Biogenic and biomimetic nanocoatings for bone modelling and regeneration

Jun 29, 2022, 2:30 PM
Room: S4 B

Room: S4 B


Graziani, Gabriela (IRCCS Istituto Ortopedico Rizzoli, Laboratory of Biotechnology )


Bone is a complex composite material, so any scaffold or model designed to reconstruct its integrity or model its behaviour must have a high degree of complexity and fulfil several requirements, including high biocompatibility, suitable surface and mechanical properties, adequate architecture, tailored degradability. Obtaining a bone-mimetic composition is also crucial, because hydroxyapatite (HA), the mineral phase of bone, dictates the behaviour of both healthy and tumour cells.
Here, for bone regeneration and modelling purposes, biomimetic nanostructured coatings are designed, manufactured by Ionized Jet Deposition (IJD) and deposited onto 3D printed metallic and polymeric scaffolds.
Coatings are obtained by ablation of biogenic hydroxyapatite, derived from bovine bone. Polymeric scaffolds are obtained by Fused Deposition Modelling of PLA filaments, while metallic scaffolds are obtained by selective laser sintering starting from Ti-6Al-4V powder.
Surface morphology (FEG-SEM, AFM), composition (GI-XRD, FT-IR, EDS) and stability profile in culture medium (immersion in alpha-MEM at pH 7.4 and FEG-SEM at 24h, 7 days and 14 days) are assessed, for the coatings. Then, coverage of the 3D printed coatings is optimized and the relevance of shadowing effects is evaluated.
Finally, the interactions between the coatings and cells (MSCs for bone regeneration and SAOS-2 for bone tumour modelling) is assessed, by studying their adhesion to the scaffolds, morphology, early proliferation and differentiation (for the MSCs).
Coatings have a submicrometric thickness, that can be selected by tuning deposition time, nanostructured surface morphology and biomimetic composition. Indeed, the nanostructured coatings are constituted by multi-doped carbonated hydroxyapatite (Na 0.28 ± 0.08, Mg 0.16 ± 0.01 wt%) and are constituted of nanoscale aggregates (diameter ~ 50 nm) grouping in clusters up to 2 microns diameter. A nominal thickness of 450 nm is selected. Upon exposure in medium, they progressively dissolve, but maintain stability for over 14 days. Upon deposition on the 3D printed scaffolds, nanostructured coatings grow on all the surface of the fibres without altering their shape or porosity and coat their entire surface with no shadowing effects.
In addition, they promote cells colonization of the whole scaffolds, different from controls, where cells tend to concentrate on the outer layers.
For bone regeneration, coatings dictate MSCs morphology and sustain early proliferation and differentiation towards an osteogenic lineage. For bone models, they permit optimal viability at early and late timepoints.
As a consequence, the developed coatings appear promising for applications in regenerative medicine and bone modelling.

ACKNOWLEDGEMENTS: Funding from 5 per mille provided to IRCCS - Istituto Ortopedico Rizzoli, and from the Euronanomed III project NANOVERTEBRA is acknowledged.


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