Autophagy induction by silver nanowires: a new aspect in the biocompatibility assessment of nanocomposite thin films

Essential Oils Infused Poly-ε-Caprolactone/Gelatin Electrospun Nanofibrous Mats: Biocompatibility and Antibacterial Study

Infections caused by antibiotic-resistant pathogens result in a delayed wound-healing process. As an approach to prevent infections, alternatives in the form of natural antimicrobial products have become public interest. Essential oils derived from plants are used as antimicrobials owing to their broad-spectrum activity against pathogenic organisms. In this study, essential oil from seeds of watermelon, jackfruit, and papaya was incorporated into poly-ε-caprolactone/gelatin nanofibers using an electrospinning technique. The synthesized nanofibers were smooth, continuous, and bead-free. The nanofibers were found to be mechanically competent as confirmed by the universal tensile tester. The antibacterial activity of the various essential oil-loaded nanofibrous mats was determined by disc diffusion assay. Furthermore, they were found to be non-toxic and biocompatible by MTT and CMFDA assays on fibroblast cells. The obtained results have demonstrated that essential oil-loaded nanofiber mats are promising alternatives to conventional antibacterial wound dressings.

A new strategy to integrate silver nanowires with waterborne coating to improve their antimicrobial and antiviral properties

Purpose

This study aims to focus on the preparation and characterization of the silver nanowire (AgNWs), as well as their application as antimicrobial and antivirus activities either with incorporation on the waterborne coating formulation or on their own.

Design/methodology/approach

Prepared AgNWs are characterized by different analytical instruments, such as ultraviolet-visible spectroscope, scanning electron microscope and X-ray diffraction spectrometer. All the paint formulation's physical and mechanical qualities were tested using American Society for Testing and Materials, a worldwide standard test procedure. The biological activities of the prepared AgNWs and the waterborne coating based on AgNWs were investigated. And, their effects on pathogenic bacteria, antioxidants, antiviral activity and cytotoxicity were also investigated.

Findings

The obtained results of the physical and mechanical characteristics of the paint formulation demonstrated the formulations' greatest performance, as well as giving good scrub resistance and film durability. In the antimicrobial activity, the paint did not have any activity against bacterial pathogen, whereas the AgNWs and AgNWs with paint have similar activity against bacterial pathogen with inhibition zone range from 10 to 14 mm. The development of antioxidant and cytotoxicity activity of the paint incorporated with AgNWs were also observed. The cytopathic effects of herpes simplex virus type 1 (HSV-1) were reduced in all three investigated modes of action when compared to the positive control group (HSV-1-infected cells), suggesting that these compounds have promising antiviral activity against a wide range of viruses, including DNA and RNA viruses.

Originality/value

The new waterborne coating based on nanoparticles has the potential to be promising in the manufacturing and development of paints, allowing them to function to prevent the spread of microbial infection, which is exactly what the world requires at this time.

Effect of Sublethal Concentrations of Metal Nanomaterials on Cell Energy Metabolism

Metallic nanomaterials (MNMs) are widely used in the medical field because of their photocatalytic, optical, electrical, electronic, antibacterial, and bactericidal properties. Despite the advantages of MNMs, there is a lack of complete understanding of their toxicological behavior and their interactions with cellular mechanisms that determine cell fate. Most of the existing studies are acute toxicity studies with high doses, which is not conducive to understanding the toxic effects and mechanisms of homeostasis-dependent organelles, such as mitochondria, which are involved in many cellular functions. In this study, four types of MNMs were used to investigate the effects of metallic nanomaterials on mitochondrial function and structure. We first characterized the four MNMs and selected the appropriate sublethal concentration for application in cells. Mitochondrial characterization, energy metabolism, mitochondrial damage, mitochondrial complex activity, and expression levels were evaluated using various biological methods. The results showed that the four types of MNMs greatly inhibited mitochondrial function and cell energy metabolism and that the material entering the mitochondria damaged the mitochondrial structure. Additionally, the complex activity of mitochondrial electron transport chains is critical for assessing the mitochondrial toxicity of MNMs, which may serve as an early warning of MNM-induced mitochondrial dysfunction and cytotoxicity.

Colorful Conductive Threads for Wearable Electronics: Transparent Cu-Ag Nanonets

Electronic textiles have been regarded as the basic building blocks for constructing a new generation of wearable electronics. However, the electronization of textiles often changes their original properties such as color, softness, glossiness, or flexibility. Here a rapid room-temperature fabrication method toward conductive colorful threads and fabrics with Ag-coated Cu (Cu-Ag) nanonets is demonstrated. Cu-Ag core-shell nanowires are produced through a one-pot synthesis followed by electroless deposition. According to the balance of draining and entraining forces, a fast dip-withdraw process in a volatile solution is developed to tightly wrap Cu-Ag nanonets onto the fibers of thread. The modified threads are not only conductive, but they also retain their original features with enhanced mechanical stability and dry-wash durability. Furthermore, various e-textile devices are fabricated such as a fabric heater, touch screen gloves, a wearable real-time temperature sensor, and warm fabrics against infrared thermal dissipation. These high quality and colorful conductive textiles will provide powerful materials for promoting next-generation applications in wearable electronics.

Transient, Implantable, Ultrathin Biofuel Cells Enabled by Laser-Induced Graphene and Gold Nanoparticles Composite

Transient power sources with excellent biocompatibility and bioresorablility have attracted significant attention. Here, we report high-performance, transient glucose enzymatic biofuel cells (TEBFCs) based on the laser-induced graphene (LIG)/gold nanoparticles (Au NPs) composite electrodes. Such LIG electrodes can be easily fabricated from polyimide (PI) with an infrared CO₂ laser and exhibit a low impedance (16 Ω). The resulted TEBFC yields a high open circuit potential (OCP) of 0.77 V and a maximum power density of 483.1 μW/cm². The TEBFC not only exhibits a quick response time that enables reaching the maximum OCP within 1 min but also owns a long lifetime over 28 days in vitro. The excellent biocompatibility and transient performance from in vitro and in vivo tests allow long-term implantation of TEBFCs in rats for energy harvesting. The TEBFCs with advanced processing methods provide a promising power solution for transient electronics.

