Mechanism and strength of bonding between two bioactive ceramics in vivo.

A study was conducted to examine the mechanism and strength of bonding between two bioactive ceramic plates in vivo. Rectangular plates (15 mm X 10 mm X 2 mm) of Bioglass, apatite-wollastonite-containing glass ceramic (designated A-W.GC), and two types of hydroxyapatite sintered at 900 degrees C and 1200 degrees C (designated HA900 and HA1200) were prepared. Two plates of the same materials tied together with silk thread were implanted subcutaneously into rats. The force required to detach the mutually bonded bioactive ceramic plates was measured 4, 8, 12, and 24 weeks after implantation. The interface between the two bonded plates was examined by SEM-EPMA and thin-film x-ray diffraction analysis. At 24 weeks after implantation, the mutual bonding of Bioglass and A-W.GC was stronger than that of the two HA types. SEM-EPMA and thin-film x-ray diffraction analysis of the bonded area of Bioglass and A-W.GC plates showed bonding zones with apatite in the margins, and a bonding zone with calcite in the center. The greater strength of bonding of Bioglass and A-W.GC plates compared with the two types of HA plate 24 weeks after implantation is explained by the wider bonding zone provided by the calcite layer formed in the center of the plates, which is considered to have been perfused with PO4-poor body fluids resulting from PO4 consumption for apatite formation in the margins.     

Comparison of two carbonated apatite ceramics in vivo

Carbonated apatite ceramics, with a composition similar to that of bone mineral, are potentially interesting synthetic bone graft substitutes. In the present study, two porous carbonated apatite ceramics were developed, characterized and tested for their bone repair capacity and osteoinductive potential in a goat model. Although the two ceramics were prepared from a similar starting powder, their physico-chemical and structural characteristics differed as a consequence of different preparation methods. Both ceramics had an open and interconnected porous structure with a porosity of about 80%. The morphology of the surface of CA-A and CA-B at the submicron level differed significantly: CA-A consisted of irregular grains with a size of 5–20 μm, with 1–10 μm large micropores among the grains, whereas CA-B surface consisted of much smaller and regular shaped grains (0.05–0.5 μm), with most micropores smaller than 1 μm. The specific surface area of CA-B was about 10 times larger than that of CA-A due to its significantly smaller grain size. CA-A and CA-B ceramics contained 3 and 5 wt.% of B-type carbonated apatite, respectively. Although neither ceramic succeeded in completely bridging the 17 mm iliac wing defect with new bone after 12 weeks of implantation, CA-A showed significantly more bone formation in the pores of the implant than CA-B. The total area percentage of new bone in the total defect area was 12.7 ± 1.81 and 5.51 ± 1.37 (mean ± SEM) for CA-A and CA-B, respectively. Intramuscular implantation of the ceramics led to ectopic bone formation by CA-A in all three implanted specimens, in contrast to CA-B, where no new bone was observed in any of the 11 animals. CA-A showed a more pronounced degradation than CA-B both in vitro and in vivo at both implantation sites, which was unexpected based on the physico-chemical and structural properties of the two ceramics. Both physico-chemical and structural properties of the ceramics could, dependently or independently, have affected their in vivo behaviour, emphasizing the importance to control individual parameters for successful bone repair.     

Preparation of bioactive nanotitania ceramics with biomechanical compatibility

In this article, bioactive nanotitania ceramics with biomechanical compatibility was prepared by using an additive of hydroxyapatite or MgO as particle growth inhibitor. After sintering at 1000 degrees C, the particle size of nanotitania ceramics prepared by using HA as additive (HT) was much smaller than that prepared by using MgO as additive (MT). In simulated body fluid (SBF), HT could induce apatite formation in 4 days, while no apatite could be found on MT even after it was soaked in SBF for 14 days. After Ros17/28 osteoblasts were cultured on the materials for 1, 4, and 6 days, MTT results showed that the osteoblasts on the HT differentiated faster than that on the MT. Mechanical tests results showed that the bending and compressive strength of HT were 160 and 200 MPa, while those of MT were 70 and 88 MPa, respectively. These results demonstrated that it is suitable to prepare bioactive nanotitania ceramics, with biomechanical compatibility, by using HA as particle growth inhibitor.     

