Application of CdTe/ZnSe Quantum Dots inIn VitroImaging of Chicken Tissue and Embryo

Mercury (Hg2+) Detection in Aqueous Media, Photocatalyst, and Antibacterial Applications of CdTe/ZnS Quantum Dots

In the present work, CdTe/ZnS high luminescence quantum dots (QDs) were synthesized by a facile, fast, one-pot, and room temperature photochemical method. Synthesized QDs were characterized by different structural and optical analyses such as X-ray diffraction (XRD), energy dispersive X-ray spectroscopy (EDS), field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), Fourier transform-infrared spectroscopy (FT-IR), Raman, photoluminescence (PL) and UV-visible (UV-vis) spectroscopies. The results confirmed the successful growth of the ZnS shell and formation of CdTe/ZnS core/shell structure. CdTe/ZnS prepared QDs indicated a PL quantum yield of about 51%. These high luminescence QDs were used for detection of Hg²⁺ ions in aqueous media, as catalyst for photodegradation of different organic dyes, and as antibacterial material for the inhibition of bacterial growth. PL intensity of the CdTe/ZnS QDs was completely quenched after addition of 1 m molar Hg²⁺in to the media. Photocatalyst activity of CdTe/ZnS QDs was studied by rhodamine b, methylene blue, and methylene orange as organic dyes under both the sun and UV illuminations, and results showed that CdTe/ZnS QDs had the best photocatalyst activity for methylene blue degradation under UV irradiation and radical scavenger results indicated that electrons have a main role in photodegradation of methylene blue dye by CdTe/ZnS QDs under UV illumination. Antibacterial effects of CdTe/ZnS QDs evaluated by Minimum Inhibitory Concentration (MIC), and Minimum Bactericidal Concentration (MBC) methods against two strains of bacteria. The results of the antibacterial test showed that CdTe/ZnS could inhibit bacterial growth in Bacillus cereus (Gram-positive) and Escherichia coli (Gram-negative G) bacteria.

Effect of Pulsed Laser Frequency on CdTe Deposited as Solar Cells Device

In this paper, we discuss a new method for increasing the efficiency of cadmium telluride (CdTe) thin film solar cells (changing frequency in pulsed laser and knowing its effect on solar cells); using the pulse laser (power 800[Formula: see text]mJ), solar cells with (Al/Si/[Formula: see text]-Psi/CdTe/Al) structure were formed using the vacuum deposition method for three samples at various frequencies (4, 5, 6)[Formula: see text]Hz. X-ray diffraction was used to examine nanostructures ([Formula: see text]-Psi, CdTe) for structural, optical and morphological features, UV-Vis spectrophotometers and microscopy of atomic forces. The calculated thin film (CdTe) optical energy value was 2.15, 2.25 and 2.45[Formula: see text]eV accordingly. The test results showed that the solar cell’s highest energy conversion efficiency (PCE) was 2.73, 3.42 and 4.28%; this study reveals and examines the effective hybrid Perovskite solar cells based on porous silicone. With an increase in the frequency of pulsed laser, the efficiency of the prepared solar cells increased.

Effect of concentration and shell thickness on the optical behavior of aqueous CdTe/ZnSe core/shell quantum dots (QDs) exposed to ionizing radiation

In this work CdTe/ZnSe core/shell quantum dots (QDs) were synthesized via a simple, rapid and room temperature photochemical approach. Optical properties of aqueous prepared CdTe/ZnSe QDs were studied systematically under gamma irradiation with doses range of 0 Gy to 20 kGy. The obtained results showed a regular red shift behavior versus gamma irradiation dose, in PL peak and absorption edge of the CdTe/ZnSe QDs. Structural properties of CdTe/ZnSe QDs before and after gamma irradiation were characteristic by means of XRD, Raman and FT-IR analyses. The obtained results showed that the crystalline structure of CdTe/ZnSe core/shell QDs wasn't changed after gamma irradiation. Concentration and shell thickness as two important factors on the sensitivity of CdTe/ZnSe QDs in front of gamma irradiation have been investigated. Based on this study, CdTe/ZnSe QDs suggested as a good candidate for gamma dosimeter.

Quantitative comparison of luminescence probes for biomedical applications

Optical imaging holds great promise for the early-stage detection of diseases. It plays an important role in the process of protecting the patient's health. Most of the organic dyes suffer due to photobleaching, light scattering, short light penetration depth, and autofluorescence of specimen, thus, need to be replaced with alternative nanoprobes emitting light in the optical biological window (700-1350 nm). The group of candidates which can challenged described problems are colloidal quantum dots (e.g. CdSe and PbS) and upconverting nanocrystals (e.g. NaGdF₄:Er, Yb). This paper presents comprehensive and systematic studies of the aforementioned probes, using specially designed tissue phantom, and custom-built wide-field fluorescence microscope. We investigated how the absorption and scattering of light at the water, hemoglobin, and intralipid may affect the intensity of luminescence probes and the quality of optical images. We propose a protocol, that could be easily implemented for investigating other nanoprobes that allow for comparison of their optical performance.

