A Biocompatible Microsensor Based on a Cation-Selective Nanoporous Conductive Hydrogel for Stable Electrochemical Sensing of Dopamine in Mouse Brain

Electroanalytical methods have demonstrated unique advantages in the real-time, <i>in situ</i> dynamic monitoring of brain neurotransmitters. Nevertheless, these methods continue to encounter specific challenges, including the passivation of microsensors resulting from nonspecific adsorption of proteins. This study developed a crosslinked hydrogel coating composed of aniline (AN), 3-aminophenylboronic acid hydrochloride (ABA), and tannic acid (TA). The coating was prepared through a one-step amperometric method (a constant potential of +1.0 V for 150 s), utilizing hydrophilic three-dimensional nanonetworks. This approach successfully addressed the challenge posed by the uneven application of hydrogel coatings and their propensity to delaminate. It has been demonstrated that the highly hydrophilic nanoporous structure of the hydrogel can resist protein adsorption on the surface of carbon fibers, thereby enhancing the stability of neural electrodes. In addition, the negatively charged TA in the hydrogel displays excellent selectivity toward dopamine (DA). The microsensor demonstrates high detection sensitivities of 0.77 and 0.28 nA μM^-1 within the detection ranges of 0.02-0.5 and 0.5-20 μM, respectively, with a low detection limit of 16 nM. Finally, the dynamics of DA in the mouse brain was successfully monitored <i>in vivo</i> by the implanted microsensor in real time. Furthermore, the immunohistochemistry result indicates that the expression of GFAP and Iba-1 around the microsensor was reduced by 55.2 and 41.7%, respectively, after 21 days of implantation into brain tissue, compared to CFE. This demonstrates that the microsensor exhibits good biocompatibility. The present study proposes a straightforward methodology to construct antifouling interfaces, with the objective of resisting protein adsorption in complex biological environments. The study demonstrates the exceptional properties of hydrogel materials in the preparation of electrochemical sensors.