New Polymers Promise to Enhance Neural Interfaces

by James Cavuoto, editor

Several new polymeric biomaterials are promising to enhance the functionality of existing neural interfaces, which are largely based on metals. At least two commercial firms have begun offering electrodes and other components of neural stimulation and recording systems that have mechanical, electrical, and functional properties not found in metal electrodes.

One of the most promising commercial ventures in this area is Biotectix LLC, a Quincy, MA startup company that spun off from research at the University of Michigan last year. David Martin, a University of Michigan researcher who has been working with new electrode materials for some time, is one of the founders of the startup, along with two of his doctoral students. Allied Minds, a Massachusetts incubator firm, invested $750,000 in Biotectix.

Biotectix has licensed technology developed at the Organic Electronics and Electroactive Biomaterials Laboratory, University of Michigan. “These technologies lay the groundwork for a fully integrated electrode-tissue interface,” said Martin. “With such an interface, we will be able to counter the tissue injury and inflammation associated with implantation of microelectrodes and neural prosthetic devices and improve quality of life for individuals requiring such devices.”

Traditional metallic electrodes (steel, platinum, iridium, gold) are energy inefficient, hard, non-biocompatible, and can cause local tissue damage and scarring. They also have limited-MRI compatibility, and often don’t function for as long or as well as intended, leading to more frequent battery replacement. Devices that fall into this class include pacemakers, cortical probes, cochlear implants, glucose sensors, and deep brain stimulators.

Biotectix has developed soft, bioactive conductive polymer electrodes and coatings for electrodes. This novel technology results in increased electrode sensitivity and charge transfer capacity conferred by polymer coatings, significantly enhancing device function and battery life. In addition, drugs can be released from the polymer coating as desired: passive, intermittent, or extended release.

“One of the most exciting aspects of the technology is its bioactive attributes. By this we mean the technology’s ability to promote neural in-growth. Byproducts of this capability include improved mechanical integration and reduced immune response,” said Marc Eichenberger, COO of Allied Minds. “It seems like every day we see new opportunities for these technologies. One example is to improve the interface with robotic arms being developed by the U.S. government and others. Initially we will look to benefit key areas such as cochlear implants, deep brain stimulation and cardiac ­markets.”

Biotectix uses a polymer called polyethylenedioxy-thio-phene, or PEDOT, to make coatings it hopes will make cardiac, cranial, and cochlear implants more biocompatible. Martin is also principal investigator for a five-year, $5.7 million grant announced last year by the U.S. Army Research Office to develop the next generation of prosthetic devices for wounded soldiers. Although not funding Biotectix directly, Martin said, the grant should produce research that speeds product development.

Another commercial firm actively pursuing the market for biopolymers in neurotechnology devices is Invibio Ltd., a UK-based firm with U.S. offices in Woodbury, MN. Invibio markets a material called PEEK-OPTIMA. The polymer has already been selected as lead insulation material for a deep-brain stimulation system. Compared with other polymer-based materials, such as polyimide, PEEK-OPTIMA has relatively low moisture absorption and is also injection moldable, which offers device manufacturers greater flexibility. Invibio materials also offer radiotransparency, which eliminates interference and improves efficiency for remote monitoring applications.

Executives from both Biotectix and Invibio will be making presentations at the 2008 Neurotech Leaders Forum, October 23-24 in San Francisco, CA.