Introduction to Nanoparticles, How Nanoparticles achieve targeted drug delivery, Chitosan Nanoparticles, Synthesis, Modifications, Biological Properties, Formulation, Drug release mechanism, Clinical aspects

2. INTRODUCTION TO NANOPARTICLES
Targeting Mechanisms, Types

3. Introduction to Nanomedicine
• It is the medical application of nanotechnology.
• Nanomedicine ranges from the medical applications of
nanomaterials in advanced drug delivery systems, new
therapies, and in contrast imaging.
• It is widely studied in cancer treatment. In addition,
research is also focused on neurodegenerative, infectious,
autoimmune, etc. diseases.
• The major goal of nanoparticles is to achieve the site-
specific action of the drug at the therapeutically optimal
rate and dose regimen.

4. TARGETED DRUG DELIVERY
Mechanisms of Action

5. Targeted delivery
• Targeted drug delivery or smart drug delivery is a method
that delivers the drug only to targeted areas within the
body.
• The delivery of the drug to the target tissue can be
achieved primarily in two ways:
1. Passive targeting
2. Active targeting

6. Mechanism of Nanoparticle drug delivery
Passive and Active targeting

7. Passive targeting
• This is based on the accumulation of drug at areas around the site of
interest, such as in case of tumor tissues. This is called Enhanced
Permeability Retention (EPR) effect.
• Such a types of targeting occurs with almost all types of drug delivery
carriers.
• Passive targeting is based on:
a. Leaky Vasculature
b. Tumor Environment
c. Local Application

8. Leaky Vasculature
• Most polymer nanoparticles display the enhanced
permeability and retention effect.
• It is based on two factors:
a. Capillary endothelium in malignant tissue is more
disorderly and thus more permeable.
b. Lack of tumor lymphatic drainage results in drug
accumulation.
• So, concentrations of polymer-drug conjugates in tumor
can reach 10-100 times higher than that resulting from the
administration of the free drug.

9. Tumor Microenvironment
• The drug is conjugated to a tumor-specific molecule and
the tumor environment converts it to active drug, so-called
tumor-activated prodrug therapy.
• For example, paclitaxel is modified with an Matrix
metalloproteinases-cleavable linker. This functionalized
nanoparticle was effectively delivered and paclitaxel was
released into the tumor site owing to high levels of MMPs
in TME.

10. Local Drug Application
• Direct local application allows the drug to be given directly
to tumor tissue, avoiding systemic circulation.
• Tacrolimus loaded poly(lactic-co-glycolic acid)
nanoparticles administered orally for colitis. Results
showed successful release of both drug and nanoparticle
into the tumor environment. The drug penetration into
inflamed tissue was 3-fold higher compared with healthy
tissue when using nanoparticle as drug carrier.

11. Active Targeting
• Active targeting is usually achieved by conjugating the nanoparticle to
a targeting moiety, thereby allowing preferential accumulation of the
drug in the tumor tissues or cells.
• This approach is used to direct nanoparticles to cell surface
carbohydrates, receptors, and antigens.

12. Carbohydrate-Directed Targeting
• Cancer cells have been found to differentially express
lectins on their surface compared to healthy cells, and the
affinity of carbohydrates towards these lectins can be
exploited to target these cells.
• It can be used by producing nanoparticles containing
carbohydrate directed to certain lectins (direct lectin
targeting), or incorporating lectins directed to cell surface
carbohydrates (reverse lectin targeting).
• A lectin Jacalin has been employed to target Thomsen–
Friedenreich antigen (T-antigen). The T-antigen is
expressed in 90% of cancers and is usually cryptic on
healthy cells.

13. Receptor Targeting
• The overexpression of receptors or antigens in human
cancers lends itself to efficient uptake via receptor-
mediated endocytosis.
• Epidermal growth factor has been used to target AuNPs
towards epidermal growth factor receptor (EGFR)
overexpressing in breast cancer.

14. Antibody Targeting
• Antibody target antigens are typically highly expressed on
the surface of cancer cells compared to normal cells.
• An antibody-drug conjugate will combine with target
antigen with the delivery of a highly potent cytotoxic
agent.
• Brentuximab vedotin represents one such ADC. Its target
antigen, CD30, highly expressed on the surface of
malignant cells.

15. Components & Characteristics
• It has three essential molecules.
• Polymer, to which drug can be conjugated. It must be
inert, free of leachable impurities and biodegradable.
• Ligand/antibody, to which polymers are linked, which in
turn, bind with receptor. It should be easily incorporated
into a nanoparticle, have specificity, has the ability to
cause endocytosis, and biodegradable.
• Receptors/antigens, to which NP binds, should be
abundant on tumor tissue, upregulation should occur
following exposure, the rate of endocytosis should be
high, the receptors or antigens are recycled back after
endocytosis.

