Autophagy and oxidative stress associated with gold nanoparticles

Efficient delivery of C/EBP beta gene into human mesenchymal stem cells via polyethylenimine-coated gold nanoparticles enhances adipogenic differentiation

The controlled differentiation of stem cells via the delivery of specific genes encoding appropriate differentiation factors may provide useful models for regenerative medicine and aid in developing therapies for human patients. However, the majority of non-viral vectors are not efficient enough to manipulate difficult-to-transfect adult human stem cells in vitro. Herein, we report the first use of 25 kDa branched polyethylenimine-entrapped gold nanoparticles (AuPEINPs) and covalently bound polyethylenimine-gold nanoparticles (AuMUAPEINPs) as carriers for efficient gene delivery into human mesenchymal stem cells (hMSCs). We determined a functional application of these nanoparticles by transfecting hMSCs with the C/EBP beta gene, fused to EGFP, to induce adipogenic differentiation. Transfection efficacy with AuPEINPs and AuMUAPEINPs was 52.3% and 40.7%, respectively, which was 2.48 and 1.93 times higher than that by using Lipofectamine 2000. Luciferase assay results also demonstrated improved gene transfection efficiency of AuPEINPs/AuMUAPEINPs over Lipofectamine 2000 and polyethylenimine. Overexpression of exogenous C/EBP beta significantly enhanced adipogenesis in hMSCs as indicated by both of Oil Red O staining and mRNA expression analyses. Nanoparticle/DNA complexes exhibited favorable cytocompatibility in hMSCs. Taken together, AuPEINPs and AuMUAPEINPs potentially represent safe and highly efficient vehicles for gene delivery to control hMSC differentiation and for therapeutic gene delivery applications.

The NLRP3 inflammasome in pathogenic particle and fibre-associated lung inflammation and diseases

The concept of the inflammasome, a macromolecular complex sensing cell stress or danger signals and initiating inflammation, was first introduced approximately a decade ago. Priming and activation of these intracellular protein platforms trigger the maturation of pro-inflammatory chemokines and cytokines, most notably, interleukin-1β (IL-1β) and IL-18, to promulgate innate immune defenses. Although classically studied in models of gout, Type II diabetes, Alzheimer's disease, and multiple sclerosis, the importance and mechanisms of action of inflammasome priming and activation have recently been elucidated in cells of the respiratory tract where they modulate the responses to a number of inhaled pathogenic particles and fibres. Most notably, inflammasome activation appears to regulate the balance between tissue repair and inflammation after inhalation of pathogenic pollutants such as asbestos, crystalline silica (CS), and airborne particulate matter (PM). Different types of fibres and particles may have distinct mechanisms of inflammasome interaction and outcome. This review summarizes the structure and function of inflammasomes, the interplay between various chemokines and cytokines and cell types of the lung and pleura after inflammasome activation, and the events leading to the development of non-malignant (allergic airway disease and chronic obstructive pulmonary disease (COPD), asbestosis, silicosis) and malignant (mesothelioma, lung cancer) diseases by pathogenic particulates. In addition, it emphasizes the importance of communication between cells of the immune system, target cells of these diseases, and components of the extracellular matrix (ECM) in regulation of inflammasome-mediated events.

NKCT1 (purified Naja kaouthia protein toxin) conjugated gold nanoparticles induced Akt/mTOR inactivation mediated autophagic and caspase 3 activated apoptotic cell death in leukemic cell

BACKGROUND

Gold nanoparticle (GNP) and snake venom protein toxin NKCT1 was conjugated as stated earlier (Bhowmik et al., 2013). The aim of this study was to explore the caspase dependent apoptotic pathway and autophagy inducing ability of gold nanoparticles tagged snake venom protein toxin NKCT1 (GNP-NKCT1) in human leukemic U937 and K562 cell line.

METHODS

GNP-NKCT1 induced apoptosis in U937 and K562 cell line were assessed through mitochondrial membrane potential assay, ROS generation assay, caspase 3 pathways and western blotting. GNP-NKCT1 induced autophagic pathway was detected through Akt, mTOR and PI3K expression by western blotting. Autophagic cell death also checked after addition of caspase 3 inhibitor and which also reconfirmed by western blotting of autophagic marker protein, lysosomal staining.

RESULTS

Loss of mitochondrial membrane potential was occurred in both the leukemic cell line after induction by GNP-NKCT1 and treatment of which also exhibited high ROS generation. Caspase 3 expression of cell was also increased. With caspase 3 inhibitor, GNP-NKCT1 downregulated PI3K/Akt and mTOR expression and thus undergoing autophagic cell death. Lysosomal staining confirmed lysosomal enzyme involvement in the autophagic response. Up regulation of Atg 3, Atg12, Beclin 1, LC3-II protein and BIF-1 and down regulation of Atg4B were also showed by blotting.

CONCLUSION

The results demonstrated that conjugation of Gold nanoparticles with NKCT1 could induce an alternate cell death pathway other than apoptosis in the form of autophagy in leukemic cell.

GENERAL SIGNIFICANCE

This study might provide the understanding area of chemotherapeutic drug development from natural resources like snake venoms.

Effects of surface charges of gold nanoclusters on long-term in vivo biodistribution, toxicity, and cancer radiation therapy

Gold nanoclusters (Au NCs) have exhibited great advantages in medical diagnostics and therapies due to their efficient renal clearance and high tumor uptake. The in vivo effects of the surface chemistry of Au NCs are important for the development of both nanobiological interfaces and potential clinical contrast reagents, but these properties are yet to be fully investigated. In this study, we prepared glutathione-protected Au NCs of a similar hydrodynamic size but with three different surface charges: positive, negative, and neutral. Their in vivo biodistribution, excretion, and toxicity were investigated over a 90-day period, and tumor uptake and potential application to radiation therapy were also evaluated. The results showed that the surface charge greatly influenced pharmacokinetics, particularly renal excretion and accumulation in kidney, liver, spleen, and testis. Negatively charged Au NCs displayed lower excretion and increased tumor uptake, indicating a potential for NC-based therapeutics, whereas positively charged clusters caused transient side effects on the peripheral blood system.

