal. Chem., 2005, 382(5), 1256-1264.
[62] Ferreira, H.; Lucio, M.; Lima, J.L.F.C.; Matos, C.; Reis, S. Interac-
tion of clonixin with EPC liposomes used as membrane models. J.
Pharm. Sci., 2005, 94(6), 1277-1287.
[63] Lucio, M.; Ferreira, H.; Lima, J.L.; Reis, S. Use of liposomes to
evaluate the role of membrane interactions on antioxidant activity.
Anal. Chim. Acta, 2007, 597(1), 163-170.
[64] Lucio, M.; Ferreira, H.; Lima, J.L.F.C.; Matos, C.; de Castro, B.;
Reis, S. Influence of some anti-inflammatory drugs in membrane
fluidity studied by fluorescence anisotropy measurements. Phys.
Chem. Chem. Phys., 2004, 6(7), 1493-1498.
[65] Santos, F.; Teixeira, L.; Lucio, M.; Ferreira, H.; Gaspar, D.; Lima,
J.L.F.C.; Reis, S. Interactions of sulindac and its metabolites with
phospholipid membranes: An explanation for the peroxidation pro-
tective effect of the bioactive metabolite. Free Radical Res., 2008,
42(7), 639-650.
[66] Brockman, H. Lipid monolayers: why use half a membrane to
characterize protein-membrane interactions? Curr. Opin. Struct.
Biol., 1999, 9(4), 438-443.
[67] Greenhall, M.H.; Yarwood, J.; Brown, R.; Swart, R.M. Spectro-
scopic studies of model biological membranes in vesicles and
Langmuir-Blodgett films. Langmuir, 1998, 14(10), 2619-2626.
[68] Agasosler, A.V.; Tungodden, L.M.; Cejka, D.; Bakstad, E.; Sydnes,
L.K.; Holmsen, H. Chorpromazine-induced increase in dipalmi-
toylphosphatidylserine surface area in monolayers at room tem-
perature. Biochem. Pharmacol., 2001, 61(7), 817-825.
[69] Brezesinski, G.; Mohwald, H. Langmuir monolayers to study inter-
actions at model membrane surfaces. Adv. Colloid Interface Sci.,
2003, 100-102, 563-584.
[70] Brockman, H.; Graff, G.; Spellman, J.; Yanni, J. A comparison of
the effects of olopatadine and ketotifen on model membranes. Acta
Ophthalmol. Scand., 2000, 78, 10-15.
[71] Caetano, W.; Ferreira, M.; Tabak, M.; Sanchez, M.I.M.; Oliveira,
O.N.; Kruger, P.; Schalke, M.; Losche, M. Cooperativity of phos-
pholipid reorganization upon interaction of dipyridamole with sur-
face monolayers on water. Biophys. Chem., 2001, 91(1), 21-35.
[72] da Silva, A.M.G.; Romao, R.I.S. Mixed monolayers involving
DPPC, DODAB and oleic acid and their interaction with nicotinic
acid at the air-water interface. Chem. Phys. Lipids., 2005, 137(1-2),
62-76.
[73] Jutila, A.; Soderlund, T.; Pakkanen, A.L.; Huttunen, M.; Kinnunen,
P.K. Comparison of the effects of clozapine, chlorpromazine, and
haloperidol on membrane lateral heterogeneity. Chem. Phys. Lip-
ids., 2001, 112(2), 151-163.
[74] Varnier Agasoster, A.; Holmsen, H. Chlorpromazine associates
with phosphatidylserines to cause an increase in the lipid's own in-
terfacial molecular area--role of the fatty acyl composition. Bio-
phys. Chem., 2001, 91(1), 37-47.
[75] Hidalgo, A.A.; Caetano, W.; Tabak, M.; Oliveira, O.N. Interaction
of two phenothiazine derivatives with phospholipid monolayers.
Biophys. Chem., 2004, 109(1), 85-104.
