Facile synthesis of nickel phosphate nanorods as biomimetic enzyme with excellent electrocatalytic activity for highly sensitive detection of superoxide anion released from living cells

In this work, the superoxide dismutase (SOD) biomimetic enzyme based on nickel phosphate nanorods [Ni(PO4)NRs] was prepared by a simple and eco-friendly hydrothermal method. After further introduction of carboxylated multi-walled carbon nanotubes (C-MWCNTs), the obtained Ni(PO4)NRs/C-MWCNTs nanocomposites were utilized as the novel electrode materials to construct the electrochemical superoxide anion radicals (O2•-) biosensor with excellent electrical conductivity and unprecedented catalytic performance. The morphology of Ni(PO4)NRs/C-MWCNTs nanocomposite was examined by scanning electron microscopy (SEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and Raman microscope, respectively. Under the optimum conditions, the proposed biosensor exhibits high sensitivity (5.67 × 104 μA/mM/cm2), low detection limit (0.097 μM at S/N = 3) and good selectivity to O2•-. In addition, the sensor can monitor O2•- released from MCF-7 cells with satisfactory results, which provides a great opportunity to apply it in the field of fundamental research and clinical diagnostics. Our results would promote Ni(PO4)NRs as the SOD biomimetic enzyme for designing biosensor and expand its various applications in biocatalysis and bioanalysis.