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Nanotechnology , 19 29 , Journal of Fluorescence , DOI: Pair your accounts. Wheat seeds Triticum aestivum L. Four treatments, each with three replicates, were applied, starting on the day of seed germination as outlined in Table 1. Briefly, seeds were soaked with either QDs  or water for the control group all day long. Five graded doses of UV-B radiation intensities were tested: B1 2. The effect of UV-B and QDs doses on seedling growth were determined by assessing height, root length, and the concentrations of malondialdehyde MDA , soluble sugar and soluble protein.
Five-day-old wheat seedlings were subsequently treated with the doses showing the most inhibitory effect and more detailed analyse including plant height, root length, biomass, and chlorophyll content were performed. After 5 d of growth, the plant height and root length were measured with a ruler. Twenty seedlings per replicate per treatment were randomly selected for analysis. A total of 90 seedlings were assessed for height, fresh weight FW , and dry weight DW. Fresh and dry weights were detected with an analytical balance. Chlorophyll content was measured as described .
Fresh tissues 1. After centrifugation at rpm for 10 min, supernatants were removed, added to 2 mL 0. Reactions were stopped on ice. After centrifugation at rpm for 15 min, supernatants were assayed at and nm. Total sugar concentration was determined using anthrone colorimetry. Samples were then cooled for 5 min before spectrophometric absorbance assessment at nm. Concentrations were determined using standard curves. Soluble protein was extracted according to Zhao  , using bovine serum albumin as a calibration standard.
After centrifugation, supernatants were added to 5 mL Coomassie brilliant blue G and incubated at room temperature for 15 min before spectroscopic assessment at nm. After exposure to CdTe-QDs for 5 days, 4—7 plants were recovered and roots were rinsed thoroughly with deionized water to remove material that was neither adsorbed nor integrated into the plant tissues. Samples were transferred to polypropylene tubes and centrifuged at g for 10 min. Supernatants were recovered and brought to 10 mL using deionized water.
Determination of H 2 O 2 content in plant extracts.
Frozen plant tissues 0. The content of H 2 O 2 was analyzed with a hydrogen peroxide assay kit Beyotime, China according to the manufacturer instruction. Absorbance values were calibrated to a standard curve generated with known concentrations of H 2 O 2 . The reaction was stopped by transferring the seedlings into distilled water.
The A was immediately measured and compared with a standard curve obtained from known amounts of NBT in the KOH-dimethyl sulfoxide mixture . Cell observations were performed on at least three replicate samples. Quantum dots were excited at nm. DNA concentration was determined by spectrophotometry. CdTe-QDs had an average diameter of 2. Emission spectra collected over a period of 7 days are shown in Figure 3. QDs emission intensity decreased daily, with a total decrease of approximately 6. These results indicated that almost Treatments of seedlings with five different concentrations of CdTe-QDs resulted in reductions in shoot height and root length, increased lipid oxidation as measured by the levels of the oxidation product MDA, as well as reductions in soluble sugar and soluble protein concentrations, in a dose dependent manner when compared with the control CK group Figure 4.
Treatments of seedlings with graded doses of UV-B irradiation led to similar growth inhibition as assessed by the above parameters Figure 5. The UV-B dose of Root length was reduced in all three treatment groups compared to the control group Figure 6. This is likely due to the direct contact exposure of roots to the CdTe-QDs suspension. The growth and chlorophyll contents of wheat seedlings exposed to different treatments were determined Tables 2 and 3.
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UV-B radiation treatment resulted in a significantly reduction in plant height with an average height Similarly, chlorophyll content, both chlorophyll a and b , were significantly lower than in controls Table 3. Average root length in CdTe-QDs-treated plants was Total biomass was similar between the UV-B and QDs treated groups, but was significantly reduced compared to control untreated seedlings. The combined treatment group showed a significant reduction in plant height, root length, and total biomass when compared to the control group and the single treatment groups Table 2.
