The document discusses the role of polymers in drug delivery systems, detailing their definitions, classifications, and mechanisms of drug release. It highlights the significance of various types of polymers, including natural and synthetic, biodegradable and non-biodegradable, and their therapeutic applications in maintaining controlled medication release. Additionally, it covers different methods of polymer utilization, such as diffusion and degradation mechanisms, for enhancing drug absorption and effectiveness.

1. NOVEL DRUG DELIVERY SYSTEM
- Akanksha Patel
Unit 1
Polymers
Definition- “Polymers are long chain organic molecules assembled from many smaller
molecules called as monomers.”
- Polymer word is derived from Greek root ‘poly’ means many and ‘meros’ means parts.
- Long chain organic molecules assembled from many smaller molecules called monomers.
- Copolymer: Polymers formed from two or more different monomers are called as
copolymers. Eg. - [A – B – A – B – A – B] –
- Homopolymer : Polymers formed from bonding of identical monomers are called as
homopolymers. Eg. - [A – A – A – A – A] –
Significance- 1. In the field of drug delivery, polymers are becoming increasingly significant.
2. Polymers are the major tool for controlling the medication release rate from the formulation.
3. Polymers can be used to conceal the flavour of a medicine, improve its stability, and change
its release properties.
General mechanism of drug release from polymer There are three primary mechanisms-
a. Diffusion- it occurs when the drug passes from the polymer matrix into the external
environment.
b. Degradation- Biodegradable polymer degrades within the body as a result of natural biological
processes, eliminating the need to remove a drug delivery system after release of the active
agent has been completed.
c. Swelling- They are initially dry and when placed in the body will absorb water or other body
fluids and swell.
Classification-
1) Based on the origin-
i) Natural Polymers-
Protein-based: Albumin, Collagen, gelatine, keratin etc.
Carbohydrates: starch, cellulose, glycogen.
Polysaccharides: Agarose, alginate, carrageenan, chitosan, cyclodextrins, dextran, hyaluronic
acid, polysialic acid etc.
ii) Synthetic Polymers / Based on Bio-stability:
a, Biodegradable

2. NOVEL DRUG DELIVERY SYSTEM
- Akanksha Patel
Polyesters: Poly lactic acid (PLA), poly glycolic acid (PGA), poly hydroxyl butyrate (PHB),
poly Ɛ-caprolactone (PCL), poly β-malic acid (PMA), poly dioxanones (PDA) etc.
Polyanhydrides: Poly sebacic acid (PSBA), poly adipic acid (PAPA), poly terphthalic acid
(PTA) and various copolymers etc.
Polyamides: Poly imino carbonates (PIC), polyamino acids (PAA) etc.
Phosphorus-based: Polyphosphates, polyphosphonates, polyphosphazens etc.
Others: Poly cyano acrylates (PCA), polyurethanes, polyortho esters, polydihydropyrans,
polyacetals etc.
b, Non-biodegradable
Cellulose derivatives: Carboxy methyl cellulose (CMC), ethyl cellulose (EC), cellulose
acetate (CA), cellulose acetate propionate (CAP), hydroxypropyl methylcellulose (HPMC).
Silicones: Polydimethylsiloxane (PDS), Colloidal silica etc.
Ethyl cellulose Insoluble but dispersible in water, aqueous coating system for sustained release
Acrylic polymers: Polymethacrylates (PMA), poly methyl methacrylate (PMMA), poly hydro
ethyl methacrylate (PHEM) etc.
Others: Polyvinyl pyrrolidone (PVP), ethyl vinyl acetate (EVA), poloxamers, poloxamines.
iii) Semi-synthetic Polymer: Hydrogenated natural rubber, Cellulose nitrate, methyl cellulose
etc are chemically modified polymers.
2. Based on origin-
Polymers with carbon chain backbone: Polyethylene, polypropylene, polystyrene, poly vinyl
chloride, polytetrafluoroethylene, poly acrylonitrile, poly vinyl alcohol, poly vinyl acetate,
polyacrylamide, poly methyl methacrylate, poly vinyl pyrrolidone, etc.