Assessment of the dose-dependent biochemical and cytotoxicity of zein-coated MgO nanowires in male and female albino rats

Introduction: Recently, zein-coated MgO nanowires were synthesized, which could be promising as an effective antimicrobial compounds that can be combined in the preparation of a diversity of new dental formulations. However, there is a deficiency of information concerning their toxicological profile regarding the human health.Objective: This in vivo study aimed to explore the hepato- and nephrotoxicity of low versus high doses of zein-coated MgO nanowires in rats.Materials and Methods: A 21-day recurrent dose toxicity research was carried out. Wistar rats were divided into 2 main groups, males and females (n = 18). Each group was further subdivided into 3 subgroups: control, MgO-zein nanowires low dose, MgO-zein nanowires high dose. The low dose used was 100 mg/kg while the high dose used was 200 mg/kg.Results: The results showed that MgO-zein nanowires at both doses did not affect the electrolytes levels compared to the control levels. Also, they did not produce any significant alteration in liver function markers in both rats' genders. MgO-zein nanowires at both doses did not produce any effective alteration in serum creatinine in treated rats of both genders. Moreover, very minimal histological alterations were observed in both doses of MgO-zein nanowires in liver and kidney of both genders.Conclusion: Based on the observed safety of zein-coated MgO nanowires, it can be utilized as an effective antimicrobial compound that can be combined in the preparation of a diversity of new dental formulations.KEY MESSAGESMgO NPs are globally used in multiple fields including the therapeutic field.Zein has wide pharmaceutical applications especially coating the tablet over sugar.There are no cytotoxic studies that investigate MgO-zein nanowires safety until now.

Uptake, intracellular dissolution, and cytotoxicity of silver nanowires in cell models

The uptake, intracellular dissolution, and cytotoxicity of silver nanowires (AgNWs) in two cell models (human keratinocytes - HaCaT cells and murine macrophages) were systemically investigated for the first time. Cellular uptake of AgNWs occurred mainly via pathways of clathrin-dependent endocytosis, caveolae-dependent endocytosis, and phagocytosis. AgNWs could be internalized by two types of cells with numerous lysosomal vesicles detected in close vicinity to AgNWs. Meanwhile, AgNWs exposure caused lysosomal permeabilization and release of cathepsisn B into cytoplasm. Furthermore, for the first time, this study found that AgNWs exposure inhibited the transmembrane ATP binding cassette (ABC) efflux transporter activity, which could make AgNWs as chemosensitizers to increase the toxicity of other xenobiotic pollutants. Toxicity assays evaluating reactive oxygen species production and mitochondrial activity indicated that cytotoxicity differed for different cell types and particles. The intracellular presence of AgNWs with different diameters induced similar toxic events but to different extents. AgNWs were absorbed by macrophages more efficiently than HaCaT cells, while AgNWs exhibited only marginal cytotoxicity towards macrophages compared to HaCaT cells. Using an Ag⁺ fluorescence probe, it was found that a fraction of AgNWs was dissolved inside the lysosomes. A higher amount of released Ag⁺ was detected in HaCaT cells than in macrophages, which might partially contribute to their higher cytotoxicity in HaCaT cells. The toxicity of AgNWs in HaCaT cells and macrophages is due to the high-aspect nature of the nanowires rather than the extracellular release of Ag⁺. This study may be useful for risk assessments of AgNWs in their practical applications in the biomedical field.

Direct Observations of Silver Nanowire-Induced Frustrated Phagocytosis among NR8383 Lung Alveolar Macrophages

The interaction of long nanowires and living cells is directly related to nanowires' nanotoxicity and health impacts. Interactions of silver nanowires (AgNWs) and macrophage cell lines (NR8383) were investigated using laser scanning confocal microscopy and single cell compression (SCC). With high-resolution imaging and mechanics measurement of individual cells, AgNW-induced frustrated phagocytosis was clearly captured in conjunction with structural and property changes of cells. While frustrated phagocytosis is known for long microwires and long carbon nanotubes, this work reports first direct observations of frustrated phagocytosis of AgNWs among living cells in situ. In the case of partial penetration of AgNWs into NR8383 cells, confocal imaging revealed actin participation at the entry sites, whose behavior differs from microwire-induced frustrated phagocytosis. The impacts of frustrated phagocytosis on the cellular membrane and cytoskeleton were also quantified by measuring the mechanical properties using SCC. Taken collectively, this study reveals the structural and property characteristics of nanowire-induced frustrated phagocytosis, which deepens our understanding of nanowire-cell interactions and nanocytotoxicity.

A review on nanotoxicity and nanogenotoxicity of different shapes of nanomaterials

Nanomaterials (NMs) generally display fascinating physical and chemical properties that are not always present in bulk materials; therefore, any modification to their size, shape, or coating tends to cause significant changes in their chemical/physical and biological characteristics. The dramatic increase in efforts to use NMs renders the risk assessment of their toxicity highly crucial due to the possible health perils of this relatively uncharted territory. The different sizes and shapes of the nanoparticles are known to have an impact on organisms and an important place in clinical applications. The shape of nanoparticles, namely, whether they are rods, wires, or spheres, is a particularly critical parameter to affect cell uptake and site-specific drug delivery, representing a significant factor in determining the potency and magnitude of the effect. This review, therefore, intends to offer a picture of research into the toxicity of different shapes (nanorods, nanowires, and nanospheres) of NMs to in vitro and in vivo models, presenting an in-depth analysis of health risks associated with exposure to such nanostructures and benefits achieved by using certain model organisms in genotoxicity testing. Nanotoxicity experiments use various models and tests, such as cell cultures, cores, shells, and coating materials. This review article also attempts to raise awareness about practical applications of NMs in different shapes in biology, to evaluate their potential genotoxicity, and to suggest approaches to explain underlying mechanisms of their toxicity and genotoxicity depending on nanoparticle shape.

