Efficient Electrochemical Microsensor for In Vivo Monitoring of H2O2 in PD Mouse Brain: Rational Design and Synthesis of Recognition Molecules

Hydrogen peroxide (H2O2), one of the most stable and abundant reactive oxygen species (ROS), acting as a modulator of dopaminergic signaling, has been intimately implicated in Parkinson's disease, creating a critical need for the selective quantification of H2O2 in the living brain. Current natural or nanomimic enzyme-based electrochemical methods employed for the determination of H2O2 suffer from inadequate selectivity and stability, due to which the in vivo measurement of H2O2 in the living brain remains a challenge. Herein, a series of 5-(1,2-dithiolan-3-yl)-N-(4- (4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)phenyl)pentanamide (DBP) derivatives were designed by tuning the substitute groups and sites of a boric acid ester, which served as probes to specifically react with H2O2. Consequently, the reaction products, 5-(1,2-dithiolan-3-yl)-N-(4-hydroxyphen-yl)pentanamide (DHP) derivatives, converted the electrochemical signal from inactive into active. After systematically evaluating their performances, S-(1,2-dithiolan-3-yl)-N-(3-chloro-4-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)phenyl)pentanamide (o-CI-DBP) was finally identified as the optimized probe for H2O2 detection as it revealed the fastest reaction time, the largest current density, and the most negative potential. In addition, electrochemically oxidized graphene oxide (EOGO) was utilized to produce a stable inner reference. The designed electrochemical microsensor provided a ratiometric strategy for real-time tracking of H2O2 in a linear range of 0.5-600 mu M with high selectivity and accuracy. Eventually, the efficient electrochemical microsensor was successfully applied to the measurement of H2O2 in Parkinson's disease (PD) mouse brain. The average levels of H2O2 in the cortex, striatum, and hippocampus in the normal mouse and PD mouse were systematically compared for the first time.