Scanning electron microscope image of cell growth on gallium nitride that has been coated with peptides. Credit: Albena Ivanisevic, North Carolina State University.
We live in good times, medically speaking. Creaky, painful knees and hips can be replaced. Arteries can be held open with stents. A variety of implants hold us together, stabilize our heartbeats, relieve our pain and keep us going for a good long time.
Semiconductor materials are of interest for biomedical implants for applications like electrodes for neurostimulation therapy and sensors. However, the interior of the body is a harsh environment-corrosive, reactive and sensitive to toxins.
A new paper published by a North Carolina State University and Purdue research team reports that gallium nitride, a semiconductor, shows strong promise as a biocompatible and non-toxic candidate material for biomedical implants.
In the press release, co-author and professor at NC State Albena Ivanisevic says, “The first finding is that GaN, unlike other semiconductor materials that have been considered for biomedical implants, is not toxic.” Mass spectrometry was used to show that GaN is very stable in in-vitro environments, releasing so little gallium as to be considered non-toxic. The chemical stability is critical because gallium oxides are toxic to humans.
The team also tested the biocompatibility of GaN by coating specimens with peptides—the building blocks of proteins—and comparing cell interactions with coated and uncoated samples.
The functionality of the material is important, Ivanisevic says, “because we want materials that give us some control over cell behavior, for example, being able to make cells adhere to a material or to avoid it.”
The uncoated GaN did not interfere with cell growth, but the peptide-coated GaN bonded with the cells. Per the abstract: “Peptide terminated GaN promoted greater cell spreading and extension of neurites.” Ivanisevic says the result also suggests, “we may also be able to coat GaN with peptides that would help prevent cell growth—and keep the implant ‘clean.'”
All of this means that, according to the abstract, “peptide-modified GaN is a biocompatible and non-toxic material that can be used to probe chemical and electrical stimuli associated with neural interfaces.”
Full details are available in “Gallium Nitride is Biocompatible and Non-toxic Before and After Functionalization with Peptides,” written by Scott A. Jewett, Matthew S. Makowski, Benjamin Andrews, Michael J. Manfra and Ivanisevic, and published in Acta Biomaterialia, (doi:10.1016/j.actbio.2011.09.038)