Techniques for In Vivo Measurement of Ligament and Tendon Strain: A Review

The critical clinical and scientific insights achieved through knowledge of in vivo musculoskeletal soft tissue strains has motivated the development of relevant measurement techniques. This review provides a comprehensive summary of the key findings, limitations, and clinical impacts of these techniques to quantify musculoskeletal soft tissue strains during dynamic movements. Current technologies generally leverage three techniques to quantify in vivo strain patterns, including implantable strain sensors, virtual fibre elongation, and ultrasound. (1) Implantable strain sensors enable direct measurements of tissue strains with high accuracy and minimal artefact, but are highly invasive and current designs are not clinically viable. (2) The virtual fibre elongation method tracks the relative displacement of tissue attachments to measure strains in both deep and superficial tissues. However, the associated imaging techniques often require exposure to radiation, limit the activities that can be performed, and only quantify bone-to-bone tissue strains. (3) Ultrasound methods enable safe and non-invasive imaging of soft tissue deformation. However, ultrasound can only image superficial tissues, and measurements are confounded by out-of-plane tissue motion. Finally, all in vivo strain measurement methods are limited in their ability to establish the slack length of musculoskeletal soft tissue structures. Despite the many challenges and limitations of these measurement techniques, knowledge of in vivo soft tissue strain has led to improved clinical treatments for many musculoskeletal pathologies including anterior cruciate ligament reconstruction, Achilles tendon repair, and total knee replacement. This review provides a comprehensive understanding of these measurement techniques and identifies the key features of in vivo strain measurement that can facilitate innovative personalized sports medicine treatment.

Evaluation of Antibacterial and Cytotoxicity Properties of Silver Nanowires and Their Composites with Carbon Nanotubes for Biomedical Applications

In this work, we prepared silver nanowires (AgNWs) via the polyol method in the presence or absence of single wall carbon nanotubes (CNTs) and tested their physicochemical, antibacterial and cytotoxic properties. Results showed that the introduction of CNTs lead to the formation of AgNWs at lower temperature, but the final product characteristics of AgNWs and AgNWs-CNT were not significantly different. AgNWs exhibited antibacterial properties against all the studied bacterial species via the formation of oxygen reactive species (ROS) and membrane damage. Furthermore, AgNWs exhibited a dose-dependent and time-dependent toxicity at concentrations ≥ 10 µg/mL. Fibroblasts appeared to be more resistant than human colorectal adenocarcinoma (Caco-2) and osteoblasts to the toxicity of AgNWs. The cytotoxicity of AgNWs was found to be related to the formation of ROS, but not to membrane damage. Overall, these results suggest that AgNWs are potential antibacterial agents against E. coli, S. aureus, MRSA and S. saprophyticus, but their dosage needs to be adjusted according to the route of administration.

Autophagy Modulated by Inorganic Nanomaterials

With the rapid development of nanotechnology, inorganic nanomaterials (NMs) have been widely applied in modern society. As human exposure to inorganic NMs is inevitable, comprehensive assessment of the safety of inorganic NMs is required. It is well known that autophagy plays dual roles in cell survival and cell death. Moreover, inorganic NMs have been proven to induce autophagy perturbation in cells. Therefore, an in-depth understanding of inorganic NMs-modulated autophagy is required for the safety assessment of inorganic NMs. This review presents an overview of a set of inorganic NMs, consisting of iron oxide NMs, silver NMs, gold NMs, carbon-based NMs, silica NMs, quantum dots, rare earth oxide NMs, zinc oxide NMs, alumina NMs, and titanium dioxide NMs, as well as how each modulates autophagy. This review emphasizes the potential mechanisms underlying NMs-induced autophagy perturbation, as well as the role of autophagy perturbation in cell fate determination. Furthermore, we also briefly review the potential roles of inorganic NMs-modulated autophagy in diagnosis and treatment of disease.

Ultralong AgNWs-induced toxicity in A549 cells and the important roles of ROS and autophagy

Safety concerns have been raised with regard to silver nanowires (AgNWs) because of their extensive applications. Recently, ultralong AgNWs have shown physical properties superior to those of short AgNWs. However, little is known about their toxicity and potential risks. In this study, we demonstrated a series of ultralong AgNWs-induced biological effects in human lung cancer epithelial cells (A549). Ultralong AgNWs treatments induced ROS generation, mitochondria-mediated apoptosis, and self-protective autophagy at nonlethal concentrations. In contrast to some previous reports, apoptosis was found not to correlate with the reduction of intracellular ROS. Measuring the processing of ROS generation, apoptosis and autophagy, we demonstrated that ROS not only enhance mitochondrial damage, but also raise protective autophagic flux in ultralong AgNW-treated cells. Moreover, ultralong AgNWs were found to be internalized into the cytoplasm of the epithelial cells. This study not only investigates ultralong AgNWs-induced cytotoxicity but also pinpoints ROS as a key signal in mechanisms of their toxicity.

Silver nanowire inks for direct-write electronic tattoo applications

Room-temperature printing of conductive traces has the potential to facilitate the direct writing of electronic tattoos and other medical devices onto biological tissue, such as human skin. However, in order to achieve sufficient electrical performance, the vast majority of conductive inks require biologically harmful post-processing techniques. In addition, most printed conductive traces will degrade with bending stresses that occur from everyday movement. In this work, water-based inks consisting of high aspect ratio silver nanowires are shown to enable the printing of conductive traces at low temperatures and without harmful post-processing. Moreover, the traces produced from these inks retain high electrical performance, even while undergoing up to 50% bending strain and cyclic bending strain over a thousand bending cycles. This ink has a rapid dry time of less than 2 minutes, which is imperative for applications requiring the direct writing of electronics on sensitive surfaces. Demonstrations of conductive traces printed onto soft, nonplanar materials, including an apple and a human finger, highlight the utility of these new silver nanowire inks. These mechanically robust films are ideally suited for printing directly on biological substrates and may find potential applications in the direct-write printing of electronic tattoos and other biomedical devices.

