Preparation,characterization, in vitro bioactivity and protein loading/release property of mesoporous bioactive glass microspheres with different compositions

Mesoporous bioactive glass microspheres (MBGMs) with large mesopores have attracted considerable attention in the field of bone tissue regeneration and drug delivery systems due to their excellent bioactivity, biocompatibility and high specific area. In this study, a loose structure of MBGMs with adjustable chemical compositions was synthesized by the combination of sol-gel and water-in-oil (W/O) microemulsion. All the prepared MBGMs possessed a large mesopore diameter that increased with CaO content, a high surface area and good apatite-inducing formation ability. In vitro protein absorption and release assays demonstrated that the MBGMs exhibited decreased loading efficiency and burst release behavior as the CaO content increased. Additionally, an enhanced BSA-loading amount and prolonged release curve were obtained after the surfaces of MBGMs were modified by amine groups. Furthermore, the preliminary in vitro cell experiments showed that MBGMs exhibited good biocompatibility. The results indicated that MBGMs could be a promising candidate as a drug/protein carrier for bone tissue regeneration.     

Hollow carbonated hydroxyapatite microspheres with mesoporous structure: Hydrothermal fabrication and drug delivery property

Hollow carbonated hydroxyapatite microspheres with mesoporous structure (HCHAs) have been fabricated by using calcium carbonated microspheres as sacrificial templates according to the following routes: (i) the in situ deposit of carbonated hydroxyapatite on the surfaces of CaCO₃ microspheres by hydrothermal method and (ii) the removal of CaCO₃ by chemical etching. The HCHAs consist of a hollow core and a mesoporous shell. Interestingly, the shell of the microspheres is constructed by carbonated hydroxyapatite nanoplates as building blocks. Moreover, these nanoplates are composed of many smaller nanoparticles with different crystal orientations, and the mesopores exist among these nanoparticles. The HCHAs exhibit the high drug-loading capacity and sustained drug release property, suggesting that the hierarchically porous microspheres have great potentials for bone-implantable drug-delivery applications.     

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.     

MAS-NMR support for Hench model in the case of bioactive glass microspheres

The structural changes occurred in bioactive glass microspheres belonging to the system SiO₂–Na₂O–P₂O₅–CaO–K₂O–MgO incorporating yttrium were investigated before and after soaking in simulated body fluid (SBF) by X-ray diffraction (XRD) and ³¹P and ²⁹Si magic angle sample spinning nuclear magnetic resonance (MAS-NMR). The addition of yttrium to the bioactive glass composition induces changes in the behavior of the glass microspheres in SBF. The XRD analysis proves that after the immersion in SBF a crystalline hydroxyapatite-like phase is developed on the microspheres surface. The ²⁹Si and ³¹P MAS-NMR results show that silicate species with two and three bridging oxygens per SiO₄ tetrahedra and PO₄ monomeric units are present in the glass structure. After immersion in SBF, new silicate species with four bridging oxygens appear as result of silica-gel layer formed on microspheres surface. The formation of crystalline hydroxyapatite-type layer is reflected by the occurrence of narrow components in ³¹P MAS-NMR spectra. The NMR results support the Hench model for bioactive glasses behavior in biological environments.     

Fabrication and photocatalytic activity of porous TiO2 nanowire microspheres by surfactant-mediated spray drying process

A novel, porous TiO₂ nanowire microsphere with a diameter of 3-8 μm was successfully fabricated via spray drying of TiO₂ nanowire suspension with the assistance of surfactant (F127). The products were characterized by FESEM, XRD and N₂ adsorption-desorption analysis and results revealed that the resulting TiO₂ nanowire microspheres possessed a hierarchically macro/mesoporous structure, as well as a high BET surface area of 38.2 m²/g. Systematic studies showed that the presence of surfactant in the suspension feed for spray drying was critical in the formation of porous microspheres. The structure of the fabricated microspheres depends on the nanowire concentration in the feed. The TiO₂ nanowire microspheres exhibited significant photocatalytic degradation of Methylene blue (MB) as compared to commercial TiO₂ nanoparticles (P25). It was also revealed that the microspheres have excellent stability on photocatalytic activity and mechanical strength, which are both crucial factors when considering reuse of these photocatalysts.     

