Preparation of Organosoluble Silica−Polypeptide Particles by “Click” Chemistry

Abstract

The synthesis of organo-soluble hybrid particles with a hydrophobic, α-helical polypeptide shell and silica core has been achieved by combining ring-opening polymerization and click chemistry. Alkyne end-terminated poly(γ-stearyl-α- l -glutamate) (alkyne-PSLG) was prepared by the ring-opening polymerization of the N -carboxyanhydride of γ-stearyl-α- l -glutamate using propargylamine as initiator. The molecular weight and structure of this polypeptide were characterized by GPC and MALDI, and the α-helical nature was established by 1 H 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 and XPS. Alkyne-PSLG was coupled to azido-silica by click reaction in tetrahydrofuran or toluene in the presence of pentamethyldiethylenetriamine and copper(I) bromide. Further characterization of the product using XPS, FTIR, and 1 H NMR revealed that the grafted polypeptide retained its α-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.