Necrotic cell death induced by the protein-mediated intercellular uptake of CdTe quantum dots

The impact of Zn doping on CdTe quantum dots-protein corona formation and the subsequent toxicity at the molecular and cellular level

Understanding the formation of protein corona (PC) is of vital importance for exploring the toxicity of nanoparticles and promoting their safe applications. In this study, CdTe QDs doping with 0, 1%, 5% and 10% Zn were synthesized using one-pot hydrothermal methods. Afterwards, this study explored and compared the formation of pure and Zn doped-QDs PC as well as the subsequent molecular and cellular toxicity. Result found that Zn doping regulated the toxicity of Cd-QDs by controlling their ability to adsorb serum proteins. The adsorption to Cd-QDs induced the dispersion, unfolding, secondary structural changes and the activity loss of bovine serum albumin (BSA). Among the synthesized Cd-QDs, 10%Zn-QDs exhibited the highest fluorescence quantum yield and lowest molecular toxicity. The formations of pure QDs and 10%Zn-QDs with BSA corona are majorly driven by different forces with different patterns. The regulation of BSA on the cytotoxicity differences of pure QDs and 10%Zn-QDs was similar with fetal bovine serum, proving the significant contribution of BSA to the cytotoxicity of Cd-QDs PC. Compared with pure QDs PC, the higher cytotoxicity and oxidative stress level of 10%Zn-QDs PC were correlated with higher intracellular [Cd²⁺]. Both larger amount of BSA adsorption and higher level of intracellular reactive oxygen species could accelerate the dissolution rates of 10%Zn-QDs and thus result in higher intracellular [Cd²⁺].

Recent Trends and Developments in Multifunctional Nanoparticles for Cancer Theranostics

Conventional anticancer treatments, such as radiotherapy and chemotherapy, have significantly improved cancer therapy. Nevertheless, the existing traditional anticancer treatments have been reported to cause serious side effects and resistance to cancer and even to severely affect the quality of life of cancer survivors, which indicates the utmost urgency to develop effective and safe anticancer treatments. As the primary focus of cancer nanotheranostics, nanomaterials with unique surface chemistry and shape have been investigated for integrating cancer diagnostics with treatment techniques, including guiding a prompt diagnosis, precise imaging, treatment with an effective dose, and real-time supervision of therapeutic efficacy. Several theranostic nanosystems have been explored for cancer diagnosis and treatment in the past decade. However, metal-based nanotheranostics continue to be the most common types of nonentities. Consequently, the present review covers the physical characteristics of effective metallic, functionalized, and hybrid nanotheranostic systems. The scope of coverage also includes the clinical advantages and limitations of cancer nanotheranostics. In light of these viewpoints, future research directions exploring the robustness and clinical viability of cancer nanotheranostics through various strategies to enhance the biocompatibility of theranostic nanoparticles are summarised.

CdTe quantum dots trigger oxidative stress and endoplasmic reticulum stress-induced apoptosis and autophagy in rat Schwann cell line RSC96

In the current study, the cytotoxicity and mechanisms of cadmium telluride quantum dots (CdTe QDs) on RSC96 cells were evaluated by exposing different doses of CdTe QDs for 24 h. Two types of cell death, including apoptosis and autophagy, as well as two important organelles, mitochondria and endoplasmic reticulum, were focused after CdTe QDs exposure. The results showed that CdTe QDs induced apoptosis in RSC96 cells in a concentration-dependent manner; promoted the accumulation of intracellular reactive oxygen species; decreased the mitochondrial membrane potential; caused the release of cytochrome c; and also increased the expression of Bcl-2 associated X protein, caspase-3, and cytochrome c proteins and decreased the expression of Bcl-2 protein. Further results also confirmed that CdTe QDs could be internalized by RSC96 cells, and the exposure and internalization of CdTe QDs could induce excessive endoplasmic reticulum stress in the cells, and the expression levels of binding immunoglobulin protein, C/EBP homologous protein, and caspase12 proteins were increased in a concentration-dependent manner. Moreover, autophagy-related proteins LC3II, Beclin1, and P62 all increased after CdTe QDs exposure, suggesting that CdTe QDs exposure both promoted autophagosome formation and inhibited autophagosome degradation, and that CdTe QDs affected the autophagic flow in RSC96 cells. In conclusion, CdTe QDs are able to cause apoptosis and autophagy in RSC96 cells through mitochondrial and endoplasmic reticulum stress pathways, and the possible neurotoxicity of CdTe QDs should be further investigated.

Quantum-Dot-Based Iron Oxide Nanoparticles Activate the NLRP3 Inflammasome in Murine Bone Marrow-Derived Dendritic Cells

Inflammasomes are cytosolic complexes composed of a Nod-like receptor, NLR, the adaptor protein, ASC, and a proteolytic enzyme, caspase-1. Inflammasome activation leads to caspase-1 activation and promotes functional maturation of IL-1β and IL-18, two prototypical inflammatory cytokines. Besides, inflammasome activation leads to pyroptosis, an inflammatory type of cell death. Inflammasomes are vital for the host to cope with foreign pathogens or tissue damage. Herein, we show that quantum-dot-based iron oxide nanoparticles, MNP@QD, trigger NLRP3 inflammasome activation and subsequent release of proinflammatory interleukin IL-1β by murine bone marrow-derived dendritic cells (BMDCs). This activation is more pronounced if these cells endocytose the nanoparticles before receiving inflammatory stimulation. MNP@QD was characterized by using imaging techniques like transmission electron microscopy, fluorescence microscopy, and atomic force microscopy, as well as physical and spectroscopical techniques such as fluorescence spectroscopy and powder diffraction. These findings may open the possibility of using the composite MNP@QD as both an imaging and a therapeutic tool.

