Using Nanotechnology to Warm Testicles Can Work as a Male Contraception Alternative

Woman contraceptive methods are common and vary to suit different needs. As for men, the options are limited to two common methods - condoms and vasectomies.

Due to several drawbacks, the attempt to find alternative male contraceptive options are explored, in which one among others currently being investigated is nanocontraception - deploying metallic nanoparticles to the testicles where they are heated.

As a result, sperm production and fertility becomes less, like an on and off switch as they get warmer. Nonetheless, the testicles can be irreversibly destroyed if they become too warm as the tissue dies and can no longer produce sperm, even when returned to normal temperature.

This delicate process includes long nanorods (or nanocylinders) of gold atoms coated with a few long polymer chains on their surface, like oblong bacteria with hairs sticking out - first studied in 2013 on mice by biologist Fei Sun and his multidisciplinary research team.

A new method using magnetic nanoparticles

Sun and his team published their latest findings in July 2021, concerning a new method composed of magnetic iron oxide instead of gold coated with citric acid instead of ethylene glycol, but have the same size and shape as the earlier nanorods.

The injection of magnetic nanoparticles - followed by magnetic targeting - was performed daily on mice for one to four days. The more days it had been injected, the hotter its testicles became. In some cases, fertility was completely eliminated, but showed gradual recovery after 60 days.

Sun and his colleagues found that unlike the gold nanorods, the iron nanorods were gradually eliminated into the liver and spleen, and later fully eliminated from the body, reducing the risk for long-term toxicity.

According to Sun, nanocontraception is ready to be used on household pets. In fact, it is already being used on cats in China.

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Nanocontraception reversibility

According to David Powell, nanocontraception might be of greater interest in Europe where surgical castration is less popular. Even zoos consider nanocontraception as part of their "reproductive toolkit".

With this provided, Sun's ultimate long-term goal is applying this method to humans, especially with its one potential advantage - reversibility - although he admits that possibility is still a long way off (but should work in theory).

However, determination of just how reversible it is needs further study, as all of Sun's experiments only injected mice once and were never subjected to a second injection of nanoparticles after their testicles had healed. Detailed studies are required to assure that nanocontraception is not toxic for men, especially in large quantities.

Unlike in mice, it is more difficult to put a man under anesthesia for four hours and wrap an electric coil around his testicle. As an alternative, the researchers hope to be able to deliver the magnetic nanorods orally and direct them to the testicles. In addition, it is uncertain how many men will be comfortable with shrunken testicles, even if the original size recovers with time.

Until then, men could only rely to better quality condoms or surgical procedures.

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