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The preparation of CdTe nanoparticles and CdTe nanoparticle-labelled microspheres for biological applications.

Different sizes of CdTe semiconductor nanoparticles were prepared in aqueous solution. These nanoparticles exhibit narrow fluorescence with full width at half-maximum (FWHM) of 35-45 nm that spans the visible spectrum, and they also have high PL quantum yield with high resistance to photodegradation. In addition, CdTe quantum dot (QD)-labelled microspheres, comprising polystyrene (PS) cores and CdTe/polyelectrolyte (PE) shells, were also prepared by the layer-by-layer technique in this paper. The optical properties of the CdTe nanoparticles and CdTe-labelled microspheres were investigated by UV-Visible absorption and luminescence spectroscopy, and fluorescence microscopy was employed for microscopic identification behaviour of the luminescent microspheres.

Animals↗
PubMed2002

Microbial synthesis of semiconductor CdS nanoparticles, their characterization, and their use in the fabrication of an ideal diode.

Cadmium sulfide nanoparticles were synthesized intracellularly by a Schizosaccharomyces pombe strain when challenged with 1 mM cadmium in solution. The nanoparticles, a known semiconducting material, exhibited an absorbance maximum at 305 nm. X-ray scattering data showed that the nanoparticles had a Wurtzite (Cd(16)S(20))-type hexagonal lattice structure and most of the nanoparicles were in the size range of 1-1.5 nm. The nanoparticles were used in the fabrication of a heterojunction with poly (p-phenylenevinylene). The diode exhibited approximately 75 mA/cm(2) current at 10 V when forward biased and the breakdown occurred at approximately 15 V in the reverse biased mode. These characteristics are considered ideal for a diode.

Cadmium Compounds↗
PubMed2005

A new two-phase route to high-quality CdS nanocrystals.

A new two-phase route has been developed to synthesize high-quality CdS nanocrystals with a narrow size distribution and a high photoluminescence (PL) quantum yield (QY). In the two-phase system, toluene and water were used as separate solvents for cadmium myristate (CdM2) and thiourea, which served as cadmium source and sulfur source, respectively, and oleic acid (OA) was used as a ligand for stabilizing the nanocrystals. The reactions were completed in the heated autoclaves. The initial Cd/S molar ratio of the precursors and the reaction temperature were found to be factors that affected the growth of nanocrystals. Furthermore, a seeding-growth technique was developed to synthesize CdS nanocrystals of different sizes, which exhibit PL peaks with quite similar full width at half-maximum (FWHM) values compared to those of the initial nanocrystal seeds in all cases.

Cadmium↗
PubMed2007

Shape-controlled synthesis of 3D and 1D structures of CdS in a binary solution with L-cysteine's assistance.

A facile L-cysteine-assisted route was designed for the selectively controlled synthesis of 1D and novel, interesting 3D CdS spherical nanostructures constructed from CdS nanorods (or nanopolypods) in a binary solution. By controlling reaction conditions such as the molar ratio between Cd(OAc)2 and L-cysteine and the volume ratio of the mixed solvents, the synthesis of various 3D architectural structures and 1D wirelike structures in large quantities can be controlled. This is the first reported case of the direct growth of novel 3D self-assemblies of CdS nanorods (or nanopolypods). The morphology, structure, and phase composition of the as-prepared CdS products were examined by using various techniques (X-ray diffraction (XRD), field-emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), selected-area electron diffraction (SAED), high-resolution TEM, and Raman spectroscopy). On the basis of the results from TEM studies and our analysis, we speculate that in the present synthesis the L-cysteine dominates nucleation growth and the ethylenediamine (en)-dominated, oriented-assembly process. Interestingly, the products obtained show a gradient evolution in color from light-yellow to dark-yellow, which implies that their intrinsic optical properties change, possibly due to variations in their special morphologies and structures. This facile solution-phase L-cysteine-assisted method could be extended for the controlled preparation of other metal chalcogenides nanostructures with complex morphologies.

Cadmium Compounds↗
PubMed2006

Highly efficient size separation of CdTe quantum dots by capillary gel electrophoresis using polymer solution as sieving medium.

In this paper, we present a new method for highly efficient size separation of water-soluble CdTe quantum dots (QDs) based on CGE using polymer solution as sieving medium. CdTe QDs were synthesized in aqueous phase by a chemical route with mercaptopropionic acid as a ligand. In the alkaline solution, CdTe QDs possess negative charges and migrate to the anode in the electric field. In linear polyacrylamide sieving medium, the migration time of CdTe QDs was increased with the size of CdTe QDs. The effects of some factors, such as types, concentrations, and pH of sieving media, on the separation of CdTe QDs were investigated systematically. Highly efficient separation of CdTe QDs was obtained in linear polyacrylamide sieving medium, and collection of fractions was automatically accomplished by CGE technique. Our preliminary results show that CGE technique is an efficient tool for characterization and size-dependent separation of water-soluble nanoparticles. In addition, the fraction collection in CGE may be useful in certain special applications such as fabrication of nanodevices in the future.

Acrylic Resins↗
PubMed1994

Studies on cytotoxic and genotoxic effects of cadmium nitrate and lead nitrate in Chinese hamster ovary cells.

