Scanning electron microscope image of cell growth on GaN that has been coated with peptides. Image: North Carolina State University
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 material’s 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 Alzheimer’s 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 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 GaN’s 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. We’ve 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.