CdTe nanocrystals capped with 1-mercapto-2,3-propandiol, CdSe nanocrystals capped with sodium citrate, and core-shell CdSe/CdS nanocrystals capped with sodium citrate were synthesized in aqueous solutions, and their surface was modified by 3-mercaptopropyltrimethoxysilane (MPS) in water-ethanol mixtures. By addition of sodium silicate, "raisin bun"-type composite particles were formed, with either CdTe, CdSe, or CdSe/CdS nanocrystals being homogeneously incorporated as multiple cores into silica spheres of 40-80 nm size, accompanied by some alteration of optical properties of the nanoparticles and, in particular, the reduction of the luminescence quantum yield. Further, growth of larger silica spheres (100-700 nm) can be performed by the Sto ¨ber technique using either MPS-modified semiconductor nanocrystals or "raisin bun"-type composite particles as seeds, which gives semiconductor-doped silica globules of desirable sizes in the submicrometer range. The composite spheres can be used as building blocks for 3D colloidal crystals, prepared in this study for CdS/CdSe-doped 250 nm silica colloid. The shift of the photonic band gap to the red was observed in photonic crystals made of nanoparticles-doped silica due to the high refractive index of the semiconductors.

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Stable aqueous colloids of 2-3 nm In 2 S 3 nanocrystals have been prepared by using the classical method of nanoparticle stabilization by low molecular weight thiols. TEM crystal lattice spacing, X-ray diffraction, EDAX data, and electron diffraction indicate that the nanoparticles are predominantly in -In 2 S 3 form. They exhibit relatively strong excitonic emission at 360-380 nm with a quantum yield of 1.5%. The excitonic radiative lifetime is 350 ns, which indicates that a direct allowed electronic transition is responsible for this emission. The NMR lines of the stabilizer are strongly broadened and shifted as a result of deshielding induced by electron withdrawing by positively charged metal ions. This effect quickly wears off as the carbon chain becomes longer and the separation between the hydrogen atoms of the stabilizer and the semiconductor surface increases. The broadening is attributed to the reduced mobility of the stabilizer in the nanoparticle shell. For CdS nanoparticles of the same size, this effect was found to be substantially stronger than for In 2 S 3 . The lower density of metal centers in In 2 S 3 than in CdS, which serve as anchor points for the stabilizer, promotes greater mobility of the stabilizer moieties.

BackgroundPotential routes of nanomaterial exposure include inhalation, dermal contact, and ingestion. Toxicology of inhalation of ultra-fine particles has been extensively studied; however, risks of nanomaterial exposure via ingestion are currently almost unknown. Using enterocyte-like Caco-2 cells as a small intestine epithelial model, the possible toxicity of CdSe quantum dot (QD) exposure via ingestion was investigated. Effect of simulated gastric fluid treatment on CdSe QD cytotoxicity was also studied.ResultsCommercially available CdSe QDs, which have a ZnS shell and poly-ethylene glycol (PEG) coating, and in-house prepared surfactant coated CdSe QDs were dosed to Caco-2 cells. Cell viability and attachment were studied after 24 hours of incubation. It was found that cytotoxicity of CdSe QDs was modulated by surface coating, as PEG coated CdSe QDs had less of an effect on Caco-2 cell viability and attachment. Acid treatment increased the toxicity of PEG coated QDs, most likely due to damage or removal of the surface coating and exposure of CdSe core material. Incubation with un-dialyzed in-house prepared CdSe QD preparations, which contained an excess amount of free Cd2+, resulted in dramatically reduced cell viability.ConclusionExposure to CdSe QDs resulted in cultured intestinal cell detachment and death; cytotoxicity depended largely, however, on the QD coating and treatment (e.g. acid treatment, dialysis). Experimental results generally indicated that Caco-2 cell viability correlated with concentration of free Cd2+ ions present in cell culture medium. Exposure to low (gastric) pH affected cytotoxicity of CdSe QDs, indicating that route of exposure may be an important factor in QD cytotoxicity.

This work describes the formation of porous composite materials based on a combination of bioactive mesoporous silicon and bioerodible polymers such as poly-caprolactone (PCL). The fabrication of a range of composites prepared by both salt leaching and microemulsion techniques are discussed. Particular attention to the influence of Si content in the composite on in vitro calcification assays are assessed. For each system, cytotoxicity and cellular proliferation are explicitly evaluated through fibroblast cell culture assays.

