This paper demonstrates a reliable and durable method for in situ real-time determination of O2˙− based on direct electron transfer of Mn3(PO4)2, which acts as a superoxide dismutase (SOD). Mn2+ is ion-exchanged into zeolite–ZSM-5 microstructures, and further coated with poly(diallyldimethylammonium chloride) (PDDA). Direct electron transfer of Mn2+ is greatly facilitated by zeolite microstructures with the formal potential of 561 ± 6 mV vs.Ag|AgCl, which is just located between thermodynamic potentials of O2˙−/O2 and O2˙−/H2O2. The biomimetic catalytic activity of Mn3(PO4)2, together with the enhanced electron transfer of Mn2+ obtained at the zeolite electrode has provided a platform for determination of O2˙− with high selectivity, wide linear range, low detection limit, and quick response. On the other hand, the present Mn2+-ZSM/PDDA electrode shows relatively long-term stability, good reproducibility, and biocompatibility, which opens up a way to adhering cells directly onto the film surface for in situ monitoring of cellular species. As a sequence, the remarkable analytical performance of the present O2˙− biosensor, combined with the characteristics of the Mn2+-ZSM/PDDA electrode surface has established a novel approach for real-time determination of O2˙− released from living cells.
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