Model surfaces engineered with nanoscale roughness and RGD tripeptides promote osteoblast activity

Cell adhesion to biomaterials is a prerequisite for tissue integration with the implant surface. Herein, we show that we can generate a model silica surface that contains a minimal-length arginine-glycine-aspartic acid (RGD) peptide that maintains its biological activity. In the first part of this study, attachment of MC3T3-E1 osteoblast-like cells was investigated on silicon oxide, amine terminated substrates [i.e., 3-aminopropyl triethoxysilane (APTS)], grafted RGD, and physisorbed RGD control. The APTS layer exhibited nanoscale roughness and presented amine functional groups for grafting a minimal RGD tripeptide devoid of any flanking groups or spacers. Contact angle measurements indicated that the hydrophobicity of the APTS surface was significantly lower than that of the surface with grafted RGD (RGD-APTS). Atomic force microscopy showed that surfaces covered with RGD-APTS were smoother (Ra = 0.71 nm) than those covered with APTS alone (Ra = 1.59 nm). Focusing mainly on cell morphology, experiments showed that the RGD-APTS hybrid provided an optimum surface for cell adhesion, spreading, and cytoskeletal organization. Discrete focal adhesion plaques were also observed consistent with successful cell signaling events. In a second set of experiments, smooth, monolayers of APTS (Ra = 0.1 nm) were used to prepare arginine-glycine-aspartic acid-serine (RGDS)-APTS and arginine-glycine-glutamic acid-serine (RGES)-APTS (control) substrates. Focusing mainly on cell function, integrin and gene expression were all enhanced for rate osteosarcoma cells on surfaces containing grafted RGDS. Both sets of studies demonstrated that grafted molecules of RGD(S) enhance both osteoblast-like cell adhesion and function.