Integrated slidable and valveless polymerase chain reaction-capillary electrophoresis microdevice for pathogen detection

An integrated slidable and valveless polymerase chain reaction (PCR) and capillary electrophoresis (CE) microdevice has been developed for pathogen detection on a portable genetic analysis microsystem. The proposed microdevice does not need any microvalve or external pneumatic actuators, thereby simplifying the chip fabrication and the chip operation process. The slidable PCR-CE chip consists of three glass layers: a channel wafer that includes a sample injection and CE microchannel, a Ti/Pt electrode-patterned resistance temperature detector (RTD) wafer, and a slidable plate in which a PCR chamber was fabricated. First, the slidable PCR plate was placed in the sample injection zone to load a PCR cocktail, and then moved to the PCR zone for thermal cycling. After PCR, the slidable PCR chamber was switched to the CE region for separation, the resultant amplicons were then analyzed by a miniaturized laser-induced fluorescence detector. Non-specific DNA adsorption was prevented by treating the glass surface with hydrophobic decyltrichlorosilane, and the leakage and evaporation of the PCR cocktail during the movement and PCR could be minimized by surrounding the slidable chamber with mineral oil. The target protein A gene (101 bp) of Staphylococcus aureus (S. aureus) was detected with a limit of detection (LOD) of 6 copies, even with a background of 1000-fold excess of Escherichia coli K12 (E. Coli K12) templates. This demonstrates a highly sensitive and selective genetic analysis was achieved on our slidable and valveless PCR-CE microdevice.