Optical biosensor rapidly detects virus that causes mpox

The technology could allow clinicians to diagnose the disease at the point of care rather than wait for lab results. The study has been published in Biosensors and Bioelectronics.

In the clinic, mpox symptoms such as fever, pain, rashes and lesions resemble those of many other viral infections, said Partha Ray, an associate project scientist at UC San Diego School of Medicine and co-principal investigator on the study.

Polymerase chain reaction (PCR) is currently the only approved method of diagnosing mpox, which is expensive, requires a laboratory, and can take days or weeks to get results.

“A deadly combination when there is a fast-spreading epidemic or pandemic,” Ray said in a statement.

The search for a better molecular diagnostic for mpox draws on over a decade of research in the lab of Selim Ünlü, a distinguished professor of engineering at Boston University (BU) and co-principal investigator on the study.

The lab has developed optical biosensors for detecting the viruses that cause Ebola haemorrhagic fever and COVID-19, among others. Ray’s team at UC San Diego collaborated with Ünlü’s lab, providing biological expertise and authenticated samples to Ünlü’s engineering team.

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The study, led by first author Mete Aslan, a Ph.D. student in electrical and electronics engineering at BU, used a digital detection platform called Pixel-Diversity interferometric reflectance imaging sensor (PD-IRIS) to detect the virus. 

The researchers used samples collected from the lesions of a patient at UC San Diego Health with laboratory-confirmed mpox. They briefly incubated the samples with monoclonal monkeypox antibodies provided by Ray’s lab that bind to proteins on the surface of the virus. The virus-antibody complex was then transferred into tiny chambers on the surface of silicon chips on the sensor that were treated to fix these nanoparticles. 

Shining precise wavelengths of red and blue light simultaneously on the chips caused interference, which resulted in slightly different responses when the virus-antibody nanoparticles were present. A colour camera was used to detect this small signal and count individual particles with high sensitivity. 

“You're not trying to see the scattered light from the virus particle itself, but you're looking at the interferometric signature of the field of scattered light mixed with the field that is reflected from the surface of the chip,” said Ünlü.

The scientists also analysed herpes simplex virus and cowpox virus samples, which have similar clinical presentations to mpox. The biosensor assay is said to have easily discriminated mpox samples from these other viruses, demonstrating that the specificity of the assay is essential for distinguishing mpox from these common viral diseases.

“Within two minutes, we can tell whether someone has monkeypox or not,” said Ray. “From collecting the virus samples to getting the real-time data takes around 20 minutes.”

Ray envisions the tests being mass-produced as kits and sold to clinics, further reducing costs. A single boxed kit could be used to test for a variety of viruses, such as syphilis or HIV.

“The chip would be the same,” said Ray. “The only thing that would be different here is the binding antibody that would be specific for a particular virus.”

A new variant of human mpox has claimed the lives of approximately five per cent of people with reported infections in the Democratic Republic of the Congo since 2023. Since then, it has spread to several other countries. The World Health Organization declared the outbreak a Public Health Emergency of International Concern on August 14.