Disposable electrochemical immunosensor for simultaneous assay of a panel of breast cancer tumor markers

Abstract

The multiplexed immunosensor array was fabricated on a carbon electrode array containing three graphite working electrodes, which was prepared with screen-printed technology. This immunosensor was achieved using graphene (GR) to modify the immunosensor surface for accelerating electron transfer. The in situ synthesis of AuNPs on GR modified electrode surface aimed at the immobilization of capture antibody (Ab₁). With a sandwich-type immunoreaction, the alkaline phosphatase (ALP)-labeled antibody (Ab₂) functionalized Au cluster (AuCs)/GR was captured on the immunosensor surface to catalyze the hydrolysis of 3-indoxyl phosphate in substrate, which produced an indoxyl intermediate to reduce Ag ion. The silver deposition process was catalyzed by both ALP and AuCs/GR, which amplified the detection signal. The deposited silver was then measured by anodic linear sweep voltammetric stripping analysis in KCl solution. The increase of stripping peak currents was proportional to the logarithm value of the CA 153, CA 125 and CEA concentration in the range 5.0 × 10⁻³ to 50 U mL⁻¹ for CA 153, 1.0 × 10⁻³ to 100 U mL⁻¹ for CA 125, and 4.0 × 10⁻³ to 200 ng mL⁻¹ for CEA, with a limit detection of 1.5 × 10⁻³ U mL⁻¹ for CA 153, 3.4 × 10⁻⁴ U mL⁻¹ for CA 125, and 1.2 × 10⁻³ ng mL⁻¹ for CEA. The disposable immunosensor array and simple detection method for fast measurement of a panel of tumor markers avoided cross-talk and the need for deoxygenation for the electrochemical immunoassay, and showed significant clinical value for application in cancer screening, providing great potential for convenient point-of-care testing and commercial application.