Improvements in osteoconduction of implant biomaterials require focusing on the bone-implant interface, which is a complex multifactorial system. Surface topography of implants plays a crucial role at this interface. Nanostructured surfaces have been shown to promote serum protein adsorption and osteoblast adhesion when compared to microstructured surfaces for bone-implant materials. We studied the influence of the serum proteins fibronectin and vitronectin on the attachment and proliferation of osteoblasts onto nanostructured titania surfaces. Human fetal osteoblastic cells hFOB 1.19 were used as model osteoblasts and were grown on nanoporous TiO2 templates, using Ti6Al4V and commercially pure Ti substrates as controls. Results show a significant increase in cell proliferation on nanoporous TiO2 over flat substrates. Initial cell attachment data exhibited a significant effect by either fibronectin or vitronectin on cell adhesion at the surface of any of the tested materials. In addition, the extent of cell adhesion was significantly different between the nanoporous TiO2 and both Ti6Al4V and commercially pure Ti substrates, with the first showing the highest surface coverage. There was no significant difference on osteoblast attachment or proliferation between the presence of fibronectin or vitronectin using any of the material substrates. Taken together, these results suggest that the increase in osteoblast attachment and proliferation shown on the nanoporous TiO2 is due to an increase in the adsorption of fibronectin and vitronectin because of the higher surface area and to an enhanced protein unfolding, which allows access to osteoblast binding motifs within these proteins.

ExperimentalGlassy solid electrolytes in the Li 2 S±P 2 S 5 system were prepared by the mechanical milling technique [13]. Highly pure Li 2 S (Idemitsu Kosan Co., > 99.9 %) and reagent-grade P 2 S 5 (Aldrich, 99 %) crystalline powders were used as starting materials to prepare the 70Li 2 S´30P 2 S 5 (70 mol-% Li 2 S, 30 mol-% P 2 S 5 ) samples. The mixture of these materials was mechanically milled at room temperature by a planetary ball-mill apparatus (Fritsch Pulverisette 7) using an alumina pot (volume of 45 mL) with ten alumina balls (10 mm in diameter); the milling time was 20 h and the rotation speed was 370 rpm. All the processes were performed in a dry, Ar-filled glove box (less than 1 ppm water). Glass-ceramic solid electrolytes were prepared by crystallization of the mechanically milled glass at 240 C for 2 h. Crystalline solid electrolytes with the same composition were prepared by a conventional solid-state reaction in which a mixture of Li 2 S and P 2 S 5 was put into a carbon-coated quartz tube and sealed under vacuum. The tube was heated at 700 C for 8 h, and then slowly cooled to room temperature.Electrical conductivities of pellets obtained by cold pressing the sample under a pressure of 3700 kg cm ±2 were measured; the diameters and thicknesses of the pellets were 10 mm and about 1 mm, respectively. A carbon paste was painted onto both sides of the sample and carbon electrodes were formed after heat treatment. Alternating current (AC) impedance measurements were carried out in a dry argon atmosphere using an impedance analyzer (SI1260, Solartron) in the frequency range of 10 Hz to 8 MHz. The temperature of the measurements ranged from 25 to 240 C. X-ray diffraction (XRD) measurements (Cu Ka) were performed using a diffractometer (M18XHF 22-SRA, MAC Science) to identify crystals in the glass-ceramics. Local structures of the samples were analyzed by Raman spectroscopy using a spectrometer (NR-1000, JASCO) equipped with an Ar + laser (514.5 nm).

CdS nanoparticles (NP), 22 Å, have been synthesized from cadmium 2-ethylhexanoate in DMSO as a uniformly sized dispersion. After ripening, CdS exhibits a sharp excitonic emission peak at 402 nm, while in freshly prepared dispersions a broad trapped emission at 510 nm dominates. By using one-and two-dimensional NMR spectroscopy, the conformation of the stabilizer adsorbed to the NP has been determined. The long hexyl chain of 2-ethylhexanoate ions spreads over the surface of NP, whereas the short ethyl end is primarily surrounded by DMSO. Surface modification of CdS with nucleophiles such as 4,4-bipyridine, thiophene, trimethylamine, and thiomolybdate anion results in a partial replacement of the stabilizer and reorientation of the hexyl chain away from the surface. The difference in the degree of replacement and/or conformational changes of 2-ethylhexanoate ion depends on the electron donor activity of the modifier.