陶瓷-树脂黏结剂黏结的研究进展

全瓷修复体以多种优良的特性赢得了医师和患者的青睐,其临床应用的成败很大程度上取决于陶瓷与树脂黏结剂的黏结强度。论述了黏结的重要性并围绕陶瓷的表面处理技术及材料的性质对黏结强度的影响等问题综述了陶瓷-树脂黏结剂黏结的最新进展。     

Effects of injecting massive amounts of bioactive ceramics in mice

The effects of massive administration of bioactive ceramic powder (Bioglass (45S5), Ceravital (KGS), apatite-wollastnite containing glass ceramics (A-W GC), and hydroxyapatite (HA], by intraperitoneal (IP), intramuscular (IM), or subcutaneous (SC) injection in Balb/c mice were examined in this investigation. Alumina, Silica Glass (SG), and A-W-Al (containing the same amount of crystal as A-W GC and 6.3% Alumina) were used as nonbioactive controls. The particle size of each material injected was smaller than 44 microns. In addition to the above, two more sizes (smaller than 105 microns and smaller than 255 microns) of A-W GC powder, and a 1 x 1 x 0.2 cm plate of the A-W GC were also evaluated. When the particle size was smaller than 44 microns, intraperitoneal injections of 5 mg per g of body weight of BG, KGS, A-W GC, and A-W-Al were lethal to the mice. Ceramics in fine powder form, which are generally believed to have higher bioactivity, are associated with higher mortality except A-W-Al. On the other hand, when the particle size of the ceramic was increased, the fatal effects of ceramic powders in mice decreased. Plate form of ceramics implanted I.P. had no systemic effects. Intramuscular or SC injections of bioactive ceramic powder with a particle size smaller than 44 microns had almost no systemic effects. Both the particle size of the ceramic powder and the route of administration influenced the reactivity of the bioactive ceramics in the mice. In conclusion, regardless of particle size, neither SC nor IM injection of large doses of highly bioactive ceramics had an adverse effect on the host (mouse).     

Relationship between contrived in vivo and role-play assertive behavior

Used a 2 (High or Low Assertive) × 2 (Role-Play or Contrived In Vivo) design to investigate the external validity of role-play (N = 32). The Conflict Resolution Inventory was used as the selection device. Results indicated a positive relationship between self-report scores and role-play behavior. They also indicated that self-report scores were not predictive of behavior in the contrived in vivo condition; moreover, assertion was enhanced in the role-play condition, while the converse occurred in the contrived in vivo condition. The results indicate that generalizations to more naturalistic settings based upon role-play or self-report scores must be made with caution.     

Alkaline phosphatase grafting on bioactive glasses and glass ceramics

Bone integration of orthopaedic or dental implants and regeneration of damaged bone at the surgical site are still unresolved problems in prosthetic surgery. For this reason, biomimetic surfaces (i.e. both inorganic and biological bioactive surfaces) represent a challenge for bone implantation. In this research work a hydrolase enzyme (alkaline phosphatase) was covalently grafted to inorganic bioactive glass and glass ceramic surfaces, in order to impart biological bioactivity. The functionalized samples were analysed by means of X-ray photoelectron spectroscopy in order to verify enzyme presence on the surface. Enzyme activity was measured by means of UV–visual spectroscopy after reaction with the natural substrate. Scanning electron microscopy–energy-dispersive spectroscopy observations allowed monitoring of the morphological and chemical modification of the materials during the different steps of functionalization. In vitro inorganic bioactivity was investigated by soaking samples in simulated body fluid. Enzymatic activity of the samples was tested and compared before and after soaking. Enzymatic activity of the solution was monitored at different experimental times. This study demonstrates that alkaline phosphatase could be successfully grafted onto different bioactive surfaces while maintaining its activity. Presence of the enzyme in vitro enhances the inorganic bioactivity of the materials tested.     

