Development of a Photoelectrochemical Microelectrode Using an Organic Probe for Monitoring Hydrogen Sulfide in Living Brains.

Hydrogen sulfide (HS) is an important bioactive molecule that plays a significant role in various functions, particularly in the living brain, where it is closely linked to cognition, memory, and several neurological diseases. Consequently, developing effective detection methods for HS is essential for studying brain functions and the underlying mechanisms of these diseases. This study aims to construct a novel photoelectrochemical (PEC) microelectrode Ti/TiO@HSP for the quantitative monitoring of HS levels in the living brain. The PEC microelectrode Ti/TiO@HSP is formed by covalently bonding a specifically designed organic PEC probe HSP, which possesses a D-π- structure, to the surface of TiO nanotubes generated via in situ anodic oxidation of titanium wire. The PEC probe HSP can effectively react with HS and generate significant photocurrent response under long-wavelength excitation light (560 nm), thereby achieving quantitative detection of HS. The sensor demonstrates high sensitivity and good selectivity. In vivo experiments utilizing the PEC microelectrode Ti/TiO@HSP enable the monitoring of dynamic changes in HS levels across various regions of the mouse brain. The findings reveal that in normal mice, the concentration of HS in the hippocampus is significantly higher than in the striatum and cerebral cortex. Additionally, following propargylglycine drug stimulation, HS concentrations in different brain regions were observed to decrease, with the most substantial reduction noted in the hippocampus. This suggests that cystathionine γ-lyase (CSE) is the primary enzyme responsible for HS production in this area, while the striatum exhibits a less pronounced decrease in HS concentration, indicating a reliance on alternative enzymatic pathways for HS production. Therefore, this study not only successfully develops a high-performance HS detection sensor but also provides new experimental tools and theoretical foundations for further exploring the roles of HS in neurophysiological and pathological processes.