Polymers with hetero chain backbone: Poly ethylene oxide, poly propylene oxide, cellulose
(poly –glucoside,β →1,4), amylase (poly-glucoside, alpha → 1,4) (component of starch),
pectinic acid (polygalacturonoside), polyethylene glycol terphthalate, polydimethylsiloxane.
3. Based on the presence of carbon (organic and inorganic)-
Organic Polymers: Polymer whose backbone chain is essentially made of carbon atoms.
Inorganic Polymers: The molecules of inorganic polymers, contain no carbon atom in their
chain backbone. Glass and silicone rubber are examples of inorganic polymers.
4. Based on the types of monomer-
Homoplymer: A polymer containing a single type of repeat units, e.g., polystyrene.
Copolymer: two different monomers, e.g., styrene butadiene (SBS) rubber and Sty-co-An.
5. Based on the Polymerization process-

3. NOVEL DRUG DELIVERY SYSTEM
- Akanksha Patel
Addition polymers: this reaction is responsible for formation of polymer. Double and triple
bonds are possessed by these monomer molecules.eg polythene, polypropene, polystyrene, pvc
Condensation polymers: this reaction is responsible for the formation of polymers elimination
of small molecule such as water, alcohol, HCl, takes place by this polymerization reaction.
(i) Chain growth polymer: Chain polymers are the products of self-addition reaction of
monomer molecules through a chain reaction. e.g., all the vinyl monomers.
(ii) Step growth polymers: this reaction involves a random reaction of two molecules that
may be any combination of a monomer, oligomer or a long chain molecule. Ex. nylons,
polyurethanes.
6. Based on the Line structure-
i) Linear Polymer: A straight chain species. e.g. high density polyethylene.
ii) Branched Polymer: The main chains of polymer molecules have small branches of the
same or different molecules. e.g. comb like polymers, star polymers, dendrimers, low density
polyethylene, graft copolymers etc.
iii) Cross-linked Polymer: two linear polymer chains are joined together by covalent bonds
i.e, cross-linked. E.g., Bakelite. Vulcanized rubber Novolac, melamine-formaldehyde.
7. Based on thermal characteristics / thermo response-
i) Thermoplastic polymers: They can be softened on heating and hardened on cooling, e.g.
are Polyolefin, nylons, linear polyesters and polyether’s, PVC, sealing wax etc.
ii) Thermosetting polymers: Conversion of polymers into an infusible mass is because of
chemical changes. That cannot be softened once get solidified either by heating or by curing
agents. eg, crosslinked epoxy resins, polydicyclopentadiene, polycarbonates, polyisoprene, etc.
8. Based on interaction with water-
i) Non‐biodegradable hydrophobic Polymers: E.g. Polyvinyl chloride.
ii) Soluble Polymers: CP, HEC, HPC, HPMC, PEG, PAA, sodium CMC, sodium alginate.
Water-Soluble Synthetic Polymers-
· Poly (acrylic acid) Cosmetic, immobilization of cationic drugs, base for Carbopol polymer
· Poly (ethylene oxide) Coagulant, flocculent, very high mol wt ~ millions, swelling agent
· Poly (ethylene glycol) MW <10,000; liquid (MW <1000) and wax (MW >1000),
plasticizer, base for suppositories
· Poly (vinyl pyrrolidone) Used to make betadine (iodine complex of PVP) with less toxicity
than iodine, plasma replacement, tablet granulation
· Poly (vinyl alcohol) Water-soluble packaging, tablet binder, coating Polyacrylamide Gel
electrophoresis to separate proteins based on their molecular weights, coagulant, absorbent.

4. NOVEL DRUG DELIVERY SYSTEM
- Akanksha Patel
· Poly (isopropyl acrylamide) and poly (cyclopropyl methacrylamide)
· Thermo-gelling acrylamide derivatives, its balance of hydrogen bonding, and hydrophobic
association changes with temperature.
iii) Insoluble polymers: Chitosan (soluble in dilute acids), ethyl cellulose, PC.
Water-Insoluble Biodegradable Polymers- (Lactide-co-glycolide) For protein delivery.
Starch-Based Polymer- Sodium starch glycolate Superdisintegrant for tablets and capsules in
oral delivery Starch Glidant, a diluent in tablets and capsules, a disintegrant in tablets and
capsules, a tablet binder.
