An ultrasensitive chemiluminescent immunosensor for the detection of human leptin using hemin/G-quadruplex DNAzymes-assembled signal amplifier

In this work, we reported a sensitive chemiluminescent immunosensor for the detection of human leptin by using hemin/G-quadruplex DNAzymes to amplify detection signal. In this sensing system, the primary antibody (anti-human leptin) was firstly bound to the 96-well plates, and human leptin and biotinylated secondary antibody were successively combined to form sandwich-type immune complex through specific interactions. Then streptavidin labeled with hemin/G-quadruplex DNAzymes was assembled to the sandwich-type immunocomplex by streptavidin–biotin interaction. The DNAzymes exhibited an excellent catalytic activity to the chemiluminescent reaction of luminol with hydrogen peroxide in strong alkaline solution, leading to significant enhancement in response signal. Under the optimum conditions, the proposed immunosensor showed high sensitivity and selectivity with a low detection limit of 1.9 pg mL−1 and a wide linear response range of human leptin from 10 to 1000 pg mL−1. The immunosensor was used to detect human leptin in serum, and the results were in good agreement with the data obtained by conventional ELISA method.