Improved EIS performance of an electrochemical cytosensor using three-dimensional architecture Au@BSA as sensing layer

An ultrasensitive electrochemical cytosensor for quantitative determination of carcinoembryonic antigen (CEA)-positive tumor cells was developed using three-dimensional (3D) architecture Au@BSA microspheres as sensing layer with the conjugation of targeting molecule monoclonal anti-CEA antibody (anti-CEA). The prepared Au@BSA microspheres exhibited satisfactory biocompatibility for cell proliferation via evaluation from thiazolyl blue tetrazolium bromide (MTT) assay, providing a suitable platform for cell adhesion study. Attributed to the excellent electroconductivity of Au@BSA, amplified electrochemical signals could be obtained and resulted in the greatly enhanced detection sensitivity. Electrochemical testing techniques including electrochemical impedance spectroscopy (EIS), differential pulse voltammetry (DPV), and cyclic voltammetry (CV) were applied to assess the optimal conditions, specificity, and detection performance of as-fabricated cytosensor. The attachment of CEA-positive BXPC-3 cells onto the anti-CEA immobilized sensing layer led to the increased EIS responses, which changed linearly in the cell concentration range from 5.2 × 10¹ to 5.2 × 10⁷ cells mL^-1 with a detection limit of 18 cells mL^-1. This proposed cytosensing strategy revealed high specificity to CEA-positive cells, acceptable intra-assay precision, excellent fabrication reproducibility with the RSD of 3.5%, and good stability owing to the outside BSA biocompatible layer, developing a promising technique for early monitoring of tumor cells at a lower level.