ИСТИНА

Colloidal gold has many applications in biosensing, catalysis and therapy. It is advantageous to encapsulate colloidal gold into biocompatible carriers that can provide long blood circulation of the particles and control their clearance. The present work was focused on the fabrication of gold nanoparticles encapsulated in the micelles of amphiphilic block copolymers of ethylene oxide (EO) and amino acids. Poly(amino acid) block can bind to gold metal trough hydrophobic and coordination forces, while hydrophilic polyethylene oxide block stabilize metal particles towards aggregation in water solution. In this study, we obtained colloidal gold in reaction between HAuCl4 and block copolymers of EO and tyrosine (Tyr). We found that polytyrosine block enters this reaction as a reducing agent. The copolymers containing 30-70 mass. % of polytyrosine were synthesized via ring-opening polymerization of L-Tyrosine N-carboxyanhydride using amino-PEG as a macroinitiator. Degree of polymerization of polytyrosine varied between 8 and 100, while degree of polymerizarion of PEG was 52 and 115. Thus obtained block copolymers formed micelles with average hydrodynamic radii varying in the 20-70 nm range. Addition of HAuCl4 led to formation of golden colloidal particles whose properties depended on the composition of the copolymer. Investigation of obtained samples by ultraviolet–visible spectroscopy and transmission electron microscopy revealed that reaction with the copolymers containing short polytyrosine block resulted in large particles with diameter 20-300 nm, which exhibited intensive plasmonic absorbance band at about 530-540 nm. On the other hand, ultrasmall gold particles with diameter less than 2 nm formed in the presence of the copolymers containing long polytyrosine block. This kind of colloidal gold is called gold nanoclusters and attracts great attention because of its high surface energy, molecule-like fluorescence and atomically precise structure. Thus, we first have demonstrate that colloidal gold can be obtained in reaction between HAuCl4 and block copolymers of EO and tyrosine. In addition, we have disclosed that Tyr/EO ratio in the copolymers determines size and properties of the obtained gold nanoparticles.