Mitochondrial dynamics and mitophagy involved in MPA-capped CdTe quantum dots-induced toxicity in the human liver carcinoma (HepG2) cell line

Quantum dots (QDs) are nanoparticles of inorganic semiconductors and have great promise in various applications. Many studies have indicated that mitochondria are the main organelles for the distribution and toxic effects of QDs. However, the underlying mechanism of QDs interacting with mitochondria and affecting their function is unknown. Here, we report the mechanism of toxic effects of 3-mercaptopropionic acid (MPA)-capped CdTe QDs on mitochondria. Human liver carcinoma (HepG2) cells were exposed to 25, 50 and 100 μmol/L of MPA-capped CdTe QDs. The results indicated that MPA-capped CdTe QDs inhibited HepG2 cell proliferation and increased the extracellular release of LDH in a concentration-dependent manner. Furthermore, MPA-capped CdTe QDs caused reactive oxygen species (ROS) generation and cell damage through intrinsic apoptotic pathway. MPA-capped CdTe QDs can also lead to the destruction of mitochondrial cristae, elevation of intracellular Ca²⁺ levels, decreased mitochondrial transmembrane potential and ATP production. Finally, we showed that MPA-capped CdTe QDs inhibited mitochondrial fission, mitochondrial inner membrane fusion and mitophagy. Taken together, MPA-capped CdTe QDs induced significant mitochondrial dysfunction, which may be caused by imbalanced mitochondrial fission/fusion and mitophagy inhibition. These findings provide insights into the regulatory mechanisms involved in MPA-capped CdTe QDs-induced mitochondrial dysfunction.

Study of Physico-Chemical Changes of CdTe QDs after Their Exposure to Environmental Conditions

The irradiance of ultraviolet (UV) radiation is a physical parameter that significantly influences biological molecules by affecting their molecular structure. The influence of UV radiation on nanoparticles has not been investigated much. In this work, the ability of cadmium telluride quantum dots (CdTe QDs) to respond to natural UV radiation was examined. The average size of the yellow QDs was 4 nm, and the sizes of green, red and orange QDs were 2 nm. Quantum yield of green CdTe QDs-MSA (mercaptosuccinic acid)-A, yellow CdTe QDs-MSA-B, orange CdTe QDs-MSA-C and red CdTe QDs-MSA-D were 23.0%, 16.0%, 18.0% and 7.0%, respectively. Green, yellow, orange and red CdTe QDs were replaced every day and exposed to daily UV radiation for 12 h for seven consecutive days in summer with UV index signal integration ranging from 1894 to 2970. The rising dose of UV radiation led to the release of cadmium ions and the change in the size of individual QDs. The shifts were evident in absorption signals (shifts of the absorbance maxima of individual CdTe QDs-MSA were in the range of 6–79 nm), sulfhydryl (SH)-group signals (after UV exposure, the largest changes in the differential signal of the SH groups were observed in the orange, green, and yellow QDs, while in red QDs, there were almost no changes), fluorescence, and electrochemical signals. Yellow, orange and green QDs showed a stronger response to UV radiation than red ones.

A Novel Biocompatible Titanium-Gadolinium Quantum Dot as a Bacterial Detecting Agent with High Antibacterial Activity

In this study, the titanium–gadolinium quantum dots (TGQDs) were novel, first of its type to be synthesized, and fully characterized to date. Multiple physical characterization includes scanning electron microscopy (SEM), scanning electrochemical microscope (SCEM), x-ray fluorescence, spectrophotometry, and dynamic light scattering were carried out. The obtained results confirmed appropriate size and shape distributions in addition to processing optical features with high quantum yield. The synthesized TGQD was used as a fluorescent dye for bacterial detection and imaging by fluorescent microscopy and spectrophotometry, where TGQD stained only bacterial cells, but not human cells. The significant antibacterial activities of the TGQDs were found against a highly pathogenic bacterium (Staphylococcus aureus) and its antibiotic resistant strains (vancomycin and methicillin resistant Staphylococcus aureus) using growth curve analysis and determination of minimum inhibitory concentration (MIC) analysis. Live/dead cell imaging assay using phase-contrast microscope was performed for further confirmation of the antibacterial activity. Cell wall disruption and release of cell content was observed to be the prime mode of action with the reduction of cellular oxygen demand (OD).

