Biomineralisation von Knochengewebe unter dem Einfluss von Metallionen

Bei der Implantation eines metallischen Hüftprothesenschafts in den Oberschenkelknochen kommt es zum Austritt von Metallionen in das umliegende Gewebe. Der Vorgang der mit der Osteointegration einhergehenden Knochenneubildung erfolgt also in einem metallionenhaltigen Milieu. In der vorliegenden Arbeit wurde der Einfluss der Metalle Titan, Vanadium, Kobalt, Chrom und Aluminium auf die Mineralisation des wichtigen Knochenminerals Hydroxylapatit untersucht, die in einem vereinfachten chemischen Modellsystem simuliert wurde. Zusätzliche Versuche mit einem komplexeren, den physiologischen Bedingungen angenäherten Modellsystem dienten der Verifizierung der erhaltenen Resultate. Die mit verschiedenen Metallzusätzen hergestellten Apatite wurden mit Hilfe der Röntgendiffraktometrie hinsichtlich ihrer kristallographischen Eigenschaften und ihrer Phasenzusammensetzung untersucht. Dabei konnte die durch Metallionen induzierte Bildung zusätzlicher Kalziumphosphate und die Inkorporation von Metallionen in die apatitische Phase belegt werden

Multifunctional calcium phosphate based coatings on titanium implants with integrated trace elements

For decades, the main focus of titanium implants developed to restore bone functionality was on improved osseointegration. Additional antimicrobial properties have now become desirable, due to the risk that rising antibiotic resistance poses for implant-associated infections. To this end, the trace elements of copper and zinc were integrated into calcium phosphate based coatings by electrochemically assisted deposition. In addition to their antimicrobial activity, zinc is reported to attract bone progenitor cells through chemotaxis and thus increase osteogenic differentiation, and copper to stimulate angiogenesis. Quantities of up to 68.9 ± 0.1 μg cm$^{-2}$ of copper and 56.6 ± 0.4 μg cm$^{-2}$ of zinc were deposited; co-deposition of both ions did not influence the amount of zinc but slightly increased the amount of copper in the coatings. The release of deposited copper and zinc species was negligible in serum-free simulated body fluid. In protein-containing solutions, a burst release of up to 10 μg ml$^{-1}$ was observed for copper, while zinc was released continuously for up to 14 days. The presence of zinc was beneficial for adhesion and growth of human mesenchymal stromal cells in a concentration-dependent manner, but cytotoxic effects were already visible for coatings with an intermediate copper content. However, co-deposited zinc could somewhat alleviate the adverse effects of copper. Antimicrobial tests with E. coli revealed a decrease in adherent bacteria on brushite without copper or zinc of 60%, but if the coating contained both ions there was almost no bacterial adhesion after 12 h. Coatings with high zinc content and intermediate copper content had the overall best multifunctional properties