Osteoblast responses to tape-cast and sintered bioactive glass ceramics

The advantage of tape-cast bioactive glasses lies in the manufacturing procedure, which allows the build-up of layers and, therefore, the production of complex shapes. This, therefore, has applications to tissue engineering, where specific shapes are required such as repair of craniofacial defects. The bioactivity of tape-cast discs sintered at temperatures ranging from 800 degrees C to 1000 degrees C and for 3 or 6 h was analyzed by FTIR. Tape-cast discs were used to culture primary human osteoblasts, and cell attachment, cell death, collagen production, nodule formation, and mineralization were studied. These responses were dependent upon Si and Na release profiles of the tape-cast discs, and development of the hydroxyapatite layer.     

In vitro and in vivo behavior of self-reinforced bioabsorbable polymer and self-reinforced bioabsorbable polymer/bioactive glass composites

The aim of this study was to investigate the in vitro and in vivo properties and degradation of (1) self-reinforced (SR) lactide copolymer, P(L/DL)LA 70:30, and (2) SR composites of the same polylactide and bioactive glass 13-93. The following three polymer and polymer-bioactive glass samples were studied: SR-PLA70, SR-PLA70 + BaG15s, and SR-PLA70 + BaG20c. In vitro behavior was studied in a phosphate-buffered saline for 87 weeks at 37 degrees +/- 1 degrees C and a pH of 7.4 +/- 0.2. In vivo behavior was studied by implanting the rods in the dorsal subcutaneous tissue of rats (SR-PLA70 + BaG20c) or rabbits (SR-PLA70 and SR-PLA70 + BaG15s) for 48 weeks. The degradation of the specimens was evaluated by measuring the changes in mechanical properties, crystallinity and molecular weight of polymer, water absorption, weight loss, and structural changes. Results showed that the addition of bioactive glass filler modified the degradation kinetics and material morphology.     

硅酸盐基-Cu/Mg生物活性陶瓷促进成骨细胞的成骨性能

文题释义：硅酸盐生物活性陶瓷：能从分子水平上激发特定的细胞响应,负载骨修复相关的活性物质、释放活性离子,或直接在材料表面与细胞发生反应,诱导、刺激新骨生成的新型可降解生物活性材料。 生物活性离子：是一类在分子水平对细胞具有特殊激发作功能的碱金属或碱土离子。研究发现,铜、镁作为人体所必需的微量元素都对成骨细胞和成血管细胞都具有明显的诱导、刺激作用。   摘要背景：硅酸盐生物陶瓷作为组织工程骨支架时促成骨能力不足。研究发现铜、镁等人体所必需微量元素对成骨细胞和成血管细胞具有明显的诱导、刺激作用。 目的：探讨掺杂铜、镁元素的多元硅酸盐生物活性陶瓷对成骨细胞增殖和成骨性能的影响。 方法：将铜、镁加入硅酸盐生物活性陶瓷中,采用溶胶-凝胶法制备掺铜硅酸盐生物陶瓷、掺镁硅酸盐生物陶瓷与掺铜镁硅酸盐生物活性陶瓷(陶瓷中铜、镁的摩尔百分比均为5%),分别记为CS-5Cu、CS-5Mg、CS-5Cu/5Mg,以硅酸盐生物活性陶瓷为对照(记为CS),利用X射线衍射、傅里叶红外光谱对样本进行表征,检测生物陶瓷表面析晶情况。将成骨细胞分别与4组陶瓷共培养24 h,分析成骨细胞的增殖指数、碱性磷酸酶分泌量、骨桥蛋白和骨钙素基因表达及黏着斑和肌动蛋白表达。结果与结论：①陶瓷矿化结晶能力大小顺序为：CS-5Cu>CS>CS-5Cu/5Mg>CS-5Mg;②成骨细胞增殖指数的大小顺序为：CS-5Cu/5Mg>CS-5Cu≈CS-5Mg>CS;③碱性磷酸酶分泌量的大小顺序为：CS-5Cu/5Mg> CS-5Cu≈CS-5Mg>CS;④骨桥蛋白和骨钙素基因表达的高低顺序为：CS-5Cu/5Mg>CS-5Cu≈CS-5Mg>CS;⑤黏着斑和肌动蛋白表达多少的顺序为：CS-5Cu/5Mg>CS-5Cu≈CS-5Mg>CS;⑥结果表明,掺铜或掺镁硅酸盐生物活性陶瓷可促进成骨细胞的增殖、成骨相关基因表达及其黏附与铺展,且同时掺入两种离子硅酸盐生物活性陶瓷的促进效果最明显。ORCID: 0000-0002-5861-6903(周航宇) 中国组织工程研究杂志出版内容重点：生物材料;骨生物材料; 口腔生物材料; 纳米材料; 缓释材料; 材料相容性;组织工程     

