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Although the real “cyborgs” – partly human, partly robotic – are science fiction, researchers are taking steps to integrate electronics into the body. Such devices could monitor tumor development or replace damaged tissue. But connecting electronics directly to human body tissue is a huge challenge. Now, a team is bringing back new coatings for components that could help them integrate more easily into this environment.
The researchers will present their results today (Agusut 17, 2020) at the American Chemical Society (ACS) Fall 2020 Virtual Meeting & Expo. ACS is holding the meeting until Thursday. It includes over 6,000 presentations on a wide range of scientific topics.
“We got the idea for this project because we were trying to interface rigid, inorganic microelectrodes with the brain, but brains are made of organic, salty, living material,” says David Martin, Ph.D., who led the study. “It wasn’t working well, so we thought there had to be a better way.”
Traditional microelectronic materials, such as silicon, gold, stainless steel, and iridium, cause scarring during implantation. For applications in muscle or brain tissue, electrical signals must flow for them to work properly, but scars interrupt this activity. The researchers felt that a coating could help.
Molecular model of PEDOT with maleimide; the carbon atoms are gray, the oxygen red, the nitrogen blue, the sulphide yellow and the hydrogens white. Credit: David Martin
“We started looking at organic electronic materials like conjugated polymers that were used in non-biological devices,” says Martin, who is at the University of Delaware. “We found a chemically stable example that was sold commercially as an antistatic coating for electronic displays.” After testing, the researchers found that the polymer had the properties needed to interface human material and tissue.
“These conjugated polymers are electrically active, but they are also ionically active,” explains Martin. “The counterions give them the charge they need, so when they’re working, the electrons and the ions move around.” The polymer, known as poly (3,4-ethylenedioxythiophene) or PEDOT, has dramatically improved the performance of medical implants by lowering their impedance by two to three orders of magnitude, thereby increasing signal quality and lifespan. of battery in patients.
Martin has since figured out how to specialize the polymer, putting different functional groups on PEDOT. Addition of a carboxylic acid, an aldehyde or maleimide substituting for ethylenedioxythiophene (EDOT) monomer gives researchers the versatility to create polymers with a variety of functions.
“Maleimide is particularly powerful because we can make click-to-click chemical substitutions to make functionalized polymers and biopolymers,” Martin explains. Mixing unsubstituted monomer with the maleimide substituted version results in material with many locations where the team can attach peptides, antibodies or DNA. “Name your favorite biomolecule, and you can basically make a PEDOT movie that has the biofunctional group you’re interested in,” he says.
More recently, Martin’s group created a PEDOT movie with an antibody for vascular endothelial growth factor (VEGF) attached. VEGF stimulates the growth of blood vessels after injury, and tumors hijack this protein to increase their blood supply. The polymer the team developed could serve as a sensor to detect overexpression of VEGF and thus early stages of the disease, among other potential applications.
Other functionalized polymers contain neurotransmitters, and these films could help detect or treat disorders of the brain or nervous system. So far, the team has made a polymer with dopamine, which plays a role in addictive behaviors, as well as dopamine-functionalized variants of the EDOT monomer. Martin says these hybrid bi-synthetic materials could one day be useful in fusing artificial intelligence with the human brain.
Ultimately, Martin says, his dream is to be able to adapt the way these materials settle on a surface and then put them into the tissues of a living organism. “The ability to polymerize in a controlled manner inside a living organism would be fascinating.”
A press conference on this will be held on Wednesday, August 19, 2020 at 10 a.m. EST online.
The researchers acknowledge the support and funding from the National Science Foundation and the University of Delaware.
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