Nanoscale Coatings for Ultralow Dose BMP-2-Driven Regeneration of Critical-Sized Bone Defects.

While new biomaterials for regenerative therapies are being reported in the literature, clinical translation is slow. Some existing regenerative approaches rely on high doses of growth factors, such as bone morphogenetic protein-2 (BMP-2) in bone regeneration, which can cause serious side effects. An ultralow-dose growth factor technology is described yielding high bioactivity based on a simple polymer, poly(ethyl acrylate) (PEA), and mechanisms to drive stem cell differentiation and bone regeneration in a critical-sized murine defect model with translation to a clinical veterinary setting are reported. This material-based technology triggers spontaneous fibronectin organization and stimulates growth factor signalling, enabling synergistic integrin and BMP-2 receptor activation in mesenchymal stem cells. To translate this technology, plasma-polymerized PEA is used on 2D and 3D substrates to enhance cell signalling in vitro, showing the complete healing of a critical-sized bone injury in mice in vivo. Efficacy is demonstrated in a Münsterländer dog with a nonhealing humerus fracture, establishing the clinical translation of advanced ultralow-dose growth factor treatment.

Material-driven fibronectin assembly for high-efficiency presentation of growth factors.

Growth factors (GFs) are powerful signaling molecules with the potential to drive regenerative strategies, including bone repair and vascularization. However, GFs are typically delivered in soluble format at supraphysiological doses because of rapid clearance and limited therapeutic impact. These high doses have serious side effects and are expensive. Although it is well established that GF interactions with extracellular matrix proteins such as fibronectin control GF presentation and activity, a translation-ready approach to unlocking GF potential has not been realized. We demonstrate a simple, robust, and controlled material-based approach to enhance the activity of GFs during tissue healing. The underlying mechanism is based on spontaneous fibrillar organization of fibronectin driven by adsorption onto the polymer poly(ethyl acrylate). Fibrillar fibronectin on this polymer, but not a globular conformation obtained on control polymers, promotes synergistic presentation of integrin-binding sites and bound bone morphogenetic protein 2 (BMP-2), which enhances mesenchymal stem cell osteogenesis in vitro and drives full regeneration of a nonhealing bone defect in vivo at low GF concentrations. This simple and translatable technology could unlock the full regenerative potential of GF therapies while improving safety and cost-effectiveness.

Comparison of the density of proteins and peptides grafted on silane layers and polyelectrolyte multilayers.

Immobilized proteins or peptides are of critical importance for applications such as biosensing or cell culture. We analyze the structure of layers of a large variety of proteins and peptides, grafted on silicon substrates by different routes differing in the nature of the intermediate layer linking the biomolecules to the substrate, either a silane monolayer, or a polyelectrolyte multilayer made from synthetic or natural polymers. The structural analysis is essentially performed by X-ray reflectometry, which proves to be an efficient methodology not requiring the use of tagged biomolecules, capable of evaluating consistently the amount of grafted biomolecules per surface area with estimated precisions ranging from 10 to 20%. The study provides a quantitative basis for selecting one among a series of well-proofed and sturdy grafting methodologies and underlines the potential of XRR for assessing the amount of grafted biomacromolecules without requiring the expensive tagging of molecules. Our results also show that, for the coupling route resting on synthetic polyelectrolytes, the grafting density is significantly lower than for direct coupling over a silane layer. In contrast, when performed over a cushion based on polysaccharides, the grafting density is well above the values found for a dense layer grafted on a silane monolayer, indicating partial penetration and swelling of the polysaccharide cushion.

Bioactive chemical nanopatterns impact human mesenchymal stem cell fate.

We present a method of preparing and characterizing nanostructured bioactive motifs using a combination of nanoimprint lithography and surface functionalization. Nanodots were fabricated on silicon surfaces and modified with a cell-adhesive RGD peptide for studies in human mesenchymal stem cell adhesion and differentiation. We report that bioactive nanostructures induce mature focal adhesions on human mesenchymal stem cells with an impact on their behavior and dynamics specifically in terms of cell spreading, cell-material contact, and cell differentiation.