Fabrication Of Novel Structured Nanoreactors And Their Application As Nanozymes For Colorimetric Biosensing

Enzymes usually exist in living organisms and play an important role in various catalytic reactions.Although natural enzymes have the advantages of high catalytic activity and strong specificity,they also have the defects of high purification cost,easy to be affected by the environment and difficulty in preservation.In order to overcome the defects of natural enzymes,the nanozymes emerge and become substitutes for biological enzymes.In this article,three kinds of silica-based nanoreactors with peroxidase-like activity were synthesized.These nanoreactors were utilized in the detection of bioactive molecules and were also successfully used in the real sample detection.The nano-enzyme Au@Co₃O₄/Ce O₂with peroxidase activity was prepared with chloric acid,cobalt nitrate and cerous nitrate as raw materials.In order to improve the stability of the nano-enzymes,a mesoporous silica shell was coated on the surface of the nano-enzymes,and the final nanomaterial Au@Co₃O₄/Ce O₂@m SiO₂was obtained.The prepared nanoenzymes were subjected to various characterization and performance tests and used to detect glucose,glucose-6-phosphate dehydrogenase,and glucose-6-phosphate.It is proved that the nano-enzyme has good catalytic activity.A nanoreactor Au@Co₃O₄/Ce O₂@m SiO₂with a unique yolk-shell structure was constructed,which exhibited superior peroxidase-like activity with lower K_mand higher affinity toward H₂O₂.The enhanced peroxidase-like activity was attributed to its unique structure and synergistic effects among multiple active components.Based on Au@Co₃O₄/Ce O₂@m SiO₂as nanozyme,an ultrasensitive detection of glucose was established with a detection range of 3.9 n M～1.03 m M and a detection limit as low as 3.2n M.The combination of Au@Co₃O₄/Ce O₂@m SiO₂with glucose-6-phosphate dehydrogenase（G6PD）realized the detection of G6PD.This detection method is sensitive,has a wide detection range of 5.0×10^-3～15 m U?m L^-1with the detection limit as low as3.6×10^-3m U·m L^-1.The s SiO₂@Ce O₂@PDA/Pt composite structure was obtained by coating a layer of PDA on the surface of s SiO₂@Ce O₂for loading Pt nanoparticles.A layer of mesopore silica was then coated on the surface of the composite structure.Finally,after the removal of PDA and CTAB by calcination,a nanoreactor with yolk-shell structure s SiO₂@Ce O₂/Pt@m SiO₂was prepared.The nanoreactor exhibited excellent peroxidase-like activity,and the kinetic studies show that the material had strong affinity to both TMB and H₂O₂.The method was used to detect H₂O₂,glutathione（GSH）and ascorbic acid（AA）with s SiO₂@Ce O₂/Pt@m SiO₂as nanozymes.The linear range of detection was wide and the detection limit was low.In addition,the nanozyme s SiO₂@Ce O₂/Pt@m SiO₂had been successfully used for the detection of glutathione and ascorbic acid in the candies and alkaline phosphatase in bovine serum.Co（OH）₂@m SiO₂was obtained by in-situ etching template Cu₂O@m SiO₂with Na₂S₂O₃in the presence of cobalt nitrate.The nanoreactor YS-Co₃O₄@m SiO₂with multi-shell structure was prepared after calcination.The catalytical performance and kinetic study of YS-Co₃O₄@m SiO₂showed that the nanoreactor had good peroxidase-like activity.Using YS-Co₃O₄@m SiO₂as nanozyme,a colorimetric method was established to detect hydrogen peroxide and bioactive small molecule uric acid.The linear detection range for uric acid was from 4 nmol/L to 866μmol/L.In addition,the detection method was applied to the detection of uric acid in saliva samples,which proved that the nanozyme had good selectivity and practicability.