Guohou Miao

Size control and biological properties of monodispersed mesoporous bioactive glass sub-micron spheres

We report a facile method for fabricating monodispersed mesoporous bioactive glass sub-micron spheres (MBGS) using dodecylamine (DDA) as a catalyst and template agent in a sol–gel process by self-assembly between a neutral organic surfactant and neutral inorganic precursor (S0I0). Moreover, we investigate the effect of sub-micron particle size on the physicochemical properties, apatite-forming ability, and biocompatibility of MBGS. Results showed that all samples exhibited regular spherical morphology and favorable mono-dispersibility. The average particle diameters of MBGS (200–800 nm) were controlled by adjusting the concentration of DDA. All samples induced the formation of rod-like apatite precipitates, which closely resembled the natural nanoscale apatite crystal, showing their high apatite-forming ability. Furthermore, MBGS surfaces also supported the attachment and promoted proliferation of alkaline phosphatase (ALP) activity of MG-63 cells, showing the good biocompatibility of MBGS. MBGS-1 had the smallest particle size and it was found that it could significantly enhance MG-63 proliferation and differentiation because of the smaller particle size and higher specific surface area. It is hoped that this study may motivate the development and applications of submicron biomaterials for bone repair applications.

Angiogenesis stimulated by novel nanoscale bioactive glasses

The ability of biomaterials to induce rapid vascular formation is critical in tissue regeneration. Combining recombinant angiogenic growth factors with bioengineered constructs have proven to be difficult due to several issues, including the instability of recombinant proteins, the need for sustained delivery and the dosage of factors. New formulations of bioactive glass, 58S nanosized bioactive glass (58S-NBG), have been reported to enhance wound healing in animal models better than the first generation of 45S5 Bioglass. Therefore, we investigated the effects of extracts of 58S-NBG and 80S-NBG on cultures of human umbilical vein endothelial cells (HUVECs). Cell viability was assessed by MTS assay. In vitro angiogenesis was measured using an ECM gel tube formation assay, and levels of mRNAs for five angiogenic related genes were measured by qRT-PCR. Extracts of 58S-NBG and 80S-NBG stimulated the proliferation of HUVECs, accelerated cell migration, up-regulated expression of the vascular endothelial growth factor, basic fibroblast growth factor, their receptors, and endothelial nitric oxide synthase, resulting in enhanced tube formation in vitro. The enhanced angiogenic response correlated with increased levels of Ca and Si in the extracts of 58S-NBG and 80S-NBG. The ability of 58S-NBG and 80S-NBG to stimulate angiogenesis in vitro provides alternative approaches for stimulating neovascularization of tissue-engineered constructs.

Synthesis of radial mesoporous bioactive glass particles to deliver osteoactivin gene

Mesoporous bioactive glasses (MBGs) can be used as carriers for biomolecule delivery with improved functions. Although there are a great number of studies on drug delivery by MBGs, until now little work has been done to investigate the DNA gene transfection effect of MBGs. In this study, radial mesoporous bioactive glasses (rMBGs) were prepared by sol-gel process combined with a micro-emulsion method. The surface was further modified by amino groups in order to improve its affinity for DNA. Our study showed that rMBGs have good apatite-forming ability and cellular biocompatibility. In addition, rMBGs can enter cells in a time- and dose-dependent manner, and mainly localize in the cytoplasm. Agarose gel electrophoresis demonstrated that pOA-EGFP (containing the osteoactivin and the green fluorescent protein fusion gene) can be completely absorbed and protected from DNase I degradation by the aminated rMBGs. Additionally, the plasmid can be successfully expressed in cells transfected by rMBGs.

Investigation of emulsified, acid and acid-alkali catalyzed mesoporous bioactive glass microspheres for bone regeneration and drug delivery

Acid-catalyzed mesoporous bioactive glass microspheres (MBGMs-A) and acid-alkali co-catalyzed mesoporous bioactive glass microspheres (MBGMs-B) were successfully synthesized via combination of sol-gel and water-in-oil (W/O) micro-emulsion methods. The structural, morphological and textural properties of mesoporous bioactive glass microspheres (MBGMs) were characterized by various techniques. Results show that both MBGMs-A and MBGMs-B exhibit regularly spherical shape but with different internal porous structures, i.e., a dense microstructure for MBGMs-A and internally porous structure for MBGMs-B. (29)Si NMR data reveal that MGBMs have low polymerization degree of silica network. The in vitro bioactivity tests indicate that the apatite formation rate of MBGMs-B was faster than that of MBGMs-A after soaking in simulated body fluid (SBF) solution. Furthermore, the two kinds of MBGMs have similar storage capacity of alendronate (AL), and the release behaviors of AL could be controlled due to their unique porous structure. In conclusion, the microspheres are shown to be promising candidates as bone-related drug carriers and filling materials of composite scaffold for bone repair.

Acute toxicity and in vivo biodistribution of monodispersed mesoporous bioactive glass spheres in intravenously exposed mice

The use of biomaterials from laboratories to clinics requires exhaustive and elaborate studies involving the biodistribution, clearance, and biocompatibility of biomaterials for in vivo biomedical applications. This study aimed to evaluate the acute toxicity and biodistribution of intravenously administrated sub-micrometer mesoporous bioactive glass spheres (SMBGs) in mice. The lethal dose 50 (LD50) of SMBGs was higher than 250 mg/kg. The acute toxicity was evaluated at 14 days after intravenous injection of SMBGs at 20, 100 and 180 mg/kg in ICR mice. The mortality, coefficients of major organs, hematology data and blood biochemical indexes revealed the low in vivo toxicity of SMBGs at all doses. However, the histological examination showed lymphocytic infiltration and granuloma formation in hepatocyte and megakaryocyte hyperplasia in the spleen at high dose. The silicon content analysis using ICP-OES and TEM results indicated that SMBGs mainly distributed in the resident macrophages of the liver and spleen, and could be cleared from the body more than 2 weeks. These findings can be important for the toxicity assessment of sub-micrometer particles and the development of bioactive glass based drug delivery system for biomedical applications.

Regulation of cellular behaviors of fibroblasts related to wound healing by sol-gel derived bioactive glass particles.

Sol-gel derived bioactive glass (BG) holds great potential in the application of skin repair. However, the specific regulation of BG on skin cells is still unclear and demands more investigation. Herein, we synthesized sol-gel derived BGs with different compositions (60S, 70S, 80S, and 90S) and found 90S BGs (90 mol % SiO2 , 6 mol % CaO, 4 mol % P2 O5 ) exhibited the best supportiveness for the proliferation of normal human foreskin fibroblasts. Thus, 90S BG particles were used as a model to systematically study the wound healing related cellular response of fibroblasts to BGs. Time-lapse imaging revealed a promoted fibroblast motility stimulated by 90S BG particles. Results on the expression of extracellular matrix (ECM) related genes illustrated that 90S BG particles modulated the synthesis capacity for critical ECM molecules including type I collagen, type III collagen, fibronectin, and tenascin-C. Moreover, the myofibroblastic differentiation of fibroblasts was greatly inhibited by 90S BG particles. Further analysis on the intracellular signaling pathways demonstrated that 90S BG particles down-regulated the collagen synthesis and fibroblast-to-myofibroblast differentiation via TGF-β1-Smad2 signaling, evidenced by the decreased expression levels of TGF-β receptor I and its downstream effector Smad2. Our study provided a further understanding of the specific regulation of 90S BG particles on fibroblasts, which may guide the future design of BG based wound dressing and benefit the clinical application of BG particles in skin repair.