Cadmium nitrate decreased the viability of Chinese hamster ovary (CHO) cells in a concentration-dependent manner; 50% inhibition (IC50) was achieved at 0.015 mM. In contrast, lead nitrate appeared to be less toxic. Neither cadmium nitrate nor lead nitrate significantly increased frequencies of binucleated CHO cells with micronuclei (MN). However, both cadmium nitrate and lead nitrate could augment sister chromatid exchanges (SCEs). Cadmium nitrate induced SCEs with a potency approximately equal to that of mitomycin C and more than 10 times higher than lead nitrate. Cadmium nitrate also increased chromosome aberrations (CAs), which included breaks, acentrics, interchanges, and dicentrics of chromosomes. In addition, cadmium nitrate induced a decrease in the mitotic index (MI), but lead nitrate increased it. In summary, it appears that both of these two heavy metal salts have cytogenetic toxicities with different degrees of effects on the cytotoxicity, MN, CAs, and SCEs in CHO cells. However, SCE was the most sensitive endpoint for indicating mutagenetic effects of cadmium and lead in the present study.

Animals↗
PubMed1994

Comparative investigations of the genotoxic effects of metals in the single cells gel (SCG) assay and the sister chromatid exchange (SCE) test.

Sodium arsenite (NaAsO2) and cadmium sulphate (CdSO4) were tested for their ability to induce genotoxic effects in the single cell gel (SCG) assay and the sister chromatid exchange (SCE) test in human blood cultures in vitro. Both metals induced DNA damage in white blood cells that was expressed and detected as DNA migration in the SCG assay. Dose dependent effects were seen for cadmium in concentrations from 5 x 10(-4)-5 x 10(-3) M and for arsenic in concentrations from 2 x 10(-4)-1.5 x 10(-3) M. The distribution of DNA migration among cells, a function of dose, revealed that the majority of exposed cells expressed more DNA damage than cells from control cultures and that with increasing length of DNA migration the variability in migration among cells increased as well. Treatment of cells for 2 hr or 24 hr beginning 48 hr after the start of the blood cultures did not increase the SCE frequency in the case of cadmium but caused a small but significant SCE induction with arsenic at the highest concentration. The metal concentrations which could be investigated in the SCE test were much lower due to a strong toxic effect. Metal concentrations which were toxic in the SCE test were without visible effect in the SCG assay. Thus the two endpoints for the determination of genotoxic effects in vitro differed markedly with respect to the detection of genotoxicity induced by metals. These differences and the biological significance of the findings are discussed.

Arsenites↗
PubMed2006

Intracellular uptake of CdSe-ZnS/polystyrene nanobeads.

The ideal optical properties of quantum dots (QDs) offer the possibility of using them as fluorescent probes in biological staining and diagnostics. Some techniques have been developed to incorporate QDs into polymer beads, to solve the problems relating to QDs' surface chemistry, such as water solubility, biocompatibility, chemical stability in physiological media, and so on, or to pack different combinations of QDs and produce QD encoded polymer beads. However, the QD encoded polymer beads that have been reported so far are above 100 nm; therefore they are very useful for multiplexed bioassays, but not suitable for staining or labeling of subcellular components or intracellular measurements because of the relatively big size of the beads. There is great need for QD encoded polymer beads smaller than 100 nm. In this work, luminescent CdSe-ZnS QDs were incorporated into polystyrene (PS) beads grafted with carboxyl groups with the use of an emulsion polymerization method, and separation of nanoscale QD encoded PS beads (30 nm) was performed through centrifugation at high speed in viscous solution. The nanobeads were further surface modified with folic acid and their intracellular delivery into NIH-3T3 and HT-29 cell lines was investigated with the use of confocal microscope. The longevity of QDs allows the intracellular delivery of the nanobeads to be tracked over a certain time period.

Animals↗
PubMed2006

The internalized CdSe/ZnS quantum dots impair the chondrogenesis of bone marrow mesenchymal stem cells.

Mesenchymal stem cells (MSCs) are capable of differentiating into multiple cell lineages and are useful for therapeutic applications. Labeling the MSCs with fluorescent probes is beneficial in tracing the fate of MSCs after implantation. We have introduced the CdSe/ZnS quantum dots (QDs) into the human bone marrow MSCs and examined the effects of QDs on the proliferation and chondrogenesis of the cells. The internalized QDs were found localized in perinuclear regions and remained there after a number of cell passages. The presence of QDs did not affect the proliferation of cells or the size of chondrospheres formed, when subjected to chondrogenesis induction. However, the expression of mRNA and protein of type II collagen and aggrecan in the chondrospheres was significantly inhibited in cells labeled with QDs, suggesting impaired chondrogenesis. Our results that the presence of QDs interferes with the chondrogenic differentiation of MSCs raise concerns in using the QDs as fluorescence tracers for stem cells.

Biocompatible Materials↗
PubMed1988

Exposure to different forms of cadmium in mice: differences in metallothionein and alphafetoprotein mRNA induction in liver and kidney.

Cadmium (Cd) exposure in mice induces transcription of metallothionein (MT) mRNA and protein accumulation in both liver and kidney. Resistance to hepatotoxicity through chronic exposure to heavy metals is the result of this induction. However, the same chronic exposure results in damage to kidney. We report here that acute exposure of mice to Cd as cadmium sulfate (CdSO4), which resulted in preferential accumulation of metal in liver, or Cd-metallothionein (CdMT), which resulted in preferential metal accumulation in kidney, induced MT mRNA accumulation in both liver and kidney. However, MT mRNA accumulated to a level twofold higher in liver than in kidney in response to CdSO4. Equivalent doses of CdMT induced MT mRNA accumulation to an equal degree in kidney and liver. While MT mRNA accumulation in kidney was directly proportional to the amount of cadmium in the organ, this was not the case in liver. There, liver MT mRNA was elevated in the absence of elevated tissue cadmium levels. Interestingly, CdMT induced alphafetal protein (AFP) mRNA accumulation in kidney, but not liver. It appears that (a) maximal MT mRNA accumulation in kidney is less than in liver, and (b) liver is capable of accumulating MT mRNA in response to even very low cadmium exposure that may not result in elevated tissue cadmium.

Animals↗