Scientists at the University of Massachusetts Amherst have developed a biosensor that is based on protein nanowires that are created by bacteria. The protein nanowires are highly sensitive to ammonia, in this case, which is present in the breath of patients with kidney disease, but it is likely possible to create nanowires for a huge array of other health biomarkers. The researchers genetically modified E. Coli to create protein nanowires with increased ammonia sensitivity. The nanowires are layered onto an electrode array and then if ammonia binds to them, it will change the electrical signal of the biosensor, revealing the presence of kidney disease or allow doctors to track a patient’s progress. The protein constructs are also biodegradable, and more environmentally friendly than conventional synthetic nanowires.
The human nose is an incredibly powerful sensor, and acted as the inspiration for this latest biosensor. “Human noses have hundreds of receptors, each sensitive to one specific molecule,” said Jun Yao, a researcher involved in the study. “They are vastly more sensitive and efficient than any mechanical or chemical device that could be engineered. We wondered how we could leverage the biological design itself rather than rely on a synthetic material.”
The technology began with a bacterium called Geobacter sulfurreducens, which produces electrically conductive protein nanowires. However, these bacteria are difficult to cultivate and work with, so the researchers took the gene responsible for the protein deposits and inserted it into E. Coli. “What we’ve done,” said Dereck Lovley, another researcher involved in the study, “is to take the ‘nanowire gene’ — called pilin — out of G. sulfurreducens and splice it into the DNA of Escherichia coli, one of the most widespread bacteria in the world.”
The researchers also modified the gene so that it now encodes for an ammonia-sensitive peptide called DLESFL. “Genetically modifying the nanowires made them 100 times more responsive to ammonia than they were originally,” said Yassir Lekbach, another researcher involved in the project. “The microbe-produced nanowires function much better as sensors than previously described sensors fabricated with traditional silicon or metal nanowires.”
Excitingly, the researchers believe that they can modify these nanowires to sense a huge variety of biomarkers, suggesting that one day you could use one sensor to detect a long list of diseases. “It’s possible to design unique peptides, each of which specifically binds a molecule of interest,” said Toshiyuki Ueki, another researcher who participated in the study. “So, as more tracer molecules, emitted by the body and which are specific to particular a disease are identified, we can make sensors that incorporate hundreds of different chemical-sniffing nanowires to monitor all sorts of health conditions.”
Study in journal Biosensors and Bioelectronics: Microbial nanowires with genetically modified peptide ligands to sustainably fabricate electronic sensing devices