GNP-CeO- polyaniline hybrid hydrogel for electrochemical detection of peroxynitrite anion and its integration in a microfluidic platform.

Peroxynitrite anion (ONOO) is an important in vivo oxidative stress biomarker whose aberrant levels have pathophysiological implications. In this study, an electrochemical sensor for ONOO detection was developed based on graphene nanoplatelets-cerium oxide nanocomposite (GNP-CeO) incorporated polyaniline (PANI) conducting hydrogels. The nanocomposite-hydrogel platform exhibited distinct synergistic advantages in terms of large electroactive surface coverage and providing a conductive pathway for electron transfer. Besides, the 3D porous structure of hydrogel integrated the GNP-CeO nanocomposite to provide hybrid materials for the evolution of catalytic activity towards electrochemical oxidation of ONOO. Various microscopic and spectroscopic characterization techniques endorsed the successful formation of GNP-CeO-PANI hydrogel. Cyclic voltammetry (CV) measurements of GNP-CeO-PANI hydrogel modified screen-printed electrodes (SPE) were carried out to record the current changes influenced by ONOO. The prepared sensor demonstrated a significant dose-dependent increase in CV peak current within a linear range of 5-100 µM (at a potential of 1.12 V), and a detection limit of 0.14 with a sensitivity of 29.35 ± 1.4 μA μM. Further, a customized microfluidic flow system was integrated with the GNP-CeO-PANI hydrogel modified SPE to enable continuous electrochemical detection of ONOO at low sample volumes. The developed microfluidic electrochemical device demonstrated an excellent sensitivity towards ONOO under optimal experimental conditions. Overall, the fabricated microfluidic device with hybrid hydrogels as electrochemical interfaces provides a reliable assessment of ONOO levels. This work offers considerable potential for understanding the oxidative stress-related disease mechanisms through determination of ONOO in biological samples.