!!!!!!!!!!!! POLYMERS !!!!!!!!!!!! 7th Sept. 2010KLECOP, Nipani

INTRODUCTION A polymer is a very large molecule in which one or two small units is repeated over and over again The small repeating units are known as monomers Imagine that a monomer can be represented by the letter A. Then a polymer made of that monomer would have the structure: -A-A-A-A-A-A-A-A-A-A-A-A-A-A-A-A-A-A-A-A-A-A- A-A-A-A 1 14 Aug,2011 Amity, Lucknow

In another kind of polymer, two different monomers might be involved If the letters A and B represent those monomers, then the polymer could be represented as: -A-B-A-B-A-B-A-B-A-B-A-B-A-B-A-B-A-B-A-B-A-B-A-B- A-B-A A polymer with two different monomers is known as a copolymer. 14 Aug,2011 Amity, Lucknow 2

Chemistry of the polymers Polymers are organic, chain molecules They can, vary from a few hundreds to thousands of atoms long. There are three classes of polymers that we will consider:- a. Thermo-plastic - Flexible linear chains b. Thermosetting - Rigid 3-D network c. Elastomeric - Linear cross-linked chains 14 Aug,2011Amity,Lucknow 3

THERMOPLASTICS In simple thermoplastic polymers, the chains are bound to each other by weaker Van der Waal’s forces and mechanical entanglement. Therefore, the chains are relatively strong, but it is relatively easy to slide and rotate the chains over each other. 14th Aug. 2011Amity, lucknow 4

ELASTOMERS Common elastomers are made from highly coiled, linear polymer chains. In their natural condition, elastomers behave in a similar manner to thermoplastics (viscoelastic) – i.e. applying a force causes the chains to uncoil and stretch, but they also slide past each other causing permanent deformation. This can be prevented by cross-linking the polymer chains 14th Aug. 2011Amity, lucknow 5

MOLECULAR STRUCTURE The mechanical properties are also governed by the structure of the polymer chains. They can be: Linear Network (3D) Branched Cross-linked 14th Aug. 2011Amity, lucknow 7

POLYMER MOLECULES Before we discuss how the polymer chain molecules are formed, we need to cover some definitions: The ethylene monomer looks like The polyethylene molecule looks like: 14th Aug. 2011Amity, Lucknow 8

CHARACTERISTICS OF AN IDEAL POLYMER Should be versatile and possess a wide range of mechanical, physical, chemical properties Should be non-toxic and have good mechanical strength and should be easily administered Should be inexpensive Should be easy to fabricate Should be inert to host tissue and compatible with environment 14th Aug. 2011Amity, Lucknow 9

CRITERIA FOLLOWED IN POLYMER SELECTION The polymer should be soluble and easy to synthesis It should have finite molecular weight It should be compatible with biological environment It should be biodegradable It should provide good drug polymer linkage 14th Aug. 2011Amity, lucknow 10

APPLICATIONS The pharmaceutical applications of polymers range from their use as binders in tablets Viscosity and flow controlling agents in liquids, suspensions and emulsions Polymers are also used as film coatings to disguise the unpleasant taste of a drug, to enhance drug stability and to modify drug release characteristics. 14th Aug. 2011Amity, lucknow 11

Applications in Conventional Dosage Forms 14th Aug. 2011Amity, lucknow Tablets : - As binders - To mask unpleasant taste - For enteric coated tablets Liquids : - Viscosity enhancers - For controlling the flow Semisolids : - In the gel preparation - In ointments In transdermal Patches 12

Applications In Controlled Drug Delivery Reservoir Systems - Ocusert System - Progestasert System - Reservoir Designed Transdermal Patches Matrix Systems Swelling Controlled Release Systems Biodegradable Systems Osmotically controlled Drug Delivery 14th Aug. 2011Amity, lucknow 13

BIO DEGARADABLE POLYMERS 14th Aug. 2011Amity, lucknow 14

BIO DEGRADABLE POLYMER Biodegradable polymers can be classified in two: Natural biodegradable polymer Synthetic biodegradable polymer Synthetic biodegradable polymer are preferred more than the natural biodegradable polymer because they are free of immunogenicity & their physicochemical properties are more predictable &reproducible 14th Aug. 2011Amity, lucknow 15

ROLE OF POLYMER IN DRUG DELIVERY The polymer can protect the drug from the physiological environment & hence improve its stability in vivo. Most biodegradable polymer are designed to degrade within the body as a result of hydrolysis of polymer chain into biologically acceptable & progressively small compounds. * TYPES OF POLYMER DRUG DELIVERY SYSTEM: MICRO PARTICLES: These have been used to deliver therapeutic agents like doxycycline. NANO PARTICLES: delivery drugs like doxorubicin, cyclosporine, paclitaxel, 5- fluorouracil etc 14th Aug. 2011Amity, Lucknow 16

POLYMERIC MICELLES: used to deliver therapeutic agents. HYDRO GELS: these are currently studies as controlled release carriers of proteins & peptides. POLYMER MORPHOLOGY: The polymer matrix can be formulated as either micro/nano-spheres, gel, film or an extruded shape. The shape of polymer can be important in drug release kinetics. 14th Aug. 2011Amity,Lucknow 17

Application For specific site drug delivery- anti tumour agent Polymer system for gene therapy Bio degradable polymer for ocular, non- viral DNA, tissue engineering, vascular, orthopaedic, skin adhesive & surgical glues. Bio degradable drug system for therapeutic agents such as anti tumor, antipsychotic agent, anti-inflammatory agent and biomacro molecules such as proteins, peptides and nucleic acids 14th Aug. 2011Amity, Lucknow 18

Natural polymers Polymers are very common in nature some of the most widespread naturally occurring substances are polymers Starch and cellulose are examples Green plants have the ability to take the simple sugar known as glucose and make very long chains containing many glucose units These long chains are molecules of starch or cellulose If we assign the symbol G to stand for a glucose molecule, then starch or cellulose can be represented as: -G-G-G-G-G-G-G-G-G-G-G-G-G-G-G-G-G-G-G-G-G-G-G-G-G-G-G- 14th Aug. 2011Amity. Lucknow 19

NATURAL POLYMERS Natural polymers remains the primary choice of formulator because - They are natural products of living organism - Readily available - Relatively inexpensive - Capable of chemical modification Moreover, it satisfies most of the ideal requirements of polymers. But the only and major difficulty is the batch- to-batch reproducibility and purity of the sample. 14th Aug. 2011Amity, Lucknow 20

RECENTLY DEVELOPED MARKETED FORMULATIONS Medisorb Microencapsulation by PLA, PGA, PLGA Drug release : week to one year Alzamer Bioerodible polymer : release at a controlled rate Chronic disease, contraception, topical therapy 14th Aug. 2011Amity,Lucknow 21

REFERENCES Novel drug delivery systems – Y.W.Chien – Dekker 50 Bio–adhesive drug delivery system – Dekker 98 Encyclopedia of controlled drug delivery systems. 14th Aug. 2011Amity, Lucknow 22

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