The 2000s truly have been a time of innovation. Humans have put robots on Mars, rapidly developed vaccines for a raging global pandemic, and brought self-driving and flying cars to the market. Yet, somehow, we still don’t have viable male contraceptives apart from the trusty condom.
Well, researchers from Nantong University, China, are on the noble path to change that. But it really doesn’t sound pleasant.
In new research published in the journal Nano Letters, Ding et al. describe a novel method of male contraception involving the injection of magnetic nanomaterials, which are then helped via magnets to the scrotum, where they induce the particles to rapidly heat up the testes. The induced hyperthermia was enough to temporarily halt sperm production, and even shrink the testes for 30 to 60 days, before reverting back to normal. The research has only been performed in mice so far.
While it sounds pretty terrifying, induced mild hyperthermia does appear to show promise. Even small increases in temperature can decrease sperm count in men, and the researchers hope to leverage this effect to halt spermatogenesis (the production of sperm). Therefore, the magnets gently heat the area to a toasty (but still moderate) 58 °C (104 °F).
However, finding a nanoparticle that is magnetic, injectable, and non-toxic is no easy feat. The researchers leant on existing studies that have used iron oxide nanoparticles, which are degradable in the body and can be guided by magnetic fields to their target. After trying a few different variations, they found citric acid-coated nanoparticles to be the best for the job.
The treatment lasted 15 minutes, involving an alternating magnetic field being applied to the testes of five mice to heat them to the required temperature. Afterwards, the mice were caged with female mice to induce pregnancy before being sacrificed at different time points (seven, 30 and 60 days) to perform analysis. Following treatment, the mice could no longer father any pups for seven days. As time went on, the mice slowly returned to normal fertility levels, with them fathering around 12 pups per pregnancy at day 60.
Of course, the study must be analyzed carefully – the results are in mice, and it is never certain what will translate over to humans. It is also virtually impossible to estimate any pain the mice were in with accuracy, and this has limited male contraceptives in the past. However, it certainly illuminates an interesting line of enquiry, as non-invasive male contraceptives are desperately needed.