Surface initiated-atom transfer radical polymerization of a sugar methacrylate on gold nanoparticles

For development of surface-functionalized gold nanoparticles (GNPs) as cellular probes, we report herein the synthesis of glycoconjugates of GNPs with cyclic sugar methacrylate, 2-lactobionamidoethyl methacrylate (LAMA). The strategy involves the attachment of an initiator on the nanoparticle surface followed by surface initiated-atom transfer radical polymerization (SI-ATRP) of LAMA. SI-ATRP of LAMA was achieved by reacting a mixture of copper (1) bromide (CuBr), 2,2'-bipyridine (bpy) and initiator-bound GNPs in methanol at 20 degrees C for 12 h. The resultant GNP glycoconjugates were characterized using Fourier-transform infrared (FT-IR) spectroscopy, X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM). The FT-IR spectra of GNP glycoconjugates show IR peaks characteristic of LAMA demonstrating the formation of a LAMA layer on the GNPs' surface. The XPS spectrum of glycoconjugates shows signals due to the presence of carbon (C1s, 288 eV) and oxygen (O1s, 536 eV) along with gold (Au 4f, 100 eV; Au 4p, 743 eV). The increase in diameter of GNPs from 13 to 25 nm measured by SEM further confirms the presence of a LAMA layer on the surface of the GNPs. Considering the biological importance of glycoconjugates, such as cell recognition, cell adhesion and cell growth regulation, the method described herein would be beneficial in many areas such as pathogen detection and biosensors. Copyright (C) 2008 John Wiley & Sons, Ltd.