Emerging Roles of Green-Synthesized Chalcogen and Chalcogenide Nanoparticles in Cancer Theranostics

The last few decades have seen an overwhelming increase in the amount of research carried out on the use of inorganic nanoparticles. More fascinating is the tremendous progress made in the use of chalcogen and chalcogenide nanoparticles in cancer theranostics. These nanomaterials, which were initially synthesized through chemical methods, have now been efficiently produced using different plant materials. The paradigm shift towards the biogenic route of nanoparticle synthesis stems from its superior advantages of biosafety, eco-friendliness, and simplicity, among others. Despite a large number of reviews available on inorganic nanoparticle synthesis through green chemistry, there is currently a dearth of information on the green synthesis of chalcogens and chalcogenides for cancer research. Nanoformulations involving chalcogens such as sulfur, selenium, and tellurium and their respective chalcogenides have recently emerged as promising tools in cancer therapeutics and diagnosis. Similar to other inorganic nanoparticles, chalcogens and chalcogenides have been synthesized using plant extracts and their purified biomolecules. In this review, we provide an up-to-date discussion of the recent progress that has been made in the plant-mediated synthesis of chalcogens and chalcogenides with a special focus on their application in cancer theranostics.

Protein corona mitigated the cytotoxicity of CdTe QDs to macrophages by targeting mitochondria

Despite the potential of cadmium telluride quantum dots (CdTe QDs) in bioimaging and drug delivery, their toxic effects have been documented. It is known that the immunotoxicity of CdTe QDs targeting macrophages is one of their adverse effects, and the protein corona (PC) will affect the biological effects of QDs. In order to prove whether the PC-CdTe QDs complexes could alleviate the toxicity of CdTe QDs without weakening their luminescence, we investigated the impact of protein corona formed in fetal bovine serum (FBS) on the cytotoxicity of CdTe QDs to mitochondria. RAW264.7 cells were used as the model to compare the effects of CdTe QDs and PC-CdTe QDs complexes on the structure, function, quantity, morphology, and mitochondrial quality control of mitochondria. As result, the protein corona form in FBS alleviated the inhibition of CdTe QDs on mitochondrial activity, the damage to mitochondrial membrane, the increase of ROS, and the reduction of ATP content. Also, CdTe QDs increased the number of mitochondria in macrophages, while the complexes did not. In line with this, the morphology of mitochondrial network in macrophages which were exposed to CdTe QDs and PC-CdTe QDs complexes was different. CdTe QDs transformed the network into fragments, punctuations, and short rods, while PC-CdTe QDs complexes made the mitochondrial network highly branched, which was related to the imbalance of mitochondrial fission and fusion. Mechanically, CdTe QDs facilitated mitochondrial fission and inhibited mitochondrial fusion, while protein corona reversed the phenomenon caused by QDs. Besides mitochondrial dynamics, mitochondrial biogenesis and mitophagy were also affected. CdTe QDs increased the expression of mitochondrial biogenesis signaling molecules including PGC-1α, NRF-1 and TFAM, while PC-CdTe QDs complexes played the opposite role. With regard to mitophagy, they both showed promoting effect. In conclusion, the formation of protein corona alleviated the toxic effects of CdTe QDs on the mitochondria in macrophages and affected mitochondrial quality control. Under the premise of ensuring the fluorescence properties of CdTe QDs, these findings provided useful insight into reducing the toxicity of CdTe QDs from two perspectives: protein corona and mitochondria, and shared valuable information for the safe use of QDs.

Intracellular reactive oxygen species trigger mitochondrial dysfunction and apoptosis in cadmium telluride quantum dots-induced liver damage

Quantum dots (QDs), also known as semiconductor QDs, have specific photoelectricproperties which find application in bioimaging, solar cells, and light-emitting diodes (LEDs). However, the application of QDs is often limited by issues related to health risks and potential toxicity. The purpose of this study was to provide evidence regarding the safety of cadmium telluride (CdTe) QDs by exploring the detailed mechanisms involved in its hepatotoxicity. This study showed that CdTe QDs can increase reactive oxygen species (ROS) in hepatocytes after being taken up by hepatocytes, which triggers a significant mitochondrial-dependent apoptotic pathway, leading to hepatocyte apoptosis. CdTe QDs-induce mitochondrial cristae abnormality, adenosine triphosphate (ATP) depletion, and mitochondrial membrane potential (MMP) depolarization. Meanwhile, CdTe QDs can change the morphology, function, and quantity of mitochondria by reducing fission and intimal fusion. Importantly, inhibition of ROS not only protects hepatocyte viability but can also interfere with apoptosis and activation of mitochondrial dysfunction. Similarly, the exposure of CdTe QDs in Institute of Cancer Research (ICR) mice showed that CdTe QDs caused oxidative damage and apoptosis in liver tissue. NAC could effectively remove excess ROS could reduce the level of oxidative stress and significantly alleviate CdTe QDs-induced hepatotoxicity in vivo. CdTe QDs-induced hepatotoxicity may originate from the generation of intracellular ROS, leading to mitochondrial dysfunction and apoptosis, which was potentially regulated by mitochondrial dynamics. This study revealed the nanobiological effects of CdTe QDs and the intricate mechanisms involved in its toxicity at the tissue, cell, and subcellular levels and provides information for narrowing the gap between in vitro and in vivo animal studies and a safety assessment of QDs.

