Uptake Of Quantum Dots Research Articles

Facile green synthesis of dual stabilized near-infrared CuInSe/ZnS quantum dots as fluorescent probes for cancer-bacteria imaging

Imaging is a critical step in diagnosis and therapy; thus, developing a non-carcinogenic near-infrared (NIR) emitting probe for guided therapy remains a priority for effective bacteria and cancer treatment. Herein, we report the effect of dual stabilization in producing NIR fluorescent CuInSe/ZnS quantum dots (QDs) and their use as imaging probes in cancer-bacteria therapy. The as-synthesised NIR QDs were stabilized using different combinations of hydrophilic dual capping agents, MPA-Gelatine, TGA-Gelatine, MPA-Citrate and TGA-Citrate. The optical characteristics of the prepared dual-stabilized CuInSe/ZnS QDs indicate that the material has high stability and fluorescence quantum yield. The dual stabilization resulted in varied emission positions as well as fluorescence intensity for the as-synthesized QDs. The cytotoxicity evaluation showed that cells treated with dual stabilised CuInSe/ZnS QDs displayed good cell viability against malignant fibrous histiocytoma-like (KM-Luc/GFP) cells, mouse colon carcinoma (C26) cells and mouse mammary carcinoma (FM3A-Luc) cells. It also showed high affinity to prostate and human adenocarcinoma cells with no indication of QDs uptake by normal prostate cells. The biofilm analysis showed that the QDs uptake was elevated in Staphylococcus aureus (Gram-positive bacteria) than in Escherichia coli (Gram-negative bacteria). The dual stabilized QDs remain a promising study as future fluorescence probes for early diagnosis and guided cancer therapy.

Peptide-functionalized graphene oxide quantum dots as colorectal cancer theranostics

Colorectal cancer (CRC) accounts for approximately 10% of all new cancer cases worldwide with significant morbidity and mortality. The current imaging techniques are lacking diagnostic precision while traditional chemotherapeutic strategies are limited by their adverse side effects and poor response in advanced stages. Targeted nanoparticles (NPs) can specifically bind to surface antigens on cancer cells and provide effective delivery of diagnostic and chemotherapeutic agent. Placenta-specific protein 1 (PLAC-1) is overexpressed in CRC and can be used as a target for detection and treatment of the disease. The aim of this work was to develop a targeted nanotheranostic agent for early diagnosis and inhibition of the malignant progression and metastasis of CRC. Graphene oxide quantum dots (QD) were covalently labeled with a peptide (GILGFVFTL) having high affinity to PLAC-1. The covalent coupling between the QD and the peptide was confirmed using a series of physicochemical and morphological characterization techniques. Confocal microscopy was used to evaluate the uptake of QD and QD-P in HCT-29, HT-116 and LS-180 CRC cell lines. Selective targeting of antigen PLAC-1 overexpressed on HT-29 and HCT-116 cells was measured by immunofluorescence. Cell proliferation, cell invasion and extent of PLAC-1 expression in CRC cells after treatment with QD and QD-P were determined. The prepared QD-P showed a significant increase in targeting and specific uptake in cells expressing the antigen PLAC-1 compared to non-functionalized QD. Treatment with QD-P also increased the cell cytotoxicity, reduced the invasiveness of HT-29 and HCT-116 cells by 38% and 62%, respectively, and downregulated the expression of PLAC-1 by 53% and 33%, respectively. These results highlight the potential use of QD-P as a theranostic agent for the detection and treatment of CRC cells expressing the antigen PLAC-1.

Caveolae-dependent endocytosis mediates the cellular uptake of CdTe quantum dots in ovarian cancer cell lines.

Quantum dots (QDs) are semiconductor nanocrystals that are widely used in biology due to their good optical properties. QDs, especially cadmium-based QDs, play an important role in the diagnosis and treatment of cancer due to their intrinsic fluorescence. The aim of the present study was the evaluation of the cellular uptake mechanisms of CdTe QDs in ovarian cancer cell lines. In this study, we used CdTe QDs coated with thioglycolic acid. The ovarian cancer cell lines SKOV3 and OVCAR3 were treated with different concentrations of QDs, triamterene, chlorpromazine, and nystatin, and cell viability was evaluated through the MTT test. To find the way of cellular uptake of CdTe QDs, we used the MTT test and interfering compounds in endocytic pathways. Intrinsic fluorescence and cellular internalization of CdTe QDs were assessed using flow cytometry and fluorescence microscopy imaging. The viability of CdTe QDs-treated cells dose-dependently decreased in comparison to untreated cells. To evaluate the cellular uptake pathways of CdTe QDs, in most cases, a significant difference was observed when the cells were pretreated with nystatin. The results of flow cytometry showed the cellular uptake of CdTe QDs was dose- and time-dependent. Nystatin had a measurable effect on the cellular uptake of CdTe QDs. This finding suggests that caveola-mediated endocytosis has a large portion on the internalization of CdTe QDs. According to the results of this study, CdTe QDs may have potential applications in cancer research and diagnosis.

