MIL-68(In)-derived CdIn2S4 @In2S3 hollow microtubes for sensitive molecularly imprinted photoelectrochemical CEA sensor

Herein, an antibody-free photoelectrochemical sensing platform was constructed for sensitive carcinoembryonic antigen (CEA) assay by coupling with CdIn₂S₄@In₂S₃ hollow microtubes (HMTs) and polydopamine-mediated molecularly imprinted polymer (MIP). Among them, CdIn₂S₄@In₂S₃ HMTs, synthesized by Cd²⁺-exchange reaction on MIL-68(In)-derived In₂S₃ surface with large specific surface area, could promote the separation of photogenerated charge carriers by means of the shortened charge-transfer distance and the enhanced light adsorption, resulting in a stable photocurrent. Meanwhile, polydopamine-dependent MIP, electrodeposited on the surface of CdIn₂S₄@In₂S₃ HMTs-modified ITO electrode, could elute the template molecules to effectively recognize CEA without complex and expensive antibody-antigen assembly processes. In the presence of target CEA, the imprinted cavities could be re-embedded for inhibiting the diffusion of electron donor via a typical stereo-hindrance effect. Under the optimized conditions, the above sensor exhibited wide linearity range of 1 pg mL⁻¹ to 500 ng mL⁻¹, low detection limit of 0.52 pg mL⁻¹, high selectivity and good stability. This sensor was also applied to CEA analysis in real human serum, providing a feasible strategy for selective detection of other biomarkers.