Functionalized quantum dots induce proinflammatory responses in vitro: the role of terminal functional group-associated endocytic pathways

Applicability of Quantum Dots in Breast Cancer Diagnostic and Therapeutic Modalities-A State-of-the-Art Review

The increasing incidence of breast cancers (BCs) in the world population and their complexity and high metastatic ability are serious concerns for healthcare systems. Despite the significant progress in medicine made in recent decades, the efficient treatment of invasive cancers still remains challenging. Chemotherapy, a fundamental systemic treatment method, is burdened with severe adverse effects, with efficacy limited by resistance development and risk of disease recurrence. Also, current diagnostic methods have certain drawbacks, attracting attention to the idea of developing novel, more sensitive detection and therapeutic modalities. It seems the solution for these issues can be provided by nanotechnology. Particularly, quantum dots (QDs) have been extensively evaluated as potential targeted drug delivery vehicles and, simultaneously, sensing and bioimaging probes. These fluorescent nanoparticles offer unlimited possibilities of surface modifications, allowing for the attachment of biomolecules, such as antibodies or proteins, and drug molecules, among others. In this work, we discuss the potential applicability of QDs in breast cancer diagnostics and treatment in light of the current knowledge. We begin with introducing the molecular and histopathological features of BCs, standard therapeutic regimens, and current diagnostic methods. Further, the features of QDs, along with their uptake, biodistribution patterns, and cytotoxicity, are described. Based on the reports published in recent years, we present the progress in research on possible QD use in improving BC diagnostics and treatment efficacy as chemotherapeutic delivery vehicles and photosensitizing agents, along with the stages of their development. We also address limitations and open questions regarding this topic.

Cytotoxicity of Quantum Dots in Receptor-Mediated Endocytic and Pinocytic Pathways in Yeast

Despite the promising applications of the use of quantum dots (QDs) in the biomedical field, the long-lasting effects of QDs on the cell remain poorly understood. To comprehend the mechanisms underlying the toxic effects of QDs in yeast, we characterized defects associated with receptor-mediated endocytosis (RME) as well as pinocytosis using Saccharomyces cerevisiae as a model in the presence of cadmium selenide/zinc sulfide (CdSe/ZnS) QDs. Our findings revealed that QDs led to an inefficient RME at the early, intermediate, and late stages of endocytic patch maturation at the endocytic site, with the prolonged lifespan of GFP fused yeast fimbrin (Sac6-GFP), a late marker of endocytosis. The transit of FM1-43, a lipophilic dye from the plasma membrane to the vacuole, was severely retarded in the presence of QDs. Finally, QDs caused an accumulation of monomeric red fluorescent protein fused carbamoyl phosphate synthetase 1 (mRFP-Cps1), a vacuolar lumen marker in the vacuole. In summary, the present study provides novel insights into the possible impact of CdSe/ZnS QDs on the endocytic machinery, enabling a deeper comprehension of QD toxicity.

Enhancing silk fibroin structures and applications through angle-dependent Ar+ plasma treatment

This study tackles limitations of Silk Fibroin (SF), including availability of sites for modification. This is achieved by Direct Plasma Nanosynthesis (DPNS), an Ar+ bombardment method, to generate and modify nanostructures and nanoscale properties on the SF surface. SF samples were treated with DPNS at incidence angles of 45o and 60o, with specific ion dose and energy parameters (1 × 1018 ions/cm2 and 500 eV, respectively) maintained throughout the process. Fourier-transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS) primarily underscored transformations in SF's nitrogenous components. Specifically, treatment produced a boost in C-NH2, particularly pronounced in the 45o-treated samples, suggesting changes were more superficial than alterations to the secondary structure. The DPNS treatment gave rise to periodic nanocone structures on the SF surface, with a scale increase correlated to a higher angle of incidence. This resulted in a decrease in surface stiffness and significant changes in the motility of J774 macrophages interacting with the transformed SF. Furthermore, the SF samples treated at a 60o incidence showcased a confinement effect, moderating the macrophages' motility, morphology, and inflammatory response. The DPNS-induced alterations not only mitigate SF's limitations but also affect cellular behavior, expanding potential for SF in biomaterials.

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.

Cellular uptake, intracellular behavior, and acute/sub-acute cytotoxicity of a PEG-modified quantum dot with promising in-vivo biomedical applications

