ABSTRACT
Biodegradable polymers can be either natural or synthetic. However, synthetic polymers offer greater advantages and possibilities of use because they can be molded into anything you need them to be. The main advantages of synthetic biodegradable polymers are their strength, degradability, adhesiveness, non-immunogenicity, non-inammatory, and non-toxicity. They can be easily sterilized and have good shelf life. Biodegradable polymers are designed to degrade upon disposal by the action of living organisms. They are the most versatile class of biomaterials, being extensively applied in medicine and biotechnology, as well as in the food and cosmetics industries, surgical devices, implants, articial organs, prostheses and sutures, drug-delivery systems, tissue engineering, dental applications, cardiovascular applications, bone replacement, enzymes and cells immobilization, biosensors, bioadhesives, ocular devices, and materials for orthopedic applications.1,2 Biodegradation of polymers takes place through the action of enzymes and/or chemical deterioration associated with living organisms. This event occurs in two steps. The rst one is the fragmentation of the polymers into lower molecular mass species by means of either abiotic reactions, i.e., oxidation, photodegradation, or hydrolysis, or biotic reactions, i.e., degradation by microorganisms. This is followed by bioassimilation of the polymer fragments by microorganisms and their mineralization.1-3
Natural polymers and some of the synthetic polymers have biodegradable properties and are utilized in designing of drug delivery systems for the purpose of controlled release of drugs or other active ingredients. The purpose of polymers in the system is to immobilize active drug molecules and protect them from the environmental physiological conditions, then deliver drugs to the pathological cell or other specic body organ in order to increase the effectiveness of drugs and thus reducing undesirable side effects resulting in an increase in bioavailability of active molecules in the body.2,4 Polymers that are used to formulate drug delivery systems should have some specic properties such as biocompatibility, non-toxicity, and have a well-dened structure. Taking this point in mind, many polymers have been invented with the desired physiological properties, which are utilized in the development of various drug delivery systems such as biodegradable drug delivery systems, diffusion controlled, and responsive drug delivery systems. Biodegradability of polymers can easily be modied by incorporating a variety of labile groups such as ester, orthoester, anhydride, carbonate, amide, urea, and urethane in their backbone.5-12
Biodegradation is a process in which the enzymes produced by microorganisms breakdown or assimilate the organic substances. Such living organisms use these organic substances as a carbon and food/energy source. Biological degradation of polymers occurs either in the presence of oxygen (aerobic biodegradation) or in the absence of oxygen (anaerobic biodegradation) in which carbon dioxide, water, and biomass are the ultimate end products in both the processes while methane, an additional byproduct, is also formed in the anaerobic biodegradation.
