Sperm sorter separates good cells from bad

Last updated at 10:33 06 January 2005

A shoebox-sized sperm-sorter could soon allow IVF clinics to screen out damaged cells associated with infertility and childhood cancers, it has been revealed.

The machine, developed in Australia, works on the principle that the most negatively charged sperm have the healthiest DNA.

The sorter simply runs a current across a filter to separate the "good" sperm from the "bad".

In preliminary tests using semen from medical students the sperm selected by the sorter had only half as much DNA damage as the rejected sperm.

Fittest-looking sperm

Mechanised sorting could be especially useful when a would-be father is older, a heavy smoker, or has been exposed to workplace pollution - all risk factors for DNA damage.

IVF clinics currently centrifuge semen to increase the concentration of the densest sperm cells, which tend to be the healthiest.

For certain treatments, IVF technicians also pick out the fittest-looking sperm, such as those with regular, ovoid heads.

But centrifuging takes a long time and neither technique can spot sperm that is free of DNA damage.

The new sorter, developed by John Aitken and Chris Ainsworth at the University of Newcastle in New South Wales, consists of two chambers divided by a polycarbonate filter.

The filter has holes that are five micrometres in diameter, large enough to allow sperm through while blocking other bodies such as white blood cells. These can contaminate semen and damage sperm.

Semen is injected into the first chamber and a voltage applied across the filter for up to five minutes to move more negatively charged sperm into the second chamber.

Picking good sperm

Moira O'Bryan, from the Monash Institute of Reproduction and Development in Melbourne, Australia, told New Scientist magazine: "It is so simple. I've never seen anything like it before.

You turn it on, the sperm move across and there you go.

"Only time will tell, but it might take some of the subjective nature out of picking good sperm."

Sperm chosen by the sorter also happen to look healthier, with the same physical characteristics as those sought by technicians making a visual selection.

The machine's ability to select "good" sperm will be tested in two clinical trials of women undergoing IVF at an Australian fertility clinic later this year.

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