Quantum Dots (QDs) modified with branched Polyethylene Glycol-amine (6- or 8-arm PEG-amine) coupled with methoxy PEG (mPEG) hold great promise for in vivo biomedical applications due to a long half-life in blood and negligible toxicity. However, the potential risks regarding their concomitant prolonged co-incubation with cardiovascular and blood cells remains inconclusive. In the present study, the feasible, effective and convenient proliferating-restricted cell line models representing the circulatory system were established to investigate the cellular internalization followed by intracellular outcomes and resulting acute/sub-acute cytotoxicity of the 6-arm PEG-amine/mPEG QDs. We found a dose-, time- and cell type-dependent cellular uptake of the 6-arm PEG-amine/mPEG QDs, which was ten-fold lower compared to the traditional linear PEG-modified counterpart. The QDs entered cells via multiple endocytic pathways and were mostly preserved in Golgi apparatus for at least one week instead of degradation in lysosomes, resulting in a minimal acute cytotoxicity, which is much lower than other types of PEG-modified QDs previously reported. However, a sub-acute cytotoxicity of QDs were observed several days post exposure using the concentrations eliciting no-significant acute cytotoxic effects, which was associated with elevated ROS generation caused by QDs remained inside cells. Finally, a non-cytotoxic concentration of the QDs was identified at the sub-acute cytotoxic level. Our study provided important information for clinical translation of branched PEG-amine/mPEG QDs by elucidating the QDs-cell interactions and toxicity mechanism using the proliferation-restricted cell models representing circulatory system. What's more, we emphasized the indispensability of sub-acute cytotoxic effects in the whole biosafety evaluation process of nanomaterials like QDs.

An overview of quantum dots-induced immunotoxicity and the underlying mechanisms

Quantum dots (QDs) have bright luminescence and excellent photostability. New synthesis techniques and strategies also enhance QDs properties for specific applications. With the continuous expansion of the applications, QDs-mediated immunotoxicity has become a major concern. The immune system has been confirmed to be an important target organ of QDs and is sensitive to QDs. Herein, review immunotoxic effects caused by QDs and the underlying mechanisms. Firstly, QDs exposure-induced modulation in immune cell maturation and differentiation is summarized, especially pre-exposed dendritic cells (DCs) and their regulatory roles in adaptive immunity. Cytokines are usually recognized as biomarkers of immunotoxicity, therefore, variation of cytokines mediated by QDs is also highlighted. Moreover, the activation of the complement system induced by QDs is discussed. Accumulated results have suggested that QDs disrupt the immune response by regulating intracellular oxidative stress (reactive oxygen species) levels, autophagy formation, and expressions of pro-inflammatory mediators. Furthermore, several signalling pathways play a key role in the disruption. Finally, some difficulties worthy of further consideration are proposed. Because there are still challenges in biomedical and clinical applications, this review hopes to provide information that could be useful in exploring the mechanisms associated with QD-induced immunotoxicity.

Design of Smart Nanodiamonds: Introducing pH Sensitivity to Improve Nucleic Acid Carrier Efficiency of Diamoplexes

The mechanism of cellular uptake and intracellular fate of nanodiamond/nucleic acid complexes (diamoplexes) are major determinants of its performance as a gene carrier. Our group designed lysine-nanodiamonds (K-NDs) as vectors for nucleic acid delivery. In this work, we modified the surface of K-NDs with histidine to overcome endo-lysosomal entrapment diamoplexes, the major rate limiting step in gene transfer. Histidine is conjugated onto the NDs in two configurations: lysyl-histidine-NDs (HK-NDs) where histidine is loaded on 100% of the lysine moieties and lysine/lysyl-histidine-NDs (H50K50-NDs) where histidine is loaded on 50% of the lysine moieties. Both HK-NDs and H50K50-NDs maintained the optimum size distribution (i.e., <200 nm) and a cationic surface (zeta potential > 20 mV), similar to K-NDs. HK-NDs binds plasmid deoxyribonucleic acid (pDNA) and small interfering ribonucleic acid (siRNA) forming diamoplexes at mass ratios of 10:1 and 60:1, respectively. H50K50-NDs significantly improved nucleic acid binding, forming diamoplexes at a 2:1 mass ratio with pDNA and a 30:1 mass ratio with siRNA, which are at values similar to the K-NDs. The amount of histidine on the surface also impacted the interactions with mammalian cells. The HK-NDs reduced the cell viability by 30% at therapeutic concentrations, while H50K50-NDs maintained more than 90% cell viability, even at the highest concentrations. H50K50-NDs also showed highest cellular uptake within 24 h, followed by K-NDs and HK-NDs. Most functionalized NDs show cellular exit after 5 days, leaving less than 10% of cells with internalized diamonds. The addition of histidine to the ND resulted in higher transfection of anti-green fluorescent protein siRNA (anti-GFP siRNA) with the fraction of GFP knockdown being 0.8 vs. 0.6 for K-NDs at a mass ratio of 50:1. H50K50-NDs further improved transfection by achieving a similar fraction of GFP knockdown (0.8) at a lower mass ratio of 30:1. Overall, this study provides evidence that the addition of histidine, a pH-modulating entity in the functionalization design at an optimized ratio, renders high efficiency to the diamoplexes. Further studies will elucidate the uptake mechanism and intracellular fate to build the relationship between physicochemical characteristics and biological efficacy and create a platform for solid-core nanoparticle-based gene delivery.

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.

