Fate of CdSe/ZnS quantum dots in cells: Endocytosis, translocation and exocytosis

Current Advances in Nanomaterials Affecting Functions and Morphology of Platelets

Nanomaterials have been extensively used in the biomedical field due to their unique physical and chemical properties. They promise wide applications in the diagnosis, prevention, and treatment of diseases. Nanodrugs are generally transported to target tissues or organs by coupling targeting molecules or enhanced permeability and retention effect (EPR) passively. As intravenous injection is the most common means of administration of nanomedicine, the transport process inevitably involves the interactions between nanoparticles (NPs) and blood cells. Platelets are known to not only play a critical role in normal coagulation by performing adhesion, aggregation, release, and contraction functions, but also be associated with pathological thrombosis, tumor metastasis, inflammation, and immune reactions, making it necessary to investigate the effects of NPs on platelet function during transport, particularly the way in which their physical and chemical properties determine their interaction with platelets and the underlying mechanisms by which they activate and induce platelet aggregation. However, such data are lacking. This review is intended to summarize the effects of NPs on platelet activation, aggregation, release, and apoptosis, as well as their effects on membrane proteins and morphology in order to shed light on such key issues as how to reduce their adverse reactions in the blood system, which should be taken into consideration in NP engineering.

Nanoparticles Internalization through HIP-55-Dependent Clathrin Endocytosis Pathway

Nanoparticles are promising tools for biomedicine. Many nanoparticles are internalized to function. Clathrin-mediated endocytosis is one of the most important mechanisms for nanoparticle internalization. However, the regulatory mechanism of clathrin-mediated nanoparticle endocytosis is still unclear. Here, we report that the adapter protein HIP-55 regulates clathrin-mediated nanoparticle endocytosis. CdSe/ZnS quantum dots (QDs), a typical nanoparticle, enter cells through the HIP-55-dependent clathrin endocytosis pathway. Both pharmacological inhibitor and genetic intervention demonstrate that QDs enter cells through clathrin-mediated endocytosis. HIP-55 can interact with clathrin and promote clathrin-mediated QDs endocytosis. Furthermore, HIP-55 ΔADF which is defective in F-actin binding fails to promote QDs endocytosis, indicating HIP-55 promotes clathrin-mediated QDs endocytosis depending on interaction with F-actin. In vivo, HIP-55 knockout also inhibits endocytosis of QDs. These findings reveal that HIP-55 acts as an intrinsic regulator for clathrin-mediated nanoparticle endocytosis, providing new insight into the nanoparticle internalization and a new strategy for nanodrug enrichment in target cells.

Exploring the potential and safety of quantum dots in allergy diagnostics

Biomedical investigations in nanotherapeutics and nanomedicine have recently intensified in pursuit of new therapies with improved efficacy. Quantum dots (QDs) are promising nanomaterials that possess a wide array of advantageous properties, including electronic properties, optical properties, and engineered biocompatibility under physiological conditions. Due to these characteristics, QDs are mainly used for biomedical labeling and theranostic (therapeutic-diagnostic) agents. QDs can be functionalized with ligands to facilitate their interaction with the immune system, specific IgE, and effector cell receptors. However, undesirable side effects such as hypersensitivity and toxicity may occur, requiring further assessment. This review systematically summarizes the potential uses of QDs in the allergy field. An overview of the definition and development of QDs is provided, along with the applications of QDs in allergy studies, including the detection of allergen-specific IgE (sIgE), food allergens, and sIgE in cellular tests. The potential treatment of allergies with QDs is also described, highlighting the toxicity and biocompatibility of these nanodevices. Finally, we discuss the current findings on the immunotoxicity of QDs. Several favorable points regarding the use of QDs for allergy diagnosis and treatment are noted.

Near infrared conjugated polymer nanoparticles (CPN™) for tracking cells using fluorescence and optoacoustic imaging

Tracking the biodistribution of cell therapies is crucial for understanding their safety and efficacy. Optical imaging techniques are particularly useful for tracking cells due to their clinical translatability and potential for intra-operative use to validate cell delivery. However, there is a lack of appropriate optical probes for cell tracking. The only FDA-approved material for clinical use is indocyanine green (ICG). ICG can be used for both fluorescence and photoacoustic imaging, but is prone to photodegradation, and at higher concentrations, undergoes quenching and can adversely affect cell health. We have developed novel near-infrared imaging probes comprising conjugated polymer nanoparticles (CPNs™) that can be fine-tuned to absorb and emit light at specific wavelengths. To compare the performance of the CPNs™ with ICG for in vivo cell tracking, labelled mesenchymal stromal cells (MSCs) were injected subcutaneously in mice and detected using fluorescence imaging (FI) and a form of photoacoustic imaging called multispectral optoacoustic tomography (MSOT). MSCs labelled with either ICG or CPN™ 770 could be detected with FI, but only CPN™ 770-labelled MSCs could be detected with MSOT. These results show that CPNs™ show great promise for tracking cells in vivo using optical imaging techniques, and for some applications, out-perform ICG.

