Drug delivery systems based on polymer blends: Synthesis, characterization and application

Polymer blending is the physical mixing of two or more existing polymers. It offers an effective way to produce new polymeric materials with combined excellent properties. With this technique, non-toxic, biocompatible hydrogels can be synthesized through mixing biocompatible polymers in the absence of the toxic agents, such as crosslinking agents, initiators and residual monomers, which are inevitable in regular polymerization processes. In this regard, this project focuses on the development of new drug delivery systems based upon blending of polymers with known biocompatibility. The first part of the project was to synthesize hydrogels from blending of two hydrophilic polymers-polyvinyl alcohol (PVA) and polyvinyl pyrrolidone (PVP). The hydrogel characteristics and model drug release were evaluated. The second part of the research was to incorporate biodegradable poly (D, L-lactide-co-glycolide) microparticles (∼10μm) containing a model drug into hydrogel matrices of PVA, with the crystallites of PVA serving as the crosslinking points. The release of the drug formulated in the polymeric composite was controlled by the degradation of the microparticles and the diffusion through the hydrogel matrix. Furthermore, a multilayer approach was adopted to reduce the initial burst effect by offering additional diffusion barriers. An empirical model of drug release from the multilayer composite was developed and applied to estimate the effects of outer layer thickness and particle size on the release from the delivery system.