Enhanced osteoporotic bone regeneration by strontium-substituted calcium silicate bioactive ceramics

The regeneration capacity of the osteoporotic bones is generally lower than that of the normal bones. Current methods of bone defect treatment for osteoporosis are not always satisfactory. Recent studies have shown that the silicate based biomaterials can stimulate osteogenesis and angiogenesis due to the silicon (Si) ions released from the materials, and enhance bone regeneration in vivo. Other studies showed that strontium (Sr) plays a distinct role on inhibiting bone resorption. Based on the hypothesis that the combination of Si and Sr may have synergetic effects on osteoporotic bone regeneration, the porous Sr-substituted calcium silicate (SrCS) ceramic scaffolds combining the functions of Sr and Si elements were developed with the goals to promote osteoporotic bone defect repair. The effects of the ionic extract from SrCS on osteogenic differentiation of bone marrow mesenchymal stem cells derived from ovariectomized rats (rBMSCs-OVX), angiogenic differentiation of human umbilical vein endothelial cells (HUVECs) were investigated. The in vitro results showed that Sr and Si ions released from SrCS enhanced cell viability, alkaline phosphatase (ALP) activity, and mRNA expression levels of osteoblast-related genes of rBMSCs-OVX and expression of vascular endothelial growth factor (VEGF) without addition of extra osteogenic and angiogenic reagents. The activation in extracellular signal-related kinases (ERK) and p38 signaling pathways were observed in rBMSCs-OVX cultured in the extract of SrCS, and these effects could be blocked by ERK inhibitor PD98059, and P38 inhibitor SB203580, respectively. Furthermore, the ionic extract of SrCS stimulated HUVECs proliferation, differentiation and angiogenesis process. The in vivo experiments revealed that SrCS dramatically stimulated bone regeneration and angiogenesis in a critical sized OVX calvarial defect model, and the enhanced bone regeneration might be attributed to the modulation of osteogenic differentiation of endogenous mesenchymal stem cells (MSCs) and the inhibition of osteoclastogenesis, accompanying with the promotion of the angiogenic activity of endothelial cells (ECs).     

