Layered cocktails inspire new male birth control

Pictured: When the layers of the injection are exposed to infrared heat, the contraceptive mixes and dissolves. Source: Ahmad Syahrir (via Pexels)

By Holly Giles

We all know that part of the appeal of a cocktail is the fancy glass, the little umbrella and the coloured layers, but this week scientists in China have used this image as the inspiration for a new male birth control strategy. Currently for men there are only shortterm and long-term contraceptives in the form of condoms and vasectomy respectively. But condoms can fail, and many men are deterred from the alternative by the permanency of surgery.

Lead researcher Professor Xiaolei Wang and his colleagues at Nanchang University wanted to change this; their vision is to provide medium-term, reversible coverage for between 2 and 20 weeks. This comes after the discovery that the long-term use of female birth control pills can increase the likelihood of side effects such as blood clots and breast cancer. The unusual idea behind this new method could be the answer to current contraceptive issues.

Wang’s team performed a series of trials on rats where four consecutive layers were injected into the vas deferens, the duct through which sperm travels from the testicle to the urethra: a hydrogel to form a physical barrier to sperm; gold nanoparticles; EDTA which breaks down the hydrogel and kills sperm; and another layer of gold nanoparticles. This cocktail of chemicals blocks the vas deferens and prevents sperm being released.

Upon exposure to infrared light the layers mix and dissolve, reversing the effect. Data released from the study looks very promising, as a group of rats were allowed to mate for a couple of months after injection and none of them became pregnant. The subjects were then exposed to near-infrared light for a few minutes and allowed to mate for a further few months, when pregnancy rates returned to normal. Now the researchers are scaling up the study to other animals, while hoping to work on humans in the near future.

There are still some concerns about the safety of the approach. It is unknown how long the contraception would last for humans or whether the buildup of blocked sperm would cause inflammation or injury. Also, it is not well understood how the vas deferens would react to the chemicals.

Evidently studies focusing on these potential risks are needed before this kind of injection can become a widespread procedure, but it is a great example of how scientists can be inspired by the world around them. Whether it works or not, it certainly brings a new meaning to the phrase “going out for cocktails”.