Crumpling of silver nanowires by endolysosomes strongly reduces toxicity

Fibrous particles interact with cells and organisms in complex ways that can lead to cellular dysfunction, cell death, inflammation, and disease. The development of conductive transparent networks (CTNs) composed of metallic silver nanowires (AgNWs) for flexible touchscreen displays raises new possibilities for the intimate contact between novel fibers and human skin. Here, we report that a material property, nanowire-bending stiffness that is a function of diameter, controls the cytotoxicity of AgNWs to nonimmune cells from humans, mice, and fish without deterioration of critical CTN performance parameters: electrical conductivity and optical transparency. Both 30- and 90-nm-diameter AgNWs are readily internalized by cells, but thinner NWs are mechanically crumpled by the forces imposed during or after endocytosis, while thicker nanowires puncture the enclosing membrane and release silver ions and lysosomal contents to the cytoplasm, thereby initiating oxidative stress. This finding extends the fiber pathology paradigm and will enable the manufacture of safer products incorporating AgNWs.

In vitro exposure of a 3D-tetraculture representative for the alveolar barrier at the air-liquid interface to silver particles and nanowires

BACKGROUND

The present study aimed to evaluate the potential differences in the biological effects of two types of spherical silver particles of 20 and 200 nm (Ag20 and Ag200), and of PVP-coated silver nanowires (AgNWs) with a diameter of 50 nm and length up to 50 μm, using a complex 3D model representative for the alveolar barrier cultured at air-liquid interface (ALI). The alveolar model was exposed to 0.05, 0.5 and 5 μg/cm2 of test compounds at ALI using a state-of-the-art exposure system (Vitrocell™Cloud System). Endpoints related to the oxidative stress induction, anti-oxidant defence mechanisms, pro-inflammatory responses and cellular death were selected to evaluate the biocompatibility of silver particles and nanowires (AgNMs) and to further ascribe particular biological effects to the different morphologic properties between the three types of AgNMs evaluated.

RESULTS

Significant cytotoxic effect was observed for all three types of AgNMs at the highest tested doses. The increased mRNA levels of the pro-apoptotic gene CASP7 suggests that apoptosis may occur after exposure to AgNWs. All three types of AgNMs increased the mRNA level of the anti-oxidant enzyme HMOX-1 and of the metal-binding anti-oxidant metallothioneins (MTs), with AgNWs being the most potent inducer. Even though all types of AgNMs induced the nuclear translocation of NF-kB, only AgNWs increased the mRNA level of pro-inflammatory mediators. The pro-inflammatory response elicited by AgNWs was further confirmed by the increased secretion of the 10 evaluated interleukins.

CONCLUSION

In the current study, we demonstrated that the direct exposure of a complex tetra-culture alveolar model to different types of AgNMs at ALI induces shape- and size-specific biological responses. From the three AgNMs tested, AgNWs were the most potent in inducing biological alterations. Starting from 50 ng/cm2, a dose representative for an acute exposure in a high exposure occupational setting, AgNWs induced prominent changes indicative for a pro-inflammatory response. Even though the acute responses towards a dose representative for a full-lifetime exposure were also evaluated, chronic exposure scenarios at low dose are still unquestionably needed to reveal the human health impact of AgNMs during realistic conditions.

Differentiation regulation of mesenchymal stem cells via autophagy induced by structurally-different silica based nanobiomaterials

Autophagy is associated with the proliferation and differentiation of mesenchymal stem cells (MSCs). In this study, we investigated the biological impact of silica-based nanobiomateiral-induced autophagy on the differentiation of MSCs, in which the nanoparticulate cues include solid silica nanoparticles (SSN), mesoporous silica nanoparticles (MSN) and biodegradable mesoporous silica nanoparticles (DMSN). The treatment with SSN significantly up-regulated the LC3-II expression via ERK1/2 and AKT/mTOR signaling pathways compared to DMSN and MSN, leading to a higher autophagic activity in MSCs. The enhanced protein adsorption of DMSN and MSN could prevent the direct interaction between cells and nanoparticles, which consequently reduces the autophagic stimulation of MSCs. It should be noted that MSCs exhibited increased differentiation potential when the autophagic activity was enhanced by the treatment with different nanoparticles. In comparison, no difference in the cell differentiation potential was found when an autophagy inhibitor (chloroquine, CQ) was incorporated in all groups. The study may contribute to the development of silica-based nanobiomaterials in the future.

Poly-ε-Caprolactone/Gelatin Hybrid Electrospun Composite Nanofibrous Mats Containing Ultrasound Assisted Herbal Extract: Antimicrobial and Cell Proliferation Study

Electrospun fibers have emerged as promising materials in the field of biomedicine, due to their superior physical and cell supportive properties. In particular, electrospun mats are being developed for advanced wound dressing applications. Such applications require the firers to possess excellent antimicrobial properties in order to inhibit potential microbial colonization from resident and non-resident bacteria. In this study, we have developed Poly-ε-Caprolactone /gelatin hybrid composite mats loaded with natural herbal extract (Gymnema sylvestre) to prevent bacterial colonization. As-spun scaffolds exhibited good wettability and desirable mechanical properties retaining their fibrous structure after immersing them in phosphate buffered saline (pH 7.2) for up to 30 days. The initial burst release of Gymnema sylvestre prevented the colonization of bacteria as confirmed by the radial disc diffusion assay. Furthermore, the electrospun mats promoted cellular attachment, spreading and proliferation of human primary dermal fibroblasts and cultured keratinocytes, which are crucial parenchymal cell-types involved in the skin recovery process. Overall these results demonstrated the utility of Gymnema sylvestre impregnated electrospun PCL/Gelatin nanofibrous mats as an effective antimicrobial wound dressing.

In Vitro Dermal Safety Assessment of Silver Nanowires after Acute Exposure: Tissue vs. Cell Models

Silver nanowires (AgNW) are attractive materials that are anticipated to be incorporated into numerous consumer products such as textiles, touchscreen display, and medical devices that could be in direct contact with skin. There are very few studies on the cellular toxicity of AgNW and no studies that have specifically evaluated the potential toxicity from dermal exposure. To address this question, we investigated the dermal toxicity after acute exposure of polymer-coated AgNW with two sizes using two models, human primary keratinocytes and human reconstructed epidermis. In keratinocytes, AgNW are rapidly and massively internalized inside cells leading to dose-dependent cytotoxicity that was not due to Ag⁺ release. Analysing our data with different dose metrics, we propose that the number of NW is the most appropriate dose-metric for studies of AgNW toxicity. In reconstructed epidermis, the results of a standard in vitro skin irritation assay classified AgNW as non-irritant to skin and we found no evidence of penetration into the deeper layer of the epidermis. The findings show that healthy and intact epidermis provides an effective barrier for AgNW, although the study does not address potential transport through follicles or injured skin. The combined cell and tissue model approach used here is likely to provide an important methodology for assessing the risks for skin exposure to AgNW from consumer products.

