Sperm-particle interactions and their prospects for charge mapping

In this article, we demonstrate a procedure to investigate sperm charge distribution by electrostatic sperm-particle interactions. We fabricated and investigated differently charged particles and their attachment distribution on the bovine sperm membrane. We observed the sperm-particle attachment sites using bright field and cryo-scanning electron microscopy combined with energy-dispersive X-ray analysis. Our findings suggest that the charge distribution of the sperm membrane is not uniform and although the overall net charge of the sperm cell is negative, positively charged areas are especially found on the sperm heads. We test the newly developed method to investigate the dynamic charge distribution of the sperm cell membrane upon maturation induced by heparin, as a representation of the multitude of changes during the development of a sperm.