Their imbalance can be highly cytotoxic  , . Furthermore, there was These results are consistent with the greater toxicity from higher levels of Cd following UV-B irradiation predicted for roots. The relatively moderate effect in the Cd-associated ROS production in shoots is likely due to the low levels of Cd accumulation in shoots Figure 7.
Finally, H 2 O 2 activation of caspase can lead to programmed cell death  , . Photosynthesis, which is susceptible to changes in light, mainly occurs in leaves . However, it is currently unknown whether UV-B irradiation used in this study stimulates antioxidant enzyme activities in the same pathway.
However, the other enzymes were significantly inhibited in the UV-B treated group compared to the control group. There were also significant difference in enzyme activities between the CdTe-QDs treated group and the control group, but the effects were not as marked as with the UV-B treated group Figure 11 upper part.
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Electrophoresis gels of DNA extracted from wheat with different treatments. It has been demonstrated that CdSe-QDs, through the apoplastic pathway with the aid of silwet L, could be transferred into roots and were stable . We therefore examined root cells of wheat seedling for the presence of CdSe-QDs using confocal microscopy Figure No fluorescence signal was detected in the untreated control a, b, c and in the UV-B treated cells d, e, f.
As shown in the DIC images, cells in the control group exhibited a clear outline of cell wall and regular shape ove three day period. In contrast, cells in the UV-B treated group showed the presence of intracellular vesicles on the fifth day and apparent abnormal rectangular shapes f. CdTe-QDs are indicated by fluorescence imaging g, h, i, m, n, o, s , DIC images demonstrate cell integrity a, b, c, d, e, f, j, k, l, p, q, r, t.
Regions highlighted in red in panel e are shown in panels s, t, and u. Pictures of the bottom right corner in figure j, k, l, p, q, r is the merge figures of g and j, h and k, i and l, m and p, n and q, o and r separately. Cell morphology appeared normal, with smooth surface and intact cell walls. After 4 days of treatment h, k , vacuolation of cytoplasm appeared in some cells as shown ringed in red k and at higher magnification s, t, u.
Many small vesicles appeared around the nucleus t , and CdTe-QDs were located inside the nucleus u. This indicated the CdTe-QDs may enter the nucleus through the nuclear pore. CdTe-QDs were not uniformly distributed, but were found preferentially in and around the nucleus u.
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A putative vesicle transport mechanism is shown in Figure We propose that following the uptake of QDs by plant cells, PCs bind to Cd and form stable metal chelate complexes that are stored in the vacuole. We inferred that NPs could produce a nanostructure that lead to an increase in the concentration of Cd around the nucleus, resulting in an increased cytotoxicity . After 5 days of treatment i, l , cell walls appeared looser and cells more variable in size l , and the CdTe-QDs fluorescence intensity was reduced i.
Their work showed that, along with electrostatic forces, QD size has a strong influence on MT proteins and QDs, with the smallest QDs having a higher affinity for this type of interaction. The increased fat storage in the intestines of the nematodes was attributed to the prolonged defection cycle length and not to the cadmium ions released from the QDs.
These findings shed light on the environmental impact of CdTe QDs on the lipid metabolism in certain animals. QD-induced nanotoxicity was observed in the studied cell lines, with autophagy as the general response to QD exposure. For the murine model, the injection of QDs determined splenic injury, liver injury, nephrotoxicity and hematopoietic disorders, with ROS involved in toxicity induction and autophagy initiation.
Cadmium oxide nanoparticle toxicity was evaluated by Balmuri et al on a zebrafish model. They studied two types of CdO nanoparticles: one where CdO was obtained through calcination of Cd OH 2 to yield nanoparticles without any organic molecules on the surface CdO-1 and another type that involved the calcination of Cd-citrate CdO The toxic effect registered for the CdO-2 was lower than for the CdO-1; this result could be attributed to a carbon layer that covered the surface of CdO-2 during the calcination process.
