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How to trap sperm

Partial-protein coating lets microscopic beads mimic unfertilized eggs

8:39am, May 12, 2016

BOUND  Mouse sperm (left, red) flock to a polymer bead coated with the sperm-binding sections of a protein found around unfertilized eggs (illustration, right). Such beads could someday be used as contraceptives or a method for identifying healthy sperm, researchers report. 

New sperm-catching beads could someday help prevent pregnancy — or enable it.

Researchers created microscopic polymer beads that mimic unfertilized eggs and trap passing sperm. The beads are coated in the sperm-binding section of a protein called ZP2. In mammals, ZP2 is found in membranes around unfertilized eggs; sperm must bind to the protein before entering the egg.

The beads could be used as short-term contraceptives, Jurrien Dean of the National Institutes of Health in Bethesda, Md., and colleagues report in the April 27 Science Translational Medicine. In the laboratory, human sperm attached to the beads within five minutes. The researchers then mixed 100,000 human sperm with 1.5 million beads and 28 mouse eggs containing human ZP2 proteins. After 16 hours, only one sperm reached an egg.

In another experiment, beads coated with mouse ZP2 delayed pregnancy when injected into the

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