Light-Driven Ammonia Production by Azotobacter vinelandii Cultured in Medium Containing Colloidal Quantum Dots.

There is an evergrowing demand for environment-friendly processes to synthesize ammonia (NH3) from atmospheric nitrogen (N2). Although diazotrophic N2 fixation represents an undeniably "green" process of NH3 synthesis, the slow reaction rate makes it less suitable for industrially meaningful large-scale production. Here, we report the photoinduced N2 fixation using a hybrid system composed of colloidal quantum dots (QDs) and aerobic N2-fixing bacteria, Azotobacter vinelandii. Compared to the case where A. vinelandii cells are simply mixed with QDs, NH3 production increases significantly when A. vinelandii cells are cultured in the presence of core/shell InP/ZnSe QDs. During the cell culture of A. vinelandii, the cellular uptake of QDs is facilitated in the exponential growth phase. Experimental results as well as theoretical calculations indicate that the photoexcited electrons in QDs within A. vinelandii cells are directly transferred to MoFe protein, the catalytic component of nitrogenase. We also observe that the excess amount of QDs left on the outer surface of A. vinelandii disrupts the cellular membrane, leading to the decrease in NH3 production due to the deactivation of nitrogenase. The successful uptake of QDs in QD-A. vinelandii hybrid with minimal amount of QDs on the outer surface of the bacteria is key to efficient photosensitized NH3 production. The comprehensive understanding of the QD-bacteria interface paves an avenue to novel and efficient nanobiohybrid systems for chemical production.

Silica-coated graphene compared to Si-CdSe/ZnS quantum dots: Toxicity, emission stability, and role of silica in the uptake process for imaging purposes

Quantum dots (QDs) present a special type of nanocrystals (NCs) due to their unique optical and chemical properties. While cadmium-based QDs (Cd-QDs) have the most favorable physicochemical properties, their toxicity, instability in the aqueous phase, and loss of brightness at high temperature are some of the obstacles that prevent the wide use of Cd-QDs. Carbon-based QDs as graphene quantum dots (GQDs) represent a very promising biocompatible replacement. In the present work, we mainly focus on comparing the efficiency and uptake of GQDs and Cd-QDs for fluorescent imaging purposes and studying the effect of growing silica shell on the emission and the uptake of QDs inside living human and bacterial cells. Graphene and CdSe/ZnS QDs were prepared and encapsulated in silica to increase their emission and uptake by living cells. Moreover, we studied their photostability and cytotoxicity. The Prepared G-Si QDs showed good emission inside the cytoplasmic portion of the liver hepatocellular carcinoma cell line (HepG2) and Bacillus subtilis (B. subtilis), but they revealed lower photoluminescence (PL) intensity compared to Si-CdSe/ZnS NCs although G-Si QDs are advantageous in other aspects, i.e. possess lower toxicity and higher stability with temperature variations.

Monitoring the Cd2+ release from Cd-containing quantum dots in simulated body fluids by size exclusion chromatography coupled with ICP-MS.

Quantification of Cd2+ release from Cd-containing quantum dots (QDs) is of fundamental importance to elucidate its toxicity to organisms, but remains a great challenge due to the lack of appropriate analytical method. Herein, a facile method based on size exclusion chromatography (SEC) combined with inductively coupled plasma mass spectrometry (ICP-MS) was developed for separating and quantifying the QDs and counterpart ions. By using the mixture of sodium dodecyl sulfate (SDS) and ethylenediaminetetraacetic acid tetrasodium salt (EDTA) as the mobile phase, the defect of QD and ion adsorption onto the SEC column was overcome, thus realizing the accurate quantification of ionic species. Besides, the concentration of QDs was achieved through subtracting the ion concentration from the total concentration. Selecting CdSe@ZnS as the typical QDs, the Cd2+ release process in four typical simulated body fluids, namely, simulated gastric fluid, simulated sweat, Gamble's solution, and artificial lysosomal fluid, was monitored using the developed SEC-ICP-MS method. The media pH is identified as the decisive factor which controls the dissolution of ZnS shells and also the Cd2+ release kinetics and final concentration. Our results suggest that the oral pathway for QD uptake poses the biggest risk to human health.