Nanomaterial-Enabled Wearable Sensors for Healthcare

Highly sensitive wearable sensors that can be conformably attached to human skin or integrated with textiles to monitor the physiological parameters of human body or the surrounding environment have garnered tremendous interest. Owing to the large surface area and outstanding material properties, nanomaterials are promising building blocks for wearable sensors. Recent advances in the nanomaterial-enabled wearable sensors including temperature, electrophysiological, strain, tactile, electrochemical, and environmental sensors are presented in this review. Integration of multiple sensors for multimodal sensing and integration with other components into wearable systems are summarized. Representative applications of nanomaterial-enabled wearable sensors for healthcare, including continuous health monitoring, daily and sports activity tracking, and multifunctional electronic skin are highlighted. Finally, challenges, opportunities, and future perspectives in the field of nanomaterial-enabled wearable sensors are discussed.

Activation of autophagy by elevated reactive oxygen species rather than released silver ions promotes cytotoxicity of polyvinylpyrrolidone-coated silver nanoparticles in hematopoietic cells

Silver nanoparticles (AgNPs) are the most commonly used engineered nanomaterials in commercialized products because of their antimicrobial activity. Previously, we have shown that polyvinylpyrrolidone (PVP)-coated AgNPs have an anti-leukemia effect against human myeloid leukemia cells; however, whether AgNPs are able to trigger autophagy in normal hematopoietic cells and the role of autophagy in AgNP-induced cytotoxicity remain unclear. In the current study, we observed that AgNPs were taken up by murine pro-B cells (Ba/F3), and then promoted accumulation of autophagosomes, which resulted from the induction of autophagy rather than the blockade of autophagic flux. AgNPs induced cytotoxicity in a dose-dependent manner accompanied by apoptosis and DNA damage through the production of reactive oxygen species (ROS) and the release of silver ions. The ROS-mediated mTOR signaling pathway was responsible for the induction of autophagy. More importantly, the inhibition of autophagy with the addition of 3-methyladenine (3-MA) or silencing of Atg5 significantly attenuated the cytotoxicity of AgNPs in Ba/F3. These findings suggest that autophagy is involved in the cytotoxicity of PVP-coated AgNPs in normal hematopoietic cells, and the inhibition of autophagy is a novel and potent strategy to protect normal hematopoietic cells upon treatment with AgNPs.

Biocompatible, optically transparent, patterned, and flexible electrodes and radio-frequency antennas prepared from silk protein and silver nanowire networks

We demonstrated biocompatible, optically transparent and flexible electrodes by embedding AgNWs just below the surface of the silk fibroin film.

Highly sensitive, direct and real-time detection of silver nanowires by using a quartz crystal microbalance

For several decades, silver nanomaterials (AgNMs) have been used in various research areas and commercial products. Among the many AgNMs, silver nanowires (AgNWs) are one of the mostly widely used nanomaterials due to their high electrical and thermal conductivity. However, recent studies have investigated the toxicity of AgNWs. For this reason, it is necessary to develop a successful detection method of AgNWs for protecting human health. In this study, label-free, highly sensitive, direct, and real-time detection of AgNWs is performed for the first time. The detection mechanism is based on the resonance frequency shift upon the mass change from the hybridization between the probe DNA on the electrode and the linker DNA attached on AgNWs. The frequency shift is measured by using a quartz crystal microbalance. We are able to detect 1 ng ml^-1 of AgNWs in deionized water in real-time. Moreover, our detection method can selectively detect AgNWs among other types of one-dimensional nanomaterials and can also be applied to detection in drinking water.

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.

Insight into membrane selectivity of linear and branched polyethylenimines and their potential as biocides for advanced wound dressings

We report here structure-property relationship between linear and branched polyethylene imines by examining their antimicrobial activities against wide range of pathogens. Both the polymers target the cytoplasmic membrane of bacteria and yeasts, eliciting rapid microbicidal properties. Using multiscale molecular dynamic simulations, we showed that, in both fully or partially protonated forms LPEI discriminates between mammalian and bacterial model membranes whereas BPEI lacks selectivity for both the model membranes. Simulation results suggest that LPEI forms weak complex with the zwitterionic lipids whereas the side chain amino groups of BPEI sequester the zwitterionic lipids by forming tight complex. Consistent with these observations, label-free cell impedance measurements, cell viability assays and high content analysis indicate that BPEI is cytotoxic to human epithelial and fibroblasts cells. Crosslinking of BPEI onto electrospun gelatin mats attenuate the cytotoxicity for fibroblasts while retaining the antimicrobial activity against Gram-positive and yeasts strains. PEI crosslinked gelatin mats elicit bactericidal activity by contact-mediated killing and durable to leaching for 7days. The potent antimicrobial activity combined with enhanced selectivity of the crosslinked ES gelatin mats would expand the arsenel of biocides in the management of superficial skin infections. The contact-mediated microbicidal properties may avert antimicrobial resistance and expand the diversity of applications to prevent microbial contamination.

STATEMENT OF SIGNIFICANCE

Current commercially available advanced wound dressings are either impregnated with metallic silver or silver salts which have side effects or may not avert antimicrobial resistance. In this article, we have used multidisciplinary approach comprising of computational, chemical and biological methods to understand the antimicrobial properties and biocompatibility of linear (LPEI) and branched (BPEI) polyethylenimines. We then applied this knowledge to develop dual purpose wound dressings containing these polymers, which encourages healing while maintain antimicrobial activity. In addition, the approach can be expanded to rationalize the antimicrobial vs. cytotoxicity of other cationic polymers and the method of crosslinking would enhance their potentials as biocides for advanced materials.

