Fabrication of polyoxometalate dispersed cobalt oxide nanowires for electrochemically monitoring superoxide radicals from Hela cell mitochondria.

An ultrasensitive electrochemical sensor is constructed by electrostatically adsorbing negatively charged hourglass-shape Cu-Polyoxometalate (POM) onto a positively charged CoO nanowires modified carbon cloth. The petaloid CoO nanowires have a large specific surface area that can well disperse open-structured Cu-POM to form Cu-POM@CoONWs@CC, which can maximumly expose catalytic active centers (Co²⁺ and Cu²⁺) and accelerate mass/charge transfer. In addition to the above advantages, the excellent electron exchange ability of Cu-POM and good conductivity of CoONWs@CC endow the sensor with good detection capability to H₂O₂ including a linear detection range of 0.05-1.4 μA μM^-1, a low detection limit of 0.022 μM, high sensitivity of 110.48 μA μM^-1, good selectivity and long-term stability. Due to the fast transformation of superoxide anion (O₂^∙-) to H₂O₂, the sensor can indirectly monitor the electron leakage resulting in the formation of O₂^∙- via detecting H₂O₂. Afterwards, Hela cell mitochondria were extracted from the living cells that cultured with different mitochondrial inhibitors and the release of O₂^∙- from the corresponding mitochondrial complexes was monitored by the sensor. Through comparing the current signals, we determined that complex I is probably the main electron leakage site. This work could provide meaningful information for the diagnosis of certain oxidative stress diseases.