A Novel Ruthenium Based Coordination Compound Against Pathogenic Bacteria

The current epidemic of antibiotic-resistant infections urges to develop alternatives to less-effective antibiotics. To assess anti-bacterial potential, a novel coordinate compound (RU-S4) was synthesized using ruthenium-Schiff base-benzimidazole ligand, where ruthenium chloride was used as the central atom. RU-S4 was characterized by scanning electron microscope (SEM), energy-dispersive X-ray spectroscopy (EDS), and Raman spectroscopy. Antibacterial effect of RU-S4 was studied against Staphylococcus aureus (NCTC 8511), vancomycin-resistant Staphylococcus aureus (VRSA) (CCM 1767), methicillin-resistant Staphylococcus aureus (MRSA) (ST239: SCCmecIIIA), and hospital isolate Staphylococcus epidermidis. The antibacterial activity of RU-S4 was checked by growth curve analysis and the outcome was supported by optical microscopy imaging and fluorescence LIVE/DEAD cell imaging. In vivo (balb/c mice) infection model prepared with VRSA (CCM 1767) and treated with RU-S4. In our experimental conditions, all infected mice were cured. The interaction of coordination compound with bacterial cells were further confirmed by cryo-scanning electron microscope (Cryo-SEM). RU-S4 was completely non-toxic against mammalian cells and in mice and subsequently treated with synthesized RU-S4.

CdSe QD Biosynthesis in Yeast Using Tryptone-Enriched Media and Their Conjugation with a Peptide Hecate for Bacterial Detection and Killing

The physical and chemical synthesis methods of quantum dots (QDs) are generally unfavorable for biological applications. To overcome this limitation, the development of a novel "green" route to produce highly-fluorescent CdSe QDs constitutes a promising substitute approach. In the present work, CdSe QDs were biosynthesized in yeast Saccharomyces cerevisiae using a novel method, where we showed for the first time that the concentration of tryptone highly affects the synthesis process. The optimum concentration of tryptone was found to be 25 g/L for the highest yield. Different methods were used to optimize the QD extraction from yeast, and the best method was found to be by denaturation at 80 °C along with an ultrasound needle. Multiple physical characterizations including transmission electron microscopy (TEM), dynamic light scattering (DLS), energy-dispersive X-ray spectroscopy (EDX), and spectrophotometry confirmed the optical features size and shape distribution of the QDs. We showed that the novel conjugate of the CdSe QDs and a cell-penetrating peptide (hecate) can detect bacterial cells very efficiently under a fluorescent microscope. The conjugate also showed strong antibacterial activity against vancomycin-resistant Staphylococcus aureus (VRSA), methicillin-resistant Staphylococcus aureus (MRSA), and Escherichia coli, which may help us to cope with the problem of rising antibiotic resistance.

Antioxidant, gene expression and metabolomics fingerprint analysis of Arabidopsis thaliana treated by foliar spraying of ZnSe quantum dots and their growth inhibition of Agrobacterium tumefaciens

Nanotechnology, new fascinating field of science, is bringing many application's options. However, it is necessary to understand their potential environmental risk and toxicity. Zinc selenide quantum dots (ZnSe QDs) are getting valuable due to wide industrial usage, mainly as cadmium free diodes or stabilizing ligand. Thanks to unique properties, they could also open the possibilities of application in the agriculture. Their effects on living organisms, including plants, are still unknown. Therefore, the attention of this work was given to antioxidant response of Arabidopsis thaliana to 100 and 250 μM ZnSe QDs foliar feeding. ZnSe QDs treatment had no statistically significant differences in morphology but led to increased antioxidant response in the leaves at the level of gene expression and production secondary antioxidant metabolites. Concurrently, analysis of growth properties of Agrobacterium tumefaciens was done. 250 μM ZnSe solution inhibited the Agrobacterium tumefaciens viability by 60%. This is the first mention about effect ZnSe QDs on the plants. Although QDs induced oxidative stress, the apply treatment dose of ZnSe QDs did not have significant toxic effect on the plants and even no morphological changes were observed. However, the same amount of ZnSe QD induced an inhibitory effect on Agrobacterium tumefaciens.

Real-Time Visualization of Cell Membrane Damage Using Gadolinium-Schiff Base Complex-Doped Quantum Dots

Despite the importance of cell membranes for maintenance of integrity of cellular structures, there is still a lack of methods that allow simple real-time visualization of their damage. Herein, we describe gadolinium-Schiff base-doped quantum dots (GdQDs)-based probes for a fast facile spatial labeling of membrane injuries. We found that GdQDs preferentially interact through electron-rich and hydrophobic residues with a specific sequence motif of NHE-RF2 scaffold protein, exposed upon membrane damage. Such interaction results in a fast formation of intensively fluorescent droplets with a higher resolution and in a much shorter time compared to immunofluorescence using organic dye. GdQDs have high stability, brightness, and considerable cytocompatibility, which enable their use in long-term experiments in living cultures. To the best of our knowledge, this is the first report, demonstrating a method allowing real-time monitoring of membrane damage and recovery without any special requirements for instrumentation. Because of intensive brightness and simple signal pattern, GdQDs allow easy examination of interactions between cellular membranes and cell-penetrating peptides or cytostatic drugs. We anticipate that the simple and flexible method will also facilitate the studies dealing with host-pathogen interactions.

