Thin degradable coatings for optimization of osteointegration associated with simultaneous infection prophylaxis (OsteoInt)

• Applicants: Dr. Sofia Dembski; Professor Dr. Andreas Killinger; Privatdozent Dr.-Ing. Michael Seidenstücker
• Subject Area: Biomaterials ; Orthopaedics, Traumatology, Reconstructive Surgery
• Term: since 2013
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 240897167

The colonization of biomaterials with bacteria represents the main cause of implant-associated infections. Both an antibiotic prophylaxis and a faster osteointegration can be obtained by incorporation of bactericidal active metals in degradable CaP coatings. By using the high-velocity suspension flame spraying process (HVSFS) it is possible to produce thin coatings of resorbable bioactive ceramics based on degradable calcium phosphate and bioactive glasses doped with bacteriostatically/bacticidally active metals silver, copper and bismuth. The process parameters used so far lead to very densecoatings, which considerably reduce degradability. This is associated with a very low release rate of bactericidal active metal ions. The aim of the application is therefore to develop coatings with controllable porosity and surface roughness in order to ensure degradation of the coatings, which runs simultaneously with the formation of new bone.At the same time, a continuous release of the metal ions during degradation of the ceramics has to be achieved, which is sufficient to prevent biofilm formation on the implant. Therefore, three different approaches are to be pursued: 1. The process parameters were previously optimized to application efficiency and coating adhesion. Inthis project, the focus of process parameter optimization will be on a defined porosity. 2. A new two-way injector concept to be developed allows the injection of suspensions at different positions in the combustion jet (axial combustion chamber rear, radial free jet). The aim is to generate particle flows with different kinetics. The porosity as a function of these partial streams is to be adjusted by varying the injection location and flow rate ratios. 3. Another promising approach is the implementation of nanoparticles (NP) in the coatings. They can be designed as hollow particles or complex raspberry-like particlesystems. The NP should exhibit a similar resorption behavior as the ceramic materials used for the coatings. This third approach focuses on the synthesis and characterization of biodegradable silica and calcium phosphate NP. Special attention must be paid to theadjustment of a degradation similar to the coatings. These nanoparticles can also have a positive effect on preventing the formation of cracks in the coating. The hollow particles additionally open up a new possibility of introducing antibiotics or antibiotic activesubstances into the coatings. It is planned to review this possibility as a proof of concept towards the end of the project. The new coating systems will be analysed with regard to the degradability, biocompatibility and release kinetics of the metal ions. It is alsoplanned to analyse the antibiotic effectiveness of the coatings. The quantitative, time-dependent in vivo degradation of the coatings and the quality of osteointegration are assessed with the aid of an established animal model in the rabbit.

• DFG Programme: Research Grants