Temperature-responsive polymer brush constructed on a colloidal gold monolayer.

Polymers of 2-(2-methoxyethoxy)ethyl methacrylate (MDM) were prepared by atom transfer radical polymerization using 2-(2'-bromoisobutyroyloxy)ethyl disulfide as initiator. An aqueous solution of the disulfide-carrying polymer (DT-PMDM) turned to be opaque above certain temperature (22 degrees C for DT-PMDM (M(n)=1.69x10(4))), which was corresponding to the lower critical solution temperature (LCST) of the polymer. The disulfide-carrying polymer could be accumulated on the surface of gold colloid as a polymer brush as confirmed by the increase in absorbance at 550 nm ascribable to the localized surface plasmon resonance (LSPR). Furthermore, the polymer brush could also be constructed on a monolayer of colloidal gold that had been deposited on a glass plate beforehand. The PMDM brush on both the free and surface-confined gold colloids showed definite temperature responsiveness in the absorbance at 550 nm. Moreover, non-specific adsorption of various proteins to the surface of polymer brush on the glass plate was examined by the absorption increase at 550 nm. The PMDM brush, which had been prepared with the DT-PMDM pretreated with NaBH(4), did not adsorb lysozyme significantly below the LCST of the polymer chain, whereas substantially adsorbed the protein above the LCST. These results suggest usability of the polymer brushes with pendent omega-methoxy oligo(ethylene glycol) groups to coat various materials for biomedical applications.