Hydrocolloids- Carrageenan Modified release, viscosifier, Chitosan Cosmetics and controlled
drug delivery, Pectinic acid, Alginic acid.
Cellulose-Based Polymers- HPMC Binder for tablet matrix and tablet coating, gelatine
alternative as capsule material.
-Hydroxyethyl and hydroxypropyl cellulose Soluble in water and in alcohol, tablet coating
iv) Hydro gels: Polyvinyl pyrrolidone.
9. Based on stimuli response-
classified in three categories: physical, chemical, or biological.
I) Physical stimuli (light, temperature, ultrasound, magnetic, mechanical, electrical)
ii) chemical stimuli (solvent, ionic strength, electrochemical, pH)
iii) Biological stimuli (enzymes, receptors)
Photoresponsive polymers: PAA, PHPMAm, PNIPAM.
pH responsive polymers: Chitosan, albumin, gelatine, poly acrylic acid (PAAc)/chitosan IPN,
poly methacrylic acid-g-ethylene glycol [P(MAA-g-EG)], poly ethylene imine (PEI),
poly(N,N-diakylamino ethylmethacrylates) (PDAAEMA), and poly lysine (PL).
Inflammation responsive polymers: Hyaluronic acid.
Temperature responsive polymers: Poly(N-alkyl substituted acrylamides): e.g. poly(N-
isopropylacrylamide) (PNiPAAm), Poly (N-vinylalkylamides): e.g. poly(N-vinylcaprolactam)
(PNVC), and copolymers such as poly (L-lactic acid)-poly(ethylene glycol)-poly(L-lactic acid)
(PLLA-PEG-PLLA) triblock copolymers, and poly (ethylene oxide)-poly(propylene oxide)-
poly (ethylene oxide) (PEO–PPO–PEO) copolymers.
Electro-Responsive Polymers: Polythiophene (PT) or sulphonated-polystyrene (PSS).
Redox-Responsive Polymers: Acid labile moieties inside polyanhydrides,
poly(lactic/glycolic acid) (PLGA), and poly(b-amino esters) (PbAEs) induce redox
responsiveness.
Enzyme-Responsive Polymers: Pectin, chitosan, amylase/amylopectin, cyclodextrin, dextrin.

5. NOVEL DRUG DELIVERY SYSTEM
- Akanksha Patel
10. Based on Morphology-
Crystalline Polymers: e.g., syndiotactic polypropylene.
Amorphous polymers: e.g., atactic polypropylene.
11. Based on tacticity-
i) Isotactic polymers: A polymer in which substituents group is located on one side of plane
of carbon-carbon chain, every chiral carbon has the same configuration, E.g: Isotactic
polypropene.
ii) Syndiotactic polymers: A polymer, in which substituents group is attached alternatively
above and below the plane of carbon-carbon chain. E.g. syndiotactic polypropylene
iii) Atactic polymers: in which there is no systematic configuration, e.g., atactic
polypropylene.
12. Based on Charge-
Cationic: Aminodextran, chitosan, (DEAE)- dextran, TMC
Anionic: Chitosan-EDTA, CP, CMC, pectin, PAA, PC, sod alginate, sod CMC, xanthan gum
Non-ionic: Hydroxy ethyl starch, HPC, poly (ethylene oxide), PVA
13. Based on Potential-
Covalent: PVP, scleroglucan
Hydrogen bond: Cyanoacrylate
14. Based on bioadhesive forces-
Electrostatic interaction: Acrylate (hydroxylated methacrylate), poly (methacrylic acid), CP,
PC, PVA, chitosan.
15. Based on Physical properties-
Elastomers: e.g., Natural rubbers, synthetic rubber.
Plastic: e.g., polyethylene, polystyrene.
Fibres: e.g., saran, vinyon, orlan.
Plastics and Rubbers-Polycyanoacrylate Biodegradable tissue adhesives in surgery.
Polystyrene Petri dishes and containers for cell culture
Poly(methyl methacrylate) Hard contact lenses
Poly(hydroxyethyl methacrylate) Soft contact lenses
Poly(vinyl chloride) Blood bag, hoses, and tubing
Poly (vinyl acetate) Binder for chewing gum
Polyurethane Transdermal patch backing.
