The Application of Ultrasmall Gold Nanoparticles (2 nm) Functionalized with Doxorubicin in Three-Dimensional Normal and Glioblastoma Organoid Models of the Blood-Brain Barrier.

Among brain tumors, glioblastoma (GBM) is very challenging to treat as chemotherapeutic drugs can only penetrate the brain to a limited extent due to the blood-brain barrier (BBB). Nanoparticles can be an attractive solution for the treatment of GBM as they can transport drugs across the BBB into the tumor. In this study, normal and GBM organoids comprising six brain cell types were developed and applied to study the uptake, BBB penetration, distribution, and efficacy of fluorescent, ultrasmall gold nanoparticles (AuTio-Dox-AF647s) conjugated with doxorubicin (Dox) and AlexaFluor-647-cadaverine (AF647) by confocal laser scanning microscopy (CLSM), using a mixture of dissolved doxorubicin and fluorescent AF647 molecules as a control. It was shown that the nanoparticles could easily penetrate the BBB and were found in normal and GBM organoids, while the dissolved Dox and AF647 molecules alone were unable to penetrate the BBB. Flow cytometry showed a reduction in glioblastoma cells after treatment with AuTio-Dox nanoparticles, as well as a higher uptake of these nanoparticles by GBM cells in the GBM model compared to astrocytes in the normal cell organoids. In summary, our results show that ultrasmall gold nanoparticles can serve as suitable carriers for the delivery of drugs into organoids to study BBB function.

Ultrastructure and Surface Composition of Glutathione-Terminated Ultrasmall Silver, Gold, Platinum, and Alloyed Silver-Platinum Nanoparticles (2 nm).

Alloyed ultrasmall silver-platinum nanoparticles (molar ratio Ag:Pt = 50:50) were prepared and compared to pure silver, platinum, and gold nanoparticles, all with a metallic core diameter of 2 nm. They were surface-stabilized by a layer of glutathione (GSH). A comprehensive characterization by high-resolution transmission electron microscopy (HRTEM), electron diffraction (ED), X-ray diffraction (XRD), small-angle X-ray scattering (SAXS), differential centrifugal sedimentation (DCS), and UV spectroscopy showed their size both in the dry and in the water-dispersed state (hydrodynamic diameter). Solution NMR spectroscopy (1H, 13C, COSY, HSQC, HMBC, and DOSY) showed the nature of the glutathione shell including the number of GSH ligands on each nanoparticle (about 200 with a molecular footprint of 0.063 nm2 each). It furthermore showed that there are at least two different positions for the GSH ligand on the gold nanoparticle surface. Platinum strongly reduced the resolution of the NMR spectra compared to silver and gold, also in the alloyed nanoparticles. X-ray photoelectron spectroscopy (XPS) showed that silver, platinum, and silver-platinum particles were at least partially oxidized to Ag(+I) and Pt(+II), whereas the gold nanoparticles showed no sign of oxidation. Platinum and gold nanoparticles were well crystalline but twinned (fcc lattice) despite the small particle size. Silver was crystalline in electron diffraction but not in X-ray diffraction. Alloyed silver-platinum nanoparticles were almost fully amorphous by both methods, indicating a considerable internal disorder.

Water-Based Synthesis of Ultrasmall Nanoparticles of Platinum Group Metal Oxides (1.8 nm).

Ultrasmall nanoparticles of platinum group metal oxides (core diameter of about 1.8 nm) were prepared by alkaline hydrolysis of metal precursors in the presence of NaBH4 and by colloidal stabilization with tripeptide glutathione. We obtained water-dispersed nanoparticles of Rh2O3, PdO, RuO2, IrO2, Os/OsO2, and Pt/PtO. Their size was probed using high-resolution transmission electron microscopy, differential centrifugal sedimentation, small-angle X-ray scattering, and diffusion-ordered 1H NMR spectroscopy (1H DOSY). Their oxidation state was clearly determined using X-ray photoelectron spectroscopy, X-ray powder diffraction, and electron diffraction. The chemical composition of the nanoparticles, that is, the ratio of the metal oxide core and glutathione capping agent, was quantitatively determined by a combination of these methods.

Controlling the Surface Functionalization of Ultrasmall Gold Nanoparticles by Sequence-Defined Macromolecules.

