Researchers from North Carolina
State University
and Purdue University have shown that the
semiconductor material gallium nitride (GaN) is non-toxic and is compatible
with human cells – opening the door to the materials use in a variety of
biomedical implant technologies.

GaN is currently used in a host of technologies, from LED
lighting to optic sensors, but it is not in widespread use in biomedical
implants. However, the new findings from NC State and Purdue mean that GaN
holds promise for an array of implantable technologies – from electrodes used
in neurostimulation therapies for Alzheimers to transistors used to monitor
blood chemistry.

“The first finding is that GaN, unlike other semiconductor
materials that have been considered for biomedical implants, is not toxic. That
minimizes risk to both the environment and to patients,” says Dr. Albena
Ivanisevic, who co-authored a paper describing the research. Ivanisevic is an
associate professor of materials science and engineering at NC State and
associate professor of the joint biomedical engineering program at NC State and
the University of North Carolina at Chapel Hill.

Researchers used a mass spectrometry technique to see how
much gallium is released from GaN when the material is exposed to various
environments that mimic conditions in the human body. This is important because
gallium oxides are toxic. But the researchers found that GaN is very stable in
these environments – releasing such a tiny amount of gallium that it is
non-toxic.

The researchers also wanted to determine GaNs potential
biocompatibility. To do this they bonded peptides – the building blocks that
make up proteins – to the GaN material. Researchers then placed peptide-coated
GaN and uncoated GaN into cell cultures to see how the material and the cells
interacted.

Researchers found that the peptide-coated GaN bonded more
effectively with the cells. Specifically, more cells bonded to the material and
those cells spread over a larger area.

“This matters because we want materials that give us some
control over cell behavior,” Ivanisevic says. “For example, being able to make
cells adhere to a material or to avoid it.

“One problem facing many biomedical implants, such as
sensors, is that they can become coated with biological material in the body.
Weve shown that we can coat GaN with peptides that attract and bond with
cells. That suggests that we may also be able to coat GaN with peptides that
would help prevent cell growth – and keep the implant ‘clean. Our next step
will be to explore the use of such ‘anti-fouling peptides with GaN.”

The paper, “Gallium Nitride is Biocompatible and Non-Toxic
Before and After Functionalization with Peptides,” is forthcoming from Acta
Biomaterialia and was co-authored by Ph.D. students Scott A. Jewett and Matthew
S. Makowski; undergraduate Benjamin Andrews; and Michael J. Manfra – all of
Purdue. The research was funded by the National Science Foundation.

NC States Department of Materials Science and Engineering,
and joint Department of Biomedical Engineering, are part of the universitys College of Engineering.