Amphiphilic Block Copolymers Directed Interface Coassembly to Construct Multifunctional Microspheres with Magnetic Core and Monolayer Mesoporous Aluminosilicate Shell

Core–shell magnetic porous microspheres have wide applications in drug delivery, catalysis and bioseparation, and so on. However, it is great challenge to controllably synthesize magnetic porous microspheres with uniform well‐aligned accessible large mesopores (>10 nm) which are highly desired for applications involving immobilization or adsorption of large guest molecules or nanoobjects. In this study, a facile and general amphiphilic block copolymer directed interfacial coassembly strategy is developed to synthesize core–shell magnetic mesoporous microspheres with a monolayer of mesoporous shell of different composition (FDUcs‐17D), such as core–shell magnetic mesoporous aluminosilicate (CS‐MMAS), silica (CS‐MMS), and zirconia‐silica (CS‐MMZS), open and large pores by employing polystyrene‐block‐poly (4‐vinylpyridine) (PS‐b‐P4VP) as an interface structure directing agent and aluminum acetylacetonate (Al(acac)₃), zirconium acetylacetonate, and tetraethyl orthosilicate as shell precursors. The obtained CS‐MMAS microspheres possess magnetic core, perpendicular mesopores (20–32 nm) in the shell, high surface area (244.7 m² g^?1), and abundant acid sites (0.44 mmol g^?1), and as a result, they exhibit superior performance in removal of organophosphorus pesticides (fenthion) with a fast adsorption dynamics and high adsorption capacity. CS‐MMAS microspheres loaded with Au nanoparticles (≈3.5 nm) behavior as a highly active heterogeneous nanocatalyst for N‐alkylation reaction for producing N‐phenylbenzylamine with a selectivity and yields of over 90% and good magnetic recyclability.     

介孔硼硅酸盐玻璃微球药物载体的制备及其性能表征

介孔二氧化硅微粒具有化学稳定性好、比表面积大和表面易修饰等特点, 作为药物载体具有良好的应用前景, 但其缺乏生物活性且生物降解缓慢等在一定程度上限制了它的应用领域。为克服这些缺陷, 寻找合适的药物载体已成为重要研究方向。与纯二氧化硅相比, 硼硅酸盐玻璃具有良好的生物活性和更高的降解速率。基于此, 本研究尝试合成介孔硼硅酸盐玻璃微球(MBGMs), 并表征了其在负载和释放抗肿瘤药物盐酸阿霉素(DOX)过程中的载体特性和材料降解引发的各种功能性离子的释放行为。结果表明BMGMs具有约25 mg/g的DOX负载量,引入硼不仅可以调控MBGMs的化学活性和降解速率, 而且较高硼含量的MBGMs可促进酸性条件下的药物释放, 具有一定的酸性响应性。此外, MBGMs可在模拟体液中释放SiO₄^4-、BO₃^3-和Ca²⁺等有益骨组织生长的功能性离子, 并诱导生成羟基磷灰石, 具备良好的离子缓释能力和体外矿化活性。因此, MBGMs作为一种新颖的药物载体材料, 既可作为药物和功能离子的双重负载, 又具有良好的生物活性和降解特性, 在病理性骨缺损修复领域具有良好的应用前景。     

Synthesis and in vitro bioactivity of novel mesoporous hollow bioactive glass microspheres

The remarkable tissue-repairing bioactivity and biocompatibility of bioactive glass make it suitable for a wide range of applications. Here, novel mesoporous hollow bioactive glass microspheres (MHBGMs) with a uniform diameter range of 2-5 µm were prepared by a sol-gel method. Structural characterization indicated that the shell of hollow sphere had a mesopore size range between 2 and 10 nm and a thickness about 500 nm. The in vitro bioactivity test indicated that the novel structure exhibited high in vitro bioactivity. The uniform microspherical morphology and mesoporous hollow structure of MHBGMs, together with their high bioactivity, turn them into a good candidate as an injectable and drug-loading biomaterial for in vivo tissue regeneration and drug control release.     

In situ preparation and protein delivery of silicate–alginate composite microspheres with core-shell structure

The efficient loading and sustained release of proteins from bioactive microspheres remain a significant challenge. In this study, we have developed bioactive microspheres which can be loaded with protein and then have a controlled rate of protein release into a surrounding medium. This was achieved by preparing a bioactive microsphere system with core-shell structure, combining a calcium silicate (CS) shell with an alginate (A) core by a one-step in situ method. The result was to improve the microspheres'' protein adsorption and release, which yielded a highly bioactive material with potential uses in bone repair applications. The composition and the core-shell structure, as well as the formation mechanism of the obtained CS–A microspheres, were investigated by X-ray diffraction, optical microscopy, scanning electron microscopy, energy dispersive spectrometer dot and line-scanning analysis. The protein loading efficiency reached 75 per cent in CS–A microspheres with a core-shell structure by the in situ method. This is significantly higher than that of pure A or CS–A microspheres prepared by non-in situ method, which lack a core-shell structure. CS–A microspheres with a core-shell structure showed a significant decrease in the burst release of proteins, maintaining sustained release profile in phosphate-buffered saline (PBS) at both pH 7.4 and 4.3, compared with the controls. The protein release from CS–A microspheres is predominantly controlled by a Fickian diffusion mechanism. The CS–A microspheres with a core-shell structure were shown to have improved apatite-mineralization in simulated body fluids compared with the controls, most probably owing to the existence of bioactive CS shell on the surface of the microspheres. Our results indicate that the core-shell structure of CS–A microspheres play an important role in enhancing protein delivery and mineralization, which makes these composite materials promising candidates for application in bone tissue regeneration.     

