Colloidal quantum dots for fluorescent labels of proteins (original) (raw)
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Application of Antibody-Conjugated CdSe/MSA Quantum Dots on Immunohistochemistry
SSR Institute of International Journal of Life Sciences, 2020
Background: Quantum dots (QDs) are recently conjugated to antibody for using in biological labeling applications. In previous studies, we developed CdSe/MSA QDs, which were coated with protein A/G (pA/G) for antibody conjugation, and evaluated their cell staining application. Here, we expanded their applications into immunohistochemistry (IHC) by investigating their storage time by accelerated heat aging method, and comparing them with FITC in sample labeling. Methods: Cytokeratin 6A (KRT6A) in animal skin tissue section were stained by pA/G-coated QDs conjugated to anti-KRT6A antibody and TF-1 human erythroleukemia cells were stained by pA/G-coated QDs conjugated to anti-CD34 antibody. Results: The results indicated that our pA/G-coated QDs effectively stained KRT6A in epidermis of skin tissue section when they were probed with specific antibody. Besides, pA/G-coated QDs still maintained their labeling ability in cell staining and IHC formats after 12-month storage at 4 o C. In comparison with FITC (relatively almost the same emission fluorophore), our QDs showed a significantly stronger fluorescent signal. Conclusion: In conclusion, these results indicated that our pA/G-coated QDs were potentially fluorescent nanomaterials and could be applied in a wide range of biological labeling applications.
Quantum dots as fluorescent bio-labels in cancer diagnostic
2006
In this work we present and discuss some results concerning the application of colloidal semiconductor quantum dots for cancer diagnostic. We have prepared and applied different core-shell semiconductor quantum dots such as Cadmium Teluride-Cadmium Sulfide (CdTe-CdS) and Cadmium Sulfide -Cadmium Hydroxide (CdS/Cd(OH) 2 ). For the purpose of diagnostic with living cells, the CdS/Cd(OH) 2 presented best results, maintaining high levels of luminescence as well high stability in biological media. The quantum dots were obtained in aqueous medium, by reacting Cd 2+ and S 2in the presence of sodium polyphosphate as the stabilizing agent. Subsequent surface passivation with Cd(OH) 2 was carried out to improve luminescence. At a pH of 7,2 the quantum dots were functionalized with a 0.01% glutaraldehyde solution and then, incubated with living healthy and neoplastic cells (glial, glioblastoms and cervical) and tissues (breast) in culture medium. Tissue and cell staining were evaluated by the laser scanning confocal microscopy. Fluorescence Microscopy was used as a primary tool in order to explore the labeling of the samples. The procedure presented in this work, shown to be very efficient as a potential tool for fast and precise cancer diagnostic.
Introducing the Safe Capsule for CdS Quantum Dots as Bio-Labeling Device
Bio-labeling applications of quantum dots (QDs) have grabbed scientists' attention due to their numerous benefits to human life. The quality properties such as strong, narrow, tunable and size-dependent emission of broad absorption spectrum QDs, combined with water-solubility and non-toxicity, are needed for QDs to perform as excellent labeling tools in biological applications. Besides, predictable and reliable controls to achieve perfect and biologically safe QDs with excellent optical properties are expected. In this study, we managed to synthesize cadmium sulfide (CdS) QDs with a mean size of 8nm by capping it with thioglycolic acid-which has hydrogen bonding-to make QDs soluble in aqueous solutions. Polyethilenimine has functioned to render the QDs to be water soluble and enhances photo-oxidation even in aqueous solution. It also acted as a ligand to modify CdS QDs to prevent surface trap and thus increase CdS QDs' quantum yield. Furthermore, improved stability of the QDs in polymer sphere and non-toxicity is needed. Therefore, the ideal bio-labeling QDs should be dense and equal in size and shape to achieve constant photoluminescence peak. Hence, the CdS QDs have been capsulated with poly(2vinylpyridine) (P2VP) homopolymers and apo-ferritin in order to compare which one is the best capsule for QDs with the desired properties for applications in bio-labeling.
Detection of Bioconjugated Quantum Dots Passivated with Different Ligands for Bio-Applications
Bioconjugation of quantum dots has resulted in a significant increase in resolution of biological fluorescent labeling. This intrinsic property of quantum dots can be utilized for sensitive detection of target analytes with high sensitivity; including pathogenic bacteria and cancer monitoring. The quantum dots and quantum dot doped silica nanoparticles exhibit prominent emission peaks when excited at 400 nm but on conjugation to model rabbit antigoat antibodies exhibit diminished intensity of emission peak at 600 nm. It shows that photoluminescence intensity of conjugated quantum dots and quantum dot doped silica nanoparticles could permit the detection of bioconjugation. Samples of conjugated and unconjugated quantum dots and quantum dot doped silica nanoparticles were subjected to enzyme linked immunosorbent assay for further confirmation of bioconjugation. In the present study ligand exchange, bioconjugation, fluorescence detection of bioconjugated quantum dots and quantum dot doped silica nanoparticles and further confirmation of bioconjugation by enzyme linked immunosorbent assay has been described.