Antiproliferative and Genotoxic Action of an Underexploited Organoteluran Derivative on Sarcoma 180 Cells

BACKGROUND

The search for novel metallic chemical compounds with toxicogenic effects has been of great importance for more efficient cancer treatment.

OBJECTIVE

The study evaluated the cytotoxic, genotoxic and mutagenic activity of organoteluran RF07 in the S-180 cell line.

METHODS

The bioassays used were cell viability with 3-(4,5-dimethyl-2-thiazole)-2,5-diphenyl-2-H-tetrazolium bromide (MTT) test, evaluation of apoptosis and necrosis using fluorescence and flow cytometry, cytokinesisblock micronucleus test and comet assay. The compound was tested at 1; 2.5 and 5μM.

RESULTS

The results showed the cytotoxicity of RF07 at concentrations of 2.5, 5, 10 and 20μM when compared to the negative control. For genotoxicity tests, RF07 showed effects in all concentrations assessed by increased index and frequencies of damage and mutagenic alterations. The compound was also cytotoxic due to the significant decrease in the nuclear division index, with significant values of apoptosis and necrosis. The results of fluorescence and flow cytometry showed apoptosis as the main type of cell death caused by RF07 at 5μM, which is thought to avoid an aggressive immune response of the organism.

CONCLUSION

In addition to cytotoxic and genotoxic effects, RF07 creates good perspectives for future antitumor formulations.

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.

Toxicity of different types of quantum dots to mammalian cells in vitro: An update review

Currently, there are a great quantity type of quantum dots (QDs) that has been developed by researchers. Depending on the core material, they can be roughly divided into cadmium, silver, indium, carbon and silicon QDs. And studies on the toxicity of QDs are also increasing rapidly, but in vivo tests in model animals fail to reach a consistent conclusion. Therefore, we review the literatures dealing with the cytotoxicity of QDs in mammalian cells in vitro. After a short summary of the application characteristics of five types of QDs, the fate of QDs in cells will be discussed, ranging from the uptake, transportation, sublocation and excretion. A substantial part of the review will be focused on in vitro toxicity, in which the type of QDs is combined with their adverse effect and toxic mechanism. Because of their different luminescent properties, different subcellular fate, and different degree of cytotoxicity, we provide an overview on the balance of optical stability and biocompatibility of QDs and give a short outlook on future direction of cytotoxicology of QDs.

Titanium Dioxide Nanoparticles Induced HeLa Cell Necrosis under UVA Radiation through the ROS-mPTP Pathway

Titanium dioxide nanoparticles (nano-TiO₂), as a common nanomaterial, are widely used in water purification, paint, skincare and sunscreens. Its safety has always been a concern. Prior studies have shown that ultraviolet A (UVA) can exacerbate the toxicity of nano-TiO₂, including inducing cell apoptosis, changing glycosylation levels, arresting cell cycle, inhibiting tumor cell and bacterial growth. However, whether the combination of UVA and nano-TiO₂ cause cell necrosis and its mechanism are still rarely reported. In this study, we investigated the cytotoxicity and phototoxicity of mixture crystalline nano-TiO₂ (25% rutile and 75% anatase, 21 nm) under UVA irradiation in HeLa cells. Our results showed that the abnormal membrane integrity and the ultrastructure of HeLa cells, together with the decreased viability induced by nano-TiO₂ under UVA irradiation, were due to cell necrosis rather than caspase-dependent apoptosis. Furthermore, nano-TiO₂ and UVA generated the reactive oxygen species (ROS) and caused the mitochondrial permeability transition pore (mPTP) of HeLa cells to abnormally open. Cell viability was significantly increased after adding vitamin C (VC) or cyclosporin A (CsA) individually to inhibit ROS and mPTP. Clearance of ROS could not only impede the opening of mPTP but also reduce the rate of cell necrosis. The results suggest the possible mechanism of HeLa cell necrosis caused by nano-TiO₂ under UVA irradiation through the ROS-mPTP pathway.

Mechanisms and pathogenesis underlying environmental chemical-induced necroptosis

Necroptosis is a regulated cell death that is governed by mixed lineage kinase domain-like, receptor-interacting serine-threonine kinase 3 and commonly displays with necrosis morphological characteristics. This study examined the molecular mechanisms involved in the chemical-induced necroptosis where a systematic evaluation of experimental studies addressing this issue is missing. We strictly reviewed all scientific reports related to our search terms including "necroptosis" or "programmed necrosis", "environmental chemicals" or "air pollutants" or "pesticides" or "nanoparticles" and "Medicines" from 2009 to 2019. Manuscripts that met the objective of this study were included for further evaluations. Studies showed that several pathological contexts like cancer, neurodegenerative disorders, and inflammatory diseases were related to necroptosis. Furthermore, multiple chemical-induced cytotoxic effects, such as DNA damage, mitochondrial dysregulation, oxidative damage, lipid peroxidation, endoplasmic reticulum disruption, and inflammation are also associated with necroptosis. The main environmental exposures that are related to necroptosis are air pollutants (airborne particulate matter, cadmium, and hydrogen sulfide), nanoparticles (gold, silver, and silica), pesticides (endosulfan, cypermethrin, chlorpyrifos, and paraquat), and tobacco smoke. To sum up, air pollutants, pesticides, and nanoparticles could potentially affect human health via disruption of cell growth and induction of necroptosis. Understanding the exact molecular pathogenesis of these environmental chemicals needs further comprehensive research to provide innovative concepts for the prevention approaches and introduce novel targets for the amelioration of a range of human health problems.

