Ultrathin MXene nanosheet-based TiO2/CdS heterostructure as a photoelectrochemical sensor for detection of CEA in human serum samples

To develop highly accurate and ultrasensitive strategies is of great importance for the clinical measurement, in particular, the detection of cancer biomarkers. Herein, we synthesized an ultrasensitive TiO2/MXene/CdS QDs (TiO2/MX/CdS) heterostructure as a photoelectrochemical immunosensor, which favors energy levels matching and fast electron transfer from CdS to TiO2 in the help of ultrathin MXene nanosheet. Dramatic photocurrent quenching can be observed upon incubation of the TiO2/MX/CdS electrode by Cu2+ solution from 96-well microplate, which caused by the formation of CuS and subsequent CuxS (x = 1, 2), reducing the absorption of light and boosting the electron-hole recombination upon irradiation. As a result, the as-prepared biosensor demonstrates a linearly increased photocurrent quenching percentage (Q%) value with CEA concentration ranging from 1 fg/mL to 10 ng/mL, as well as a low detection limit of 0.24 fg/mL. Benefit from its excellent stability, high selectivity and good reproducibility of as-prepared PEC immunosensor, we believe that this proposed strategy might provide new opportunities for clinical diagnosis of CEA and other tumor markers.