Interactions between Quantum Dots and G-Actin

Quantum dots (QDs) are a type of nanoparticle with excellent optical properties, suitable for many optical-based biomedical applications. However, the potential of quantum dots to be used in clinical settings is limited by their toxicity. As such, much effort has been invested to examine the mechanism of QDs' toxicity. Yet, the current literature mainly focuses on ROS- and apoptosis-mediated cell death induced by QDs, which overlooks other aspects of QDs' toxicity. Thus, our study aimed to provide another way by which QDs negatively impact cellular processes by investigating the possibility of protein structure and function modification upon direct interaction. Through shotgun proteomics, we identified a number of QD-binding proteins, which are functionally associated with essential cellular processes and components, such as transcription, translation, vesicular trafficking, and the actin cytoskeleton. Among these proteins, we chose to closely examine the interaction between quantum dots and actin, as actin is one of the most abundant proteins in cells and plays crucial roles in cellular processes and structural maintenance. We found that CdSe/ZnS QDs spontaneously bind to G-actin in vitro, causing a static quenching of G-actin's intrinsic fluorescence. Furthermore, we found that this interaction favors the formation of a QD-actin complex with a binding ratio of 1:2.5. Finally, we also found that CdSe/ZnS QDs alter the secondary structure of G-actin, which may affect G-actin's function and properties. Overall, our study provides an in-depth mechanistic examination of the impact of CdSe/ZnS QDs on G-actin, proposing that direct interaction is another aspect of QDs' toxicity.

Current Advances in the Biomedical Applications of Quantum Dots: Promises and Challenges

Quantum dots (QDs) are a type of nanoparticle with exceptional photobleaching-resistant fluorescence. They are highly sought after for their potential use in various optical-based biomedical applications. However, there are still concerns regarding the use of quantum dots. As such, much effort has been invested into understanding the mechanisms behind the behaviors of QDs, so as to develop safer and more biocompatible quantum dots. In this mini-review, we provide an update on the recent advancements regarding the use of QDs in various biomedical applications. In addition, we also discuss# the current challenges and limitations in the use of QDs and propose a few areas of interest for future research.

Exocytosis of Nanoparticles: A Comprehensive Review

Both biomedical applications and safety assessments of manufactured nanomaterials require a thorough understanding of the interaction between nanomaterials and cells, including how nanomaterials enter cells, transport within cells, and leave cells. However, compared to the extensively studied uptake and trafficking of nanoparticles (NPs) in cells, less attention has been paid to the exocytosis of NPs. Yet exocytosis is an indispensable process of regulating the content of NPs in cells, which in turn influences, even decides, the toxicity of NPs to cells. A comprehensive understanding of the mechanisms and influencing factors of the exocytosis of NPs is not only essential for the safety assessment of NPs but also helpful for guiding the design of safe and highly effective NP-based materials for various purposes. Herein, we review the current status and progress of studies on the exocytosis of NPs. Firstly, we introduce experimental procedures and considerations. Then, exocytosis mechanisms/pathways are summarized with a detailed introduction of the main pathways (lysosomal and endoplasmic reticulum/Golgi pathway) and the role of microtubules; the patterns of exocytosis kinetics are presented and discussed. Subsequently, the influencing factors (initial content and location of intracellular NPs, physiochemical properties of NPs, cell type, and extracellular conditions) are fully discussed. Although there are inconsistent results, some rules are obtained, like smaller and charged NPs are more easily excreted. Finally, the challenges and future directions in the field have been discussed.