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

Semiconductor quantum dots (QDs) have been extensively explored for extensive bioapplications, yet their cellular fate, especially exocytosis, has not been thoroughly investigated. Herein, we systematically investigated the whole cellular process from the endocytosis, intercellular trafficking, to the exocytosis of a typical QD, core/shell CdSe/ZnS QD. Using confocal laser scanning microscopy and flow cytometry, and after carefully eliminating the effect of cell division, we found that the QDs were internalized by HeLa cells with a time-, dose-, and serum-dependent manner. The cellular uptake was inhibited by serum, but eventually peaked after 4-6 h incubation with or without serum. The primary endocytosis pathway was clathrin-mediated, and actin- and microtubule-dependent in the medium with serum, while the caveolae-mediated endocytosis and macropinocytosis were more important for the QDs in the serum-free medium. Inside cells, most QDs distributed in lysosomes, and some entered mitochondria, endoplasmic reticulum, and Golgi apparatus. The translocation of the QDs from other organelles to Golgi apparatus was observed. The exocytosis of QDs was faster than the endocytosis, reaching the maximum in about one hour after cultured in fresh culture medium, with around 60% of the internalized QDs remained undischarged. The exocytosis process was energy- and actin-dependent, and the lysosome exocytosis and endoplasmic reticulum/Golgi pathway were the main routes. This study provides a full picture of behavior and fate of QDs in cells, which may facilitate the design of ideal QDs applied in biomedical and other fields.

Luminescent copper indium sulfide (CIS) quantum dots for bioimaging applications

Copper indium sulfide (CIS) quantum dots are ideal for bioimaging applications, by being characterized by high molar absorption coefficients throughout the entire visible spectrum, high photoluminescence quantum yield, high tolerance to the presence of lattice defects, emission tunability from the red to the near-infrared spectral region by changing their dimensions and composition, and long lifetimes (hundreds of nanoseconds) enabling time-gated detection to increase signal-to-noise ratio. The present review collects: (i) the most common procedures used to synthesize stable CIS QDs and the possible strategies to enhance their colloidal stability in aqueous environment, a property needed for bioimaging applications; (ii) their photophysical properties and parameters that affect the energy and brightness of their photoluminescence; (iii) toxicity and bioimaging applications of CIS QDs, including tumor targeting, time-gated detection and multimodal imaging, as well as theranostics. Future perspectives are analyzed in view of advantages and potential limitations of CIS QDs compared to most traditional QDs.

The Effect of Chemical Structure of OEG Ligand Shells with Quaternary Ammonium Moiety on the Colloidal Stabilization, Cellular Uptake and Photothermal Stability of Gold Nanorods

PURPOSE

Plasmonic photothermal cancer therapy by gold nanorods (GNRs) emerges as a promising tool for cancer treatment. The goal of this study was to design cationic oligoethylene glycol (OEG) compounds varying in hydrophobicity and molecular electrostatic potential as ligand shells of GNRs. Three series of ligands with different length of OEG chain (ethylene glycol units = 3, 4, 5) and variants of quaternary ammonium salts (QAS) as terminal functional group were synthesized and compared to a prototypical quaternary ammonium ligand with alkyl chain - (16-mercaptohexadecyl)trimethylammonium bromide (MTAB).

METHODS

Step-by-step research approach starting with the preparation of compounds characterized by NMR and HRMS spectra, GNRs ligand exchange evaluation through characterization of cytotoxicity and GNRs cellular uptake was used. A method quantifying the reshaping of GNRs was applied to determine the effect of ligand structure on the heat transport from GNRs under fs-laser irradiation.

RESULTS

Fourteen out of 18 synthesized OEG compounds successfully stabilized GNRs in the water. The colloidal stability of prepared GNRs in the cell culture medium decreased with the number of OEG units. In contrast, the cellular uptake of OEG+GNRs by HeLa cells increased with the length of OEG chain while the structure of the QAS group showed a minor role. Compared to MTAB, more hydrophilic OEG compounds exhibited nearly two order of magnitude lower cytotoxicity in free state and provided efficient cellular uptake of GNRs close to the level of MTAB. Regarding photothermal properties, OEG compounds evoked the photothermal reshaping of GNRs at lower peak fluence (14.8 mJ/cm2) of femtosecond laser irradiation than the alkanethiol MTAB.

CONCLUSION

OEG+GNRs appear to be optimal for clinical applications with systemic administration of NPs not-requiring irradiation at high laser intensity such as drug delivery and photothermal therapy inducing apoptosis.

Carbon Dot Nanoparticles: Exploring the Potential Use for Gene Delivery in Ophthalmic Diseases

Ocular gene therapy offers significant potential for preventing retinal dystrophy in patients with inherited retinal dystrophies (IRD). Adeno-associated virus (AAV) based gene transfer is the most common and successful gene delivery approach to the eye. These days, many studies are using non-viral nanoparticles (NPs) as an alternative therapeutic option because of their unique properties and biocompatibility. Here, we discuss the potential of carbon dots (CDs), a new type of nanocarrier for gene delivery to the retinal cells. The unique physicochemical properties of CDs (such as optical, electronic, and catalytic) make them suitable for biosensing, imaging, drug, and gene delivery applications. Efficient gene delivery to the retinal cells using CDs depends on various factors, such as photoluminescence, quantum yield, biocompatibility, size, and shape. In this review, we focused on different approaches used to synthesize CDs, classify CDs, various pathways for the intake of gene-loaded carbon nanoparticles inside the cell, and multiple studies that worked on transferring nucleic acid in the eye using CDs.