16. Advantages
1. Particle size and surface characteristics can be
manipulated to achieve passive and active drug targeting.
2. Site specific release by attaching ligands or use of
magnetic field. It reduces side effects.
3. Controlled release and particle degradation can be
modulated by the choice of matrix constituents.
4. Drugs can be incorporated without any chemical reaction.
5. The system can be used for various routes of
administration including oral, nasal, parenteral, intra-
ocular etc.

17. Disadvantages
• Their small size and large surface area can lead to
aggregation.
• Small particles size and large surface area readily result
in limited drug loading and burst release.

18. CLASSIFICATION
Organic & Inorganic NPs

19. Types
They are broadly classified into inorganic and organic NPs.

20. CHITOSAN NANOPARTICLES
Synthesis, Properties, Clinical Aspects

21. CHITOSAN NANOPARTICLES
Preparation, Characteristics, Application

22. Chitosan
• Chitosan is a modified bio-polymer. It consists of
alternating units of ß-1, 4 linked N-acetyl glucos-amine
and glucosamine units.
• In 1859, Prof. C. Rouget found that alkali treatment of
chitin yielded a substance that unlike chitin can be
dissolved in acids.
• In 1894, Hoppe Seiler called this deacetylated chitin
‘Chitosan.’
• It has a pKa of 6.5.
• It is insoluble in water but soluble in acidic solutions.
• It is protonated and poly-cationic in nature.

23. Chitosan
Chemical Structure

24. Synthesis
• It is obtained by
deacetylation of
Chitin.

25. Modifications
• Chitosan shows solubility issues. Therefore, modification
are done to improve its solubility.
• The primary amine (-NH2) groups of chitosan provide a
reaction site for chemical modification.
• N-trimethyl chitosan chloride has been produced to
improve the solubility.
• The mucoadhesiveness can be enhanced by thiolation to
form chitosan-cysteine, chitosan-glutathione, etc.
• Quaternization derivatives such as trimethyl (TMC),
dimethylethyl (DMEC), aids in the opening of tight
junctions and improving the permeability.

26. Modifications
• Grafting with poly (methyl methacrylate) helps achieve
pH-sensitive properties.
• A pH sensitive polymer gel can be prepared by chemically
linking D,L-lactic acid.
• Lactose modification has been used in combination with
the polyvalent ion tripolyphosphate (TPP) to form highly
uniform and small (200 nm diameter) nanoparticles.

27. Chemical Modifications
Structures of some of functionalized chitosan derivatives.

28. PROPERTIES
Biological Characteristics

29. Mucoadhesion
• The cationic chitosan and anionic acids in the mucous
results in mucoadhesive attributes to chitosan.
• This attribute is instrumental in achieving sustained
release of drug.
• The mucoadhesion increases with the degree of
deacetylation and its molecular weight and decreases with
an increase in crosslinking.

30. Controlled Drug Release
• The ability of chitosan to form ionic crosslinks leads to
formation of stable complexes releasing the drug over a
prolonged period of time conferring controlled drug
release.
• This is beneficial for drugs that show suboptimal plasma
levels.
• It is also useful for carrying drugs that are susceptible to
metabolic degradation in the GIT.

31. Permeation Enhancement
• Chitosan being positively charged, interacts with the
mucus membrane and opens the tight junctions between
the cells, enhancing drug permeation.
• This is beneficial for hydrophilic and high molecular weight
compounds like proteins and peptides. Modified chitosan
like thiolated and trimethyl chitosan show improved
permeation enhancement effect than chitosan.

32. Biocompatibility & Biodegradability
• Chitosan exhibits very good biocompatibility because of
resemblance to glycosaminoglycans and quickly forms
hydrogels through crosslinking methods.
• It is easily degraded by in vivo lysozyme, chitinases and
colon residing bacteria by virtue of the cleavage of
glycosidic linkage in its structure.

33. PREPARATION
Ionic cross linking, Reverse micellar method, Precipitation method,
Emulsion-droplet coalescence method

34. Ionic cross-linking method
• This method involves crosslinking the cationic chitosan
amino groups to a polyanionic crosslinker.
• Tripolyphosphate is the most commonly used cross-
linking agent. Aqueous acidic solution of chitosan is
added dropwise in tripolyphosphate (TPP) solution with
stirring.
• There is a formation of gels due to ionic linkage, therefore
this method is also known as ionic-gelation method.
• This method is simple, mild and easy, the use of aqueous
medium eliminates the hazards and toxicities associated
with the use of organic solvent.
• The NPs prepared by this method have the limitation of
poor mechanical strength.

