In vitro bioactivity, cytocompatibility, and antibiotic release profile of gentamicin sulfate-loaded borate bioactive glass/chitosan composites

Borate bioactive glass-based composites have been attracting interest recently as an osteoconductive carrier material for local antibiotic delivery. In the present study, composites composed of borate bioactive glass particles bonded with a chitosan matrix were prepared and evaluated in vitro as a carrier for gentamicin sulfate. The bioactivity, degradation, drug release profile, and compressive strength of the composite carrier system were studied as a function of immersion time in phosphate-buffered saline at 37 °C. The cytocompatibility of the gentamicin sulfate-loaded composite carrier was evaluated using assays of cell proliferation and alkaline phosphatase activity of osteogenic MC3T3-E1 cells. Sustained release of gentamicin sulfate occurred over ~28 days in PBS, while the bioactive glass converted continuously to hydroxyapatite. The compressive strength of the composite loaded with gentamicin sulfate decreased from the as-fabricated value of 24 ± 3 MPa to ~8 MPa after immersion for 14 days in PBS. Extracts of the soluble ionic products of the borate glass/chitosan composites enhanced the proliferation and alkaline phosphatase activity of MC3T3-E1 cells. These results indicate that the gentamicin sulfate-loaded composite composed of chitosan-bonded borate bioactive glass particles could be useful clinically as an osteoconductive carrier material for treating bone infection.     

Sol-gel生物活性玻璃体外矿化沉积的动态/静态体外模拟系统对比研究

采用溶胶-凝胶法制备了CaO-P2O3-SiO2系统生物活性玻璃粉体,并通过成型烧结工艺制成多孔材料,对比研究了样品在动态和静态2种体外模拟实验系统中的材料矿化沉积,通过测量溶液pH值,Ca^2 浓度,及样品的XRD、SEM、FTIR测试,证明了动态体外模拟系统可以更好地模拟体内环境,生物活性玻璃材料在2种模拟系统中表面都有碳酸羟基磷灰石生成。     

玻璃基多孔骨水泥的制备和性能研究

将SiO2-CaO-P2O5系统生物活性玻璃粉末、甘露醇和磷酸铵调和液均匀混合制得多孔玻璃基骨水泥.利用XRD、FTIR和SEM对骨水泥的晶相和显微结构进行了观察和分析,并对其显气孔率和力学强度进行了测试.实验结果表明,随着浸泡时间的增加,骨水泥固化体中生成了HAP晶体,HAP晶体呈短柱状,交织分布于玻璃颗粒间隙,尺寸大约为200nm;甘露醇晶体能在生理模拟液的浸泡下降解,降解后留下的孔隙显著增加了骨水泥的显气孔率,并且随着甘露醇含量的增加而增加,而体积密度和力学强度则呈下降的趋势.     

Local drug delivery system for the treatment of osteomyelitis: In vitro evaluation

Local antimicrobial delivery is a potential area of research conceptualized to provide alternative and better methods of treatment for cases, as osteomyelitis where avascular zones prevent the delivery of drugs from conventional routes of administration. Drug-loaded polymers and calcium phosphates as hydroxyapatites have been tried earlier. Bioactive glasses are bone-filling materials used for space management in orthopedic and dental surgery. A new bioactive glass (SSS2) was synthesized and fabricated into porous scaffold with a view to provide prolonged local delivery of gatifloxacin and fluconazole as suitable for the treatment of osteomyelitis. The new SSS2 was characterized by Fourier transform infrared (FTIR) and X-ray diffraction (XRD) analyses. In addition, the bioactivity of the SSS2 glass and resulting scaffold was examined by in vitro acellular method and ascertained by FTIR and XRD. The pore size distribution was analysed by mercury intrusion porosimetry and the release of drugs from scaffolds were studied in vitro. The glass and the resulting scaffolds were bioactive indicating that they can bond with bone in vivo. The scaffolds were porous with pores predominantly in the range of 10-60 μm, released the drugs effectively for 6 weeks and deemed suitable for local delivery of drugs to treat osteomyelitis.     

