A novel FRET biosensor based on four-way branch migration HCR for Vibrio parahaemolyticus detection

A versatile and powerful fluorescence resonance energy transfer (FRET) biosensor based on four-way branch migration hybridization chain reaction (HCR) was proposed for the detection of Vibrio parahaemolyticus (V. parahaemolyticus). In the system, two partly complementary hairpin structures of H1 and H2, and an assistant DNA strand (R) were designed. H1 was labeled with carboxyfluorescein (FAM) as fluorophore donor, and H2 was labeled with tetramethylrhodamine (TAMRA) as fluorophore acceptor. When target DNA was presented in the system, it would firstly bind with the assistant DNA to form a short double-strand DNA (dsDNA), and subsequently trigger the four-way branch migration HCR, which would produce long nicked dsDNA concatamer and bring a good deal of FAM and TAMRA in close proximity, so that dramatic FRET signals could be achieved. With the assistance of well-designed four-way branch migration HCR circuits, this FRET biosensor exhibited a superior detection capability, which could detect 0.067 nM target DNA and as low as 10 CFU mL(-1) of V. parahaemolyticus. To our knowledge, it is the first time that a four-way branch migration HCR strategy for signal amplification has been adapted to the FRET biosensor, which might show great potential in food safety and clinical diagnosis.