New spermicides stop cells gently

A promising new class of spermicides has the potential to perform better, and with fewer drawbacks, than those available today.

 Researchers at the Wayne Hughes Institute in Roseville, Minn., have found that in test-tube experiments, organic vanadium compounds inactivate sperm more quickly than the common spermicide nonoxynol-9. "A 15-second exposure will knock [sperm] out completely," says Osmond J. D'Cruz. Moreover, the compounds work at lower concentrations and may avoid the problems that currently accompany repeated spermicide use.

 Spermicides such as nonoxynol-9 are "basically detergents," says D'Cruz. They immobilize sperm by washing away their outer membranes. However, these spermicides also destroy the membranes of other cells, thus damaging the lining of the vagina. Nonoxynol-9 kills beneficial bacteria in the vagina, allowing bacteria that cause urinary tract infections to thrive.

 The vanadium compounds, on the other hand, stop sperm by shutting down the motors that turn their whiplike tails. Using a microscope, the researchers could see that the compounds leave a sperm's outer membranes undisturbed, suggesting that they won't disrupt other cell membranes either, says D'Cruz. He and his colleagues Phalguni Ghosh and Fatih M. Uckun report their findings in the June Biology of Reproduction.

 The team discovered vanadium's spermicidal properties while searching for alternatives to a platinum-based drug used to treat testicular cancer. Knowing that the drug interferes with sperm production, D'Cruz and his colleagues decided to investigate the spermicidal properties of various organic metal compounds. They found that compounds containing titanium, zirconium, molybdenum, or hafnium did not inactivate sperm, but 12 vanadium compounds did.

 The team is now testing vanadium compounds in animals. Henry Gabelnick of the Contraceptive Research and Development Program in Arlington, Va., points out that many spermicides are now being developed, including some that show antimicrobial action.