Bioactive borate glass scaffolds: in vitro and in vivo evaluation for use as a drug delivery system in the treatment of bone infection

The objective of this work was to evaluate borate bioactive glass scaffolds (with a composition in the system Na₂O–K₂O–MgO–CaO–B₂O₃–P₂O₅) as devices for the release of the drug Vancomycin in the treatment of bone infection. A solution of ammonium phosphate, with or without dissolved Vancomycin, was used to bond borate glass particles into the shape of pellets. The in vitro degradation of the pellets and their conversion to a hydroxyapatite-type material in a simulated body fluid (SBF) were investigated using weight loss measurements, chemical analysis, X-ray diffraction, and scanning electron microscopy. The results showed that greater than 90% of the glass in the scaffolds degraded within 1 week, to form poorly crystallized hydroxyapatite (HA). Pellets loaded with Vancomycin provided controlled release of the drug over 4 days. Vancomycin-loaded scaffolds were implanted into the right tibiae of rabbits infected with osteomyelitis. The efficacy of the treatment was assessed using microbiological examination and histology. The HA formed in the scaffolds in vivo, resulting from the conversion of the glass, served as structure to support the growth of new bone and blood vessels. The results in this work indicate that bioactive borate glass could provide a promising biodegradable and bioactive material for use as both a drug delivery system and a scaffold for bone repair.     

Synthesis of novel tricalcium phosphate-bioactive glass composite and functionalization with rhBMP-2

A functionalization is required for calcium phosphate-based bone substitute materials to achieve an entire bone remodeling. In this study it was hypothesized that a tailored composite of tricalcium phosphate and a bioactive glass can be loaded sufficiently with rhBMP-2 for functionalization. A composite of 40 wt% tricalcium phosphate and 60 wt% bioactive glass resulted in two crystalline phases, wollastonite and rhenanite after sintering. SEM analysis of the composite’s surface revealed a spongious bone-like morphology after treatment with different acids. RhBMP-2 was immobilized non-covalently by treating with chrome sulfuric acid (CSA) and 3-aminopropyltriethoxysilane (APS) and covalently by treating with CSA/APS, and additionally with 1,1′-carbonyldiimidazole. It was proved that samples containing non-covalently immobilized rhBMP-2 on the surface exhibit significant biological activity in contrast to the samples with covalently bound protein on the surface. We conclude that a tailored composite of tricalcium phosphate and bioactive glass can be loaded sufficiently with BMP-2.     

Fabrication of porous bioactive glass particles by one step sintering

In this study, we reported a facile method to prepare porous bioactive glass microparticles. Porous particles were synthesized by sintering hollow bioactive glass microspheres obtained using a sol-gel co-template technology. The results showed that porous bioactive glass particles possessed a narrow particle size distribution, a relatively porous surface morphology and a hollow structure. It is worth to say that the resulting microparticles present an amorphous structure although the sintering temperature was improved compared to hollow microspheres. The presence of macropore on the shell may provide an efficient method to carry drugs in the hollow cores. Considering the high deposit rate of nanoscale apatite for bioactive glass materials, the porous microparticles should have potential applications in drug and bioactive molecules delivery, in addition to bone tissue regeneration.     

Poly (l-lactide-co-Є caprolactone) microspheres laden with bioactive glass-ceramic and alendronate sodium as bone regenerative scaffolds

Microspheric scaffolds of poly-(lactide-co-caprolactone) loaded with alendronate sodium, a family precursor of bisphosphonate drug and bioactive glass-ceramic (BGS) were prepared for the treatment of osteoporosis like bone defects with the rationale of getting a combined effect/concurrent advantage of osteoclast apoptosis as well as the augmentation of bone regeneration. The porous microspheres were generated by oil in water/solvent evaporation technique. The distribution of bioactive glass-ceramic was evidenced by the microcomputed tomography (μ-CT) and scanning electron microscopy analyses. The microspheres were evaluated for their in vitro cytocompatibility using L929 cell line and were found to be noncytotoxic. The osteoinductivity of the scaffold was assessed by its response in simulated body fluid and observed an excellent hydroxy carbonate apatite (HCA) layer formation on the surface which revealed the bone bonding and bone regeneration capability of the scaffold. The cell adhesion studies was performed with L-929 cell line and a marking cell growth on the surface as well as in the pores of the bioactive glass-ceramic as well as bioactive glass-ceramic cum drug incorporated microspheres was evidenced by the Confocal laser scanning microscopy (CLSM) investigation. No cell adhesion was observed onto the surface of the bare microspheres prepared by the copolymer alone where as the bioactive glass-ceramic and drug cum bioactive glass-ceramic loaded microspheres were found to promote the cell adhesion. The viability of the adhered cells on the microspheres was checked by flourescein diacetate (FDA) staining and it was observed that the adhered cells were viable and metabolically active. The release of the drug, alendronate sodium, directly into the problem site makes the presently prepared microsphere superior to the oral variety of drug available which is associated with oral discomfort and low bioavailability.     