Systematic toxicity assessment of CdTe quantum dots in Drosophila melanogaster

The risk assessment of cadmium (Cd)-based quantum dots (QDs) used for biomedical nanotechnology applications has stern toxicity concerns. Despite cytotoxicity studies of cadmium telluride (CdTe) QDs, the systematic in vivo study focusing on its organismal effects are more relevant to public health. Therefore, the present study aims to investigate the effect of chemically synthesized 3-mercapto propionic acid-functionalized CdTe QDs on organisms’ survival, development, reproduction, and behaviour using Drosophila melanogaster as a model. The sub-cellular impact on the larval gut was also evaluated. First/third instar larvae or the adult Drosophila were exposed orally to green fluorescence emitting CdTe QDs (0.2–100 μM), and organisms' longevity, emergence, reproductive performance, locomotion, and reactive oxygen species (ROS), and cell death were assessed. Uptake of semiconductor CdTe QDs was observed as green fluorescence in the gut. A significant decline in percentage survivability up to 80% was evident at high CdTe QDs concentrations (25 and 100 μM). The developmental toxicity was marked by delayed and reduced fly emergence after CdTe exposure. The teratogenic effect was evident with significant wing deformities at 25 and 100 μM concentrations. However, at the reproductive level, adult flies' fecundity, fertility, and hatchability were highly affected even at low concentrations (1 μM). Surprisingly, the climbing ability of Drosophila was unaffected at any of the used CdTe QDs concentrations. In addition to organismal toxicity, the ROS level and cell death were elevated in gut cells, confirming the sub-cellular toxicity of CdTe QDs. Furthermore, we observed a significant rescue in CdTe QDs-associated developmental, reproductive, and survival adversities when organisms were co-exposed with N-acetyl-cysteine (NAC, an antioxidant) and CdTe QDs. Overall, our findings indicate that the environmental release of aqueously dispersible CdTe QDs raises a long-lasting health concern on the development, reproduction, and survivability of an organism.

Cytotoxicity and transcriptome changes triggered by CuInS2/ZnS quantum dots in human glial cells

As a newly developed cadmium-free quantum dot (QD), CuInS2/ZnS has great application potential in many fields, but its biological safety has not been fully understood. In this study, the in vitro toxicity of CuInS2/ZnS QDs on U87 human glioma cell line was explored. The cells were treated with different concentrations of QDs (12.5, 25, 50 and 100 μg/mL), and the uptake of QDs by the U87 cells was detected by fluorescence imaging and flow cytometry. The cell viability was observed by MTT assay, and the gene expression profile was analyzed by transcriptome sequencing. These results showed that QDs could enter the cells and mainly located in the cytoplasm. The uptake rate was over 90 % when the concentration of QDs reached 25 μg/mL. The cell viability (50 and 100 μg/mL) increased at 24 h (P < 0.05), but no significant difference after 48 h and 72 h treatment. The results of differential transcription showed that coding RNA accounted for the largest proportion (62.15 %), followed by long non-coding RNA (18.65 %). Total 220 genes were up-regulated and 1515 genes were down-regulated, and significantly altered gene functions included nucleosome, chromosome-DNA binding, and chromosome assembly. In conclusion, CuInS2/ZnS QDs could enter U87 cells, did not reduce the cell viability, but would obviously alter the gene expression profile. These findings provide valuable information for a proper understanding of the toxicity risk of CuInS2/ZnS QD and promote the rational utilization of QDs in the future.

