P(AAm-co-EG) Interpenetrating Polymer Networks Grafted to Oxide Surfaces: Surface Characterization, Protein Adsorption, and Cell Detachment Studies

Abstract

We investigated the composition, properties, and utility of a novel copolymer of P(AAm-co-EG) designed to be an adaptable, durable, and biocompatible surface treatment of metallic, polymeric, and ceramic materials. Solution deposition and photoinitiation reactions were employed to graft a silane layer and then two sequential polymer layers (a discontinuous two stage polymerization) onto oxide surfaces. Different solvents, polymer concentrations, and cross-linker concentrations in the top polymer layer were compared. Contact angle measurements, spectroscopic ellipsometry, and X-ray photoelectron spectroscopy were used to characterize layer wettability, thickness, and chemistry, respectively. A sandwich type network formed between acrylamide and poly(ethylene glycol) when acetone was used as the solvent for both layers. In contrast, an interpenetrating polymer network between acrylamide and poly(ethylene glycol) formed when acetone and methanol were used as the solvents for polymerization of the acrylamide and poly(ethylene glycol) layers, respectively. Interpenetrating polymer network configured samples were tested for protein adsorption and strength of cell attachment. Protein adsorption experiments in 15% fetal bovine serum indicated that significant amounts of protein do not adsorb to the surface of the thin polymer films (∼20 nm). Cell detachment experiments indicated that cells contacting copolymer-modified surfaces were removed by lower shear stresses than cells contacting clean and amine-terminated, (N-(2-aminoethyl)-3-aminopropyl)trimethoxysilane modified surfaces.