tellurium and 2-thiomalic-acid

Topics: Aminoglycosides; Anti-Bacterial Agents; Cadmium Compounds; Fluorescence; Fluorescent Dyes; Humans; Quantum Dots; Spectrometry, Fluorescence; Tellurium

The water-soluble semiconductor quantum dots (QDs) serve as optically detectable models of nanoparticles and are commonly applied as photoluminescent markers in biological systems. The unicellular algae represent a popular model system suitable to evaluate pollution-induced effects. There is growing experimental evidence that release of metal ions cannot account for potential toxicity of metal containing nanoparticles, however, the underlying mechanisms are not clearly understood. Surrounding environment and illumination conditions are among the most important factors affecting the stability of QDs as well as the interaction between nanoparticles and cells such as microalgae. The measurements of changes in photoluminescence (PL) of QDs and autofluorescence (AF) of microalgae can thus be used as a non-invasive screening method for detecting mutual effects of nanoparticles and algae cells on each other under natural conditions. In this study, CdTe quantum dots (a peak of PL at 550 nm) capped with a mercaptosuccinic acid (MSA) were introduced into aqueous ionic medium containing wild type green freshwater microalgae Scenedesmus and Chlorella sp. cells under artificial and natural ambient illumination. The spectroscopy and microscopy techniques were applied to observe both the influence of the microalgae on the spectral properties of negatively charged CdTe-MSA quantum dots and the effects of nanoparticles on the microalgae. The presence of algae cells revealed a protecting effect on both medium-dependent and radiation-induced changes in photoluminescence properties of QDs, which could be related with the increased stability of the capping layer. The effects on cellular AF intensity and the interaction of QDs with cellular surface depended on type of microalgae. The observed changes in AF spectral properties and AF induction signals can't be explained only by the photodegradation of QDs and have revealed the ability of nanoparticles to retard the photoadaptation of wild type microalgae under naturally varying illumination conditions.

Topics: Cadmium Compounds; Chlorella; Fluorescent Dyes; Fresh Water; Light; Microalgae; Quantum Dots; Scenedesmus; Spectrometry, Fluorescence; Surface Properties; Tellurium; Thiomalates

Cadmium telluride quantum dots (CdTe QDs) have been proposed to induce oxidative stress, which plays a crucial role in CdTe QDs-mediated mitochondrial-dependent apoptosis in human umbilical vein endothelial cells (HUVECs). However, the direct interactions of CdTe QDs with HUVECs and their potential impairment of other organelles like endoplasmic reticulum (ER) in HUVECs are poorly understood. In this study, we reported that the negatively charged CdTe QDs (-21.63±0.91 mV), with good dispersity and fluorescence stability, were rapidly internalized via endocytosis by HUVECs, as the notable internalization could be inhibited up to 95.52% by energy depletion (NaN3/deoxyglucose or low temperature). The endocytosis inhibitors (methyl-β-cyclodextrin, genistein, sucrose, chlorpromazine, and colchicine) dramatically decreased the uptake of CdTe QDs by HUVECs, suggesting that both caveolae/raft- and clathrin-mediated endocytosis were involved in the endothelial uptake of CdTe QDs. Using immunocytochemistry, a striking overlap of the internalized CdTe QDs and ER marker was observed, which indicates that QDs may be transported to ER. The CdTe QDs also caused remarkable ER stress responses in HUVECs, confirmed by significant dilatation of ER cisternae, upregulation of ER stress markers GRP78/GRP94, and activation of protein kinase RNA-like ER kinase-eIF2α-activating transcription factor 4 pathway (including phosphorylation of both protein kinase RNA-like ER kinase and eIF2α and elevated level of activating transcription factor 4). CdTe QDs further promoted an increased C/EBP homologous protein expression, phosphorylation of c-JUN NH2-terminal kinase, and cleavage of ER-resident caspase-4, while the specific inhibitor (SP600125, Z-LEVD-fmk, or salubrinal) significantly attenuated QDs-triggered apoptosis, indicating that all three ER stress-mediated apoptosis pathways were activated and the direct participation of ER in the CdTe QDs-caused apoptotic cell death in HUVECs. Our findings provide important new insights into QDs toxicity and reveal potential cardiovascular risks for the future applications of QDs.

