Electrochemically assisted deposition of trace element modified calcium and magnesium phosphate coatings on titanium for improved implant healing in osteoporotic bone

• Applicants: Professor Dr. Uwe Gbureck, since 2/2017; Dr. Cornelia Wolf-Brandstetter
• Subject Area: Biomaterials
• Term: from 2014 to 2019
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 250488887

Implants made from titanium and its alloys are well-established biomaterials and have been in use for load-bearing applications as well as for implantation into soft tissue for decades. Despite the generally good implant success rates concerning healing and retention time there is still a need for further improvements, particularly for use in more challenging situations, e.g. in the case of a weakened osseous bed caused by systemic diseases like osteoporosis. Hence the aim of this project is to further improve implant integration, specifically during the initial healing phase, by using inorganic bioactive mediators: Controlled release of the trace elements copper and zinc can stimulate vascularization, while chemotactic zinc ions recruit and stimulate osteogenic cells, and strontium release reduces osteoclastic activity. In combination, these effects are expected to increase bone formation adjacent to the modified surfaces.During the first project phase, the immobilization and controlled release of the separate trace elements could be established in calcium and magnesium phosphate coatings, namely brushite (CaHPO4 * 2H2O) and struvite (MgNH4PO4 * 6H2O), deposited on titanium substrates. The second 12-month project phase is dedicated to the fabrication and characterization of coating systems which will combine several trace elements to obtain synergetic effects of their specific biological activities.The resulting coatings will be examined regarding their physicochemical properties, namely their quantitative composition, morphology, crystallinity, as well as the distribution of the incorporated trace elements and their oxidation state. In particular, the newly available focused ion beam (FIB) technique will be combined with release studies in order to analyze the influence of the local coating composition on the release kinetics of the trace elements.For the evaluation of the angiogenetic potential both endothelial cell monocultures in 2D and 3D techniques as well as co-cultures with other cell types relevant for angiogenesis in vivo will be used. In particular the influence of the trace metal ions on the interaction of endothelial cells with monocytes and smooth muscle cells will be analyzed. Both the osteoblast activating potential of zinc and the osteoclast inhibiting activity of strontium containing coatings will be evaluated by means of colonization with an osteoblast (MG63) or an osteoclast (RAW) cell line, respectively.In a first animal study, both the effect of the strontium concentration in the coating and the effect of the coating matrix (struvite or brushite) will be examined. Utilizing the bioactive effects of the mentioned trace elements as an alternative to growth factors with comparable effects is believed to improve the performance of implants in a likewise manner, but with a higher safety margin.

• DFG Programme: Research Grants
• Co-Investigator: Privatdozent Dr. Wolfgang Metzger
• Ehemaliger Antragsteller: Dr. Claus Moseke, until 2/2017