Calcium phosphates-based coatings have been extensively used to promote osseointegration of metallic implants. In particular, ion-doped hydroxyapatite thin films, having a composition as similar as possible to host bone, high adhesion to the substrate and surface roughness are desired.
Here, bone apatite-like thin films are proposed, manufactured by Ionized Jet Deposition, by ablation of deproteinized bone targets.
Previously, the Authors have proved the feasibility of the approach and the capability of bovine apatite coatings to promote host cells attachment, proliferation, differentiation, and their osteogenic commitment. Interestingly, coatings exhibited better mechanical and biological behavior compared stoichiometric hydroxyapatite.
Here, because the technique allows for a fine control over composition, different bone sources are used as deposition targets, and composition and morphology of the obtained coatings are compared (GI-XRD, FT-IR, SEM/EDS, AFM). Then, post-deposition annealing treatments (350-450°C) are proposed to optimize films crystallinity, hydrophilicity and adhesion (GI-XRD, contact angle, micro-scratch). Uniformity in deposition on complex geometries, such as bone screws and porous 3D-printed scaffolds is tested (SEM/EDS).
Coatings are primarily proposed for bone implants, but, because deposition occurs at room temperature, they can be of interest for several biomedical devices, including heat sensitive ones. For this reason, feasibility of deposition onto different polymers is demonstrated and possible damage caused to substrate morphology and composition is investigated (SEM/EDS, FT-IR, TGA).
All deposited coatings (≈450 nm thick) are composed of nano-sized globular aggregates and exhibit a nanostructured surface morphology. Thanks to nanostructuration and sub-micrometric thickness, substrate porosity and finishing at the micro-scale are preserved. Composition perfectly reflects that of deposition targets, also in terms of trace ions. Upon annealing at 400°C and above, crystallinity increases up to resembling that of bone, hydrophilicity increases and adhesion is optimized.
Finally, no damage is observed when coatings are deposited onto polymeric substrates, demonstrating the feasibility of the approach.