Target-Induced Horseradish Peroxidase Deactivation for Multicolor Colorimetric Assay of Hydrogen Sulfide in Rat Brain Microdialysis

Hydrogen sulfide (H₂S) is important for normal neural functions, which involves protecting neurons from oxidative stress and neuronal transmission modulation in brain. The detection of H₂S is significant for revealing its role in the diagnosis of various disease. In this study, a novel multicolor colorimetric assay based on the etching of gold nanorods (Au NRs) is proposed to evaluate H₂S level with the naked eye. This measurement relies on the catalytic oxidation of 3,3',5,5'-tetramethylbenzidine (TMB) via horseradish peroxidase (HRP) to produce TMB²⁺, which could etch the Au NRs quickly and accompany with a distinct color change. The vivid colors can be easily distinguished with the naked eye without any sophisticated instruments. The presence of H₂S can cause the deactivation of HRP, which affects the amount of TMB²⁺ produced and consequently affects the color changing of the system. Based on this mechanism, a simple but sensitive multicolor colorimetric assay is developed for H₂S detection with a linear range of 0.05-50 μM. The proposed method is demonstrated for monitoring extracellular H₂S in rat brain coupled with microdialysate.