Synthesis, characterization, biodegradation, and drug delivery applicationof biodegradable lactic/glycolic acid polymers. Part II: Biodegradation

A series of previously-synthesized lactic/glycolic acid polymers (PLGA) wit h various molar ratios of lactic to glycolic acid and various molecular wei ghts were further studied with regard to their biodegradation behavior, and in particular, the factors affecting the biodegradation rate. The biodegra dation of PLGA is affected by many factors including polymer composition. m olecular weight, and nature of the incubating media. The biodegradation rat e of PLGA containing higher content of lactic acid moiety is lower than tho se containing a lower content of lactic acid moiety. PLGAs with a higher mo lecular weight, degrade faster than those with a lower molecular weight, i. e. the molecular weight decreases more rapidly for higher molecular weight PLGAs than their lower molecular weight counterparts. Nature or properties of the hydrolysis/incubating media may have an effect on the biodegradation of PLGAs. A basic medium may slow down the biodegradation of PLGA in compa rison with samples in an acidic medium. The rate of pH reduction for the in cubating medium can be divided into three deferent phases, giving an invert ed S-type pH profile for the non-buffered incubating media.