Imaging of the internal chorion structure of rainbow trout Oncorhynchus mykiss live embryos and the distribution of quantum dots therein: Towards a deeper understanding of potential nanotoxicity

Quantum dots (QDs) are extensively explored in biomedicine but the understanding of the mechanism underlying the uptake of colloidal QDs by biological systems is still poor. The knowledge of their distribution in tissues and their possibilities to cross biological barriers, especially at early stages of organism development, is also still limited. The potential risk of nanoparticle exposure to aquatic organisms is continuously questioned in ecotoxicology. To answer this question, we investigated the interaction (penetration and distribution) of CdSe/ZnS-COOH QDs with the chorion as well as their toxicity, cytotoxicity and genotoxicity in “eye-egg” stage embryos of rainbow trout Oncorhynchus mykiss. Results of the confocal fluorescence microscopy, fluorescence spectroscopy and 3D image analysis of O. mykiss chorion showed that it consists of three different layers and has a hexagonal pattern of pores distribution. The present study has revealed that both the accumulation and the distribution of QDs within the chorion are related to its structure. QDs are accumulated in pore canals of the external membrane of a fertilized O. mykiss egg. Our study has shown that QDs exposure induces bradycardia in O. mykiss and, as a result, cardiac toxicity in embryos. However, embryo survival rates as well as cytotoxicity and genotoxicity effects in the fish exposed to QDs for 1 day were not found to differ significantly from those in 4-day exposed fish. Results of the mathematical modelling showed the adsorption of QDs aggregates on the outer surface of the chorion leading to the oxygen-deficient microenvironment in embryos. These results represent an important step forward towards a better understanding of the mechanisms underlying QDs impacts on living organisms, which is essential for clarifying the protective properties of biological structures, and is valuable for the evaluation of nanotoxicity to fish at early development stages.

Quantifying Nutrient Trade in the Arbuscular Mycorrhizal Symbiosis Under Extreme Weather Events Using Quantum-Dot Tagged Phosphorus

Given the current trends in climate change, extreme weather events are expected to increase in strength and frequency. Such events can impact species survival and species interactions. One of the most ubiquitous symbioses on earth is the nutrient exchange partnership between arbuscular mycorrhizal fungi and their host plants. While past work has shown that mycorrhizal fungi can help alleviate stress, it is unknown how phosphorus uptake by plants to fungi is affected by extreme weather events, such as flooding and heat waves. To test this response, we grewMedicago truncatulahost plants with or without mycorrhizal fungi and then exposed them to extreme weather treatments: increasing soil temperature by 12°C, or by flooding the plant roots for 7 days. We measured plant and fungal performance, and quantified phosphorus (P) uptake before and after extreme weather treatments using a technique in which we tagged apatite, a form of rock phosphorus, with fluorescing quantum-dots (QDs) nanoparticles. We then measured fluorescence in root and shoot tissue at harvest. We found that plants and arbuscular mycorrhizal fungi were affected by soil flooding, with plant survival, fungal colonization and QD-apatite uptake decreasing under flooded conditions. We did not see these negative effects in the heat treatment. While the presence of arbuscular mycorrhizal fungi affected plant biomass allocation, leading to an increase in shoot biomass, the symbiosis did not increase plant survival, total biomass or QD uptake in either treatment. More generally, we found host tissue contained roughly 80% more QD-apatite from the pre-treatment compared to the post-treatment nutrient injection. Future studies should focus on various plant-fungal combinations to create databases on which predictive models to extreme weather events can be constructed.

Quantum Dots as a Good Carriers of Unsymmetrical Bisacridines for Modulating Cellular Uptake and the Biological Response in Lung and Colon Cancer Cells.

Nanotechnology-based drug delivery provides a promising area for improving the efficacy of cancer treatments. Therefore, we investigate the potential of using quantum dots (QDs) as drug carriers for antitumor unsymmetrical bisacridine derivatives (UAs) to cancer cells. We examine the influence of QD–UA hybrids on the cellular uptake, internalization (Confocal Laser Scanning Microscope), and the biological response (flow cytometry and light microscopy) in lung H460 and colon HCT116 cancer cells. We show the time-dependent cellular uptake of QD–UA hybrids, which were more efficiently retained inside the cells compared to UAs alone, especially in H460 cells, which could be due to multiple endocytosis pathways. In contrast, in HCT116 cells, the hybrids were taken up only by one endocytosis mechanism. Both UAs and their hybrids induced apoptosis in H460 and HCT116 cells (to a greater extent in H460). Cells which did not die underwent senescence more efficiently following QDs–UAs treatment, compared to UAs alone. Cellular senescence was not observed in HCT116 cells following treatment with both UAs and their hybrids. Importantly, QDgreen/red themselves did not provoke toxic responses in cancer or normal cells. In conclusion, QDs are good candidates for targeted UA delivery carriers to cancer cells while protecting normal cells from toxic drug activities.

