Improvements in the infectivity of cryopreserved third-stage larvae of Angiostrongylus cantonensis using a programmable freezer

A simple and rapid method for cryopreservation of Trichomonas vaginalis

A pellet freezing method, one type of rapid freezing protocol, was established for Trichomonas vaginalis. As cryoprotectants, 5-20% dimethylsulfoxide (DMSO), ethylene glycol, propylene glycol, and glycerol were used. Of these, DMSO showed a high protective effect, with a maximum effect at a concentration of 20%. No effect of equilibration time was recognized with any of the cryoprotectants. Therefore, the optimal condition was deemed 20% DMSO without equilibration. The pellet freezing method was also compared with the conventional slow cooling protocol. The survival rate was 73 +/- 8% with the slow cooling protocol and 48 +/- 4% with the pellet freezing method. The delay in growth with the pellet freezing method was no more than 5.4 h compared with the slow cooling protocol, suggesting its validity as a technique for cryopreservation of T. vaginalis.