Abstract
Alumina (Al2O3) ceramic implants do not stimulate osteoblasts in vivo. Surface alterations targeted at changing the chemistry or topography have been proposed to enhance the bioactivity of alumina. This surface modification is intended to improve oxide bioceramic’s ability to integrate with the biological environment and, in particular, to rapidly osteointegrate. In this study, the surface of zirconia-toughened alumina (ZTA) was functionalized using two methods: (i) Surface laser-patterning and successive filling of patterned wells with powder mixtures of bioglass and Si3N4; and, (ii) Si3N4 coating by pulse-laser sintering. Functionalized ZTA surfaces were characterized with vibrational spectroscopy, biological testing, and laser microscopy. Both enhancements resulted in osteoblast activation, a property that is relevant to osteosynthesis.
Highlights
During bone formation, organic matrix is synthesized by cells secreting a variety of glycoproteins, genetic markers, and bone sialoprotein [1]
zirconia-toughened alumina (ZTA) partially melted under the laser beam; the molten material was ejected from the well producing some roughening in the neighborhood of the well border
We selected a diameter of 500 μm for the patterned wells, consistent with pore sizes used in bone fusion implants clinically [24,25,26,27]
Summary
During bone formation, organic matrix (i.e., predominantly collagen type I) is synthesized by cells secreting a variety of glycoproteins, genetic markers, and bone sialoprotein [1]. A favorable environment for cellular apatite mineralization relies on local supersaturation of extra-cellular fluids with osteoblastic alkaline phosphatase (ALP), pyrophosphatase activity, and osteocalcin production. Ceramic materials are considered to be bioinert [4,5], they can stimulate or suppress osteoblastic activity [6,7]. Silicon nitride (Si3 N4 ) ceramic implants are known to accelerate bone repair because of the surface chemistry of the material [8,9,10,11]. The release of silicic acid and reactive nitrogen species (RNS) on Si3 N4 surfaces enhances osteogenic activity in osteosarcoma and mesenchymal cells [8,9,10]. Analyses of a retrieved Si3 N4 human cervical fusion implant have confirmed the incorporation of silicon and nitrogen into the crystal lattice of native hydroxyapatite [11]
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