Disposable electrochemical immunosensor based on r-GO/Thi/AuNPs nanocomposites for detection of NSE

In this work, a disposable electrochemical immunosensor based on screen-printed electrode with modification of r-GO/Thi/AuNPs nanocomposites was developed onto the chromatography paper for detection of NSE. The electrochemical immunosensor consists of two sheets of chromatography paper and one double-side tape. The carbon working electrode (WE) was screen-printed onto the hydrophilic channels separated with wax-printed hydrophobic areas on one sheet, and the counter electrode (CE) and the Ag|AgCl reference electrode (RE) were on the other sheet. The synthesized r-GO/Thi/AuNPs nanocomposites and the anti-NSE were successively coated on the carbon working electrode so as to provide an electrochemical interface sensitive to NSE. Finally, the above three electrodes were integrated using the double-side tape. Thus, a capillary-driven flow is generated through the porous medium to connect the three electrodes in the same solution cell on account of the hydrophilic fiber surface. And the modification of the r-GO/Thi/AuNPs nanocomposites on the immunosensor, in which Thi functioned as electrically active substances to generate an electric current and r-GO can accelerate the transfer of electrons to amplify the signal, make it possible to detect NSE through the lable-free immunoreactions. When the immunosensor was incubated with the target NSE antigen, the peak currents of DPVs were decreased because the formation of antibody-antigen immunocomplex onto the working electrode resulted in the enhanced steric hindrance blocking the electron transfer of Thi. Additionally, the peak currents of DPVs decreased with the NSE concentrations increasing. There is a good linear relationship between the peak currents and the NSE concentration in the ranges of 0.01-100 ng/mL and the limit of detection was 10 pg/mL (S/N=3). The results indicated that the immunosensors enabled relatively wide linear range and a low detection limit for NSE.