A portable microfluidic analyzer for integrated bacterial detection using visible loop-mediated amplification

Bacterial contamination has become an important issue for food safety in recent years. Culture-based methods, though a gold standard for bacterial detection, usually take a long time for detection. Microfluidic-based molecular diagnosis can help to achieve rapid and accurate detection of bacteria; however, existing microfluidic systems have limited portability because bulky and complicated instruments are needed. In this study, a portable analyzer was developed to rapidly and simultaneously detect five types of foodborne bacteria (Staphylococcus aureus, Salmonella, Shigella, enterotoxigenic Escherichia coll., and Pseudomonas aeruginosa) on a centrifugal chip. Integration of the processes, including bacteria lysis, visible loop-mediated amplification (LAMP) and detection, was accomplished within 70 min. The analyzer has a compact size (151 x 134 x 110 mm) and two motors positioned on both sides of the centrifugal chip. The upper motor was used to generate a rotating magnetic field for lysing bacteria by bead-beating, whereas the lower motor rotated the chip on demand to execute the following processes: sedimentation of bacteria lysate, mixing of the LAMP buffer and bacteria lysate, and distribution of the mixture to the designated reaction chambers. The LAMP results were detected by a color sensor in the analyzer. Using this portable analyzer, similar detection sensitivities for the five bacteria were achieved compared to that of conventional LAMP in Eppendorf tubes. Considering the portability of the system and its simplicity of operation, the analyzer developed in this study may be of potential use in point-of-care applications.