Effect of V/Mo Atomic Ratio on the Microstructure and Mechanical Properties of MoVCuN Coatings.

To improve the gas ionization ratio, the Mo-V-Cu-N coatings were deposited by pulsed dc magnetron sputtering with assistance from an anode layer ion source, and the influence of the V/Mo atomic ratio was explored with regard to the microstructure and mechanical properties of the coatings. The findings of this study indicated that the MoVCuN coatings exhibited a solid solution phase of FCC B1-MoVN with a prominent (220) preferred orientation, and the deposition rate was found to decrease from 4.7 to 1.8 nm/min when the V/Mo atomic ratio increased. The average surface roughness of the MoVCuN coatings gradually decreased, and the lowest surface roughness of 6.9 nm was achieved at a V/Mo atomic ratio of 0.31. Due to the enhanced ion bombardment effect, the coatings changed from a coarse columnar to a dense columnar crystal structure, and promoted grain refinement at higher V/Mo atomic ratios, contributing to a gradual improvement in the compressive residual stress, hardness and adhesion strength of the coatings.

Relaxin enhances bone regeneration with BMP-2-loaded hydroxyapatite microspheres.

Our aims were to 1) evaluate the capacity of hollow hydroxyapatite (HA) microspheres (212-250 µm) to serve as a delivery system for controlled release of BMP-2 in vitro and 2) examine relaxin as an enhancer of BMP-2 for bone regeneration. Hollow HA microspheres were converted from borate glass microspheres and characterized using X-ray diffraction, Fourier-transform infrared spectroscopy, scanning electron microscopy, and the Brunauer-Emmett-Teller method. The microspheres loaded with BMP-2 and relaxin were implanted for 6 weeks in Sprague Dawley rats with calvarial defects. BMP-2 alone in the range up to 1 µg per defect exhibited dose-dependent bone regeneration while relaxin alone in the range up to 0.25 µg per defect did not promote bone regeneration. When compared with BMP-2 alone (1 µg per defect), a 50% reduction in the BMP-2 dose was achieved with the addition of 0.05, 0.1, or 0.25 µg of relaxin per defect. These results show that loading HA microspheres with a combination of relaxin and BMP-2 can significantly reduce the BMP-2 dose required to regenerate an equivalent amount of bone.

Influence of Cu doping in borosilicate bioactive glass and the properties of its derived scaffolds.

Copper doped borosilicate glasses (BG-Cu) were studied by means of FT-IR, Raman, UV-vis and NMR spectroscopies to investigate the changes that appeared in the structure of borosilicate glass matrix by doping copper ions. Micro-fil and immunohistochemistry analysis were applied to study the angiogenesis of its derived scaffolds in vivo. Results indicated that the Cu ions significantly increased the B-O bond of BO4 groups at 980 cm(-1), while they decrease that of BO2O(-) groups at 1440-1470 cm(-1) as shown by Raman spectra. A negative shift was observed from (11)B and (29)Si NMR spectra. The (11)B NMR spectra exhibited a clear transformation from BO3 into BO4 groups, caused by the agglutination effect of the Cu ions and the charge balance of the agglomerate in the glass network, leading to a more stable glass network and lower ions release rate in the degradation process. Furthermore, the BG-Cu scaffolds significantly enhanced blood vessel formation in rat calvarial defects at 8 weeks post-implantation. Generally, it suggested that the introduction of Cu into borosilicate glass endowed glass and its derived scaffolds with good properties, and the cooperation of Cu with bioactive glass may pave a new way for tissue engineering.

Evaluation of borate bioactive glass scaffolds as a controlled delivery system for copper ions in stimulating osteogenesis and angiogenesis in bone healing.

Biocompatible synthetic scaffolds with enhanced osteogenic and angiogenic capacity are of great interest for the repair of large (critical size) bone defects. In this study, we investigated an approach based on the controlled delivery of copper (Cu) ions from borate bioactive glass scaffolds for stimulating angiogenesis and osteogenesis in a rodent calvarial defect model. Borate glass scaffolds (pore size = 200-400 µm) doped with varying amounts of Cu (0-3.0 wt% CuO) were created using a polymer foam replication technique. When immersed in simulated body fluid (SBF) in vitro, the scaffolds released Cu ions into the medium at a rate that was dependent on the amount of Cu in the glass and simultaneously converted to hydroxyapatite (HA). At the concentrations used, the Cu in the glass was not cytotoxic to human bone marrow derived stem cells (hBMSCs) cultured on the scaffolds and the alkaline phosphatase activity of the hBMSCs increased with increasing Cu in the glass. When implanted in rat calvarial defects for 8 weeks, the scaffolds doped with 3 wt% CuO showed a significantly better capacity to stimulate angiogenesis and regenerate bone when compared to the undoped glass scaffolds. Together, these results indicate that the controlled delivery of Cu ions from borate bioactive glass implants is a promising approach in healing bone defects.