Just Keep Swimming! Speedy Sperm Tails Boost Nanobiotechnology

The study of nanoparticles acquiring biological functions has had a significant step forward through an unlikely source: sperm tails. Specifically, the enzymes that propel sperm tails.

Researchers at Cornell's Baker Institute for Animal Health have released a study in the Angewandte Chemie on how sperm tail enzymes turn sugar into lactate and energy so quickly that sperm can speed along at five body lengths per second. As a result, they were able to produce a 10-step biological pathway with all the enzymes tethered to nanoparticles. Given their composition, enzymes could produce a final product more efficiently if they are grouped in one place and pass the raw material from enzyme to enzyme just like in an assembly line.

"Sperm have a highly efficient energy-producing system," said the study's lead author, Chinatsu Mukai. A postdoctoral research associate in the Baker Institute laboratory of Alex Travis, Mukai and his colleagues had been doing research on metabolism and sperm function. Travis, who is associate professor of reproductive biology, had the idea to recreate the way sperm tail enzymes were attached to a solid support in to replicate the same sort of effectiveness on small human-made electronics.

In sperm, the enzymes that carry out glycolysis, or the process of turning sugar into energy, have special regions that attach the enzymes to a solid protein scaffold. This lies just underneath the membrane covering the cell and runs most of the length of the tail. In the system developed by Mukai and Travis, the sugar molecule is processed from start to finish by enzymes attached to nanoparticles.

"Sugar comes in through the membrane, hits the enzymes immediately underneath, and then is processed and passed down the line, giving energy production in a high-throughput fashion," explained Travis. If the work can be enhanced to be a net producer of energy, Travis acknowledges that there could be quite a few practical applications. While sperm uses energy to swim and to receive the signal to fertilize an egg, nanobiotechnology uses the energy to power devices that perform a myriad of tasks.

"Imagine devices the size of blood cells, each holding a chemotherapy drug. If outfitted with this kind of engine, then the devices could make their own energy from sugar in the bloodstream," explained Travis. "Using molecular pumps powered by that energy, the devices could kick out that drug cargo at defined rates, and specifically where it's needed, such as at the site of a solid tumor."

The research team has already applied the concept of tethered enzymes in a device to detect signs of stroke or traumatic brain injury in blood samples. Their discovery could represent realizing the potential of artificial cells much sooner according to Mukai.