Size effects of single-walled carbon nanotubes on in vivo and in vitro pulmonary toxicity

Nanocomposite Hydrogels Based on Poly(vinyl alcohol) and Carbon Nanotubes for NIR-Light Triggered Drug Delivery

Photothermal nanocomposite hydrogels are promising materials for remotely triggering drug delivery by near-infrared (NIR) radiation stimuli. In this work, a novel hydrogel based on poly(vinyl alcohol), poly(vinyl methyl ether-alt-maleic acid), poly(vinyl methyl ether), and functionalized multiwalled carbon nanotubes (MWCNT-f) was prepared by the freeze/thaw method. A comparative characterization of materials (with and without MWCNT-f) was carried out by infrared spectroscopy, differential scanning calorimetry, scanning electron microscopy, mechanical assays, swelling kinetics measurements, and photothermal analysis under NIR irradiation. Hydrophilic chemotherapeutic 5-fluorouracil (5-FU) and hydrophobic ibuprofen drugs were independently loaded into hydrogels, and the drug release profiles were obtained under passive and NIR-irradiation conditions. The concentration-dependent cytotoxicity of materials was studied in vitro using noncancerous cells and cancer cells. Notable changes in the microstructure and physicochemical properties of hydrogels were observed by adding a low content (0.2 wt %) of MWCNT-f. The cumulative release amounts of 5-FU and ibuprofen from the hydrogel containing MWCNT-f were significantly increased by 21 and 39%, respectively, through the application of short-term NIR irradiation pulses. Appropriate concentrations of the nanocomposite hydrogel loaded with 5-FU produced cytotoxicity in cancer cells without affecting noncancerous cells. The overall properties of the MWCNT-f-containing hydrogel and its photothermal behavior make it an attractive material to promote the release of hydrophilic and hydrophobic drugs, depending on the treatment requirements.

Carbon Nanotubes and Graphene Materials as Xenobiotics in Living Systems: Is There a Consensus on Their Safety?

Carbon nanotubes and graphene are two types of nanomaterials that have unique properties and potential applications in various fields, including biomedicine, energy storage, and gas sensing. However, there is still a debate about the safety of these materials, and there is yet to be a complete consensus on their potential risks to human health and the environment. While some studies have provided recommendations for occupational exposure limits, more research is needed to fully understand the potential risks of these materials to human health and the environment. In this review, we will try to summarize the advantages and disadvantages of using carbon nanotubes and graphene as well as composites containing them in the context of their biocompatibility and toxicity to living systems. In addition, we overview current policy guidelines and technical regulations regarding the safety of carbon-based nanomaterials.

Anti-Infective and Toxicity Properties of Carbon Based Materials: Graphene and Functionalized Carbon Nanotubes

Recently, antimicrobial activities of various carbon-based nanomaterials against specific pathogens have become one of the most significant research interests in this field. Carbon nanotubes (CNTs) are promising multidisciplinary nanostructures in biomedicine, drug delivery, genetic engineering, biosensors, and artificial implants. However, the biomedical administration of CNTs is dependent on their solubility, toxicity, and biocompatibility, as well as novel drug-delivery applications through optimization of the drug's loading capacity, cellular absorption, and continuous release within the target cell. The usage of CNTs and Graphene materials as antimicrobial agents and nanocarriers for antibiotics delivery would possibly improve their bioavailability and facilitate better anti-infective therapy. However, it is worth mentioning that CNTs' antimicrobial activity and toxicity are highly dependent on their preparation and synthesis method. Various types of research have confirmed that diameter, length, residual catalyst, metal content, surface coating, electronic structure, and dispersibility would affect CNTs' toxicity toward bacteria and human cells. In this review article, a general study was performed on the antimicrobial properties of carbon-based nanomaterials, as well as their toxicity and applications in confronting different microorganisms. This study could be useful for researchers who are looking for new and effective drug delivery methods in the field of microbial resistance.

Research on Mechanism of miR-488-5p Carried with Magnetic Carbon Nanotubes in Restraining Lymphatic Metastasis in Cervical Cancer Through Induction of mTOR/P70S6K Signaling Pathway

This study intends to discuss mechanism of miR-488-5p carried with magnetic carbon nanotubes (MAGCNTs) in restraining lymphatic metastasis in cervical cancer through induction of mTOR/P70S6K signaling pathway. Fifty female rats were randomly divided into five sets, which included control set, miR-488-5p set, empty carrier set, set of miR-488-5p carrier and inhibitor set. The MAGCNTs were prepared and characterized. Condition and quantity of lymphatic metastasis in cervical cancer, miR-488-5p expression and protein expression of factors related with mTOR/P70S6K signaling transduction pathway were observed. Quantity of lymphatic metastasis in the control set was highest, while quantity of lymphatic metastasis in the set of miR-488-5p and carrier were lowest. Expressions of miR-488-5p in of the miR-488-5p and carrier sets were highest and lowest in the control set, and mTOR/P70S6K expression was reversed. miR-488-5p was carried with multi-walled carbon nanotubes (MWCNTs) and entered into cells more rapidly. There was over expression of miR-488-5p and activity of mTOR/P70S6K signaling pathway was restrained. The information conduction was slowed down, and therefore, the lymphatic metastasis in the cervical cancer was restrained.

