In this study, the effect of cell alignment on proliferation and phenotype expression of rat bone marrow derived osteoblasts on micropatterned (MP) PHBV and P(L/D,L)LA films with 27 mu m wide parallel microgrooves was investigated. Immobilization of fibrinogen (Fb) on film surface by adsorption increased hydrophilicity, while covalent immobilization decreased it. Amount of Fb immobilized was significantly higher upon covalent bonding (153.1 +/- 42.4 mu g Fb/cm(2)) than when adsorbed (10.0 +/- 3.3 mu g Fb/cm(2)). It was observed that the presence of MP did not influence cell proliferation in the long run. Osteoblasts on MP films with adsorbed (MP Fb(a)) and covalently immobilized Fb (MP Fb(1)) aligned parallel to the groove axis with mean deviation angles of 10.59 +/- 23.47 and 29.02 +/- 33.03 degrees, respectively, while on tissue culture polystyrene (TCP), on unpatterned films (UNP) and on UNP with adsorbed Fb (UNP Fb(a)) alignment with an arbitrary axis was much higher: 46.66 +/- 24.98, 48.72 +/- 31.19, 47.74 +/- 27.29 degrees, respectively. Fb-free MP films were not effective in cell alignment, and clumps were formed. Cell alignment achieved on MP Fb(a) films did not influence cell proliferation, but increased differentiation, as shown by ALP activity per cell and the evenness and the amount of calcium phosphate deposition. It was concluded that orientation of cells was influential on their differentiation and also, MP cell carriers with chemical cues on their surfaces are important in improving tissue repair. (c) 2005 Elsevier Ltd. All rights reserved.