Preparation of Organosoluble Silica-Polypeptide Particles by "Click" Chemistry

The synthesis of organo-soluble hybrid particles With a hydrophobic, alpha-helical polypeptide shell and silica core has been achieved by combining ring-opening polymerization and click chemistry. Alkyne end-terminated poly(gamma-stearyl-alpha-L-glutamate) (alkyne-PSLG) was prepared by the ring-opening polymerization of the N-carboxyanhydride of gamma-stearyl-alpha-L-glutamate using propargylamine Lis initiator. The molecular weight and structure of this polypeptide were characterized by GPC and MALDI, and the alpha-helical nature was established by H-1 NMR and FTIR. Azide-functionalized silica particles (azido-silica) were prepared by the functionalization of silica particles with 3-bromopropyltrichlorosilane followed by nucleophilic substitution with sodium azide. The azide functionalization was confirmed by FTIR mid XPS. Alkyne-PSLG was coupled to azido-silica by click reaction in tetrahydrofuran or toluene in the presence of pentamethyldiethylene-triamine and copper(l) bromide. Further characterization of the product using XPS, FTIR, and H-1 NMR revealed that the grafted polypeptide retained its alpha-helical nature and formed colloidal particles that readily dispersed in organic solvents. These hydrophobic, polypeptide-functionalized particles can serve as model systems in studies of colloid dynamics and/or crystallization. They may also find use in investigations designed to model enzyme activation or the properties of hydrophobic proteins in cell membranes.