Are Motorized 'Spermbots' the Answer to Male Infertility?

sperm in microhelices
An enhanced look at the sperm wrapped in their tiny Slinky-like polymer microhelices that will propel them toward their goal. American Chemical Society/HowStuffWorks


For couples who are having difficulty conceiving, one of the common hindrances is something called low or poor sperm motility, which is the fancy medical way of saying that a man's sperm cells aren't so great at swimming. That may not sound like a big deal — after all, we can't all be Michael Phelps, right? — but swimming happens to be a skill the little fellas have to excel, in order to travel up into a woman's body, reach and penetrate an egg. If less than 40 percent of a man's sperm are able to move forward in a straight line, his chances of becoming a proud papa drop greatly.

There are a number of different causes for having laggardly sperm, from pituitary gland disorders to testicular disease. And according to the Mayo Clinic website, the ability of sperm to move as well as the proportion of normally motile sperm tend to decrease with age. That's a worrisome problem for men who've put off starting a family. Couples can get around it by using in-vitro fertilization, in which eggs are removed, artificially fertilized and re-implanted, but that's an expensive procedure that doesn't always work.

Now, a team of German scientists has come up with an ingenious way to give those sluggish sperm a boost, though it's one that sounds a little like an outlandish gadget dreamed up by Professor Farnsworth in the TV comedy "Futurama." They want to create cyborg sperm — "spermbots," as they call them — by equipping the cells with tiny remote-controlled motorized vehicles to propel them on their reproductive mission.

The researchers from IFW Dresden and Chemnitz University of Technology describe their invention in a recent article in the journal Nano Letters titled "Cellular Cargo Delivery: Toward Assisted Fertilization by Sperm-Carrying Micromotors."

Building on previous researchers' efforts to build cell-sized motors, the researchers' first step was to fashion a bunch of metal-coated polymer microhelices — imagine really, really tiny Slinky toys — whose movement can be controlled by a magnetic field. Once the scientists had the gear ready, they took a sample of semen and identified the sperm who were weak swimmers.

In the process, they weeded out the ones with genetic defects, so that those cells that remained all were capable of fertilizing an egg, if only they could get to it.

After that, they guided the Slinky-like gadgets to lasso the sperm cells. When a sperm slipped inside one, its tail was captured inside the helix, while a noose-like ring at the other end fastened around the sperm's head, preventing it from slipping inside. The spermbots then were directed to swim to an egg and release the sperm.

Here's a video showing the spermbots' performance.

While the researchers have demonstrated in the lab that sperm can be hooked up to motors and transported without fatal damage, they caution that there's still a lot of work to be done before the technology is ready for use by prospective parents.

As the Nano Letters article notes, the tricked-out sperm actually swim more slowly than they naturally would, and the sperm cells have a tendency to get stuck in the helices when it's time to release them. And it's not clear yet what it might cost to use spermbots. But the invention is still in its early stages. "We will strive to find more efficient approaches in future works," the researchers wrote.