Tethered To Chip, Energy Supply That Drives Sperm Could Power 'Nanobot'

The work by researchers at Cornell's Baker Institute of Animal Health may be the first demonstration of how multistep biological pathways can be assembled and function on a human-made device.

"One of the major limitations in making implantable, nanomedical devices is providing power to them," said Travis, who conducts his research at the James A. Baker Institute for Animal Health, part of Cornell's College of Veterinary Medicine. "If you can engineer a device that can make its own energy, then it can potentially last longer and regulate its own task rate."

Another potential use for this technology: creating nanoscale pumps that could release chemotherapeutics or antibiotics into specific places in the body.

Mammalian sperm have to delivery energy to the long, thin, whip-like tails that power their swimming. Sperm meet the challenge, in part, by onsite power generation, modifying the enzymes of glycolysis so that they can attach themselves to a solid structure running the major length of the sperm tail. From that secure perch, glycolytic enzymes convert sugar into ATP, supplying energy all along the sperm's bending and flexing tail.

Chinatsu Mukai, Alex Travis, and others at Cornell's College of Veterinary Science looked at the early steps in the glycolysis pathway to see if they could move it from the thin "fibrous sheath" that covers the sperm tail to a solid inorganic substitute--a nickel-NTA (nitrilotriacetic acid) chip.

First, the researchers replaced the sperm-specific targeting domain of hexokinase, the first enzyme of glycolysis, with a tag that binds to a special gold surface. Even when tethered, the enzyme remained functional. Next they tagged the second enzyme in the pathway, glucose-6-phosphate isomerase. This too was active when tethered. With both attached to the same support, the enzymes acted in series with the product of the first reaction serving as substrate for the second.

These are only the first steps in reproducing the full glycolytic pathway on an inorganic support, say Mukai and Travis. Mukai and Travis suggest that their work serves as proof of principle that the organization of the glycolytic pathway in sperm might provide a natural engineering solution of how to produce ATP locally on nano devices.

The paper, Coupled Metabolic Reaction on a Chip: A Step Toward Energy Production on Implantable Medical Devices,  was presented  Dec. 3 at  the American Society for Cell Biology's 47th Annual meeting.