Controlled loop and graft formations of water-soluble polymers on SAMs for the design of biomaterials surfaces

Abstract

We prepared four types of water-soluble polymers with anchoring group(s) at one or both terminals: poly(ethylene glycol) (PEG) with one or two anchoring groups and polyrotaxane with one or two anchoring groups. Each polymer was immobilized to successfully form a loop or graft structure on a gold substrate covered with a self-assembled monolayer (SAM) of a tri(ethylene glycol)-dodecanethiol conjugate. Controlled immobilization of the polymers onto a gold substrate was examined by an original two-step protocol and was confirmed by quartz crystal microbalance (QCM) measurement. We investigated the effects of the immobilization modes (loop and graft) of the polymers on the surface properties of biomaterials. Surface softness or rigidity of the hydrated polymers on a SAM was analyzed by QCM with dissipation monitoring measurements, by which we found smaller ratios of energy dissipation to frequency (ΔD/Δf) for a loop structure than for a graft structure in an aqueous environment. With regard to surface wettability, substrates with PEG or polyrotaxane were similar in terms of static and dynamic contact angles and were also not influenced by the immobilization modes. We demonstrate that less fibrinogen was adsorbed on the polyrotaxane loop, making it a good platform for the design of biomaterials surfaces. © 2012 The Society of Polymer Science, Japan (SPSJ) All rights reserved.