Functional PEG-Hydrogels Convey Gold Nanoparticles from Silicon and Aid Cell Adhesion onto the Nanocomposites

A novel poly­(ethylene glycol) (PEG)-based hydrogel has been synthesized and further functionalized by amine and thiol-ene Michael-type addition reactionsfirst with ammonia and then with dithiothreitol, respectivelyto yield hydrogels with thiol functions (8PEG-VS-SH), hence with high affinity for gold. Consequently, gold nanoparticles (Au NPs) can be firmly bound and immobilized on their surface. It is demonstrated that Au NPs with different sizes (20 and 42 nm, respectively) that decorate silicon surfaces in different densities can easily be transferred from silicon wafers to the surface of hydrogels, with a transfer efficiency of more than 98%. The novel Au NPs-PEG nanocomposite gels (Au NPs@Gel) have been investigated in a cell culture with murine fibroblasts L-929. Optical microscopy studies revealed remarkable cell adhesion on these nanocomposites. Apparently, the nonfunctionalized Au NPs on the intrinsically anti-adhesive PEG background do serve as anchoring points for cell adhesion. We propose that protein adsorption is enabled on these nanocomposite surfaces and this in turn results in the cell adhesion.