PREPARATION AND DRUG RELEASE BEHAVIORS OF pH-SENSITIVE MICROCAPSULES

The pH-sensitive microcapsules were prepared by interfacial polymerization, in which caffeine was used as a model drug and hyperbranched poly L-lysine (HBPL) and terephthaloyl chloride as wall-forming materials. The microcapsules were characterized by Malvern particle size analysis, scanning electron microscopy, Fourier transform infrared spectrophotometry (FTIR) and UV-vis spectrophotometer. Triton X-100 was used as the emulsifier of interfacial polymerization. The effects of the emulsifier content on the particle size distribution, loading content, encapsulation efficiency and drug release property of microcapsules were discussed in detail. The release behaviours of caffeine in different phosphate buffered saline (PBS) pH were investigated systematically. The FTIR analysis of caffeine-containing microcapsules demonstrated that caffeine was successfully encapsulated in the wall-forming materials. The resultant microcapsules had narrower particle size distribution, smoother surface, and higher drug release amount with the percentage weight of emulsifier being 1.5 wt%. The drug-release behavior of caffeine from microcapsules was evaluated as a function of pH. More than 87.1% caffeine was released into pH 7.6 PBS after 100 min, whereas only 37.0% caffeine was diffused out in pH 2.2 PBS over the same time interval. The results indicated that these drug-loaded microcapsules have shown sensitivity to pH value