A sensitive unlabeled ratiometric biosensor was developed to the detection of cardiac troponin I (cTnI). This biosensor was established by using the glassy carbon electrode coated with graphene oxide to form a platform bonded with N, Zn co-doped graphene quantum dots (N, Zn-GQDs). The N, Zn-GQDs was successfully prepared as the raw materials of graphite powder and characterized. Antibodies of cTnI were bonded to the surface of N, Zn-GQDs as the nanoprobe by amide bonds. The signals of electrochemiluminescence (ECL) and differential pulse voltammetry (DPV) were exposed to decrease in the presence of cTnI, which caused the signal substance to move farther away from the electrode. It was found that the immune complex layer attenuated the intensity of ECL and DPV which could be used as the good overall signal for determining concentration of cTnI. The ratiometric biosensor had a good response to cTnI with the detection limit is 4.59 pg L-1 in the concentration range of 10-106 pg L-1. The developed method was evaluated for the detection of cTnI in human serum, and the obtained results were consistent compared to the reference values obtained by hospital standard enzyme linked immunoassay (ELISA) with 9.09%-11.1% of RSD. Our findings suggested that this ratiometric biosensor could be used to the detection of cTnI in human serum with lower cost and higher sensitivity, it also might be better potential application prospect based on N, Zn-GQDs to detect other biomarkers.
Keywords: Biomarker; Cardiac troponin I; Graphene oxide; Graphene quantum dots; Ratiometric biosensor.
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