Abstract
The effect of a glutamic acid (negatively charged) peptide (Glu6), which mimics the terminal region of the osteonectin glycoprotein of bone on the shear modulus of a synthetic hydorgel/apatite nanocomposite, was investigated. One end of the synthesized peptide was functionalized with an acrylate group (Ac‐Glu6) to covalently attach the peptide to the hydrogel phase of the composite matrix. The addition of Ac‐Glu6 to hydroxyapatite (HA) nanoparticles (50 nm in size) resulted in significant reinforcement of the shear modulus of the nanocomposite (∼100% increase in elastic shear modulus). The reinforcement effect of the Glu6 peptide, a sequence in the terminal region of osteonectin, was modulated by the size of the apatite crystals. A molecular model is also proposed to demonstrate the role of polymer‐apatite interaction in improving the viscoelastic behavior of the bone mimetic composite. The predictions of the model were compared with the measured dynamic shear modulus of the PLEOF hydrogel reinforced with HA nanoparticles. This predictive model provides a quantitative framework to optimize the properties of reinforced polymer nanocomposites as scaffolds for applications in tissue regeneration.
Highlights
Synthetic degradable and biomimetic polymer nanocomposites are an ideal replacement material for orthopedics and dental applications because of minimum risk of disease transfer, reduced stress shielding and particulate wear, and the ability to couple polymer degradation with tissue regeneration
It is believed that the first seventeen NH2-terminal amino acids of osteonectin are responsible for binding to the bone collagen network [13], while a glutamic acid-rich sequence binds to the bone HA nanoparticles, due to its high ionic affinity for calcium ions [12]
Predictions of the model are compared with the measured dynamic shear modulus of the PLEOF hydrogel reinforced with HA nanoparticles
Summary
Synthetic degradable and biomimetic polymer nanocomposites are an ideal replacement material for orthopedics and dental applications because of minimum risk of disease transfer, reduced stress shielding and particulate wear, and the ability to couple polymer degradation with tissue regeneration. Injectable hydrogels seeded with cells and growth factors and coupled with minimally invasive arthroscopic techniques are an attractive alternative for treating irregularly shaped degenerated hard tissues. Marrow stromal cells, isolated from the bone marrow, and growth factors can be placed in a supportive hydrogel and injected into an osteochondral defect by a minimally invasive arthroscopic procedure [1,2,3,4,5]. A variety of multifunctional composite materials have been developed to mimic the organized nanostructure of the bone, which consists of the collagenous matrix and mineralized apatite nanocrystals [6,7,8]. One of the NCPs with bone specific functions is osteonectin which has a strong affinity for both collagen and hydroxyapatite (HA), and it is speculated to be a bone-specific nucleator of mineralization [11, 12]. It is believed that the first seventeen NH2-terminal amino acids of osteonectin are responsible for binding to the bone collagen network [13], while a glutamic acid-rich sequence binds to the bone HA nanoparticles, due to its high ionic affinity for calcium ions [12]
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