Papers by Author: J.L. Xu

Abstract: Hydroxyapatite (HA) is a bioactive ceramic material with a chemical composition similar to natural bone, and carbon nano tubes (CNT) is able to enhance the brittle ceramic matrix without detrimental to the bioactivity. This study reported an attempt to use a commercially multiwalled CNT strengthen brittle hydroxyapatite bioceramics. Using iTRAQ-coupled 2D LCMS/ MS analysis, we report the first study of protein profile in osteoblasts from human osteoblastic cell line incubated separately on HA with and without strengthening multiwall CNT surfaces. Sixty proteins were identified and quantified simultaneously at the initial culturing stage of 3 days. The results were validated by Western blotting for selected proteins: Fetuin-A, Elongation factor II and Peroxiredoxin VI. Fetuin-A showed up-regulation, and Peroxiredoxin VI gave down-regulation in the osteoblasts cultured on HA based ceramic surfaces. Similar regulation was expressed by the protein of Elongation factor II on the phase pure HA surfaces as compared to the control group cultured on the polystyrene substrate. Relatively high EF 2 expression was detected on the phase the surfaces of CNT strengthen HA samples.

Abstract: Hydroxyapatite based biomaterials were prepared by a spark plasma sintering technology. The human limb-derived osteoblasts were cultured on the various biomaterial surfaces (HA, RF21, 1SiHA and 5SiHA) for up to two weeks to investigate the cellular behaviors. The bone gammacarboxyglutamic protein or osteocalcin in the medium were determined at different periods of cell culture. The results indicated that a combined effect of bioceramic surface composition and surface morphology had influenced the osteoblast behaviors. The amount of osteocalcin in the medium increased in the initial periods of culture but decreased in the late periods of culture.

Abstract: It was a normal phenomena that hydroxyapatite (HA) decomposes into tricalcium phosphate (TCP), tetracalcium phosphate (TTCP), calcium oxide (CaO) and amorphous calcium phosphate (ACP) during the plasma processing step. The present study characterized the phase evolution of calcium phosphates (CaPs) in the nanoparticles synthesized using a radio frequency (RF) induction plasma processing technique. The morphology and microstructure of the CaP nanoparticles were investigated by XRD, SEM, TEM, Raman spectroscopy, FTIR spectroscopy and thermal analysis. It was found that ACP, α-TCP, TTCP and CaO were the main decomposed phases in the nanoparticle. After heat treatment at dicalcium pyrophosphate (β-Ca2P2O7) due to the extreme decomposition of the starting HA during the RF plasma processing step which rapidly solidified into amorphous phase.