科研之友
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摘要
A novel pH-dependent immunosensor to detect tumor biomarker, carcinoembryonic antigen (CEA), was developed by using the pH-dependent AuNPs-Ab(2)-glucose oxidase-Concanavalin A as tracing tag and the albumin bovine V-Ab(1)/chitosan-AuNPs/three-dimensional kenaf stem-derived macroporous carbon (3D-KSCs) integrated electrode as signal collector based on a sandwich-type assay mode. The integrated 3D-KSCs electrode provided a large specific surface area to load a large number of Ab(1) effectively and the tracing tag with a lots of pH-dependent surface negative charges repulsed the negatively charged probe of Fe(CN)(6)(3) in a pH 9.0 solution. Accordingly, after a sandwich immunoreaction, the quantitative capture of tracing tag on the signal collector greatly hindered the electron transfer of Fe(CN)(6)(3) (/4) due to the electrostatic repulsion, which improved the sensitivity and selectivity of the immunosensors significantly. It was verified by electrochemical impedance spectroscopy. The resistance to charge transfer of Fe(CN)(6)(3) (/4) changed proportionally toward CEA concentration from 4 pg mL(-1) to 50 ng mL(-1) with a low detection limit of 1.3 pg mL(-1) (S/N=3) and a high sensitivity of 57.57 Omega ng(-1) mL. Based on human serum experiments, the sensing platform was proved to be suitable to assay CEA in a practical biosystem. This work not only gives a sensitive way to detect CEA but also provides a potential strategy for immunosensors based on 3D-KSC electrode and pH-dependent behavior.
