Scientists engineer ‘revolutionary electronic nose’ to sniff out diseases

They produced a nanowire 10,000 times thinner than a human hair that can be cheaply grown by common bacteria and tuned to "smell."
Loukia Papadopoulos
An illustration of the new artificial noses.jpg
An illustration of the new artificial noses.

UMass Amherst 

In 2017, researchers developed an electronic nose that could smell diseases. Now, scientists at the University of Massachusetts Amherst have produced a nanowire 10,000 times thinner than a human hair that can be cheaply grown by common bacteria and tuned to “smell” a vast array of chemical tracers. 

It can even detect smells given off by people afflicted with a wide range of medical conditions, such as asthma and kidney disease, according to a press release by the institution published Wednesday.

Monitoring health complications

These specially tuned wires can be combined onto tiny, wearable sensors to become an unprecedented tool for monitoring potential health complications. 

The innovation was spearheaded by the new study’s senior authors Derek Lovley, Distinguished Professor of Microbiology at UMass Amherst, and Jun Yao, professor of electrical and computer engineering in the College of Engineering at UMass Amherst. It was based on the functioning of the human nose.

“Human noses have hundreds of receptors, each sensitive to one specific molecule,” said Yao.

“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.”  

To do this, they used a bacterium known as Geobacter sulfurreducens which has the natural ability to grow tiny, electrically conductive nanowires. They then proceeded to genetically edit it. 

“What we’ve done,” says Lovley, “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.” 

Lovley, Yao, and the team then further modified it to include a specific peptide known as DLESFL, which is extremely sensitive to ammonia—a chemical often present in the breath of those with kidney disease. 

“Genetically modifying the nanowires made them 100 times more responsive to ammonia than they were originally,” said Yassir Lekbach, the paper’s co-lead author and a postdoctoral researcher in microbiology at UMass Amherst.

“The microbe-produced nanowires function much better as sensors than previously described sensors fabricated with traditional silicon or metal nanowires.” 

Countless applications

Now, the new sensors have many applications beyond the detection of ammonia and kidney disease. 

Toshiyuki Ueki, the paper’s other co-lead author and research professor in microbiology at UMass Amherst, said that “it’s possible to design unique peptides, each of which specifically binds a molecule of interest.”

“So, as more tracer molecules emitted by the body and which are specific to a particular disease are identified, we can make sensors that incorporate hundreds of different chemical-sniffing nanowires to monitor all sorts of health conditions,” concluded Ueki in the press statement.

The new innovations are detailed in the journal Biosensors and Bioelectrics.

Study abstract: 

Nanowires have substantial potential as the sensor component in electronic sensing devices. However, surface functionalization of traditional nanowire and nanotube materials with short peptides that increase sensor selectivity and sensitivity requires complex chemistries with toxic reagents. In contrast, microorganisms can assemble pilin monomers into protein nanowires with intrinsic conductivity from renewable feedstocks, yielding an electronic material that is robust and stable in applications, but also biodegradable. Here we report that the sensitivity and selectivity of protein nanowire-based sensors can be modified with a simple plug and play genetic approach in which a short peptide sequence, designed to bind the analyte of interest, is incorporated into the pilin protein that is microbially assembled into nanowires. We employed a scalable Escherichia coli chassis to fabricate protein nanowires that displayed either a peptide previously demonstrated to effectively bind ammonia, or a peptide known to bind acetic acid. Sensors comprised of thin films of the nanowires amended with the ammonia-specific peptide had a ca. 100-fold greater response to ammonia than sensors made with unmodified protein nanowires. Protein nanowires with the peptide that binds acetic acid yielded a 4-fold higher response than nanowires without the peptide. The protein nanowire-based sensors had greater responses than previously reported sensors fabricated with other nanomaterials. The results demonstrate that protein nanowires with enhanced sensor response for analytes of interest can be fabricated with a flexible genetic strategy that sustainably eliminates the energy, environmental, and health concerns associated with other common nanomaterials.

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