In vivo monitoring of superoxide anion from Alzheimer's rat brains with functionalized ionic liquid polymer decorated microsensor

The superoxide anion (O₂ ^•−) is an important reactive oxygen species (ROS) in the brain system, which has been associated with the development of many neurological diseases, including Alzheimer's disease (AD). Herein, we introduced a carbon fiber microelectrode (CFME) based in vivo technique for specific and sensitive monitoring of the O₂ ^•− radical in the living brains of both normal and AD model rats. Compared with other reported superoxide dismutase (SOD) electrochemical biosensors, the microsensor presented in our work was featured in the coating of a functionalized ionic liquid polymer (PIL) onto PB nanoparticles (PBNPs) and carbon nanotubes (CNT). It was demonstrated that the cationic and carboxyl-rich PILs provided abundant interaction sites with SOD to prevent enzyme leakage from sensor, which was beneficial for the enhancement of sensitivity. Additionally, CCK-8 assay and autoxidation of pyrogallol tests showed that MCF-7 cells maintained a high viability after incubated with PIL and most of the SOD bioactivity was retained in the presence of PIL, which implied the PIL itself possessed an excellent biocompatibility. These properties allow the sensor to track the fluctuation of O₂ ^•− levels in vivo between normal and AD rats. This is the first report on application of functionalized PIL to reveal the O₂ ^•− related pathological process of AD.