Supramolecular hydrogel mediated photoelectrochemical/electrochemiluminescence dual-mode biosensor based on TiO2/CdIn2S4/CdS for sensitive detection of enrofloxacin

In this paper, a new photoelectrochemical (PEC) and electrochemiluminescence (ECL) dual-mode biosensor based on TiO₂/CdIn₂S₄/CdS (TO/CIS/CdS) composite and a unique supramolecular hydrogel quenching probe was constructed for sensitive detection of enrofloxacin (ENR). Firstly, TO/CIS/CdS showed excellent PEC and ECL dual signals, which was applied to dual-mode sensing and detection. By using cyclic amplification and magnetic separation techniques, target ENR was converted into a large number of product chains with ZnO nanoparticles (NPs), and acidolysis was carried out to obtain zinc ions. Then, a layer of supramolecular hydrogel with good biocompatibility and stability was formed on the electrode using the ligand interaction between adenosine monophosphate (AMP) and Zn²⁺. The poor electrical conductivity and light transmission of the hydrogel layer make it an excellent double-quenching material for PEC and ECL signals, which was used for sensitive dual-mode detection of ENR. The cyclic amplification technique in a homogeneous solution was utilized to improve the sensitivity of detection while avoiding the complex electrode-modification process, thus effectively improving efficiency and stability of the sensor. The detection range of the PEC mode can reach 0.1 pg mL^˗1 to 1 μg mL^˗1, and the limit of detection (LOD) is 35 fg mL^˗1. The detection range of the ECL mode is from 1 pg mL^˗1 to 1 μg mL^˗1, and the LOD is 0.14 pg mL^˗1. Thus, a new multifunctional biosensor utilizing TO/CIS/CS and the unique hydrogel quencher was opened up, which has great potential for application in the field of food safety and environmental monitoring.