Enzyme-free multicolor biosensor based on Cu2+-modified carbon nitride nanosheets and gold nanobipyramids for sensitive detection of neuron specific enolase

In this work, we have synthesized Cu2+-modified carbon nitride nanosheets (Cu2+-C3N4) as peroxidase mimic catalytic substance, which is more active than the horseradish peroxidase enzyme in extreme environments. Gold nanobipyramid (Au NBP) is a good chromogenic substrate for multicolor display because the longitudinal plasmon bands of AuNRs can be easily tuned by adjusting their aspect ratios and used as an excellent indicator for colorimetric detection of immunoassays. The generation of TMB2+ from sandwich complex (peroxidase-like catalysis) efficiently etches Au NPBs to produce multicolor variations from brown to olive, green, blue, purple, purple, red, pink, and colorless in presence of varied concentrations of neuron specific enolase (NSE). The experimental results show that the colorimetric detection ranging from 312.5 to 20,000 pM with a detection limit of 92.8 pM, which is higher than other multicolor based sensors. The Cu2+-C3N4 nanosheets and Au NBPs based colorimetric visual (naked eye) semi-quantitative method as a potential platform towards the detection of important biomolecules in clinical and therapeutic applications. The proposed method is simple, low-cost and enzyme-free to detect NSE for the first time.