A comparison of immunotoxic effects of nanomedicinal products with regulatory immunotoxicity testing requirements

Nanomaterials (NMs) are attractive for biomedical and pharmaceutical applications because of their unique physicochemical and biological properties. A major application area of NMs is drug delivery. Many nanomedicinal products (NMPs) currently on the market or in clinical trials are most often based on liposomal products or polymer conjugates. NMPs can be designed to target specific tissues, eg, tumors. In virtually all cases, NMPs will eventually reach the immune system. It has been shown that most NMs end up in organs of the mononuclear phagocytic system, notably liver and spleen. Adverse immune effects, including allergy, hypersensitivity, and immunosuppression, have been reported after NMP administration. Interactions of NMPs with the immune system may therefore constitute important side effects. Currently, no regulatory documents are specifically dedicated to evaluate the immunotoxicity of NMs or NMPs. Their immunotoxicity assessment is performed based on existing guidelines for conventional substances or medicinal products. Due to the unique properties of NMPs when compared with conventional medicinal products, it is uncertain whether the currently prescribed set of tests provides sufficient information for an adequate evaluation of potential immunotoxicity of NMPs. The aim of this study was therefore, to compare the current regulatory immunotoxicity testing requirements with the accumulating knowledge on immunotoxic effects of NMPs in order to identify potential gaps in the safety assessment. This comparison showed that immunotoxic effects, such as complement activation-related pseudoallergy, myelosuppression, inflammasome activation, and hypersensitivity, are not readily detected by using current testing guidelines. Immunotoxicity of NMPs would be more accurately evaluated by an expanded testing strategy that is equipped to stratify applicable testing for the various types of NMPs.

The bright side of plasmonic gold nanoparticles; activation of Nrf2, the cellular protective pathway

Plasmonic gold nanoparticles (AuNPs) are widely investigated for cancer therapy, due to their ability to strongly absorb light and convert it to heat and thus selectively destroy tumor cells. In this study we shed light on a new aspect of AuNPs and their plasmonic excitation, wherein they can provide anti-oxidant and anti-inflammatory protection by stimulating the cellular protective Nrf2 pathway. Our study was carried out on cells of the immune system, macrophages, and on skin cells, keratinocytes. A different response to AuNPs was noted in the two types of cells, explained by their distinct uptake profiles. In keratinocytes, the exposure to AuNPs, even at low concentrations, was sufficient to activate the Nrf2 pathway, without any irradiation, due to the presence of free AuNPs inside the cytosol. In contrast, in macrophages, the plasmonic excitation of the AuNPs by a low, non-lethal irradiation dose was required for their release from the constraining vesicles. The mechanism by which AuNPs activate the Nrf2 pathway was studied. Direct and indirect activation were suggested, based on the inherent ability of the AuNPs to react with thiol groups and to generate reactive oxygen species, in particular, under plasmonic excitation. The ability of AuNPs to directly activate the Nrf2 pathway renders them good candidates for treatment of disorders in which the up-regulation of Nrf2 is beneficial, specifically for topical treatment of inflammatory skin diseases.

pH-Sensitive Polymeric Nanoparticles Modulate Autophagic Effect via Lysosome Impairment

In drug delivery systems, pH-sensitive polymers are commonly used as drug carriers, and significant efforts have been devoted to the aspects of controlled delivery and release of drugs. However, few studies address the possible autophagic effects on cells. Here, for the first time, using a fluorescent autophagy-reporting cell line, this study evaluates the autophagy-induced capabilities of four types of pH-sensitive polymeric nanoparticles (NPs) with different physical properties, including size, surface modification, and pH-sensitivity. Based on experimental results, this study concludes that pH-sensitivity is one of the most important factors in autophagy induction. In addition, this study finds that variation of concentration of NPs could cause different autophagic effect, i.e., low concentration of NPs induces autophagy in an mTOR-dependent manner, but high dose of NPs leads to autophagic cell death. Identification of this tunable autophagic effect offers a novel strategy for enhancing therapeutic effect in cancer therapy through modulation of autophagy.

Nanomaterial-modulated autophagy: underlying mechanisms and functional consequences

Autophagy is an essential lysosome-dependent process that controls the quality of the cytoplasm and maintains cellular homeostasis, and dysfunction of this protein degradation system is correlated with various disorders. A growing body of evidence suggests that nanomaterials (NMs) have autophagy-modulating effects, thus predicting a valuable and promising application potential of NMs in the diagnosis and treatment of autophagy-related diseases. NMs exhibit unique physical, chemical and biofunctional properties, which may endow NMs with capabilities to modulate autophagy via various mechanisms. The present review highlights the impacts of various NMs on autophagy and their functional consequences. The possible underlying mechanisms for NM-modulated autophagy are also discussed.

Nanoparticles in radiation oncology: From bench-side to bedside

Nanoparticles (NP) are "in vogue" in medical research. Pre-clinical studies accumulate evidence of NP enhancing radiation therapy. On one hand, NP, selected for their intrinsic physicochemical characteristics, are radio-sensitizers. Thus, when NP accumulate in cancer cells, they increase the radiation absorption coefficient specifically in tumour tissue, sparing healthy surrounding tissue from toxicity. On the other hand, NP, by being drug vectors, can carry radio-sensitizer therapeutics to cancer cells. Finally, NP present theranostic effects. Indeed they are used in imaging as contrast agents. NP therefore can be multi-tasking and have promising prospect in radiotherapy field. In spite of the numerous encouraging preclinical evidence, the very small number of clinical trials investigating NP possible involvement in the radiotherapy clinical practice suggests a physicians' unwillingness. Many prerequisites seem necessary including define biological mechanisms of NP radiosensitization pathways and of NP clearance. NP biocompatibility and toxicities should be better investigated to select, among the extensive range of possible systems, the harmless and most efficient one, and to finally come to a safe and successful clinical use. The present review focuses on the various interests of NP in the radiotherapy area and proposes a discussion about their role in the future clinical practice.

