Dewetting of Polymer Films Controlled by Protein Adsorption

The stability of the film poly(n-butyl methacrylate) (PnBMA) with different tacticities, prepared on silicon oxide and exposed to aqueous phosphate-buffered saline with different concentrations of bovine serum albumin (C_BSA between 0 and 4.5 mg/mL), was examined at temperatures close to the physiological limit (between 4 and 37 °C) with optical microscopy, contact angle measurements, atomic force microscopy, and time-of-flight secondary ion mass spectrometry. For PBS solutions with C_BSA = 0, the stability of atactic PnBMA and dewetting of isotactic PnBMA was observed, caused by the interplay between the stabilizing long-range dispersion forces and the destabilizing short-range polar interactions. Analogous considerations of excess free energy cannot explain the retardation of dewetting observed for isotactic PnBMA in PBS solutions with higher C_BSA. Instead, formation of a BSA overlayer, adsorbed preferentially but not exclusively to uncovered SiO regions, is evidenced and postulated to hinder polymer dewetting. Polymer dewetting and protein patterning are obtained in one step, suggesting a simple approach to fabricate biomaterials with micropatterned proteins.