The cytotoxicity of core-shell or non-shell structure quantum dots and reflection on environmental friendly: A review

Quantum dots are widely applicated into bioindustry and research owing to its superior properties such as broad excitation spectra, narrow bandwidth emission spectra and high resistance to photo-bleaching. However, the toxicity of quantum dots should not be underestimated and aroused widespread concern. The surface properties and size of quantum dots are critical relevant properties on toxicity. Then, the core/shell structure becomes one common way to affect the activity of quantum dots such as enhance biocompatibility and stability. Except those toxicity it induced, the problem it brought into the environment such as the degradation of quantum dot similarly becomes a hot issue. This review initially took a brief scan of current research on the cytotoxicity of QDs and the mechanism behind that over the past five years. Mainly discussion concentrated on the diversity of structure on quantum dots whether played a key role on the cytotoxicty of quantum dots. It also discussed the role of different shells with metal or nonmetal cores and the influence on the environment.

Pulmonary siRNA delivery for lung disease: Review of recent progress and challenges

Lung diseases are a leading cause of mortality worldwide and there exists urgent need for new therapies. Approval of the first siRNA treatments in humans has opened the door for further exploration of this therapeutic strategy for other disease states. Pulmonary delivery of siRNA-based biopharmaceuticals offers the potential to address multiple unmet medical needs in lung-related diseases because of the specific physiology of the lung and characteristic properties of siRNA. Inhalation-based siRNA delivery designed for efficient, targeted delivery to specific cells within the lung holds great promise. Efficient delivery of siRNA directly to the lung, however, is relatively complex. This review focuses on the barriers that impact pulmonary siRNA delivery and successful recent approaches to advance this field forward. We focus on the pulmonary barriers that affect siRNA delivery, the disease-dependent pathological changes and their role in pulmonary disease and impact on siRNA delivery, as well as the recent development on the pulmonary siRNA delivery systems.

Toxicity evaluation of cadmium-containing quantum dots: A review of optimizing physicochemical properties to diminish toxicity

Fluorescent quantum dots (QDs) have received extensive attention because of their excellent optical properties and wide utilization in biological and biomedical areas. Nonetheless, there have been intense concerns on the cytotoxicity assessment of cadmium-containing QDs due to free cadmium ions release and nano-size effects. This paper reviews the representative synthetic strategies for preparation of cadmium-containing QDs and their applications. Then the toxicity assessments of QDs from cell studies to animal models are discussed, which can aid in improving our understanding of the cytotoxicity of QDs, and the toxicity mechanism is proposed. Several critical physicochemical properties of QDs are discussed and suggestions are provided for optimizing QDs design in view of minimal cytotoxicity. Finally, accurate detection techniques and systematic methodologies for the toxicity assessment of QDs are expected to achieve further breakthroughs in the future, especially in-situ, real-time, and rapid quantitative analysis methods.

Co-delivery of 5-fluorouracil and miRNA-34a mimics by host-guest self-assembly nanocarriers for efficacious targeted therapy in colorectal cancer patient-derived tumor xenografts

Rationale: A co-delivery system that can transport chemotherapeutic drugs and nucleotide drugs to distinct targets in tumors is an attractive strategy for cancer therapy. In this study, well-defined targeted quantum dot (QD)-based multifunctional nanocarriers were developed through self-assembly driven by host-guest interactions. 5-fluorouracil (5-FU) and microRNA-34a mimics (miR-34a(m)) were co-administered to achieve synergistic effects for colorectal cancer (CRC) therapy for the first time. Furthermore, the CRC patient-derived tumor xenograft (PDX) model, which closely mimics human CRC tumor pathological properties, was used for evaluating the therapeutic effect in this research.

Methods: Multiple β-cyclodextrin (CD)-attached QD nanoparticles were used as host molecules. An adamantane (ADA)-modified TCP1 peptide-targeting ligand (TCP1) was used as the guest molecule. 5-FU and miR-34a(m) were loaded into TCP1-CD-QD nanocarriers, which were used to treat CRC in vitro and in vivo. In addition, the CRC PDX model was used to evaluate the treatment efficacy of this co-delivery system.

Results: 5-FU and miR-34a(m) can be efficiently encapsulated into TCP1-CD-QD nanocarriers and delivered into CRC cells, which led to the inhibition of the proliferation and migration of CRC cells in vitro and suppression of tumor growth in a CRC cell-derived tumor xenograft model. The obtained data further suggested that co-delivery of 5-FU and miR-34a(m) could achieve synergistic effects for CRC therapy. Notably, targeted therapy via the co-delivery of 5-FU and miR-34a(m) by TCP1-CD-QD nanocarriers significantly inhibited the growth of PDX tumors.

