Application of microencapsulation for toxicology studies. I. Principles and stabilization of trichloroethylene in gelatin-sorbitol microcapsules.

Microencapsulation is an innovative, alternative means of incorporating volatile, reactive, and/or unpalatable chemicals into animal feed for toxicologic studies. For such usage, the materials in the microcapsule shell must not adversely affect the laboratory animals, and the encapsulation process must not alter the chemical under study. Trichloroethylene (TCE), a volatile chemical identified in drinking water, was encapsulated in gelatin-sorbitol microcapsules. The concentration of TCE ranged from 40 to 43% (w/w) and most particles (approximately 85%) were between 300 and 420 micron in diameter. Under optimum storage conditions, loss of TCE from the microcapsules was less than 1% per month. Less than 2% of the TCE was lost from microcapsules held in uncovered petri dishes at ambient temperature and humidity for 14 days. Microencapsulated TCE was mixed with NIH-07 rodent feed at a level of 50 mg microcapsules/g feed (equivalent to 20.6 mg TCE/g feed) and stored at room temperature for 7 days in an open container or for 21 days in a sealed container. There was no detectable loss of TCE from the feed blends stored under these conditions. Thus, the stability of TCE in gelatin-sorbitol microcapsules is adequate for dosed-feed toxicity studies of this chemical.