One‐step method for the preparation of poly(methyl methacrylate) modified titanium‐bioactive glass three‐dimensional scaffolds for bone tissue engineering

A novel three‐dimensional (3D) titanium (Ti)‐doping meso‐macroporous bioactive glasses (BGs)/poly(methyl methacrylate) (PMMA) composite was synthesised using PMMA and EO₂₀ PO₇₀ EO₂₀ (P₁₂₃) as the macroporous and mesoporous templates, respectively. Unlike the usual calcination method, the acid steam technique was used to improve the polycondensation of Ti‐BGs, and then PMMA was partially extracted via chloroform to induce the macroporous structure. Simultaneously, the residual PMMA which remained in the wall enhanced the compressive strength to 2.4 MPa (0.3 MPa for pure BGs). It is a simple and green method to prepare the macro‐mesoporous Ti‐BGs/PMMA. The materials showed the 3D interconnected hierarchical structure (250 and 3.4 nm), making the fast inducing‐hydroxyapatite growth and the controlled drug release. Besides mentioned above, the good antimicrobial property and biocompatible of the scaffold also ensure it is further of clinical use. Herein, the fabricated materials are expected to have potential application on bone tissue regeneration.Inspec keywords: titanium, bone, tissue engineering, glass, materials preparation, biomedical materials, polymers, porous materials, drug delivery systems, nanomedicineOther keywords: poly(methyl methacrylate), PMMA preparation, 3D titanium‐bioactive glass scaffold, bone tissue engineering, titanium‐doping mesomacroporous bioactive glass, bioactive glass‐PMMA composite, macroporous template, mesoporous template, calcination method, acid steam technique, titanium‐bioactive glass polycondensation, macroporous structure, green method, macromesoporous titanium‐bioactive glass‐PMMA, 3D interconnected hierarchical structure, fast inducing‐hydroxyapatite growth, controlled drug release, bone tissue regeneration, Ti     

An emulsification–solvent evaporation route to mesoporous bioactive glass microspheres for bisphosphonate drug delivery

Regular spherical mesoporous bioactive glass microspheres (MBG-MSs) with tunable SiO₂–CaO–P₂O₅ composition and adjustable mesoporous structure have been synthesized by a new approach of emulsification and solvent evaporation-induced self-assembly. Less ordered mesostructure and enhanced bioactivity resulting from the addition of CaO are investigated through scanning electron microscopy, transmission electron microscopy, Fourier transform infrared spectroscopy, and X-ray diffraction characterizations. The MBG-MSs have high storage capacities and sustained release patterns of anti-osteoporosis (alendronate sodium, NaAL) drugs which are hardly absorbed via oral administration. Furthermore, to some extent the dosage and release rate could also be controlled by CaO content. Cell viability and proliferation assay with rabbit bone marrow stromal cells indicates a positive effect of the CaO/P₂O₅ components on improving the cell growth cumulatively in about 2 weeks.     

Mesoporous bioactive glass as a drug delivery system: fabrication, bactericidal properties and biocompatibility

Implant-associated infection remains a difficult medical problem in orthopaedic surgery. Here, we report on the fabrication of gentamicin-loaded mesoporous bioactive glass (Gent-MBG) for use as a controlled antibiotic delivery system to achieve the sustained release of antibiotics in the local sites of bone defects. The high surface area and mesoporous structure of MBG enable higher drug loading efficiency (79–83 %) than non-mesoporous biological glass (NBG) (18–19 %). Gent-MBG exhibits sustained drug release for more than 6 days, and this controlled release of gentamicin significantly inhibits bacterial adhesion and prevents biofilm formation by S. aureus (ATCC25923) and S. epidermidis (ATCC35984). Biocompatibility tests with human bone marrow stromal cells (hBMSCs) indicate that MBG has better biocompatibility than NBG. Therefore, Gent-MBG can be used as a controlled drug delivery system to prevent and/or treat orthopedic peri-implant infections.     

