Optical biosensor detects monkeypox more rapidly

19 Nov 2024

UC San Diego and Boston University develop faster diagnosis to combat spread of the disease.

Monkeypox is a growing current health concern, with a potentially fatal variant of human mpox spreading across certain African countries, and a different non-lethal variant also now being observed elsewhere.

Rapid diagnosis of the virus is key to containing its spread, so there is an urgent need for faster and more cost-effective diagnostic tools as preparation for any possible global pandemic.

A team from University of California, San Diego and Boston University has now developed an optical biosensor designed to rapidly detect and identify monkeypox.

Reported in Biosensors and Bioelectronics, the interferometric technology could allow clinicians to diagnose the disease right away at the point of care rather than wait for lab results.

In the clinic, mpox symptoms such as fever, pain, rashes and lesions resemble those of many other viral infections, making visual diagnosis difficult. Analysis by polymerase chain reaction (PCR) is currently the only approved method of diagnosing mpox, but it is expensive, requires a laboratory, and can take days or weeks to get results.

The project's new solution is based around interferometric reflectance imaging sensor (IRIS) technology, exploiting light interference from an optically transparent thin film and eliminating the need for complex optical resonances to enhance the signal. This builds on prior work at the Boston lab of Selim Ünlü, which developed optical biosensors for detecting the viruses that cause Ebola and Covid-19, among others.

In earlier studies an IRIS-based platform using a layered silicon/silicon dioxide microarray chip was used to visualize single viruses, by collecting all the light from the sensor surface and treating viruses as sub-diffraction scattering objects. Identifying the characteristic defocus signature of those objects allowed the viruses to be spotted.

Stopping future pandemics right now

For the new monkeypox device, the project expanded this approach into multi-spectral pixel diversity IRIS, or PD-IRIS, in which the optical signature of interest is encoded into multiple wavelengths, and target particles are detected in a single snapshot rather than through scanning of a sample.

In the UC San Diego platform, simultaneous irradiation of the chips with red and blue light creates the interference, with measureably different responses when the virus-antibody nanoparticles were present. A color camera detects this small signal and counts 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 Selim Ünlü. He compared the process to FM radio, which mixes a weak signal containing information with a more powerful carrier signal at the same frequency, effectively amplifying the weak signal.

In trials, the scientists tested the platform on monkeypox and also on herpes simplex and cowpox virus samples, which have similar clinical presentations to mpox. The biosensor assay easily discriminated mpox samples from these other viruses, commented UC San Diego, and did so in a short space of time.

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

Ray and Ünlü are now working toward commercialization, not only to address the urgent need for rapid mpox tests but also to keep outbreaks from turning into pandemics. But this effort will require government support, commented the project, because there is little market for diagnostics addressing future threats.

"If we don't take care of this particular epidemic right now, it is not going to be limited within Africa," commented Partha Ray.