Surface modification of titanium with chitosan-heparin multilayers via electrostatic self-assembly technique

To improve the surface biocompatibility of titanium films, a electrostatic self-assembly technique (ESA), based on the polyelectrolyte-mediated electrostatic adsorption of chitosan (Chi) and heparin (Hep), was used leading to the formation of multilayers on the titanium thin film surfaces. The film growth was initialized by depositing one layer of positively charged poly-L-lysine (PLL) on the NaOH-treated titanium substrate (negatively charged surface). Then the film was formed by the alternate deposition of negatively charged heparin and positively charged chitosan via electrostatic interactions of polyelectrolytes, and terminated by an outermost layer of chitosan. The ESA film was monitored by several techniques. The chemical composition and surface topography were investigated by using diffuse reflectance Fourier transform infrared spectroscopy (DR-FTIR), scanning electron microscope (SEM) and atomic force microscope (AFM), respectively. The results indicated that a full surface coverage for the outmost layer was achieved after deposition of sixteen layers. Cell morphology, cell proliferation as well as differentiation function (alkaline phosphatase) of osteoblasts on ESA-modified titanium film (PLL/(Hep/Chi)16) and control sample were investigated, respectively. Osteoblasts cultured on ESA-modified titanium film showed better morphology than that of control. Cell proliferation and alkaline phosphatase measurements indicated that osteoblasts on ESA-modified titanium films were greater (p<0.01) than those for the control, respectively. These results suggested that surface modification of titanium was successfully achieved via deposition of PLL/(Hep/Chi)16 layers, which was useful to enhance the biocompatibility of the titanium film. The approach presented here may be exploited for fabrication of titanium-based implant surfaces.