Conclusions: These studies strongly indicate that such a nanocarrier-based co-delivery system is a promising combined therapeutic strategy that utilizes chemotherapeutic drugs and nucleotide drugs for enhancing colorectal cancer targeting and synergistic therapy.

Graphene Quantum Dots' Surface Chemistry Modulates the Sensitivity of Glioblastoma Cells to Chemotherapeutics

Recent evidence has shown that graphene quantum dots (GQDs) are capable of crossing the blood-brain barrier, the barrier that reduces cancer therapy efficacy. Here, we tested three alternative GQDs' surface chemistries on two neural lineages (glioblastoma cells and mouse cortical neurons). We showed that surface chemistry modulates GQDs' biocompatibility. When used in combination with the chemotherapeutic drug doxorubicin, GDQs exerted a synergistic effect on tumor cells, but not on neurons. This appears to be mediated by the modification of membrane permeability induced by the surface of GQDs. Our findings highlight that GQDs can be adopted as a suitable delivery and therapeutic strategy for the treatment of glioblastoma, by both directly destabilizing the cell membrane and indirectly increasing the efficacy of chemotherapeutic drugs.

Biological responses to physicochemical properties of biomaterial surface

Biomedical scientists use chemistry-driven processes found in nature as an inspiration to design biomaterials as promising diagnostic tools, therapeutic solutions, or tissue substitutes. While substantial consideration is devoted to the design and validation of biomaterials, the nature of their interactions with the surrounding biological microenvironment is commonly neglected. This gap of knowledge could be owing to our poor understanding of biochemical signaling pathways, lack of reliable techniques for designing biomaterials with optimal physicochemical properties, and/or poor stability of biomaterial properties after implantation. The success of host responses to biomaterials, known as biocompatibility, depends on chemical principles as the root of both cell signaling pathways in the body and how the biomaterial surface is designed. Most of the current review papers have discussed chemical engineering and biological principles of designing biomaterials as separate topics, which has resulted in neglecting the main role of chemistry in this field. In this review, we discuss biocompatibility in the context of chemistry, what it is and how to assess it, while describing contributions from both biochemical cues and biomaterials as well as the means of harmonizing them. We address both biochemical signal-transduction pathways and engineering principles of designing a biomaterial with an emphasis on its surface physicochemistry. As we aim to show the role of chemistry in the crosstalk between the surface physicochemical properties and body responses, we concisely highlight the main biochemical signal-transduction pathways involved in the biocompatibility complex. Finally, we discuss the progress and challenges associated with the current strategies used for improving the chemical and physical interactions between cells and biomaterial surface.

Cytotoxicity-Related Bioeffects Induced by Nanoparticles: The Role of Surface Chemistry

Nanoparticles (NPs) are widely used in a variety of fields, including those related to consumer products, architecture, energy, and biomedicine. Once they enter the human body, NPs contact proteins in the blood and interact with cells in organs, which may induce cytotoxicity. Among the various factors of NP surface chemistry, surface charges, hydrophobicity levels and combinatorial decorations are found to play key roles inregulating typical cytotoxicity-related bioeffects, including protein binding, cellular uptake, oxidative stress, autophagy, inflammation, and apoptosis. In this review, we summarize the recent progress made in directing the levels and molecular pathways of these cytotoxicity-related effects by the purposeful design of NP surface charge, hydrophobicity, and combinatorial decorations.

Quantum Dot Cellular Uptake and Toxicity in the Developing Brain: Implications for Use as Imaging Probes

Nanometer-sized luminescent semiconductor quantum dots (QDs) have been utilized as imaging and therapeutic agents in a variety of disease settings, including diseases of the central nervous system. QDs have several advantages over traditional fluorescent probes including their small size (5-10 nm), tunable excitation and emission spectra, tailorable surface functionality, efficient photoluminescence, and robust photostability, which are ideal characteristics for in vivo imaging. Although QDs are promising imaging agents in brain-related applications, no systematic evaluation of QD behavior in brain-relevant conditions has yet been done. Therefore, we sought to investigate QD colloidal stability, cellular uptake, and toxicity in vitro, ex vivo, and in vivo in the brain environment. We found that QD behavior is highly dependent on surface functionality and that treatment of cultured organotypic whole hemisphere (OWH) slices with QDs results in dose-dependent toxicity and metallothionein increase, but no subsequent mRNA expression level changes in inflammatory cytokines or other oxidative stress. QDs coated with poly(ethylene glycol) (PEG) were protected from aggregation in neurophysiologically relevant fluids and in tissue, allowing for greater penetration. Importantly, QD behavior differed in cultured slices as compared to monolayer cell cultures, and behavior in cultured slices aligned more closely with that seen in vivo. Irrespective of surface chemistry and brain-relevant platform, non-aggregated QDs were primarily internalized by microglia in a region-dependent manner both in slices and in vivo upon systemic administration. This knowledge will help guide further engineering of candidate QD-based imaging probes for neurological application.

