Cryopreservation of spermatozoa in alginic acid capsules

Objective To develop a method of freezing small amounts of spermatozoa in polymerized alginic acid drops, which can be liquified after thawing for recovery of the spermatozoa. Design Prospective clinical study. Setting Medical School, RWTH Aachen, Aachen Germany. Patient(s) None. Intervention(s) Validation of the encapsulation method with bovine sperm; cryopreservation of human spermatozoa in alginic capsules. Main Outcome Measure(s) We optimized the cryopreservation method by testing different parameters influencing the freezing procedure, such as concentration of alginic acid, size of drops, time of polymerization, and culture media. Result(s) The final protocol was as follows: encapsulation by 7.3 mg/mL alginic acid forming 10-μL drops polymerized for 30 seconds and liquefied for 2.5 minutes in sodium citrate. Cryopreservation of human spermatozoa by this protocol resulted in a decreased motility of 18.3% compared with standard protocols but a 19.9% higher vitality of the immotile spermatozoa. Conclusion(s) No difference in viability of spermatozoa after both sperm-freezing procedures could be observed. Further investigation will be undertaken to reduce the amount of immotile but viable sperm after microencapsulation in alginic acid.