Propylene Oxide and Ethanol are commonly used dehydrating solvents for processing tissues for electron microscopy. But both solvents, however, have some undesirable properties: they are highly flammable, volatile, toxic and potentially carcinogenic.
Acetonitrile is a direct substitute for ethanol and propylene oxide; furthermore, it is safer to use and requires shorter dehydration times. It is freely miscible with water, alcohol, acetone and epoxy resin and it does not interfere with epoxy polymerization.
Acetonitrile is not mutagenic in bacterial and animal cells and has not been found to be a carcinogen in humans. Acetonitrile is slightly toxic by acute exposure through oral intake, skin contact, and inhalation. However, acetonitrile can be converted by the body to cyanide. Symptoms of exposure include weakness, flushing, headache, difficult and/or rapid breathing, nausea, vomiting, diarrhea, blue-gray discoloration of the skin and lips (due to a lack of oxygen), stupor, and loss of consciousness.
Harold H. Edwards, Yu-Yan Yeh, Betty I. Tarnowsky, and Gregory R. Schonbaum. (1992). Acetonitrile as a Substitute for Ethanol/ Propylene Oxide in Tissue Processing for Transmission Electron Microscopy: Comparison of Fine Structure and Lipid Solubility in Mouse Liver, Kidney, and Intestine. Microsc. Res. and Technique Vol 21, pg.39-50.