Although real “cyborgs” – partly human, partly robotic beings – are science fiction, researchers are taking steps to integrate electronics with the body. Such devices could check for tumor development or stand in for damaged tissue. But electronics directly connecting to human tissue in the body is an enormous challenge. Now a team is reporting new coatings for components that would fit them more easily in this environment.
The researchers will present their results today (Agusut 17, 2020) at the American Chemical Society (ACS) Fall 2020 Virtual Meeting & Expo. ACS will hold the meeting until Thursday. It has more than 6,000 presentations on a wide range of scientific topics.
“We got the idea for this project because we tried rigid, inorganic micro-electrodes to interface with the brain, but brains are made from organic, salty, living materials,” says David Martin, Ph.D., who led the study. in charge of. “It didn’t work well, so we thought there had to be a better way.”
Traditional microelectronic materials, such as silicon, gold, stainless steel and iridium, cause scarring on implants. For applications in muscle or brain tissue, electrical signals must flow for them to operate properly, but scars interrupt this activity. The researchers reasoned that a coating could help.
Molecular model of PEDOT with maleimide; carbon atoms are gray, oxygen red, nitrogen blue, sulfur yellow and hydrogen white. Credit: David Martin
“We started looking at organic electronic materials such as conjugated polymers that were used in non-biological devices,” said Martin, who is at the University of Delaware. “We found a chemically stable sample that was sold commercially as an antistatic coating for electronic displays.” After testing, the researchers found that the polymer had the properties needed for interface of hardware and human tissue.
“These conjugated polymers are electrically active, but they are also ionically active,” says Martin. “Counter ions give them the charge they need, so when they are in action, both electrons and ions move.” The polymer, known as poly (3,4-ethylenedioxytiophene) as PEDOT, dramatically improved the performance of medical implants by reducing their impedance by two to three orders of magnitude, thereby increasing signal quality and battery life in patients.
Martin has since determined how to specialize the polymer, by putting different functional groups on PEDOT. Add a carboxylic sour, aldehyde or maleimide substituent on the ethylenedioxythiophene (EDOT) monomer gives researchers the versatility to make polymers with a variety of functions.
“The maleimide is particularly potent because we can click on chemical substitutions to make functionalized polymers and biopolymers,” says Martin. Unsubstituted monomer mixing with the maleimide-substituted version results in a material with many locations where the team peptides, antibodies as DNA. “Name your favorite biomolecule, and you can basically make a PEDOT movie that has whatever biofunctional group you might be interested in,” he says.
Most recently, Martin’s group made a PEDOT film with a vascular endothelial growth factor (VEGF) antibody added. VEGF stimulates growth of blood fats after an injury, and tumors cut off this protein to increase its blood supply. The polymer that the team developed could act as a sensor to detect overexpression of VEGF and thus early stages of disease, among other potential applications.
Other functionalized polymers have neurotransmitters on them, and these films can help understand or treat brain or nervous system disorders. To date, the team has created a polymer containing dopamine, which plays a role in addictive behavior, as well as dopamine-functionalized variants of the EDOT monomer. Martin says that these biologically-synthetic hybrid materials may one day be useful in combining artificial intelligence with the human brain.
Ultimately, Martin says, his dream is to be able to adapt how these materials deposit on a surface and then place them in tissue in a living organism. “The ability to do the polymerization in a controlled way in a living organism would be fascinating.”
A press conference on this topic will be held online on Wednesday, August 19, 2020, at 10 a.m. Eastern time.
The researchers recognize support and funding from the National Science Foundation and the University of Delaware.