Ultrasmall gold nanoparticles (diameter about 2 nm) were surface-functionalized with cysteine-carrying precision macromolecules. These consisted of sequence-defined oligo(amidoamine)s (OAAs) with either two or six cysteine molecules for binding to the gold surface and either with or without a PEG chain (3400 Da). They were characterized by 1 H NMR spectroscopy, 1 H NMR diffusion-ordered spectroscopy (DOSY), small-angle X-ray scattering (SAXS), and high-resolution transmission electron microscopy. The number of precision macromolecules per nanoparticle was determined after fluorescent labeling by UV spectroscopy and also by quantitative 1 H NMR spectroscopy. Each nanoparticle carried between 40 and 100 OAA ligands, depending on the number of cysteine units per OAA. The footprint of each ligand was about 0.074 nm2 per cysteine molecule. OAAs are well suited to stabilize ultrasmall gold nanoparticles by selective surface conjugation and can be used to selectively cover their surface. The presence of the PEG chain considerably increased the hydrodynamic diameter of both dissolved macromolecules and macromolecule-conjugated gold nanoparticles.

Synthesis and characterization of PLGA/HAP scaffolds with DNA-functionalised calcium phosphate nanoparticles for bone tissue engineering.

Porous scaffolds of poly(lactide-co-glycolide) (PLGA; 85:15) and nano-hydroxyapatite (nHAP) were prepared by an emulsion-precipitation procedure from uniform PLGA-nHAP spheres (150-250 µm diameter). These spheres were then thermally sintered at 83 °C to porous scaffolds that can serve for bone tissue engineering or for bone substitution. The base materials PLGA and nHAP and the PLGA-nHAP scaffolds were extensively characterized by X-ray powder diffraction, infrared spectroscopy, thermogravimetry, differential scanning calorimetry, and scanning electron microscopy. The scaffold porosity was about 50 vol% as determined by relating mass and volume of the scaffolds, together with the computed density of the solid phase (PLGA-nHAP). The cultivation of HeLa cells demonstrated their high cytocompatibility. In combination with DNA-loaded calcium phosphate nanoparticles, they showed a good activity of gene transfection with enhanced green fluorescent protein (EGFP) as model protein. This is expected enhance bone growth around an implanted scaffold or inside a scaffold for tissue engineering.

Deciphering the Surface Composition and the Internal Structure of Alloyed Silver-Gold Nanoparticles.

Spherical bimetallic AgAu nanoparticles in the molar ratios 30:70, 50:50, and 70:30 with diameters of 30 to 40 nm were analyzed together with pure silver and gold nanoparticles of the same size. Dynamic light scattering (DLS) and differential centrifugal sedimentation (DCS) were used for size determination. Cyclic voltammetry (CV) was used to determine the nanoalloy composition, together with atomic absorption spectroscopy (AAS), energy-dispersive X-ray spectroscopy (EDX) and ultraviolet-visible (UV/Vis) spectroscopy. Underpotential deposition (UPD) of lead (Pb) on the particle surface gave information about its spatial elemental distribution and surface area. Scanning electron microscopy (SEM), transmission electron microscopy (TEM), and atomic force microscopy (AFM) were applied to study the shape and the size of the nanoparticles. X-ray powder diffraction gave the crystallite size and the microstrain. The particles form a solid solution (alloy) with an enrichment of silver on the nanoparticle surface, including some silver-rich patches. UPD indicated that the surface only consists of silver atoms.

Peculiarities in thermal evolution of precipitated amorphous calcium phosphates with an initial Ca/P ratio of 1:1.

Thermal evolution of amorphous calcium phosphate (ACP) powder from a fast nitrate synthesis with a Ca/P ratio of 1:1 were studied in the range of 20-980 °C. The powder consisted of amorphous dicalcium phosphate anhydrate (CaHPO4) after heating to 200 °C. CaHPO4 gradually condensed to amorphous calcium pyrophosphate Ca2P2O7 (CPP) between 200 to 620 °C. Amorphous CPP crystallized at 620-740 °C to a metastable polymorph α'-CPP of the high-temperature phase α-CPP and ß-CPP. The α'-CPP/ ß-CPP phase ratio reached a maximum at 800 °C (60 wt% α'-CPP/40 wt% ß-CPP), and α'-CPP gradually transformed to ß-CPP at a higher temperature. Some ß-TCP occurred at 900 °C, so that a three-phasic mixture was obtained in the powder heated to 980 °C. The occurrence of metastable α'-CPP is attributed to Ostwald's step rule, and a mechanism for ß-TCP formation is proposed. The advantages of prospective biomaterials from these powders are discussed.

Plattenepithelkarzinom in Verbindung mit einer roten Tätowierung.

