Project description:Monodispersed spherical Ag-doped bioactive glass nanoparticles (Ag-BGNs) were synthesized by a modified Stöber method combined with surface modification. The surface modification was carried out at 25, 60, and 80 °C, respectively, to investigate the influence of processing temperature on particle properties. Energy-dispersive X-ray spectroscopy (EDS) results indicated that higher temperatures facilitate the incorporation of Ag. Hydroxyapatite (HA) formation on Ag-BGNs was detected upon immersion of the particles in simulated body fluid for 7 days, which indicated that Ag-BGNs maintained high bioactivity after surface modification. The conducted antibacterial assay confirmed that Ag-BGNs had an antibacterial effect on E. coli. The above results thereby suggest that surface modification is an effective way to incorporate Ag into BGNs and that the modified BGNs can remain monodispersed as well as exhibit bioactivity and antibacterial capability for biomedical applications.
Project description:The nanostructure of engineered bioscaffolds has a profound impact on cell response, yet its understanding remains incomplete as cells interact with a highly complex interfacial layer rather than the material itself. For bioactive glass scaffolds, this layer comprises of silica gel, hydroxyapatite (HA)/carbonated hydroxyapatite (CHA), and absorbed proteins-all in varying micro/nano structure, composition, and concentration. Here, we examined the response of MC3T3-E1 pre-osteoblast cells to 30 mol% CaO-70 mol% SiO2 porous bioactive glass monoliths that differed only in nanopore size (6-44 nm) yet resulted in the formation of HA/CHA layers with significantly different microstructures. We report that cell response, as quantified by cell attachment and morphology, does not correlate with nanopore size, nor HA/CHO layer micro/nano morphology, or absorbed protein amount (bovine serum albumin, BSA), but with BSA's secondary conformation as indicated by its β-sheet/α-helix ratio. Our results suggest that the β-sheet structure in BSA interacts electrostatically with the HA/CHA interfacial layer and activates the RGD sequence of absorbed adhesion proteins, such as fibronectin and vitronectin, thus significantly enhancing the attachment of cells. These findings provide new insight into the interaction of cells with the scaffolds' interfacial layer, which is vital for the continued development of engineered tissue scaffolds.
Project description:Several virulence lipids populate the outer cell wall of pathogenic mycobacteria. Phthiocerol dimycocerosate (PDIM), one of the most abundant outer membrane lipids, plays important roles in both defending against host antimicrobial programs and in evading these programs altogether. Immediately following infection, mycobacteria rely on PDIM to evade Myd88-dependent recruitment of microbicidal monocytes which can clear infection. To circumvent the limitations in using genetics to understand virulence lipids, we developed a chemical approach to track PDIM during Mycobacterium marinum infection of zebrafish. We found that PDIM's methyl-branched lipid tails enabled it to spread into host epithelial membranes to prevent immune activation. Additionally, PDIM's affinity for cholesterol promoted this phenotype; treatment of zebrafish with statins, cholesterol synthesis inhibitors, decreased spreading and provided protection from infection. This work establishes that interactions between host and pathogen lipids influence mycobacterial infectivity and suggests the use of statins as tuberculosis preventive therapy by inhibiting PDIM spread.
Project description:Microfluidic instrumentation offers unique advantages in biotechnology applications including reduced sample and reagent consumption, rapid mixing and reaction times, and a high degree of process automation. As dimensions decrease, the ratio of surface area to volume within a fluidic architecture increases, which gives rise to some of the unique advantages inherent to microfluidics. Thus, manipulation of surface characteristics presents a promising approach to tailor the performance of microfluidic systems. Microfluidic valves are essential components in a number of small volume applications and for automated microfluidic platforms, but rigorous evaluation of the sealing quality of these valves is often overlooked. In this work, the glass valve seat of hybrid glass/PDMS microfluidic valves was surface modified with hydrophobic silanes, octyldimethylchlorosilane (ODCS) or (tridecafluoro-1,1,2,2-tetrahydrooctyl)dimethylchlorosilane (PFDCS), to investigate the effect of surface energy on electrical resistance of valves. Valves with ODCS- or PFDCS-modified valve seats both exhibited >70-fold increases in electrical resistance (>500 G?) when compared to the same valve design with unmodified glass valve seats (7 ± 3 G?), indicative of higher sealing capacity. The opening times for valves with ODCS- or PFDCS-modified valve seats was ca. 5× shorter compared to unmodified valve seats, whereas the closing time was up to 8× longer for modified valve seats, although the total closing time was ?1.5 s, compatible with numerous microfluidic valving applications. Surface modified valve assemblies offered sufficient electrical resistance to isolate sub-pA current signals resulting from electrophysiology measurement of ?-hemolysin conductance in a suspended lipid bilayer. This approach is well-suited for the design of novel microfluidic architectures that integrate fluidic manipulations with electrophysiological or electrochemical measurements.
Project description:Polyetheretherketone (PEEK) is an important material applied in orthopedic applications, as it posses favorable properties for orthopedic implants, e.g., radiolucency and suitable elastic modulus. However, PEEK exhibits insufficient osteogenesis and osteointegration that limits its clinical applications. In this study, we aimed to enhance the osteogenisis of PEEK by using a surface coating approach. Nanocomposite coating composed of albumin/lithium containing bioactive glass nanospheres was fabricated on PEEK through dip-coating method. The presence of nanocomposite coating on PEEK was confirmed by SEM, FTIR, and XRD techniques. Nanocomposite coatings significantly enhanced hydrophilicity and roughness of PEEK. The nanocomposite coatings also enhanced adhesion, proliferation, and osteogenic differentiation of bone mesenchymal stem cells due to the presence of bioactive glass nanospheres and the BSA substrate film. The results indicate the great potential of the nanocomposite coating in enhancing osteogenesis and osteointegration of PEEK implants.