Differences in toxicity, mitochondrial function and miRNome in human cells exposed in vitro to Cd as CdS quantum dots or ionic Cd

Cadmium is toxic to humans, although Cd-based quantum dots exerts less toxicity. Human hepatocellular carcinoma cells (HepG2) and macrophages (THP-1) were exposed to ionic Cd, Cd(II), and cadmium sulfide quantum dots (CdS QDs), and cell viability, cell integrity, Cd accumulation, mitochondrial function and miRNome profile were evaluated. Cell-type and Cd form-specific responses were found: CdS QDs affected cell viability more in HepG2 than in THP-1; respective IC₂₀ values were ∼3 and ∼50 μg ml^-1. In both cell types, Cd(II) exerted greater effects on viability. Mitochondrial membrane function in HepG2 cells was reduced 70 % with 40 μg ml^-1 CdS QDs but was totally inhibited by Cd(II) at corresponding amounts. In THP-1 cells, CdS QDs has less effect on mitochondrial function; 50 μg ml^-1 CdS QDs or equivalent Cd(II) caused 30 % reduction or total inhibition, respectively. The different in vitro effects of CdS QDs were unrelated to Cd uptake, which was greater in THP-1 cells. For both cell types, changes in the expression of miRNAs (miR-222, miR-181a, miR-142-3p, miR-15) were found with CdS QDs, which may be used as biomarkers of hazard nanomaterial exposure. The cell-specific miRNome profiles were indicative of a more conservative autophagic response in THP-1 and as apoptosis as in HepG2.

Targeting non-apoptotic cell death in cancer treatment by nanomaterials: Recent advances and future outlook

Many tumors develop resistance to most of the apoptosis-based cancer therapies. In this sense targeting non-apoptotic forms of cell death including necroptosis, autophagy and ferroptosis may have therapeutic benefits in apoptosis-defective cancer cells. Nanomaterials have shown great advantages in cancer treatment owing to their unique characteristics. Besides, the capability of nanomaterials to induce different forms of cell death has gained widespread attention in cancer treatment. Reports in this field reflect the therapeutic potential of necroptotic cell death induced by nanomaterials in cancer. Also, autophagic cell death induced by nanomaterials alone and as a part of chemo-, radio- and photothermal therapy holds great promise as anticancer therapeutic option. Besides, ferroptosis induction by iron-based nanomaterials in drug delivery, immunotherapy, hyperthermia and imaging systems shows promising results in malignancies. Hence, this review is devoted to the latest efforts and the challenges in this field of research and its clinical merits.

A metabolomics study: CdTe/ZnS quantum dots induce polarization in mice microglia

In this study, a metabolomic analysis was used to reveal the neurotoxicity of the CdTe/ZnS QDs via microglia polarization. A gas chromatography-mass spectrometer (GC-MS) was applied to uncover the metabonomic changes in microglia (BV-2 cell line) after exposure to 1.25 μM CdTe/ZnS QDs. 11 annotated metabolic pathways (KEGG database) were significantly changed in all exposed groups (3 h, 6 h, 12 h), 3 of them were related to glucose metabolism. The results of the Seahorse XFe96 Analyzer indicated that the CdTe/ZnS QDs increased the glycolysis level of microglia by 86% and inhibited the aerobic respiration level by 54% in a non-hypoxic environment. In vivo study, 3 h after the injection of CdTe/ZnS QDs (2.5 mM) through the tail vein in mice, the concentration of the CdTe/ZnS QDs in hippocampus reached the peak (1.25 μM). The polarization level of microglia (Iba-1 immunofluorescence) increased 2.7 times. In vitro study, the levels of the extracellular TNF-α, IL-1β and NO of BV-2 cells were all increased significantly after a 6 h or 12 h exposure. According to the results of the Cell Counting Kit-8, after a 6 h or 12 h exposure to the CdTe/ZnS QDs, the exposed microglia could significantly decrease the number of neurons (HT-22 cell line). This study proved that CdTe/ZnS QDs could polarize microglia in the brain and cause secondary inflammatory damage to neurons. There are potential risks in the application of the CdTe/ZnS QDs in brain tissue imaging.

The interaction between nanoparticles-protein corona complex and cells and its toxic effect on cells

Once nanoparticles (NPs) contact with the biological fluids, the proteins immediately adsorb onto their surface, forming a layer called protein corona (PC), which bestows the biological identity on NPs. Importantly, the NPs-PC complex is the true identity of NPs in physiological environment. Based on the affinity and the binding and dissociation rate, PC is classified into soft protein corona, hard protein corona, and interfacial protein corona. Especially, the hard PC, a protein layer relatively stable and closer to their surface, plays particularly important role in the biological effects of the complex. However, the abundant corona proteins rarely correspond to the most abundant proteins found in biological fluids. The composition profile, formation and conformational change of PC can be affected by many factors. Here, the influence factors, not only the nature of NPs, but also surface chemistry and biological medium, are discussed. Likewise, the formed PC influences the interaction between NPs and cells, and the associated subsequent cellular uptake and cytotoxicity. The uncontrolled PC formation may induce undesirable and sometimes opposite results: increasing or inhibiting cellular uptake, hindering active targeting or contributing to passive targeting, mitigating or aggravating cytotoxicity, and stimulating or mitigating the immune response. In the present review, we discuss these aspects and hope to provide a valuable reference for controlling protein adsorption, predicting their behavior in vivo experiments and designing lower toxicity and enhanced targeting nanomedical materials for nanomedicine.

