GNP-CeO₂- 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-CeO₂) 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-CeO₂ 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-CeO₂-PANI hydrogel. Cyclic voltammetry (CV) measurements of GNP-CeO₂-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⁻¹. Further, a customized microfluidic flow system was integrated with the GNP-CeO₂-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. Graphical abstract: