Characterization of biodegradable polymeric microparticles for controlled release

Well-defined release of molecules is of great interest to researchers in many fields, especially in the pharmaceutical industry. Biodegradable polymeric microparticles are an especially attractive means of introducing drugs to the body in controlled release formulations. Although many previous studies have considered polymeric microspheres and core-shell microcapsules for their applications to drug delivery, several aspects make the work shown here unique. First, precision particle fabrication technology generates uniformly sized microparticles, allowing precise control of microcapsule shell thicknesses. The fabrication technique also can be manipulated to selectively locate polymers to the core or shell of microcapsules based on thermodynamic and kinetic considerations of the particular polymer-polymer system.; Using a series of characterization techniques, the effects of various solvents on the formation of core-shell microcapsule structures were evaluated. Thermodynamic predictions of polymer-polymer immiscibility and spreading within the microcapsule system matched experimental results well. Using a faster extracting shell solvent resulted in better core entrapment and higher drug loadings.; Core-shell microcapsules with a surface eroding biodegradable polymeric shell are a promising future route for protection of fragile therapeutics. A delay is seen in polyester core degradation due to the presence of a polyanhydride shell, but imaging, bond breakage and molecular weight analysis indicate that water has reached the core as early five weeks after beginning incubation. However, the ability to fabricate such devices with controlled polymer location and precise shell thicknesses is a major advance.; The core-shell or reservoir-type microcapsules resulting from precision particle fabrication methods are of a uniform size that allow specific probing of the effect of well-defined shell thicknesses. The use of a slowly eroding shell has the ability to delay the release of drug, with complete release being achieved almost 3 weeks later than with pure microspheres. Combining microcapsules of different shell thicknesses allows the generation of complex release profiles, such as constant release.; The formation of microcapsules is a complex process relying on thermodynamic, kinetic and other factors such as the physical drug. Continued study in the microparticle arena will help achieve better control of release and allow for application of more potent therapeutics.