Improving cytocompatibility of CdTe quantum dots by Schiff-base-coordinated lanthanides surface doping

Background

Suitable fluorophores are the core of fluorescence imaging. Among the most exciting, yet controversial, labels are quantum dots (QDs) with their unique optical and chemical properties, but also considerable toxicity. This hinders QDs applicability in living systems. Surface chemistry has a profound impact on biological behavior of QDs. This study describes a two-step synthesis of QDs formed by CdTe core doped with Schiff base ligand for lanthanides [Ln (Yb³⁺, Tb³⁺ and Gd³⁺)] as novel cytocompatible fluorophores.

Results

Microwave-assisted synthesis resulted in water-soluble nanocrystals with high colloidal and fluorescence stability with quantum yields of 40.9–58.0%. Despite induction of endocytosis and cytoplasm accumulation of Yb- and TbQDs, surface doping resulted in significant enhancement in cytocompatibility when compared to the un-doped CdTe QDs. Furthermore, only negligible antimigratory properties without triggering formation of reactive oxygen species were found, particularly for TbQDs. Ln-doped QDs did not cause observable hemolysis, adsorbed only a low degree of plasma proteins onto their surface and did not possess significant genotoxicity. To validate the applicability of Ln-doped QDs for in vitro visualization of receptor status of living cells, we performed a site-directed conjugation of antibodies towards immuno-labeling of clinically relevant target—human norepinephrine transporter (hNET), over-expressed in neuroendocrine tumors like neuroblastoma. Immuno-performance of modified TbQDs was successfully tested in distinct types of cells varying in hNET expression and also in neuroblastoma cells with hNET expression up-regulated by vorinostat.

Conclusion

For the first time we show that Ln-doping of CdTe QDs can significantly alleviate their cytotoxic effects. The obtained results imply great potential of Ln-doped QDs as cytocompatible and stable fluorophores for various bio-labeling applications.

Using CdTe/ZnSe core/shell quantum dots to detect DNA and damage to DNA

CdTe/ZnSe core/shell quantum dot (QD), one of the strongest and most highly luminescent nanoparticles, was directly synthesized in an aqueous medium to study its individual interactions with important nucleobases (adenine, guanine, cytosine, and thymine) in detail. The results obtained from the optical analyses indicated that the interactions of the QDs with different nucleobases were different, which reflected in different fluorescent emission maxima and intensities. The difference in the interaction was found due to the different chemical behavior and different sizes of the formed nanoconjugates. An electrochemical study also confirmed that the purines and pyrimidines show different interactions with the core/shell QDs. Based on these phenomena, a novel QD-based method is developed to detect the presence of the DNA, damage to DNA, and mutation. The QDs were successfully applied very easily to detect any change in the sequence (mutation) of DNA. The QDs also showed their ability to detect DNAs directly from the extracts of human cancer (PC3) and normal (PNT1A) cells (detection limit of 500 pM of DNA), which indicates the possibilities to use this easy assay technique to confirm the presence of living organisms in extreme environments.

Comparative study on toxicity of extracellularly biosynthesized and laboratory synthesized CdTe quantum dots

Nanobiosynthesis belongs to the most recent methods for synthesis of nanoparticles. This type of synthesis provides many advantages including the uniformity in particle shape and size. The biosynthesis has also a significant advantage regarding chemical properties of the obtained particles. In this study, we characterized the basic properties and composition of quantum dots (QDs), obtained by the extracellular biosynthesis by Escherichia coli. Furthermore, the toxicity of the biosynthesized QDs was compared to QDs prepared by microwave synthesis. The obtained results revealed the presence of cyan CdTe QDs after removal of substantial amounts of organic compounds, which stabilized the nanoparticle surface. QDs toxicity was evaluated using three cell lines Human Foreskin Fibroblast (HFF), Human Prostate Cancer cells (PC-3) and Breast Cancer cells (MCF-7) and the MTT assay. The test revealed differences in the toxicity between variants of QDs, varying about 10% in the HFF and 30% in the MCF-7 cell lines. The toxicity of the biosynthesized QDs to the PC-3 cell lines was about 35% lower in comparison with the QDs prepared by microwave synthesis.