Polyurethane membranes with tunable surface properties for biomedical applications

The use of surfaces with tunable properties triggered by external stimuli is effective in controlling the interactions between biomaterials and biological entities, such as proteins and cells. The goal of this work is to prove that the presence of poly-n-isopropylacrylamide (P-N-IPAAm) chains grafted onto polyurethane (PU) membranes and used for medical wound dressings can allow the behavior of the surfaces to be shifted from hydrophobic to hydrophilic by reducing the temperature to values lower than the low critical solution temperature (LCST) of the polymer, which is close to 32°C. The manipulation of this behavior can then be used to control cell and protein adhesion on the surface. Grafting of P-N-IPAAm was accomplished by treating the surface of polyurethane membranes with ultraviolet (UV) radiation, followed by polymerizing the isopropylacrylamide from the modified surfaces. The wettability of the surfaces was studied using contact angle measurements as a function of temperature. Infrared spectroscopy was also used to characterize these modified surfaces. The ability of the grafted surfaces to allow adsorption of proteins was evaluated as a function of temperature. The results showed that the amount of proteins adsorbed on the polyurethane membranes could be radically changed by altering the temperature above or below 32°C. In vivo biocompatibility tests were performed on P-N-IPPAm samples, and no indication of toxicity was noted after 7 days of implantation. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011