Surface capping and size-dependent toxicity of gold nanoparticles on different trophic levels

In the present study, the toxicity of gold nanoparticles (Au NPs) was evaluated on various trophic organisms. Bacteria, algae, cell line, and mice were used as models representing different trophic levels. Two different sizes (CIT30 and CIT40) and surface-capped (CIT30-polyvinyl pyrrolidone (PVP)-capped) Au NPs were selected. CIT30 Au NP aggregated more rapidly than CIT40 Au NP, while an additional capping of PVP (CIT30-PVP capped Au NP) was found to enhance its stability in sterile lake water medium. Interestingly, all the forms of NPs evaluated were stable in the cell culture medium during the exposure period. Size- and dose-dependent cytotoxicities were observed in both bacteria and algae, with a strong dependence on reactive oxygen species (ROS) generation and lactate dehydrogenase (LDH) release. CIT30-PVP capped Au NP showed a significant decrease in toxicity compared to CIT30 Au NP in bacteria and algae. In the SiHa cell line, dose- and exposure-dependent decline in cell viability were noted for all three types of Au NPs. In mice, the induction of DNA damage was size and dose dependent, and surface functionalization with PVP reduced the toxic effects of CIT30 Au NP. The exposure to CIT30, CIT40, and CIT30-PVP capped Au NPs caused an alteration of the oxidative stress-related endpoints in mice hepatocytes. The toxic effects of the gold nanoparticles were found to vary in diverse test systems, accentuating the importance of size and surface functionalization at different trophic levels.

Silver nanoparticles synthesized from Adenium obesum leaf extract induced DNA damage, apoptosis and autophagy via generation of reactive oxygen species

Silver nanoparticles (AgNPs) are an important class of nanomaterial used for a wide range of industrial and biomedical applications. Adenium obesum is a plant of the family Apocynaceae that is rich in toxic cardiac glycosides; however, there is scarce information on the anticancer potential of its AgNPs. We herein report the novel biosynthesis of AgNPs using aqueous leaf extract of A. obesum (AOAgNPs). The synthesis of AOAgNPs was monitored by color change and ultraviolet-visible spectroscopy (425 nm). It was further characterized by Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD) and transmission electron microscopy (TEM). The FTIR spectra for the AOAgNPs indicated the presence of terpenoids, long chain fatty acids, secondary amide derivatives and proteins that could be responsible for the reduction and capping of the formed AOAgNPs. X-ray diffraction confirmed the crystallinity of the AgNPs. The TEM images revealed mostly spherical particles in the size range of 10-30 nm. The biological properties of novel AOAgNPs were investigated on MCF-7 breast cancer cells. Cell viability was determined by the MTT assay. Generation of reactive oxygen species (ROS), DNA damage, induction of apoptosis and autophagy were assessed. A dose-dependent decrease in the cell viability was observed. The IC50 value was calculated as 217 μg/ml. Both qualitative and quantitative evaluation confirmed about a 2.5 fold increase in the generation of ROS at the highest concentration of 150 μg/ml. A significant (p<0.05) increase in the DNA damage evaluated by comet assay was evident. Flow cytometry revealed an increase in the apoptotic cells (24%) in the AOAgNPs treated group compared to the control. Acridine orange staining of acidic vesicles in exposed cells confirmed the induction of autophagy. These findings suggest that AOAgNPs increased the level of ROS resulting in heightened the DNA damage, apoptosis and autophagy in MCF-7 cells.

Ru(II)-polypyridyl surface functionalised gold nanoparticles as DNA targeting supramolecular structures and luminescent cellular imaging agents

The development of Ru(II) functionalized gold nanoparticles 1–3·AuNP is described. These systems were found to be mono-disperse with a hydrodynamic radius of ca. 15 nm in water but gave rise to the formation of higher order structures in buffered solution. The interaction of 1–3·AuNP with DNA was also studied by spectroscopic and microscopic methods and suggested the formation of large self-assembly structures in solution. The uptake of 1–3·AuNP by cancer cells was studied using both confocal fluorescence as well as transmission electron microscopy (TEM), with the aim of investigating their potential as tools for cellular biology. These systems displaying a non-toxic profile with favourable photophysical properties may have application across various biological fields including diagnostics and therapeutics.

Unraveling the neurotoxicity of titanium dioxide nanoparticles: focusing on molecular mechanisms

Titanium dioxide nanoparticles (TiO2 NPs) possess unique characteristics and are widely used in many fields. Numerous in vivo studies, exposing experimental animals to these NPs through systematic administration, have suggested that TiO2 NPs can accumulate in the brain and induce brain dysfunction. Nevertheless, the exact mechanisms underlying the neurotoxicity of TiO2 NPs remain unclear. However, we have concluded from previous studies that these mechanisms mainly consist of oxidative stress (OS), apoptosis, inflammatory response, genotoxicity, and direct impairment of cell components. Meanwhile, other factors such as disturbed distributions of trace elements, disrupted signaling pathways, dysregulated neurotransmitters and synaptic plasticity have also been shown to contribute to neurotoxicity of TiO2 NPs. Recently, studies on autophagy and DNA methylation have shed some light on possible mechanisms of nanotoxicity. Therefore, we offer a new perspective that autophagy and DNA methylation could contribute to neurotoxicity of TiO2 NPs. Undoubtedly, more studies are needed to test this idea in the future. In short, to fully understand the health threats posed by TiO2 NPs and to improve the bio-safety of TiO2 NPs-based products, the neurotoxicity of TiO2 NPs must be investigated comprehensively through studying every possible molecular mechanism.

Visualization and analysis of nanoparticle transport and ageing in reactive porous media

We present quasi-3D visualization and analysis of engineered nanoparticle (ENP) transport behavior in an experimental setup that uses a transmitted light imaging technique. A flow cell was packed with specially adapted, water-transparent, spherical polyacrylamide beads, which carry a negative surface charge representative of many natural environments. Ubiquitous, oppositely-charged ENPs - Au and Ag NPs - were synthesized and introduced into a flow cell subjected to a macroscopically uniform flow field via point source pulse injection, at three different flow rates. The negatively-charged ENPs behaved like a conservative tracer, in terms of spatio-temporal plume evolution. The positive AgNPs, however, displayed a decrease in their initially strong tendency to attach to the oppositely-charged porous medium. As a result, immobilization of the positive AgNPs was spatially and temporally limited to the vicinity of the point of injection; beyond this region, the AgNPs were mobile and effluent contained AgNPs with hydrodynamic diameters significantly larger than those of the injected AgNPs. This behavior is understood by dynamic light scattering and ζ potential measurements, which showed aggregation processes and inversion in particle surface charge to occur during transport of the positive ENPs. These findings have broad implications for ENP mobility and reactivity in the environment.