[76] Turner, Y.T.; Roberts, C.J.; Davies, M.C. Scanning probe micros-
copy in the field of drug delivery. Adv. Drug Res., 2007, 59(14),
1453-1473.
[77] Chakraborty, H.; Roy, S.; Sarkar, M. Interaction of oxicam
NSAIDs with DMPC vesicles: differential partitioning of drugs.
Chem. Phys. Lipids, 2005, 138(1-2), 20-28.
[78] Chakraborty, H.; Sarkar, M. Optical spectroscopic and TEM stud-
ies of catanionic micelles of CTAB/SDS and their interaction with
a NSAID. Langmuir, 2004, 20(9), 3551-3558.
[79] Clausell, A.; Busquets, M.A.; Pujol, M.; Alsina, A.; Cajal, Y. Po-
lymyxin B-lipid interactions in Langmuir-Blodgett monolayers of
Escherichia coli lipids: a thermodynamic and atomic force micros-
copy study. Biopolymers, 2004, 75(6), 480-490.
[80] Liu, J.; Conboy, J.C. Structure of a gel phase lipid bilayer prepared
by the Langmuir-Blodgett/Langmuir-Schaefer method character-
ized by sum-frequency vibrational spectroscopy. Langmuir, 2005,
21(20), 9091-9097.
[81] Nussio, M.R.; Sykes, M.J.; Miners, J.O.; Shapter, J.G. Kinetics
Membrane Disruption Due to Drug Interactions of Chlorpromazine
Hydrochloride. Langmuir, 2009, 25(2), 1086-1090.
[82] Tatulian, S.A. Attenuated total reflection Fourier transform infrared
spectroscopy: a method of choice for studying membrane proteins
and lipids. Biochemistry, 2003, 42(41), 11898-11907.
[83] Seddon, A.M.; Casey, D.; Law, R.V.; Gee, A.; Templer, R.H.; Ces,
O. Drug interactions with lipid membranes. Chem. Soc. Rev., 2009,
38(9), 2509-2519.
[84] Schreier, S.; Malheiros, S.V.P.; de Paula, E. Surface active drugs:
self-association and interaction with membranes and surfactants.
Physicochemical and biological aspects. Biochim. Biophys. Acta,
Biomembr., 2000, 1508(1-2), 210-234.
[85] Carrozzino, J.M.; Khaledi, M.G. Interaction of basic drugs with
lipid bilayers using liposome electrokinetic chromatography.
Pharm. Res., 2004, 21(12), 2327-2335.
[86] Romanowski, M.; Zu, X.Y.; Ramaswami, V.; Misicka, A.;
Lipkowski, A.W.; Hruby, V.J.; OBrien, D.F. Interaction of a highly
potent dimeric enkephalin analog, biphalin, with model mem-
branes. Biochim. Biophys. Acta, Biomembr., 1997, 1329(2), 245-
258.
[87] Hillgren, K.M.; Kato, A.; Borchardt, R.T. In vitro systems for
studying intestinal drug absorption. Med. Res. Rev., 1995, 15(2),
83-109.
[88] Kansy, M.; Fischer, K.; Kratzat, F.; Senner, B.; Wagner, B.; Parilla,
I. High-throughput artificial membrane permeability studies in
early lead discovery and development. Willey-VCH Verlag
Helvetica Chimica Acta: Weinheim and Zürich, Germany, 2001.
[89] Sugano, K.; John, B.T.; David, J.T. Comprehensive Medicinal
Chemistry. Elsevier: Oxford, 2007.
[90] Avdeef, A.; Bendels, S.; Di, L.; Faller, B.; Kansy, M.; Sugano, K.;
Yamauchi, Y. PAMPA--critical factors for better predictions of ab-
sorption. J. Pharm. Sci., 2007, 96(11), 2893-2909.
