A colorimetric and photothermal dual-mode immunobiosensor for chloramphenicol based on the β-NiOOH nanozyme-3,3′,5,5′-tetramethylbenzidine system

A colorimetric and photothermal dual-mode detection method based on β-NiOOH nanozyme-3,3′,5,5′-tetramethylbenzidine (TMB) system was established for chloramphenicol (CAP) content in fruit juice. Herein, a novel nanozyme β-NiOOH with high oxidase-like activity can directly and effectively catalyze the oxidation of colorless TMB to blue color TMB oxidation (oxTMB) without the presence of H₂O₂. Using a competition-type immunoassay, the oxTMB can induce not only an increase in the absorption peak intensity but also a photothermal effect under 808 nm laser irradiation, achieving dual-mode detection of CAP. The increase of absorbance at 652 nm and the increase of temperature generated by photothermal conversion are linearly correlated with the CAP content. Under the optimal conditions, the dual-mode detection shows a low limit of 0.0056 ng mL⁻¹ for the colorimetric method, and 0.0016 ng mL⁻¹ for the photothermal method. Moreover, the developed colorimetric and photothermal dual-mode immunobiosensor was successfully used to detect CAP in fruit juice with an acceptable recovery rate between 93.387% and 118.514%. This method has good repeatability, specificity, and accuracy, and provides an efficient approach for real-time detection of CAP in food safety analysis and detection platforms.