For decades male contraception has been limited to short-term methods like condoms or more permanent solutions like vasectomies, but there aren't really any options between those two extremes. In the hunt for a useful middle-ground, researchers from Nanchang University have developed a new method that so far seems to be relatively long-lasting, effective and reversible.

The new method involves injecting four layers of materials into the vas deferens, the tube that sperm passes through on its way from the testicles to the urethra. Those layers are added in a specific order: first there's a calcium alginate hydrogel, then some gold nanoparticles, then ethylenediaminetetraacetic acid (EDTA), and finally a second layer of gold nanoparticles.

Each of those layers has a purpose. The hydrogel is there as a physical barrier to the sperm, preventing them from escaping during ejaculation, while the EDTA can also kill sperm as a secondary contraceptive effect.

When it comes time to reverse the procedure, doctors can apply near-infrared light to the area, which heats up the gold and causes the layers to mix. The EDTA breaks down the hydrogel, and the mixture can then be easily flushed from the patient.

Strangely enough, the team says the method was inspired by cocktails – specifically, the kind that are made by layering different ingredients so they stay separate, before mixing together on demand when stirred or heated up.

The Nanchang team tested the method on rats, and found that it kept the males from impregnating females for more than two months. The procedure was easily reversed in a matter of minutes using a near-infrared lamp, and afterwards the animals were fertile enough to produce offspring.

As is usually the case with animal studies, there's no guarantee this will work on humans, and the team says more work will be needed to ensure the materials and methods are safe. But that's not the only thing that might sink the procedure – other male contraceptives are in the works that could be simpler and safer.

Vasalgel, which works in a similar way by blocking the vas deferens, is further along in development than the layered method. Less invasive techniques might also work, including ultrasound pulses that kill off sperm, while contraceptive pills and topical gels are already in Phase 2 human trials.

With so many potential options on the way, methods like this could face some stiff competition. But maybe they'll fill a specific niche – after all, they could become the male equivalent of the IUD, as a medium-term solution that means you don't need to remember to take a pill every day, and can be easily reversed when you want to start trying for kids.

The research was published in the journal ACS Nano.

Source: ACS Nano

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