The interdisciplinary Duke team, which has "generally beenworking to develop new ways to diagnose infectious disease," according toGeoffrey Ginsburg, director of genomic medicine at Duke's Institute for GenomeSciences & Policy, has now "found a number of molecular biomarkers based onhost response to infection that can actually detect viral infection in hours ordays of when a patient becomes symptomatic."
This discovery, described in a paper published recently inthe online version of the journal AnalyticaChimica Acta, was made possible by a surface-enhanced Raman scattering(SERS)-based detection approach, referred to as "molecular-sentinel" (MS)plasmonic nanoprobes, designed to detect an RNA target related to viralinfection. The MS method, which was an achievement of Tuan Vo-Dinh, director ofthe Fitzpatrick Institute for Photonics at Duke, is described in the paper as"essentially a label-free technique incorporating the SERS effect modulationscheme associated with silver nanoparticles and Raman dye-labeled DNA hairpinprobes."
Vo-Dinh and colleagues developed an MS nanoprobe to detectthe human radical S-adenosyl methionine domain containing 2 (RSAD2) RNA targetas a model system for method demonstration. Hybridization with target sequencesopened the hairpin and spatially separated the Raman label from the silver surface,reducing the SERS signal of the label.
"The general idea that one could utilize these silvernanoparticles as a way to enhance and amplify the overall spectrum elicited inthe context of introducing light is something that Vo-Dinh has pioneered andworked on for quite some time," Ginsburg explains. "This is the first time ithas been down with an RNA probe, but he has published the same approachinvolving DNA technologies in the past."
That's where Ginsburg and his colleagues enter the picture,with their development of a method of measuring the host's response toinfection through RNA profiling. The human RSAD2 gene has recently emerged as anovel host-response biomarker for diagnosis of respiratory infections.
The team's results showed that the RSAD2 MS nanoprobesexhibited high specificity and could detect as low as 1 nM target sequences.
"With the use of a portable Raman spectrometer and total RNAsamples, we have also demonstrated for the first time the potential of the MSnanoprobe technology for detection of host-response RNA biomarkers forinfectious disease diagnostics," they concluded.
"Our work has really demonstrated the strength of the RNAsignal from the host response," says Ginsburg. "The fact that we can actuallydo this with an RNA molecule is an important step forward in detecting infections."
Next, the researchers will pursue the development of devicesthat measure multiple genome-derived markers and enable the more accurate andrapid diagnosis of infectious disease at the point of care, Ginsburg says.
"One can imagine having these tools in physicians' officesor even in a patient's home, and they may offer the fastest way to predict ifpeople are going to have upper respiratory infections or viruses with thatetiology," he says. "This would guide care decisions that will lead to moreeffective treatment and improved outcomes of antimicrobial therapy. Point-of-carediagnostics holds great promise to accelerate precision medicine, and moreimportantly, help patients in limited-resource settings gain access tomolecular testing."
There are several scenarios that these devices may be ableto address, Ginsburg says, such as "routine surveillance in high-risk areas ifthere is an outbreak."
"In the developing world, if this type of technology couldbe put in place at a low cost, then we really could have an impact on a majorcause of mortality around the globe," he says. "We're motivated to help solvesome of these problems, and that is the impetus for some of our work here."
Duke is currently in talks with "several groups" to bringsuch devices to market, Ginsburg says.
"We believe that a single molecule is not going to besignificant enough to achieve success in clinical trials, and it's also goingto be something that regulatory agencies will have a strong say over," henotes, "but I would say that in the next five to 10 years, point-of-caredevices like this one will vastly improve the way we approach diagnostics."
The research was supported by the U.S. National Institutesof Health, the Defense Advanced Projects Agency, the Department of Defense andthe Wallace H. Coulter Foundation.
