Magnetic bead-based photoelectrochemical immunoassay for sensitive detection of carcinoembryonic antigen using hollow cadmium sulfide.

Herein a versatile photoelectrochemical (PEC) immunoassay platform for sensitive and specific screening of tumor biomarkers (carcinoembryonic antigen; CEA) was innovatively designed using hollow cadmium sulfide (H-CdS) as photoactive matrix based on immunomagnetic separation. Experimental results reveal that the hollow-structure prepared by template hydrothermal-etching method endowed the CdS with better photocurrent intensity compared to the traditional CdS nanoparticles. Upon addition of target CEA, a sandwiched immunoreaction was carried out between anti-CEA capture antibody-conjugated immunomagnetic bead (IMB) and horseradish peroxidase (HRP)-labeled anti-CEA detection antibody, accompanying the immunocomplex formation of the IMB-antibody/CEA/HRP-labeled antibody (IMB-CEA-HRP). Followed by magnetic separation, the carried HRP on the sandwich structure triggers enzymatic bioetching of H-CdS, thus resulting in decreasing photocurrent intensity. The H-CdS-based PEC sensing system exhibited satisfying photocurrent responses toward target CEA within the working range from 0.02 ng mL-1 to 50 ng mL-1 at a low detection limit of 6.12 pg mL-1. Combined with magnetic immunoassay, this sensing platform has the advantages of high precision, great anti-interference ability, and acceptable accuracy. Overall, this research not only provides an efficient strategy for the activity of CdS with a well-defined hollow-nanostructures but also sheds light on the development of enzyme-triggered bioetching technology for traditional PEC immunoassay.