Semiconductor chips enable biomolecular sensing

Bioengineers at the University of California San Diego have integrated the olfactory receptor of an insect called a jumping bristletail into semiconductor chips made of graphene, creating an electronic nose capable of sniffing out a variety of small organic compounds.

This biomimetic bioelectronic sensor can detect and distinguish between molecules that are difficult for conventional electronic sensors to differentiate. This work opens the door to building semiconductor-based chemical sensing systems inspired by nature for applications in health care, environmental monitoring, food quality, agriculture and biodefence.

In a paper published in Advanced Materials, researchers led by bioengineers at UC San Diego describe a method to manufacture at scale the MhOR5 odorant receptor from the insect Machilis hrabei, and chemically attach the purified MhOR5 protein to high-performance graphene field effect transistors (gFETs). gFETs are semiconductor devices that rely on graphene instead of silicon as the conductive material, resulting in exceptional sensitivity to molecular change.

The researchers tested their MhOR5-functionalised gFETs against 16 chemically diverse compounds, including DEET, hexanol and eugenol, at different concentrations. The sensor produced a concentration-dependent electrical response for each of the 16 compounds.

“Advances in engineering, biology, biomanufacturing and semiconductor technology are now making it possible to reproduce the remarkable sensing capabilities of other organisms, and directly interface them with scalable semiconductor chips,” said Kiana Aran, corresponding author of the study. “We’re no longer just studying biology; we’re beginning to integrate biological functions with semiconductor technology in a way that can be manufactured at scale.”

To manufacture, purify and integrate MhOR5 into the gFET, the researchers took the genetic sequence of this olfactory receptor, synthesised it and transfected this receptor into mammalian cells. They purified the MhOR5 protein from cell membranes, and found that the MhOR5 protein’s tetrameric form was stable after being stored for three months at -80°C. The manufactured MhOR5 was also stable after being subjected to several freeze–thaw cycles.

The researchers then took the purified MhOR5 protein and chemically attached it to the graphene surface of the gFET platform using Carbodiime Crosslinker Chemistry and the PBASE molecule that links molecules including proteins with carbon-based nanomaterials such as graphene.

This is reportedly the first direct integration of MhOR5 onto a gFET for selective, label-free detection of small organic compounds.

Image credit: iStock.com/rdegrie