Biodistribution and stability of CdSe core quantum dots in mouse digestive tract following per os administration: Advantages of double polymer/silica coated nanocrystals (original) (raw)
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Biocompatible CdSe−ZnS Core−Shell Quantum Dots Coated with Hydrophilic Polythiols
Langmuir, 2009
We designed four polymeric ligands for semiconductor quantum dots and synthesized these macromolecular constructs in four steps, starting from commercial precursors. These ligands have a poly(methacrylate) backbone with pendant thiol groups and poly(ethylene glycol) chains. The thiol groups anchor these ligands on the surface of preformed CdSe-ZnS core-shell quantum dots, and the poly(ethylene glycol) chains impose hydrophilic character on the resulting assemblies. Indeed, three of the four sets of quantum dots are soluble in aqueous environments and are stable under these conditions for days over a wide pH range (5.0-9.0). Furthermore, the polymeric coatings wrapped around the inorganic nanoparticles preserve the photophysical properties of the CdSe core and ensure relatively compact dimensions. Specifically, the luminescence quantum yield is ca. 0.4 and the hydrodynamic diameter ranges from 15 to 29 nm with the nature of the polymeric ligand. Model studies with human umbilical vein endothelial cells demonstrated that these hydrophilic quantum dots cross the cell membrane and localize either in the cytosol or in the nucleus. The length of the poly(ethylene glycol) chains appears to guide the intracellular localization of these luminescent probes. In addition, these studies indicated that these particular nanoparticles are not cytotoxic. In fact, their cellular internalization has essentially no influence on cell growth. In summary, we developed novel polymeric ligands able to impose hydrophilic character and biocompatibility on CdSe-ZnS core-shell nanoparticles. Thus, our results can lead to a new family of valuable luminescent probes for cellular imaging, based on the unique photophysical properties of semiconductor quantum dots.
Synthesis and Characterization of Aqueous Carboxyl-Capped CdS Quantum Dots for Bioapplications
Industrial & Engineering Chemistry Research, 2007
A direct and environmentally friendly synthesis method was developed to produce aqueous CdS quantum dots (QDs) at room temperature. The transmission electron microscopy (TEM) and X-ray diffraction (XRD) results showed the small size and the cubic zinc blende structure of the nanocrystals. The quantum yield was comparable to that of the commercial core-shell QDs. With 3-mercaptopropionic acid (MPA) as the capping molecule, the feasibility of using the aqueous CdS QDs as imaging tool was demonstrated with Salmonella typhimurium cells. The photoluminescence (PL) properties of the present aqueous CdS QDs can be optimized by adjusting various processing parameters. The emission was due to trap states and was related to the dispersion condition. In particular, with higher pH and MPA/Cd ratio of 2, the QDs exhibited stronger emission. The temperature-and concentration-dependent properties of QDs resulted from the intrinsic interactions between nanoparticles. The aqueous CdS QDs displayed long lifetime of 12 h under UV light and excellent stability in DI water, PBS, and cytosol for more than 26 days. The ease of processing and good PL properties of the aqueous CdS QDs provide a practical and economical approach for single-target imaging application.
Cytotoxicity and fluorescence studies of silica-coated CdSe quantum dots for bioimaging applications
Journal of Nanoparticle Research, 2011
The toxicological effects of silica-coated CdSe quantum dots (QDs) were investigated systematically on human cervical cancer cell line. Trioctylphosphine oxide capped CdSe QDs were synthesized and rendered water soluble by overcoating with silica, using aminopropyl silane as silica precursor. The cytotoxicity studies were conducted by exposing cells to freshly synthesized QDs as a function of time (0-72 h) and concentration up to micromolar level by Lactate dehydrogenase assay, MTT [3-(4,5-Dimethylthiazol-2-yl)-2,5-Diphenyltetrazolium Bromide] assay, Neutral red cell viability assay, Trypan blue dye exclusion method and morphological examination of cells using phase contrast microscope. The in vitro analysis results showed that the silica-coated CdSe QDs were nontoxic even at higher loadings. Subsequently the in vivo fluorescence was also demonstrated by intravenous administration of the QDs in Swiss albino mice. The fluorescence images in the cryosections of tissues depicted strong luminescence property of silica-coated QDs under biological conditions. These results confirmed the role of these luminescent materials in biological labeling and imaging applications.
