Antibacterial activity of nanostructured Ti-45S5 bioglass-Ag composite against Streptococcus mutans and Staphylococcus aureus

Mechanical alloying and annealing at 1150 °C for 2 h under an argon atmosphere were used to prepare Ti-45S5 bioglass nanocomposites. Ti-45S5 bioglass material was chemically modified by silver. The antibacterial activity of Ti-10% 45S5 bioglass nanocomposite containing silver against Streptococcus mutans and Staphylococcus aureus was studied. Nanocomposites were characterized by X-ray diffraction, scanning electron microscopy equipped with an electron energy dispersive spectrometer and transmission electron microscopy to evaluate phase composition, crystal structure and grain size. In vitro bacterial adhesion study indicated a significantly reduced number of Streptococcus mutans and Staphylococcus aureus on the bulk nanostructured Ti-45S5 bioglass-Ag plate surface in comparison to that on microcrystalline Ti plate surface. Nanostructured Ti-based biomaterials can be considered to be the future generation of dental implants.

Synthesis and Properties of Ag-doped Titanium-10 wt% 45S5 Bioglass Nanostructured Scaffolds

A new kind of biomedical Ti-45S5 Bioglass-Ag nanocomposites and their scaffolds with antibacterial function was developed by the introduction of 1.5 wt% Ag into the Ti-10 wt% 45S5 Bioglass matrix. The microstructure, hardness and corrosion resistance in Ringer solution of the Ag-doped Ti-45S5 glass were investigated. The Vickers hardness of the bulk Ti-10 wt% 45S5 Bioglass-1.5 wt% Ag nanocomposites reached 480 HVo.3. Contact angles of water on the micro- crystalline Ti and nanostructured Ti-10 wt% 45S5 Bioglass-1.5 wt% Ag sample were determined and show visible decrease from 55.2° to 49.6°. In vitro tests culture of normal human osteoblast cells showed very good cells proliferation, colonization and multilayering. In vitro bacterial adhesion study indicated a significantly reduced number of bacteria （Staphylococcus aureus） on the bulk nanostructured Ti-10 wt% 45S5 Bioglass-1.5 wt% Ag plate surface in comparison with that on microcrystalline Ti plate surface. Development of porous Ti-10 wt% 45S5 Bioglass-1.5 wt% Ag scaffolds aims in enhancing bone ingrowth and prosthesis fixation.

溶胶-凝胶低熔点硼硅酸盐生物活性玻璃增强高温熔融45S5生物玻璃多孔材料

本文研究了硼掺杂58S生物玻璃（58S-B）低温助烧结45S5生物玻璃块体材料。实验将45S5超细颗粒加入到制备58S—B的溶胶中，按常规溶胶一凝胶制备粉体的步骤制备出45S5／58S—B复合粉体，并同步制备58S—B粉体，然后再考察不同烧结温度对复合粉体制备块体材料的烧结性能和力学强度的影响规律，并运用TRIS缓冲溶液浸泡实验分析块体材料的降解性。结果显示，45S5与58S—B两相颗粒混合均匀，850℃烧结后的低、高孔隙率45S5／58S—B块体材料的抗压强度（40．2MPa；8．3MPa）均显著优于相同温度处理后的低、高孔隙率纯45S5玻璃陶瓷（14．9MPa；2．8MPa）；同时，较低的烧结温度（850-900℃）极为有利于45S5／58S—B多孔材料在TRIS缓冲液浸泡中沉积类骨羟基磷灰石（HA）和生物活性离子释放。以上研究结果解决了长期以来困扰45S5生物玻璃低温烧结性能差、极为易脆等关键问题，为45S5等熔融法制备的生物活性玻璃多子L块体材料在临床齿骨及骨损伤修复和骨组织工程中的应用提供了新的技术方案。

Chronology of Bioactive Glass Development and Clinical Applications

The key research and development steps for bioactive glass (45S5 Bioglass) are documented from the date of discovery in 1969 through FDA approvals of the first dental, ENT, maxillo-facial and orthopedic clinical products. Understanding the mechanisms and quantifying the rapid surface reactions to form a bone-bonding hydroxyl-carbonate apatite (HCA) layer on the bioactive glass in contact with living bone was a vital part of the early development of this class of biomaterials. A key later discovery was enhanced osteogenesis and in situ bone regeneration by controlled release of ionic dissolution products from the bioactive glass particulates that leads to up-regulation and activation of seven families of genes, a process called osteostimulation.

Superior biocompatibility and comparable osteoinductive properties: Sodium-reduced fluoride-containing bioactive glass belonging to the CaO–MgO–SiO2 system as a promising alternative to 45S5 bioactive glass

Bioactive glasses(BGs)are promising bone substitute materials.However,under certain circumstances BGs such as the well-known 45S5 Bioglass®(composition in wt%:45.0 SiO2,24.5 Na2O,24.5 CaO,6.0 P2O5)act cytotoxic due to a strong increase in pH caused by a burst release of sodium ions.A potential alternative is a sodiumreduced fluoride-containing BG belonging to the CaO–MgO–SiO2 system,namely BG1d-BG(composition in wt%:46.1 SiO2,28.7 CaO,8.8 MgO,6.2 P2O5,5.7 CaF2,4.5 Na2O),that has already been evaluated in-vitro,in-vivo and in preliminary clinical trials.Before further application,however,BG1d-BG should be compared to the benchmark amongst BGs,the 45S5 Bioglass®composition,to classify its effect on cell viability,proliferation and osteogenic differentiation of human mesenchymal stem cells(MSCs).Therefore,in this study,the biocompatibility and osteogenic potential of both BGs were investigated in an indirect and direct culture setting to assess the effect of the ionic dissolution products and the BGs’physical presence on the cells.The results indicated an advantage of BG1d-BG over 45S5 Bioglass®regarding cell viability and proliferation.Both BGs induced an earlier onset of osteogenic differentiation and accelerated the expression of late osteoblast marker genes compared to the control group.In conclusion,BG1d-BG is an attractive candidate for further experimental investigation.The basic mechanisms behind the different impact on cell behavior should be assessed in further detail,e.g.by further alteration of the BG compositions.

Strengthening mechanisms in carbon nanotube reinforced bioglass composites

Carbon nanotube reinforced bioglass composites have been successfully synthesized by two comparative sintering techniques, i.e., spark plasma sintering （SPS） and conventional compaction and sinteirng. The composites show improved mechanical properties, with SPS technique substantially better than conventional compact and sintering approach. Using SPS, compared with the 45S5Bioglass matrix, the maximum flexural strength and fracture toughness increased by 159% and 105%, respectively. Enhanced strength and toughness are attributed to the interfacial bonding and bridging effects between the carbon nanotubes and bioglass powders during crack propagations.