Topics: Apoptosis; beta-Cyclodextrins; Cadmium Compounds; Colchicine; eIF-2 Kinase; Endocytosis; Endoplasmic Reticulum Chaperone BiP; Endoplasmic Reticulum Stress; Fluorescence; Genistein; Heat-Shock Proteins; Human Umbilical Vein Endothelial Cells; Humans; Quantum Dots; Tellurium; Thiomalates

Semiconductor colloidal quantum dots (QDs) have been applied in biological analysis due to their unique optical properties and their versatility to be conjugated to biomolecules, such as lectins and antibodies, acquiring specificity to label a variety of targets. Concanavalin A (Con A) lectin binds specifically to α-d-mannose and α-d-glucose regions of saccharides that are usually expressed on membranes of mammalian cells and on cell walls of microbials. Candida albicans is the most common fungal opportunistic pathogen present in humans. Therefore, in this work, this fungus was chosen as a model for understanding cells and biofilm-forming organisms. Here, we report an efficient bioconjugation process to bind CdTe (Cadmium Telluride) QDs to Con A, and applied the bioconjugates to label saccharide structures on the cellular surface of C. albicans suspensions and biofilms. By accomplishing hemagglutination experiments and circular dichroism, we observed that the Con A structure and biochemical properties were preserved after the bioconjugation. Fluorescence microscopy images of yeasts and hyphae cells, as well as biofilms, incubated with QDs-(Con A) showed a bright orange fluorescence profile, indicating that the cell walls were specifically labeled. Furthermore, flow cytometry measurements confirmed that over 93% of the yeast cells were successfully labeled by QD-(Con A) complex. In contrast, non-conjugated QDs or QDs-(inhibited Con A) do not label any kind of biological system tested, indicating that the bioconjugation was specific and efficient. The staining pattern of the cells and biofilms demonstrate that QDs were effectively bioconjugated to Con A with specific labeling of saccharide-rich structures on C. albicans. Consequently, this work opens new possibilities to monitor glucose and mannose molecules through fluorescence techniques, which can help to optimize phototherapy protocols for this kind of fungus.

Topics: Cadmium Compounds; Candida albicans; Concanavalin A; Fluorescent Dyes; Glucose; Mannose; Microscopy, Fluorescence; Quantum Dots; Spectrometry, Fluorescence; Tellurium; Thiomalates

A study of the interactions between nanoparticles and living cells is invaluable in understanding the nano-biological effect and the mechanism of cellular endocytosis. Here we describe two methods for the preparation of semiconductor quantum dots with different physiochemical properties. Furthermore, we describe how to study the interaction of the two quantum dots with living HeLa cells and red blood cells with confocal microscopy.

Topics: Cadmium Compounds; Cell Survival; Erythrocytes; HeLa Cells; Humans; Ligands; Microscopy, Confocal; Nanotechnology; Penicillamine; Quantum Dots; Sulfides; Tellurium; Thiomalates; Zinc Compounds

A new method based on the use of highly fluorescent water-soluble cadmium telluride (CdTe) quantum dots (QDs) capped with mercaptosuccinic acid (MSA) was explored to develop latent fingerprints. After optimized the effectiveness of QDs method contains pH value and developing time, super fast detection was achieved. Excellent fingerprint images were obtained in 1-3s after immersed the latent fingerprints into quantum dots solution on various non-porous surfaces, i.e. adhesive tape, transparent tape, aluminum foil and stainless steel. High sensitivity of the new latent fingerprints develop method was obtained by developing the fingerprints pressed on aluminum foil successively with the same finger. Compared with methyl violet and rhodamine 6G, the MSA-CdTe QDs showed the higher develop speed and fingerprint image quality. Clear image can be maintained for months by extending exposure time of CCD camera, storing fingerprints in a low temperature condition and secondary development.

Topics: Cadmium Compounds; Dermatoglyphics; Fluorescent Dyes; Gentian Violet; Humans; Hydrogen-Ion Concentration; Male; Photography; Quantum Dots; Rhodamines; Solubility; Surface Properties; Tellurium; Thiomalates; Ultraviolet Rays; Water

We here report the CdTe quantum dot (CdTe QDs)-based sensor for probing vitamin B12 derivatives in aqueous solution. In this paper, simple and sensitive fluorescence quenching measurements has been employed. The Stern-Volmer constant (KSV), quenching rate constant (kq) and binding constant (K) were rationalized from fluorescence quenching measurement. Furthermore, the fluorescence resonance energy transfer (FRET) mechanism was discussed. This method was applicable over the concentration ranging from 1 to 14μg/mL (VB12) with correlation coefficient of 0.993. The limit of detection (LOD) of VB12 was found to be 0.15μg/mL. Moreover, the present approach opens a simple pathway for developing cost-effective, sensitive and selective QD-based fluorescence sensors/probes for biologically significant VB12 in pharmaceutical sample with mean recoveries in the range of 100-102.1%.

