Technology and applications for encapsulated spermatozoa.

A technique for microencapsulation of bovine spermatozoa has been developed with minimal spermatozoal injury and thus, a potential use in artificial insemination (AI). Membranes made of the following polymers have proven best: poly-l-lysine, polyarginine, polyvinylamine, and protamine sulfate. Successful encapsulation has been achieved for capsules ranging in size from 0.75 to 1.5 mm, and sperm concentrations from 45 to 180 x 10(6) cells/ml. Successful buffers include Cornell University Extender and egg yolk citrate - glycerol (maximum 10% v/v egg yolk for normal capsular shape). Capsule fragility (ability to rupture under aging and physical stress) was negatively related to membrane thickness which ranges from 1.92 microm to 5.32 microm (controlled by polymer concentration, molecular weight, and exposure time) and positively to concentration of sperm encapsulated. On delivery to the porcine reproductive tract, the capsule constructed of poly-l-lysine membranes ruptured between 12 and 24 hr after insemination. Heterospermic studies have shown that encapsulated sperm are capable of fertilization in vivo, but are at a disadvantage to unencapsulated sperm when AI is at conventional times following detection of estrus.