| Reactive oxygen species（ROS）were usually produced by metabolic processes in living organisms.Although there are multiple enzymes that regulate ROS in human body,imbalance of ROS will lead to oxidative stress,causing many acute and chronic diseases such as cardiovascular and cerebrovascular diseases,diabetes,chronic kidney disease,intestinal diseases and various cancers.It can also cause neurodegenerative diseases such as Alzheimer’s disease（AD）.The clinical manifestations of AD are mainly severe cognitive impairment and behavior and personality changes.Although the pathogenesis of AD is not fully understood,there is a lot of evidence that abnormal folding of Amyloid-βand accumulation of insoluble amyloid aggregates are the key steps in the pathogenesis of AD.Therefore,it is of great importance to find a kind of nanomaterial with anti-oxidation properties to resist oxidative stress and AD.Although studies have shown that noble metal nanoclusters,such as gold nanoclusters or silver nanoclusters,have certain antioxidant capacity,reports on copper nanoclusters（Cu NCs）are relative few.Thanks to the tremendous advances in nano-synthetic chemistry,today we can obtain high-quality copper nanoclusters with custom sizes and good stability.Due to the unique physical and chemical properties,such as large specific surface area,high luminous efficiency,excellent chemical stability,and good biocompatibility,copper nanoclusters act as a new type of nanomaterial for bio-catalysis,optical sensing,and biomedicine.In this paper,biological peptide glutathione（GSH）was used as the ligand to synthesize copper nanoclusters（GSH-Cu NCs）under mild conditions.According to the characterization results,ultra-small GSH-Cu NCs was successfully synthesized with uniform size of 1.5±1 nm accompanied by strong fluorescence emission.The experimental results also show that GSH-Cu NCs can stably exist in a large p H range.Based on the good biocompatibility,we have applied it to the test of multi-enzyme activities.The catalase（CAT）activity of Cu NCs was measured by the dissolved oxygen in solution and modified Hafeman’s method was used to test glutathione peroxidase（GPx）activity of Cu NCs.According to the experimental results,we found that GSH-Cu NCs have good GPx activity and certain CAT activity.It is worth mentioning that catalytic activity of GSH-Cu NCs has a lot to do with its concentration and proper increasing in the reaction temperature can improve CAT activity of GSH-Cu NCs.In addition,the SOD vitality of GSH-Cu NCs was calculated to be 25.6 U·mg-1using superoxide dismutase（SOD）kit.These results indicate that GSH-Cu NCs with multi-enzyme activities can effectively protect cells from oxidative damage and therefore have therapeutic potential for preventing ROS-mediated neurological diseases.Finally,we investigated the effects of different concentrations of GSH-Cu NCs on Amyloid-βfibrosis through atomic force microscope（AFM）and thioflavin-T（Th T）fluorescent labeling.We found that the inhibitory effect of GSH-Cu NCs on Amyloid-βincreased as its concentration increased.The inhibition of Amyloid-βfibrosis and aggregation at different time and the results of CD kinetics show that GSH-Cu NCs cannot decompose the completed fibrotic protein,but inhibit the conformational transition of Amyloid-βfromα-helix toβ-sheet in the growth stage which in turn inhibit the fibrotic process. |