Distribution of polymer-coated gold nanoparticles in a 3D lung model and indication of apoptosis after repeated exposure

AIM

The distribution and impact of aerosol-delivered gold nanoparticles (AuNPs) functionalized with a mixture of aminated-polyvinyl alcohol and amino-PEG ([polyvinyl alcohol/PEG]-NH₂) upon repeated administration onto a 3D lung model were explored.

MATERIALS & METHODS

AuNPs were aerosolized and uptake and epithelial translocation was assessed by inductively coupled plasma optical-emission spectroscopy, flow cytometry and electron microscopy. In addition, cytotoxicity, apoptosis and proinflammation were evaluated.

RESULTS

Repeated AuNP aerosolization resulted in NP accumulation in macrophages and epithelial cells. Dendritic cells demonstrated substantial NP internalization after single administration which was reduced in later time points. No cytotoxicity or proinflammation was observed but after 96 h significant apoptosis was induced by the polymer coating.

CONCLUSION

These results indicate the importance of repeated exposures in addressing potential effects of NPs.

In vitro to in vivo benchmark dose comparisons to inform risk assessment of quantum dot nanomaterials

Engineered nanomaterials are currently under review for their potential toxicity; however, their use in consumer/commercial products has continued to outpace risk assessments. In vitro methods may be utilized as tools to improve the efficiency of risk assessment approaches. We propose a framework to compare relationships between previously published in vitro and in vivo toxicity assessments of cadmium-selenium containing quantum dots (QDs) using benchmark dose (BMD) and dosimetric assessment methods. Although data were limited this approach was useful for identifying sensitive assays and strains. In vitro studies assessed effects of QDs in three pulmonary cell types across two mouse strains. Significant dose-response effects were modeled and a standardized method of BMD analysis was performed as a function of both exposure dose and dosimetric dose. In vivo studies assessed pulmonary effects of QD exposure across eight mouse strains. BMD analysis served as a basis for relative comparison with in vitro studies. We found consistent responses in common endpoints between in vitro and in vivo studies. Strain sensitivity was consistent between in vitro and in vivo studies, showing A/J mice more sensitive to QDs. Cell types were found to differentially take up QDs. Dosimetric adjustments identified similar sensitivity among cell types. Thus, BMD analysis can be used as an effective tool to compare the sensitivity of different strains, cell types, and assays to QDs. These methods allow for in vitro assays to be used to predict in vivo responses, improve the efficiency of in vivo studies, and allow for prioritization of nanomaterial assessments. This article is categorized under: Toxicology and Regulatory Issues in Nanomedicine > Toxicology of Nanomaterials Toxicology and Regulatory Issues in Nanomedicine > Regulatory and Policy Issues in Nanomedicine.

pH-sensitive polymer-modified liposome-based immunity-inducing system: Effects of inclusion of cationic lipid and CpG-DNA

Efficient vaccine carriers for cancer immunotherapy require two functions: antigen delivery to dendritic cells (DCs) and the activation of DCs, a so-called adjuvant effect. We previously reported antigen delivery system using liposomes modified with pH-sensitive polymers, such as 3-methylglutarylated hyperbranched poly(glycidol) (MGlu-HPG), for the induction of antigen-specific immune responses. We reported that inclusion of cationic lipids to MGlu-HPG-modified liposomes activates DCs and enhances antitumor effects. In this study, CpG-DNA, a ligand to Toll-like receptor 9 (TLR9) expressing in endosomes of DCs, was introduced to MGlu-HPG-modified liposomes containing cationic lipids using two complexation methods (Pre-mix and Post-mix) for additional activation of antigen-specific immunity. For Pre-mix, thin membrane of lipids and polymers were dispersed by a mixture of antigen/CpG-DNA. For Post-mix, CpG-DNA was added to pre-formed liposomes. Both Pre-mix and Post-mix delivered CpG-DNA to DC endosomes, where TLR9 is expressing, more efficiently than free CpG-DNA solution did. These liposomes promoted cytokine production from DCs and the expression of co-stimulatory molecules in vitro and induced antigen-specific immune responses in vivo. Both Pre-mix and Post-mix exhibited strong antitumor effects compared with conventional pH-sensitive polymer-modified liposomes. Results show that inclusion of multiple adjuvant molecules into pH-sensitive polymer-modified liposomes and suitable CpG-DNA complexation methods are important to design potent vaccine carriers.