[91] Osterberg, T.; Svensson, M.; Lundahl, P. Chromatographic reten-
tion of drug molecules on immobilised liposomes prepared from
egg phospholipids and from chemically pure phospholipids. Eur. J.
Pharm. Sci., 2001, 12(4), 427-439.
[92] Barbato, F.; di Martino, G.; Grumetto, L.; La Rotonda, M.I. Predic-
tion of drug-membrane interactions by IAM-HPLC: effects of dif-
ferent phospholipid stationary phases on the partition of bases. Eur.
J. Pharm. Sci., 2004, 22(4), 261-269.
[93] Cushion, M.T.; Walzer, P.D. Preclinical drug discovery for new
anti-pneumocystis compounds. Curr. Med. Chem., 2009, 16(20),
2514-2530.
[94] Ford, J.M.; Prozialeck, W.C.; Hait, W.N. Structural features deter-
mining activity of phenothiazines and related drugs for inhibition
of cell growth and reversal of multidrug resistance. Mol. Pharma-
col., 1989, 35(1), 105-115.
[95] Ford, J.M.; Hait, W.N. Pharmacology of drugs that alter multidrug
resistance in cancer. Pharmacol. Rev., 1990, 42(3), 155-199.
[96] Ford, J.M.; Bruggemann, E.P.; Pastan, I.; Gottesman, M.M.; Hait,
W.N. Cellular and biochemical characterization of thioxanthenes
for reversal of multidrug resistance in human and murine cell lines.
Cancer Res., 1990, 50(6), 1748-1756.

[97] Foldvari, M.; Moreland, A.; Smith, T. Topical liposomal tetracaine
for pain relief of intralesional interferon injections in the treatment
of condylomata acuminata. Int. J. Dermatol., 1992, 31(12), 894-
895.
[98] Mamelli, L.; Petit, S.; Chevalier, J.; Giglione, C.; Lieutaud, A.;
Meinnel, T.; Artaud, I.; Pages, J.M. New antibiotic molecules: by-
passing the membrane barrier of gram negative bacteria increases
the activity of peptide deformylase inhibitors. PLoS ONE, 2009,
4(7), e6443.
[99] Shah, J.C.; Sadhale, Y.; Chilukuri, D.M. Cubic phase gels as drug
delivery systems. Adv. Drug Deliv. Rev., 2001, 47(2-3), 229-250.
[100] Ulrich, A.S. Biophysical aspects of using liposomes as delivery
vehicles. Biosci. Rep., 2002, 22(2), 129-150.
[101] Bouwstra, J.A.; De Graaff, A.; Groenink, W.; Honeywell, L. Elas-
tic vesicles: interaction with human skin and drug transport. Cell.
Mol. Biol. Lett., 2002, 7(2), 222-223.
[102] Bouwstra, J.A.; Honeywell-Nguyen, P.L. Skin structure and mode
of action of vesicles. Adv. Drug Deliv.. Rev., 2002, 54 Suppl 1,
S41-55.
[103] Yamane, M.A.; Williams, A.C.; Barry, B.W. Terpene penetration
enhancers in propylene glycol/water co-solvent systems: effective-
ness and mechanism of action. J. Pharm. Pharmacol., 1995,
47(12A), 978-989.
[104] Gao, S.; Singh, J. In vitro percutaneous absorption enhancement of
a lipophilic drug tamoxifen by terpenes. J. Control Release, 1998,
51(2-3), 193-199.
[105] El Maghraby, G.M.M.; Williams, A.C.; Barry, B.W. Drug interac-
tion and location in liposomes: correlation with polar surface areas.
Int. J. Pharm., 2005, 292(1-2), 179-185.
[106] Sahoo, S.K.; Panyam, J.; Prabha, S.; Labhasetwar, V. Residual
polyvinyl alcohol associated with poly (D,L-lactide-co-glycolide)
nanoparticles affects their physical properties and cellular uptake.
