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

Herein, an antibody-free photoelectrochemical sensing platform was constructed for a sensitive carcinoembryonic antigen (CEA) assay by coupling CdIn₂S₄@In₂S₃ hollow microtubes (HMTs) and a polydopamine-mediated molecularly imprinted polymer (MIP). The CdIn₂S₄@In₂S₃ HMTs, synthesized by a Cd²⁺-exchange reaction on an MIL-68(In)-derived In₂S₃ surface with a large specific surface area, could promote the separation of photogenerated charge carriers by shortening the charge-transfer distance and enhancing light absorption, resulting in a stable photocurrent. Furthermore, the polydopamine-dependent MIP, electrodeposited on the surface of a 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 the target, CEA, the imprinted cavities could be re-embedded for inhibiting the diffusion of the electron donor <i>via</i> a typical steric-hindrance effect. Under optimized conditions, the developed sensor exhibited a wide linear range of 1 pg mL^-1-500 ng mL^-1, a low detection limit of 0.52 pg mL^-1, high selectivity and good stability. This sensor was also applied to the CEA analysis of real human serum, providing a feasible strategy for the selective detection of other biomarkers.