Objectives: Chemical modification of biomaterial surface with polyelectrolyte self-assembled films is a promising method for their bio-functionalisation to achieve improved biointegration. Methods: Poly-L-lysine (PLL) and poly-L-glutamic acid (PGA) polyelectrolyte (PE) films were deposited onto titanium and silica substrates by sequential adsorption methods in two ways: buildup either in situ, in the liquid cell of the atomic force microscope (AFM) or by an automatic immersion technique (dry samples). In this way possible differences of film surface characteristic between in situ and immersion buildup method were investigated which is an important aspect of industrial applicability. As surface characteristics, mean roughness (R_a), grain height (G_h) and grain diameter (D) were determined. Results: In case of in situ buildup both on silica and titanium substrates up to 10 bilayers the film shows granular pattern. For samples on titanium the R_a, G_h values are bigger than on silica, probably due to the originally rougher titanium surface. The grain diameter is independent of the method used and is about 1.4 times smaller on titanium than on silica for both in situ and dry samples that can be related to the different hydrophobicity of the substrates. On titanium discs the layers were stable in time for up to at least two months, during which R_a, G_h, D were not changing significantly. In contrast, roughness was changing with time when films were built onto silica. Conclusion: Comparison of the two buildup procedures shows an independence of the method used and a very good stability in time. Films deposited onto titanium are more stable in time, than on silica. The stability of PLL/PGA multilayer coatings built on titanium by immersion is of prime importance for their biomedical use. Aknowledgment: This work was supported by the SIMI-NAS Project of the 5^th FWP of the European Commission (GRD3-2001-61801).

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