Controlled release of BSA by microsphere-incorporated PLGA scaffolds under cyclic loading

Localized delivery of bioactive molecules from porous biodegradable scaffolds is very important in advanced tissue engineering strategies, and it is necessary to study the delivery under dynamic loading which mimics the in vivo biomechanical environments. In this study, bovine serum albumin (BSA), a model of bioactive proteins, was incorporated into porous poly(l-lactide-co-glycolide) (PLGA) scaffolds by seeding BSA-loaded microspheres onto the scaffold pore wall, where the microspheres of poly(ethylene glycol)-b-poly(l-lactide) (PELA) were prepared by double emulsion technique. The in vitro release behavior of BSA from the scaffold under dynamic cyclic loading was studied in comparison with that under a static condition as well as from PELA microspheres. It was observed that the microsphere-incorporated scaffold prolonged BSA release with respect to the microspheres. The cyclic loading accelerated the release of BSA from the scaffold and the cumulative release on day 10 reached 85% of the totally encapsulated BSA. The delivery under a dynamic condition would be an initial study of in vivo localized delivery of growth factors.     

分级介孔结构组成的ZnO微球及光催化性能

以硝酸锌、脲素及酒石酸为反应物, 采用水热法制备碱式碳酸锌前驱体微球, 通过煅烧前驱体制备了介孔氧化锌微球。通过扫描电子显微镜(SEM)可以观察到, 氧化锌微球的直径约为2~4 μm, 由大量厚度约为10 nm的介孔纳米片组装而成。X 射线衍射(XRD)和透射电镜(TEM)结果表明: ZnO微球为六方纤锌矿结构, 并结晶较好。比表面积测试(BET)表明ZnO微球为介孔材料, 孔径为20~50 nm, ZnO微球比表面积约为29.8 m²/g。以亚甲基蓝为目标降解物, 对介孔氧化锌微球进行了光催化降解实验。实验结果表明, 所合成的介孔ZnO微球对亚甲基蓝的光催化性能较好。     

Bioactive glass nanotube scaffold with well-ordered mesoporous structure for improved bioactivity and controlled drug delivery

In this study, a novel mesoporous bioactive glass nanotube (MBGN) scaffold has been fabricated via template-assisted sol-gel method using bacterial cellulose (BC) as template and nonionic block copolymer (P123) as pore-directing agent. The scaffold was characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier-transform infrared (FTIR) spectroscopy, and N₂ adsorption-desorption analysis. Furthermore, simvastatin was used to evaluate the loading efficiency and release kinetics of the scaffold. The obtained scaffold displays nanofiber-like morphology, ordered mesopores on the tube walls, and interconnected three-dimensional (3D) network structure that completely replicates the BC template. In addition, it shows dual pore sizes (16.2 and 3.3 nm), large specific surface area (537.2 m² g⁻¹) and pore volume (1.429 cm³ g⁻¹). More importantly, the scaffold possesses excellent apatite-forming ability and sustainable drug release as compared to the counterpart scaffold without mesopores. This unique scaffold can be considered a promising candidate for drug delivery and bone tissue regeneration.     

Fabrication of hollow mesoporous NiO hexagonal microspheres via hydrothermal process in ionic liquid

The novel NiO hexagonal hollow microspheres have been successfully prepared by annealing Ni(OH)₂, which was synthesized via an ionic liquid-assisted hydrothermal method. The samples were characterized by X-ray diffraction (XRD), field emission scanning electron microscope (FE-SEM), transmission electron microscopy (TEM), N₂ adsorption-desorption and Fourier transform infrared spectrometer (FTIR). The results show that the hollow NiO microstructures are self-organized by mesoporous cubic and hexagonal nanocrystals. The mesoporous structure possessed good thermal stability and high specific surface area (ca. 83 m²/g). The ionic liquid 1-butyl-3methylimidazolium tetrafluoroborate ([Bmim][BF₄]) was found to play a key role in controlling the morphology of NiO microstructures during the hydrothermal process. The special hollow mesoporous architectures will have potential applications in many fields, such as catalysts, absorbents, sensors, drug-delivery carriers, acoustic insulators and supercapacitors.     

