Some men produce sperm that are poor swimmers, a major cause of infertility. To help, researchers from Germany have developed motorised cyborg "spermbots" that can be guided directly to an egg. This isn't the first time that scientists have fooled around with sperm. Back in 2013, a team led by Oliver G. Schmidt positioned bull sperm inside of tiny metal cylinders which could then be steered with magnets. The point of all this was to create a new class of manoeuvrable microscopic machines with "fascinating future applications". Unfortunately this model, in which the sperm-flagella is completely encased, did not lend itself well to sperm's primary application: fertilising an egg.
Building on this previous work, Schmidt's team at Germany's Institute for Integrative Nanosciences at IFW Dresden has now developed a "cellular cargo delivery" system. To give sperm with low motility an added boost, tiny metal helices are fitted around their tails. Like the team's other robosperm, these cells can be controlled by a rotating magnetic field. The details for how it works can now been found in the latest issue of Nano Letters.
The opening line of the paper's abstract describes the system nicely.
We present artificially motorised sperm cells — a novel type of hybrid micromotor, where customised microhelices serve as motors for transporting sperm cells with motion deficiencies to help them carry out their natural function.
Looking at the contraption, it looks as though a strand of DNA was wrapped around the tail of the sperm. In actuality, it's a metal-coated polymer that can be spun around and propelled forward with a rotating magnetic field. When the helix moves forward, so does its passenger. By changing the orientation of the field, the researchers can guide a cyborg sperm in three dimensions to its intended destination.
In a demonstration, Schmidt's team managed to capture, transport and release a single "immotile" live sperm cell in a fluidic bath, an environment that closely resembles an actual physiological system. It's all still in the early stages of development, so we're not even close to seeing clinical trials.
"Despite the fact that there still remain some challenges on the way to achieve successful fertilization with artificially motorised sperms, we believe that the potential of this novel approach toward assisted reproduction can be already put into perspective with the present work," the researchers conclude.
All images: M. Medina Sanchez et al., 2016/Nano Letters.