Electricity-Free Amplification May Expand Molecular POC Testing

The need for molecular point-of-care (POC) tests is perhaps greatest in low-resource settings, where logistical constraints, including unreliable electricity make most current molecular testing technologies unfeasible. Electricity-free, non-instrumented nucleic acid amplification (NINA) is nearing a reality with the development of a platform by researchers at the nonprofit PATH (Seattle), according to a study published online Nov. 26, 2014 in Plos ONE.

The group further showed that the heater can be paired with complementary, instrument-free technologies, such as a biplexed loop-mediated isothermal amplification (LAMP) assay and visual endpoint detection with nucleic acid lateral flow (NALF) and applied to the detection of HIV. The authors say that improvements over previous design iterations bring the technology from the “proof-of-concept stage to an optimized, robust alpha prototype.”

By bringing molecular testing for infectious diseases closer to the site of patient care researchers hope to overcome challenges with patient follow-up while improving upon the sensitivity of over-the-counter antibody-based tests by enabling detection of infections in the very early stages of disease.

The electricity-free, self-contained NINA system uses an inexpensive insulated thermos where the source of heat is a small-scale chemical reaction, rather than electrical power. In the latest iteration, the researchers utilize magnesium iron alloy for the exothermic reaction due to its high energy density and low cost ($.06 per test for heater reaction materials). The researchers demonstrate that the heater design has a thermal standard deviation less than 0.5 degrees C at operating temperature, which can range from an ambient temperature of 16 degrees C to 30 degrees C.

While the platform design is pathogen-agnostic, the researchers demonstrated the utility of the electricity-free molecular amplification and visual detection system using HIV-1 detection as a model analyte. A biplexed LAMP assay detected HIV-1 infection (and ß-actin for internal amplification control) with processed sample to result in less than 80 minutes. One outstanding need the authors hope to address is the need for “appropriate” sample preparation methods. The complete system, the authors say, will enable infectious disease case detection and surveillance well beyond centralized laboratories, at lower levels of the health care system.

Senior author Paul LaBarre, a senior technical officer PATH, tells DTET that the team will next focus on integrating the amplification hardware and the lateral flow detection hardware into a single disposable device. Additionally, they are working with collaborators to “optimize” resilient polymerase enzymes that enable reverse transcriptase amplification of unpurified samples.

LaBarre says that the commercialization timeline will be dictated, in part, by the need for additional funds. The general distribution plan will be disease specific, he says, with non-exclusive licenses for multiple isothermal methods and for multiple diseases likely. While the initial focus is sub-Saharan Africa and Southeast Asia, LaBarre envisions one day having a CLIA-waived molecular test available in local pharmacies or grocery stores.

Takeaway: By coupling new electricity-free nucleic acid amplification methods with complimentary, instrument-free assays and visual detection endpoints, point-of-care molecular testing for infectious diseases will be feasible in low resource settings.