Construction Of Gold Nanocluster-Based Nanocomposites And Their Applications In Biomedicine

Functional nanomaterials have shown great application prospects in the past two decades.Ultrasmall gold nanoclusters（AuNCs）have been widely used in biomedical fields due to their good biocompatibility and high potential for functional expansion.In this paper,a series of AuNCs with ligand transmutation were prepared using thiol biomolecules（including cysteine and two polypeptides）as ligands.Based on these AuNCs,two nanocomposites were constructed to improve the properties of AuNCs.The main experimental results are summarized as follows:（1）The aggregation induced fluorescence enhancement（AIEE）effect of AuNCs induced by Zn²⁺and other metal ions was studied,which shows a pH-dependent evolution.Transmission electron microscopy（TEM）was used to reveal the evolution of particle state from single AuNCs to spherical aggregates and then to irregular network structure with increasing pH.Using photoluminescent enhancement ratio as an index,the concept of“mid-pH”is proposed to quantize the optimal pH for the formation of spheric AuNCs aggregates.Based on the mid-pH,[G1E3+Zn²⁺]containing RGD targeting sequence was selected to label integrin-positive He La cell,providing a new idea for the application of AuNCs in cell fluorescence imaging.（2）AuNCs@SNP nanocomposites with enhanced nano-enzymatic activity was constructed.The silica nanoparticles（SNP）were prepared by St（?）ber method and modified by amination to make it carry positive charge（SNP-NH₂）.AuNCs were self-assembled on the surface of SNP to form AuNCs@SNP through electrostatic action.AuNCs@SNP It shows enhanced peroxidase-like activities,which was 10.54 and 4.33 times higher than AuNCs and SNP,repectively.The kinetic test shows that the nanocomposites have a catalytic activity close to the HRP,which provides a new direction for improving the peroxidase-like activities of AuNCs and exploiting better nano-enzymes.