Nanomedicine and nanotoxicology: the pros and cons for neurodegeneration and brain cancer

Current strategies for brain diseases are mostly symptomatic and noncurative. Nanotechnology has the potential to facilitate the transport of drugs across the blood-brain barrier and to enhance their pharmacokinetic profile. However, to reach clinical application, an understanding of nanoneurotoxicity in terms of oxidative stress and inflammation is required. Emerging evidence has also shown that nanoparticles have the ability to alter autophagy, which can induce inflammation and oxidative stress, or vice versa. These effects may increase neurodegenerative processes damage, but on the other hand, they may have benefits for brain cancer therapies. In this review, we emphasize how nanomaterials may induce neurotoxic effects focusing on neurodegeneration, and how these effects could be exploited toward brain cancer treatment.

Nanoparticle pollution and associated increasing potential risks on environment and human health: a case study of China

The aims of this study are (1) to discuss the mechanism of nanoparticle lifecycle and estimate the impacts of its associated pollution on environment and human health; and (2) to provide recommendation to policy makers on how to leverage nanopollution and human health along with the rapid development of economics in China. Manufactured nanoparticles (MNPs) could either directly or indirectly impair human health and the environment. Exposures to MNP include many ways, such as via inhalation, ingestion, direct contact, or the use of consumer products over the lifecycle of the product. In China, the number of people exposed to MNP has been increasing year by year. To better provide medical care to people exposed to MNP, the Chinese government has established many disease control and prevention centers over China. However, the existing facilities and resources for controlling MNP are still not enough considering the number of people impacted by MNP and the number of ordinary workers in the MNP related industry applying for their occupational identification through the Center for Disease Control and Prevention. China should assess the apparent risk environment and human health being exposed to MNP and develop action plans to reduce the possibility of direct contacts between human beings and the emerging nanomaterials. In addition, we suggest more comprehensive studies on the MNP behavior and the development of quantitative approaches to measure MNP transport, and persistence should be carried out.

The autophagic response to polystyrene nanoparticles is mediated by transcription factor EB and depends on surface charge

BACKGROUND

A number of engineered nanoparticles induce autophagy, the main catabolic pathway that regulates bulk degradation of cytoplasmic material by the lysosomes. Depending on the specific physico-chemical properties of the nanomaterial, however, nanoparticle-induced autophagy may have different effects on cell physiology, ranging from enhanced autophagic degradation to blockage of autophagic flux. To investigate the molecular mechanisms underlying the impact of nanoparticle charge on the nature of the autophagic response, we tested polystyrene nanoparticles (50 nm) with neutral, anionic, and cationic surface charges.

RESULTS

We found all polystyrene nanoparticles investigated in this study to activate autophagy. We showed that internalization of polystyrene nanoparticles results in activation of the transcription factor EB, a master regulator of autophagy and lysosome biogenesis. Autophagic clearance, however, was observed to depend specifically on the charge of the nanoparticles. Particularly, we found that the autophagic response to polystyrene nanoparticles presenting a neutral or anionic surface involves enhanced clearance of autophagic cargo. Cell exposure to polystyrene nanoparticles presenting a cationic surface, on the other hand, results in transcriptional upregulation of the pathway, but also causes lysosomal dysfunction, ultimately resulting in blockage of autophagic flux.

CONCLUSIONS

This study furthers our understanding of the molecular mechanisms that regulate the autophagic response to nanoparticles, thus contributing essential design criteria for engineering benign nanomaterials.

Cytotoxicity of various types of gold-mesoporous silica nanoparticles in human breast cancer cells

Recently, gold nanoparticles (AuNPs) have shown promising biological applications due to their unique electronic and optical properties. However, the potential toxicity of AuNPs remains a major hurdle that impedes their use in clinical settings. Mesoporous silica is very suitable for the use as a coating material for AuNPs and might not only reduce the cytotoxicity of cetyltrimethylammonium bromide-coated AuNPs but might also facilitate the loading and delivery of drugs. Herein, three types of rod-like gold-mesoporous silica nanoparticles (termed bare AuNPs, core-shell Au@mSiO2NPs, and Janus Au@mSiO2NPs) were specially designed, and the effects of these AuNPs on cellular uptake, toxic behavior, and mechanism were then systematically studied. Our results indicate that bare AuNPs exerted higher toxicity than the Au@mSiO2NPs and that Janus Au@mSiO2NPs exhibited the lowest toxicity in human breast cancer MCF-7 cells, consistent with the endocytosis capacity of the nanoparticles, which followed the order, bare AuNPs > core-shell Au@mSiO2NPs > Janus Au@mSiO2NPs. More importantly, the AuNPs-induced apoptosis of MCF-7 cells exhibited features that were characteristic of intracellular reactive oxygen species (ROS) generation, activation of c-Jun-N-terminal kinase (JNK) phosphorylation, an enhanced Bax-to-Bcl-2 ratio, and loss of the mitochondrial membrane potential. Simultaneously, cytochrome c was released from mitochondria, and the caspase-3/9 cascade was activated. Moreover, both ROS scavenger (N-acetylcysteine) and JNK inhibitor (SP600125) partly blocked the induction of apoptosis in all AuNPs-treated cells. Taken together, these findings suggest that all AuNPs induce apoptosis through the ROS-/JNK-mediated mitochondrial pathway. Thus, Janus Au@mSiO2NPs exhibit the potential for applications in biomedicine, thus aiding the clinical translation of AuNPs.

