Mesenchymal Stem Cell Responses to Bone-Mimetic Electrospun Matrices Composed of Polycaprolactone, Collagen I and Nanoparticulate Hydroxyapatite

The performance of biomaterials designed for bone repair depends, in part, on the ability of the material to support the adhesion and survival of mesenchymal stem cells (MSCs). In this study, a nanofibrous bone-mimicking scaffold was electrospun from a mixture of polycaprolactone (PCL), collagen I, and hydroxyapatite (HA) nanoparticles with a dry weight ratio of 50/30/20 respectively (PCL/col/HA). The cytocompatibility of this tri-component scaffold was compared with three other scaffold formulations: 100% PCL (PCL), 100% collagen I (col), and a bi-component scaffold containing 80% PCL/20% HA (PCL/HA). Scanning electron microscopy, fluorescent live cell imaging, and MTS assays showed that MSCs adhered to the PCL, PCL/HA and PCL/col/HA scaffolds, however more rapid cell spreading and significantly greater cell proliferation was observed for MSCs on the tri-component bone-mimetic scaffolds. In contrast, the col scaffolds did not support cell spreading or survival, possibly due to the low tensile modulus of this material. PCL/col/HA scaffolds adsorbed a substantially greater quantity of the adhesive proteins, fibronectin and vitronectin, than PCL or PCL/HA following in vitro exposure to serum, or placement into rat tibiae, which may have contributed to the favorable cell responses to the tri-component substrates. In addition, cells seeded onto PCL/col/HA scaffolds showed markedly increased levels of phosphorylated FAK, a marker of integrin activation and a signaling molecule known to be important for directing cell survival and osteoblastic differentiation. Collectively these results suggest that electrospun bone-mimetic matrices serve as promising degradable substrates for bone regenerative applications

Cold spray coating of submicronic ceramic particles on poly(vinyl alcohol) in dry and hydrogel states

International audienceThis study demonstrates that cold spray technology offers a route to functionalize the surface of PVA pieces with ceramic (HA) coatings. Swollen PVA hydrogels could not sustain the heat and deformation produced by the spraying process. Dry PVA substrates, however, could be efficiently coated using a technologically relevant range of spraying energy parameters. By adjusting the fragmentation of the sprayed powder, one can produce fine HA coatings of submicron fragments embedded into the PVA substrate surface. The binding of these HA particles to the PVA substrate is strong enough to withstand swelling in water, enabling formation of HA-coated hydrogels by immersion in water after spraying. A microscopic picture of the coating formation is proposed, where the PVA substrate melts superficially within a microscopic layer and sprayed aggregates fragment upon impact with the substrate, therefore inducing surface roughening and strong binding of the HA fragments to the molten PVA layer. More generally, these results using one type of aggregated powder suggest that adjusting the nature of the sprayed powder (aggregate size, cohesiveness, porosity, composition, etc.) could be a promising strategy to tailor the morphology of such coatings produced by cold spray; For instance, thick layers could be deposited by cold spray on various substrates, including PVA and Ti-6Al-V, thanks to the binding action of residual byproducts of the chemical synthesis of HA particles (Ref 39). With the recent progress in the design of bioactive ceramics (Ref 40), such a cold-spray-based approach offers an interesting possibility to functionalize the surface of polymer implants with fine control of the ceramic composition and crystallinity