Mitochondrial toxicity of nanomaterials

In recent years, nanomaterials have been widely applied in electronics, food, biomedicine and other fields, resulting in increased human exposure and consequent research focus on their biological and toxic effects. Mitochondria, the main target organelle for nanomaterials (NM), play a critical role in their toxic activities. Several studies to date have shown that nanomaterials cause alterations in mitochondrial morphology, mitochondrial membrane potential, opening of the mitochondrial permeability transition pore (MPTP) and mitochondrial respiratory function, and promote cytochrome C release. An earlier mitochondrial toxicity study of NMs additionally reported induction of mitochondrial dynamic changes. Here, we have reviewed the mitochondrial toxicity of NMs and provided a scientific basis for the contribution of mitochondria to the toxicological effects of different NMs along with approaches to reduce mitochondrial and, consequently, overall toxicity of NMs.

Cytotoxicity investigations of biogenic tellurium nanorods towards PC12 cell line

The authors evaluated the cytotoxicity underlying mechanisms of biogenic tellurium (Te) nanorods (NRs) produced by the Pseudomonas pseudoalcaligenes strain Te on the PC12 cell line. The half-maximal inhibitory concentration (IC₅₀) value was estimated at 5.05 ± 0.07 ng/ml for biogenic Te NRs and 2.44 ± 0.38 ng/ml for K₂TeO₃, respectively. The viability of PC12 was inhibited concentration dependent at doses of 1, 2.5, 5, 10, and 20 ng/ml. Te NRs principally induced late apoptosis or necrosis at IC₅₀ concentration, without effect on caspase-3 activities. Furthermore, Te NRs reduced glutathione and enhanced malondialdehyde levels, and also reduced superoxide dismutase and catalase activities. These findings revealed that biogenic Te NRs were less toxic than K₂TeO₃. Additionally, they induced cytotoxity towards the PC12 cell line through the activation of late apoptosis independent of the caspase pathway, and may also enhance oxidative stress in the nervous system.

Toxic effects and involved molecular pathways of nanoparticles on cells and subcellular organelles

Owing to the increasing application of engineered nanoparticles (NPs), besides the workplace, human beings are also exposed to NPs from nanoproducts through the skin, respiratory tract, digestive tract and vein injection. This review states pathways of cellular uptake, subcellular distribution and excretion of NPs. The uptake pathways commonly include phagocytosis, micropinocytosis, clathrin- and caveolae-mediated endocytosis, scavenger receptor-related pathway, clathrin- or caveolae-independent pathway, and direct penetration or insertion. Then the ability of NPs to decrease cell viability and metabolic activity, change cell morphology, and destroy cell membrane, cytoskeleton and cell function was presented. In addition, the lowest dose decreasing cell metabolic viability compared with the control or IC₅₀ of silver, titanium dioxide, zinc oxide, carbon black, carbon nanotubes, silica, silicon NPs and cadmium telluride quantum dots to some cell lines was gathered. Next, this review attempts to increase our understanding of NP-caused adverse effects on organelles, which have implications in mitochondrial dysfunction, endoplasmic reticulum stress and lysosomal rupture. In particular, the disturbance of mitochondrial biogenesis and mitochondrial dynamic fusion-fission, mitophagy and cytochrome c-dependent apoptosis are involved. In addition, prolonged endoplasmic reticulum stress will result in apoptosis. Rupture of the lysosomal membrane was associated with inflammation, and both induction of autophagy and blockade of autophagic flow can result in cytotoxicity. Finally, the network mechanism of the combined action of multiple organelle dysfunction, apoptosis, autophagy and oxidative stress was discussed.

Shape-dependent adhesion and endocytosis of hydroxyapatite nanoparticles on A7R5 aortic smooth muscle cells

The interaction between nanohydroxyapatite (HAP) and smooth muscle cells is an important step in vascular calcification. However, the effect of the shape of HAP on adhesion and endocytosis to aortic smooth muscle cells has been rarely reported. Four different morphological HAP crystals (H-Rod, H-Needle, H-Sphere, and H-Plate) were selected to interact with rat aortic smooth muscle cells (A7R5). Fluorescence-labeled HAP was used to detect crystal adhesion and endocytosis and then pretreated with different endocytic inhibitors to explore the pathway of endocytotic crystals. The distribution of crystals inside and outside the cells and the crystal localization in lysosomes was observed through laser confocal microscopy. The effect of crystal on the cell cycle and the changes in the expression of phosphatidylserine, osteopontin, α-actin, core binding factor alpha 1, and osterix on the surface of A7R5 cells were detected. The adhesion and endocytosis of HAP on A7R5 cells were closely related to crystal shapes and ranked as follows: H-Plate > H-Sphere > H-Needle > H-Rod. H-Sphere and H-Needle were internalized into the cells mainly via the clathrin-mediated pathway, whereas H-Plate and H-Rod were internalized into the cells mainly via macropinocytosis. The endocytosed nano-HAP was mainly distributed in the cell lysosome. The adhesion and endocytosis of HAP to A7R5 cells were positively correlated with the specific surface area, and contact area of HAP and negatively correlated with the absolute value of Zeta and contact angle of HAP. This study provided insights into the effect of crystal morphology on vascular calcification and its mechanism.

