Nanopipette confined hydrogel-catalyst networks for spatiotemporal monitoring of nanoplastics-induced oxidative stress in single cells.

Accurate and reliable monitoring of nanoplastics-induced oxidative stress at the single-cell level is essential for revealing the relevant biotoxicity and environmental health risks. Herein, a novel nanopipette sensor coupling Prussian blue-ferroferric oxide (PB-Fe3O4) nanozyme with highly hydrophilic hydrogel (Gel/PB-Fe3O4) was fabricated for the spatiotemporal monitoring of hydrogen peroxide (H2O2) fluctuations in single cells. The Gel/PB-Fe3O4 networks confined inside nanopipette provided the nanochannels, which were featured of good catalytic activity, high ion transport efficiency, and excellent antifouling capacity. The Gel/PB-Fe3O4 catalyzed the decomposition of H2O2 to generate hydroxyl radicals, which mediated the oxidation of 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid)diammonium salt (ABTS) substrate into the ABTS+. The directional migration of positively charged ABTS+ within the hydrogel nanochannels caused a significant enhancement of ion current rectification, realizing highly sensitive response toward H2O2 with a detection limit of 0.2 μM. Moreover, the proposed nanosensor enabled the spatiotemporal monitoring of polystyrene nanoplastics-induced H2O2 fluctuations in single 293T cells and A549 cells, indicating different oxidative responses of the two cell lines at the single-cell level. The developed nanopipette sensor offers a reliable platform for in-depth investigation on the biotoxicity mechanisms of nanoplastics.