A portable nucleic acid detection system using natural convection combined with a smartphone

The development of portable nucleic acid diagnostic devices has the potential to expand the availability of molecular diagnostics into low-resource settings. One of the promising solutions for rapid and simple DNA amplification is the use of Rayleigh–Bernard natural convection which is caused by a buoyancy-driven thermal gradient of liquid when heated from below. This natural convection avoids the use of the complex and sophisticated hardware that is required for precise maintenance of temperature cycles in conventional PCR. We have developed a stand-alone convective PCR (cPCR) device linked to a smartphone for rapid detection of nucleic acids using natural convection heating. The device amplifies multiple DNA samples simultaneously using a custom-made heat block controlled by Bluetooth wireless communication. The entire device is highly portable, user-friendly, battery-operated and can provide target DNA amplification in less than 30 min. A detection limit of 2.8 × 10³ copies of a segment of lambda DNA was obtained when the two different fluorescently-tagged amplicons were collected magnetically and detected using the smartphone fluorescence reader. Thus, the combination of cPCR and multiplex fluorescence-based detection on a smartphone provides new opportunities for the development of affordable and portable molecular diagnostic devices for point-of-care situations or remote clinical settings.