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.

Automated summary

Developing highly accurate and ultrasensitive strategies is crucial for clinical measurements, especially in cancer biomarker detection. In this study, an ultrasensitive TiO2/MXene/CdS QDs heterostructure was synthesized as a photoelectrochemical immunosensor, utilizing the ultrathin MXene nanosheet to facilitate energy level matching and fast electron transfer. Incubating the TiO2/MX/CdS electrode with Cu2+ solution caused significant photocurrent quenching due to the formation of CuS and subsequent CuxS (x = 1, 2), reducing light absorption and increasing electron-hole recombination. The prepared biosensor exhibited a linearly increased photocurrent quenching percentage (Q%) with CEA concentration and a low detection limit of 0.24 fg/mL. Overall, this proposed strategy provides new opportunities for the clinical diagnosis of CEA and other tumor markers, offering excellent stability, high selectivity, and good reproducibility.