Determination of quantum dots in single cells by inductively coupled plasma mass spectrometry (original) (raw)
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Evaluation of Quantum Dot Cytotoxicity Based on Intracellular Uptake
Small, 2006
Advances in nanomaterials have led to promising candidates for many biological applications in research and medicine. Their novel physicochemical properties, attributable to their small size, chemical composition, surface structure, solubility, and shape, have been increasingly utilized in medicine for purposes of diagnosis, imaging, and drug delivery. Applications range from the fluorescent tracking of cells [1-3] and immunostaining assays [4] to magnetic resonance imaging. [5] Given the potential for widespread application and commercialization, nanomaterials will be increasingly uti-A C H T U N G T R E N N U N G lized for future biological applications. [6] Quantum dots (QDs) are an example of a nanomaterial that possesses optical properties ideal for biological imaging, which makes them a useful alternative to fluorescent dyes. The organic fluorophores currently used are vulnerable to chemical and metabolic degradation and are easily photobleached, which limits long-term cellular tracking. QDs offer advantages, such as bright photoluminescence, narrow emission, broad UV excitation, and high photostability, [7-9] to help overcome current optical-imaging limitations. Due to the tremendous focus on developing nanoparticles for imaging and therapeutic applications, there has been increasing interest in evaluating the toxicity of nanomaterials, [10] in particular, quantum dots. Some studies suggest that nanomaterials are not inherently benign and affect biological systems at the cellular, subcellular, and protein levels. [11-15] Akerman et al. demonstrated that some nanoparticulates are cleared from the circulation of live mice by the macrophages of the reticuloendothelial system in the liver and spleen. [16] Nevertheless, concerns have surfaced regarding the toxicity of QDs, in particular, those nanoparticles that are cadmium-containing and thus toxic to both cell cul
Evaluation of Toxicity and Gene Expression Changes Triggered by Quantum Dots
Bulletin of The Korean Chemical Society, 2010
Quantum dots (QDs) are extensively employed for biomedical research as a fluorescence reporter and their use for various labeling applications will continue to increase as they are preferred over conventional labeling methods for various reasons. However, concerns have been raised over the toxicity of these particles in the biological system. Till date no thorough investigation has been carried out to identify the molecular signatures of QD mediated toxicity. In this study we evaluated the toxicity of CdSe, Cd1-xZnxS/ZnS and CdSe/ZnS quantum dots having different spectral properties (red, blue, green) using human embryonic kidney fibroblast cells (HEK293). Cell viability assay for both short and long duration exposure show concentration material dependent toxicity, in the order of CdSe > Cd1-xZnxS/ ZnS > CdSe/ZnS. Genome wide changes in the expression of genes upon QD exposure was also analyzed by wholegenome microarray. All the three QDs show increase in the expression of genes related to apoptosis, inflammation and response towards stress and wounding. Further comparison of coated versus uncoated CdSe QD-mediated cell death and molecular changes suggests that ZnS coating could reduce QD mediated cytotoxicity to some extent only.
Experimental approach for an in vitro toxicity assay with non-aggregated quantum dots
Toxicology in Vitro, 2009
Engineered nanoparticles are increasingly used in consumer products. While the potential of these products hold great promise, it is not known what potential toxic effects these nanomaterials may have on human health. There is a need to develop affordable, systematic, short-term in vitro assays aimed at allowing rapid assessment of potential toxicity. The method reported in this paper describes a system in which the intestinal lining is mimicked (Caco-2 human intestinal cell line) and provides an environment in which quantum dots (QDs), and possibly other nanomaterials, can be applied. Transepithelial electrical resistance (TEER) measurements assessed whether the epithelial integrity was breached because of QD exposure. QDs were suspended in calcium/magnesium-free phosphate buffered saline to study non-aggregated QDs. To maintain cell integrity, normal cell culture conditions were retained below the epithelium to provide necessary nutrients and ions. Toxicity studies completed here show that the nanosized QDs coated with hydrophilic thioglycolate capping ligands purchased for these experiments caused disruption in the epithelium monolayer and cell death at 0.1 mg/L of QDs. This toxicity was caused by the nano-size of the QDs rather than the cadmium ions or the sodium thioglycolate capping ligands. Aggregated QDs did not cause toxicity as measured by TEER.
Quantum Dots: Proteomics characterization of the impact on biological systems
Journal of Physics: Conference Series, 2009
Over the past few years, Quantum Dots have been tested in most biotechnological applications that use fluorescence, including DNA array technology, immunofluorescence assays, cell and animal biology. Quantum Dots tend to be brighter than conventional dyes, because of the compounded effects of extinction coefficients that are an order of magnitude larger than those of most dyes. Their main advantage resides in their resistance to bleaching over long periods of time (minutes to hours), allowing the acquisition of images that are crisp and well contrasted. This increased photostability is especially useful for three-dimensional (3D) optical sectioning, where a major issue is bleaching of fluorophores during acquisition of successive z-sections, which compromises the correct reconstruction of 3D structures. The long-term stability and brightness of Quantum Dots make them ideal candidates also for live animal targeting and imaging. The vast majority of the papers published to date have shown no relevant effects on cells viability at the concentration used for imaging applications; higher concentrations, however, caused some issues on embryonic development. Adverse effects are due to be caused by the release of cadmium, as surface PEGylation of the Quantum Dots reduces these issues. A recently published paper shows evidences of an epigenetic effect of Quantum Dots treatment, with general histones hypoacetylation, and a translocation to the nucleus of p53. In this study, mice treated with Quantum Dots for imaging purposes were analyzed to investigate the impact on protein expression and networking. Differential monoand bidimensional electrophoresis assays were performed, with the individuation of differentially expressed proteins after intravenous injection and imaging analysis; further, as several authors indicate an increase in reactive oxygen species as a possible mean of damage due to the Quantum Dots treatment, we investigated the signalling pathway of APE1/Ref1, a protein involved in the response to oxidative stress. Our results, although preliminary, suggest several interesting point of discussion on Quantum Dots imaging for in vivo diagnostic application, but also for a new therapeutic approach.