Oxidative stress by inorganic nanoparticles

Metallic and metallic oxide nanoparticles (NPs) have been increasingly used for various bio-applications owing to their unique physiochemical properties in terms of conductivity, optical sensitivity, and reactivity. With the extensive usage of NPs, increased human exposure may cause oxidative stress and lead to undesirable health consequences. To date, various endogenous and exogenous sources of oxidants contributing to oxidative stress have been widely reported. Oxidative stress is generally defined as an imbalance between the production of oxidants and the activity of antioxidants, but it is often misrepresented as a single type of cellular stress. At the biological level, NPs can initiate oxidative stress directly or indirectly through various mechanisms, leading to profound effects ranging from the molecular to the disease level. Such effects of oxidative stress have been implicated owing to their small size and high biopersistence. On the other hand, cellular antioxidants help to counteract oxidative stress and protect the cells from further damage. While oxidative stress is commonly known to exert negative biological effects, measured and intentional use of NPs to induce oxidative stress may provide desirable effects to either stimulate cell growth or promote cell death. Hence, NP-induced oxidative stress can be viewed from a wide paradigm. Because oxidative stress is comprised of a wide array of factors, it is also important to use appropriate assays and methods to detect different pro-oxidant and antioxidant species at molecular and disease levels. WIREs Nanomed Nanobiotechnol 2016, 8:414-438. doi: 10.1002/wnan.1374 For further resources related to this article, please visit the WIREs website.

Reactive oxygen species-activated nanomaterials as theranostic agents

Reactive oxygen species (ROS) are generated from the endogenous oxidative metabolism or from exogenous pro-oxidant exposure. Oxidative stress occurs when there is excessive production of ROS, outweighing the antioxidant defense mechanisms which may lead to disease states. Hydrogen peroxide (H2O2) is one of the most abundant and stable forms of ROS, implicated in inflammation, cellular dysfunction and apoptosis, which ultimately lead to tissue and organ damage. This review is an overview of the role of ROS in different diseases. We will also examine ROS-activated nanomaterials with emphasis on hydrogen peroxide, and their potential medical implications. Further development of the biocompatible, stimuli-activated agent responding to disease causing oxidative stress, may lead to a promising clinical use.

A real-time documentation and mechanistic investigation of quantum dots-induced autophagy in live Caenorhabditis elegans

Autophagy is a highly important intracellular process for the degradation of endogenous or foreign contents in the cytoplasm. Though nanomaterials-induced autophagy has been extensively studied, real-time information about the autophagic process induced by nanomaterials in live organisms remains unknown. Here by using Caenorhabditis elegans as the model organism and fluorescent semiconductor quantum dots (QDs) as a representative nanomaterial, we systematically investigated the phenomenon of QDs-induced autophagy in live organisms. Our results demonstrated that the internalized QDs trigger a complete autophagic process in C. elegans intestinal cells. Further investigations revealed that this QD-induced autophagy in C. elegans is neither a response to released heavy metal ions by the QDs, nor an attempt to engulf exogenous QD materials, but a defensive strategy of the organism to clear and recycle damaged endosomes. Of particular significance, for the first time, we presented real-time tracking of autophagosomes formation in live organisms, providing detailed temporal-spatial information of this process. This study may help us better understand the relationship between nanomaterials and autophagy in vivo, and provide invaluable information for safety evaluation and bio-application of nanomaterials.

Plasmonic Tipless Pyramid Arrays for Cell Poration

Improving the efficiency, cell survival, and throughput of methods to modify and control the genetic expression of cells is of great benefit to biology and medicine. We investigate, both computationally and experimentally, a nanostructured substrate made of tipless pyramids for plasmonic-induced transfection. By optimizing the geometrical parameters for an excitation wavelength of 800 nm, we demonstrate a 100-fold intensity enhancement of the electric near field at the cell-substrate contact area, while the low absorption typical for gold is maintained. We demonstrate that such a substrate can induce transient poration of cells by a purely optically induced process.

Silicon-based quantum dots induce inflammation in human lung cells and disrupt extracellular matrix homeostasis

Quantum dots (QDs) are nanocrystalline semiconductor materials that have been tested for biological applications such as cancer therapy, cellular imaging and drug delivery, despite the serious lack of information of their effects on mammalian cells. The present study aimed to evaluate the potential of Si/SiO2 QDs to induce an inflammatory response in MRC-5 human lung fibroblasts. Cells were exposed to different concentrations of Si/SiO2 QDs (25-200 μg·mL(-1)) for 24, 48, 72 and 96 h. The results obtained showed that uptake of QDs was dependent on biocorona formation and the stability of nanoparticles in various biological media (minimum essential medium without or with 10% fetal bovine serum). The cell membrane damage indicated by the increase in lactate dehydrogenase release after exposure to QDs was dose- and time-dependent. The level of lysosomes increased proportionally with the concentration of QDs, whereas an accumulation of autophagosomes was also observed. Cellular morphology was affected, as shown by the disruption of actin filaments. The enhanced release of nitric oxide and the increase in interleukin-6 and interleukin-8 protein expression suggested that nanoparticles triggered an inflammatory response in MRC-5 cells. QDs decreased the protein expression and enzymatic activity of matrix metalloproteinase (MMP)-2 and MMP-9 and also MMP-1 caseinase activity, whereas the protein levels of MMP-1 and tissue inhibitor of metalloproteinase-1 increased. The present study reveals for the first time that silicon-based QDs are able to generate inflammation in lung cells and cause an imbalance in extracellular matrix turnover through a differential regulation of MMPs and tissue inhibitor of metalloproteinase-1 protein expression.

Magnetite nanoparticles induced adaptive mechanisms counteract cell death in human pulmonary fibroblasts

Magnetite nanoparticles (MNP) have attracted great interest for biomedical applications due to their unique chemical and physical properties, but the MNP impact on human health is not fully known. Consequently, our study proposes to highlight the biochemical mechanisms that underline the toxic effects of MNP on a human lung fibroblast cell line (MRC-5). The cytotoxicity generated by MNP in MRC-5 cells was dose and time-dependent. MNP-treated MRC-5 cells accumulated large amount of iron and reactive oxygen species (ROS) and exhibited elevated antioxidant scavenger enzymes. Reduced glutathione (GSH) depletion and enhanced lipid peroxidation (LPO) processes were also observed. The cellular capacity to counteract the oxidative damage was sustained by high levels of heat shock protein 60 (Hsp60), a protein that confers resistance against ROS attack and inhibition of cell death. While significant augmentations in nitric oxide (NO) and prostaglandine E2 (PGE2) levels were detected after 72 h of MNP-exposure only, caspase-1 was activated earlier starting with 24h post-treatment. Taken together, our results suggest that MRC-5 cells have the capacity to develop cell protection mechanisms against MNP. Detailed knowledge of the mechanisms induced by MNP in cell culture could be essential for their prospective use in various in vivo biochemical applications.