Project description:Owing to their exceptional physical, chemical, and mechanical properties, carbon nanotubes (CNTs) have been extensively studied for their effect on cellular behaviors. However, little is known about the process by which cells attach and spread on CNTs and the process for cell attachment and spreading on individual single-walled CNTs has not been studied. Cell adhesion and spreading is essential for cell communication and regulation and the mechanical interaction between cells and the underlying substrate can influence and control cell behavior and function. A limited number of studies have described different adhesion mechanisms, such as cellular process entanglements with multi-walled CNT aggregates or adhesion due to adsorption of serum proteins onto the nanotubes. Here, we hypothesized that cell attachment and spreading to both individual single-walled CNTs and multi-walled CNT aggregates is governed by the same mechanism. Specifically, we suggest that cell attachment and spreading on nanotubes is integrin-dependent and is facilitated by the adsorption of serum and cell-secreted adhesive proteins to the nanotubes.
Project description:Sol-gel-derived bioactive glass nanoparticles have attracted special interest due to their potential as novel therapeutic and regenerative agents. Significant challenges are yet to be addressed. The fabrication of sol-gel-derived nanoparticles in binary and ternary systems with an actual composition that meets the nominal has to be achieved. This work addresses this challenge and delivers nanoparticles in a ternary system with tailored composition and particle size. It also studies how specific steps in the fabrication process can affect the incorporation of the metallic ions, nanoparticle size, and mesoporosity. Sol-gel-derived bioactive glass nanoparticles in the 62 SiO2-34.5 CaO-3.2 P2O5 (mol %) system have been fabricated and characterized for their structural, morphological, and elemental characteristics using Fourier transform infrared spectroscopy, X-ray diffraction analysis, scanning electron microscopy associated with elemental analysis, transmission electron microscopy, and solid-state nuclear magnetic resonance. The fabricated nanoparticles were additionally observed to form the apatite phase when immersed in simulated body fluid. This work highlights the effect of the different processing variables, such as the nature of the solvent, the order in which reagents are added, stirring time, and the concentrations in the catalytic solution on the controlled incorporation of specific ions (e.g., P and Ca) in the nanoparticle network and particle size.
Project description:Polycaprolactone (PCL)-based composite scaffolds containing 50 wt% of 45S5 bioactive glass (45S5) or strontium-substituted bioactive glass (SrBG) particles were fabricated into scaffolds using melt-extrusion based additive manufacturing technique. Additionally, the PCL scaffolds were surface coated with a layer of calcium phosphate (CaP). For a comparison of the scaffold degradation, the scaffolds were then subjected to in vitro accelerated degradation by immersion in 5 M sodium hydroxide (NaOH) solution for up to 7 days. The scaffold?s morphology was observed by means of SEM imaging and scaffold mass loss was recorded over the experimental period.
Project description:Bone metastases are a frequent complication in prostate cancer, and several studies have shown that vitamin D deficiency promotes bone metastases. However, while many studies focus on vitamin D's role in cell metabolism, the effect of chronically low vitamin D levels on bone tissue, i.e. insufficient mineralization of the tissue, has largely been ignored. To investigate, whether poor tissue mineralization promotes cancer cell attachment, we used a fluorescence based adhesion assay and single cell force spectroscopy to quantify the adhesion of two prostate cancer cell lines to well-mineralized and demineralized dentin, serving as biomimetic bone model system. Adhesion rates of bone metastases-derived PC3 cells increased significantly on demineralized dentin. Additionally, on mineralized dentin, PC3 cells adhered mainly via membrane anchored surface receptors, while on demineralized dentin, they adhered via cytoskeleton-anchored transmembrane receptors, pointing to an interaction via exposed collagen fibrils. The adhesion rate of lymph node derived LNCaP cells on the other hand is significantly lower than that of PC3 and not predominately mediated by cytoskeleton-linked receptors. This indicates that poor tissue mineralization facilitates the adhesion of invasive cancer cells by the exposure of collagen and emphasizes the disease modifying effect of sufficient vitamin D for cancer patients.
Project description:To prepare nanocomposite cements based on the incorporation of bioactive glass nanoparticles (nBGs) into BiodentineTM (BD, Septodent, Saint-Maur-des-Fosses Cedex, France) and to assess their bioactive properties.nBGs were synthesised by the sol-gel method. BD nanocomposites (nBG/BD) were prepared with 1 and 2% nBGs by weight; unmodified BD and GC Fuji IX (GIC, GC Corporation, Tokyo, Japan) were used as references. The in vitro ability of the materials to induce apatite formation was assessed in SBF by X-ray diffraction (XRD), attenuated total reflectance with Fourier transform infrared spectroscopy (ATR-FTIR), and scanning electron microscopy (SEM) with energy dispersive X-ray (EDX) analysis. BD and nBG/BD were also applied to dentine discs for seven days; the morphology and elemental composition of the dentine-cement interface were analysed using SEM-EDX.One and two percent nBG/BD composites accelerated apatite formation on the disc surface after short-term immersion in SBF. Apatite was detected on the nBG/BD nanocomposites after three days, compared with seven days for unmodified BD. No apatite formation was detected on the GIC surface. nBG/BD formed a wider interfacial area with dentine than BD, showing blockage of dentine tubules and Si incorporation, suggesting intratubular precipitation.The incorporation of nBGs into BD improves its in vitro bioactivity, accelerating the formation of a crystalline apatite layer on its surface after immersion in SBF. Compared with unmodified BD, nBG/BD showed a wider interfacial area with greater Si incorporation and intratubular precipitation of deposits when immersed in SBF.