Journal of Nanobiotechnology, 2010
Background: The unique and tuneable photonic properties of Quantum Dots (QDs) have made them potentially useful tools for imaging biological entities. However, QDs though attractive diagnostic and therapeutic tools, have a major disadvantage due to their inherent cytotoxic nature. The cellular interaction, uptake and resultant toxic influence of CdTe QDs (gelatinised and non-gelatinised Thioglycolic acid (TGA) capped) have been investigated with pheochromocytoma 12 (PC12) cells. In conjunction to their analysis by confocal microscopy, the QD -cell interplay was explored as the QD concentrations were varied over extended (up to 72 hours) co-incubation times. Coupled to this investigation, cell viability, DNA quantification and cell proliferation assays were also performed to compare and contrast the various factors leading to cell stress and ultimately death.
Intracellular distribution of nontargeted quantum dots after natural uptake and microinjection
International Journal of Nanomedicine, 2013
Background: The purpose of this study was to elucidate the mechanism of natural uptake of nonfunctionalized quantum dots in comparison with microinjected quantum dots by focusing on their time-dependent accumulation and intracellular localization in different cell lines. Methods: The accumulation dynamics of nontargeted CdSe/ZnS carboxyl-coated quantum dots (emission peak 625 nm) was analyzed in NIH3T3, MCF-7, and HepG2 cells by applying the methods of confocal and steady-state fluorescence spectroscopy. Intracellular colocalization of the quantum dots was investigated by staining with Lysotracker ®. Results: The uptake of quantum dots into cells was dramatically reduced at a low temperature (4°C), indicating that the process is energy-dependent. The uptake kinetics and imaging of intracellular localization of quantum dots revealed three accumulation stages of carboxyl-coated quantum dots at 37°C, ie, a plateau stage, growth stage, and a saturation stage, which comprised four morphological phases: adherence to the cell membrane; formation of granulated clusters spread throughout the cytoplasm; localization of granulated clusters in the perinuclear region; and formation of multivesicular body-like structures and their redistribution in the cytoplasm. Diverse quantum dots containing intracellular vesicles in the range of approximately 0.5-8 µm in diameter were observed in the cytoplasm, but none were found in the nucleus. Vesicles containing quantum dots formed multivesicular body-like structures in NIH3T3 cells after 24 hours of incubation, which were Lysotracker-negative in serum-free medium and Lysotracker-positive in complete medium. The microinjected quantum dots remained uniformly distributed in the cytosol for at least 24 hours. Conclusion: Natural uptake of quantum dots in cells occurs through three accumulation stages via a mechanism requiring energy. The sharp contrast of the intracellular distribution after microinjection of quantum dots in comparison with incubation as well as the limited transfer of quantum dots from vesicles into the cytosol and vice versa support the endocytotic origin of the natural uptake of quantum dots. Quantum dots with proteins adsorbed from the culture medium had a different fate in the final stage of accumulation from that of the protein-free quantum dots, implying different internalization pathways.
An experimental and theoretical assessment of quantum dot cytotoxicity
Toxicol. Res., 2015
Quantum dots (QDs) are a class of semiconductor nanoparticles that possess a unique set of size-tunable optical properties. The potential applications of QDs in biological and medical applications are enormous -some notable examples being in high-resolution cellular imaging, cancer tumour targeting and drug delivery. However, the mechanisms for QD-cell interactions are at best partially understood, and QD cytotoxicity is an ongoing concern. In particular, it remains unclear how QD uptake by cells and subsequent cell fate are influenced by QD parameters such as size, composition, concentration, and exposure time. To help resolve this complex issue in a systematic manner, we have developed here one of the first mathematical models that describes the toxic effects of QDs on cells. The model consists of a system of ordinary differential equations describing (among other things) the transition of healthy cells to an apoptotic or necrotic state induced by QD toxicity. We also experimentally investigated the behaviour of a cell population subsequent to exposure to various types of CdTe QDs. In a population of identical cells exposed to QDs of similar size (2-5 nm), it was found that some of the cells entered apoptosis, others entered necrosis, and others demonstrated no response at all. The toxicity of the various QDs was conveniently quantitatively assessed using the parameters appearing in the mathematical model, and satisfactory agreement between theory and experiment was found. †Electron ic supplem en tary in form ation (ESI) available. See DOI: 10.1039/ c5tx00149h ‡Auth ors m ade equal con tribution to experim en ts an d m an uscript preparation .
Bioconjugate Chemistry
Interest in taking advantage of the unique spectral properties of semiconductor quantum dots (QDs) has driven their widespread use in biological applications such as in vitro cellular labeling/imaging and sensing. Despite their demonstrated utility, concerns over the potential toxic effects of QD core materials on cellular proliferation and homeostasis have persisted, leaving in question the suitability of QDs as alternatives for more traditional fluorescent materials (e.g., organic dyes, fluorescent proteins) for in vitro cellular applications. Surprisingly, direct comparative studies examining the cytotoxic potential of QDs versus these more traditional cellular labeling fluorophores remain limited. Here, using CdSe/ZnS (core/shell) QDs as a prototypical assay material, we present a comprehensive study in which we characterize the influence of QD dose (concentration and incubation time), QD surface capping ligand and delivery modality (peptide or cationic amphiphile transfection r...