Direct role of interrod spacing in mediating cell adhesion on Sr-HA nanorod-patterned coatings

Abstract

The process in which nanostructured surfaces mediate cell adhesion is not well understood, and may be indirect (via protein adsorption) or direct. We prepared Sr-doped hydroxyapatite (Sr 1 -HA) 3D nanorods (with interrod spacing of 67.3±3.8, 95.7±4.2, and 136.8±8.7 nm) and 2D nanogranulate patterned coatings on titanium. Employing the coatings under the same surface chemistry and roughness, we investigated the indirect/direct role of Sr 1 -HA nanotopographies in the regulation of osteoblast adhesion in both serum-free and serum-containing Dulbecco’s Modified Eagle/Ham’s Medium. The results reveal that the number of adherent cells, cell-secreted anchoring proteins (fibronectin, vitronectin, and collagen), vinculin and focal adhesion kinase (FAK) denoted focal adhesion (FA) contact, and gene expression of vinculin, FAK, and integrin subunits (α 2 , α 5 , α v , β 1 , and β 3 ), undergo significant changes in the inter-nanorod spacing and dimensionality of Sr 1 -HA nanotopographies in the absence of serum; they are significantly enhanced on the <96 nm spaced nanorods and more pronounced with decreasing interrod spacing. However, they are inhibited on the >96 nm spaced nanorods compared to nanogranulated 2D topography. Although the adsorption of fibronectin and vitronectin from serum are higher on 136.8±8.7 nm spaced nanorod patterned topography than nanogranulated topography, cell adhesion is inhibited on the former compared to the latter in the presence of serum, further suggesting that reduced cell adhesion is independent of protein adsorption. It is clearly indicated that 3D nanotopography can directly modulate cell adhesion by regulating integrins, which subsequently mediate anchoring proteins’ secretion and FA formation rather than via protein adsorption.

Surface Immobilization of TiO2 Nanotubes with Bone Morphogenetic Protein-2 Synergistically Enhances Initial Preosteoblast Adhesion and Osseointegration

“…It also promotes integrin clustering and composes and stabilizes focal adhesion (FA) [37]. Previous studies suggested that nanotopography formed by AO induces higher cell adhesion in osteoblast cells [14, 38]. hBMP-2 is also shown to be able to induce higher vinculin protein expression in osteoblasts [32].…”

“…To further verify the osteogenic potential of modified surfaces, we employed a rat model to investigate the osseointegration properties in vivo . It is reported that the anodized surface could not only promote cell attachment so as to improve osseointegration [38], but also inhibit bacterial adhesion, which has adverse effects on the success of implant biomaterials [44]. Furthermore, precious study revealed that 70 nm is the optimum size of TiO 2 nanotube diameter for osteoconductivity and osseointegration [27].…”

Silver-nanoparticles-modified biomaterial surface resistant to staphylococcus: new insight into the antimicrobial action of silver

“…This inspired us to investigate the HCM as a promising strategy for loading Ag onto Ti surface. In addition, a PEO-fabricated titania (TiO 2 ) coating was selected for the pre-modifying layer on the Ti surface because PEO can produce porous, homogeneous and firmly adherent titania layers with favorable biocompatibility and bioactivity 27 28 29 30 . Moreover, previous literatures have manifested that inorganic ions deposited on the porous titania coating could present a pattern of sustained release instead of explosive release 31 32 .…”

Different methods of hydroxyapatite‐based coatings on external fixator pin with high adhesion approach

“…[32,[150][151][152] Nowadays, different methods are used to improve the biological activity of HA-coated via the MAO, such as the sol-gel method, alkali treatment, and hydrothermal method. [153] Among them, hydrothermal is the most effective method because it can reduce the Ca and P values in the MAO coating, which leads to making for a weak interface bonding strength between the substrate and MAO layer. [154,155] It is confirmed that the surface structure and phase compositions after coating are so crucial for osseointegrating.…”