35. Ionic cross-linking method
Diagrammatic representation of chitosan nanoparticles preparation by
ionic cross-linking technique

36. Reverse micellar method
• This method involves use of four components- polymer,
surfactant, crosslinker (most commonly used is
glutaraldehyde) and an organic solvent (n-hexane,
toluene).
• It involves preparation of surfactant solution in a suitable
organic solvent, preparation of polymer and crosslinker
blend which is added to the surfactant mixture; thus,
yielding the desired polymer-crosslinker NPs.

37. Reverse micellar method
Diagrammatic representation of chitosan nanoparticles preparation by
reverse micellar method

38. Co-Precipitation Method
• In this method, the chitosan solution is blown into an alkali
solution using a compressed air nozzle forming
coacervate droplets. The particles are then separated and
purified by filtration or centrifugation.

39. Precipitation/Coacervation
Illustration representing the preparation of chitosan nanoparticles by
coacervation/precipitation

40. Emulsion-droplet coalescence method
• Two emulsions are prepared:
i. Aqueous solution of chitosan along with the drug is
added in liquid paraffin oil to give water/oil emulsion.
ii. An aqueous solution of chitosan in sodium hydroxide is
mixed in paraffin oil giving a second water/oil emulsion.
• The two emulsions are subsequently mixed with high
speed stirring resulting in collision of droplets of the
emulsions giving rise to coacervates, followed by
centrifugation and filtration to yield chitosan-drug NPs.

41. Emulsion-droplet coalescence method
Diagrammatic representation of preparation of chitosan nanoparticles
by emulsion droplet coalescence method.

42. DRUG RELEASE
Mechanisms of drug release from Chitosan Nanoparticles

43. Drug Release from Chitosan Nanoparticles
The drug release from chitosan NPs occurs by three mechanisms.

44. Erosion
• Erosion occurs in two ways:
o Homogenous erosion occurs at the same rate throughout
the matrix.
o Heterogeneous erosion moves from the surface towards
the inner core.
• Polymer degradation may be due to the surrounding
media or the presence of enzymes. It also depends on the
pH of the surrounding media, the copolymer composition
and water uptake.
• Drug release depends on the type of polymer and internal
bonding, any additives (chitosan derivatives), as well as
the shape and size of the nanoparticles.

45. Diffusion
• The drug permeates from matrix to the surrounding
medium. The mathematical representation of diffusion is
given by Fick’s law of diffusion:
F = −D
∆C
∆x
• F is the rate of transfer per unit area of section (flux), C is
the concentration of the drug and D is the diffusion
coefficient (diffusivity).

46. Swelling
• The swelling of the polymer is due to imbibition of water
into the polymer until the polymer dissolves and the
polymer chains detangle. This is followed by drug release
from that region of the polymer matrix.
• Its factors include polymer solubility, polymer swelling
rate, density of polymer chains, interaction of the polymer
with the drug and particle size.
• One of the important criteria is drug loading in the polymer
nanocarrier, more the drug loading, greater bursting effect
and faster release of the nanocarrier and vice versa.

47. CLINICAL ASPECTS
Pharmacokinetics, Therapeutic Uses, Benefits & Risks

48. Pharmacokinetics of Chitosan NPs
• Chitosan NPs increase the oral bioavailability of drugs.
• The increased intestinal permeation of drugs could be due
to enhanced paracellular transport of the drug across
intestinal epithelium owing to the mucoadhesive property
of chitosan.

49. Mucoadhesion & Bioavailability

50. Therapeutic Uses
• The properties of chitosan NPs are leading to
development of better therapeutics and superior clinical
outcomes.
• These NPs are a potential system for treatment of cancer.
Modifications made in
Chitosan NPs
Drug Inference
Curcumin loaded folate
modified-chitosan NPs
Curcumin
Potential carriers in targeting therapy for
delivering curcumin to cancerous cells
Epidermal growth factor
receptor-targeted chitosan
NPs
Cisplatin
Enhanced the tumour inhibition efficacy
but was surprisingly more effective in
cisplatin-resistant tumours
Hydrophobically modified
glycol chitosan NPs
Camptothecin
Showed marked anti-tumor effects and
high tumour targeting ability.

51. Chitosan Nanoparticles
Advantages
• Toxicity is less
• Enhanced Biocompatibility
• Mucoadhesive character
• Possess stability
• Site-specific drug targeting
• Therapeutic index of the
drug is increased
• Frequent, expensive dosing
is prevented.
Disadvantages
• Less Mechanical resistance
• Pore size difficult to control
• May contract
• Electrospinning is difficult
• Crosslinking can affect
properties of chitosan
• Solubility issues
• Preparation method is
changed with the drug.