Exploring quantitative cellular bioimaging and assessment of CdSe/ZnS quantum dots cellular uptake in single cells, using ns-LA-ICP-SFMS

Quantitative bioimaging of Quantum Dots (QDs) uptake in single cells by laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) is a challenging task due to the high sensitivity and high spatial resolution required, and to the lack of matrix-matched reference materials. In this work, high spatially resolved quantitative bioimaging of CdSe/ZnS QDs uptake in single HT22 mouse hippocampal neuronal cells and in single HeLa human cervical carcinoma cells is novelty investigated combining: (a) the use of a ns-LA-ICP-Sector Field (SF)MS unit with mono-elemental fast and sensitive single pulse response for 114Cd+; and (b) the spatially resolved analysis of dried pL-droplets from a solution with a known concentration of these QDs to obtain a response factor that allows quantification of elemental bioimages. Single cells and dried pL-droplets are morphologically characterized by Atomic Force Microscopy (AFM) to determine their volume and thickness distribution. Moreover, operating conditions (e.g. spot size, energy per laser pulse, etc.) are optimized to completely ablate the cells and pL droplets at high spatial resolution. Constant operating conditions for the analysis of the single cells and calibrating samples is employed to reduce potential fractionation effects related to mass load effects in the ICP. A number concentration of CdSe/ZnS QDs between 3.5 104 and 48 104 is estimated to be uptaken by several selected single HT22 and HeLa cells, after being incubated in the presence of a QDs suspension added to a standard cell culture medium. Mono-elemental bioimaging at subcellular resolution seems to show a higher number concentration of the CdSe/ZnS QDs in the cytosol around the cell nucleus.

Changes in the Fluorescence Characteristics of Quantum Dots Based on InP/ZnS during the Interaction with Cells

Semiconductor quantum dots (QDs), due to their unique spectral-luminescent properties, are attractive for visualizing biological objects in biological and medical research. The main methods for registering luminescent QDs in the cells are various types of scanning microscopy. It is important to note that during the use of QDs, they are delivered into different extracellular and intracellular environments, which can affect the surface integrity of QDs and, as a result, the photophysical characteristics of QDs. In this connection, changes in the characteristics of the luminescence signals of non-target QDs based on InP/ZnS, coated with polyethylene glycol with COOH-groups, were studied, which can reduce the risk of toxic effects in the process of biological and medical research. In this work, QDs-InP accumulated in endosomes of A549 cultured cells. Analysis of the photophysical properties of QDs showed that the average intensity of QDs in endosomes was lower than the intensity of clusters outside the cells, which can be explained by a lower concentration of QDs in intracellular clusters. However, the QDs luminescence lifetime in clusters, independent of concentration, was also 5–10 ns lower. Analysis of the QDs solution showed that a decrease in the quantum yield and QDs luminescence lifetimes is observed in solution with pH 4.0, but not 7.4–8.0. Also, the process of significant formation of QDs aggregates in such solutions was not revealed. In this connection, changes in the photophysical properties of QDs interacting with cells, can be associated with the entry into endosomes with a low pH level. Thus, the analysis of the luminescence lifetimes of QDs allows to obtain additional information about their state in comparison with the determination of the fluorescence intensity. Our results are important for an adequate interpretation of data concerning both the efficiency of QDs uptake and analysis of the properties of intracellular compartments in which QDs accumulate.

Current Status and Future Prospects of Semiconductor Quantum Dots in Botany.

The development of botanical applications of nanomaterials has produced a new generation of technologies that can profoundly impact botanical research. Semiconductor quantum dots (QDs) are an archetype nanomaterial and have received significant interest from diverse research communities, owing to their unique and optimizable optical properties. In this review, we describe the most recent progress on QD-based botanical research and discuss the uptake, translocation, and effects of QDs on plants and the potential applications of QDs in botany. A critical evaluation of the current limitations of QD technologies is discussed, along with the future prospects in QD-based botanical research.

Exploring the conformational changes in fibrinogen by forming protein corona with CdTe quantum dots and the related cytotoxicity.

This study describes synthesis of N‑acetyl‑l‑cysteine-capped CdTe quantum dots (QDs) and investigates their interaction with plasma protein fibrinogen (FIB) and the structural changes of FIB. It is shown that the interaction of QDs with FIB is a spontaneous process and the major driving forces are van der Waals forces and hydrogen bonds. Multi-spectroscopic measurements show that the intrinsic fluorescence of FIB was quenched and secondary and tertiary structures were altered due to the interaction with QDs. In addition, the aggregation state of FIB was altered in the presence of QDs. Furthermore, the formed complexes of FIB with QDs reduced the cytotoxicity of QDs. The coating of FIB on QDs could lower intracellular QDs uptake and therefore result in less released cadmium ions and ROS productions. This study, therefore, might be helpful to the comprehensive understanding of QDs toxicity and provide evidence for assessing the safe application of nanoparticles.