2001
We describe the synthesis of water-soluble semiconductor nanoparticles and discuss and characterize their properties. Hydrophobic CdSe/ZnS core/shell nanocrystals with a core size between 2 and 5 nm are embedded in a siloxane shell and functionalized with thiol and/or amine groups. Structural characterization by AFM indicates that the siloxane shell is 1-5 nm thick, yielding final particle sizes of 6-17 nm, depending on the initial CdSe core size.
Examination of the stability of hydrophobic (CdSe)ZnS quantum dots in the digestive tract of rats
Photochemical and Photobiological Sciences, 2008
Semiconductor quantum dots show promise as alternatives to organic dyes for biological labelling because of their bright and stable photoluminescence. The typical quantum dots is CdSe because colloidal synthesis for nanocrystals of this semiconductor is well established. CdSe is usually passivated with zinc sulfide. While the cytotoxicity of bulk CdSe is well documented, questions about (CdSe)ZnS potential toxicity and behaviour in vivo remain unanswered. The distribution and stability of (CdSe)ZnS quantum dots in Wistar line rats' digestive tract were investigated. Hydrophobic quantum dots were mixed with fat or sonificated in water and administered orally. The distribution and stability of quantum dots moving through the digestive system of rats was followed by fluorescence spectroscopy. In both ways prepared quantum dots were degraded in the digestive tract of animals. Quantum dots mixed with fat were more stable and degraded more slowly than quantum dots sonificated in water. The data obtained suggest possible toxicity of (CdSe)ZnS quantum dots due to the liberation of Cd 2+ .
Bioconjugate Chemistry, 2008
Chemical modification of the surface of CdSe/ZnS quantum dots (QDs) with small molecules or functional ligands often alters the characteristics of these particles. For instance, dopamine conjugation quenches the fluorescence of the QDs, which is a property that can be exploited for sensing applications if the conjugates are taken up into living cells. However, different sizes and/or preparations of mercaptocarboxylic acid solubilized QDs show very different properties when incubated with cells. It is unknown what physical parameters determine a QDs ability to interact with a cell surface, be endocytosed, escape from endosomes, and/or enter the nucleus. In this study, we examine the surface chemistry of QD-dopamine conjugates and present an optimized method for tracking the attachment of small biomolecules to the surface. It is found that the fluorescence intensity, surface charge, colloidal stability, and biological interactions of the QDs vary as a function of the density of dopamine on the surface. Successful targeting of QD-dopamine to dopamine receptor positive PC12 cells correlates with greater homogeneity of particle thiol layer, and a minimum number of ligands required for specific association can be estimated. These results will enable users to develop methods for screening QD conjugates for biological activity before proceeding to experiments with cell lines and animals.
Journal of Nanoparticle Research, 2016
A silanization process was employed to transfer hydrophobic quantum dots (QDs) prepared via an organic route at high temperature into water phase. The QDs were further coated with a thin organic SiO 2 shell to form QDs@SiO 2 composite nanoparticles by ligand exchange or remaining initial organic ligands on the surface. In this study, QDs with different ligands, either trioctylphosphine oxide (TOPO) or oleic acid (OA), were employed to investigate the effects of ligands on the reverse micelles in preparing QDs@SiO 2 nanoparticles. In the preparing process, hydrophobic QDs were silanized by partially hydrolyzed tetraethyl orthosilicate (TEOS). For TOPO-capped CdSe QDs, surface TOPO ligands were completely replaced by partially hydrolyzed TEOS. As for OA-capped CdSe/Cd x Zn 1-x S QDs, surface OA ligands were partially replaced. It was found that the ligand exchange drastically reduced the photoluminescence (PL) efficiency of CdSe QDs. Furthermore, the cytotoxicity studies of QDs@SiO 2 have been carried out in detail. The results indicate that CdSe/Cd x Zn 1-x S QDs@SiO 2 composite nanoparticles exhibit lower cytotoxicity compared with CdSe QDs@SiO 2 , because the SiO 2 shell and remained OA ligand layer can effectively prevent the leakage of toxic Cd 2? ions. Meanwhile, it was found that these CdSe/Cd x Zn 1-x S QDs@SiO 2 nanocomposites could keep excellent PL properties even for 24 h incubating with Siha cells, which indicating that our prepared composite nanoparticles are potentially applicable for cell imaging in biological systems.