Effects of Atrazine and Chlorpyrifos on Autophagy-Related Genes in the Brain of Common Carp: Health-Risk Assessments

This study assessed the impacts of atrazine (ATR), chlorpyrifos (CPF), and a combined ATR/CPF exposure on the brain of common carp (Cyprinus carpio L.). The carp were sampled after a 40-days exposure to CPF and ATR, individually or in combination, followed by a 40-days recovery period to measure autophagy and antioxidant activity. The results indicate that the anti-superoxide anion and anti-hydroxy radical activities decreased upon exposure to ATR, CPF, and the ATR/CPF combination but increased after a subsequent 40-days recovery period. Quantitative real-time PCR and Western blot analyses revealed that the mRNA and protein levels of LC3B and dynein in common carp decreased significantly after exposure to ATR and CPF alone or in combination. Moreover, the mRNA and protein levels of beclin1 gene decreased significantly only in the 116 and 11.3 μg/L treatment groups. However, the mRNA and protein levels of all tested genes increased significantly after a 40-days recovery. Transmission electron microscope demonstrated the occurrence of autolysosomes in the recovery groups but not in the exposure groups. These results suggest that exposure to ATR, CPF, or their combination promotes oxidative stress and autophagic responses in the brain of common carp.

Antifungal properties of lecithin- and terbinafine-loaded electrospun poly(ε-caprolactone) nanofibres

We investigated the effect of terbinafine- and egg lecithin-loaded PCL mats on mechanical properties, swellability, biocompatibility andin vitroandex vivoantifungal efficacy against pathogenic moulds and dermatophytes.

A comparison of catabolic pathways induced in primary macrophages by pristine single walled carbon nanotubes and pristine graphene

Understanding the correlation between the physico-chemical properties of carbonaceous nanomaterials and how these properties impact on cells and subcelluar mechanisms is critical to their risk assessment and safe translation into engineered devices.

Electrochemical monitoring of colloidal silver nanowires in aqueous samples

Silver nanowires (NWs) are increasingly utilized in technological materials and consumer products, but an effective analytical technique is not yet available to measure their concentration in the environment. Here, we present an electrochemical method to quantify Ag NWs suspended in aqueous solution. Using linear sweep voltammetry, the Ag NWs are identified by the peak potential while their concentration is revealed by the intensity of the peak current. The peak current varies linearly with the Ag NW concentration with a low detection limit of 3.50 ng mL(-1). This method is also successfully applied to quantify Ag NWs in mixtures with nanoparticles, through their specific oxidation behavior, and in wastewater obtained after the Ag NW film preparation process.

Atrazine and chlorpyrifos exposure induces liver autophagic response in common carp

Under normal conditions, autophagy occurs at basal levels but can be induced rapidly in response to stress conditions and extracellular signals. Increasing experimental evidence indicates that the expression of autophagy-related genes play very important roles in toxicology. Atrazine (ATR) and chlorpyrifos (CPF) are the most common agrochemical in the freshwater ecosystems of the world. This study assessed the effects of ATR, CPF and combined ATR/CPF exposure on the liver of common carp. Carp were sampled after a 40-d exposure to ATR and CPF, individually or in combination, followed by a 40-d recovery to measure the mRNA and protein levels of autophagy-related genes in the liver. In addition, we also investigated the change in ultrastructure in the liver. The results revealed that the mRNA and protein levels of microtubule-associated protein 1 light chain 3 B (LC3B) and dynein were significantly induced in the treated groups compared to the solvent control group. Transmission electron microscope assays indicated that autolysosomes were observed in the exposure and recovery groups. These results indicated that ATR and CPF could induce autophagy in carp liver. To the best of our knowledge, this is the first report to study the autophagy effects caused by sub-chronic exposure to ATR, CPF and the ATR/CPF combination in common carp. The information presented in the present study may provide new insights into the mechanisms used by fish to adapt to stressful environments.

Eu3+:Y2O3@CNTs—a rare earth filled carbon nanotube nanomaterial with low toxicity and good photoluminescence properties

New fluorescent nanomaterials—europium-doped yttria filled CNTs with low toxicity and good photoluminescence properties were synthesized using a supercritical method.

Green synthesis of hyaluronic acid-based silver nanoparticles and their enhanced delivery to CD44+ cancer cells

A novel hyaluronic acid (HA)-based strategy for the green synthesis of AgNP was developed, in which HA was used as both the reducer and stabilizer, and the HA-modified AgNP can target CD44-overexpressed cancer cells for improved therapy.

Inhalation of silver nanomaterials--seeing the risks

Demand for silver engineered nanomaterials (ENMs) is increasing rapidly in optoelectronic and in health and medical applications due to their antibacterial, thermal, electrical conductive, and other properties. The continued commercial up-scaling of ENM production and application needs to be accompanied by an understanding of the occupational health, public safety and environmental implications of these materials. There have been numerous in vitro studies and some in vivo studies of ENM toxicity but their results are frequently inconclusive. Some of the variability between studies has arisen due to a lack of consistency between experimental models, since small differences between test materials can markedly alter their behaviour. In addition, the propensity for the physicochemistry of silver ENMs to alter, sometimes quite radically, depending on the environment they encounter, can profoundly alter their bioreactivity. Consequently, it is important to accurately characterise the materials before use, at the point of exposure and at the nanomaterial-tissue, or "nanobio", interface, to be able to appreciate their environmental impact. This paper reviews current literature on the pulmonary effects of silver nanomaterials. We focus our review on describing whether, and by which mechanisms, the chemistry and structure of these materials can be linked to their bioreactivity in the respiratory system. In particular, the mechanisms by which the physicochemical properties (e.g., aggregation state, morphology and chemistry) of silver nanomaterials change in various biological milieu (i.e., relevant proteins, lipids and other molecules, and biofluids, such as lung surfactant) and affect subsequent interactions with and within cells will be discussed, in the context not only of what is measured but also of what can be visualized.