Evaluation of channel-like porous-structured titanium in mechanical properties and osseointegration

The porous titanium with a channel-like pore structure fabricated by infiltration casting followed by selectively dissolving the precursor woven three dimensional(3 D) structure technique was comprehensively investigated by means of mechanical tests, in vitro and in vivo evaluation. Such porous structure exhibited superiority in compressive, tensile strength and osseointegration. At 40% porosity, the average compressive and tensile strength reached about 145 MPa and 85 MPa, which was superior to that of other porous titanium, e.g., Selective Laser Melting or powder sintered ones, and was comparable to that of the human cortical bone. Without any bioactive surface treatment, this porous titanium exhibited good cell adhesion, rapid cell proliferation and excellent osseointegration. Based on the study, the 0.4 mm pore size resulted in the most rapid cell proliferation and the maximal BV/TV ratio and trabecular bone number of the new bone that ingrew into the porous titanium. To balance the excellent osseointegration and adequate mechanical properties, the optimal structural parameters were 0.4 mm pore size with40% porosity. This porous titanium is very promising for orthopedic applications where compressive and tensile load-bearing is extremely important.     

Development of porous HAp and β-TCP scaffolds by starch consolidation with foaming method and drug-chitosan bilayered scaffold based drug delivery system

The inability to maintain high concentrations of antibiotic at the site of infection for an extended period of time along with dead space management is still the driving challenge in treatment of osteomyelitis. Porous bioactive ceramics such as hydroxyapatite (HAp) and beta-tri calcium phosphate (β-TCP) were some of the alternatives to be used as local drug delivery system. However, high porosity and high interconnectivity of pores in the scaffolds play a pivotal role in the drug release and bone resorption. Ceftriaxone is a cephalosporin that has lost its clinical popularity. But has recently been reported to exhibit better bactericidal activity in vitro and reduced probability of resistance development, in combination with sulbactam, a β-lactamase inhibitor. In this article, a novel approach of forming HAp and pure β-TCP based porous scaffolds by applying together starch consolidation with foaming method was used. For the purpose, pure HAp and β-TCP were prepared in the laboratory and after thorough characterization (including XRD, FTIR, particle size distribution, etc.) the powders were used for scaffold fabrication. The ability of these scaffolds to release drugs suitably for osteomyelitis was studied in vitro. The results of the study indicated that HAp exhibited better drug release profile than β-TCP when drug was used alone indicating the high influence of the carrier material. However, this restriction got relaxed when a bilayered scaffold was formed using chitosan along with the drug. SEM studies along with EDAX on the drug-chitosan bilayered scaffold showed closest apposition of this combination to the calcium phosphate surface.     

Transplantation of nano-bioglass/gelatin scaffold in a non-autogenous setting for bone regeneration in a rabbit ulna

Bioactive glass has been investigated for variety of tissue engineering applications. In this study, fabrication, in vitro and in vivo evaluation of bioactive glass nanocomposite scaffold were investigated. The nanocomposite scaffolds with compositions based on gelatin and bioactive glass nanoparticles were prepared. The apatite formation at the surface of the nanocomposite samples confirmed by Fourier transform infrared spectroscopy, scanning electron microscopy and X-ray powder diffraction analyses. The in vitro characteristics of bioactive glass scaffold as well as the in vivo bone formation capacity of the bioactive glass scaffold in rabbit ulnar model were investigated. The bioactive glass scaffold showed no cytotoxicity effects in vitro. The nanocomposite scaffold made from gelatin and bioactive glass nanoparticles could be deliberated as an extremely bioactive and prospective bone tissue engineering implant. Bioactive glass scaffolds were capable of guiding bone formation in a rabbit ulnar critical-sized-defect model. Radiographic evaluation indicated that successful bridging of the critical-sized defect on the sides both next to and away from the radius took place using bioactive glass scaffolds. X-ray analysis also proposed that bioactive glass scaffolds supported normal bone formation via intramembranous formation     

Bioresorbable and bioactive polymer/Bioglass® composites with tailored pore structure for tissue engineering applications

An overview about the development of porous bioresorbable composite materials for applications as scaffolds in tissue engineering is presented. A thermally induced phase separation method was developed to fabricate porous foam-like structures of poly(lactide-co-glycolide) (PLGA) containing bioactive glass particle additions (up to 50 wt.%) and exhibiting well-defined, oriented and interconnected porosity. The in vitro bioactivity and the degradability of the composite foams were investigated in contact with phosphate buffer saline (PBS). Weight loss, water absorption and molecular weight measurements were used to monitor the polymer degradation after incubation periods of up to 7 weeks in PBS. It was found that the presence of bioactive glass retards the polymer degradation rate for the time period investigated. The present results show a way of controlling the in vitro degradation behaviour of PLGA porous composite scaffolds by tailoring the concentration of bioactive glass.     

