Poly(d,l-lactide-co-glycolide) encapsulated poly(vinyl alcohol) hydrogel as a drug delivery system

Purpose. The efficiency of encapsulation of water-soluble drugs in biodegradable polymer is often low and occasionally these microcapsules are associated with high burst effect. The primary objective of this study is to develop a novel microencapsulation technique with high efficiency of encapsulation and low burst effect. Method. Pentamidine was used as a model drug in this study. Pentamidine/polyvinyl alcohol (PVA) hydrogel was prepared by freeze-thaw technique. Pentamidine loaded hydrogel was later microencapsulated in poly( lactide-co-glycolide) (PLGA) using solvent evaporation technique. The microcapsules were evaluated for the efficiency of encapsulation, particle size, surface morphology, thermal characteristic, and drug release. Results. Scanning Electron Microscope (SEM) studies revealed that the microcapsules were porous. The microcapsules were uniform in size and shape with the median size of the microcapsules ranging between 27 and 94 mum. The samples containing 10% PLGA showed nearly three times increase in drug loading (18-53%) by increasing the hydrogel content from 0-6%. The overall drug release from the microencapsulated hydrogel, containing 3% and 6% PVA, respectively, was significantly lower than the control batches. Conclusions. The use of a crosslinked hydrogel such as PVA can significantly increase the drug loading of highly water-soluble drugs. In addition, incorporation of the PVA hydrogel significantly reduced the burst effect and overall dissolution of pentamidine.