Investigation of peroxidase-like activity of monodisperse-porous metal oxide microspheres and their usage in the development of biosensors

Magnetic-monodisperse and porous microspheres were synthesized using hydrolysis and condensation method. The surface of microspheres was again covered with SiO2 structure. Gold nanoparticles (Au NP) were synthesized by Turkevich method and immobilized on SiO2@MagSiO2 microspheres. Glucose oxidase (GOx) was bound to Au NPs immobilized on SiO2@MagSiO2 microspheres. The physical and chemical properties of GOx@Au@SiO2@MagSiO2 microspheres were determined by Nitrogen adsorption-desorption method, Fourier transform infrared spectroscopy (FTIR), Scanning electron microscope (SEM), Transmission electron microscopy (TEM), Vibration sample magnetometry analysis (VSM), X-ray photoelectron spectroscopy (XPS) and X-Ray Diffraction Analysis (XRD) methods.In one-pot determination of glucose using peroxidase-like activity of GOx@Au@SiO2@MagSiO2 microspheres, the hydrogen peroxide produced by oxidation induced by immobilized GOx was reacted with the synthetic substrate 3,3',5,5'-tetramethylbenzidine (TMB). The peroxidase-like activity of GOx@Au@SiO2@MagSiO2 microspheres was investigated by changing the substrate concentration and pH. The selectivity against glucose and stability of GOx@Au@SiO2@MagSiO2 microspheres were also evaluated. The measurements were carried out using a UV-Vis spectrophotometer. Km and rm values were calculated by plotting Lineweaver-Burk and Michaelis Menten graphs with the developed nanozymes. The rm values for GOx@Au@SiO2@MagSiO2 and Au@SiO2@MagSiO2 microspheres were calculated as 11.1 and 47.84 μM / min, respectively. The calibration curves with the developed nanozme were obtained for direct determination of glucose concentration in human whole-blood without any pretreatment.