Topics: Absorption; Cadmium Compounds; Dosage Forms; Electrochemical Techniques; Energy Transfer; Fluorescent Dyes; Humans; Hydrogen-Ion Concentration; Kinetics; Limit of Detection; Quantum Dots; Spectrometry, Fluorescence; Spectrophotometry, Ultraviolet; Tellurium; Thiomalates; Vitamin B 12; X-Ray Diffraction

An aqueous synthesis method to obtain highly luminescent cadmium telluride nanocrystals is described. We have shown water-soluble semi-conductor quantum dots with high photoluminescence quantum yield have great potential for biological applications. The spectral properties of these nanocrystals can be easily tuned according to their particle size to yield multicolours simultaneously by a single excitation light source. A stable precursor material sodium tellurite is utilised instead of the traditional oxygen sensitive NaHTe or H2Te as Te source. We have introduced mercaptosuccinic acid and propylisobutyl polyhedral oligomeric silsesquioxane nanoparticles as novel capping agents to stabilize the nanocrystals, synthesized in borate-citrate buffering system. Inclusion of propylisobutyl polyhedral oligomeric silsesquioxane nanoparticles in the capping procedure showed enhanced stability and biocompatibility. The presence of mercaptosuccinic acid/propylisobutyl polyhedral oligomeric silsesquioxane coatings was confirmed by Fourier Transform Infrared spectroscopy and average sizes of 2-5 nm by transmission electron microscopy measurements. The functionalized and targeted quantum dots detected cancer cell death on exposure to some anticancer drugs. Studies have indicated that apoptotic cells can activate signaling pathways in dendritic cells via ligation of surface receptors. Cells treated with specific class of pro-apototic drug such as anthracyclines mount an anti-tumour immune response when introduced into mice. Apoptotic cells may be immunogenic or non-immunogenic depending on the presence of calreticulin on the plasma membrane of dying tumour cells. Here the confocal microscopy showed localization of conjugated mercaptosuccinic acid/propylisobutyl polyhedral oligomeric silsesquioxane cadmium telluride quantum dots on MCF-7 cells when exposed to cadmium ions at 50 microM, compared to coated quantum dots. We have used cadmium ions as a model drug as certain anticancer drugs (anthracyclines) induce translocation of calreticulin to the cell membrane, an indicator of apoptosis. Antibodies generated against a peptide to human calreticulin and conjugated to quantum dots detected the protein on cell membrane of stimulated cells were visualized by confocal microscopy. Stimulating natural immune response, against tumours has enormous potential to improve current regimens of cancer detection and therapy.

Topics: Breast Neoplasms; Cadmium Compounds; Cell Line, Tumor; Humans; Microscopy, Fluorescence; Nanocapsules; Organosilicon Compounds; Quantum Dots; Staining and Labeling; Tellurium; Thiomalates

Quantum dots (QDs) are fluorescent semiconductor nanocrystals that have the potential for major advancements in the field of nanomedicine through their unique photophysical properties. They can potentially be used as fluorescent probes for various biomedical imaging applications, including cancer localization, detection of micrometastasis, image guided surgery, and targeted drug delivery. Their main limitation is toxicity, which requires a biologically compatible surface coating to shield the toxic core from the surrounding environment. However, this leads to an increase in QD size that may lead to problems of excretion and systemic sequestration. We describe a one pot synthesis, characterization, and in vitro cytotoxicity of a novel polyhedral oligomeric silsesquioxane (POSS)-coated CdTe-cored QD using mercaptosuccinic acid (MSA) and D-cysteine as stabilizing agents. Characterization was performed using transmission electron microscopy Fourier transform infrared spectroscopy, and photoluminescence studies. POSS-coated QDs demonstrated high colloidal stability and enhanced photostability on high degrees of ultraviolet (UV) excitation compared to QDs coated with MSA and D-cysteine alone (P value < 0.05). In vitro toxicity studies showed that both POSS and MSA-QDs were significantly less toxic than ionized salts of Cd(+2) and Te(-2). Confocal microscopy confirmed high brightness of POSS-QDs in cells at both 1 and 24 hours, indicating that these QDs are rapidly taken up by cells and remain photostable in a biological environment. We therefore conclude that a POSS coating confers biological compatibility, photostability, and colloidal stability while retaining the small size and unique photophysical properties of the QDs. The amphiphilic nature of the coating allows solubility in aqueous solutions and rapid transfer across cell membranes, enabling the use of lower concentrations of the QDs for an overall reduced toxicity particularly for prolonged live cell and in vivo imaging applications.