HINTERGRUND UND ZIELE: Obwohl Tätowierungen in den letzten Jahren außerordentlich beliebt geworden sind, wurde in der Literatur bisher nur über wenige Fälle schwerer Reaktionen berichtet, die zu einer malignen Transformation führten. Dies steht im Kontrast zu der praktisch unüberschaubaren Zahl an Tätowierungen weltweit. Die Zusammensetzung der für Tätowierungen verwendeten Farbstoffe variiert stark, und selbst gleiche Farbtöne können unterschiedliche Komponenten enthalten. Das Ziel unserer Studie war es zu untersuchen, auf welche Weise Tätowierungen möglicherweise Hautkrebs auslösen können. PATIENTEN UND METHODEN: Wir berichten über den seltenen Fall einer 24-jährigen Frau, bei der sich sieben Monate nachdem sie eine Tätowierung auf dem Fußrücken erhalten hatte in unmittelbarer Nähe des verwendeten roten Farbstoffs ein Plattenepithelkarzinom entwickelte. Die Komplikationen begannen mit einer unspezifischen Schwellung. Die Läsion wurde histologisch untersucht. Die Zusammensetzung des inkorporierten Farbstoffs wurde mittels Rasterelektronenmikroskopie in Kombination mit energiedispersiver Elementanalyse analysiert. Zur weiteren Charakterisierung wurden Thermogravimetrie und Pulverdiffraktometrie eingesetzt. ERGEBNISSE UND SCHLUSSFOLGERUNGEN: Der Tätowierungsfarbstoff enthielt hauptsächlich Bariumsulfat; Spuren von Al, S, Ti, P, Mg und Cl ließen sich ebenfalls nachweisen. Bei der Analyse zeigten sich Pigmentgranula unterschiedlicher Größe. In seltenen Fällen kann Tätowierungstinte karzinogene Effekte haben, die multifaktoriell zu sein scheinen.

Squamous cell carcinoma in association with a red tattoo.

BACKGROUND AND OBJECTIVES: Although tattoos have become exceedingly popular in recent years, only few cases of severe reactions leading to malignant transformation have been reported in the literature. This stands in contrast to the virtually innumerable number of tattoos worldwide. The composition of tattoo dyes is highly variable, and even the same colors may contain different compounds. The objective of our study was to investigate in what way tattoo dyes may potentially trigger skin cancer. PATIENT AND METHODS: We report the rare case of a 24-year-old woman who - seven months after getting a tattoo on the back of her foot - developed a squamous cell carcinoma in close proximity to the red dye used. Complications started in the form of nonspecific swelling. The lesion was histologically examined. The composition of the incorporated dye was analyzed using scanning electron microscopy in combination with energy dispersive element analysis. Thermogravimetry and powder diffraction were used for further characterization. RESULTS AND CONCLUSIONS: While the tattoo dye primarily consisted of barium sulfate, traces of Al, S, Ti, P, Mg, and Cl were also detected. The analysis showed pigment granules of varying sizes. In rare cases, tattoo inks may have carcinogenic effects, which appear to be multifactorial.

Integrated In Situ Fabrication of CuO Nanorod-Decorated Polymer Membranes for the Catalytic Flow-Through Reduction of p-Nitrophenol.

We developed a novel method to fabricate copper nanorods in situ in a poly(ether sulfone) (15 wt %) casting solution by a sonochemical reduction of Cu2+ ions with NaBH4. The main twist is the addition of ethanol to remove excess NaBH4 through Cu(0) catalyzed ethanolysis. This enabled the direct use of the resulting copper-containing casting dispersions for membrane preparation by liquid nonsolvent-induced phase separation and led to full utilization of the copper source, generating zero metal waste. We characterized the copper nanorods as presented in the membranes via scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), and UV/vis spectroscopy. We could demonstrate that the rapid immobilization from reducing conditions led to the membrane incorporation of copper nanorods in a state of high reactivity, which also promoted the complete oxidation to CuO after fabrication. We further observed a large aspect ratio and crystal straining of the nanorods, likely resulting from growth around the matrix polymer. The entanglement with poly(ether sulfone) further facilitated a selective presentation at the pore surface of the final CuO-decorated membranes. The membranes also exhibit high water permeances of up to 2800 L/m2hbar. Our catalytic membranes achieved exceptionally high activities in the aqueous flow-through reduction of p-nitrophenol (p-NP), with turnover frequencies of up to 115 h-1, even surpassing those of other state-of-the-art catalytic membranes that incorporate Pd or Ag. Additionally, we demonstrated that catalytic hydrolysis of the reducing agent in water can lead to hydrogen gas formation and blocking of active sites during continuous catalytic p-NP hydrogenation. We illustrated that the accompanying conversion loss can be mitigated by facilitated gas transport in the water-filled pores, which is dependent on the orientation of the pore size gradient and the flow direction.

