Bioactive Coatings and Antibacterial Approaches for Titanium Medical Implants

Sammanfattning: The aim of this thesis was to characterize and manufacture coatings and surfaces with antibacterial properties and retained or enhanced bioactivity and biocompatibility. The aim was also to study the optimal composition and parameters of mixtures for debridement of bacterial biofilms on titanium surfaces. The mixtures contained TiO2 particles and H2O2 and were irradiated by light to activate reactive oxygen species (ROS) formation.In the first part of the thesis, characterization of a thin, multifunctional hydroxyapatite (HA) coating was performed. The coating was applied to anodized cancellous bone screws with the purpose of stimulating local bone formation without bonding too firmly and providing local antibacterial effect. Specifications of the coating included a thickness of around 1 µm, high crystallinity, Ca/P ratio close to the theoretical value of 1.67 and comprise the functional groups of HA. Additionally, the adhesion of the coating to the substrate should be stronger than the cohesion of the coating. Characterization results showed that the coating met the specification for all criteria.        In the second part of the thesis, titanium discs were soaked in H2O2 and subsequently in NaOH and Ca(OH)2 to acquire an antibacterial surface that at the same time is bioactive and biocompatible. The surface demonstrated bioactive properties, assessed by soaking in phosphate buffered saline for seven days in 37°C and examined in scanning electron microscopy and X-ray diffraction.The third part of the thesis consisted of studying the ROS generation of TiO2/H2O2 mixtures irradiated with UV-Vis light, and to study the antibacterial effect of these mixtures on S. epidermidis Xen 43 and Pseudomonas aeruginosa biofilms on titanium surfaces. The generation of ROS from different TiO2 crystalline forms and different H2O2 concentrations under light UV-Vis irradiation was determined by rhodamine B degradation. It showed that rutile and 1-3.5 mM H2O2 resulted in the highest degradation of all combinations with almost 100% degradation under 365 nm light and 77% degradation under 405 nm light after 10 min.The debridement of the S. epidermidis and P. aeruginosa biofilm discs showed that 0.95 M (3%) H2O2 was the most effective parameter for disinfection of the discs. The addition of TiO2 particles showed a significant extra effect in one of the three studies.