Impacts of Cross-Linkers on Biological Effects of Mesoporous Silica Nanoparticles

Chemically synthesized cross-linkers play decisive roles in variable cargos attached to nanoparticles (NPs). Previous studies reported that surface properties, such as the size, charge, and surface chemistry, are particularly important determinants influencing the biological fate and actions of NPs and cells. Recent studies also focused on the relationship of serum proteins with the surface properties of NPs (also called the protein corona), which is recognized as a key factor in determining the cytotoxicity and biodistribution. However, there is concern that cross-linkers conjugated onto NPs might induce undesirable biological effects. Cell responses induced by cross-linkers have not yet been precisely elucidated. Herein, using mesoporous silica nanoparticles (MSNs) the surfaces of which were separately conjugated with four popular heterobifunctional cross-linkers, i.e., N-[α-maleimidoacetoxy]succinimide ester (AMAS), m-maleimidobenzoyl-N-hydroxysuccinimide ester (MBS), succinimidyl 4-(N-maleimidomethyl)cyclohexane-1-carboxylate (SMCC), and maleimide poly(ethylene glycol) succinimidyl carboxymethyl ester (MAL-PEG-SCM), we investigated cross-linker-conjugated MSNs to determine whether they can cause cytotoxicity, or enhance reactive oxygen species (ROS) generation, nuclear factor (NF)-κB activation, and p-p38 or p21 protein expressions in RAW264.7 macrophage cells. Furthermore, we also separately conjugated two biomolecules containing TAT peptides and bovine serum albumin (BSA) as model systems to study their cell responses in detail. Finally, in vivo mice studies evaluated the biodistribution and blood assays (biochemistry and complete blood count) of PEG-derivative NPs, and results suggested that TAT peptides caused significant white blood cell (WBC)-related cell and platelet abnormalities, as well as liver and kidney dysfunction compared to BSA when conjugated onto MSNs. The results showed that attention to cross-linkers should be considered an issue in the surface modification of NPs. We anticipate that our results could be helpful in developing biosafety nanomaterials.

Integration of nanomaterials for colorimetric immunoassays with improved performance: a functional perspective

The boom of nanotechnology has yielded exciting developments in designing new kinds of colorimetric immunoassays.

AMP-Conjugated Quantum Dots: Low Immunotoxicity Both In Vitro and In Vivo

Quantum dots (QDs) are engineered nanoparticles that possess special optical and electronic properties and have shown great promise for future biomedical applications. In this work, adenosine 5'-monophosphate (AMP), a small biocompatible molecular, was conjugated to organic QDs to produce hydrophilic AMP-QDs. Using macrophage J774A.1 as the cell model, AMP-QDs exhibited both prior imaging property and low toxicity, and more importantly, triggered limited innate immune responses in macrophage, indicating low immunotoxicity in vitro. Using BALB/c mice as the animal model, AMP-QDs were found to be detained in immune organs but did not evoke robust inflammation responses or obvious histopathological abnormalities, which reveals low immunotoxicity in vivo. This work suggests that AMP is an excellent surface ligand with low immunotoxicity, and potentially used in surface modification for more extensive nanoparticles.

Clathrin to Lipid Raft-Endocytosis via Controlled Surface Chemistry and Efficient Perinuclear Targeting of Nanoparticle

Nanoparticle interacts with live cells depending on their surface chemistry, enters into cell via endocytosis, and is commonly trafficked to an endosome/lysozome that restricts subcellular targeting options. Here we show that nanoparticle surface chemistry can be tuned to alter their cell uptake mechanism and subcellular trafficking. Quantum dot based nanoprobes of 20-30 nm hydrodynamic diameters have been synthesized with tunable surface charge (between +15 mV to -25 mV) and lipophilicity to influence their cellular uptake processes and subcellular trafficking. It is observed that cationic nanoprobe electrostatically interacts with cell membrane and enters into cell via clathrin-mediated endocytosis. At lower surface charge (between +10 mV to -10 mV), the electrostatic interaction with cell membrane becomes weaker, and additional lipid raft endocytosis is initiated. If a lipophilic functional group is introduced on a weakly anionic nanoparticle surface, the uptake mechanism shifts to predominant lipid raft-mediated endocytosis. In particular, the zwitterionic-lipophilic nanoprobe has the unique advantage as it weakly interacts with anionic cell membrane, migrates toward lipid rafts for interaction through lipophilic functional group, and induces lipid raft-mediated endocytosis. While predominate or partial clathrin-mediated entry traffics most of the nanoprobes to lysozome, predominate lipid raft-mediated entry traffics them to perinuclear region, particularly to the Golgi apparatus. This finding would guide in designing appropriate nanoprobe for subcellular targeting and delivery.

A study on effects of naphthalimide derivative-capped quantum dots on the cellular internalization, proliferation, and apoptosis ability

Quantum dots (QDs) have shown great potential in monitoring and imaging cancer cells because of their unique photochemical and photophysical properties. However, it is little-known whether QDs affect the cellular internalization, proliferation and apoptosis. Here a new class of multifunctional QDs capped with ligands that possess l-Lys or l-Arg and naphthalimide (NI), linked by carboxyl groups (l-Lys-NI@QDs and l-Arg-NI@QDs, respectively), have been synthesized. We found that these QDs are of controllable sizes, in the range of 4 to 5 nm and have strong optical emission properties. The cellular uptake of NI derivative-capped QDs was monitored by flow cytometry and confocal microscopy. The results of in vitro cytotoxicity revealed that NI derivative-capped QDs, with better cell selectivity, could inhibit the growth of multiple cancer cells more potently than amonafide. They effectively inhibited the proliferation of cells due to apoptosis, which was confirmed by Hoechst 33342, annexin V-FITC and JC-1 staining and mitochondrial membrane potential (MMP) experiments. The most potent NI derivative-capped QDs, l-Arg-NI@CdSe/ZnS, were verified to efficiently induce apoptosis via a reactive oxygen species (ROS) mediating mitochondrial dysfunction, and were more effective in promoting programmed cell death in HepG2 cells in a preliminary mechanistic study.