Competition between two virulent Marek's disease virus strains in vivo

Previous studies have demonstrated the presence of multiple strains of Marek's disease virus simultaneously circulating within poultry flocks, leading to the assumption that individual birds are repeatedly exposed to a variety of virus strains in their lifetime. Virus competition within individual birds may be an important factor that influences the outcome of co-infection under field conditions, including the potential outcome of emergence or evolution of more virulent strains. A series of experiments was designed to evaluate virus competition within chickens following simultaneous challenge with two virulent serotype 1 Marek's disease virus strains, using either pathogenically similar (rMd5 and rMd5/pp38CVI) or dissimilar (JM/102W and rMd5/pp38CVI) virus pairs. Bursa of Fabricius, feather follicle epithelium, spleen, and tumour samples were collected at multiple time points to determine the frequency and distribution of each virus present using pyrosequencing, immunohistochemistry and virus isolation. In the similar pair, rMd5 appeared to have a competitive advantage over rMd5/pp38CVI, which in turn had a competitive advantage over the less virulent JM/102W in the dissimilar virus pair. Dominance of one strain over the other was not absolute for either virus pair, as the subordinate virus was rarely eliminated. Interestingly, competition between two viruses with either pair rarely ended in a draw. Further work is needed to identify factors that influence virus-specific dominance to better understand what characteristics favour emergence of one strain in chicken populations at the expense of other strains.     

Protein adsorption onto two bioactive glass-ceramics

Recent research suggests that the biocompatibility of an implant is to a large extent determined by selective adsorption of proteins from surrounding body fluids. Protein adsorption from human plasma onto two bioactive glass-ceramics (RKKP and AP40) which differ in La and Ta content, was studied by means of chromatography and two-dimensional polyacrylamide gel electrophoresis (2D-PAGE). The quantitative analysis showed that the glass-ceramics have good protein binding capacities indicating multilayer formation. A correlation between chemical composition and the amount of adsorbed proteins was observed. The presence of La and Ta decreased the protein adsorption, so AP40 bound significantly more protein per surface unit then did RKKP. Preferential adsorption of apolipoprotein J, fibrinogen and fibronectin was observed.     

In vivo comparison of bioactive glass particles in rabbits

Bioglass particles of the compositions 45s5, 52s and 55s were implanted in the distal femoral epiphysis of rabbits. Animals were sacrificed at 7, 28, and 84 d postoperatively and specimens investigated using light microscopy and histomorphometry. Bone bonding occurred in a zentripetal fashion and fastest for 45s5. Bone formation was hampered at the core of the implantation bed where bone bonding showed a peak at 28d and diminished at 84d (except for 55s). This went along with a significant increase in numerous multinuclear giant cells (MNGC). Implantation model, particle size and surface-area-to-volume ratio are discussed as possible parameters determining bone regeneration.     

Dose-dependent behavior of bioactive glass dissolution.

The effect of glass dosage (0.001 g ml(-1) to 0.015 g ml(-1)) on the in vitro dynamic dissolution behavior of melt-derived 45S5 and sol-gel-derived 58S bioactive glasses, in simulated body fluid (SBF) at 37 degrees C, was evaluated. These glasses differ significantly in texture, especially the specific surface area and porosity, as a result of differences in manufacturing route. The concentrations of elements (Si, Ca, P, and Na) leached from the glasses into the dissolution medium, from 1 to 22 h, were evaluated with the use of induced coupled plasma analysis (ICP). The reacted powders were analyzed with the use of FTIR to observe the formation of a hydroxycarbonate apatite layer on the surface. The results show that the rate of HCA formation on both gel- and melt-derived bioactive glass powders in vitro depends on the concentration of the powders in solution. This result must be taken into account when carrying out in vitro cell-culture studies to simulate conditions in vivo and in experiments using extracts of the bioactive glass powders.     

New biomorphic SiC ceramics coated with bioactive glass for biomedical applications

A new generation of light, tough and high-strength material for medical implants for bone substitutions with a good biological response is presented. The innovative product that fulfills all these requirements is based on biomorphic silicon carbide ceramics coated with a bioactive glass layer. The combination of the excellent mechanical properties and low density of the biomorphic SiC ceramics, used as a base material for implants, with the osteoconducting properties of the bioactive glass materials opens new possibilities for the development of alternative dental and orthopedic implants with enhanced mechanical and biochemical properties that ensures optimum fixation to living tissue. Biomorphic SiC is fabricated by molten-Si infiltration of carbon templates obtained by controlled pyrolysis of wood. Through this process, the microstructure of the final SiC product mimics that of the starting wood, which has been perfected by natural evolution. The basic features of such microstructure are its porosity (ranging from 30% to 70%) and its anisotropy, which resembles the cellular microstructure and the mechanical characteristics of the bone. The SiC ceramics have been successfully coated with a uniform and adherent bioactive glass film by pulsed laser ablation using an excimer ArF laser. The excellent coverage of the SiC rough surface without film spallation or detachment is demonstrated. In order to assess the coating bioactivity, in vitro tests by soaking the samples in simulated body fluid have been carried out. After 72 h, the formation of a dense apatite layer has been observed even in interconnecting pores by SEM and energy dispersive X-ray spectroscopy analysis demonstrating the bioactive response of this product.     