Polycarbonate Case for biomedical and pharmaceutical products

6. NOVEL DRUG DELIVERY SYSTEM
- Akanksha Patel
Polychloroprene Septum for injection, plungers for syringes, and valve components
Polyisobutylene Pressure sensitive adhesives for transdermal delivery
# based on chemical nature- Polymer Vinyl Polymers Polymethacrylates, Polyvinyl
Alcohols, Polyvinyl Pyrrolidone (Povidone), Poly(Acrylic Acid) (Carbomer) Cellulose Ethers
Methycellulose, Ethycellulose, Hydroxy ethyl cellulose (HEC), Hydroxy propyl cellulose
(HPC), Hydroxy propyl methyl cellulose (HPMC):Hydroxy ethyl methyl cellulose (HEMC),
Sodium carboxy methyl cellulose Polyesters Poly (lactic) and related copolymers, Poly (ε-
caprolactone), polyglycolide Polysac charides Chitosan, Carragenan, Tragacanth, Acacia,
Poly(allginic acid), xanthum gum Miscellaneous Polymers Gelatin, polyanhydrides,
polyethyleneglycols, poyethyene oxides.
IDEAL CHARACTERISTICS OF POLYMERS
 Shouldbeinert
 Shouldbeinexpensive
 Shouldhavegoodmechanicalstrength
 Shouldbenontoxic
 Shouldbecompatiblewithenvironment
 Shouldhavelowcoefficientoffriction
 Shouldhavegoodmoldabilityandgoodcorrosionresistance
 Canbeproducedtransparentorindifferentcolours
 Shouldbeeasyandinexpensivetofabricate
 Shouldhavegoodmechanicalstrength
ADVANTAGES OF POLYMER
• Polymers used in colloidal drug carrier systems, consisting of small particles, show great advantage in drug
deliverysystemsbecauseofoptimizeddrugloadingandreleasingproperty.
• Apolymer(naturalorsynthetic)givesaneffectiveandcontrolleddoseofavoidingoverdose.
• Thedegradablepolymersarerupturedintobiologicallysuitablemoleculesthatareassimilatedanddiscarded
fromthebodythroughnormalroute.
• Reservoir based polymers is advantageous in various ways like it increases the solubility of incompetently
solubledrugsanditlowerstheantagonisticsideeffectsofdrugs.
• InBiodegradablepolymers,thesystemisbiocompatibleanditwillnotshowdoseleavingbehindatanytime
andthepolymerwillkeepitspropertiesuntilafterexhaustionofthedrug.

7. NOVEL DRUG DELIVERY SYSTEM
- Akanksha Patel
• Polymersspanfromtheiruseasfilmsorbinderscoveringagentsintabletstoflowmanagingagentinliquids
oremulsionsforimprovingdrugsecurityandtoalterthedeliveringcharacteristics.
• • Biggestbenefitofutilizingpolymersindrugdeliveryistheircontrol(manipulation)ontheirproperties(e.g.
linkersandmolecularweight)tomodifytotheneedofdrugdeliverysystems.
APPLICATION OF POLYMERS IN FORMULATION OF CONTROLLED
RELEASEDRUG DELIVERY SYSTEMS
Inorderforcontrolleddrugdeliveryformulation,thepolymersmustbechemicallyinertandfreefromimpurities
withappropriatephysicalstructure,minimalundesiredaging,andtoreadilymanufactured.
Fewexamples:
•Poly (ethylene-co-vinyl acetate) •Poly (methyl methacrylate) •Poly (vinyl alcohol) •Poly (N-vinyl
pyrrolidone) •Poly(acrylicacid) •Polyacrylamide •Poly(methacrylicglycol) •Poly(etheleneglycol).
