Integrating Prussian Blue Analog-Based Nanozyme and Online Visible Light Absorption Approach for Continuous Hydrogen Sulfide Monitoring in Brains of Living Rats

The continuous detection of hydrogen sulfide (H₂S) is significant for revealing its role in the neuron protection and diagnosis of various diseases. In this study, a Prussian blue analog nanocubes (PBA NCs)-based oxidase-like mimic was synthesized and designed for continuous H₂S monitoring in a visible light absorption-based online optical detection platform (OODP). A specific chemical reaction between H₂S and the PBA NCs induce a decreasing oxidase-like activity of the PBA NCs, generating lower amounts of oxidized products of 3,3′5,5′-tetramethylbenzidine (TMB) and increasing the light intensity. By coupling the microdialysis techniques with OODP, excellent linearity in the range of 0.1–20 μM H₂S with a limit of detection of 33 nM and outstanding stability, reproducibility, and specificity in the response to H₂S were exhibited. By using this OODP, near real-time response and continuous H₂S measurements in the brains of living rats were successfully achieved. This new idea of integrating enzyme-like mimics with specific chemical reactions to form an online optical detection platform for continuous monitoring of neurochemical in the brain may be highly meaningful for thoroughly understanding the function of the brain.