Dose- and duration-dependent cytotoxicity and genotoxicity in human hepato carcinoma cells due to CdTe QDs exposure

Nanotechnology has achieved more commercial attention over recent years, and its application has increased concerns about its discharge in the environment. In this study, we have chosen human hepatic carcinoma (HuH-7) cells because liver tissue has played an important role in human metabolism. Therefore, the objective of this study was to determine DNA damaging and apoptotic potential of cadmium telluride quantum dots (CdTe QDs; average particle size (APS) 10 nm, 1-25 µg/ml) on HuH-7 cells and the basic molecular mechanism of its cellular toxicity. Cytotoxicity of different concentrations of CdTe QDs on HuH-7 cells was determined by 3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium (MTS) and lactate dehydrogenase (LDH) tests. Moreover, reactive oxygen species (ROS) generation, mitochondrial membrane potential, DNA damage, and Hoechst 33342 fluorescent staining morphological analysis of necrotic/apoptotic cells were detected; cellular impairment in mitochondria and DNA was confirmed by JC-1 and comet assay, respectively. A dose- and time-dependent cytotoxicity effect of CdTe QDs exposure was observed HuH-7 cells; the significant (p < 0.05) cytotoxicity was found at 25 μg/ml of CdTe QDs exposure. The percentage of cytotoxicity of CdTe QDs (25 μg/ml) in HuH-7 cells reached 62% in 48 h. CdTe QDs elicited intracellular ROS generation and mitochondrial depolarization, and DNA integrity cells collectively advocated the apoptotic cell death at higher concentration. DNA damage was observed in cells due to CdTe QDs exposure, which was mediated by oxidative stress. This study exploring the effects of CdTe QDs in HuH-7 cells has provided valuable insights into the mechanism of toxicity induced by CdTe QDs.

Nanoparticles for Bioapplications: Study of the Cytotoxicity of Water Dispersible CdSe(S) and CdSe(S)/ZnO Quantum Dots

Semiconductor nanocrystals or quantum dots (QDs) have unique optical and physical properties that make them potential imaging tools in biological and medical applications. However, concerns over the aqueous dispersivity, toxicity to cells, and stability in biological environments may limit the use of QDs in such applications. Here, we report an investigation into the cytotoxicity of aqueously dispersed CdSe(S) and CdSe(S)/ZnO core/shell QDs in the presence of human colorectal carcinoma cells (HCT-116) and a human skin fibroblast cell line (WS1). The cytotoxicity of the precursor solutions used in the synthesis of the CdSe(S) QDs was also determined in the presence of HCT-116 cells. CdSe(S) QDs were found to have a low toxicity at concentrations up to 100 µg/mL, with a decreased cell viability at higher concentrations, indicating a highly dose-dependent response. Meanwhile, CdSe(S)/ZnO core/shell QDs exhibited lower toxicity than uncoated QDs at higher concentrations. Confocal microscopy images of HCT-116 cells after incubation with CdSe(S) and CdSe(S)/ZnO QDs showed that the cells were stable in aqueous concentrations of 100 µg of QDs per mL, with no sign of cell necrosis, confirming the cytotoxicity data.

Necrotic, apoptotic and autophagic cell fates triggered by nanoparticles

Nanomaterials have gained a rapid increase in use in a variety of applications that pertain to many aspects of human life. The majority of these innovations are centered on medical applications and a range of industrial and environmental uses ranging from electronics to environmental remediation. Despite the advantages of NPs, the knowledge of their toxicological behavior and their interactions with the cellular machinery that determines cell fate is extremely limited. This review is an attempt to summarize and increase our understanding of the mechanistic basis of nanomaterial interactions with the cellular machinery that governs cell fate and activity. We review the mechanisms of NP-induced necrosis, apoptosis and autophagy and potential implications of these pathways in nanomaterial-induced outcomes. Abbreviations: Ag, silver; CdTe, cadmium telluride; CNTs, carbon nanotubes; EC, endothelial cell; GFP, green fluorescent protein; GO, graphene oxide; GSH, glutathione; HUVECs, human umbilical vein endothelial cells; NP, nanoparticle; PEI, polyethylenimine; PVP, polyvinylpyrrolidone; QD, quantum dot; ROS, reactive oxygen species; SiO2, silicon dioxide; SPIONs, superparamagnetic iron oxide nanoparticles; SWCNT, single-walled carbon nanotubes; TiO2, titanium dioxide; USPION, ultra-small super paramagnetic iron oxide; ZnO, zinc oxide.

Live-stream characterization of cadmium-induced cell death using visible CdTe-QDs

Characterization of cell death currently requires the use of indirect markers, which has largely limited the ability to monitor cell death processes inside the cell. Here, we introduce a new method for the characterization of cell death mechanisms using cadmium telluride quantum dots (CdTe-QDs). Using visible CdTe-QDs with mesenchymal cells (e.g. synoviocytes), live-stream imaging allowed for visualization of cadmium-induced cell death, combining characteristics of apoptosis and autophagy. Initially, similar anti-proliferative effect was observed between 10 µg/ml Cd²⁺ and CdTe-QDs at 24 h (cell index/cell density ratio decreased from 0.6 to −16.6, p < 0.05) using techniques that do not require the capacity of CdTe-QDs. Apoptosis was confirmed by the quantification of morphological parameters (reduced surface area, increased cell thickness) and positive labeling with annexin V. Autophagy was confirmed by monodansylcadaverine staining, identifying similar autophagic vacuoles with both Cd²⁺ and CdTe-QD. However, QD imaging allowed for visualization of cadmium elements inside cell structures and their kinetic changes leading to cell death. Cell death characteristics were similar in inflammatory and non-inflammatory environment but were induced up to 4 h earlier in the former. Therefore, live-stream imaging of a visible cytotoxic agent has useful applications not currently possible with indirect methods, including chronological monitoring of cell death.

