Research On Colorimetric Analytical Methods Based On Metal Nanozymes

Nanozymes are nanomaterials with enzyme-like activities,and it is a research hotspot in the field of artificial enzymes.Compared with natural enzymes,nanozymes have the advantages of low cost,simple preparation,good stability and easy surface modification.Therefore,nanozymes are widely used in clinical diagnosis,nanomedicine and environmental pollutant detection.However,the currently developed nanozymes still have the problems of low catalytic activity and poor specificity.Improving the catalytic activity and the affinity of substrates of nanozymes is the focus of current research.In this thesis,we have studied the effects of different ions and molecules on the catalytic activity and the affinity of substrates of metal nanozymes.It was found that certain analytes significantly enhanced or inhibited the catalytic activity of nanozymes.For example,lead ion can enhance the peroxidase-like activity of gold nanoclusters;sulfur ion can inhibit the peroxidase-like activity of copper nanoclusters;heparin can increase the peroxidase-like activity of gold nanoclusters;heparinase can inhibit the peroxidase-like activity of gold nanoclusters.Three new colorimetric methods for detecting target analytes are established based on the enhancement or inhibition of the analytes on the catalytic activity of nanozymes.The main results are as follows:1.Lead ions can increase the peroxidase-like catalytic activity of gold nanoclusters.In the presence of lead ions,the catalytic activity of the aggregated gold nanoclusters on the peroxidase substrate 3,3’,5,5’-tetramethylbenzidine increased by nearly 10 times.Based on this finding,a simple and reliable new method for colorimetric detection of lead ions was developed.2.Sulfur ions can inhibit peroxidase-like activity of copper nanoclusters.In the presence of sulfides,the catalytic activity of copper nanoclusters was significantly reduced.Based on this finding,a colorimetric assay was developed for the rapid determination of sulfides.The detection limit is 0.5 μM.This method has good selectivity and it is successfully applied to the quantitative analysis of sulfur ions in environmental water samples.3.Heparin can greatly enhance the peroxidase-like activity of gold nanoclusters at neutral p H.In the presence of heparin,the catalytic activity of the gold nanoclusters on the peroxidase substrate TMB increased by 25 times.After the addition of heparinase,the heparin was cut into small fragments,and the peroxidase-like activity of gold nanoclusters was decreased.Based on this phenomenon,a new analytical method for colorimetric determination of heparin and heparinase was developed.This method has also been applied to the detection of heparin and heparinase in diluted serum samples.