J. Control Release, 2002, 82(1), 105-114.
[107] Gref, R.; Couvreur, P.; Barratt, G.; Mysiakine, E. Surface-
engineered nanoparticles for multiple ligand coupling. Biomateri-
als, 2003, 24(24), 4529-4537.
[108] Zilversmit, D.B.; Boyd, G.A.; Brucer, M. The effect of particle size
on blood clearance and tissue distribution of radioactive gold col-
loids. J. Lab. Clin. Med., 1952, 40(2), 255-260.
[109] Hong, S.P.; Leroueil, P.R.; Janus, E.K.; Peters, J.L.; Kober, M.M.;
Islam, M.T.; Orr, B.G.; Baker, J.R.; Holl, M.M.B. Interaction of
polycationic polymers with supported lipid bilayers and cells:
Nanoscale hole formation and enhanced membrane permeability.
Bioconjug. Chem., 2006, 17(3), 728-734.
[110] Leroueil, P.R.; Hong, S.; Mecke, A.; Baker, J.R., Jr.; Orr, B.G.;
Banaszak Holl, M.M. Nanoparticle interaction with biological
membranes: does nanotechnology present a Janus face? Acc. Chem.
Res., 2007, 40(5), 335-342.
[111] Mecke, A.; Majoros, I.J.; Patri, A.K.; Baker, J.R., Jr.; Holl, M.M.;
Orr, B.G. Lipid bilayer disruption by polycationic polymers: the
roles of size and chemical functional group. Langmuir, 2005,
21(23), 10348-10354.
[112] Bosch, I.; Croop, J. P-glycoprotein multidrug resistance and cancer.
Biochim. Biophys. Acta, 1996, 1288(2), F37-54.
[113] Gottesman, M.M.; Pastan, I. Biochemistry of multidrug resistance
mediated by the multidrug transporter. Annu. Rev. Biochem., 1993,
62, 385-427.
[114] Omote, H.; Al-Shawi, M.K. Interaction of transported drugs with
the lipid bilayer and beta-glycoprotein through a solvation ex-
change mechanism. Biophys. J., 2006, 90(11), 4046-4059.
[115] Ambudkar, S.V.; Kimchi-Sarfaty, C.; Sauna, Z.E.; Gottesman,
M.M. P-glycoprotein: from genomics to mechanism. Oncogene,
2003, 22(47), 7468-7485.
[116] Borst, P.; Elferink, R.O. Mammalian ABC transporters in health
and disease. Annu. Rev. Biochem., 2002, 71, 537-592.
[117] Leslie, E.M.; Deeley, R.G.; Cole, S.P. Multidrug resistance pro-
teins: role of P-glycoprotein, MRP1, MRP2, and BCRP (ABCG2)
in tissue defense. Toxicol. Appl. Pharmacol., 2005, 204(3), 216-
237.
[118] Lu, P.; Liu, R.; Sharom, F.J. Drug transport by reconstituted P-
glycoprotein in proteoliposomes. Effect of substrates and modula-
tors, and dependence on bilayer phase state. Eur. J. Biochem.,
2001, 268(6), 1687-1697.
[119] Omote, H.; Al-Shawi, M.K. A novel electron paramagnetic reso-
nance approach to determine the mechanism of drug transport by P-
glycoprotein. J. Biol. Chem., 2002, 277(47), 45688-45694.
[120] Romsicki, Y.; Sharom, F.J. Interaction of P-glycoprotein with
defined phospholipid bilayers: A differential scanning calorimetric
study. Biochemistry, 1997, 36(32), 9807-9815.
[121] Romsicki, Y.; Sharom, F.J. The membrane lipid environment
modulates drug interactions with the P-glycoprotein multidrug
transporter. Biochemistry, 1999, 38(21), 6887-6896.
[122] Drori, S.; Eytan, G.D.; Assaraf, Y.G. Potentiation of Anticancer-
Drug Cytotoxicity by Multidrug-Resistance Chemosensitizers In-
volves Alterations in Membrane Fluidity Leading to Increased
Membrane-Permeability. Eur. J. Biochem., 1995, 228(3), 1020-
1029.