A novel strategy to evaluate the degradation of quantum dots: identification and quantification of CdTe quantum dots and corresponding ionic species by CZE-ICP-MS

In view of the significance and urgency of the speciation analysis of quantum dots (QDs) and their degradation products for clarifying their degradation rules and toxicity mechanisms, a method for the identification and quantification of CdTe QDs and corresponding ionic species in complex matrices was developed using capillary zone electrophoresis (CZE) coupled to inductively coupled plasma-mass spectrometry (ICP-MS). The quality assessment of commercial CdTe QDs and serum pharmacokinetics of synthesized CdTe QDs in rats were successfully undertaken using the developed CZE-ICP-MS method.

Dysfunction of various organelles provokes multiple cell death after quantum dot exposure

Quantum dots (QDs) are different from the materials with the micrometer scale. Owing to the superiority in fluorescence and optical stability, QDs act as possible diagnostic and therapeutic tools for application in biomedical field. However, potential threats of QDs to human health hamper their wide utilization in life sciences. It has been reported that oxidative stress and inflammation are involved in toxicity caused by QDs. Recently, accumulating research unveiled that disturbance of subcellular structures plays a magnificent role in cytotoxicity of QDs. Diverse organelles would collapse during QD treatment, including DNA damage, endoplasmic reticulum stress, mitochondrial dysfunction and lysosomal rupture. Different forms of cellular end points on the basis of recent research have been concluded. Apart from apoptosis and autophagy, a new form of cell death termed pyroptosis, which is finely orchestrated by inflammasome complex and gasdermin family with secretion of interleukin-1 beta and interleukin-18, was also summarized. Finally, several potential cellular signaling pathways were also listed. Activation of Toll-like receptor-4/myeloid differentiation primary response 88, nuclear factor kappa-light-chain-enhancer of activated B cells and NACHT, LRR and PYD domains-containing protein 3 inflammasome pathways by QD exposure is associated with regulation of cellular processes. With the development of QDs, toxicity evaluation is far behind its development, where specific mechanisms of toxic effects are not clearly defined. Further studies concerned with this promising area are urgently required.

Cadmium telluride quantum dots induce apoptosis in human breast cancer cell lines

Introduction:

Semiconductor quantum dots (QDs), especially those containing cadmium, have undergone marked improvements and are now widely used nanomaterials in applicable biological fields. However, great concerns exist regarding their toxicity in biomedical applications. Because of the lack of sufficient data regarding the toxicity mechanism of QDs, this study aimed to evaluate the cytotoxicity of three types of QDs: CdTe QDs, high yield CdTe QDs, and CdTe/CdS core/shell QDs on two human breast cancer cell lines MDA-MB468 and MCF-7.

Methods:

The breast cancer cells were treated with different concentrations of QDs, and cell viability was evaluated via MTT assay. Hoechst staining was applied for observation of morphological changes due to apoptosis. Apoptotic DNA fragmentation was visualized by the agarose gel electrophoresis assay. Flow cytometric annexin V/propidium iodide (PI) measurement was used for apoptosis detection.

Results:

A significant decrease in cell viability was observed after QDs treatment ( p < 0.05). Apoptotic bodies and chromatin condensation was observed by Hoechst staining. DNA fragmentation assay demonstrated a DNA ladder profile in the exposed cells and also annexin V/PI flow cytometry confirmed apoptosis in a dose-dependent manner.

Conclusion:

Our results revealed that CdTe, high yield CdTe, and CdTe/CdS core/shell QDs induce apoptosis in breast cancer cell lines in a dose-dependent manner. This study would help realizing the underlying cytotoxicity mechanism, at least partly, of CdTe QDs and may provide information for the development of nanotoxicology and safe use of biological applications of QDs.

The interactions of CdTe quantum dots with serum albumin and subsequent cytotoxicity: the influence of homologous ligands

With spreading applications of fluorescent quantum dots (QDs) in biomedical fields in recent years, there is increasing concern over their toxicity. Among various factors, surface ligands play critical roles. Previous studies usually employed QDs with different kinds of surface ligands, but general principles were difficult to be obtained since it was hard to compare these surface ligands with varied chemical structures without common features. Herein, the physicochemical properties of two types of CdTe QDs were kept very similar, but different in the surface ligands with mercaptoacetic acid (TGA) and 3-mercaptopropionic acid (MPA), respectively. These two types of homologous ligands only had a difference in one methylene group (-CH2-). The interactions of the two types of CdTe QDs with bovine serum albumin (BSA), which was one of the main components of cell culture, were studied by fluorescence, UV-vis absorption, and circular dichroism spectroscopy. It was found that the fluorescence quenching of BSA by CdTe QDs followed a static quenching mechanism, and there was no obvious difference in the Stern-Volmer quenching constants and binding constants. The thermodynamic parameters of the two types of QDs were similar. BSA underwent conformational changes upon association with these QDs. By comparing the cytotoxicity of these two types of QDs, TGA-capped QDs were found to be less cytotoxic than MPA-capped QDs. Besides, in the presence of serum proteins, the cytotoxicity of the QDs was reduced. QDs in the absence of serum proteins had a higher internalization efficiency, compared with those in the medium with serum. To the best of our knowledge, this is a rare study focusing on surface ligands with such small variations at the biomolecular and cellular levels. These findings can provide new insights for the design and applications of QDs in complex biological media.

