Preparation Of Melanoidin/Fe³⁺ Nanozyme And Its Application In Food Detection And Sterilization

The implementation of the"Healthy China"strategy points to the future direction of socio-economic and food industry development.Meanwhile,it also places people’s health as a strategic priority.Food,as a source of energy and nutrition to sustain human life,provides essential guarantee of people’s survival and development.Therefore,food safety is not only related to people’s health and life safety,but also related to economic growth and social stability.However,food safety problems are still prominent at present.The innovation and application of food detection and sterilization technology provide technical support to solve food safety problems.In this paper,based on the metal chelating properties of melanoidin derived from natural food,the melanoidin-iron chelate nanozyme was successfully synthesized,which greatly improved the biocompatibility and safety of the nanomaterial.In addition,the morphology and properties of the nanozyme were fully characterized and applied to food detection and sterilization.The main research of this paper is as follows:1.Preparation and characterization of Melanoidin/Fe³⁺nanozyme:Firstly,the melanoidin was extracted from soybean sauce by ultrasonic crushing,alcohol precipitation,dialysis,freeze-drying,and other steps.Then,ferric ions(Fe³⁺)were chelated by electrostatic action to form Melanoidin/Fe³⁺.Transmission electron microscopy（TEM）showed that the morphology of Melanoidin/Fe³⁺and melanoidin was approximately spherical.The results of Fourier transform infrared spectroscopy（FTIR）,ultraviolet-visible spectroscopy（UV-vis）,X-ray photoelectron spectroscopy（XPS）,X-ray diffraction pattern（XRD）and Zeta potential（Zeta）indicated that the soybean sauce extract was melanoidin,and chelated with Fe³⁺through Fe-O bond to form stable complexes.The 625 nm UV absorption peak in UV-vis and the color change of the corresponding system indicated that melanoidin-iron chelate had peroxidase mimetic activity.Steady-state kinetic results showed that melanoidin-iron had excellent catalytic activity.The K_m values for 3,3’,5,5’-tetramethylbenzidine（TMB）and H₂O₂ were0.088 m M and 0.353 m M,respectively,which were much lower than those of natural horseradish peroxidase（HRP）and many nanozymes.2.Evaluation of the detection performance of Melanoidin/Fe³⁺nanozyme:In view of the excellent peroxidase mimic enzymatic activity of melanoidin-iron chelate,a sensing platform for detecting ascorbic acid（AA）based on enzyme-catalyzed colorimetric signal was constructed.The sensing platform can achieve rapid and accurate detection of AA in a wide range.By optimizing the conditions of the sensing platform,the performance evaluation results showed that under the optimal conditions,the standard curve of detection AA was y=0.00607x-0.00803（R²=0.998）,the detection concentration range was 10-100μM,and the detection limit was 1.19μM.The melanoidin-iron chelate had good anti-interference and stability,and had been successfully applied to the determination of AA in food and medicine.3.Evaluation of bactericidal performance of Melanoidin/Fe³⁺nanozyme:In order to verify the bactericidal capacity of melanoidin-iron chelate,methicillin-resistant Staphylococcus aureus（MRSA）was used as the bactericidal model.Firstly,the bactericidal effect of melanoidin-iron chelate was quantified by plate counting method.The results showed that the bactericidal rate of melanoidin-iron chelate was up to 99%at low concentration of H₂O₂（200μM）.In addition,the bactericidal effect of melanoidin-iron chelate was qualitatively determined by fluorescent live/dead bacterial staining,and the results were consistent with the plate counting method.Meanwhile,the results of SEM and electron spin resonance（ESR）showed that melanoidin-iron chelate catalyzed H₂O₂ to produce highly toxic superoxide radical,which could destroy bacterial cell membrane and cause leakage of bacterial cell contents resulting in the death of pathogenic bacteria.In the mouse model,the Melanoidin/Fe³⁺/H₂O₂ system can rapidly and efficiently sterilize without obvious biological toxicity.