Thesis (M.Sc.)--Chulalongkorn University, 2008

The preparation of controlled release folic acid-loaded ethyl cellulose microcapsules by oil in oil emulsion solvent evaporation was investigated. A mixed solvent system (MSS) consisting of acetone and methanol in a 9:1 ratio was selected as a dispersed phase and light liquid paraffin as a continuous phase. Span 80 was used as an emulsifier for stabilizing the emulsion. The SEM showed that the microcapsules had a spherical shape. The particulate properties and the in vitro release profile depended on the processing and formulation parameters such as concentration of ethyl cellulose, concentration of emulsifier, pore inducer and initial drug feed. The average diameter of microcapsules increased from 300 µm to 448 µm whereas release rate decreased from 52% to 40% as the concentration of ethyl cellulose increased from 2.5% to 7.5%. When the concentration of emulsifier increased from 1% to 4%, the average diameter of microcapsules decreased from 300 µm to 141 µm and release rate increased from 52% to 79%. An addition of small amounts of sucrose, a water-soluble agent, improved the release of drug from the microcapsules matrix without influencing the morphology and particulate properties of microcapsules. The encapsulation efficiency increased from 64% to 88% as the initial drug feed increased from 20 mg to 60 mg.