Antibacterial Properties of Ag-modified Ca-Phosphate Scaffolds for Bone Implant Applications
Final Report Abstract
Hydrothermal conversion of biogenic carbonate scaffolds and vapor-phase transport sintering (VTS) in AgCl atmosphere where combined to produce interconnected pore geometry and phase composition to allow for the application as bone graft ceramics. In addition, surface modification with Ag-containing phases was accomplished throughout this processing technique. The Mg-content of the carbonate starting materials employed, i.e., coral skeletons and sea urchin spines, determines the final phase composition of the final product upon conversion stabilizing Mg-bearing β-TCP at the expense of HA. Sintering in AgCl atmosphere facilitates both, microstructural coarsening without macropore shrinkage as well as condensation of finely dispersed AgCl and Ag3PO4 particles at pore surfaces of the scaffold. Representing a novel class of ceramic composites, these materials are promising candidates regarding the antibacterial properties of Ag+ ions. Moreover, the major phases present in the converted scaffolds remain stable during VTS, allowing for the fabrication of either HA or Mg-TCP ceramics. For both types of the Ag-modified ceramics it was shown via silver ion dissolution kinetics that Ag+ was immediately released into the aqueous solution and reached the solubility equilibrium within only a few hours. Hence, Ag+ availability was confirmed as the precondition for potential antibacterial activity. Both Ag-modified ceramics indeed revealed an antimicrobial effect, which was stronger for Gram-positive bacteria as for Gram-negative bacteria. Growth inhibition studies with Ag+ solutions suggest that the antibacterial effect of the ceramic originates from the phase assemblage of AgCl and Ag3PO4 present at pore surfaces.
Publications
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Combined Hydrothermal Conversion and Vapor Transport Sintering of Ag-Modified Calcium Phosphate Scaffolds. J. Am. Ceram. Soc., 96 [2] 412–419 (2013)
Margarete Schlosser, Sabrina Fröls, Ulla Hauf, Ingo Sethmann, Stefanie Schultheiss, Felicitas Pfeifer, and Hans-Joachim Kleebe