Combined effect of single-walled carbon nanotubes and cadmium on human lung cancer cells

Co-exposure of widely used single-walled carbon nanotubes (SWCNTs) and ubiquitous cadmium (Cd) to humans through ambient air is unavoidable. Studies on joint toxicity of SWCNTs and Cd in human cells are scarce. We aimed to investigate the joint effects of SWCNTs and Cd in human lung epithelial (A549) cells. Results showed that SWCNTs were safe while Cd induce significant toxicity to A549 cells. Remarkably, Cd-induced cell viability reduction, lactate dehydrogenase leakage, cell cycle arrest, dysregulation of apoptotic gene (p53, bax, bcl-2, casp3, and casp9), and mitochondrial membrane potential depletion were significantly mitigated following SWCNTs co-exposure. Cd-induced intracellular level of reactive oxygen species, hydrogen peroxide, and lipid peroxidation were significantly attenuated by SWCNT co-exposure. Moreover, glutathione depletion and lower activity of antioxidant enzymes after Cd exposure were also effectively abrogated by co-exposure of SWCNTs. Inductively coupled plasma-mass spectrometry study indicated that higher adsorption of Cd on SCWNTs might decreased cellular uptake and the toxic potential of Cd in A549 cells. Our work warranted further research to explore the potential mechanism of joint effects of SWCNTs and Cd at in vivo levels.

Innate but Not Adaptive Immunity Regulates Lung Recovery from Chronic Exposure to Graphene Oxide Nanosheets

Graphene has drawn a lot of interest in the material community due to unique physicochemical properties. Owing to a high surface area to volume ratio and free oxygen groups, the oxidized derivative, graphene oxide (GO) has promising potential as a drug delivery system. Here, the lung tolerability of two distinct GO varying in lateral dimensions is investigated, to reveal the most suitable candidate platform for pulmonary drug delivery. Following repeated chronic pulmonary exposure of mice to GO sheet suspensions, the innate and adaptive immune responses are studied. An acute and transient influx of neutrophils and eosinophils in the alveolar space, together with the replacement of alveolar macrophages by interstitial ones and a significant activation toward anti-inflammatory subsets, are found for both GO materials. Micrometric GO give rise to persistent multinucleated macrophages and granulomas. However, neither adaptive immune response nor lung tissue remodeling are induced after exposure to micrometric GO. Concurrently, milder effects and faster tissue recovery, both associated to a faster clearance from the respiratory tract, are found for nanometric GO, suggesting a greater lung tolerability. Taken together, these results highlight the importance of dimensions in the design of biocompatible 2D materials for pulmonary drug delivery system.

Broad-Spectrum Theranostics and Biomedical Application of Functionalized Nanomaterials

Nanotechnology is an important branch of science in therapies known as “nanomedicine” and is the junction of various fields such as material science, chemistry, biology, physics, and optics. Nanomaterials are in the range between 1 and 100 nm in size and provide a large surface area to volume ratio; thus, they can be used for various diseases, including cardiovascular diseases, cancer, bacterial infections, and diabetes. Nanoparticles play a crucial role in therapy as they can enhance the accumulation and release of pharmacological agents, improve targeted delivery and ultimately decrease the intensity of drug side effects. In this review, we discussthe types of nanomaterials that have various biomedical applications. Biomolecules that are often conjugated with nanoparticles are proteins, peptides, DNA, and lipids, which can enhance biocompatibility, stability, and solubility. In this review, we focus on bioconjugation and nanoparticles and also discuss different types of nanoparticles including micelles, liposomes, carbon nanotubes, nanospheres, dendrimers, quantum dots, and metallic nanoparticles and their crucial role in various diseases and clinical applications. Additionally, we review the use of nanomaterials for bio-imaging, drug delivery, biosensing tissue engineering, medical devices, and immunoassays. Understandingthe characteristics and properties of nanoparticles and their interactions with the biological system can help us to develop novel strategies for the treatment, prevention, and diagnosis of many diseases including cancer, pulmonary diseases, etc. In this present review, the importance of various kinds of nanoparticles and their biomedical applications are discussed in much detail.

Recent Advances in the Local Drug Delivery Systems for Improvement of Anticancer Therapy

The conventional anticancer chemotherapies not only cause serious toxic effects, but also produce resistance in tumor cells exposed to long-term therapy. Usually, the killing of metastasized cancer cells requires long-term therapy with higher drug doses, because the cancer cells develop resistance due to the induction of poly-glycoproteins (P-gps) that act as a transmembrane efflux pump to transport drugs out of the cells. During the last few decades, scientists have been exploring new anticancer drug delivery systems such as microencapsulation, hydrogels, and nanotubes to improve bioavailability, reduce drug-dose requirement, decrease multiple drug resistance, and to save normal cells as non-specific targets. Hopefully, the development of novel drug delivery vehicles (nanotubes, liposomes, supramolecules, hydrogels, and micelles) will assist to deliver drug molecules at the specific target site and reduce the undesirable side effects of anticancer therapies in humans. Nanoparticles and lipid formulations are also designed to deliver small drug payload at the desired tumor cell sites for their anticancer actions. This review will focus on the recent advances in the drug delivery systems, and their application in treating different cancer types in humans.