A novel injectable borate bioactive glass cement for local delivery of vancomycin to cure osteomyelitis and regenerate bone

Osteomyelitis (bone infection) is often difficult to cure. The commonly-used treatment of surgical debridement to remove the infected bone combined with prolonged systemic and local antibiotic treatment has limitations. In the present study, an injectable borate bioactive glass cement was developed as a carrier for the antibiotic vancomycin, characterized in vitro, and evaluated for its capacity to cure osteomyelitis in a rabbit tibial model. The cement (initial setting time = 5.8 ± 0.6 min; compressive strength = 25.6 ± 0.3 MPa) released vancomycin over ~25 days in phosphate-buffered saline, during which time the borate glass converted to hydroxyapatite (HA). When implanted in rabbit tibial defects infected with methicillin-resistant Staphylococcus aureus (MRSA)-induced osteomyelitis, the vancomycin-loaded cement converted to HA and supported new bone formation in the defects within 8 weeks. Osteomyelitis was cured in 87 % of the defects implanted with the vancomycin-loaded borate glass cement, compared to 71 % for the defects implanted with vancomycin-loaded calcium sulfate cement. The injectable borate bioactive glass cement developed in this study is a promising treatment for curing osteomyelitis and for regenerating bone in the defects following cure of the infection.     

Systematic approach to treat chronic osteomyelitis through localized drug delivery system: Bench to bed side

Chronic osteomyelitis is a challenging setback to the orthopedic surgeons in deciding an optimal therapeutic strategy. Conversely, patients feel frustrated of the therapeutic outcomes and development of adverse drug effects, if any. Present investigation deals with extensive approach incorporating in vivo animal experimentation and human application to treat chronic osteomyelitis, using antibiotic loaded porous hydroxyapatite scaffolds. Micro- to macro-porous hydroxyapatite scaffolds impregnated with antibiotic ceftriaxone–sulbactam sodium (CFS) were fabricated and subsequently evaluated by in vivo animal model after developing osteomyelitis in rabbit tibia. Finally 10 nos. of human osteomyelitis patients involving long bone and mandible were studied for histopathology, radiology, pus culture, 3D CT etc. up to 8–18 months post-operatively. It was established up to animal trial stage that 50N50H samples [with 50–55% porosity, average pore size 110 μm, higher interconnectivity (10–100 μm), and moderately high drug adsorption efficiency (50%)] showed efficient drug release up to 42 days than parenteral group based on infection eradication and new bone formation. In vivo human bone showed gradual evidence of new bone formation and fracture union with organized callus without recurrence of infection even after 8 months. This may be a new, alternative, cost effective and ideal therapeutic strategy for chronic osteomyelitis treatment in human patients.     

Sol-Gel生物活性玻璃降解性能及矿化沉积的体外模拟研究

本研究采用溶胶-凝胶法制备了CaO-P2O5-SiO2系统生物活性玻璃粉体,并通过成型、烧结工艺制成多孔材料,样品在体外模拟实验系统中进行材料降解性能研究.通过测量溶液pH值、Ca2 浓度及样品的XRD、SEM、FTIR测试,认为生物活性玻璃本身发生降解的同时表面有一层类骨碳酸羟基磷灰石生成.     

Bioactive macroporous titanium implants highly interconnected

Intervertebral implants should be designed with low load requirements, high friction coefficient and low elastic modulus in order to avoid the stress shielding effect on bone. Furthermore, the presence of a highly interconnected porous structure allows stimulating bone in-growth and enhancing implant-bone fixation. The aim of this study was to obtain bioactive porous titanium implants with highly interconnected pores with a total porosity of approximately 57?%. Porous Titanium implants were produced by powder sintering route using the space holder technique with a binder phase and were then evaluated in an in vivo study. The size of the interconnection diameter between the macropores was about 210?μm in order to guarantee bone in-growth through osteblastic cell penetration. Surface roughness and mechanical properties were analyzed. Stiffness was reduced as a result of the powder sintering technique which allowed the formation of a porous network. Compression and fatigue tests exhibited suitable properties in order to guarantee a proper compromise between mechanical properties and pore interconnectivity. Bioactivity treatment effect in novel sintered porous titanium materials was studied by thermo-chemical treatments and were compared with the same material that had undergone different bioactive treatments. Bioactive thermo-chemical treatment was confirmed by the presence of sodium titanates on the surface of the implants as well as inside the porous network. Raman spectroscopy results suggested that the identified titanate structures would enhance in vivo apatite formation by promoting ion exchange for the apatite formation process. In vivo results demonstrated that the bioactive titanium achieved over 75?% tissue colonization compared to the 40?% value for the untreated titanium.     