Amphiphilic polymer-coated CdSe/ZnS quantum dots induce pro-inflammatory cytokine expression in mouse lung epithelial cells and macrophages

Quantum dots (Qdots) are semiconductor nanoparticles with size-tunable fluorescence capabilities with diverse applications. Qdots typically contain cadmium or other heavy metals, hence raising concerns of their potential toxicity, especially in occupational settings where inhalation of nanomaterials may increase the risk of lung disease. Accordingly, we assessed the effects of tri-n-octylphosphine oxide, poly(maleic anhydride-alt-1-tetradecene) (TOPO-PMAT) coated CdSe/ZnS Qdots on mouse lung epithelial cells and macrophages. Mouse tracheal epithelial cells (MTEC), grown as organotypic cultures, bone marrow-derived macrophages (BMDM), and primary alveolar macrophages (AM) were derived from C57BL/6J or A/J mice and treated with TOPO-PMAT CdSe/ZnS Qdots (10-160 nM) for up to 24 h. Cadmium analysis showed that Qdots remained in the apical compartment of MTEC cultures, whereas they were avidly internalized by AM and BMDM, which did not differ between strains. In MTEC, Qdots selectively induced expression (mRNA and protein) of neutrophil chemokines CXCL1 and CXCL2 but only low to no detectable levels of other factors assessed. In contrast, 4 h exposure to Qdots markedly increased expression of CXCL1, IL6, IL12, and other pro-inflammatory factors in BMDM. Higher inflammatory response was seen in C57BL/6J than in A/J BMDM. Similar expression responses were observed in AM, although overall levels were less robust than in BMDM. MTEC from A/J mice were more sensitive to Qdot pro-inflammatory effects while macrophages from C57BL/6J mice were more sensitive. These findings suggest that patterns of Qdot-induced pulmonary inflammation are likely to be cell-type specific and genetic background dependent.

Direct chemiluminescent enzyme immunoassay for atrial natriuretic peptide in mammalian plasma using a PEGylated antibody

Atrial natriuretic peptide (ANP) is a peptide hormone that is synthesized and secreted by cardiac tissues and plays a pivotal role in maintaining cardiovascular homeostasis. Clinically, ANP is used as a marker of cardiovascular diseases, including heart failure. Although multiple ANP assays are currently available, a more sensitive assay is required for the direct measurement of plasma ANP where there is limited plasma availability, especially in mouse experiments. In the current study, we developed a plate-based sandwich chemiluminescent enzyme immunoassay for the measurement of plasma ANP in rats and mice without the need for prior extraction. To minimize nonspecific binding, we performed a single-step PEGylation procedure targeting the immobilized antibody, which markedly improved the assay's sensitivity and linearity. The linear range was 0.1 to 250 pM, and the minimum detection limit was 0.13 pM, 5-fold lower than the lowest value of the commercially available kits. ANP was directly measured in plasma samples without detectable cross-reactivity with B- and C-type natriuretic peptides. The accuracy of the assay was confirmed by spike recovery tests and dilution tests and by comparison with a conventional radioimmunoassay. Based on the species cross-reactivity, this assay can be used to measure human ANP.

Fluorescence-encoded gold nanoparticles: library design and modulation of cellular uptake into dendritic cells

In order to harness the unique properties of nanoparticles for novel clinical applications and to modulate their uptake into specific immune cells we designed a new library of homo- and hetero-functional fluorescence-encoded gold nanoparticles (Au-NPs) using different poly(vinyl alcohol) and poly(ethylene glycol)-based polymers for particle coating and stabilization. The encoded particles were fully characterized by UV-Vis and fluorescence spectroscopy, zeta potential and dynamic light scattering. The uptake by human monocyte derived dendritic cells in vitro was studied by confocal laser scanning microscopy and quantified by fluorescence-activated cell sorting and inductively coupled plasma atomic emission spectroscopy. We show how the chemical modification of particle surfaces, for instance by attaching fluorescent dyes, can conceal fundamental particle properties and modulate cellular uptake. In order to mask the influence of fluorescent dyes on cellular uptake while still exploiting its fluorescence for detection, we have created hetero-functionalized Au-NPs, which again show typical particle dependent cellular interactions. Our study clearly prove that the thorough characterization of nanoparticles at each modification step in the engineering process is absolutely essential and that it can be necessary to make substantial adjustments of the particles in order to obtain reliable cellular uptake data, which truly reflects particle properties.

Molecular interactions of nanomaterials and organisms: defining biomarkers for toxicity and high-throughput screening using traditional and next-generation sequencing approaches

The expression of molecular pathways in an organism provides a clue as to the potential impacts of exposure to nanomaterials.