The targeting ability of fluorescent quantum dots to the folate receptor rich tumors.

Quantum dots (QDs) bring new insights in cancer theranostics. Exceptional brightness together with the simple possibility to modify surface with targeting molecules make QDs attractive agents in fluorescence guided surgery and photodynamic therapy. Currently, many targeted QDs have been developed for theranostic purpose. However, their targeting ability was tested mainly in two dimensional monolayer tumor cell models, while our study includes 3D tumor model reflecting the specificity of in vivo tumor environment. Core/multilayer shell CdSe/CdS/ZnS QDs were conjugated with folic acid (FA) and characterized spectroscopically. Cytotoxicity of QDs on KB and A549 cells lines were evaluated using the MTT assay. Cellular uptake of QDs was assessed by epifluorescent microscopy. To study the distribution of QDs in tumor tissue, KB spheroids were prepared by means of the liquid overlay technique and then frozen cut of spheroids treated with QDs were imaged by epifluorescence microscopy. We confirmed the specificity of QD-FA for the folic acid receptor positive KB cells. In 3D tumor spheroid model we demonstrated uptake enhancement of QD-FA compared with non-targeted QD. It was demonstrated that penetration profiles were similar for both QDs with penetration depth never exceeding 100 μm. We have demonstrated the effectiveness of FA conjugated QDs to target tumor spheroids thus confirming the crucial role of FRα receptor as a target. Further improvement of QD-FA targeting ability could be performed using dual targeting different targeting agents, such as FA and cyclic RGD.

Surface coating determines the response of soybean plants to cadmium sulfide quantum dots

Quantum dots (QDs) are used in an array of applications from electronic devices to medicine, leading to environmental release and accumulation in landfills and agricultural soils. However, their effects on plants have been least studied among other engineered nanomaterials. In the current study, soybean seedlings were exposed to 50–200 mg/L cadmium sulfide quantum dots (CdS-QDs) to elucidate their bioaccumulation and biological response in comparison to Cd2+ ions and bulk-CdS. To understand the role of surface coatings on QD stability, uptake, translocation, subcellular localization and cellular response, bare CdS-QDs were capped with ligands varying in polarity and surface charge. Four common ligands, including trioctylphosphine oxide, polyvinylpyrrolidone, mercaptoacetic acid, and glycine were used to synthesize QD-TOPO, QD-PVP, QD-MAA, and QD-GLY, respectively. In aqueous suspension, QD-MAA particles were most stable, maintaining their size at 332 nm with least Cd2+ dissolution (9%) after 14 d, whereas QD-TOPO formed large aggregates of size 3861 nm with 27% Cd2+ dissolution. Upon exposure to 100 mg/L bare and coated CdS-QDs in vermiculite for 14 d, soybean roots accumulated Cd, ranging from 568 (QD-MAA) to 1010 (QD-PVP) μg/g tissue dry weight (DW); statistically equivalent to bulk-CdS treatment (639 μg/g DW). In the roots, Cd from CdCl2, bulk- CdS, QD-MAA and QD-GLY accumulated primarily in the cell wall (~40–55%) followed by organelles (28–40%), suggesting apoplastic pathway; whereas in QD-TOPO, dissolved Cd2+ ions accumulated mainly in the membranes. The exception was QD-PVP, which sequestered Cd mainly in the organelles (49%) in roots, potentially via symplastic pathway and translocated to shoots, resulting in reduced leaf biomass. Results suggested that peroxidases play the predominant role in quenching the oxidative stress caused by CdS-QD exposure. At the highest CdS-QD treatment (200 mg/L), root lignification allowed the plants to restrict Cd accumulation, except in QD-PVP, where lignification was reduced by 21% leading to higher Cd content in shoots. Increased amino acid content in the leaves was noted as a stress tolerance mechanism by the plants exposed to 200 mg/L QD treatments. This study highlights the significant influence that surface coating exerts on QDs fate and effects in a planted system.

