A durable non-enzymatic electrochemical sensor for monitoring H₂O₂ in rat brain microdialysates based on one-step fabrication of hydrogels

A non-enzymatic electrochemical H₂O₂ sensor was developed by in situ fabrication of biocompatible chitosan (CS) hydrogels, in which a specific recognition molecule for H₂O₂, thionine (TH), was stably immobilized via one-step electrodeposition. Electron transfer of TH was facilitated in the CS/GPTMS/TH (GPTMS: γ-glycidoxypropyltrimethoxysiloxane) hydrogels with an electron transfer rate constant (k_s) of 3.5 ± 0.1 s^-1. Meanwhile, TH in CS hydrogels maintained high electrocatalytic activity toward H₂O₂. The developed sensor exhibited a fast amperometric response toward H₂O₂ within 7 s and a linear response for H₂O₂ ranging from 5.0 × 10^-6 to 6.9 × 10^-4 M with a detection limit of 1.0 × 10^-6 M. In addition, the non-enzymatic electrochemical sensor exhibited long-term stability with a current decrease less than 5.0% in 18 days and good reproducibility with a small deviation of 7.2%. The remarkable analytical performance of the present sensor provided a promising model for durable monitoring of H₂O₂ in rat brain microdialysates, which is very useful for understanding the biological effects of H₂O₂ on the pathological and physiological processes.