Construction Of The Antibacterial Coating Via Layer-by-Layer Electrostatic Self-Assembly

Infection frequently happens in the implanted biomaterials. The bacteria initially enter into the body and adhere on the biomaterial surface, subsequently they will propagate and grow into the biofilm which is a protection barrier for the bacteria and very difficult to treat. The layer-by-layer self assembly technology was used to inhibit the formation of biofilm and reduce the infection rate.The chitosan as an antibacterial agent and the heparin as an anti-adhesion agent were successfully deposited onto the aminolyzed PET by the layer-by-layer self assembly technology. FTIR and XPS was used to demonstrate the aminolysis of the PET surface. The contact angle measurement and UV-visible spectroscopy indicated the assembly was successful. The initial adhesion test showed that the bacteria adhesion increased with the increase of assembly pH. The in vitro antibacterial test showed that the multilayers assembled at pH 3.8 had the strongest antibacterial property and that the multilayers assembled at pH 6.0 had the weakest antibacterial property.On the basis of the above results, the nanosilver was incorporated into the biocompatible chitosan/heparin multilayers through the effect of chitosan deprotonization and heparin ionization. The concentration and size of nanosilver were controlled through the adjustment of assembly pH and loading pH. UV-visible spectroscopy, TEM, and AAS were used to follow the process. The antibacterial assay showed the much stronger antibacterial property than the chitosan/heparin multilayers. And the long-term antibacterial property showed that the nanosilver incorporated multilayers still had good antibacterial performance after one month.TiO₂ is a very efficient photocatalyst with a strong antibacterial action under low intensity UV light. In this research, the small and low size distribution anatase TiO₂ nanoparticles were successfully synthesized using the simple sol-gel method. The layer-by-layer self assembly technology was adopted again to assemble the TiO₂blended chitosan and heparin. QCM and the contact angle demonstrated the alternate buildup progress of the assembly. The antibacterial test showed that the multilayers had very strong antibacterial performance under the low intensity UV light. In order to make the multilayer bactericidal in the dark, the nanosilver was incorporated again into the multilayer film and the antibacterial test demonstrate the strong antibacterial property in the dark. The long-term antibacterial test showed the nanosilver incorporated TiO2,chitosan/heparin multilayers have stable antibacterial property.