Journal of Nanoscience and Nanotechnology, 2014
Herein, we have demonstrated a facile and green approach for the synthesis of Cadmium selenide (CdSe) quantum dots (QDs). The process was mediated by bovine serum albumin (BSA) and it was found that BSA plays the dual role of reducing agent as well as a stabilizing agent. The QDs exhibited sharp excitonic absorption features at ∼ 500 nm and subsequently showed reasonably good photoluminescence (PL) at room temperature. The PL is seen to be strongly dependent on the concentration of the precursors and hence, the luminescence of these QDs could be conveniently tuned across the visible spectrum simply by varying molar ratio of the precursors. It can be envisaged from the fact that a red-shift of about 100 nm in the PL peak position was observed when the molar ratio of the precursors ([Cd 2+ ]:[Se 2− ], in mM) was varied from 10:5 to 10:40. Subsequently, the charge carrier relaxation dynamics associated with the different molar ratio of precursors has been investigated and very interesting information regarding the energy level structures of these QDs were revealed. Most importantly, in conjunction with the optical tuning, the nanomorphology of these nanoparticles was found to vary with the change in molar ratios of Se and Cd precursors. This aspect can provide a new direction of controlling the shape of CdSe nanoparticles. The possible mechanism of the formation as well as for the shape variation of these nanoparticles with the molar ratios of precursors has been proposed, taking into account the role of amino acid residues (present in BSA). Moreover, the QDs were water soluble and possessed fairly good colloidal stability therefore, can have potential applications in catalysis and bio-labeling. On the whole, the present methodology of protein assisted synthesis is relatively new especially for semiconducting nanomaterials and may provide some unique and interesting aspects to control and fine tune the morphology vis-à-vis, their optical properties.
Highly fluorescent CdTe quantum dots with reduced cytotoxicity-A Robust biomarker
Sensing and Bio-Sensing Research, 2015
L-Cysteine (Cys) capped CdTe quantum dots (CdTe@Cys QDs) were successfully synthesized in an aqueous medium. The synthesized CdTe@Cys samples were analyzed using Fourier transform infrared (FT-IR) spectroscopy, fluorescence (FL) spectroscopy, transmission electron microscopy (TEM), confocal microscopy and subsequently subjected to the antibacterial test. Systematic investigations were carried out for the determination of optimal conditions namely the ratios of Cd:Te, CdTe:Cys, pH value and the chemical stability of CdTe@Cys. Moreover, the reactivation of FL intensity in the CdTe@Cys sample was done easily by the addendum of Cys. The introduction of additional cysteine to the CdTe@Cys QDs sample showed an enhancement in terms of the FL intensity and stability along with the reduced antibacterial activity. This was further confirmed through Thiazolyl blue tetrazolium bromide (MTT) assays. Both the result of the bio-stability tests namely the antibacterial test and MTT assay displayed similarities between the externally added Cys and cytotoxicity of the bacteria and human HeLa cancer cell lines. Confocal microscopic images were captured for the CdTe@Cys conjugated Escherichia coli.
Luminescence, 2011
Functionalized CdTe-CdS core-shell quantum dots (QDs) were synthesized in aqueous solution via water-bathing combined hydrothermal method using L-cysteine (L-Cys) as a stabilizer. This method possesses both the advantages of waterbathing and hydrothermal methods for preparing high-quality QDs with markedly reduced synthesis time, and better stability than a lone hydrothermal method. The QDs were characterized by transmission electronic microscopy and powder X-ray diffraction and X-ray photoelectron spectroscopy. The CdTe-CdS QDs with core-shell structure showed both enhanced fl uorescence and better photo stability than nude CdTe QDs. After conjugating with antibody rabbit anti-CEACAM8 (CD67), the as-prepared L-Cys capped CdTe-CdS QDs were successfully used as fl uorescent probes for the direct immuno-labeling and imaging of HeLa cells. It was indicated that this kind of QD would have application potential in bio-labeling and cell imaging.
Journal of Luminescence, 2012
CdTe/CdS/ZnS core-shell-shell quantum dots (QDs) were synthesized in aqueous solution via waterbathing combined hydrothermal method using L-cysteine as a stabilizer. The present method features markedly reduced synthesis time, higher fluorescent intensity and lower cytotoxicity of the QDs. Structural and spectroscopic properties of core-shell-shell QDs are well characterized by absorption and fluorescence spectroscopy, X-ray diffraction, transmission electron microscopy, and fourier transform infrared spectroscopy. Both CdS and ZnS shells were capped on the CdTe core and the fluorescence was greatly enhanced by the ZnS coating. The ternary QDs conjugated with transferrins were successfully employed for the biolabeling and fluorescent imaging of HeLa cells. Cytotoxicity evaluation shows that CdTe/CdS/ZnS was less toxic for cells than CdTe and CdTe/CdS due to the presence of a ZnS coating on surface, which inhibited the release of cadmium ions.