Topics: Analysis of Variance; Cadmium Compounds; Cell Shape; Cell Survival; Cysteine; Hep G2 Cells; Humans; Microscopy, Confocal; Organosilicon Compounds; Quantum Dots; Solubility; Spectroscopy, Fourier Transform Infrared; Surface Properties; Tellurium; Thiomalates; Ultraviolet Rays

Quantum dots (QDs), as novel bioimaging and drug delivery agents, are generally introduced into vascular system by injection, and thus directly exposed to vascular endothelial cells (ECs). However, the adverse effects of QDs on ECs are poorly understood. In this study, employing human umbilical vein ECs (HUVECs), we investigated the potential vascular endothelial toxicity of mercaptosuccinic acid (MSA)-capped CdTe QDs in vitro. In the experiment, water-soluble and pH stable CdTe QDs were synthesized; and the cell viability assays showed that CdTe QDs (0.1-100μg/mL) dose-dependently decreased the cell viability of HUVECs, indicating CdTe QDs induced significant endothelial toxicity. The flow cytometric and immunofluorescence results revealed that 10μg/mL CdTe QDs elicited significant oxidative stress, mitochondrial network fragmentation as well as disruption of mitochondrial membrane potential (Δψ(m)); whereas ROS scavenger could protect HUVECs from QDs-induced mitochondrial dysfunction. Moreover, upon 24h exposure to 10μg/mL CdTe QDs, the apoptotic HUVECs dramatically increased by 402.01%, accompanied with alternative expression of apoptosis proteins, which were upregulation of Bax, downregulation of Bcl-2, release of mitochondrial cytochrome c and cleavage of caspase-9/caspase-3. These results suggested that CdTe QDs could not only impair mitochondria but also exert endothelial toxicity through activation of mitochondrial death pathway and induction of endothelial apoptosis. Our results provide strong evidences of the direct toxic effects of QDs on human vascular ECs, and reveal that exposure to QDs is a significant risk for the development of cardiovascular diseases. These results also provide helpful guidance on the future safe use and manipulation of QDs to make them more suitable tools in nanomedicine.

Topics: Apoptosis; Cadmium Compounds; Cell Culture Techniques; Cell Line; Cell Survival; Dose-Response Relationship, Drug; Drug Carriers; Endothelial Cells; Endothelium, Vascular; Humans; Membrane Potential, Mitochondrial; Microscopy, Electron, Transmission; Mitochondria, Muscle; Quantum Dots; Reactive Oxygen Species; Surface Properties; Tellurium; Thiomalates

Water soluble high quality CdTe nanocrystals (NCs) with mercaptosuccinic acid (MSA) as stabilizer are prepared by refluxing and hydrothermal synthesis in this paper. The MSA stabilizer which comprises both thioglycolic acid (TGA)-like and 3-mercaptopropionic acid (MPA)-like moieties can accelerate the whole growth process of CdTe NCs comparing with TGA-like or MPA-like stabilizer. It takes only 5 min and 2 hours to obtain green emitting (luminescence maximum at 526 nm) and red emitting (luminescence maximum at -650 nm) from CdTe NCs, respectively. In this study, the influences of the ratios of precursors and temperature on CdTe NCs synthesis were studied in detail, and the stable CdTe NCs with high photoluminescence quantum yield and narrow size distribution can be obtained under optimal condition by both routes. The luminescence quantum yield of the green-yellow emitting CdTe NCs obtained in this study can reach 75.2%.

Topics: Cadmium Compounds; Crystallization; Luminescence; Microscopy, Fluorescence; Nanoparticles; Nanotechnology; Optics and Photonics; Spectrometry, Fluorescence; Tellurium; Thiomalates; Time Factors

Here we present a facile one-pot method to prepare high-quality CdTe nanocrystals in aqueous phase. In contrast to the use of oxygen-sensitive NaHTe or H(2)Te as Te source in the current synthetic methods, we employ more stable sodium tellurite as the Te source for preparing highly luminescent CdTe nanocrystals in aqueous solution. By selecting mercaptosuccinic acid (MSA) as capping agent and providing the borate-citrate acid buffering solution, CdTe nanocrystals with high quantum yield (QY >70% at pH range 5.0-8.0) can be conveniently prepared by this method. The influence of parameters such as the pH value of the precursor solution and the molar ratio of Cd(2+) to Na(2)TeO(3) on the QY of CdTe nanocrystals was systematically investigated in our experiments. Under optimal conditions, the QY of CdTe nanocrystals is even high up to 83%. The biological application of luminescent MSA-CdTe to HEK 293 cell imaging was also illustrated.

Topics: Buffers; Cadmium Compounds; Hydrogen-Ion Concentration; Luminescence; Nanostructures; Tellurium; Thiomalates