Grafting of hydrophilic monomers onto polyurethane membranes by solution or pre-absorbing methods for acceleration of cell compatibility

Two grafting methods, i.e. solution grafting and pre-adsorbing, are introduced to covalently immobilize hydrophilic polymers on segmented polyurethane (SPU) to modify its hydrophilicity and to improve its cell compatibility. Solution grafting results in higher degree of grafting and rougher surface morphology. Cell culture evaluation demonstrates that the modified membranes thus obtained are disadvantageous to the endothelial cell (ECs) growth probably because the hydrophilic groups on the surface are over-crowded. However, pre-absorbing grafting generates lower degree of grafting, which is detected and confirmed by ATR-FTIR spectra and water contact angle. Scanning electron microscopic (SEM) measurement shows that the latter method produces a plane and smooth morphology, which is similar to the SPU control sample controlled. When grafting with lower monomer concentration, ECs could grow on SPU-g-PHEA [poly(2-hydroxyethyl acrylate)], SPU-g-PAAm (polyacrylamide), SPU-g-PDMA [poly(2-(dimethylamino)ethyl methacrylate)] or quaternized SPU-g-PDMA surface with elongated cell shapes. Hence, the cell compatibility of SPU is improved and a useful method to construct a cell compatible layer on the polymer surface has been developed.