[123] Michalak, K.; Wesolowska, O.; Motohashi, N.; Molnar, J.; Hen-
drich, A.B. Interactions of phenothiazines with lipid bilayer and
their role in multidrug resistance reversal. Curr. Drug Targets,
2006, 7(9), 1095-1105.
[124] Pajeva, I.K.; Wiese, M.; Cordes, H.P.; Seydel, J.K. Membrane
interactions of some catamphiphilic drugs and relation to their
multidrug-resistance-reversing ability. J. Cancer Res. Clin. Oncol.,
1996, 122(1), 27-40.
[125] Vogler, O.; Casas, J.; Capo, D.; Nagy, T.; Borchert, G.; Martorell,
G.; Escriba, P.V. The Gbetagamma dimer drives the interaction of
heterotrimeric Gi proteins with nonlamellar membrane structures.
J. Biol. Chem., 2004, 279(35), 36540-36545.
[126] Bergethon, P.R.; Simons, E.R. Biophysical Chemistry - Molecules
to Membranes. Springer-Verlag: New York, 1990.
[127] Mustonen, P.; Kinnunen, P.K. Activation of phospholipase A2 by
adriamycin in vitro. Role of drug-lipid interactions. J. Biol. Chem.,
1991, 266(10), 6302-6307.
[128] Pande, A.H.; Qin, S.; Tatulian, S.A. Membrane fluidity is a key
modulator of membrane binding, insertion, and activity of 5-
lipoxygenase. Biophys. J., 2005, 88(6), 4084-4094.
[129] Nicolay, K.; de Kruijff, B. Effects of adriamycin on respiratory
chain activities in mitochondria from rat liver, rat heart and bovine
heart. Evidence for a preferential inhibition of complex III and IV.
Biochim. Biophys. Acta, 1987, 892(3), 320-330.
[130] Mingeot-Leclercq, M.P.; Tulkens, P.M. Aminoglycosides: nephro-
toxicity. Antimicrob. Agents Chemother., 1999, 43(5), 1003-1012.
[131] Kumar, R.; Holian, O.; Cook, B.; Roshani, P. Inhibition of rat brain
protein kinase C by lipid soluble psychotropics. Neurochem. Res.,
1997, 22(1), 1-10.
[132] Theumer, M.G.; Clop, E.M.; Rubinstein, H.R.; Perillo, M.A. The
lipid-mediated hypothesis of fumonisin B1 toxicodynamics tested
in model membranes. Colloids Surf., B, 2008, 64(1), 22-33.
[133] Epand, R.M. Biophysical studies of lipopeptide-membrane interac-
tions. Biopolymers, 1997, 43(1), 15-24.
[134] Wenk, M.R. The emerging field of lipidomics. Nat. Rev. Drug
Discov., 2005, 4(7), 594-610.
[135] Watson, A.D. Thematic review series: systems biology approaches
to metabolic and cardiovascular disorders. Lipidomics: a global ap-
proach to lipid analysis in biological systems. J. Lipid Res., 2006,
47(10), 2101-2111.
[136] Han, X. Neurolipidomics: challenges and developments. Front.
Biosci., 2007, 12, 2601-2615.
[137] Escriba, P.V.; Ferrermontiel, A.V.; Ferragut, J.A.; Gonzalezros,
J.M. Role of Membrane-Lipids in the Interaction of Daunomycin
with Plasma-Membranes from Tumor-Cells - Implications in Drug-
Resistance Phenomena. Biochemistry, 1990, 29(31), 7275-7282.
[138] Escriba, P.V.; Sastre, M.; Garciasevilla, J.A. Disruption of Cellular
Signaling Pathways by Daunomycin through Destabilization of
Nonlamellar Membrane Structures. Proc. Natl. Acad. Sci. U. S. A.,
1995, 92(16), 7595-7599.
