Competent F18 bioglass-Biosilicate® bone graft scaffold substitutes

Biosilicate® glass-ceramic (BioS) offers an attractive choice for the manufacturing of scaffolds because of their high bioactivity, non-toxicity, bactericidal activity and biodegradability. Despite these positive properties, Biosilicate® scaffolds that have been developed so far show low fracture strength, limiting their clinical application. For this reason, our aim was to increase their strength through vacuum infiltration of F18 bioactive glass. First, we calculated the maximum attainable theoretical compressive strength of a scaffold using the Ryshkewitch and Ashby-Gibson models. We show that for a total porosity of 80 %, σ₀ = 250 MPa, and n = 5 the compressive strength estimated by both models is approximately 4.5 MPa. Afterward, the Biosilicate scaffolds were prepared using the foam replica technique and recoated several times with a F18 glass slurry to eliminate surface defects. Scanning Electron Microscopy examination showed that the F18 indeed helped to remove surface defects and partially infiltrated the hollow struts, significantly increasing their mechanical integrity. The F18-BioS scaffolds exhibited a total porosity of 82 %, an average cell size of 525 μm, and compressive strength of 3.3 ± 0.3 MPa, which is close to the predicted value and significantly higher than those of sole BioS scaffolds of a similar structure (< 0.1 MPa). These values are within the range of commercial scaffolds based on Hydroxyapatite (HA) and β-tricalcium phosphate (β-TCP), having a considerable advantage of being more osteoinductive, angiogenic, and highly bactericidal. The F18-BioS scaffolds developed in this work thus have high potential for odontology or craniofacial surgeries that do not involve high load–bearing conditions.     

Cryo-X-ray analysis-A novel tool to better understand the physicochemical reactions at the bioglass/biological fluid interface

The present study deals with the short-term physicochemical reactions at the interface between bioactive glass particles [55SiO(2)-20CaO-9P(2)O(5)-12Na(2)O-4MgO. mol%] and biological fluid (Dulbecco Modified Eagle's Medium (DMEM)). The physicochemical reactions within the interface are characterized by scanning transmission electron microscopy (TEM) (STEM) associated with Energy-dispersive X-ray spectroscopy (EDXS). Microanalysis of diffusible ions such as sodium, potassium, or oxygen requires a special care. In the present investigation the cryo-technique was adopted as a suitable tool for the specimen preparation and characterization. Cryosectioning is essential for preserving the native distribution of ions so that meaningful information about the local concentrations can be obtained by elemental microanalysis. The bioglass particles immersed in biological fluid for 24 h revealed five reaction stages: (i) dealkalization of the surface by cationic exchange (Na(+), Ca(2+) with H(+) or H(3)O(+)); (ii) loss of soluble silica in the form of Si(OH)(4) to the solution resulting from the breakdown of Si--O--Si bonds (iii); repolymerization of Si(OH)(4) leading to condensation of SiO(2)); (iv) migration of Ca(2+) and PO(4) (3-) to the surface through the SiO(2)-rich layer to form CaO-P(2)O(5) film; (v) crystallization of the amorphous CaO-P(2)O(5) by incorporating OH-- or CO(3) (2-) anions with the formation of three different surface layers on the bioactive glass periphery. The thickness of each layer is approximately 300 nm and from the inner part to the periphery they consist of Si--OH, which permits the diffusion of Ca(2+) and PO(4) (3-) ions and the formation of the middle Ca--P layer, and finally the outer layer composed of Na--O, which acts as an ion exchange layer between Na(+) ions and H(+) or H(3)O(+) from the solution.     

Processing of ZrO2 scaffolds coated by glass–ceramic derived from 45S5 bioglass

Three dimensional, highly porous, ZrO₂ scaffolds coated by glass–ceramic derived from 45S5 bioglass were fabricated. The surface reactivity of 45S5 in aqueous solution was investigated as a function of the immersion time. The influence of the solid loading on the rheological behavior of 45S5 aqueous slips with ammonium polyacrylate (NH₄PA) was studied; besides the effect of poly(vinyl)alcohol (PVA) on the relative viscosity was determined. The structure and microstructure of uncoated and coated ZrO₂ scaffolds were characterized. The high ionic exchange capability of 45S5 was demonstrated by the pH rise, the significant weight loss and the amorphous calcium phosphate nucleation, upon its immersion in aqueous solution. The addition of PVA did not affect the dispersion properties of the 45S5 powder, which were basically controlled by its negative surface charge. 30 wt% 45S5 slips with 4 wt% PVA exhibited a yield stress and an adequate viscosity in the low shear rate range, to produce a bioglass coating into the ZrO₂ scaffold. The glass-ceramic coating was distributed along the strut surfaces, forming a thin film without altering the porosity and the strut thickness of the original ZrO₂ scaffold structure.     

熔融法生物玻璃与溶胶-凝胶法生物玻璃的矿化特性研究

采用X射线衍射(XRD)、傅立叶转换红外光谱(FTIR)、扫描电镜(SEM)等方法对比分析了熔融法生物玻璃45S5与溶胶-凝胶法生物玻璃58S及77S的体外生物矿化性能,对它们表现出来的生物矿化性能差异进行初步的机理研究.结果表明,这3种生物玻璃中,58S具有最好的生物矿化性能,在37℃的模拟体液(simulated body fluid,SBF)中浸泡反应8 h即能在表面矿化形成结晶度较好的碳酸羟基磷灰石(HCA).     

