Images showing the nano-assembly mpox rapid test before (a) and after (e) the addition of mpox DNA. The red and green color encodes for gold nanoparticles and hafnium disulfide nanoplatelets respectively. The white arrows show dispersed gold nanoparticles and grouped gold nanoparticles. Credit: Courtesy of Dipanjan Pan
The current outbreak of mpox, formerly known as monkeypox, has affected more than 100 countries, resulting in more than 86,000 infections worldwide. Approximately one-third of these cases have been in the United States, where polymerase chain reaction (PCR) is the only FDA-approved testing method for mpox diagnosis. While highly sensitive and accurate, PCR tests can take several days to return results due to the need to transport samples to labs with advanced instrumentation. Penn State researchers have now developed the first rapid test for mpox, which returns results in just minutes.
The new technology is based on self-assembling nanomaterial heterostructures composed of “zero-dimensional” spherical gold nanoparticles and two-dimensional hafnium disulfide nanoplatelets. The gold nanoparticles serve as plasmons, holding unique optical properties due to their size and shape, which are layered with the halfnium disulfide in order to enhance the plasmons’ response to biological signals, said corresponding author Dipanjan Pan. Oligonucleotide sequences complementary to mpox DNA are attached to the gold nanoparticles, enabling the sensor to selectively detect the virus.
When the sensor comes in contact with the target DNA, the self-assembling structure of the nanocomposite transforms, resulting in a significant change in the material’s plasmonic response, the authors wrote. This change in response can be read using a relatively simple absorbance spectrometer. The researchers used ultraviolet-visible (UV-vis) spectroscopy to measure the response of the sensor in the presence of different concentrations of mpox, and found that sensor had a limit of detection of 7.6 pg µL−1, or 3.57 x 104 copies µL−1. Additionally, the nanomaterial had minimal cross-reactivity with other pathogens, such as SARS-CoV-2 RNA. The team further validated their method using X-ray diffraction, scanning transmission electron microscopy, surface-enhanced Raman microscopy and electromagnetic simulations. This study was published in Advanced Functional Materials.
“This is a major breakthrough in terms of how we manage the virus, as it is the first rapid test for mpox. While current caseloads are relatively low, as the weather warms and people become more active, cases could spike as they did last summer,” noted Pan. “But it’s also important to note that this new technology can help us to prepare for the next epidemic or even pandemic. With slight modification of the molecules used for targeting the genetic sequences, we will be able to specifically detect other viruses, bacteria or fungi using the same method.”
The development of a rapid method that does not require advanced instrumentation or special expertise could enable point-of-care diagnosis for mpox and other emerging diseases, potentially helping to catch cases faster and mitigate the spread in future outbreaks.