Cellular Localization, Aggregation, and Cytotoxicity of Bicelle-Quantum Dot Nanocomposites

Bicelles are discoidal lipid nanoparticles (LNPs) in which the planar bilayer and curved rim are, respectively, composed of long- and short-chain lipids. Bicellar LNPs have a hydrophobic core, allowing hydrophobic molecules and large molecular complexes such as quantum dots (QDs) to be encapsulated. In this study, CdSe/ZnS QDs were encapsulated in bicelles made of dipalmitoyl phosphatidylcholine, dihexanoyl phosphatidylcholine, dipalmitoyl phosphatidylglycerol, and distearoyl phosphatidylethanolamine conjugated with polyethylene glycerol amine 2000 to form a well-defined bicelle-QD nanocomplex (known as NANO²-QD or bicelle-QD). The bicelle-QD was then incubated with Hek293t cells and HeLa cells for different periods of time to determine changes in their cellular localization. Bicelle-QDs readily penetrated Hek293t cell membranes within 15 min of incubation, localized to the cytoplasm, and associated with mitochondria and intracellular vesicles. After 1 h, the bicelle-QDs enter the cell nucleus. Large aggregates form throughout the cell after 2 h and QDs are nearly absent from the nucleus by 4 h. Previous reports have demonstrated that CdSe/ZnS QDs can be toxic to cells, and we have found that encapsulating QDs in bicelles can attenuate but did not eliminate cytotoxicity. The present research outcome demonstrates the time-resolved pathway of bicelle-encapsulated QDs in Hek293t cells, morphological evolution in cells over time, and cytotoxicity of the bicelle-QDs, providing important insight into the potential application of the nanocomplex for cellular imaging.

Concentration-Dependent Cellular Uptake of Graphene Oxide Quantum Dots Promotes the Odontoblastic Differentiation of Dental Pulp Cells via the AMPK/mTOR Pathway

As zero-dimension nanoparticles, graphene oxide quantum dots (GOQDs) have broad potential for regulating cell proliferation and differentiation. However, such regulation of dental pulp cells (DPSCs) with different concentrations of GOQDs is insufficiently investigated, especially on the molecular mechanism. The purpose of this study was to explore the effect and molecular mechanism of GOQDs on the odontoblastic differentiation of DPSCs and to provide a theoretical basis for the repair of pulp vitality by pulp capping. CCK-8, immunofluorescence staining, alkaline phosphatase activity assay and staining, alizarin red staining, qRT-PCR, and western blotting were used to detect the proliferation and odontoblastic differentiation of DPSC coculturing with different concentrations of GOQDs. The results indicate that the cellular uptake of low concentration of GOQDs (0.1, 1, and 10 μg/mL) could promote the proliferation and odontoblastic differentiation of DPCSs. Compared with other concentration groups, 1 μg/mL GOQDs show better ability in such promotion. In addition, with the activation of the AMPK signaling pathway, the mTOR signaling pathway was inhibited in DPSCs after coculturing with GOQDs, which indicates that low concentrations of GOQDs could regulate the odontoblastic differentiation of DPSCs by the AMPK/mTOR signaling pathway.

Red CdSe/ZnS QDs' Intracellular Trafficking and Its Impact on Yeast Polarization and Actin Filament

Quantum dots are nanoparticles (2-10 nm) that emit strong and tunable fluorescence. Quantum dots have been heavily used in high-demand commercialized products, research, and for medical purposes. Emerging concerns have demonstrated the negative impact of quantum dots on living cells; however, the intracellular trafficking of QDs in yeast cells and the effect of this interaction remains unclear. The primary goal of our research is to investigate the trafficking path of red cadmium selenide zinc sulfide quantum dots (CdSe/ZnS QDs) in Saccharomyces cerevisiae and the impact QDs have on yeast cellular dynamics. Using cells with GFP-tagged reference organelle markers and confocal microscopy, we were able to track the internalization of QDs. We found that QDs initially aggregate at the exterior of yeast cells, enter the cell using clathrin-receptor-mediated endocytosis, and distribute at the late Golgi/trans-Golgi network. We also found that the treatment of red CdSe/ZnS QDs resulted in growth rate reduction and loss of polarized growth in yeast cells. Our RNA sequence analysis revealed many altered genes. Particularly, we found an upregulation of DID2, which has previously been associated with cell cycle arrest when overexpressed, and a downregulation of APS2, a gene that codes for a subunit of AP2 protein important for the recruitment of proteins to clathrin-mediated endocytosis vesicle. Furthermore, CdSe/ZnS QDs treatment resulted in a slightly delayed endocytosis and altered the actin dynamics in yeast cells. We found that QDs caused an increased level of F-actin and a significant reduction in profilin protein expression. In addition, there was a significant elevation in the amount of coronin protein expressed, while the level of cofilin was unchanged. Altogether, this suggests that QDs favor the assembly of actin filaments. Overall, this study provides a novel toxicity mechanism of red CdSe/ZnS QDs on yeast actin dynamics and cellular processes, including endocytosis.