[139] Garcia, M.L.; Egea, M.A.; Valero, J.; Valls, O.; Alsina, M.A. Inter-
action of flurbiprofen sodium with cornea model monolayers at the
air-water interface. Thin Solid Films, 1997, 301(1-2), 169-174.
[140] Sousa, C.; Nunes, C.; Lucio, M.; Ferreira, H.; Lima, J.L.F.C.;
Tavares, J.; Cordeiro-Da-Silva, A.; Reis, S. Effect of nonsteroidal
anti-inflammatory drugs on the cellular membrane fluidity. J.
Pharm. Sci., 2008, 97(8), 3195-3206.
[141] Cavalcanti, L.P.; Konovalov, O.; Torriani, I.L. Lipid model mem-
branes for drug interaction study. Eur. Biophys. J. Biophys., 2006,
35(5), 431-438.

[142] Bernsdorff, C.; Reszka, R.; Winter, R. Interaction of the anticancer
agent Taxol (TM) (paclitaxel) with phospholipid bilayers. J. Bio-
med. Mater. Res., 1999, 46(2), 141-149.
[143] Baginski, M.; Borowski, E. Distribution of electrostatic potential
around amphotericin B and its membrane targets. J. Mol. Struct. -
Theochem., 1997, 389(1-2), 139-146.
[144] Baginski, M.; Sternal, K.; Czub, J.; Borowski, E. Molecular model-
ling of membrane activity of amphotericin B, a polyene macrolide
antifungal antibiotic. Acta Biochim. Pol., 2005, 52(3), 655-658.
[145] Barwicz, J.; Tancrede, P. The effect of aggregation state of ampho-
tericin-B on its interactions with cholesterol- or ergosterol-
containing phosphatidylcholine monolayers. Chem. Phys. Lipids.,
1997, 85(2), 145-155.
[146] Cohen, B.E. A sequential mechanism for the formation of aqueous
channels by amphotericin B in liposomes. The effect of sterols and
phospholipid composition. Biochim. Biophys. Acta, 1992, 1108(1),
49-58.
[147] Hac-Wydro, K.; Dynarowicz-Latka, P.; Grzybowska, J.; Borowski,
E. Interactions of Amphotericin B derivative of low toxicity with
biological membrane components - the Langmuir monolayer ap-
proach. Biophys. Chem., 2005, 116(1), 77-88.
[148] Matsuoka, S.; Murata, M. Membrane permeabilizing activity of
amphotericin B is affected by chain length of phosphatidylcholine
added as minor constituent. Biochim. Biophys. Acta Biomembr.,
2003, 1617(1-2), 109-115.
[149] Merino, S.; Domenech, O.; Diez, I.; Sanz, F.; Vinas, M.; Montero,
M.T.; Hernandez-Borrell, J. Effects of ciprofloxacin on Escherichia
coli lipid bilayers: An atomic force microscopy study. Langmuir,
2003, 19(17), 6922-6927.
[150] Vazquez, J.L.; Montero, M.T.; Merino, S.; Domenech, O.; Ber-
langa, M.; Vinas, M.; Hernandez-Borrell, J. Location and nature of
the surface membrane binding site of ciprofloxacin: A fluorescence
study. Langmuir, 2001, 17(4), 1009-1014.
[151] Berquand, A.; Mingeot-Leclercq, M.P.; Dufrene, Y.F. Real-time
imaging of drug-membrane interactions by atomic force micros-
copy. Biochim. Biophys. Acta, Biomembr., 2004, 1664(2), 198-205.
[152] Fa, N.; Lins, L.; Courtoy, P.J.; Dufrene, Y.; Van Der Smissen, P.;
Brasseur, R.; Tyteca, D.; Mingeot-Leclercq, M.P. Decrease of elas-
tic moduli of DOPC bilayers induced by a macrolide antibiotic,
azithromycin. Biochim. Biophys. Acta Biomembr., 2007, 1768(7),
1830-1838.
