Synthesis, characterization, biodegradation, and drug delivery application of biodegradable lactic/glycolic acid oligomers: Part II. Biodegradation and drug delivery application.

Previously synthesized lactic/glycolic acid (PLGA) oligomers with different compositions (i.e. different ratio of lactic to glycolic acid in the oligomers) were further studied regarding their biodegradation and drug delivery application. The PLGA oligomers have fast biodegradation characteristics. They degrade to water soluble substances, i.e. lactic and glycolic acids, at a rate of 31.43-40.68 mg day-1 in a medium of constant pH and 28.04-37.87 mg day-1 in a medium of non-constant pH. The biodegradation rate is affected by the composition of the PLGA oligomers and the pH of the incubating medium. The higher the content of glycolic acid moiety in the oligomer, the faster the biodegradation rate. The lower the pH of the incubating medium, the slower the biodegradation of PLGA oligomers. A sustained-release drug delivery system based on the PLGA oligomers was fabricated as injectable microgranules by thermal blending of the PLGA oligomers and drug. Aspirin was used as a model drug. The oligomeric microgranules have advantages of easy fabrication, high drug loading efficiency, easy administration, and fast biodegradation. This thermal blending preparation method has a high loading efficiency of more than 90%. The PLGA oligomeric microgranules can release drug from 9 to 13 days depending on the oligomer composition. Both drug release rate and release duration are influenced by composition of the oligomers. The PLGA oligomeric matrix has the capability of protecting aspirin from hydrolysis. The lactic/glycolic acid oligomeric microgranules have potential use for sustained-release drug delivery.