Nanomechanical Properties of Oligo(ethylene glycol methacrylate) Polymer Brush-Based Biointerfaces

Protein resistant polymer brushes of poly(diethylene glycol methylether methacrylate) (DEGMA) are synthesized by surface-initiated polymerization (SIP) on gold and are thoroughly characterized with particular attention to the nanomechanical properties. Compared to the well known brushes of poly(oligoethylene glycol methylether methacrylate) (POEGMA) on gold, PDEGMA brushes grow faster and yield higher final brush heights. In confocal fluorescence microscopy experiments it is shown that both types of brushes possess similar low non-specific adsorption levels of labeled bovine serum albumin (BSA) from buffer. While the surface stiffness evaluated by depth sensing indentation in the dry state suggests that side chain crystallization imparts high stiffness to the POEGMA brush, PDEGMA brushes behave similar to poly(methyl methacrylate) (PMMA) brushes of comparable thickness. In the wet state PDEGMA brushes are shown to possess an elastic modulus of 800 kPa, as estimated by AFM nanoindentation, which is smaller than that of POEGMA (3 000 kPa). Expanding these brushes to end-functional polymers with recently developed block copolymer brush approaches, tailored soft biointerfaces can be generated for cell - surface interaction and cell culture studies.