NEW YORK (GenomeWeb) – Purdue University spinout company OmniVis is working toward a handheld point-of-care molecular assay for cholera bacteria in environmental samples that uses smartphone detection.
Meanwhile, the lab that generated that device is also developing new approaches for paper-based molecular testing for HIV.
Purdue assistant professor of biomedical engineering Jacqueline Linnes and her team have been developing assays intended to detect very rare nucleic acids — like cholera bacteria in water samples — by pairing a technology called particle diffusometry together with isothermal loop-mediated nucleic acid amplification (LAMP).
The diffusometry approach works because LAMP amplification creates long polymers of DNA molecules, which essentially slows down the particle motion so that diffusion is slower, Linnes said in an interview.
Traditional cholera detection methods are slow and require experts to run lab-based bacterial culture and PCR. Rapid tests exist, but these are typically not sensitive enough to detect low levels of pathogen in water.
As described in Scientific Reports this week, the team has developed its diffusometry-based approach into a cholera test that detects as few as 10 cholera cells from an environmental sample in 35 minutes, with no enrichment or sample preparation steps required. The researchers claim the test is tenfold more sensitive than current gold standard fluorescence detection of nucleic acid amplification.
Founded in late 2017 by members of the Purdue team, OmniVis will now take the diffusometry technology through to commercialization, Linnes said, in part through partnership with groups like the University of Florida's Emerging Pathogens Institute working in Haiti, and potentially with agencies like Doctors Without Borders.
Cholera is caused by ingesting Vibrio cholerae bacteria in contaminated water. Infection leads to intense vomiting and diarrhea with death typically caused by the ensuing massive, and rapid, dehydration.
Cholera is increasingly causing humanitarian crises in parts of the world. In Yemen, for example, an ongoing conflict has led to unsanitary water conditions and one of the worst cholera outbreaks in recorded history, according to Doctors Without Borders, with more than a million reported cases and over 2,000 deaths since 2016. And in Haiti, cholera is thought to have been introduced in 2010 to a population with no previous exposure and therefore no immunity. Subsequent outbreaks have infected more than 800,000 people and killed nearly 10,000. The disease is now considered to be endemic in Haiti.
OmniVis CEO and cofounder Katherine Clayton said in an interview that the company is now collaborating with researchers at Notre Dame University to perform field testing of its cholera assay in Haiti beginning in May of this year. Based on the findings, the company will then work to make the device intuitive and robust as it moves toward commercialization.
The company now has staff in Indiana as well as in Washington, DC — where Clayton and OmniVis' head of operations are serving as fellows at the Halcyon Incubator — and it is licensing two pending patents from Purdue University.
The company's current target customers are humanitarian aid organizations as well as water and sanitation agencies, predominantly focused on the 41 countries that have cholera outbreaks, Clayton said. The company plans to reach these customers through its website, scientific publications, and through networking, particularly in the Washington, DC area.
OmniVis is also focused on the World Health Organization goals for eradication of 90 percent of cholera cases by 2030. "Therefore, our current target customers remain in the humanitarian aid and water and sanitation space. … [and] we want to do a great job when we release our initial product, providing a robust solution to our initial market," Clayton said.
The technology development was funded in part through a Wireless Innovation Project award from the Vodafone Americas Foundation. And, through the Halcyon Incubator, the law firm Bracewell provides OmniVis with pro bono legal help to navigate the regulatory pathways that may be needed for water testing, Clayton said.
Importantly, although the biosensor provides new avenues to help prevent cholera outbreaks by detecting pathogens in water, the system itself is pathogen agnostic, and could potentially be used as a platform for detection of other pathogens.
Progress in Paper
Meantime, Linnes' lab is also developing a paper-based assay for HIV detection, with funding from the Bill and Melinda Gates Foundation and other sources. The assay incorporates wax valves that can be melted at will to open gates permitting fluid movement, among other innovations.
The device is about the size of a digital pregnancy test, Linnes said. It uses whole blood samples, deploying special membranes to separate out the HIV virus, then does viral lysis within the paper followed by LAMP amplification of viral RNA. All the reagents are dried into the paper using sugars, in a process called glassification.
Subsequently heating the wax valves at the side of the device pushes buffer into the test, making the sample run to a lateral flow detection strip. "So, [HIV] is easily detectable and it is all in one — add the sample and then just come back and check it later, so you don't have to do timed steps," Linnes said.
The heating of the device can be powered by a smartphone or other devices with micro USB inputs, she said.
The test could potentially be used to detect HIV much earlier than standard immunoassay-based testing, which requires a patient to develop antibodies to the virus. But, unlike PCR-based methods, which can detect HIV sooner, the test could be done at the point of care. Linnes said the team was recently able to do blood-based detection of HIV on the device using whole blood, and it is now replicating the experiment with the intention of publishing the data soon.
The lab has also recently won funding to develop an HIV viral load assay for use on its smartphone-based device, Linnes said, adding that as OmniVis builds up the technology around cholera detection, her lab is moving to detection of HIV and malaria using human blood samples. That work has recently been funded by the National Institutes of Health, but "OmniVis would be the ones to scale up and take that out of the lab," she said.