Epigenetic mechanisms in nanomaterial-induced toxicity

With the growing advent of nanotechnology in medicine (therapeutic, diagnostic and imaging applications), cosmetics, electronics, clothing and food industries, exposure to nanomaterials (NMs) is on the rise and therefore exploring their toxic biological effects have gained great significance. In vitro and in vivo studies over the last decade have revealed that NMs have the potential to cause cytotoxicity and genotoxicity although some contradictory reports exist. However, there are only few studies which have explored the epigenetic mechanisms (changes to DNA methylation, histone modification and miRNA expression) of NM-induced toxicity, and there is a scarcity of information and many questions in this area remain unexplored and unaddressed. This review comprehensively describes the epigenetic mechanisms involved in the induction of toxicity of engineered NMs, and provides comparisons between similar effects observed upon exposure to small or nanometer-sized particles. Lastly, gaps in existing literature and scope for future studies that improve our understanding of NM-induced epigenetic toxicity are discussed.

Interaction of gold nanoparticles with proteins and cells

Gold nanoparticles (Au NPs) possess many advantages such as facile synthesis, controllable size and shape, good biocompatibility, and unique optical properties. Au NPs have been widely used in biomedical fields, such as hyperthermia, biocatalysis, imaging, and drug delivery. The broad application range may result in hazards to the environment and human health. Therefore, it is important to predict safety and evaluate therapeutic efficiency of Au NPs. It is necessary to establish proper approaches for the study of toxicity and biomedical effects. In this review, we first focus on the recent progress in biological effects of Au NPs at the molecular and cellular levels, and then introduce key techniques to study the interaction between Au NPs and proteins. Knowledge of the biomedical effects of Au NPs is significant for the rational design of functional nanomaterials and will help predict their safety and potential applications.

Inorganic nanovectors for nucleic acid delivery

Nucleic acids show immense potential to treat cancer, acquired immune deficiency syndrome, neurological diseases and other incurable human diseases. Upon systemic administration, they encounter a series of barriers and hence barely reach the site of action, the cell. Intracellular delivery of nucleic acids is facilitated by nanovectors, both viral and non-viral. A major advantage of non-viral vectors over viral vectors is safety. Nanovectors evaluated specifically for nucleic acid delivery include polyplexes, lipoplexes and other cationic carrier-based vectors. However, more recently there is an increased interest in inorganic nanovectors for nucleic acid delivery. Nevertheless, there is no comprehensive review on the subject. The present review would cover in detail specific properties and types of inorganic nanovectors, their preparation techniques and various biomedical applications as therapeutics, diagnostics and theranostics. Future prospects are also suggested.

Effects of atrazine and chlorpyrifos on oxidative stress-induced autophagy in the immune organs of common carp (Cyprinus carpio L.)

Atrazine (ATR) and chlorpyrifos (CPF) are the most common agrochemical in the freshwater ecosystems of the world. This study assessed the effects of ATR (4.28, 42.8 and 428 μg/L), CPF (1.16, 11.6 and 116 μg/L) and combined ATR/CPF (1.13, 11.3 and 113 μg/L) on common carp head kidneys and spleens following 40 d exposure and 40 d recovery treatments. Nitric oxide (NO) content, activities of anti hydroxyl radical (AHR), anti superoxide anion (ASA), peroxidase (POD) and inducible nitric oxide synthase (iNOS), and the mRNA levels of the autophagy genes (LC3-II, dynein, TOR) were determined. The results indicate that the antioxidant enzyme (AHR, ASA, POD and iNOS) activities and NO content in the head kidney and spleen of the common carp increased significantly after a 40 d exposure to ATR and CPF alone or in combination. The mRNA levels of LC3-II and dynein in common carp increased significantly after exposure to ATR and CPF alone, or in combination. Moreover, the mRNA levels of LC3-II and dynein decreased significantly after a 40-d recovery. However, the mRNA levels of TOR gene for all decreased significantly at the end of the exposure and the recovery. To our knowledge, this is the first study to report the oxidative stress-induced autophagic effects in the common carp by exposure to ATR, CPF and the ATR/CPF combination. The information presented in the present study may be helpful to understanding the mechanisms of autophagy induced by ATR, CPF and the ATR/CPF combination in fish.

Self-assembled autophagy-inducing polymeric nanoparticles for breast cancer interference in-vivo

A peptide-conjugated poly(β-amino ester) that self-assembles into micelle-like nanoparticles is prepared by a convenient and modular supramolecular approach. The polymer-beclin-1 (P-Bec1) nanoparticles display enhanced cytotoxicity to breast cancer cells through induction of autophagy. This approach overcomes two major limitations of the haploinsufficient tumor suppressor Bec1 compared to small-molecule drugs: poor delivery to tumors owing to enzymatic degradation, and unstable, non-specific bio-distribution and targeting in the tumor tissues.

Biosynthesis of gold nanoparticles and related cytotoxicity evaluation using A549 cells

Biosynthesis of gold nanoparticles (AuNPs) has become an attractive area of research as it is environmentally benign. The toxicity of AuNPs synthesized by chemical routes has been widely studied. However, little is known about the toxicity associated with the biological synthesis of AuNPs. The present study was carried out to synthesize AuNPs using star anise (Illicium verum; a commercially available spice in abundance)and evaluate its toxicity using human epithelial lung cells (A549) in comparison with AuNPs synthesized by the traditional chemical methods (using sodium citrate and sodium borohydride). Apart from cell viability, markers of oxidative stress (reduced glutathione) and cell death (caspases) were also evaluated to understand the mechanisms of toxicity. Cell viability was observed to be 65.7 percent and 72.3 percent in cells exposed to chemically synthesized AuNPs at the highest dose (200nM) as compared to 80.2 percent for biologically synthesized AuNPs. Protective coating/capping of AuNPs by various polyphenolic compounds present in star anise extract appears to be a major contributor to lower toxicity observed in biologically synthesized AuNPs.