[153] Fa, N.; Ronkart, S.; Schanck, A.; Deleu, M.; Gaigneaux, A.; Goon-
naghtigh, E.; Mingeot-Leclercq, M.P. Effect of the antibiotic
azithromycin on thermotropic behavior of DOPC or DPPC bilay-
ers. Chem. Phys. Lipids, 2006, 144(1), 108-116.
[154] Molitoris, B.A.; Meyer, C.; Dahl, R.; Geerdes, A. Mechanism of
ischemia-enhanced aminoglycoside binding and uptake by proxi-
mal tubule cells. Am. J. Physiol., 1993, 264(5 Pt 2), F907-916.
[155] Zhang, L.X.; Liu, J.Y.; Wang, E.K. A new method for studying the
interaction between chlorpromazine and phospholipid bilayer. Bio-
chem. Biophys. Res. Commun., 2008, 373(2), 202-205.
[156] Cheng, H.Y.; Randall, C.S.; Holl, W.W.; Constantinides, P.P.; Yue,
T.L.; Feuerstein, G.Z. Carvedilol-liposome interaction: Evidence
for strong association with the hydrophobic region of the lipid bi-
layers. Biochim. Biophys. Acta, Biomembr., 1996, 1284(1), 20-28.
[157] Saveyn, P.; Cocquyt, J.; De Cuyper, M.; Van der Meeren, P.
Evaluation of the interaction of propranolol with 1,2-dimyristoyl-
sn-glycero-3-phosphocholine (DMPC) liposomes: The Langmuir
model. Langmuir, 2008, 24(12), 6007-6012.
[158] Cocquyt, J.; Saveyn, P.; Van der Meeren, P.; De Cuyper, M.
Evaluation of the interaction of propranolol with 1,2-dimyristoyl-
sn-glycero-3-phosphocholine (DMPC) liposomes: the partitioning
model. Langmuir, 2007, 23(4), 1959-1964.
[159] Krill, S.L.; Lau, K.Y.; Plachy, W.Z.; Rehfeld, S.J. Penetration of
dimyristoylphosphatidylcholine monolayers and bilayers by model
beta-blocker agents of varying lipophilicity. J. Pharm. Sci., 1998,
87(6), 751-756.
[160] Butler, M.B.; Sboros, V.; Moran, C.M.; Ross, J.; Koutsos, V.;
McDicken, W.N.; Pye, S. Development of a novel experimental
set-up to allow investigation of the ultrasonic backscatter from mi-
crobubble contrast agents attached to surfaces. IEEE Ultrasonics
Symposium, Proceed., 2006, 1-5, 1362-1364.
[161] Meier, M.; Blatter, X.L.; Seelig, A.; Seelig, J. Interaction of vera-
pamil with lipid membranes and P-glycoprotein: Connecting ther-
modynamics and membrane structure with functional activity. Bio-
phys. J., 2006, 91(8), 2943-2955.
[162] Borges, C.P.F.; Borissevitch, I.E.; Tabak, M. Charge-Dependent
and Ph-Dependent Binding-Sites of Dipyridamole in Ionic Micelles
- a Fluorescence Study. J. Lumin., 1995, 65(2), 105-112.
[163] Suwalsky, M.; Mennickent, S.; Villena, F.; Sotomayor, C.P. Phos-
pholipids bilayers as molecular models for drug-membrane interac-
tions. The case of the antiepileptics phenytoin and carbamazepine.
Macromol. Symp., 2008, 269, 119-127.
[164] Kessel, A.; Musafia, B.; Ben-Tal, N. Continuum solvent model
studies of the interactions of an anticonvulsant drug with a lipid bi-
layer. Biophys. J., 2001, 80(6), 2536-2545.
