Mouse and human sperm bind to specially designed polymer beads, which could one day be used to select sperm for fertility treatments or to block conception.
Mammalian sperm binds to the ZP2 protein, part of a matrix that surrounds the egg. Jurrien Dean at the National Institute of Diabetes and Digestive and Kidney Diseases in Bethesda, Maryland, and his colleagues attached an engineered portion of ZP2 to the beads, and found that they captured mouse sperm in lab dishes, preventing fertilization of most eggs in the dish. When beads were placed in mouse uteruses, animals gave birth to pups after about 70 days, whereas females with no beads did so after roughly 28 days.
The beads also selected for human sperm in a dish, and, once released, the sperm could bind to and penetrate eggs better than sperm that were not initially captured by the beads.