Dissolution controlled systems
A drug with a slow dissolution rate is inherently sustained and for those drug with higher water solubility, one
can decrease dissolution trough specific polymer is used. These systems are most commonlyemployedin the
production of enteric coated dosage forms. Polymer used:Poly vinyl pyrrolidone, Waxeslike Beeswax,
carnaubawax,Methylcellulose
Diffusion controlled system- Diffusionprocessshowsthemovementofdrugmoleculesfromaregionof
a higher concentration to one of lower concentration. This drug delivery system can be prepared either by
encapsulatingthedruginpolymerordispersingthedruginthematrix.Polymerusedinmatrixsystem:Xanthan
gum, sodium alginate, carnauba wax, beeswax, Polymer used in reservoir system: Ethyl cellulose, polyvinyl
acetate
Microspheres and microcapsules- Micro/Nanospheresarematrixsysteminwhichthedrugisdispersed
withinthepolymerthroughoutthebodyofparticle.Micro/Nanocapsulesarevesicularsystemsinwhichcavity
contains drug and is surrounded by a single ultrathin membrane of polymer (reservoir systems for controlled
release of drug). Drugs are released fromthe microsphere and microcapsule by diffusion throughthe polymer
or by degradation of the polymer. E.g. Lupron Depot is an injectable microsphere which is made up of lactic
acid-glycolicacidcopolymer
Modified drug release dosage forms- To achieve gastro retention mucoadhesive and low density,
polymershavebeenevaluated,withlittlesuccesssofartheirabilitytoextendgastricresidencetimebybonding
tothemucusliningofthestomachandfloatingontopofthegastriccontentsrespectively.
Extended release dosage forms- Extended and sustained release dosage forms prolong the time that’
systemicdruglevelsarewithinthetherapeuticrangeandthusreducethenumberofdosesthepatientmusttake

8. NOVEL DRUG DELIVERY SYSTEM
- Akanksha Patel
to maintain a therapeutic effect thereby increasing compliance. The most commonly used water insoluble
polymersareethylcellulose,celluloseacetate,polyvinylderivative,polyvinylacetate.
Gastro retentive Dosage forms- Gastroretentivedosageformsofferanalternativestrategyforachieving
extended release profile,in which the formulation will remain in the stomach for prolonged periods, releasing
thedrugin-situ,whichwillthendissolveintheliquidcontentsandslowlypassintothesmallintestine.
Polymers used as colon targeted drug delivery- Polymers play a very important role in the colon
targeteddrugdeliverysystem.Itprotectsthedrugfromdegradationorreleaseinthestomachandsmallintestine.
Italsoensuresabruptorcontrolledreleaseofthedrugintheproximalcolon.
Polymers in the mucoadhesive drug delivery system- Thenewgenerationmucoadhesivepolymers
for buccal drug delivery with advantages such as increase in the residence time of the polymer, penetration
enhancement,sitespecificadhesionandenzymaticinhibition.
Polymers as floating drug delivery system- Polymersaregenerallyemployedinfloatingdrugdelivery
systems so as to target the delivery ofdrug to a specific region in the gastrointestinal tract i.e. stomach. Natural
polymers which havebeen explored for their promising potential in stomach specific drug delivery include
chitosan,pectin,xanthangum,guargum,gellangum
Implants- Inmostoftheimplants(adrugdeliverysystem),apermeablepolymericmembranesurroundsthe
coreofsoliddrugs.Theimplantscanbeclassifiedasnon-biodegradableandbiodegradableimplants,depending
on the polymerused.The polymers mostly usedinthe non-biodegradableimplantsinclude polyvinyl alcohol,
siliconeandethylenevinylacetate.
Polymers in ocular drug delivery- For developing the liquid ocular delivery system, the hydrophilic
polymersshouldbeusedbecausetheycanbeusedasviscositymodifyingorenhancingagent.Polysaccharides
arefrequentlyusedintheocularmucoadhesivedeliverysystem.E.g.hyaluronicacid,methylcellulose,hydroxyl
propylmethylcellulose,gellangum,chitosan,xanthangum,carrageenanandguargum
Transdermal drug delivery- Transdermal drug delivery involves the diffusion of the drug through the
skin and ultimately absorption into the systemic circulation. The drug delivery system is composed of several
layers, namely a metallic backing layer, which is impermeable to drug diffusion thereby preventing drug loss,
thedrugcontainingreservoir,aratecontrollingmembraneandanadhesivelayer.Inthematrixdrugisdissolved
ordispersedwithsolidpolymer(acrylateco-polymer).