A sterile leakproof plastic vial for cell cryopreservation in liquid nitrogen: Application to parasitic protozoa

Polyethylene bulbs derived from sterile transfer pipets were evaluated as leak-proof vials for cryopreservation of parasitic protozoa. The bulbs were easily frozen and stored in conventional liquid nitrogen refrigeration equipment and were less expensive and safer to handle than plastic screw-capped cryovials. The easily testable heat seal of the polyethylene bulb never failed during longterm immersion in liquid nitrogen, and dispensing of thawed material was simple and safe. Good survival of L. donovani (80%), T. rhodesiense (95%), and C. fasciculata (95%) was obtained after cryopreservation in polyethylene bulbs or plastic screw-capped vials. The polyethylene bulb was considered an excellent container for the safe cryopreservation of pathogens and other biological material.