Development of triple-functionalized calcium phosphate nanoparticles as an advanced drug delivery system for bone tissue repair.

Introduction: During tissue repair or regeneration, several bioactive molecules are released and interact with each other and act as complex additives or inhibitors for tissue reconstruction. In this study, the bone-healing effects of the combination treatment with tumor necrosis factor-α (TNF-α) inhibition, vascular endothelial growth factor A (VEGF-A) and bone morphogenetic protein-7 (BMP-7) release by gene silencing, and gene transfection with calcium phosphate nanoparticles (CaP) in the rat femoral head was histologically, morphologically, and biochemically evaluated. Methods: A triple-functionalized paste of CaP carrying plasmid DNA encoding for BMP-7 and for VEGF), and siRNA against TNF-α was developed and denoted as CaP3mix. To compare the effects of 3mixCaP, CaP with plasmid DNA encoding BMP-7, VEGF, or siRNA encoding TNF-α was prepared and denoted as CaP/PEI/pBMP-7/SiO2, CaP/PEI/pVEGF/SiO2, or CaP/PEI/siRNA-TNF-α/SiO2, respectively. The bone healing in bone defects in the rat femoral head was investigated after 10 and 21 days of implantation. Results: The levels of bone formation-related markers OCN, Runx2, and SP7 increased at the protein and gene levels in 3mixCaP after 10 days, and 3mixCaP significantly accelerated bone healing compared with the other treatments after 21 days of implantation. Conclusion: The triple-functionalized CaP paste loading plasmid DNA encoding BMP-7 and VEGF and siRNA encoding TNF-α is a promising bioactive material for bone tissue repair.

The Molecular Footprint of Peptides on the Surface of Ultrasmall Gold Nanoparticles (2 nm) Is Governed by Steric Demand.

Ultrasmall gold nanoparticles were functionalized with peptides of two to seven amino acids that contained one cysteine molecule as anchor via a thiol-gold bond and a number of alanine residues as nonbinding amino acid. The cysteine was located either in the center of the molecule or at the end (C-terminus). For comparison, gold nanoparticles were also functionalized with cysteine alone. The particles were characterized by UV spectroscopy, differential centrifugal sedimentation (DCS), high-resolution transmission electron microscopy (HRTEM), and small-angle X-ray scattering (SAXS). This confirmed the uniform metal core (2 nm diameter). The hydrodynamic diameter was probed by 1H-DOSY NMR spectroscopy and showed an increase in thickness of the hydrated peptide layer with increasing peptide size (up to 1.4 nm for heptapeptides; 0.20 nm per amino acid in the peptide). 1H NMR spectroscopy of water-dispersed nanoparticles showed the integrity of the peptides and the effect of the metal core on the peptide. Notably, the NMR signals were very broad near the metal surface and became increasingly narrow in a distance. In particular, the methyl groups of alanine can be used as probe for the resolution of the NMR spectra. The number of peptide ligands on each nanoparticle was determined using quantitative 1H NMR spectroscopy. It decreased with increasing peptide length from about 100 for a dipeptide to about 12 for a heptapeptide, resulting in an increase of the molecular footprint from about 0.1 to 1.1 nm2.

Characterization of crocodile teeth: correlation of composition, microstructure, and hardness.

Structure and composition of teeth of the saltwater crocodile Crocodylus porosus were characterized by several high-resolution analytical techniques. X-ray diffraction in combination with elemental analysis and infrared spectroscopy showed that the mineral phase of the teeth is a carbonated calcium-deficient nanocrystalline hydroxyapatite in all three tooth-constituting tissues: Dentin, enamel, and cementum. The fluoride content in the three tissues is very low (<0.1 wt.%) and comparable to that in human teeth. The mineral content of dentin, enamel, and cementum as determined by thermogravimetry is 71.3, 80.5, and 66.8 wt.%, respectively. Synchrotron X-ray microtomography showed the internal structure and allowed to visualize the degree of mineralization in dentin, enamel, and cementum. Virtual sections through the tooth and scanning electron micrographs showed that the enamel layer is comparably thin (100-200 µm). The crystallites in the enamel are oriented perpendicularly to the tooth surface. At the dentin-enamel-junction, the packing density of crystallites decreases, and the crystallites do not display an ordered structure as in the enamel. The microhardness was 0.60±0.05 GPa for dentin, 3.15±0.15 GPa for enamel, 0.26±0.08 GPa for cementum close to the crown, and 0.31±0.04 GPa for cementum close to the root margin. This can be explained with the different degree of mineralization of the different tissue types and is comparable with human teeth.

