Resumen de Development of polymeric coatings with combined antifouling/antibacterial properties for titanium dental implants
Titanium dental implants are a commonly used solution for the replacement of lost teeth. Even though the success rate is high, the number of infections related to the placement of the implant is still remarkable and may impair the proper function of the device, leading to health and economic costs. The infections related to medical devices start with a bacterial adhesion and proliferation on the material surface, leading to the formation of a complex biofilm able to protect the bacteria from the host immune response and the treatment with antibiotic. Due to the difficulty of treatment of the implant site one the biofilm is settled, one of the strategies to avoid the infection is to deal with the initial bacterial adhesion. This PhD thesis deals with the development of polymeric antibacterial coatings on titanium for dental implants, focusing on the achievement of fast and cost-effective procedure. With this aim, different coating strategies have been developed, tested and compared.
A pre-treatment of the titanium surface was optimized in the first part of the thesis in order to achieve a clean surface and to enhance the chemical reactivity of the titanium oxide. With this aim, low pressure plasma activation was the selected method. The use of plasma activation allows for the removal of organic contaminants while increasing the surface energy of the treated surfaces.
For the preparation of the polymeric antibacterial coatings, two different antifouling polymers have been used, namely, polyethylene glycol (PEG) and poly-2-hydroxyethylmetacrylate (PHEMA). PEG coatings were prepared by three different techniques, a wet chemical technique (silanization), a plasma enhanced chemical vapor deposition and an electrochemical process (electrodeposition). The three methods rendered an ultra-thin coating able to resist the bacterial adhesion. On the other hand, PHEMA-like coatings were prepared in a novel set-up by treating the liquid monomer by a plasma jet.
Moreover, the different coatings were biofunctionalized in order to achieve multifunctionality and enhance the performance of the coating. For instance, the combination of PEG with a cell adhesion peptide (RGD) reported a better human fibroblast adhesion while maintaining the antifouling properties of the coating. PEG was also used as a platform for the immobilization of antimicrobial peptides (AMP). The bonding of the polymer with the AMP was optimized, achieving a surface able to reduce the bacterial adhesion and to kill the bacteria still able to adhere to the surface. Finally, the combination of two different plasma polymerized coatings with antibiotics (either Doxycycline or Vancomycin) was used as a drug delivery system.
