One-step synthesis and luminescence properties of tetragonal double tungstates nanocrystals.

A versatile one-step thermolysis protocol is demonstrated to produce a uniform dispersion of tetragonal double tungstates NaRE(WO4)2 (RE = rare earth) nanocrystals (NCs). Oriented attachment in the [001] direction occurred. Doping with luminescent RE(3+) ions resulted in highly luminescent NCs showing characteristic line emission of the dopant as well as a blue emission assigned to surface adsorbed organic species.

A microstructural examination of apatite induced by Bioglass in vitro.

Bioglass, a clinically used bone graft material, has been tested in vitro in a simulated body fluid (SBF) up to four weeks. Apatite crystals were not only found to form on its surface but also in the reaction solutions. The apatite crystals have been examined by high-resolution transmission electron microscopy (TEM). The crystals formed in the solutions appear identical in morphology and structure with those formed on the Bioglass surface. It may be that the soluble Si in the solution serves as the nucleating site for the apatite crystal or that apatite nuclei are released from the Bioglass surface to the solution resulting in crystal growth.

Long-term in vivo bioactivity and degradability of bulk sol-gel bioactive glasses.

Melt-derived bioactive glasses have been used with success in various clinical applications for over 10 years. Recently, particles of sol-gel-derived bioactive glasses with an initial high specific surface area have been shown to exhibit excellent osteoconductive properties as well as significant degradability. In this work, we explored the long-term in vivo bioactivity and degradability of bulk sol-gel-derived glasses in a rabbit model. Two sol-gel compositions (58S and 77S Bioglass) were used. Bulk 45S5 Bioglass was used as a control. Both sol-gel-derived glasses demonstrated osteoconductive properties similar to 45S5 Bioglass. In addition, absorbability was observed for both sol-gel-derived glasses starting after 12 weeks of implantation. Total absorption reached 40% after 52 weeks. No degradation could be measured in the case of bulk 45S5 melt-derived Bioglass within 1 year of implantation. The degradation process was highly time dependent, as demonstrated by regression analysis. New bone formation was found to fill in areas that had been resorbed, similar to bone remodeling. This absorbability can be assumed to be at least partially related to an osteoclastic resorption as viable osteoclasts-like cells were found to be in direct contact with the glass surfaces.

Effects of amelogenin on the transforming surface microstructures of Bioglass in a calcifying solution.

Topographies of a bioactive glass (45S5 type Bioglass(R)) during 0-4 h of immersion in a supersaturated calcifying solution (SCS) and the SCS containing recombinant porcine amelogenin rP172 (SCS(rP172)) were observed by atomic force microscopy. Other techniques including X-ray diffraction, scanning electron microscopy coupled with energy dispersive X-ray spectroscopy, and transmission electron microscopy were used for some complementary microstructural investigations. The smooth Bioglass surface changed to be very rough after 0.5 h of SCS immersion because of glass network dissolution. Spherical silica-gel particles with diameters of 150-300 nm consisting of substructures of 20-60 nm across had formed on the sample surfaces after 1 h of SCS immersion. The chemisorption of amorphous calcium phosphate and crystallization of nanophase apatite were seen to occur epitaxially on the silica-gel structures during 1-4 h of SCS immersion. During the first 0.5 h of SCS(rP172) immersion, more than 95% of rP172 protein in solution was adsorbed onto the sample surfaces and generated spherical assemblies of 10-60 nm diameters. During 0.5-4 h of SCS(rP172) immersion, the protein assemblies of rP172 remarkably induced the formation of orientated silica-gel plates (approximately 100-nm wide and 50-nm thick) and subsequently of long and thin apatite needle crystals. The recombinant amelogenin rP172-modulated apatite crystals resembled those formed in the early stage of tooth enamel biomineralization, suggesting the functional roles of amelogenins during the oriented growth of enamel crystallites and a great potential for amelogenins in applications designed to fabricate enamel-like calcium phosphate biomaterials.

Bioactivity of sol-gel bioactive glass coated alumina implants.

Alumina on alumina total hip arthroplasty has been in use for more than 25 years with encouraging results. However, an improvement of the alumina/bone interface still is required. The objective of this study was to investigate the in vitro and in vivo osteoconductive properties of sol-gel bioactive glass coated alumina implants. Two sol-gel glass compositions (58S Bioglass(R) and 77S Bioglass(R)) were used as coatings on alumina substrates and implanted in a rabbit model. The 58S sol-gel coating was employed in two configurations, single (A58S1) and double layer (A58S2). SEM analysis after one week in simulated body fluid revealed small crystals assumed to represent the initial phase of hydroxyapatite formation, whereas no clear conclusion could be drawn from Fourier transform infrared spectroscopy data. The percentage of bone in direct contact was greater for coated implants when compared to bulk alumina implants (p <0.001). In the case of A58S1 implants, bone percentage significantly increased from 45.1% after 3 weeks up to 87. 8% after 24 weeks of implantation (p = 0.0004). The presence of osteoid tissue, related to an aluminum release from the alumina substrates, was greatly diminished when compared to melt-derived glass-coated alumina implants.

[The effect of trilostane and dexamethasone on serum amino acids and TNF in endotoxemic rats].

By the use of specific endogenous GC biosynthesis inhibitor Trilostane and exogenous GC Dexamethasone (Dex), we established three rat models with similar severity of endotoxemia, but different plasma GC level. With these models we studied the effect of elevated plasma GC on serum TNF, pathological changes of vital organs and the changes in serum amino acids and glucose concentration in comparable endotoxemic condition. It was observed that plasma GC level was negatively correlated with the maximum TNF concentration, but positively correlated with the liver tyrosine transaminase activity, serum amino acids and glucose concentrations and as the serum GC level was elevated, the pathological changes of intestine, stomach, liver and lungs became less pronounced. From these results, it was supposed that in severe endotoxemia hypersecration of endogenous GC and maintenance of high level plasma GC are essential for animals to alleviate tissue injuries by reducing the overproduction of the host-derived mediators such as TNF and promoting the metabolism of amino acids and glucose.

[Influence of vehicles on human skin permeation of norgestrel and levonorgestrel in vitro].

In the experiment Valia-Chien skin permeation cell and methods were constructed for investigating the influence of various vehicles on the transdermal absorption of norgestrel (NG) and levonorgestrel (LNG). All of the vehicles were saturated with NG or LNG at 37 degrees C, so variations in permeation were mainly attributable to the vehicle effects. The results showed that the transdermal fluxes of NG and LNG were increased about 5-6 fold using an optimal concentration range of aqueous ethanol as a vehicle relative to that when normal saline was used as a vehicle. The NG permeation rate was about 1-2 fold greater than that of LNG in the above--mentioned saline aqueous ethanol and neat ethanol. Oleic acid (OA) and aqueous ethanol both enhanced synergistically the permeation of LNG through the human cadaver skin. When OA--80% ethanol (0.75:9.25 v/v) was used as a co--vehicle, the flux of LNG was 0.53 micrograms/cm2.h, which was 3 fold and 29 fold respectively greater than that when 80% ethanol and neat OA were used as the vehicle.