In the present study, a surface functionalization of a synthetic polyurethane was carried out by using biofunctional moieties to obtain a material with the appropriate mechanical properties and processing conditions and, at the same time, the advantages of a bioactive material. The polyurethane (PU) was synthesised from poly(epsilon-caprolactone) diol, 1,6-diisocyanatohexane and 1,4-cyclohexane dimethanol as chain extender. PU films were grafted with acrylic acid using argon plasma. The carboxyl groups formed were used to covalently bind model biomimetic/bioactive macromolecules (gelatine and poly (L-lysine). All characterizations (attenuated total reflection Fourier transform infrared spectroscopy, ATR-FTIR; X-ray photoelectron spectroscopy, XPS; atomic force microscopy, AFM; scanning electron microscopy, SEM) confirmed the surface changes at each stage of treatment, both in morphology and in chemical composition. Besides, achieved treatment allowed to obtain a very thin layer of both PAA and macromolecules. Moreover, preliminary in vitro tests were performed using NIH-3T3 fibroblasts as cell model. Both materials showed to support cell adhesion and growth, with poly (L-lysine) performing better in activating cellular processes, as it can be seen by cell shape, which appears elongated on poly (L-lysine) coating, whereas on gelatine, cells are more spherical and not uniformly distributed on the polymer surface. (c) 2007 Elsevier Ltd. All rights reserved.