仿生型壳聚糖-明胶/溶胶凝胶生物玻璃复合支架的制备及其矿化性能研究

利用冷冻干燥法制备出用于骨和软骨组织工程的壳聚糖-明胶/溶胶凝胶生物玻璃(CS-Gel/SGBG)仿生型复合多孔支架,并进行了孔隙率的测定和显微形貌的观察;探讨了各组分不同用量对CS-Gel/SGBG复合支架显微结构的影响以及复合支架在模拟生理体液中的仿生矿化性能。研究表明,通过调节各组分的不同用量,可以制备出三维连通的复合多孔支架,且孔隙率达到90%以上;在模拟生理体液中浸泡后发现CS-Gel/SGBG支架表面有大量结晶态类骨碳酸羟基磷灰石生成,表明复合支架有良好的生物矿化性能。     

A hundred times faster: Novel,rapid sol-gel synthesis of bio-glass nanopowders (Si-Na-Ca-P system,Ca:P = 1.67) without aging

Synthesis of sol-gel glass with incorporation of Na₂O is extremely difficult, as such glasses have a great tendency to crystallize. Slow drying and aging over several days or weeks is usually required in sol-gel preparation procedures. This work reports a fast, novel route for the synthesis of bioglass powders in a considerably shortened period of 1 h. A comparative study of sol-gel derived glasses made by this novel route using rotary evaporator drying, and a conventional route using oven drying and aging, revealed that the two methods produce stabilized (devitrified) bio-glasses with virtually identical behavior and properties. Indeed, the rapidly dried powder exhibited slightly enhanced properties that should result in improved bioactivity. Fourier-transform infrared spectroscopy was used to understand the structures of the synthesized powders, and MAS-NMR was used to look at the degree of polymerization. This innovative, rapid route was successfully demonstrated to produce glass and devitrified glass nanopowders more than one hundred times quicker than the quickest reported standard drying methods.     

A Bioglass-Based Antibiotic (Vancomycin) Releasing Bone Void Filling Putty to Treat Osteomyelitis and Aid Bone Healing

While the infection rate after primary total joint replacements (TJR) sits at 1–2%, for trauma-related surgery, it can be as high as 3.6 to 21.2% based on the type of trauma; the risk of reinfection after revision surgery is even higher. Current treatments with antibiotic-releasing PMMA-based bone cement/ beads and/or systemic antibiotic after surgical debridement do not provide effective treatment due to fluctuating antibiotic levels at the site of infection, leading to insufficient local antibiotic concentration. In addition, non-biodegradable PMMA does not support bone regrowth in the debrided void spaces and often must be removed in an additional surgery. Here, we report a bioactive glass or bioglass (BG) substrate-based biodegradable, easy to fabricate “press fitting” antibiotic-releasing bone void filling (ABVF-BG) putty to provide effective local antibiotic release at the site of infection along with support for bone regeneration. The ABVF-BG putty formulation had homogenously distributed BG particles, a porous structure, and showed putty-like ease of handling. Furthermore, the ABVF-BG putty demonstrated in vitro antibacterial activity for up to 6 weeks. Finally, the ABVF-BG putty was biodegradable in vivo and showed 100% bacterial eradication (as shown by bacterial cell counts) in the treatment group, which received ABVF-BG putty, compared to the infection control group, where all the rats had a high bacterial load (4.63 × 10⁶ ± 7.9 × 10⁵ CFU/gram bone) and sustained osteomyelitis. The ABVF-BG putty also supported bone growth in the void space as indicated by a combination of histology, µCT, and X-ray imaging. The potential for simultaneous infection treatment and bone healing using the developed BG-based ABVF-BG putty is promising as an alternative treatment option for osteomyelitis.     

组织工程用β-磷酸三钙生物活性支架材料的显微结构及性能

以萘粉作造孔剂,聚乙烯醇作粘结剂,以β-磷酸三钙、生物活性玻璃等材料研制生物活性组织工程支架用复合材料。用XRD,SEM等研究手段,对多孔陶瓷的性能、微观结构、及其制造工艺对材料性能影响规律进行了研究。结果表明：所制备支架材料孔隙率达75％,抗弯强度可达4．4MPa,孔径为200～400μm。实验还表明：随烧结温度升高,孔隙率随之降低,抗弯强度提高。     

BG/PHBV复合多孔组织工程支架材料的动物植入实验观察

本文研究了溶胶-凝胶生物玻璃／聚羟基烷酸脂(BG／PHBV)复合多孔支架材料与成骨细胞的生物相容性,并对植入动物体内的BG／PHBV和羟基磷灰石／聚羟基烷酸脂(HA／PHBV)两种材料的成骨情况进行了SEM跟踪测试。结果表明：在动物实验中,与HA／PHBV复合多孔支架材料相对照,BG／PHBV植入后,新生骨形成时间早,骨修复完成时间早,降解速度快。