Kill the sperm, spare the irritation
- Kill the sperm, spare the irritation
- 06 March 2007
- From New Scientist Print Edition. Subscribe and get 4 free issues.
Two new molecules kill sperm 25 times more effectively than the most commonly used spermicide, without irritating vaginal cells.
Nonoxynol-9 (N9) is the active ingredient in most spermicidal creams and is sometimes used to lubricate condoms. It is a detergent that kills almost all living cells by destroying their fatty membranes - in the same way that household detergent breaks up grease.
While this kills sperm, it also wipes out some of the normal vaginal bacteria that help prevent bladder and yeast infections. N9 can also irritate cells in the cervix and vaginal wall in some women, leaving them more susceptible to sexually transmitted diseases such as HIV and gonorrhoea.
Now a team led by Gopal Gupta at the Central Drug Research Institute in Lucknow, India, has created two molecules that specifically target sperm by binding to molecules on the sperm membranes which trigger programmed cell death. "Our molecules don't rip open the membrane to exert their action," says Gupta.
In tests on human sperm, the spermicides killed 100 per cent of the sperm at just 4 per cent of the concentration needed to get the same results with N9. The molecules were also non-toxic to cultures of human cervical cells and bacteria commonly found in the vagina (Human Reproduction, vol 22, p 708).