Graft polymerization of acrylic acid (AA) onto poly(L-lactide) (PLLA) film by UV irradiation was carried out to develop surfaces for N-methylene phosphonic chitosan (NMPC) immobilization. The properties of modified films were discussed by colorimetric method, attenuated total reflection-Fourier transform infrared spectroscopy (ATR-FTIR), contact angles, atomic force microscopy (AFM) and osteoblast incubation. The results showed that AA solution concentration and irradiation time had effect on the graft carboxyl densities. Comparing the ATR-FTIR images, two new peaks at 1561 cm (1) and 1632 cm (1) proved that NMPC was immobilized on the film surface successfully. The water contact-angles were decreased from 90 +/- 5 degrees to 37 +/- 5 degrees after modification. The AFM images indicated that the surface of the combined film was rougher than that of untreated film. The grafted film provided an excellent substrate for the growth of osteoblast. (C) 2008 Published by Elsevier B.V.