Abstract: A procedure for cryopreservation and efficient post-thaw recovery of a single or few cells, preferably human spermatozoa, their precursor cells or blastomeres, which is achieved by injecting cells into cell-free mammalian zonae pellucidae. The cells may also be of any other type where there are provided a relatively small number of valuable cells which must be retrieved. The zona pellucida may be cryopreserved with the cells contained therein. The method involves a combination of physical micromanipulation procedures and cryoprotectant mediated cryopropreservation. The zonae may be tracked by positioning them into straws between two small air bubbles prior to preservation. There is a high recovery of zonae and sperm within the zonae, and a high fertilization rate of the sperm using ICSI after recovery.

Abstract: A cell culture medium and cryopreservation medium in which sodium chloride is replaced with an organic cation, preferably choline chloride in a concentration of at least 100 mM, resulting a residual sodium ion concentration less than about 50 mM. The cryopreservation solution is suitable for cryopreservation of unfertilized oocytes, with thawed oocytes demonstrating the ability to survive, fertilize, and for the resulting embryos to proceed to full term development.