Saccharomyces cerevisiae yeast was used, as a model, by Pasquali et al in order to shed light on the effect of CdS QDs on the complex genetic networks that regulate nucleo-mitochondrial interaction. The results showed the disruption of the mitochondrial morphology, a reduced mitochondrial function and induced oxidative stress. Results showed that even when CdS QDs were coated with this biocompatible aminopropylsaccharide shell induced a severe inhibition of cell viability for human osteosarcoma cells SAOS and for human embryotic kidney cells HEKT.
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The released Ag from the QDs is excreted through both feces and urine, and the Se element is hardly excreted Figure 6. Biotransformation of Ag2Se, where Ag released from the QDs is excreted through feces and urine and the Se element is hardly excreted. Blood clearance, distribution, transformation, excretion, and toxicity of near-infrared quantum dots Ag2Se in mice. In order to passivate QDs for biological applications. They can be encapsulated in phospholipid micelles.
This approach has several advantages, such as it does not alter their surface, the optical properties of the QDs are retained, due to the highly dense surface of the micelles nonspecific adsorption is prevented and the supramolecular architecture is maintained by local hydrophobic interactions. For example, a QD with a 4 nm diameter can have its surface functionalized with 2—5 protein molecules or 50 small molecules. The potential toxicity of different types of QDs such as metal-free or CQDs remains one of the main interests of the scientific community with the need of better understanding the interactions between QDs and biological macromolecules.
It is clear that QDs have great potential for applications in areas such as drug delivery, sensors and bio-imaging. In order to see QDs realistically translated in clinical applications, several issues still need to be addressed, such as overall toxicity, body clearance, synthesis protocol scalability, environmental impact, manufacturing costs and so on.
National Center for Biotechnology Information , U. Journal List Int J Nanomedicine v. Int J Nanomedicine. Published online Jul Author information Copyright and License information Disclaimer. This work is published and licensed by Dove Medical Press Limited. By accessing the work you hereby accept the Terms. Non-commercial uses of the work are permitted without any further permission from Dove Medical Press Limited, provided the work is properly attributed. This article has been cited by other articles in PMC. Abstract Quantum dots QDs , also known as nanoscale semiconductor crystals, are nanoparticles with unique optical and electronic properties such as bright and intensive fluorescence.
Keywords: quantum dots, biomedical applications, nanoprobes, theranostic platforms. Introduction Quantum dots QDs , also known as nanoscale semiconductor crystals, were first described by Ekimov and Onushenko 1 in a glass matrix, back in , with the first biological imaging application reported in Imaging Although fluorescence imaging has been used in animal models, this approach is limited by the poor transmission of visible light through the biological tissue.
Open in a separate window. Figure 1. Drug delivery The development of diagnostic and treatment capabilities into one nanoparticle-based agent has been the focus of several groups. Figure 2. Figure 3. Sensors By employing the unique properties of QDs, new strategies for the identification and quantification of biological relevant molecules have been presented in the last years. Figure 4.
Figure 5. Toxicity The toxicity concerns regarding QDs are mainly related to their chemical composition, especially in the case of QD containing heavy metal ions such as Cd and Hg. Figure 6. Conclusion It is clear that QDs have great potential for applications in areas such as drug delivery, sensors and bio-imaging. Footnotes Disclosure The authors report no conflicts of interest in this work. References 1. Ekimov A, Onushenko AA. The quantum size effect in three-dimensional microscopic semiconductor.
JETP Lett. Environmental behaviour and ecotoxicity of quantum dots at various trophic levels: a review. Environ Int. Volkov Y. Quantum dots in nanomedicine: recent trends, advances and unresolvedissues.
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Biochem Biophys Res Commun. Recent research advances of antibody-conjugated quantum dots. Chin J Anal Chem. Fluorescent quantum dots: synthesis, biomedical optical imaging, and biosafety assessment. Colloids Surf B Biointerfaces. Fluorometric immunoassay for human serum albumin based on its inhibitory effect on the immunoaggregation of quantum dots with silver nanoparticles. Surface functionalization of quantum dots for biological applications. Adv Colloid Interface Sci. Influence of electric field ontheproperties of the polymer stabilized luminescent quantum dots in aqueous solutions.
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