May 2, 2023 | Researchers at Pennsylvania State University are leading the development of a lateral flow assay for mpox (monkeypox), which in another few years could join pregnancy tests on retail pharmacy shelves. The more immediate plan is to produce a rapid, point-of-care (POC) test for low-resource settings that involves a smartphone or other small reader capable of differentiating mpox from smallpox based on the light bouncing back from gold nanoparticles underpinning the platform, according to Dipanjan Pan, Penn State Huck Chair professor of nanomedicine, nuclear engineering, materials science, and engineering and biomedical engineering.
Pan’s lab has already produced POC tests for a wide range of infectious diseases, including COVID-19, syphilis, chlamydia, and gonorrhea. He and his team pivoted to mpox last year when the viral disease became an emerging threat, spreading from Africa into more than 100 countries with roughly one-third of global cases concentrated in the United States.
Their molecular sensor, newly described in Advanced Functional Materials (DOI: 10.1002/adfm.202212569), can detect even trace amounts of viral DNA in biological samples within minutes—specifically, from the conserved region of the mpox virus genome that is not subject to mutations. The technology leverages the power of light or, more specifically, the “plasmonic response” of zero-dimensional gold nanoparticles boosted by their interaction with two-dimensional metallic nanoplatelets.
When absorbing light, the nanoparticles respond to the presence of mpox by visibly changing color from purple to blue—meaning no expensive equipment or specialty expertise required to render test results, Pan explains. The plasmonic particles respond to even very low concentrations of the virus because of their interface with the two-dimensional nanomaterial (hafnium disulfide) enriching the natural optical properties of nanoscale gold.
To ensure the gold nanoparticles would interact with the mpox viral DNA, thereby enhancing the specificity of the test, the researchers also produced single-stranded DNA whose nucleotides are complementary to a particular genetic segment of the virus, says Pan. This “nanocomposite” approach was able to selectively detect mpox with no cross-reactivity with other viruses.
The purple-to-blue color change happens quickly when a cluster of the gold nanoparticles come together to bind to a complementary DNA sequence of the mpox such that a cluster of gold forms and starts behaving like a bigger particle, he adds. These are falsely colored on electron microscope images as red and green for better representation.
‘More Dangerous Than Smallpox’
The strategy being employed here is more material-driven than the POC tests previously developed in Pan’s lab, formerly at the University of Illinois at Urbana-Champaign and University of Maryland. The work is now being developed as a platform technology extensible to other viruses (DNA and RNA) as well as bacteria and fungi, he says. “We improved on our [prior] work to show that these gold particles give off a lot more information than we anticipated in the past” when combined with the two-dimensional material.
Some clinicians have suggested that smallpox therapies might work against mpox, given that the two diseases have similar clinical symptoms. “But that’s not really the case,” says Pan. “Mpox can be dangerous because it causes enlargement of lymph nodes or glands in the body, and there is no cure.” It is also highly contagious since it can be transmitted from animals to humans as well as person to person.
The platform under development is intended to be a multiplex system applicable to a broad range of pathogens, he says. Once it is validated clinically, the lab hopes to bring the technology to market, which might initially happen through Emergency Use Authorization by the Food and Drug Administration (FDA) that allows for a lower level of evidence based on patient sample testing.
Commercial partners will be needed, says Pan, who has launched multiple start-ups. The academic team is looking to work with a larger, experienced company with the wherewithal to operate at scale.
One of the only positive aspects of COVID is that it sped the pace of technological development and left the world better prepared to handle other emerging threats, Pan adds. In the future, virus detection in low-resource settings—be they community centers, urgent care, or retail pharmacies like Walgreens and CVS—will be the epicenters for quick and easy POC testing and pandemic prevention activities.
At present, the only FDA-approved mpox diagnostics available are PCR assays that are time- and resource-intensive, says Pan. “By the time you get results [on an individual], they have probably already infected several [other] people.” A rapid test, requiring only a small sample of lesion swab and short wait time for results, could dramatically slow the rate of transmission for the virus.
Separately, Northwestern University and Minute Molecular Diagnostics report that they have teamed up to pursue development of a rapid PCR test capable of producing results in about 15 minutes, which would at least provide speed to answers. Its DASH Analyzer was also originally designed to help address the novel coronavirus pandemic.