We recently described the OpenPCR project which is expected to make previously costly and difficult procedures like DNA amplification more accessible. Now, researchers at the University of Pennsylvania have opened the possibility of even more accessible molecular diagnostics by developing a self-heating, disposable microfluidic cartridge for isothermal nucleic acid amplification. Made out of the phase change material polymethyl methacrylate (PMMA), the cartridge (38 mm x 19 mm x 17 mm) consists of amplification chambers containing at least one thermal battery composed of magnesium iron alloy. When exposed to water, the magnesium exothermically produces hydrogen gas (released through vents in cartridge), magnesium hydroxide, and – of course – heat that can be used for the DNA amplification procedure.
In this case, the researchers maintained an optimal amplification temperature of between 60-65 degrees Celsius and controlled the rate of reaction by controlling the rate of water going into the reaction chamber. They found that they were able to amplify and detect (visually with a $2 UV LED shone into the reaction chamber, and molecularly through gel electrophoresis) as few as 10 copies of E. coli DNA. The researchers conclude their paper with a discussion of future work and applications:
Future modifications and improvements of the cartridge will include dry storage of [molecular] reagents in the amplification chamber. This can be achieved by encapsulating the dry reagents with paraffin, which will melt upon heating of the reaction chamber to the desired incubation temperature, move out of the way, and allow the hydration of the reagents. Another improvement may include equipping the cartridge with a solid phase membrane for the isolation, concentration, and purification of nucleic acid targets.
The fully integrated, non-instrumented, nucleic acid testing cartridge can be operated at the point of care by minimally trained personnel and can carry out all the necessary steps from sample to answer. With appropriate modifications of the reagents, the system can be used to detect various infectious diseases, monitor the health of individuals, provide a trigger for the administration of expensive or dangerous medications, and facilitate monitoring water and food quality. The device is suitable for use in the field, in resource-poor regions, especially in areas without reliable electric power, in remote areas, and at home.
Read about the molecular diagnostic cartridge in Lab on a Chip: A self-heating cartridge for molecular diagnostics…
Video about the type of amplification that the researchers reproduced in the cartridge: Loop-mediated isothermal reaction
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