Characterization And Application Of Vitamin C Modified Fe₃O₄ MNPs As Peroxidase Mimetics

Because of natural enzyme characteristics of nanoparticles,nanozymes have been widely used in biosensor,immunoassay,therapeutic application and environmental protection due to its strong environmental tolerance,low production cost and repeatability.However,the shortcomings of nanozymes,such as low catalytic activities,single enzyme species and lower selectivity,limit its further application.At present,there are some methods to enhance their efficiencies,such as cutting down the particle size,changing morphology,modificing surface,doping other ions,formating alloy and so on.Novertheless,It is still necessary to find more novel nano-enzymes with highly activities of nano-enzymes,develop more extensive applications,and conduct deeply mechanism studies.Therefore,this paper intends to explore a new method to enhance the activity of nanozymes peroxidase with Fe₃O₄ MNPs mimic enzyme as the template,explore the promotion mechanism and new application direction.In this paper,vitamin C?V_C?was used to modify the surface of Fe₃O₄ MNPs by oxidative polymerization,and V_C/Fe₃O₄ MNPs was obtained.The physical and chemical properties of the materials were characterized by TEM,XRD,FTIR,TGA and Zeta potential.The results showed that the synthesized material was indeed nanometer Fe₃O₄ and V_C films successfully were coated on the surface of Fe₃O₄ MNPs where the mass ratio of V_C/Fe₃O₄ MNPs is VC:Fe₃O₄=1:8.The modification of V_C changes the electrical property of the material,In the buffer solution of sodium acetate at pH=3.6,the electrical property of the material changes from positive to negative,and the Zeta potential changes from 17.3 mV to-17.6 mV,which makes the material have a better affinity with the positive chromogenic substrate.The comparison of catalytic activities indicated that V_C could significantly enhance the peroxidase activity of Fe₃O₄ MNPs.It is proved that the catalytic reaction was in accordance with the ping-pang mechanism through the study of steady state kinetics.By exploring the steady-state kinetics and analyzing the effects between leached iron ions and the catalyston the catalysis,it is concluded that the enhancement of the activity of V_C on Fe₃O₄ MNPs peroxidase is caused by three synergistic effects,including:?1?the modification of V_C promoted the affinity of Fe₃O₄ MNPs with two substrates?H₂O₂ and TMB?.?2?V_C as a chelating agent increased the release of Fe²⁺into the solution enhancing Fenton reaction.?3?the reduction of V_C promoted the Fe²⁺/Fe³⁺cycle on Fe₃O₄ MNPs surface.In addition,V_C/Fe₃O₄ MNPs have good stability which still could keep more than 80%activity after using in the range of 4-10pH and temperature range from 0 to 60?.Finally,three colorimetric methods for the determination of H₂O₂,glucose or nitrobenzene,respectively,were established using V_C/Fe3O4 MNPs as the catalyst.As low as 0.29?M H₂O₂ with a wide linear detection range of 0.5-100?M H₂O₂,and0.288?M glucose with a linear detection range of 0.5-25?M could be detected which showed its good selectivity.The detection method was highly sensitive in sensing H₂O₂and glucose.In addition,the colorimetric detection method of nitrobenzene was also studied with the detection limit of 0.38 mM in the detection range of 0.5-10 mM,indicating that the adaptation for colorimetric detection of nitrobenzene compounds.