In a proof-of-concept study, researchers from the University of California Los Angeles showed that they could detect the presence of DNA molecules using a new dye mixture and the sensors and optics of cellphones. The new system reads light created by the detector dye mixture, with a 10-times brighter signal, at a fraction of the cost of traditional laboratory equipment.
Typical diagnostic tests, such as ones for infectious diseases and genetic disorders, rely on amplifying the number of disease related nucleic acids like DNA or RNA with fluorescent dyes.
However, intercalator dyes, as they are called, which are small changes in light emitted from molecules that associate with DNA, are too subtle and unstable for regular cellphone camera sensors.
To address the problem, researchers including Aydogan Ozcan, Chancellors Professor of Electrical Engineering and Bioengineering, and Dino Di Carlo, professor of bioengineering and mechanical and aerospace engineering, found that by including a chemical additive they could stabilize the intercalator dyes and significantly increase the fluorescent signal above the background light level. This made it possible to incorporate the test with inexpensive cellphone based detection methods.
The new system was used in a process called loop-mediated isothermal amplification (LAMP), with DNA from lambda phage as the target molecule, and achieved results that were comparable to traditional laboratory equipment that costs tens of thousands of dollars more.
The team also developed a handheld reader to enable a cellphone to pick up on the light produced from dyes associated with amplified DNA while they were in well plates. The reader uses a cost-effective and portable fiber optic bundle that routed each well in the plates signal to a unique site of the camera sensor. This too produced results comparable to a standard benchtop reader, but at a significantly lower cost.
The researchers believe this reader could have applications for use with other fluorescence-based diagnostic tests and could be especially valuable in resource-limited settings.
Currently nucleic acid amplification tests have issues generating a stable and high signal, which often necessitates the use of calibration dyes and samples which can be limiting for point-of-care use, Di Carlo said in a prepared statement. The unique dye combination overcomes these issues and is able to generate a thermally stable signal, with a much higher signal to noise ratio. The DNA amplification curves we see look beautiful without any of the normalization and calibration which is usually performed, to get to the point that we start at.
The team, including lead author Janay Kong, a Ph.D. student in bioengineering, suggest that the novel dye combinations could be used in a number of other amplification tests because it can be universally used to detect any nucleic acid amplification.
Up next they plan to test the system on complex clinical samples and nucleic acids linked with pathogens like influenza.
The findings were reported in ACS Nano.
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Cellphone System Makes DNA Detection Affordable and Portable - Bioscience Technology