A smartphone-based point-of-care diagnosis of H1N1 with microfluidic convection PCR

For point-of-care diagnosis of influenza A (H1N1) virus, a convection polymerase chain reaction (PCR) in a capillary tube is developed for rapid nucleic acid amplification with a simple heating scheme. When the capillary tube is heated from the bottom end with a constant temperature, a stable temperature gradient across the tube generates a continuous circulatory flow which spontaneously transports the reagent through different temperature zones associated with the denaturing, annealing, and extension stages of PCR. A resistive heater, which is powered by a 5 V power supply, is used for heating the capillary tube. For real-time detection, Taqman probes labeled with FAM (Carboxyfluorescein) are used in amplification. A light-emitting diode positioned on the top of the capillary tube is used to shine the reagent for excitation. Real-time fluorescence detection is obtained with a smartphone whose camera is used to take the fluorescent images. A custom algorithm running on the smartphone is developed with Java for the analysis of images to interpret the detection result. The low cost and small device can be powered with a portable mobile power supply. In less than 30 min, H1N1 virus can be successfully detected with a reasonable detection limit.