Gao Y T, Wang B H
Military Medical Research Institute of Mei Fen, Fuchow.
J Microencapsul. 1989 Oct-Dec;6(4):527-33. doi: 10.3109/02652048909031172.
Four kinds of microencapsulated insecticides were prepared with fenthion, mevinphos, acetofenate and methylparathion. From observations made after the experiment it was found that type II microcapsules with polyurea capsule walls formed by interfacial polymerization had a special advantage: they had greatly enhanced safety in mice when administered via mouth, respiratory tract and skin. Type I microcapsules, with capsular walls of gelatin and Arabic gum formed through complex condensation, had no safety protection with oral administration. The mechanism of safety enhancement associated with type II microcapsules depends mainly on maintenance of microcapsule integrity within the digestive tract; type II microcapsules rarely disintegrated in the gastrointestinal tract and only about 5 per cent were ruptured. Of the small quantity of insecticide that leaked through the ruptured capsule walls, the amount absorbed by the digestive tract was not sufficient to kill the mice before the microcapsules were discharged in faeces--The amount of discharge within 48 hours exceeded 80 per cent. Administration of large numbers of microcapsules was necessary before sufficient insecticide could be absorbed by the digestive tract to cause lethal dosage; on post-mortem examination some microcapsules were found intact in the stomach and small intestine. Type I microcapsules, however, were totally disintegrated in the digestive tract and no traces could be found in the faeces; therefore their drug safety could not be increased.
用倍硫磷、速灭磷、苯氧威和甲基对硫磷制备了四种微囊化杀虫剂。实验后的观察发现，通过界面聚合法形成聚脲囊壁的II型微囊具有特殊优势：经口、呼吸道和皮肤给药时，它们在小鼠体内的安全性大大提高。通过复合凝聚形成明胶和阿拉伯胶囊壁的I型微囊，口服时没有安全保护作用。与II型微囊相关的安全性提高机制主要取决于微囊在消化道内的完整性维持；II型微囊在胃肠道中很少崩解，只有约5%会破裂。通过破裂的囊壁泄漏的少量杀虫剂，在微囊随粪便排出之前，消化道吸收的量不足以杀死小鼠——48小时内排出量超过80%。在消化道吸收足够的杀虫剂导致致死剂量之前，必须施用大量微囊；尸检时发现胃和小肠中有一些微囊完好无损。然而，I型微囊在消化道中完全崩解，粪便中找不到任何痕迹；因此它们的药物安全性无法提高。