Endocytosis, Distribution, and Exocytosis of Polystyrene Nanoparticles in Human Lung Cells

Nanoplastics, one component of plastic pollution, can enter human bodies via inhalation and thus threaten human health. However, the knowledge about the uptake and exocytosis of nanoplastics in cells of human lung organs is still very limited. Herein, we investigated the endocytosis, distribution, and exocytosis of polystyrene nanoparticles (PS NPs) of 50 nm (G50PS) and 100 nm (R100PS) in A549 cells and BEAS-2B cells. We found that both the cellular uptake of PS NPs increased positively with exposure time and dose, and A549 cells ingested more PS NPs than BEAS-2B cells did. In addition, the intracellular content of G50PS was higher than that of R100PS except at a higher dose and longer time. The ingested PS NPs were distributed mainly in lysosomes, while many G50PS appeared around the cell membrane, and R100PS also accumulated in mitochondria in BEAS-2B cells. As for the exocytosis, R100PS was more difficult to excrete than G50PS. Lysosomes in A549 cells and actin and microtubule in BEAS-2B cells were involved in the exocytosis of the PS NPs. These findings provide detailed information about the translocation of nanoplastics in lung cells, which is valuable for the safety assessment of nanoplastics in the environment.

Quantum Dots and Their Interaction with Biological Systems

Quantum dots are nanocrystals with bright and tunable fluorescence. Due to their unique property, quantum dots are sought after for their potential in several applications in biomedical sciences as well as industrial use. However, concerns regarding QDs’ toxicity toward the environment and other biological systems have been rising rapidly in the past decade. In this mini-review, we summarize the most up-to-date details regarding quantum dots’ impacts, as well as QDs’ interaction with mammalian organisms, fungal organisms, and plants at the cellular, tissue, and organismal level. We also provide details about QDs’ cellular uptake and trafficking, and QDs’ general interactions with biological structures. In this mini-review, we aim to provide a better understanding of our current standing in the research of quantum dots, point out some knowledge gaps in the field, and provide hints for potential future research.

QD:Puf Nanohybrids Are Compatible with Studies in Cells

Colloidal semiconductor quantum dots (QD), as well as other nanoparticles, are useful in cell studies as fluorescent labels. They may also be used as more active components in various cellular assays, serving as sensors or effectors. However, not all QDs are biocompatible. One of the main problems is their outer coat, which needs to be stable and to sustain hydrophilicity. Here we show that purpose-designed CdSe QDs, covered with a Puf protein, can be efficiently accumulated by HeLa cells. The uptake was measurable after a few hours of incubation with nanoparticles and most of the fluorescence was localised in the internal membrane system of the cell, including the endoplasmic reticulum and the Golgi apparatus. The fluorescence properties of QDs were mostly preserved, although the maximum emission wavelength was slightly shifted, and the fluorescence lifetime was shortened, indicating partial sensitivity of the QDs to the cell microenvironment. QD accumulation resulted in a decrease in cell viability, which was attributed to disturbance of endoplasmic reticulum performance.

On the Cellular Uptake and Exocytosis of Carbon Dots─Significant Cell Type Dependence and Effects of Cell Division

Understanding the cellular uptake and exocytosis processes of nanoparticles (NPs) is essential for developing the nanomedicines and assessing the health risk of nanomaterials. Considerable efforts have been made to reveal how physicochemical properties of NPs influence these processes. However, little attention has been paid to how cell type impacts these processes, especially exocytosis. Herein, the uptake and exocytosis of the carbon dots (CDs) obtained from the carbonization of citric acid with polyethylenimine (PEI) oligomers (CDs-PEI) in five human cell lines (HeLa, A549, BEAS-2B, A431, and MDA-MB-468) are analyzed to understand how cell type influences the fate of CDs in cells. The cell division is taken into account by the correction of cell number for accurate quantification of the uptake and exocytosis of CDs-PEI. The results indicate that the cell type significantly affects the cellular uptake, trafficking, and exocytosis of CDs-PEI. Among the cell types investigated, MDA-MB-468 cells have the greatest capacity for both uptake and exocytosis, and HeLa cells have the least capacity. The kinetics of the exocytosis largely follows a single exponential decay function, with the remaining CDs-PEI in cells reaching plateaus within 24 h. The kinetic parameters are cell-dependent but insensitive to the initial intracellular CDs-PEI content. Generally, the Golgi apparatus pathways are more important in exocytosis than the lysosomal pathway, and the locations of CDs-PEI in the beginning of exocytosis are not correlated with their exocytosis pathways. The findings on the cell type-dependent cellular uptake and exocytosis reported here may be valuable to the future design of high-performance and safe CDs and related nanomaterials in general.