Solution-based synthesis of GeTe octahedra at low temperature.

GeTe octahedra were prepared by reaction of equimolar amounts of GeCl2·dioxane and Te(SiEt3)2 in oleylamine, whereas a slight excess of the Te precursor yielded GeTe octahedra decorated with elemental Te nanowires, which can be removed by washing with TOP. The mechanism of the GeTe formation is strongly influenced by the solvent. The expected elimination of Et3SiCl (dehalosilylation) only occurred in aprotic solvents, whereas Te(SiEt3)2 was found to react with primary and secondary amines with formation of silylamines. Temperature-dependent studies on the reaction in oleylamine showed that crystalline GeTe particles are formed at temperatures higher than 140 °C. XRD, SAED, and HRTEM studies proved the formation of rhombohedral GeTe nanoparticles. These findings were confirmed by a single-crystal and powder X-ray analysis. The rhombohedral structure modification was found, and the structure was solved in the acentric space group R3m.

Cell-Biological Response and Sub-Toxic Inflammatory Effects of Titanium Dioxide Particles with Defined Polymorphic Phase, Size, and Shape.

Six types of titanium dioxide particles with defined size, shape, and crystal structure (polymorphic form) were prepared: nanorods (70 × 25 nm2), rutile sub-microrods (190 × 40 nm2), rutile microspheres (620 nm), anatase nanospheres (100 nm), anatase microspheres (510 nm), and amorphous titania microspheres (620 nm). All particles were characterized by scanning electron microscopy, X-ray powder diffraction, dynamic light scattering, infrared spectroscopy, and UV spectroscopy. The sub-toxic cell-biological response to these particles by NR8383 macrophages was assessed. All particle types were taken up well by the cells. The cytotoxicity and the induction of reactive oxygen species (ROS) were negligible for all particles up to a dose of 100 µg mL-1, except for rutile microspheres which had a very rough surface in contrast to anatase and amorphous titania microspheres. The particle-induced cell migration assay (PICMA; based on chemotaxis) of all titanium dioxide particles was comparable to the effect of control silica nanoparticles (50 nm, uncoated, agglomerated) but did not show a trend with respect to particle size, shape, or crystal structure. The coating with carboxymethylcellulose (CMC) had no significant biological effect. However, the rough surface of rutile microspheres clearly induced pro-inflammatory cell reactions that were not predictable by the primary particle size alone.

Structure, composition, and mechanical properties of shark teeth.

The teeth of two different shark species (Isurus oxyrinchus and Galeocerdo cuvier) and a geological fluoroapatite single crystal were structurally and chemically characterized. In contrast to dentin, enameloid showed sharp diffraction peaks which indicated a high crystallinity of the enameloid. The lattice parameters of enameloid were close to those of the geological fluoroapatite single crystal. The inorganic part of shark teeth consisted of fluoroapatite with a fluoride content in the enameloid of 3.1 wt.%, i.e., close to the fluoride content of the geological fluoroapatite single crystal (3.64 wt.%). Scanning electron micrographs showed that the crystals in enameloid were highly ordered with a special topological orientation (perpendicular towards the outside surface and parallel towards the center). By thermogravimetry, water, organic matrix, and biomineral in dentin and enameloid of both shark species were determined. Dentin had a higher content of water, organic matrix, and carbonate than enameloid but contained less fluoride. Nanoindentation and Vicker's microhardness tests showed that the enameloid of the shark teeth was approximately six times harder than the dentin. The hardness of shark teeth and human teeth was comparable, both for dentin and enamel/enameloid. In contrast, the geological fluoroapatite single crystal was much harder than both kinds of teeth due to the absence of an organic matrix. In summary, the different biological functions of the shark teeth ("tearing" for Isurus and "cutting" for Galeocerdo) are controlled by the different geometry and not by the chemical or crystallographic composition.

Tuning the Fluorescence in Dynamic Covalent Bonded Liquid Crystals.

