Covalent Binding of Bone Morphogenetic Protein‐2 and Transforming Growth Factor‐β3 to 3D Plotted Scaffolds for Osteochondral Tissue Regeneration

Abstract

Engineering the osteochondral tissue presents some challenges mainly relying in its function of transition from the subchondral bone to articular cartilage and the gradual variation in several biological, mechanical, and structural features. A possible solution for osteochondral regeneration might be the design and fabrication of scaffolds presenting a gradient able to mimic this transition. Covalent binding of biological factors proved to enhance cell adhesion and differentiation in two-dimensional culture substrates. Here, we used polymer brushes as selective linkers of bone morphogenetic protein-2 (BMP-2) and transforming growth factor-β3 (TGF-β3) on the surface of 3D scaffolds fabricated via additive manufacturing (AM) and subsequent controlled radical polymerization. These growth factors (GFs) are known to stimulate the differentiation of human mesenchymal stromal cells (hMSCs) toward the osteogenic and chondrogenic lineages, respectively. BMP-2 and TGF-β3 were covalently bound both homogeneously within a poly(ethylene glycol) (PEG)-based brush-functionalized scaffolds, and following a gradient composition by varying their concentration along the axial section of the 3D constructs. Following an approach previously developed by our group and proved to be successful to generate fibronectin gradients, opposite brush-supported gradients of BMP-2 and TGF-β3 were finally generated and subsequently tested to differentiate cells in a gradient fashion. The brush-supported GFs significantly influenced hMSCs osteochondral differentiation when the scaffolds were homogenously modified, yet no effect was observed in the gradient scaffolds. Therefore, this technique seems promising to maintain the biological activity of growth factors covalently linked to 3D scaffolds, but needs to be further optimized in case biological gradients are desired.

Bone tissue engineering via growth factor delivery: from scaffolds to complex matrices

“…Di Luca et al explored covalent binding of GFs to additively manufactured 3D scaffolds [ 80 ]. Additively manufactured poly(ε-caprolactone) scaffolds were modified with functionalizable poly(oligo (ethylene glycol) methacrylate) (POEGMA) brushes, which were subsequently functionalized with BMP-2 and TGF-β3.…”

Immobilization of nanocarriers within a porous chitosan scaffold for the sustained delivery of growth factors in bone tissue engineering applications

“…While covalent binding approaches have previously been used for growth factor delivery applications, the previous systems rely on the covalent binding of the growth factors themselves to the scaffold backbone. However, this method poses concerns due to the negative effects on protein bioactivity (Di Luca et al, ).…”

“…The second category of techniques that are based on the covalent binding of proteins to scaffolds lead to constant, sustained protein release profiles. These techniques fail to prevent the rapid degradation and loss of bioactivity of the protein (Di Luca et al, ). Finally, the incorporation of proteins into particles has shown great promise for controlled release and is able to both protect the protein and provide a delivery profile consisting of an initial burst release followed by a short, sustained release (Bessa et al, ; Subbiah et al, ).…”

Engineered Extracellular Vesicles: Tailored-Made Nanomaterials for Medical Applications

“…With EVs exhibiting a negative charge, this presents the potential to immobilise these nanoparticles within biomaterials via electrostatic interactions [ 123 ]. Conjugating EVs with the biomaterial via covalent modification would provide the strongest immobilisation method, which would eliminate burst release and prolong delivery, similar to what has been shown for growth factors [ 124 , 125 ]. In addition to controlling the EVs release kinetics, the mode of delivery is an essential consideration for biomaterial design.…”