Short versus long silver nanowires: a comparison of in vivo pulmonary effects post instillation

Background

Silver nanowires (Ag NWs) are increasingly being used to produce touchscreens for smart phones and computers. When applied in a thin film over a plastic substrate, Ag NWs create a transparent, highly-conductive network of fibers enabling the touch interface between consumers and their electronics. Large-scale application methods utilize techniques whereby Ag NW suspensions are deposited onto substrates via droplets. Aerosolized droplets increase risk of occupational Ag NW exposure. Currently, there are few published studies on Ag NW exposure-related health effects. Concerns have risen about the potential for greater toxicity from exposure to high-aspect ratio nanomaterials compared to their non-fibrous counterparts. This study examines whether Ag NWs of varying lengths affect biological responses and silver distribution within the lungs at different time-points.

Methods

Two different sizes of Ag NWs (2 μm [S-Ag NWs] and 20 μm [L-Ag NWs]) were tested. Male, Sprague-Dawley rats were intratracheally instilled with Ag NWs (0, 0.1, 0.5, or 1.0 mg/kg). Broncho-alveolar lavage fluid (BALF) and lung tissues were obtained at 1, 7, and 21 days post exposure for analysis of BAL total cells, cell differentials, and total protein as well as tissue pathology and silver distribution.

Results and conclusions

The two highest doses produced significant increases in BAL endpoints. At Day 1, Ag NWs increased total cells, inflammatory polymorphonuclear cells (PMNs), and total protein. PMNs persisted for both Ag NW types at Day 7, though not significantly so, and by Day 21, PMNs appeared in line with sham control values. Striking histopathological features associated with Ag NWs included 1) a strong influx of eosinophils at Days 1 and 7; and 2) formation of Langhans and foreign body giant cells at Days 7 and 21. Epithelial sloughing in the terminal bronchioles (TB) and cellular exudate in alveolar regions were also common. By Day 21, Ag NWs were primarily enclosed in granulomas or surrounded by numerous macrophages in the TB-alveolar duct junction. These findings suggest short and long Ag NWs produce pulmonary toxicity; thus, further research into exposure-related health effects and possible exposure scenarios are necessary to ensure human safety as Ag NW demand increases.

Electronic supplementary material

The online version of this article (doi:10.1186/s12989-014-0052-6) contains supplementary material, which is available to authorized users.

Cytocompatibility and cellular internalization mechanisms of SiC/SiO2 nanowires

First evidence of in vitro cytocompatibility of SiC/SiO2 core-shell nanowires is reported. Different internalization mechanisms by adenocarcinomic alveolar basal epithelial cells, monocytic cell line derived from an acute monocytic leukemia, breast cancer cells, and normal human dermal fibroblasts are shown. The internalization occurs mainly for macropinocytosis and sporadically by direct penetration in all cell models considered, whereas it occurred for phagocytosis only in monocytic leukemia cells. The cytocompatibility of the nanowires is proved by the analysis of cell proliferation, cell cycle progression, and oxidative stress on the cells treated with NWs as compared to controls. Reactive oxygen species generation was detected as an early event that then quickly run out with a rapid decrease only in adenocarcinomic alveolar basal epithelial and human dermal fibroblasts cells. In all the cell lines, the intracellular presence of NWs induce the same molecular events but to a different extent: peroxidation of membrane lipids and oxidation of proteins. The NWs do not elicit either midterm (72 h) or long-term (10 days) cytotoxic activity leading to irreversible cellular damages or death. Our results are important in view of a possible use of SiC/SiO2 core-shell structures acting as biomolecule-delivery vectors or intracellular electrodes.

Autophagy as a Possible Underlying Mechanism of Nanomaterial Toxicity

The rapid development of nanotechnologies is raising safety concerns because of the potential effects of engineered nanomaterials on human health, particularly at the respiratory level. Since the last decades, many in vivo studies have been interested in the pulmonary effects of different classes of nanomaterials. It has been shown that some of them can induce toxic effects, essentially depending on their physico-chemical characteristics, but other studies did not identify such effects. Inflammation and oxidative stress are currently the two main mechanisms described to explain the observed toxicity. However, the exact underlying mechanism(s) still remain(s) unknown and autophagy could represent an interesting candidate. Autophagy is a physiological process in which cytoplasmic components are digested via a lysosomal pathway. It has been shown that autophagy is involved in the pathogenesis and the progression of human diseases, and is able to modulate the oxidative stress and pro-inflammatory responses. A growing amount of literature suggests that a link between nanomaterial toxicity and autophagy impairment could exist. In this review, we will first summarize what is known about the respiratory effects of nanomaterials and we will then discuss the possible involvement of autophagy in this toxicity. This review should help understand why autophagy impairment could be taken as a promising candidate to fully understand nanomaterials toxicity.

Size-dependent cytotoxicity of silver nanoparticles in human lung cells: the role of cellular uptake, agglomeration and Ag release

Background

Silver nanoparticles (AgNPs) are currently one of the most manufactured nanomaterials. A wide range of toxicity studies have been performed on various AgNPs, but these studies report a high variation in toxicity and often lack proper particle characterization. The aim of this study was to investigate size- and coating-dependent toxicity of thoroughly characterized AgNPs following exposure of human lung cells and to explore the mechanisms of toxicity.

Methods

BEAS-2B cells were exposed to citrate coated AgNPs of different primary particle sizes (10, 40 and 75 nm) as well as to 10 nm PVP coated and 50 nm uncoated AgNPs. The particle agglomeration in cell medium was investigated by photon cross correlation spectroscopy (PCCS); cell viability by LDH and Alamar Blue assay; ROS induction by DCFH-DA assay; genotoxicity by alkaline comet assay and γH₂AX foci formation; uptake and intracellular localization by transmission electron microscopy (TEM); and cellular dose as well as Ag release by atomic absorption spectroscopy (AAS).