A series of emissive liquid crystalline materials based on salicylidene derivatives is reported and investigated with respect to their thermoresponsive and mechanochromic properties. Single-crystal analysis and temperature-dependent powder X-ray diffraction measurements allowed us to correlate the intermolecular organization of the mesogens with thermoresponsive changes in the fluorescence behavior. As a proof-of-principle study, we employed the dynamics of the imine bond in transamination reactions for postsynthetic tuning of the fluorescence behavior as a further step toward the development of adaptive materials.

Colloidal stability, cytotoxicity, and cellular uptake of HfO2 nanoparticles.

The colloidal stability, cytotoxicity, and cellular uptake of hafnium oxide (HfO2 ) nanoparticles (NPs) were investigated in vitro to assess safety and efficacy for use as a deliverable theranostic in nanomedicine. Monoclinic HfO2 NPs, ~60-90 nm in diameter and ellipsoidal in shape, were directly prepared without calcination by a hydrothermal synthesis at 83% yield. The as-prepared, bare HfO2 NPs exhibited colloidal stability in cell culture media for at least 10 days without significant agglomeration or settling. The viability (live/dead assay) of human epithelial cells (HeLa) and monocyte-derived macrophages (THP-1) did not fall below 95% of untreated cells after up to 24 h exposure to HfO2 NPs at concentrations up to 0.80 mg/ml. Similarly, the mitochondrial activity (MTT assay) of HeLa and THP-1 cells did not fall below 80% of untreated cells after up to 24 h exposure to HfO2 NPs at concentrations up to 0.40 mg/ml. Cellular uptake was confirmed and visualized in both HeLa and THP-1 cells by fluorescence microscopy of HfO2 NPs labeled with Cy5 and transmission electron microscopy (TEM) of bare HfO2 NPs. TEM micrographs provided direct observation of macropinocytosis and endosomal compartmentalization within 4 h of exposure. Thus, the HfO2 NPs in this study exhibited colloidal stability, cytocompatibility, and cellular uptake for potential use as a deliverable theranostic in nanomedicine.

Porous Zirconia/Magnesia Ceramics Support Osteogenic Potential In Vitro.

Porous zirconia (ZrO2), magnesia (MgO) and zirconia/magnesia (ZrO2/MgO) ceramics were synthesised by sintering and designated as ZrO2(100), ZrO2(75)MgO(25), ZrO2(50)MgO(50), ZrO2(25)MgO(75), MgO(100) based on their composition. The ceramic samples were characterised by means of scanning electron microscopy, X-ray diffraction, energy-dispersive X-ray spectroscopy and atomic absorption spectrometry to explore the incorporation of Mg atoms into the zirconia lattice. The resulting porosity of the samples was calculated based on the composition and density. The final porosity of the cylinder-shaped ceramic samples ranged between 30 and 37%. The mechanical analysis exhibited that the Young modulus increased and the microstress decreased with increasing magnesia amount, with values ranging from 175 GPa for zirconia to 301 GPa for magnesia. The adhesion, viability, proliferation and osteogenic activity of MC3T3-E1 pre-osteoblastic cells cultured on the zirconia/magnesia ceramics was found to increase, with the magnesia-containing ceramics exhibiting higher values of calcium mineralisation. The results from the mechanical analysis, the ALP activity, the calcium and collagen production demonstrate that the zirconia/magnesia ceramics possess robust osteoinductive capacity, therefore holding great potential for bone tissue engineering.

The effect of short silica fibers (0.3 µm 3.2 µm) on macrophages.

Silica fibers with a dimension of 0.3 µm ∙ 3.2 µm2 nm were prepared by a modified Stöber synthesis as model particles. The particles were characterized by scanning electron microscopy, elemental analysis, thermogravimetry and X-ray powder diffraction. Their uptake by macrophages (THP-1 cells and NR8383 cells) was studied by confocal laser scanning microscopy and scanning electron microscopy. The uptake by cells was very high, but the silica fibers were not harmful to NR8383 cells in concentrations up to 100 µg mL-1. Only above 100 µg mL-1, significant cell toxic effects were observed, probably induced by a high dose of particles that had sedimented on the cells and led to the adverse effects. The chemotactic response as assessed by the particle-induced migration assay (PICMA) was weak in comparison to a control of agglomerated silica particles. The as-prepared fibers were fully X-ray amorphous but crystallized to ß-cristobalite after heating to 1000 °C and converted to α-cristobalite upon cooling to ambient temperature. The fibers had sintered to larger aggregates but retained their elongated primary shape. The particle cytotoxicity towards THP-1 cells was not significantly enhanced by the crystallization.