Polymer for Medical Applications

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					Polymer for Medical Applications

Biodegradable Polymers as Drug Carrier Systems
• Polyesters
– Lactide/Glycolide Copolymers
• Have been used for the delivery of steriods, anticancer agent, antibiotics, etc. • PLLA is found as an excellent biomaterials and safe for in vivo (Lactic acid contains an asymmetric α-carbon atom with three different isomers as D-, L- and DL-lactic acid) • PLGA is most widely investigated biodegradable polymers for drug delivery. • Lactide/glycolide copolymers have been subjected to extensive animal and human trials without any significant harmful side effects

Biodegradable Polymers as Drug Carrier Systems
• Poly(amides)
– Natural Polymers
• Remain attractive because they are natural products of living organism, readily available, relatively inexpensive, etc. • Mostly focused on the use of proteins such as gelatin, collagen, and albumin

Biodegradable Polymers as Drug Carrier Systems
• Polymer Processing
– Drug-incorporated matrices can be formulated either compression or injection molding – Polymer & drug can be ground in a Micro Mill, sieve into particle size of 90-120 µm, then press into circular disc – Alternatively drug can be mixed into molten polymer to form small chips, then it is fed into injection molder to mold into desired shape

Biodegradable Polymers as Drug Carrier Systems
• Why nanoparticles are desired for drug delivery system?

Biodegradable Polymers as Drug Carrier Systems
• Nanoparticles can be used to increase drug solubility, have lower toxicity & target drug delivery • In order to use nanoparticle as drug delivery, they must satisfy number of criteria;
– Biocompatible – Good drug payload – Manufacturing cost must be reasonable

Polymer for Dental Application
• Four main groups of materials used in dentistry;
– Metal and alloys – Ceramics – Synthetic organic polymers & biopolymers (derived from natural tissues) – Composites (an organic matrix polymers filled with inorganic fine particles)

Polymer for Dental Application
• In 19th century, gutth-percha was used for filling • In 1909, PMMA was used as artificial teeth filling • In 1930s, polyamide, polyester, polyethylene were prepared in different forms (rigid, soft, fibers, adhesives, etc) for several applications (filling, implant, sutures, etc)

Schematic of different area of chemistry

Polymer for Dental Application
• Bases, liners and varnishes for cavities
– There is a large diversity or organic and inorganic materials for this purposes – Zinc polycarboxylate (or polyacrylate) cement is prepared by mixing zinc oxide and the polymer solution, and water solution of polyacrylic acid

Polymer for Dental Application
• Filling & Restorative Materials
– Made up of organic matrix and inorganic particulate or fibrous filling. Held together by coupling agent – PMMA resins have been used as filling materials, but they have several disadvantages
• • • • Nonadhesion to dental structures Low colour stability Low molecular weight of monomer High polymerization shrinkage

Textile based Biomaterials for Surgical Application
• 2000 BC, natural fibers like linen, silk, horsehair were used as suture materials • After world war II revolution of medical textile, used of steel wire and synthetic fibers (PP, nylon, polyester) • In early 1970s, two synthetic absorbable wound closure biomaterials, i.e. Dexon & Vicyrl were introduced • The four most widely used textile structure; woven, knitted, nonwoven and braided

Commercial Suture materials

Braided Polyester

Multifilament nylon


Textile based Biomaterials for Surgical Application
• Wound closure biomaterials are divided into;
– Suture materials – Tissue adhesives – staplers

Textile based Biomaterials for Surgical Application
• Suture- is a strand of textile materials (natural or synthetic), used to ligate blood vessel and draw tissue together • Ideal suture should
– Physical and mechanical properties (adequate tensile strength, etc) – Handling properties (easy to handle) – Biological properties (unfavourable for bacterial growth) – Biodegradation properties (absorbable; its tensile strength loss must match the healing rate of the tissue to be closed)

Table of Relative Tissue Reactivity to Sutures

Textile based Biomaterials for Surgical Application
• Suture materials can be classified into 2 broad categories;
– Absorbable;loss their entire tensile strength within two to three months – Nonabsorbable; retain their strength longer than two to three months

Biocompatibility of Elastomer
• Elastomer-definition
– Flexible- i.e.have low rigidity – Highly deformable, i.e. able to withstand strong deforming forces without rupturing and have elongation at rupture over 200% – Elastic or resilient, i.e. able to return to their original shape and size after deforming forces is removed

Biocompatibility of Elastomer
• Various famililes of Elastomers
– General-use elastomer- natural rubber (NR), styrene butadiene rubber (SBR), etc – Special elastomer- ethylene propylene and diene copolymer (EPM, EPDM), nitrile butadiene copolymer (NBR) – Very special elastomers- high thermal and/or chemical resistance elastomerfluoroelastomer, silicone elastomer, etc – Thermoplastic elastomer

Biocompatibility of Elastomer
• Silicone elastomer
– Widely used because it is strong, very mobile bone of their Si-O-Si (siloxane) caternary backbone; which provide chemical inertness and flexibility, stable over time at a body temp., show little tissue reactivity, and highly resistant to chemical attack and heat.

Medical device in human body