Journal of Luminescence, 2018
The cytotoxicity of Cd based Quantum dots (QDs) is major concern that hinders their practical use in bioimaging. Therefore, the objective of first of its kind report is to overcome this hindrance where the comparative cytotoxicity study of poly CdSe, CdSe QDs, CdSe/ZnS QDs and CdSe QDs encapsulated by TEOS, polyvinylalcohal and polyethylene glycol being presented. All the QD were synthesized and encapsulated by wet chemical method and studied. Prepared QDs were monodispersed, spherical in shape and exhibited size range of 1.8 to 2.2 nm. Elemental analysis confirms the formation of CdSe QDs and other mentioned structures. Surface functional groups notify the biocompatibility of core-shell and encapsulated QDs with respect to poly and bare CdSe QDs. Cytotoxicity of QDs was analyzed using human embryonic kidney cell line. Encapsulated QDs were tested even at very high concentrations and for long incubation time of 24 hours and even upto 72 hours of incubation. Core-shell and encapsulated QDs acquire excellent monochromatic luminescence intensity and negligible cytotoxicity as compared to prepared poly CdSe and bare CdSe QDs thus can be used as luminescent probes for bioimaging.
Synthesis and Surface Modification of Biocompatible Water Soluble Core-Shell Quantum Dots
Advanced Materials Research, 2014
In this study, the applications of CdSe/ZnS quantum dots (QDs) and its role in advanced sensings has been explored. The CdSe/ZnS was synthesized by using hot injection method with the shell ZnS layer was made using successive ionic layer adsorption and reaction (SILAR) method. The morphology of the CdSe/ZnS QDs was studied using Transmission Electron Microscope (TEM) and the average particle size was in 10-12 nm range. The prepared QDs were optically characterized using spectrofluorescence and strong emission was observed at 620 nm. Comparison of the fluorescence emissions of CdSe/ZnS capped with various capping ligands such as L-cysteine, thioglycolic acid (TGA), mercaptopropionic acid (MPA), mercaptosuccinic acid (MSA) and mercaptoundecanoic acid (MUA) were studied. The CdSe/ZnS capped with TGA gave the strongest fluorescence emission compared to others.
Effect of light on stability of thiol-capped CdSe/ZnS quantum dots in the presence of albumin
Lithuanian Journal of Physics, 2015
The effect of exposure to the green laser light on the photoluminescence (PL) stability of CdSe/ZnS quantum dots (QDs) capped with either mercaptopropionic (MPA) or thioglycolic (TGA) acid was studied in aqueous suspensions and in the presence of bovine serum albumin (BSA). The results of absorbance and luminescence measurements suggest that the capacity of protein to change the coating structure of thiol-capped QDs and the stability of photoluminescence depends on the nature of stabilizing surface ligands. The interaction of BSA molecules with TGA-capped quantum dots increases their PL quantum yield (QY) and makes PL more stable, however, the effect is opposite for MPA-capped QDs. The light exposure instantly increases the PL intensity and the quantum yield of TGA-capped QDs but does not change those of MPA-capped QDs. In the medium with BSA, however, the occurrence of light-induced PL enhancement does not depend on stabilizing thiol ligands of QDs and it lasts for a relatively long period of time.