Ratiometric Electrochemical Immunosensor Based on L-cysteine Grafted Ferrocene for Detection of Neuron Specific Enolase

Abstract

In order to realize the ultra sensitive detection of Neuron specific enolase (NSE) in human serum, we chose electrochemical immunosensor as a simple analytical method. During the experiment, we found that the peak value signals of Cu-MOFs-Au and Fc-L-Cys were significantly changed at −0.20 V and 0.20 V potentials by DPV. So a ratiometric electrochemical immunosensor for quantitative analysis of NSE was prepared for Cu-MOFs-Au as the electrode sensing surface and Fc-L-Cys as the label of Ab2. The data and performances of the immunosensor were tested and analyzed by DPV. Cu-MOFs not only provide the required signal for the immunosensor, but also have a large specific surface area, which can provide more sites for the placement of Au nanoparticles. L-cysteine (L-Cys) can prevent a large amount of Fc-COOH leakage, so that Fc+ can stably provide another required signal. With the beefing up of NSE concentration, redox peak of Cu-MOFs-Au decreased and that of Fc-L-Cys raised. The ratio (ΔI=ΔICu/ΔIFc) of two different signals was linear with the logarithm of NSE concentration in a certain value range. In brief, with the optimized experimental conditions, the immunosensor showed excellent performance in the concentration range of 1 pg/mL to 1 μg/mL, and the detection limit was 0.011 pg/mL. Compared with other immunosensors, it showed an unexpected high sensitivity. This method also provided a new idea for the ultra sensitive quantitative detection of other biomarkers.