A novel photoelectrochemical biosensing platform utilizing dual Type-II Bi2O3/CdLa2S4/Bi2S3 ternary heterojunctions as signal transduction materials and Cu2O nanosphere as a sensitizer for CA15-3 detection

Sensitive detection of CA15-3 is important for postoperative monitoring and early diagnosis of breast cancer. In this work, a photoelectrochemical (PEC) biosensing platform was constructed of CA15-3 by using Bi2O3/CdLa2S4/Bi2S3 ternary type-II heterojunction as the photoactive transduction material for sensitive detection, and the raspberry-shaped Cu2O nanospheres were exploited as the signal sensitizing tags. On one hand, the use of Bi2S3 as a sensitizer can effectively enhance the visible light excitation of the substrate material. On the other hand, Bi2S3 and Bi2O3/CdLa2S4 have the ability to create dual type-II heterojunctions with matched energy levels, which significantly enhances the separation and migration efficiency of the photogenerated carriers and effectively suppresses the recombination of the e(-)/h(+) pairs. Raspberry-like semiconducting Cu2O nanospheres can mediate the PEC process of the heterojunctions. An immunosensor was developed combining the signal transduction capacity of ternary heterojunction and the signal sensitizing effect of Cu2O nanospheres. The proposed PEC immunosensor showed good selectivity and stability for detecting CA15-3 (0.001 similar to 100 U/mL) with a detection limit of 0.0003 U/mL (S/N = 3). The constructed PEC immunosensor had potential applications in the clinical detection of CA15-3, and was expected to play a great role in the early diagnosis of breast cancer in the future. Moreover, in the design engineering of photoactive materials, the improvement of visible excitation and the enhancement of carrier separation efficiency have been realized simultaneously using a single material, which provides new ideas for the design of photoactive materials.