介孔生物活性玻璃/脱钙骨复合支架的制备及性能研究

将介孔生物活性玻璃(MBG)与脱钙骨(DB)复合, 利用浸渍法制备出MBG/DB复合支架材料. 采用红外光谱(FTIR), 扫描电镜(SEM), X射线衍射(XRD), 电子万能材料试验机等方法对牛松质骨(CB)、DB、MBG/DB复合支架进行表征. 结果表明, CB经浸酸处理后制备的DB, 孔径大小在200~600μm范围内, 孔隙率约为71%, 抗压性能比CB明显降低(1.10±0.31)MPa, 而采用浸渍法制备的复合支架, 孔隙率降为40%左右, 而压缩强度明显提高(8.49± 2.14)MPa. 体外生物活性测试表明: 复合支架具有良好的生物活性.     

Simple methods to fabricate Bioglass<Superscript>®</Superscript>-derived glass–ceramic scaffolds exhibiting porosity gradient

The present paper discusses different processing technologies for fabrication of novel 45S5 Bioglass^®-derived glass–ceramic scaffolds with tailored porosity gradient for potential application in bone tissue engineering. Different types of scaffolds with continuous or stepwise gradient of porosity were produced by the foam replication technique, using preformed polyurethane (PU) foams as sacrificial templates. After preforming the PU foams in metallic moulds, they were dipped in a 45S5 Bioglass^®-based slurry and subsequently heat treated in a chamber furnace up to 1100 °C. During heating, the organic phase is burned out and the glass sinters and partially crystallises. By using this new approach, Bioglass^®-derived glass-ceramic scaffolds with different shapes and porosity profiles were designed. Scanning electron microscopy (SEM) showed that all samples have highly interconnected porous structure, with specific porosity gradients. By modifying the shape and dimensions of the metallic mould, bioactive glass–ceramic scaffolds with complex shapes and different degrees of porosity gradient could be obtained.     

Bioresorbable and bioactive composite materials based on polylactide foams filled with and coated by Bioglass® particles for tissue engineering applications

Poly(DL-lactide) (PDLLA) foams and bioactive glass (Bioglass®) particles were used to form bioresorbable and bioactive composite scaffolds for applications in bone tissue engineering. A thermally induced phase separation process was applied to prepare highly porous PDLLA foams filled with 10 wt % Bioglass® particles. Stable and homogeneous layers of Bioglass® particles on the surface of the PDLLA/Bioglass® composite foams as well as infiltration of Bioglass® particles throughout the porous network were achieved using a slurry-dipping technique. The quality of the bioactive glass coatings was reproducible in terms of thickness and microstructure. In vitro studies in simulated body fluid (SBF) were performed to study the formation of hydroxyapatite (HA) on the surface of the PDLLA/Bioglass® composites, as an indication of the bioactivity of the materials. Formation of the HA layer after immersion in SBF was confirmed by X-ray diffraction and Raman spectroscopy measurements. The rate of HA formation in Bioglass®-coated samples was higher than that observed in non-coated samples. SEM analysis showed that the HA layer thickness rapidly increased with increasing time in SBF in the Bioglass®-coated samples. The high bioactivity of the developed composites suggests that the materials are attractive for use as bioactive, resorbable scaffolds in bone tissue engineering.     

Freeze extrusion fabrication of 13–93 bioactive glass scaffolds for bone repair

A solid freeform fabrication technique, freeze extrusion fabrication (FEF), was investigated for the creation of three-dimensional bioactive glass (13–93) scaffolds with pre-designed porosity and pore architecture. An aqueous mixture of bioactive glass particles and polymeric additives with a paste-like consistency was extruded through a narrow nozzle, and deposited layer-by-layer in a cold environment according to a computer-aided design (CAD) file. Following sublimation of the ice in a freeze dryer, the construct was heated according to a controlled schedule to burn out the polymeric additives (below ~500°C), and to densify the glass phase at higher temperature (1 h at 700°C). The sintered scaffolds had a grid-like microstructure of interconnected pores, with a porosity of ~50%, pore width of ~300 μm, and dense glass filaments (struts) with a diameter or width of ~300 μm. The scaffolds showed an elastic response during mechanical testing in compression, with an average compressive strength of 140 MPa and an elastic modulus of 5–6 GPa, comparable to the values for human cortical bone. These bioactive glass scaffolds created by the FEF method could have potential application in the repair of load-bearing bones.