Sol–gel derived composite from bioactive glass–polyvinyl alcohol

Investigation of novel biomaterials for bone engineering is based on the development of porous scaffolds, which should match the properties of the tissue that is to be replaced. These materials need to be biocompatible, ideally osteoinductive, osteoconductive, and mechanically well-matched. In the present paper, we report the preparation and characterization of hybrid macroporous scaffold of polyvinyl alcohol (PVA)/bioactive glass through the sol–gel route. Hybrids containing PVA (80, 70 and 60 wt%) and bioactive glass with composition 58SiO₂–33CaO–9P₂O₅ were synthesized by foaming a mixture of polymer solution and bioactive glass via sol–gel precursor solution. PVA with two different degree of hydrolysis (DH), 98.5% (high degree) and 80% (low degree) were also investigated, in order to evaluate the influence of residual acetate group present in polymer chain on the final structure and properties of 3D porous composite produced. The microstructure, morphology and crystallinity of the hybrid porous scaffolds were characterized by X-ray diffraction (XRD), Infrared Fourier Transform spectrometry (FTIR) and Scanning electron microscopy (SEM/EDX) analysis. In addition, specific surface area was assessed by B.E.T. nitrogen adsorption method and mechanical behavior was evaluated by compression tests. Preliminary cytotoxicity and cell viability were also performed by the MTT assay. VERO cell monolayers were grown in 96-well microtiter plates. The results have clearly showed that hybrid foams of polyvinyl alcohol/bioactive glass (PVA/BG) with interconnected macroporous 3D structure were successfully produced. All the tested hybrids of PVA/BG have showed adequate cell viability properties for potential biological applications.     

Mesoporous Metal–Metalloid Amorphous Alloys: The First Synthesis of Open 3D Mesoporous Ni‐B Amorphous Alloy Spheres via a Dual Chemical Reduction Method

Selective hydrogenation of nitriles is an industrially relevant synthetic route for the preparation of primary amines. Amorphous metal–boron alloys have a tunable, glass‐like structure that generates a high concentration of unsaturated metal surface atoms that serve as active sites in hydrogenation reactions. Here, a method to create nanoparticles composed of mesoporous 3D networks of amorphous nickel–boron (Ni‐B) alloy is reported. The hydrogenation of benzyl cyanide to β‐phenylethylamine is used as a model reaction to assess catalytic performance. The mesoporous Ni‐B alloy spheres have a turnover frequency value of 11.6 h^?1, which outperforms non‐porous Ni‐B spheres with the same composition. The bottom‐up synthesis of mesoporous transition metal–metalloid alloys expands the possible reactions that these metal architectures can perform while simultaneously incorporating more Earth‐abundant catalysts.     

Synthesis and characterization of manganese containing mesoporous bioactive glass nanoparticles for biomedical applications

Mesoporous bioactive glass (BG) nanoparticles based in the system: SiO₂–P₂O₅–CaO–MnO were synthesized via a modified Stöber process at various concentrations of Mn (0–7 mol %). The synthesized manganese-doped BG nanoparticles were characterized in terms of morphology, composition, in vitro bioactivity and antibacterial activity. Scanning electron microscopy (SEM), transmission electron microscopy (TEM) and Brunauer–Emmett–Teller (BET) analysis confirmed that the particles had spherical morphology (mean particle size: 110?nm) with disordered mesoporous structure. Energy dispersive X-ray spectroscopy (EDX) confirmed the presence of Mn, Ca, Si and P in the synthesized Mn-doped BG particles. Moreover, X-ray diffraction (XRD) analysis showed that Mn has been incorporated in the amorphous silica network (bioactive glass). Moreover, it was found that manganese-doped BG particles form apatite crystals upon immersion in simulated body fluid (SBF). Inductively coupled plasma atomic emission spectroscopy (ICP-OES) measurements confirmed that Mn is released in a sustained manner, which provided antibacterial effect against Bacillus subtilis, Pseudomonas aeruginosa and Staphylococcus aureus. The results indicate that the incorporation of Mn in the bioactive glass network is an effective strategy to develop novel multifunctional BG nanoparticles for bone tissue engineering.     

Tb<Superscript>3+</Superscript> photoluminescence in mesoporous glasses,terbium nitrate and terbium chloride hexahydrates,and coordination compounds

We have compared the intensity and shape of photoluminescence spectra of Tb³⁺ ions in mesoporous glasses, inorganic phosphors (terbium nitrate and terbium chloride hexahydrates), and coordination compounds (terbium benzoate, terbium o-phenoxybenzoate, and terbium terephthalate). The excitation sources used were a repetitively pulsed nitrogen laser with an emission wavelength of 337 nm and cw semiconductor light-emitting diodes with wavelengths of 369 and 385 nm. It has been shown that the highest photoluminescence intensity normalized by the percentage of terbium is offered by terbium terephthalate and terbium- doped mesoporous glass. We are thus led to conclude that introducing terbium terephthalate into the pores of mesoporous photonic glass and mesoporous photonic crystals is a promising approach for obtaining efficient laser operation in the green spectral region on the ⁵D₄–7F₅ transition of the terbium ion.