Isolation of spermatozoa in vaginal contents by centrifugation in a colloidal silica gradient.

Human spermatozoa were separated from vaginal contents with epithelial cells by density gradient centrifugation in colloidal silica coated with polyvinylpyrrolidone. In this procedure spermatozoa were collected at a density range of 1.130 - 1.142 g/ml by centrifugation at 35 000 g for 1 h.