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

Abstract

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 via 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.