Mechanism of bone-like formation on a bioactive implant in vivo

The physical and chemical nature of the remodelled interface between the porous A3 glass-ceramic, composed of (wt%): SiO(2) = 54.5; CaO = 15.0; Na(2)O = 12.0; MgO = 8.5; P(2)O(5) = 6.0 K(2)O = 4.0, and the surrounding bone was studied after implantation into rat tibias. The interfaces which developed new bone layer in direct contact with the implants were examined by analytical scanning and transmission electron microscopy after implantation for 6, 8 and 12 weeks. Degradation processes of the implants also encouraged osseous tissue ingrowths into the pores of the material, changing drastically the macro- and microstructure of the implants. The ionic exchange initiated at the implant interface with the physiological environment was essential in the integration process of the implant, through a dissolution-precipitation-transformation mechanism. The interfaces developed non-toxic biological and chemical activities and remained reactive over the 12-week implantation period. These findings were significant as indicative of morphological and chemical integration of the A3 glass-ceramic into the structure of living bone tissue. A3 glass-ceramic could be suitable for the repair or replacement of living bone.     

生物活性陶瓷涂层假体植入股骨初期的界面生物力学分析

目的对具有生物活性的羟基磷灰石陶瓷涂层假体植入股骨初期进行界面生物力学分析,以优化金属表面生物活性陶瓷涂层厚度。方法建立生物活性陶瓷涂层假体紧压配合植入股骨初期的生物力学模型,应用非均质层状材料弹性力学理论,定量计算不同厚度涂层钛合金假体与股骨峡部界面的紧压配合力及环向应力。结果无涂层钛合金假体与骨结合的紧压配合力最大,随着涂层厚度增加,紧压配合力逐渐减小。环向应力在界面的骨皮质上有较大的拉应力,在涂层和钛合金假体柄上为压应力。结论生物活性陶瓷涂层较薄的假体与股骨结合的抗剪切强度较大。     

Reconstruction of calvarial defect of rabbits using porous calcium silicate bioactive ceramics

In this study, the in vivo bone-regenerative capacity and resorption of the porous beta-calcium silicate (beta-CaSiO(3), beta-CS) bioactive ceramics were investigated in a rabbit calvarial defect model, and the results were compared with porous beta-tricalcium phosphate (beta-Ca(3)(PO(4))(2), beta-TCP) bioceramics. The porous beta-CS and beta-TCP ceramics were implanted in rabbit calvarial defects and the specimens were harvested after 4, 8 and 16 weeks, and evaluated by Micro-CT and histomorphometric analysis. The Micro-CT and histomorphometric analysis showed that the resorption of beta-CS was much higher than that of beta-TCP. The TRAP-positive multinucleated cells were observed on the surface of beta-CS, suggesting a cell-mediated process involved in the degradation of beta-CS in vivo. The amount of newly formed bone was also measured and more bone formation was observed with beta-CS as compared with beta-TCP (p<0.05). Histological observation demonstrated that newly formed bone tissue grew into the porous beta-CS, and a bone-like apatite layer was identified between the bone tissue and beta-CS materials. The present studies showed that the porous beta-CS ceramics could stimulate bone regeneration and may be used as bioactive and biodegradable materials for hard tissue repair and tissue engineering applications.