Generating Surface-Anchored Zwitterionic Networks and Studying Their Resistance to Bovine Serum Albumin Adsorption

We report a simple method to generate surface-anchored zwitterionic network coatings that exhibit low nonspecific protein adsorption. We first synthesize amphiphilic random copolymers comprising 2-(dimethylamino)ethyl methacrylate (DMAEMA) and propargyl methacrylate (PGMA) units in two different nominal molar ratios (50:50 and 75:25) by free radical copolymerization. The DMAEMA moieties in the copolymers are then betainized with 1,3-propane sultone to obtain zwitterionic macromolecules. We create substrate-anchored network coatings by casting thin copolymer films (∼100 nm) containing 2 wt % of photoactive benzophenone onto a polystyrene substrate and cross-link them by UV-light irradiation at 365 nm (UV dose = 9–10 J/cm2). We investigate the cross-linking reaction with infrared spectroscopy, monitor the change in film thickness, and study the swelling behavior of the coatings as a function of ionic strength and electrolyte using spectroscopic ellipsometry. We demonstrate the performance of such surface-attached zwitterionic networks by studying their resistance to nonspecific adsorption of bovine serum albumin (BSA).