Semiconductor quantum dots for photodynamic therapy: Recent advances

Photodynamic therapy is a promising cancer treatment that induces apoptosis as a result of the interactions between light and a photosensitizing drug. Lately, the emergence of biocompatible nanoparticles has revolutionized the prospects of photodynamic therapy (PDT) in clinical trials. Consequently, a lot of research is now being focused on developing non-toxic, biocompatible nanoparticle-based photosensitizers for effective cancer treatments using PDT. In this regard, semiconducting quantum dots have shown encouraging results. Quantum dots are artificial semiconducting nanocrystals with distinct chemical and physical properties. Their optical properties can be fine-tuned by varying their size, which usually ranges from 1 to 10 nm. They present many advantages over conventional photosensitizers, mainly their emission properties can be manipulated within the near IR region as opposed to the visible region by the former. Consequently, low intensity light can be used to penetrate deeper tissues owing to low scattering in the near IR region. Recently, successful reports on imaging and PDT of cancer using carbon (carbon, graphene based) and metallic (Cd based) based quantum dots are promising. This review aims to summarize the development and the status quo of quantum dots for cancer treatment.

In vitro effects of combustion generated carbon dots on cellular parameters in healthy and cancerous breast cells

Carbon nanomaterials are an inventive class of materials with wide applications in state-of-the-art bioimaging and therapeutics. They allow a broad range of tunable and integrated advantages of structural flexibility, chemical and thermal stability, upright electrical conductivity, and the option of scale-up and mass production. In the context of nanomedicine, carbon nanomaterials have been used extensively to mitigate the serious side effects of conventional chemotherapy and also to enable early cancer diagnostics, given their wide range of tunable properties. A class of carbon nanomaterials, called carbon dots (CDs) are small carbon-based nanoparticles and have been a valued discovery due to their photoluminescence, low photobleaching, and high surface area to mass ratio. The process of producing these CDs had so far been a high energy demanding process involving wet chemistry for purification. A one-step tunable production of luminescent CDs from fuel rich combustion reactors was recently presented by our group. In this paper, we explore the effects of these yellow luminescent combustion-generated CDs in MCF7 adenocarcinoma and MCF10a normal breast epithelial cells. We observed that these CDs, also at nontoxic doses, can affect basic cellular functions, such as cell cycle and proliferation; induce substantial changes on the physical parameters of the plasma membrane; and change the overall appearance of a cell in terms of morphology.

Intracellular Trafficking and Distribution of Cd and InP Quantum Dots in HeLa and ML-1 Thyroid Cancer Cells

The study of the interaction of engineered nanoparticles, including quantum dots (QDs), with cellular constituents and the kinetics of their localization and transport, has provided new insights into their biological consequences in cancers and for the development of effective cancer therapies. The present study aims to elucidate the toxicity and intracellular transport kinetics of CdSe/ZnS and InP/ZnS QDs in late-stage ML-1 thyroid cancer using well-tested HeLa as a control. Our XTT (2,3-bis-(2-methoxy-4-nitro-5-sulfophenyl)-2H-tetrazolium-5-carboxanilide) viability assay (Cell Proliferation Kit II) showed that ML-1 cells and non-cancerous mouse fibroblast cells exhibit no viability defect in response to these QDs, whereas HeLa cell viability decreases. These results suggest that HeLa cells are more sensitive to the QDs compared to ML-1 cells. To test the possibility that transporting rates of QDs are different between HeLa and ML-1 cells, we performed a QD subcellular localization assay by determining Pearson’s Coefficient values and found that HeLa cells showed faster QDs transporting towards the lysosome. Consistently, the ICP-OES test showed the uptake of CdSe/ZnS QDs in HeLa cells was significantly higher than in ML-1 cells. Together, we conclude that high levels of toxicity in HeLa are positively correlated with the traffic rate of QDs in the treated cells.