[165] Rakotomanga, M.; Saint-Pierre-Chazalet, M.; Loiseau, P.M. Al-
teration of fatty acid and sterol metabolism in miltefosine-resistant
Leishmania donovani promastigotes and consequences for drug-
membrane interactions. Antimicrob. Agents Chemother., 2005,
49(7), 2677-2686.
[166] Porcar, I.; Codoner, A.; Gomez, C.M.; Abad, C.; Campos, A. Inter-
action of quinine with model lipid membranes of different compo-
sitions. J. Pharm. Sci., 2003, 92(1), 45-57.
[167] Pedros, J.; Porcar, I.; Gomez, C.M.; Campos, A.; Abad, C. Interac-
tion of quinine with negatively charged lipid vesicles studied by
fluorescence spectroscopy - Influence of the pH. Spectrochim. Acta
A, 1997, 53(3), 421-431.
[168] de Paula, E.; Schreier, S. Molecular and physicochemical aspects
of local anesthetic-membrane interaction. Braz. J. Med. Biol. Res.,
1996, 29(7), 877-894.
[169] Malheiros, S.V.P.; Pinto, L.M.A.; Gottardo, L.; Yokaichiya, D.K.;
Fraceto, L.F.; Meirelles, N.C.; de Paula, E. A new look at the
hemolytic effect of local anesthetics, considering their real mem-
brane/water partitioning at pH 7.4. Biophys. Chem., 2004, 110(3),
213-221.
[170] Yun, I.; Cho, E.S.; Jang, H.O.; Kim, U.K.; Choi, C.H.; Chung, I.K.;
Kim, I.S.; Wood, W.G. Amphiphilic effects of local anesthetics on
rotational mobility in neuronal and model membranes. Biochim.
Biophys. Acta, 2002, 1564(1), 123-132.
[171] Zhang, J.; Hadlock, T.; Gent, A.; Strichartz, G.R. Tetracaine-
membrane interactions: effects of lipid composition and phase on
drug partitioning, location, and ionization. Biophys. J., 2007,
92(11), 3988-4001.
[172] Urban, B.W.; Bleckwenn, M.; Barann, M. Interactions of anesthet-
ics with their targets: non-specific, specific or both? Pharmacol.
Ther., 2006, 111(3), 729-770.
[173] Jorgensen, K.; Ipsen, J.H.; Mouritsen, O.G.; Bennett, D.; Zucker-
mann, M.J. A general-model for the interaction of foreign mole-
cules with lipid-membranes - drugs and anesthetics. Biochim. Bio-
phys. Acta, 1991, 1062(2), 227-238.
[174] Jorgensen, K.; Ipsen, J.H.; Mouritsen, O.G.; Bennett, D.; Zucker-
mann, M.J. The effects of density fluctuations on the partitioning of
foreign molecules into lipid bilayers: application to anaesthetics
and insecticides. Biochim. Biophys. Acta, 1991, 1067(2), 241-253.
[175] Jorgensen, K.; Ipsen, J.H.; Mouritsen, O.G.; Zuckermann, M.J. The
effect of anaesthetics on the dynamic heterogeneity of lipid mem-
branes. Chem. Phys. Lipids., 1993, 65(3), 205-216.
Received: December 20, 2009 Revised: March 19, 2010 Accepted: March 21, 2010

Copyright of Current Medicinal Chemistry is the property of Bentham Science Publishers Ltd. and its content
may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express
written permission. However, users may print, download, or email articles for individual use.
View publication stats
View publication stats

Drug-MembraneInteractionsSignificanceforMedicinalChemistry.pdf

Recommended

Recommended

More Related Content

Similar to Drug-MembraneInteractionsSignificanceforMedicinalChemistry.pdf

Similar to Drug-MembraneInteractionsSignificanceforMedicinalChemistry.pdf (20)

Recently uploaded

Recently uploaded (20)

Drug-MembraneInteractionsSignificanceforMedicinalChemistry.pdf