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Titanium and titanium alloys are widely used in orthopedic implants. Modifying the nanotopography provides a new strategy to improve osseointegration of titanium substrates. Filamentous actin (F-actin) polymerization, as a mechanical loading structure, is generally considered to be involved in cell migration, endocytosis, cell division, and cell shape maintenance. Whether F-actin is involved and how it functions in nanotube-induced osteogenic differentiation of mesenchymal stem cells (MSCs) remain to be elucidated. In this study, we fabricated TiO2 nanotubes on the surface of a titanium substrate by anodic oxidation and characterized their features by scanning electron microscopy (SEM), X-ray energy dispersive analysis (EDS), and atomic force microscopy (AFM). Alkaline phosphatase (ALP) staining, Western blotting, qRT-PCR, and immunofluorescence staining were performed to explore the osteogenic potential, the level of F-actin, and the expression of MKL1 and YAP/TAZ. Our results showed that the inner diameter and roughness of TiO2 nanotubes increased with the increase of the anodic oxidation voltage from 30 to 70 V, while their height was 2 μm consistently. Further, the larger the tube diameter, the stronger the ability of TiO2 nanotubes to promote osteogenic differentiation of MSCs. Inhibiting F-actin polymerization by Cyto D inhibited osteogenic differentiation of MSCs as well as the expression of proteins contained in focal adhesion complexes such as vinculin (VCL) and focal adhesion kinase (FAK). In contrast, after Jasp treatment, polymerization of F-actin enhanced the expression of RhoA and transcription factors YAP/TAZ. Based on these data, we concluded that TiO2 nanotubes facilitated the osteogenic differentiation of MSCs, and this ability was enhanced with the increasing diameter of the nanotubes within a certain range (30–70 V). F-actin mediated this process through MKL1 and YAP/TAZ.

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A new corn starch adhesive modified by starch‐g‐polyvinyl acetate (starch‐g‐PVAc) and epoxy resin is described in this study. Starch‐g‐PVAc is used as high cohesive energy component to improve the dry shear strength of the starch adhesive. Although the epoxy resin, which can easily crosslink with the oxidized starch, is used as water‐resistant component to improve the wet shear strength. Because there is no chemical reaction happening between polyvinyl acetate and epoxy resin, both the dry shear strength and the wet shear strength of the corn starch adhesive are notably increased. Considering all the related factors, the optimum of the modification is achieved when the dosage of starch‐g‐PVAc and epoxy resin is 70% of the oxidized starch latex with m(Ep): m(starch‐g‐PVAc) = 1:2. That is, the epoxy resin is 23% in mass fraction and starch‐g‐PVAc 47% in mass fraction. The dry shear strength is 4.50 MPa, and the wet shear strength is 2.51 MPa. The modified corn starch has a broad prospect in the application of plywood industry. POLYM. COMPOS., 2013. © 2012 Society of Plastics Engineers