Arginine-glycine-aspartic acid modified rosette nanotube–hydrogel composites for bone tissue engineering

An RGDSK (Arg-Gly-Asp-Ser-Lys) modified rosette nanotube (RNT) hydrogel composite with unique surface chemistry and favorable cytocompatibility properties for bone repair was developed and investigated. The RNTs are biologically inspired nanomaterials obtained through the self-assembly of a DNA base analog (G∧C base) with tailorable chemical functionality and physical properties. In this study, a cell-adhesive RGDSK peptide was covalently attached to the G∧C base, assembled into RNTs, and structurally characterized by 1H/13C NMR spectroscopy, mass spectrometry, and electron microscopy. Importantly, results showed that the RGDSK modified RNT hydrogels caused around a 200% increase in osteoblast (bone-forming cell) adhesion relative to hydrogel controls. In addition, osteoblast proliferation was enhanced on RNT hydrogels compared to hydrogel controls after 3 days, which further confirmed the promising cytocompatibility properties of this scaffold. When analyzing the mechanism of increased osteoblast density on RNT hydrogels, it was found that more fibronectin (a protein which promotes osteoblast adhesion) adsorption occurred on RNT coated hydrogels than uncoated hydrogels. As osteoblast adhesion was greatly enhanced on RNT coated hydrogels compared to poly l-lysine and collagen coated hydrogels, this study indicated that not only the surface chemistry was important in improving osteoblast density (via lysine or RGD groups functionalized on RNTs), but also the biomimetic nanoscale properties of RNTs provided a cell-favorable environment. These results warrant further studies on RNTs in hydrogels for better bone tissue regeneration.