Buildup mechanism for poly(L-lysine)/hyaluronic acid films onto a solid surface

The formation of a new kind of biocompatible film based on poly(L-lysine) a nd hyaluronic acid (PLL/HA) by alternate deposition of PLL and HA was inves tigated. Optical waveguide lightmode spectroscopy, streaming potential meas urements, atomic force microscopy, and quartz crystal microbalance (QCM) we re used to analyze the different aspects of the buildup process such as the deposited mass after each new polyelectrolyte adsorption, the overall surf ace charge of the film, and its morphology. As for "conventional" polyelect rolyte multilayer systems the driving force of the buildup process is the a lternate overcompensation of the surface charge after each PLL and HA depos ition. The construction of (PLL/HA) films takes place over two buildup regi mes. The first one is characterized by the formation of isolated islands th at grow both by addition of new polyelectrolytes on their top and by mutual coalescence of the islands. The second regime sets in once a continuous fi lm is formed after the eighth layer pair deposition in our working conditio ns and is characterized by an exponential increase of the mass. QCM measure ments at different frequencies evidenced a viscoelastic behavior of the fil ms with a shear viscosity on the order of 0.1 Pa(.)s. This new kind of bioc ompatible film incorporating a natural polymer of the cartilage and a widel y used polypeptide is of potential use for cell-targeted action.