Multi-doped Calcium-Phosphate coatings for resorbable magnesium alloy implant applications

Calcium Phosphate (CaP) coatings have been shown to delay the corrosion of Magnesium (Mg) implants in-vitro enabling the potential use of Magnesium as a material to design resorbable bone fixation devices such as, screws, ESINs (elastic stable intramedullary nails) and k-wires. Calcium Phosphate coatings are of particular interest as these are stoichiometric derivatives of hydroxyapatite (HA), the mineral constituent of bone. This will mean that the coatings can also potentially offer a benefit to surrounding cells/tissues post-implantation. This effect on cells/tissues is yet to be fully understood, this work will investigate in detail the relationship between amorphous CaP coated Mg alloys and cells in-vivo. HA in the body is doped with many different ions, which offer a variety of potential benefits from increasing proliferation of surrounding cells to promoting differentiation of osteoprogenitor cells down osteoblast lineages. This work will combine and build upon previous experience in CaP coatings on Magnesium and ion-doping of CaP coatings to produce coatings doped with various beneficial ions (Zn, Sr, Ag, Cu, F). Parametric studies will be conducted to determine the optimal ion-doping strategy to create a coating which can not only delay the onset of corrosion but also promote positive surrounding cell activity at the implant site enabling a more rapid healing process. Up until this point these coatings have only been deposited on lab appropriate samples, flat small coupons for testing purposes. Research into RF-Magnetron sputtering onto complex 3D shapes is required to allow for deposition of these coatings onto implant devices. Initial work by the group has studied the shear properties of the coatings, to better understand how the coating will behave on a potential implant device, with the development of a method to coat 3D implant devices, coating integrity post-implantation needs to be subsequently investigated and potentially optimised through treatments such as laser annealing to create a crystalline structure.