A highly sensitive and reusable electrochemical immunosensor based on biofunctionalized graphene paper for the detection of the lung cancer-associated biomarker GM2AP.

A novel electrochemical immunosensor based on a four-armed star poly(glycidyl methacrylate) polymer containing epoxy side groups (FASPGMA)-coated commercial graphene-paper electrode was designed for the determination of GM2-activator protein (GM2AP). The FASPGMA polymer provided multiple linear polymer chains bearing epoxy side groups, all connected to a single branching point, and GM2AP-specific antibodies were covalently attached to epoxy-functional side groups, eliminating the requirement for supplementary reagents. Different chemical, electrochemical, and morphological tests were performed to investigate the production and characterization of the biosensing layer. By building an antibody-antigen immunocomplex, a highly selective detection was achieved, and the differential pulse voltammetry (DPV) method was utilized for the detection of GM2AP. Under optimal conditions, this approach had the advantages of excellent sensitivity (7.56 µA pg- 1 mL cm- 2) and a low limit of detection (LOD, 5.24 fg mL- 1). In addition, the designed immunosensor had good repeatability and reproducibility with low relative standard deviations (RSDs, < 5.03, n = 10). The repeatability and reproducibility test results were evaluated with T and F statistical tests, and a low pooled standard deviation (0.61%, n = 20) was also obtained. Furthermore, this approach demonstrated remarkable sensitivity and great anti-interference characteristics when it was applied to the analysis of different biomarker solutions. The high recovery rates in the quantification of GM2AP in the human serum samples, high sensitivity, and good stability of the immunosensor made it a potential approach for immunosensing of GM2AP in serum samples.