Superparamagnetic core/shell GoldMag nanoparticles: size-, concentration- and time-dependent cellular nanotoxicity on human umbilical vein endothelial cells and the suitable conditions for magnetic resonance imaging

Background

GoldMag nanoparticles (GMNPs) possess the properties of colloid gold and superparamagnetic iron oxide nanoparticles, which make them useful for delivery, separation and molecular imaging. However, because of the nanometer effect, GMNPs are highly toxic. Thus, the biosafety of GMNPs should be fully studied prior to their use in biomedicine. The main purpose of this study was to evaluate the nanotoxicity of GMNPs on human umbilical vein endothelial cells (HUVECs) and determine a suitable size, concentration and time for magnetic resonance imaging (MRI).

Results

Transmission electron microscopy showed that GMNPs had a typical shell/core structure, and the shell was confirmed to be gold using energy dispersive spectrometer analysis. The average sizes of the 30 and 50 nm GMNPs were 30.65 ± 3.15 and 49.23 ± 5.01 nm, respectively, and the shell thickness were 6.8 ± 0.65 and 8.5 ± 1.36 nm, respectively. Dynamic light scattering showed that the hydrodynamic diameter of the 30 and 50 nm GMNPs were 33.2 ± 2.68 and 53.12 ± 4.56 nm, respectively. The r₂ relaxivity of the 50 nm GMNPs was 98.65 mM⁻¹ s⁻¹, whereas it was 80.18 mM⁻¹ s⁻¹ for the 30 nm GMNPs. The proliferation, cytoskeleton, migration, tube formation, apoptosis and ROS generation of labeled HUVECs depended on the size and concentration of GMNPs and the time of exposure. Because of the higher labeling rate, the 50 nm GMNPs exhibited a significant increase in nanotoxicity compared with the 30 nm GMNPs at the same concentration and time. At no more than 25 μg/mL and 12 hours, the 50 nm GMNPs exhibited no significant nanotoxicity in HUVECs, whereas no toxicity was observed at 50 μg/mL and 24 hours for the 30 nm GMNPs.

Conclusions

These results demonstrated that the nanotoxicity of GMNPs in HUVECs depended on size, concentration and time. Exposure to larger GMNPs with a higher concentration for a longer period of time resulted in a higher labeling rate and ROS level for HUVECs. Coupled with r₂ relaxivity, it was suggested that the 50 nm GMNPs are more suitable for HUVEC labeling and MRI, and the suitable concentration and time were 25 μg/mL and 12 hours.

Gold nanoparticles do not induce myotube cytotoxicity but increase the susceptibility to cell death

Gold nanoparticles (AuNP) have been widely used for many applications, including as biological carriers. A better understanding concerning AuNP safety on muscle cells is crucial, since it could be a potential tool in the nanomedicine field. Here, we describe the impact of polyethylene glycol-coated gold nanoparticles (PEG-AuNP) interaction with differentiated skeletal muscle C2C12 cells on cell viability, mitochondria function, cell signaling related to survival, cytokine levels and susceptibility to apoptosis. Intracellular localization of 4.5 nm PEG-AuNP diameter size was evidenced by STEM-in-SEM in myotube cells. Methods for cytotoxicity analysis showed that PEG-AuNP did not affect cell viability, but intracellular ATP levels and mitochondrial membrane potential increased. Phosphorylation of ERK was not altered but p-AKT levels reduced (p<0.01). Pre-treatment of cells with PEG-AuNP followed by staurosporine induction increased the caspases-3/7 activity. Indeed, cytokines analysis revealed a sharp increase of IFN-γ and TGF-β1 levels after PEG-AuNP treatment, suggesting that inflammatory and fibrotic phenotypes process were activated. These data demonstrate that PEG-AuNP affect the myotube physiology leading these cells to be more susceptible to death stimuli in the presence of staurosporine. Altogether, these results present evidence that PEG-AuNP affect the susceptibility to apoptosis of muscle cells, contributing to development of safer strategies for intramuscular delivery.

Metallic oxide nanoparticle translocation across the human bronchial epithelial barrier

Inhalation is the most frequent route of unintentional exposure to nanoparticles (NPs). Our aim was to quantify the translocation of different metallic NPs across human bronchial epithelial cells and to determine the factors influencing this translocation. Calu-3 cells forming a tight epithelial barrier when grown on a porous membrane in a two compartment chamber were exposed to fluorescently labelled NPs to quantify the NP translocation. NP translocation and uptake by cells were also studied by confocal and transmission electron microscopy. Translocation was characterized according to NP size (16, 50, or 100 nm), surface charge (negative or positive SiO2), composition (SiO2 or TiO2), presence of proteins or phospholipids and in an inflammatory context. Our results showed that NPs can translocate through the Calu-3 monolayer whatever their composition (SiO2 or TiO2), but this translocation was increased for the smallest and negatively charged NPs. Translocation was not associated with an alteration of the integrity of the epithelial monolayer, suggesting a transcytosis of the internalized NPs. By modifying the NP corona, the ability of NPs to cross the epithelial barrier differed depending on their intrinsic properties, making positively charged NPs more prone to translocate. NP translocation can be amplified by using agents known to open tight junctions and to allow paracellular passage. NP translocation was also modulated when mimicking an inflammatory context frequently found in the lungs, altering the epithelial integrity and inducing transient tight junction opening. This in vitro evaluation of NP translocation could be extended to other inhaled NPs to predict their biodistribution.

Anchoring Effects of Surface Chemistry on Gold Nanorods: Modulates Autophagy

Gold nanorods (Au NRs) have been receiving extensive attention owing to their extremely attractive properties which make them suitable for various biomedical applications. Au NRs could induce nano-toxicity, but this trouble could turn into therapeutic potential through tuning the autophagy. However, the autophagy-inducing activity and mechanism of Au NRs is still unclear. Here we showed that surface chemical modification can tune the autophagy-inducing activity of Au NRs in human lung adenocarcinoma A549 cells. CTAB-coated Au NRs induce remarkable levels of autophagy activity as evidenced by LC3-II conversion and p62 degradation, while PSS- and PDDAC-coated Au NRs barely induce autophagy. More importantly, we also demonstrated that the AKT-mTOR signaling pathway was responsible for CTAB-coated Au NRs-induced autophagy. We furthermore showed that CTAB-coated Au NRs also induces autophagy in human fetal lung fibroblast MRC-5 cells in a time-dependent manner. This study unveils a previously unknown function for Au NRs in autophagy induction, and provides a new insight for designing surface modifications of Au NRs for biomedical applications.

