Photoelectrochemical sensing Hela cell mitochondria released superoxide anion using a novel heterojunction formed by dispersing a wheel-shaped polyoxometalate on α-Fe2O3 nanoarray

Abstract

An ultra-sensitive photoelectrochemical (PEC) sensor was developed by immobilizing negatively charged wheel-shaped polyoxometalate (Co₁₆Mo₁₆P₂₄) clusters onto positively charged α-Fe₂O₃ nanoarray modified F-doped Tin Oxide glass (α-Fe₂O₃NRs|FTO) through electrostatic adsorption. α-Fe₂O₃NRs|FTO has a large specific surface area to well disperse {Co₁₆Mo₁₆P₂₄} clusters with excellent charge transfer behavior and PEC properties. {Co₁₆Mo₁₆P₂₄} and α-Fe₂O₃NRs have been verified to be perfectly matched in energy levels, which form a high-efficiency heterojunction for promoting an effective separation of photogenerated electron-hole couples. Based on that, the PEC sensor exhibits a wide linear range from 0.005 nM to 5000 nM for hydrogen peroxide (H₂O₂) detection, with a sensitivity of 12.51 μA·nM^-1, a detection limit of 0.093 nM, an excellent selectivity and long-term stability. Owing to the rapid conversion of superoxide radicals (O₂^•⁻) to H₂O₂, the sensor can therefore indirectly measure O₂^•⁻ derived from the electron leakage in mitochondrial electron transfer chain (ETC) by detecting H₂O₂ levels. To achieve a more reliable measurement, four inhibitors—rotenone, 2-monoacyltrifluoroacetone, antimycin A, and paclitaxel were utilized to induce the release of O₂^•⁻ from complexes I, II, III and IV in Hela cell mitochondria, respectively. By comparing the photocurrent changes caused by different inhibitors, we identify complex Ⅰ as the mostly likely site of electron leakage, which may provide meaningful information for the diagnosis of some oxidative stress diseases.