CdS/ZnIn2S4 heterojunction binding to HRP-catalyzed precipitation reaction for photoelectrochemically sensitive detection of IFN-γ.

By synthesizing CdS/ZnIn2S4 heterojunctions, we constructed a sensitive photoelectrochemical (PEC) sensing strategy based on aptamer structure switching and horseradish peroxidase (HRP)-induced biocatalytic precipitation reactions for interferon-gamma (IFN-γ) detection. To construct the PEC sensor, the complementary sequence (c-DNA) of the aptamer was fixed to a CdS/ZnIn2S4 heterojunctions modified tin fluoride doped tin oxide (FTO) electrode. In the absence of IFN-γ, HRP-labelled aptamers hybridized with c-DNA, and HRP catalyzed precipitation, i.e., 4-chloro-1-naphthol (4-CN) to benzo-4-chlorohexadienone (4-CD), which quenched the photocurrent of the electrode. In the presence of IFN-γ, HRP-labelled aptamers could not hybridize with c-DNA due to the formation of aptamer-IFN-γ complexes, allowing photocurrent to recover. The PEC sensor for IFN-γ detection had a wide linear range of 5 pM to 10 nM with a detection limit of 0.26 pM (signal-to-noise ratio = 3) under optimized experimental parameters. The high-performance CdS/ZnIn2S4 composite combined with the PEC sensing strategy has good stability and provide a promising sensing platform for the detection of cytokines. More importantly, the proposed PEC sensor could successfully detect IFN-γ in human serum samples. It was of great significance for clinical treatment.