Jalil R, Nixon J R
Chelsea Department of Pharmacy, King's College London, UK.
J Microencapsul. 1990 Jan-Mar;7(1):25-39. doi: 10.3109/02652049009028421.
Poly (L-lactic acid) [L-PLA] microcapsules containing phenobarbitone were prepared from a w/o emulsion system, using light liquid paraffin as the continuum and a solution of phenobarbitone and L-PLA in acetonitrile as the disperse phase. Increasing stirring rate and emulsifying agent concentration were found to reduce microcapsule size. Spans (sorbitan esters of fatty acids) and Brijs (polyoxy ethylene ethers of fatty acids) with different physicochemical properties have been found to produce microcapsules of differing size. An attempt has been made to correlate emulsifier properties and the corresponding microcapsule size. It was found that the emulsifiers had little or no effect on the interfacial tension between light liquid paraffin and acetonitrile and there was no correlation between HLB of the emulsifiers and the resulting microcapsule size. It was postulated that microcapsule size would be affected by the packing of the emulsifier at the interface which would depend on the structure of the emulsifier. Closer, more uniform packing by the straight chain saturated fatty acid containing emulsifiers produced smaller microcapsules than when lose packing, which existed when emulsifiers containing either three fatty acid chains or a 'V' shaped cis-double bond containing fatty acid chain, were used. Microcapsule size was found to increase rapidly with an increase in polymer concentration, if this polymer concentration was increased in conjunction with an increase in the total solid content of the dispersed phase. Increases in polymer concentration by reducing the quantity of solvent for the dispersed phase caused little increase in mean microcapsule size. The phenobarbitone content in the microcapsules was not affected significantly by variations in the preparative parameters.
采用油包水乳液体系，以轻质液体石蜡为连续相，以苯巴比妥和聚（L-乳酸）[L-PLA]在乙腈中的溶液为分散相，制备了含苯巴比妥的聚（L-乳酸）[L-PLA]微胶囊。研究发现，提高搅拌速率和乳化剂浓度可减小微胶囊尺寸。已发现具有不同物理化学性质的司盘（脂肪酸山梨醇酯）和吐温（脂肪酸聚氧乙烯醚）可产生不同尺寸的微胶囊。已尝试将乳化剂性质与相应的微胶囊尺寸相关联。结果发现，乳化剂对轻质液体石蜡和乙腈之间的界面张力几乎没有影响，乳化剂的亲水亲油平衡值（HLB）与所得微胶囊尺寸之间也没有相关性。据推测，微胶囊尺寸将受乳化剂在界面处的堆积情况影响，而这取决于乳化剂的结构。与含三条脂肪酸链或含“V”形顺式双键脂肪酸链的乳化剂使用时存在的松散堆积相比，含直链饱和脂肪酸的乳化剂更紧密、更均匀的堆积产生的微胶囊尺寸更小。如果聚合物浓度与分散相总固体含量的增加同时增加，则发现微胶囊尺寸会随着聚合物浓度的增加而迅速增大。通过减少分散相溶剂的量来提高聚合物浓度，对平均微胶囊尺寸的增加影响不大。微胶囊中苯巴比妥的含量不受制备参数变化的显著影响。
