Heparin-mediated Synthesis Of Metal Nanozymes And Their Applications

Heparin(Hep),a natural biopolymer,has been recognized as a natural template for the synthesis of metallic nanoparticles(MNPs)because of their outstanding biocompatible and biodegradable properties as well as carboxyl groups with metal ion-binding affinities.In this study,Hep was chosen as the nucleation template to synthesize Pd nanoparticles(Hep-Pd NPs)and Pt nanoclusters(Hep-Pt NCs).They were applied to colorimetric assays of protamine(Pro)and glucose(Glu).These colorimetric assays possess several advantages involving high sensitivity,short response as well as visibility.The content of this research is as follows:In Chapter 3,Hep-Pd NPs with the size distribution ranging from 3.1 to 3.5 nm,was synthesized by adopting Hep as the stabilizer and dimethylamine borane(DMAB)as the reductant.The most efficient nanozyme synthesized with the[Na₂Pd Cl₄]/[Hep]of 5,consists of 70.8%metallic Pd⁰ and of 29.2%Pd²⁺species.The K_m values are 0.036m M for the enzyme substrate 3,3',5,5'-tetramethylbenzidine(TMB),and 78 m M for H₂O₂.Pro shows strong binding affinity for Hep-capped Pd nanozyme.This results in the aggregation of Hep-Pd NPs,which inhibits their peroxidase-mimicking property.Based on this finding,a quantitative assay was developed for colorimetric determination of Pro.Response is linear in the 0.02 to 0.8?g/m L concentration range,and the limit of detection(LOD)is 0.014?g/m L.In Chapter 4,Hep serves as both reductant and stabilizer for one-pot synthesis of ultrasmall Pt NCs with the mean size of 1.9 nm.The surface remaining Hep enhances the affinity of Pt NCs with the substrate TMB,thereby contributing to outstanding peroxidase mimicking activity in near-neutral media.Hep-reduced Pt NCs possess high specificity in mimicking peroxidase,and has very low oxidase activity.The most efficient Pt nanozyme was reduced by adopting the[K₂Pt Cl₄]/[Hep]of 1:1,showing the K_m values of 165 m M for H₂O₂ and 0.016 m M for TMB.By employing this Pt nanozyme into a typical cascade reaction,a colorimetric test was developed for directly probing Glu at p H 6.The linear response exists in the range of 0.1?2.0 mM,giving the LOD of 33?M.