Modulating polyplex-mediated gene transfection by small-molecule regulators of autophagy

Nonviral gene transfection mediated by cationic polymer/DNA polyplexes often imposes stress and toxicity to cells. To better understand the relationship between cellular stress responses and polyplex-mediated transfection, polyplex-induced early autophagy in mouse fibroblasts was characterized and the impact of autophagy modulation on transgene expression evaluated. Transmission electron microscopy revealed the formation of double-membraned autophagosome in the cytoplasm of polyplex-transfected cells. Immunofluorescence staining and microscopy revealed intracellular LC3 punctation that was characteristic of early autophagy activation. Elevated expression of autophagosome-associated LC3 II protein was also detected by Western blot. When cells were treated with small-molecule modulators of autophagy, polyplex-mediated gene transfection efficiency was significantly affected. 3-Methyladenine (3-MA), an early autophagy inhibitor, reduced transfection efficiency, whereas rapamycin, an autophagy inducer, enhanced transgene expression. Importantly, the observed functional impact on gene transfection by autophagy modulation was decoupled from that of other modes of cellular stress response (apoptosis/necrosis). Treatment of cells by 3-MA or rapamycin did not affect the level of intracellular reactive oxygen species (ROS) but did decrease or increase, respectively, nuclear localization of polyplex-delivered plasmid DNA. These findings suggest new possibilities of enhancing polyplex-mediated gene delivery by codelivery of small-molecule regulators of autophagy.

Differential nanoreprotoxicity of silver nanoparticles in male somatic cells and spermatogonial stem cells

Background

Silver nanoparticles (AgNPs) possess unique physical, chemical, and biological properties. AgNPs have been increasingly used as anticancer, antiangiogenic, and antibacterial agents for the treatment of bacterial infections in open wounds as well as in ointments, bandages, and wound dressings. The present study aimed to investigate the effects of two different sizes of AgNPs (10 nm and 20 nm) in male somatic Leydig (TM3) and Sertoli (TM4) cells and spermatogonial stem cells (SSCs).

Methods

Here, we demonstrate a green and simple method for the synthesis of AgNPs using Bacillus cereus culture supernatants. The synthesized AgNPs were characterized using ultraviolet and visible absorption spectroscopy, X-ray diffraction, Fourier transform infrared spectroscopy, and transmission electron microscopy (TEM). The toxicity of the synthesized AgNPs was evaluated by the effects on cell viability, metabolic activity, oxidative stress, apoptosis, and expression of genes encoding steroidogenic and tight junction proteins.

Results

AgNPs inhibited the viability and proliferation of TM3 and TM4 cells in a dose- and size-dependent manner by damaging cell membranes and inducing the generation of reactive oxygen species, which in turn affected SSC growth on TM3 and TM4 as feeder cells. Small AgNPs (10 nm) were more cytotoxic than medium-sized nanoparticles (20 nm). TEM revealed the presence of AgNPs in the cell cytoplasm and nucleus, and detected mitochondrial damage and enhanced formation of autosomes and autolysosomes in the AgNP-treated cells. Flow cytometry analysis using Annexin V/propidium iodide staining showed massive cell death by apoptosis or necrosis. Real-time polymerase chain reaction and western blot analyses indicated that in TM3 and TM4 cells, AgNPs activated the p53, p38, and pErk1/2 signaling pathways and significantly downregulated the expression of genes related to testosterone synthesis (TM3) and tight junctions (TM4). Furthermore, the exposure of TM3 and TM4 cells to AgNPs inhibited proliferation and self-renewal of SSCs.

Conclusion

Our results suggest that AgNPs exhibit size-dependent nanoreprotoxicity in male somatic cells and SSCs, strongly suggesting that applications of AgNPs in commercial products must be carefully evaluated. Further studies of AgNPs-induced nanoreprotoxicity in animal models are required.

Development of noncytotoxic chitosan-gold nanocomposites as efficient antibacterial materials

This work describes the synthesis and characterization of noncytotoxic nanocomposites either colloidal or as films exhibiting high antibacterial activity. The biocompatible and biodegradable polymer chitosan was used as reducing and stabilizing agent for the synthesis of gold nanoparticles embedded in it. Herein, for the first time, three different chitosan grades varying in the average molecular weight and deacetylation degree (DD) were used with an optimized gold precursor concentration. Several factors were analyzed in order to obtain antimicrobial but not cytotoxic nanocomposite materials. Films based on chitosan with medium molecular weight and the highest DD exhibited the highest antibacterial activity against biofilm forming strains of Staphylococcus aureus and Pseudomonas aeruginosa. The resulting nanocomposites did not show any cytotoxicity against mammalian somatic and tumoral cells. They produced a disruptive effect on the bacteria wall while their internalization was hindered on the eukaryotic cells. This selectivity and safety make them potentially applicable as antimicrobial coatings in the biomedical field.

In vitro and in vivo toxicology of bare and PEGylated fluorescent carbonaceous nanodots in mice and zebrafish: the potential relationship with autophagy

The toxicity of CDs in mice and zebrafish and the potential relationship between toxicity and autophagy was evaluated.

Advances in studies of nanoparticle–biomembrane interactions

Nanoparticles (NPs) are widely applied in nanomedicine and diagnostics based on the interactions between NPs and the basic barrier (biomembrane). Understanding the underlying mechanism of these interactions is important for enhancing their beneficial effects and avoiding potential nanotoxicity. Experimental, mathematical and numerical modeling techniques are involved in this field. This article reviews the state-of-the-art techniques in studies of NP–biomembrane interactions with a focus on each technology's advantages and disadvantages. The aim is to better understand the mechanism of NP–biomembrane interactions and provide significant guidance for various fields, such as nanomedicine and diagnosis.