Nanobots have long been dreamed of by scientists and science fiction writers alike – microscopic machines that enter the bloodstream or operate undetected. What if nature could be harnessed to provide similar capabilities? What if warfighters had the capability to both counteract and treat chemical weapon agents in real-time? The Defense Threat Reduction Agency’s Chemical and Biological Technologies Department, along with Ayusman Sen, Ph.D., of Penn State University, are using enzymes that catalytically harness the chemical energy in their environment to move autonomously and do the “bot” work to neutralize the organophosphate nerve agents. While these enzymes are not nanobots by the technical definition, they function similarly.
Enzymes are naturally occurring protein catalysts of chemical reactions. Almost all metabolic processes in a cell need enzymes in order to occur at rates fast enough to sustain life. Hundreds of enzymes constantly move freely throughout our bodies and can enable the reactions of hundreds of thousands of molecules per second. Previously unknown, enzymes generate mechanical force when they facilitate a reaction.
Proteins have traditionally been regarded as drifters, catching a ride in the cell cytoplasm by passive diffusion and encountering reactants and other enzymes by chance. However, Sen and his team have demonstrated that proteins can swim along a path toward higher levels of reactant. More importantly, when enzymes catalyze a reaction, they inexplicably move, possibly due to a change in the shape of the enzyme upon catalysis. These newly discovered features make enzymes an attractive material for developing nanobots.
Additionally, according to Sen, if you attach the enzyme to a support, this force gets transmitted to the fluid, and then combined, the two will act as nanofluidic pumps. In essence, the chemical that it is pumping through the enzymes becomes the fuel, which in turn pumps in the antidote. These non-mechanical pumps provide a precise control overflow rate without the aid of an external power source and are capable of turning on in response to specific analytes in solution.
In this way, Sen’s team, backed by DTRA CB funding, made enzyme-powered nanobot pumps that destroy organophosphate nerve agents while simultaneously administering an antidote to the body. Exposure to these chemicals during military combat or terrorist attacks can cause permanent neurological damage and, in some cases, death.
According to Sen, there are enzymes that decompose nerve agents, which fuels the pumping actions. By attaching the enzyme to a reservoir, like a gel that is filled with nerve agent antidote, when it comes in contact with a nerve agent, it pumps out the agent and pumps in the antidote. It’s a one-two punch — it pumps out the agent and pumps in the antidote. In this case, the antidote is an enzyme called organophosphorus acid anhydrolase.
However, the enzyme-reservoir combination has to be in or on a body before exposure to a nerve agent, like a prophylaxis or a sunscreen. According to Sen, nanobot pumps could someday be incorporated into protective clothing for the military or first responders. He is also exploring applications for nanobots based on other enzymes, for example, an insulin-pumping device to treat diabetes and an enzyme-powered drug-delivery system.
In the event of an attack, the ability to both counteract and treat organophosphate nerve agents could save warfighters’ lives while restoring readiness and enabling mission success.
DTRA CB POC: Alison Director-Myska, Ph.D.; alison.e.myska.civ@mail.mil PSU POC: Ayusman Sen, Ph.D.; asen@psu.edu