A novel technique for chitosan microparticle preparation using a water/silicone emulsion: green tea model

Many effective methods such as spray drying, coacervation, ionic gelation, solvent evaporation and sieving have been suggested for entrapping bioactive compounds into micro- or nanoparticles. However, those methods still have some limitations owing to high temperature requirement, difficulty in particle harvesting or low entrapment for uncharged molecules. In this study, a novel chitosan microparticle preparation method was developed using water-in-silicone emulsion technique with green tea extract as a model active compound. Chitosan microparticles of diameter <5 μm were obtained from 2% chitosan solution with tripolyphosphate (TPP) solution as the hardening agent. The size and properties of the particles appeared to depend on several parameters such as TPP, emulsifier concentrations and pH. High concentration of emulsifier led to low encapsulation and particle aggregation. Entrapment efficiency of chitosan microparticles was improved with lower pH of the tripolyphosphate solution [59.94 ± 3.97 of epigallocatechin gallate (EGCG)] while slowing release of catechins. Epigallocatechin and epicatechin were released almost completely within 2 h under acidic condition whereas EGCG and epicatechin gallate were slowly released. In neutral condition, release of catechins depended on their molecular stabilities. The stabilities of catechins loaded in chitosan microparticles were varied under various temperatures. The degradation of tea catechins increased with temperature. However, the degradation of tea catechins loaded in chitosan microparticles was less than that of free catechins. Thus, the new technique for preparing chitosan microparticles containing heat-sensitive water soluble green tea extract was successfully developed. The technique is suitable for micro-encapsulation of hydrophilic compounds into chitosan microparticles with the ease of harvesting technique.