A label-free electrochemical immunosensor based on 11-mercaptoundeca-noic acid grafted chitosan and poly(N-methylaniline) for the detection of carcinoembryonic antigen

Carcinoembryonic antigen (CEA) is a cancer marker used for monitoring cancer treatment. Herein, a label-free electrochemical immunosensor for determining CEA concentration composed of the thiolated chitosan (tCHI) and the doped poly(N-methylaniline) (dPNMA) is proposed. The tCHI served as a support matrix for the immobilization of CEA antibodies (anti-CEA) and was prepared by using 11-mercaptoundecanoic acid (MUA) as a grafting agent on chitosan (CHI). The excellent electrical conductivity of the dPNMA was utilized as an electron transfer layer for the proposed immunosensor. The successful preparation of the tCHI was confirmed by the attenuated-total reflection Fourier transform spectroscopy (ATR-FTIR), X-ray photoelectron spectroscopy (XPS), and scanning electron microscopy (SEM). Cyclic voltammetry (CV), differential pulse voltammetry (DPV) and electrochemical impedance spectroscopy (EIS) were used to illustrate the performance of the proposed immunosensor. The determination of CEA concentration was relied on the decrease in the DPV current response with increasing CEA concentration from the creation of the antigen-antibody immunocomplex. The proposed immunosensor demonstrated a broad concentration range of 0.01 to 30 ng mL-1 with a low limit of detection (LOD) of 0.01 ng mL-1. In addition, the present sensor exhibited excellent selectivity, reproducibility, and longterm stability, suggesting its potential use to determine CEA in clinical immunoassay.

Automated summary

A label-free electrochemical immunosensor composed of thiolated chitosan (tCHI) and doped poly(N-methylaniline) (dPNMA) was developed for determining the concentration of carcinoembryonic antigen (CEA). The tCHI served as a support matrix for immobilizing CEA antibodies (anti-CEA), while the dPNMA provided excellent electrical conductivity as an electron transfer layer. The immunosensor demonstrated a broad concentration range of 0.01 to 30 ng mL-1 and a low limit of detection (LOD) of 0.01 ng mL-1, along with excellent selectivity, reproducibility, and long-term stability.