Polymers have become a necessary commodity of everyday life and are used for manufacturing of hundreds of things of our daily use from house hold items to transportation and communication. Polymers are also used in medicine; however, all the polymers cannot be used for this purpose. For medical applications, a polymer should have the following properties: (a) bio-safe and non-toxic which means that it should be non-carcinogenic, non-teratogenic, non-mutagenic, non-cytotoxic, non-pyrogenic, nonhemolytic, non-allergenic and chronically non-inflammative etc. (b) must be effective in terms of functionality, durability, and performance (c) must be interfacial, mechanically and biologically biocompatible and (d) sterilizable through different techniques like autoclave, dry heating, electron beam irradiation etc. It should also be chemically inert and very stable i.e. it should not decay or disintegrate to give obnoxious toxic products with the passage of time especially when it is intended to be implanted within body. The selection of a polymer for a particular medical application is also made upon the basis of its host response. Therefore a biopolymer is any polymeric non-viable material which is used in medical devices or applications that where it is intended to interact with biological systems such as tissues, cells, bones, blood and any other living substance.
Biopolymers used in manufacture of medical devices which are used to replace or repair some diseased, damaged or non-functional piece of tissue or bone like replacement of joints, heart valves, arteries, teeth, tendons, ligaments, ocular lenses etc. More advanced devices are used to partially or entirely replace or assist in functioning of a vital organ like lung, kidney, liver, heart etc. Furthermore, biocompatible and degradable polymers are used to prepare advanced and efficient drug delivery systems. Drugs (like pilocarpine, contraceptives, insulin etc.) are encapsulated within polymeric microcapsules for their controlled and sustained release or targeted delivery of drugs (like delivery of an anticancer drug only to the tumor).
Biopolymers are of two types; Natural and Synthetic. Synthetic biopolymers include polylactic acid, polyglactin, and polyhydroxy apatite which are porous and fibrous materials used for making bone implants, artificial tendon, ligament and artificial blood vessels. Polytetrafluoroethylene, due to its high chemical resistance is used for the manufacture of medical implants, dental fillings, and microfiltration membranes. Polyethylene is used in preparation of packaging, containers, films and breather patches. Syringes, medical trays, statures, beauty aid products etc. are made of polypropylene. Polystyrene is used for miscellaneous laboratory ware like petri dishes etc. Polyvinyl chloride is used for drip chamber, sterilized gloves, oxygen face masks, blood bags etc. Polymethylmethacrylate is used for cavity fillings, incubators, breathing apparatus accessories, diagnostics. Polyurethanes are used in skin prosthesis and silicon polymers are used for breast other implants. Glutaraldehyde hydrogels, polycyanoacrylates, and polyalkylene oxides are used as hemostatic materials and are used in wool, dressing, powder, and sprays for stopping bleeding. Polyethyleneimine and polymer based hydrogels are used as matrix for tissue culture in the form of sponge, mesh, nonwoven fabrics, and tubes. Synthetic polymers have advantages such as easy manufacturing, high process ability, low cost of production but they also have disadvantages such as nonrenewable, have poor resistance to UV and ozone sometimes rejected by host body.
Natural polymers are obtained from living organisms and more biocompatible. Collagen is obtained from bovines of cows, horses and other animals. It is used for wound healing, reconstruction of bones, skin, heart valves etc. Chitosan is used as hemostatic material to stop bleeding and is obtained from exoskeleton of marine animals such as crabs, shrimps etc. and. It is also used as filler in the tablets. Dextran is obtained from sucrose by action of certain bacteria and is used for increased blood sugar level, in eye drops, and in preparation of iron dextran injections. Cellulose is used for preparation of drug delivery systems such as tablet and pills coatings, granules and microcapsules. Gelatin is used as anti-adhesion material in the form of like sheet, jelly, and spray. Natural polymers may have advantages such as they are non-allergic, non-toxic, antiviral, fungistatic, and may provide bioactive sites etc. However, they also have disadvantages like high water absorption, small production and high cost, low physical, chemical and mechanical resistance.
In conclusion, the biopolymers have intrinsic properties which make them suitable for various biomedical applications for which other polymers are not suitable. Biopolymers have been in use for last several decades in medicine and surgery for preparation of many medical and body implants. The research is still continuous in search of better biopolymers with more biocompatibility, better mechanical properties, and longer shelf life.
This article is jointly authored by Smiya Mushtaq and Dr. Muhammad Irfan Majeed Department of Chemistry, University of Agriculture Faisalabad.