Evaluation of the novel nanoparticle material – CdSe quantum dots on Chlorella pyrenoidosa and Scenedesmus obliquus: Concentration-time-dependent responses

Quantum dots (QDs), as a kind of novel nanomaterial, have the extensive applications in various fields, inevitably leading to increasing risks for the ecological environment. The mobilization of cadmium including metal smelting and subsequent machining for multifarious applications has caused the release of cadmium element into the environment. In this study, we evaluated the potential toxicity of a novel nanoparticle material CdSe QDs, using two green algae Chlorella pyrenoidosa and Scenedesmus obliquus. The impact of CdSe QDs and cadmium ions on algae and the sensitivity of the two algae on target compounds were also considered and compared. Our results showed the algal growth rates and chlorophyll content decreased with increasing exposure concentrations and durations. Moreover, the glutathione levels were decreased while the activities of superoxide dismutase increased, exhibiting their pivotal functions in defeating toxic stress. The increment of malondialdehyde levels revealed that the stresses of CdSe QDs and cadmium ions were contributed to the occurrence of oxidative damage. Our study also indicated that the impact of CdSe QDs was stronger than that of cadmium nitrate and the algal response was also species-specific. In addition, the TEM photographs of the algal ultrastructure showed the presence of surface attachment and uptake of QDs.

The Colloidal Quantum Dots Suitability for Long Term Cell Imaging

Fluorescent semiconductor nanoparticles in tree-dimensional quantum confinement, quantum dots (QDs), synthesized in aqueous medium, and functionalized with polyethylene glycol, were used as nonspecific nanosized probes for the long-term imaging of glial cells. In vitro living healthy as well as cancer glial cells were labelled by direct insertion of a small volume of QDs contained in aqueous suspension into the culture wells. A long-term monitoring (over 7 days) of the cells was performed and no evidence of cell fixation and/or damage was observed. Two control groups, healthy and non-healthy glial cells, were used to compare cell viability. During the observation period, labelled cells kept the same behavior compared to non-labelled control samples. To our knowledge, this is the first report of the viability of quantum dots for long-term imaging of living cells. This opens a large range of possibilities related to a better understand of cellular mechanisms, which till now was not achieved by any other fluorescent probe. The study also permitted the observation of two distinct interaction kinetics between cells and QDs. Healthy glial cells were mainly labelled at their surface, while non-healthy glial cells have shown a high rate in the uptake of QDs.

Graphene quantum dots in alveolar macrophage: uptake-exocytosis, accumulation in nuclei, nuclear responses and DNA cleavage

BackgroundGiven the tremendous potential for graphene quantum dots (QDs) in biomedical applications, a thorough understanding of the interaction of these materials with macrophages is essential because macrophages are one of the most important barriers against exogenous particles. Although the cytotoxicity and cellular uptake of graphene QDs were reported in previous studies, the interaction between nuclei and the internalized graphene QDs is not well understood. We thus systematically studied the nuclear uptake and related nuclear response associated with aminated graphene QDs (AG-QDs) exposure.ResultsAG-QDs showed modest 24-h inhibition to rat alveolar macrophages (NR8383), with a minimum inhibitory concentration (MIC) of 200 μg/mL. Early apoptosis was significantly increased by AG-QDs (100 and 200 μg/mL) exposure and played a major role in cell death. The internalization of AG-QDs was mainly via energy-dependent endocytosis, phagocytosis and caveolae-mediated endocytosis. After a 48-h clearance period, more than half of the internalized AG-QDs remained in the cellular cytoplasm and nucleus. Moreover, AG-QDs were effectively accumulated in nucleus and were likely regulated by two nuclear pore complexes genes (Kapβ2 and Nup98). AG-QDs were shown to alter the morphology, area, viability and nuclear components of exposed cells. Significant cleavage and cross-linking of DNA chains after AG-QDs exposure were confirmed by atomic force microscopy investigation. Molecular docking simulations showed that H-bonding and π-π stacking were the dominant forces mediating the interactions between AG-QDs and DNA, and were the important mechanisms resulting in DNA chain cleavage. In addition, the generation of reactive oxygen species (ROS) (e.g., •OH), and the up-regulation of caspase genes also contributed to DNA cleavage.ConclusionsAG-QDs were internalized by macrophages and accumulated in nuclei, which further resulted in nuclear damage and DNA cleavage. It is demonstrated that oxidative damage, direct contact via H-bonding and π-π stacking, and the up-regulation of caspase genes are the primary mechanisms for the observed DNA cleavage by AG-QDs.