Cryopreservation of a small number of human sperm using enzymatically fabricated, hollow hyaluronan microcapsules handled by conventional ICSI procedures

Purpose We investigated whether enzymatically fabricated hyaluronan (HA) microcapsules were feasible for use in the cryopreservation of a small number of sperm. Methods HA microcapsules were fabricated using a system of water-immiscible fluid under laminar flow. Three sperm were injected into a hollow HA microcapsule using a micromanipulator. Capsules containing injected sperm were incubated in a freezing medium composed of sucrose as the cryoprotectant and then placed in a Cryotop® device and plunged into liquid nitrogen. After thawing, the capsule was degraded by hyaluronidase, and the recovery rate of sperm and their motility were investigated. Results The HA microcapsule measuring 200 μm in diameter and with a 30-μm thick membrane was handled using a conventional intracytoplasmic sperm injection (ICSI) system, and the procedure involved the injection of sperm into the capsule. The HA microcapsules containing sperm were cryopreserved in a Cryotop® device and decomposed by the addition of hyaluronidase. The recovery rate of sperm after cryopreservation and degradation of HA microcapsules was sufficient for use in clinical practice (90 %). Conclusions Hollow HA microcapsules can be used for the cryopreservation of a small number of sperm without producing adverse effects on sperm quality.