Polypeptide-templated Au Nanoclusters Preparing And Using For Imaging Of Cell Nuclei And Antibacterial Activity

Noble metal nanoclusters are ultrasmall nanoparticles that smaller than 2nm,and composed of several to hundred metal atoms.Due to its special size effect,have special physical and chemical properties like specific molecular structure and fluorescence characteristics.Noble metal nanoclusters that using proteins and peptides as templates have attracted attention in biomedical applications and cell imaging due to their excellent biocompatibility,size-dependent fluorescent properties,and relatively simple synthetic methods.The noble metal nanoclusters synthesized by functional peptides could maintain the biological activity of the peptides,physical and chemical properties of nanoclusters.Base on the above,this subject has synthesized a series of noble metal nanoclusters by using functional peptide as templates,applied in Imaging probe for nuclei multi-mode imaging.Based on previous work of group in biological effects of cancer and inflammation,the antibacterial effect of noble nanoclusters was studied in experiment.The main content is as follows:（1）Synthesis of functional Au clusters and nuclei multimodal imagingIn this experiment,two different types of gold clusters were synthesized by using SV polypeptide（NH₂-CCYGGPKKKRKVV-COOH）.One with red fluorescence emission(λ_ex=560 nm,λ_em=657 nm),and the particle size is 1.7±0.27 nm;One has a blue fluorescence emission(λ_ex=320 nm,λ_em=405 nm),and the particle size is 1.2±0.37 nm.The optimal conditions of synthesis were determined by adjusting the conditions,such as light,pH,ratio of peptide to Au,and temperature.Subsequently,the cytotoxicity,catalytic activity,imaging of SV-Au NCs were studied.Results show that the Au NCs possessed similar biological activities as the SV peptide,the Au NCs can target the cell nucleus,with their strong fluorescence allowing cell imaging.Moreover,the Au clusters have peroxidase-like activity,can catalyze DAB stained in cells nuclei,distinguished by microscopes,without fluorescence excitation.The Au NCs exhibited excellent multi-modal cell imaging abilities,can labeling and imaging of cell nuclei under fluorescence imaging and optical imaging.（2）Synthesis of functional Au clusters and research of antibacterialIn this study,a non-specific targeting peptide CCY was used as the template to synthesized Au clusters with blue fluorescence emission,λ_ex=320 nm,λ_em=410 nm.CCY-Au NCs have good stability and biocompatibility,can be stably stored in water,PBS solution,DMEM medium.And when the concentration of Au was increased to400μM,there was no obvious cytotoxicity to HeLa cells.Subsequently,the bacteriostatic activity in vitro of CCY-Au NCs was studied.The results show that CCY-Au has significant antibacterial effect on S.aureus in vitro,but has no inhibition on E.coli.At the same time,GSH-Au NCs were experimented to compared the antibacterial activity with CCY-Au.ICP-MS was used to quantified the uptake of gold clusters by single bacterial cells.The experimental results showed that S.aureus had a higher uptake of CCY-Au NCs than E.coli,and the uptake of CCY-Au NCs was much higher than GSH-Au NCs.Different uptakes of gold clusters may influence the antibacterial activity of gold clusters on different bacteria.