Enhanced osteoblast functions of narrow interligand spaced Sr-HA nano-fibers/rods grown on microporous titania coatings

Abstract

Nanofibrous and nanorod-shaped Sr₁-HA with lateral spacing less than 100 nm, and nanogranulated Ca_0.5Sr_0.5TiO₃ were hydrothermally grown on micro-arc oxidized microporous and nanocrystallized TiO₂, respectively, to form multilayers coatings. The multi-layer coatings and the MAOed coating reveal two kinds of micro/nano-scaled hierarchical surfaces with a similar microscale roughness, e.g., nano-granulated/crystallized 2D pattern and nano-fibrous/rod-shaped 3D pattern in nanotopography. They can firmly adhere to Ti substrates and exhibit long-term structure and adhesive strength stability as indicated by immersion tests in physiological saline solutions for 0–24 weeks. The adsorption of total protein and anchoring proteins such as vitronectin and fibronectin on the coatings from DMEM medium containing 10% fetal bovine serum was examined. Employing hFOB1.19 cells, the behaviors of osteoblast on the coatings, including adhesion, proliferation and differentiation, were evaluated by examining the number of adherent cells, cytoskeleton, focal adhesion formation, expressions of steogenesis-related genes (ALP, Runx2, osterix, BSP, osteopontin, osteocalcin, osteonectin and Col-I), ALP activity, contents of intracellular Ca²⁺ and Col-I, extracellular collagen secretion, and extracellular matrix mineralization. The nanofibrous and nanorod-shaped Sr₁-HA constructed 3D patterns (especially nanofibrous Sr₁-HA) significantly enhance adhesion, proliferation, maturation and mineralization of osteoblasts compared to the nanocrystallized TiO₂ and nanogranulated Ca_0.5Sr_0.5TiO₃ constructed 2D patterns and Ti. In addition, the efficacy of interligand (e.g., interfiber/rod) spacing of the 3D nanotopographies, protein adsorption and the difference in chemical composition of the coatings to cell adhesion, proliferation or differentiation is identified.