Colloidal Gold Nanoparticles Induce Changes in Cellular and Subcellular Morphology

Exposure of cells to colloidal nanoparticles (NPs) can have concentration-dependent harmful effects. Mostly, such effects are monitored with biochemical assays or probes from molecular biology, i.e., viability assays, gene expression profiles, etc., neglecting that the presence of NPs can also drastically affect cellular morphology. In the case of polymer-coated Au NPs, we demonstrate that upon NP internalization, cells undergo lysosomal swelling, alterations in mitochondrial morphology, disturbances in actin and tubulin cytoskeleton and associated signaling, and reduction of focal adhesion contact area and number of filopodia. Appropriate imaging and data treatment techniques allow for quantitative analyses of these concentration-dependent changes. Abnormalities in morphology occur at similar (or even lower) NP concentrations as the onset of reduced cellular viability. Cellular morphology is thus an important quantitative indicator to verify harmful effects of NPs to cells, without requiring biochemical assays, but relying on appropriate staining and imaging techniques.

Effects of Surface Charges on the Bactericide Activity of CdTe/ZnS Quantum Dots: A Cell Membrane Disruption Perspective

The inhibitory effects of CdTe/ZnS quantum dots (QDs) modified with 3-mercaptopropionic acid (negatively charged) or cysteamine (positively charged) on the metabolic activity of Escherichia coli were investigated using biological microcalorimetry. Results show that the inhibitory ratio of positive QDs is higher than that of negative QDs. Transmission electron microscopy images indicate that QDs are prone to be adsorbed on the surface of E. coli. This condition disturbs the membrane structure and function of E. coli. Fluorescence anisotropy results demonstrate that positive QDs show a significant increase in the membrane fluidity of E. coli and dipalmitoylphosphatidylcholine (DPPC) model membrane. Furthermore, fluorescence anisotropy values of DPPC membrane in the gel phase decreased upon the addition of positive QDs. By contrast, anisotropy values in the liquid-crystalline phase are almost constant. The change in membrane fluidity is associated with the increased permeability of the membrane. Finally, the kinetics of dye leakage from liposomes demonstrate that the surface charge of QDs is crucial to the interaction between QDs and membrane.

Different toxicity of cadmium telluride, silicon, and carbon nanomaterials against hemocytes in silkworm, Bombyx mori

Exposure to CdTe QDs, SiNPs, or C–NCDs exerted different toxic effects on silkworm hemocytes via the induction of different PCD processes.

In one harness: the interplay of cellular responses and subsequent cell fate after quantum dot uptake

Rapid growth and expansion of engineered nanomaterials will occur when the technology can be used safely. Quantum dots have excellent prospects in clinical applications, but the issue of toxicity has not yet been resolved. To enable their medical implementation, the effect on, and mechanisms in, live cells should be clearly known and predicted. A massive amount of experimental data dedicated to nanotoxicity has been accumulated to-date, but it lacks a logical structure. The current challenge is to organize existing knowledge into lucid biological and mathematical models. In our review we aim to describe the interplay of various cell death mechanisms triggered by quantum dots as a consequence of particle parameters and experimental conditions.

Size Effects on the Interaction of QDs with the Mitochondrial Membrane In Vitro

The mitochondrial toxicity induced by GSH-CdTe Quantum dots (QDs) of different sizes was investigated. The decreases in absorbance and transmission electron microscopy images show that QDs induce the swelling of mitochondria. Results of flow cytometry indicate that QDs cause a reduction of mitochondrial membrane potential (MMP). A remarkable increase in fluidity of protein regions of mitochondrial membrane is observed, whereas the lipid regions are not obviously affected. Cyclosporin A (CsA) effectively prevents the QD-induced mitochondrial swelling. On the basis of these results, it is proposed that QDs induce mitochondrial permeability transition (MPT). Moreover, with increasing QDs size, a pronounced MPT is observed. The difference between the membrane fluidity induced by QDs and Cadmium ion and the ineffective protective effects of EDTA suggests that the mitochondrial toxicity of QDs cannot be only attributed to the release of metal ion. The protective effects of HSA indicate that the interaction of QDs with pore-forming protein gives rise to the increase in membrane fluidity. This hypothesis is demonstrated by the interaction of QDs with model membranes and proteins using differential scanning calorimetry and isothermal titration microcalorimetry. In conclusion, as the size of QDs increases, the binding affinity of QDs with membrane protein increases, and therefore causes a pronounced mitochondrial damage.

Probing the interactions of CdTe quantum dots with pseudorabies virus

Quantum dots (QDs) have become one of the most promising luminescent materials for tracking viral infection in living cells. However, several issues regarding how QDs interact with the virus remain unresolved. Herein, the effects of Glutathione (GSH) capped CdTe QDs on virus were investigated by using pseudorabies virus (PRV) as a model. One-step growth curve and fluorescence colocalization analyses indicate that CdTe QDs inhibit PRV multiplication in the early stage of virus replication cycle by suppressing the invasion, but have no significant effect on the PRV penetration. Fluorescence spectrum analysis indicates that the size of QDs is reduced gradually after the addition of PRV within 30 min. Release of Cd²⁺ was detected during the interaction of QDs and PRV, resulting in a decreased number of viruses which can infect cells. Further Raman spectra and Circular Dichroism (CD) spectroscopy analyses reveal that the structure of viral surface proteins is altered by CdTe QDs adsorbed on the virus surface, leading to the inhibition of virus replication. This study facilitates an in-depth understanding of the pathogenic mechanism of viruses and provides a basis for QDs-labeled virus research.