Study On Glucose Oxidase-like Activity Of Gold Nanoparticles And Its Complex

As a typical nanozyme,Gold nanoparticles（AuNPs）are widely used for catalyzing due to their various enzyme-like activities,including glucose oxidase-like activity,peroxidase-like activity,and superoxide dismutase-like activity,etc.However,the low catalytic efficiency,high surface energy and unstable in reaction system have limited its applications.To overcome these disadvantages,this research constructed complexes of AuNPs loaded on SiO₂microspheres and demonstrated their glucose oxidase-like activity.The results were described briefly as follows:（1）AuNPs of different sizes were synthesized using trisodium citrate as reducing agents and stabilizer ligands;SiO₂microspheres were synthesized and modified with amination at the same time,and then different Silica-Gold complexes（SiO₂-Au,SiO₂@Au）were prepared.The UV-visible spectrums and TEM images confirmed that AuNPs,SiO₂-Au and SiO₂@Au were synthesized successfully with uniform size and well dispersion.The average diameter of different AuNPs was about 15 nm to 80 nm,while the average diameter of AuNPs on SiO₂-Au and SiO₂@Au was about 15 nm and 5 nm,and the density of AuNPs on SiO₂@Au is much greater than that of SiO₂-Au.（2）AuNPs,SiO₂-Au and SiO₂@Au demonstrated glucose oxidase-like activity,which could use dissolved oxygen to catalyze the oxidation of glucose and generate hydrogen peroxide.The glucose oxidase-like activity decreased as the particle size increased,and enzyme-like activity of 15 nm AuNPs was the highest.（3）The factors affecting the glucose oxidase-like activity of AuNPs,SiO₂-Au and SiO₂@Au were studied.The results showed that the optimal p H of AuNPs,SiO₂-Au and SiO₂@Au were 8,and the glucose oxidase-like activity of them became higher with the increase of temperature in a certain range;the kinetic study results confirmed that the initial reaction velocity of them was dependent on the substrate concentration,and its kinetic mechanism conformed to the Michaelis-Menten model.The k_cat/K_mof SiO₂-Au and SiO₂@Au were better than AuNPs,while SiO₂@Au demonstrated higher catalytic activity with equal amount of gold atoms.（4）The stability and substrate specificity of SiO₂@Au have been investigated.Compared with natural glucose oxidase,SiO₂@Au persisted higher catalytic activity at high temperature,neutral and alkaline environments.The storage stability of SiO₂@Au was better than natural glucose oxidase.Other sugars in beverages did not interfere the detection of glucose based on SiO₂@Au,and the detecting results were consistent with the natural glucose oxidase method.Therefore,SiO₂@Au was promising to detect the glucose content in actual samples.In summary,this research synthesized AuNPs and its complex（SiO₂-Au,SiO₂@Au）with glucose oxidase-like activity,while the SiO₂@Au exhibiting the highest catalytic activity.Compared with natural glucose oxidase,SiO₂@Au demonstrated higher thermal and storage stability,and could be applied to detect the glucose content in actual samples.This research could broaden the application of gold nanoparticles and also provide an example for the practical use of nanozymes.