Results

The results showed cytotoxicity only of the 10 nm particles independent of surface coating. In contrast, all AgNPs tested caused an increase in overall DNA damage after 24 h assessed by the comet assay, suggesting independent mechanisms for cytotoxicity and DNA damage. However, there was no γH₂AX foci formation and no increased production of intracellular reactive oxygen species (ROS). The reasons for the higher toxicity of the 10 nm particles were explored by investigating particle agglomeration in cell medium, cellular uptake, intracellular localization and Ag release. Despite different agglomeration patterns, there was no evident difference in the uptake or intracellular localization of the citrate and PVP coated AgNPs. However, the 10 nm particles released significantly more Ag compared with all other AgNPs (approx. 24 wt% vs. 4–7 wt%) following 24 h in cell medium. The released fraction in cell medium did not induce any cytotoxicity, thus implying that intracellular Ag release was responsible for the toxicity.

Conclusions

This study shows that small AgNPs (10 nm) are cytotoxic for human lung cells and that the toxicity observed is associated with the rate of intracellular Ag release, a ‘Trojan horse’ effect.

Silver nanowire exposure results in internalization and toxicity to Daphnia magna

Nanowires (NWs), high-aspect-ratio nanomaterials, are increasingly used in technological materials and consumer products and may have toxicological characteristics distinct from nanoparticles. We carried out a comprehensive evaluation of the physicochemical stability of four silver nanowires (AgNWs) of two sizes and coatings and their toxicity to Daphnia magna . Inorganic aluminum-doped silica coatings were less effective than organic poly(vinyl pyrrolidone) coatings at preventing silver oxidation or Ag(+) release and underwent a significant morphological transformation within 1 h following addition to low ionic strength Daphnia growth media. All AgNWs were highly toxic to D. magna but less toxic than ionic silver. Toxicity varied as a function of AgNW dimension, coating, and solution chemistry. Ag(+) release in the media could not account for observed AgNW toxicity. Single-particle inductively coupled plasma mass spectrometry distinguished and quantified dissolved and nanoparticulate silver in microliter-scale volumes of Daphnia magna hemolymph with a limit of detection of approximately 10 ppb. The silver levels within the hemolymph of Daphnia exposed to both Ag(+) and AgNW met or exceeded the initial concentration in the growth medium, indicating effective accumulation during filter feeding. Silver-rich particles were the predominant form of silver in hemolymph following exposure to both AgNWs and Ag(+). Scanning electron microscopy imaging of dried hemolymph found both AgNWs and silver precipitates that were not present in the AgNW stock or the growth medium. Both organic and inorganic coatings on the AgNW were transformed during ingestion or absorption. Pathway, gene ontology, and clustering analyses of gene expression response indicated effects of AgNWs distinct from ionic silver on Daphnia magna .

Interplay between autophagy and apoptosis mediated by copper oxide nanoparticles in human breast cancer cells MCF7

BACKGROUND

Metal oxide nanoparticles are well known to generate oxidative stress and deregulate normal cellular activities. Among these, transition metals copper oxide nanoparticles (CuO NPs) are more compelling than others and able to modulate different cellular responses.

METHODS

In this work, we have synthesized and characterized CuO NPs by various biophysical methods. These CuO NPs (~30nm) induce autophagy in human breast cancer cell line, MCF7 in a time- and dose-dependent manner. Cellular autophagy was tested by MDC staining, induction of green fluorescent protein-light chain 3 (GFP-LC3B) foci by confocal microscopy, transfection of pBABE-puro mCherry-EGFP-LC3B plasmid and Western blotting of autophagy marker proteins LC3B, beclin1 and ATG5. Further, inhibition of autophagy by 3-MA decreased LD50 doses of CuO NPs. Such cell death was associated with the induction of apoptosis as revealed by FACS analysis, cleavage of PARP, de-phosphorylation of Bad and increased cleavage product of caspase 3. siRNA mediated inhibition of autophagy related gene beclin1 also demonstrated similar results. Finally induction of apoptosis by 3-MA in CuO NP treated cells was observed by TEM.

RESULTS

This study indicates that CuO NPs are a potent inducer of autophagy which may be a cellular defense against the CuO NP mediated toxicity and inhibition of autophagy switches the cellular response into apoptosis.

CONCLUSIONS

A combination of CuO NPs with the autophagy inhibitor is essential to induce apoptosis in breast cancer cells.

GENERAL SIGNIFICANCE

CuO NP induced autophagy is a survival strategy of MCF7 cells and inhibition of autophagy renders cellular fate to apoptosis.

Magnetic core-shell nanoparticles for drug delivery by nebulization

BACKGROUND

Aerosolized therapeutics hold great potential for effective treatment of various diseases including lung cancer. In this context, there is an urgent need to develop novel nanocarriers suitable for drug delivery by nebulization. To address this need, we synthesized and characterized a biocompatible drug delivery vehicle following surface coating of Fe3O4 magnetic nanoparticles (MNPs) with a polymer poly(lactic-co-glycolic acid) (PLGA). The polymeric shell of these engineered nanoparticles was loaded with a potential anti-cancer drug quercetin and their suitability for targeting lung cancer cells via nebulization was evaluated.

RESULTS

Average particle size of the developed MNPs and PLGA-MNPs as measured by electron microscopy was 9.6 and 53.2 nm, whereas their hydrodynamic swelling as determined using dynamic light scattering was 54.3 nm and 293.4 nm respectively. Utilizing a series of standardized biological tests incorporating a cell-based automated image acquisition and analysis procedure in combination with real-time impedance sensing, we confirmed that the developed MNP-based nanocarrier system was biocompatible, as no cytotoxicity was observed when up to 100 μg/ml PLGA-MNP was applied to the cultured human lung epithelial cells. Moreover, the PLGA-MNP preparation was well-tolerated in vivo in mice when applied intranasally as measured by glutathione and IL-6 secretion assays after 1, 4, or 7 days post-treatment. To imitate aerosol formation for drug delivery to the lungs, we applied quercitin loaded PLGA-MNPs to the human lung carcinoma cell line A549 following a single round of nebulization. The drug-loaded PLGA-MNPs significantly reduced the number of viable A549 cells, which was comparable when applied either by nebulization or by direct pipetting.

CONCLUSION

We have developed a magnetic core-shell nanoparticle-based nanocarrier system and evaluated the feasibility of its drug delivery capability via aerosol administration. This study has implications for targeted delivery of therapeutics and poorly soluble medicinal compounds via inhalation route.