Pulmonary toxicity, cytotoxicity, and genotoxicity of submicron-diameter carbon fibers with different diameters and lengths

Submicron-diameter carbon fibers (SCFs) are a type of fine-diameter fibrous carbon material that can be used in various applications. To accelerate their practical application, a hazard assessment of SCFs must be undertaken. This study demonstrated the pulmonary toxicity, cytotoxicity, and genotoxicity of three types of SCFs with different diameters and lengths. The average diameter and length of SCFs were 259.2 nm and 11.7 μm in SCF1 suspensions, 248.5 nm and 6.7 μm in SCF2 suspensions, and 183.0 nm and 13.7 μm in SCF3 suspensions, respectively. The results of pulmonary inflammation and recovery following intratracheal instillation with SCFs at doses of 0.25, 0.5, or 1.0 mg/kg showed that the pulmonary toxicity of SCFs was SCF3 > SCF1 > SCF2. These results suggest that SCF diameter and length are most likely important contributing factors associated with lung SCF clearance, pulmonary inflammation, and recovery. Furthermore, SCFs are less pulmonary toxic than bent multi-walled carbon nanotubes. Cell viability, pro-inflammatory cytokine and intracellular reactive oxygen species productions, morphological changes, gene expression profiling in NR8383 rat alveolar macrophage cells showed that the cytotoxic potency of SCFs is: SCF3 > SCF1 > SCF2. These results showed that SCFs with small diameters had high cytotoxicity, and SCFs with short lengths had low cytotoxicity. We conclude that pulmonary toxicity and cytotoxicity are associated with the diameter and length distributions of SCFs. In addition, a standard battery for genotoxicity testing, namely the Ames test, an in vitro chromosomal aberration test, and a mammalian erythrocyte micronucleus test, demonstrated that the three types of SCFs did not induce genotoxicity. Our findings provide new evidence for evaluating the potential toxicity of not only SCFs used in this study but also various SCFs which differ depending on the manufacturing processes or physicochemical properties.

Toxicology of Nanoparticles in Drug Delivery

Nanoparticles have revolutionized biomedicine especially in the field of drug delivery due to their intriguing properties such as systemic stability, level of solubility, and target site specificity. It can, however, be both beneficial and damaging depending on the properties in different environments, thus highlighting the importance of nanotoxicology studies before use in humans. Different types of nanoparticles have been used in drug delivery, and this review summarizes the recent toxicity studies of these nanoparticles. The toxicological evaluation of three widely used nanoparticles in drug delivery that are metal, lipid, and protein nanoparticles has been discussed in detail. Studies have recorded several toxic effects of various nanoparticles such as metal-based nanoparticles have been linked to increased oxidative stress and have the potential to infiltrate the cell nucleus and protein-based nanoparticles have been observed to have hepatotoxicity and nephrotoxicity as their adverse effects. Considering the increasing application of nanoparticles in drug delivery and the growing concerns of regulatory authorities regarding the toxicity of nanocarriers in living organisms, it requires urgent attention to identify the gap in toxicity studies. The review highlights the gap in toxicity studies and potential focus areas to overcome the existing challenges.

Carbon Nanotubes: Current Perspectives on Diverse Applications in Targeted Drug Delivery and Therapies

Current discoveries as well as research findings on various types of carbon nanostructures have inspired research into their utilization in a number of fields. These carbon nanostructures offer uses in pharmacy, medicine and different therapies. One such unique carbon nanostructure includes carbon nanotubes (CNTs), which are one-dimensional allotropes of carbon nanostructure that can have a length-to-diameter ratio greater than 1,000,000. After their discovery, CNTs have drawn extensive research attention due to their excellent material properties. Their physical, chemical and electronic properties are excellent and their composites provide great possibilities for enormous nanometer applications. The current study provides a systematic review based on prior literature review and data gathered from various sources. The various research studies from many research labs and organizations were systematically retrieved, collected, compiled and written. The entire collection and compilation of this review concluded the use of CNT approaches and their efficacy and safety for the treatment of various diseases such as brain tumors or cancer via nanotechnology-based drug delivery, phototherapy, gene therapy, antiviral therapy, antifungal therapy, antibacterial therapy and other biomedical applications. The current review covers diverse applications of CNTs in designing a range of targeted drug delivery systems and application for various therapies. It concludes with a discussion on how CNTs based medicines can expand in the future.

An Overview of Antimicrobial Properties of Carbon Nanotubes-Based Nanocomposites

The development of carbon-based nanomaterials has extensively facilitated new discoveries in various fields. Carbon nanotube-based nanocomposites (CNT-based nanocomposites) have lately recognized as promising biomaterials for a wide range of biomedical applications due to their unique electronic, mechanical, and biological properties. Nanocomposite materials such as silver nanoparticles (AgNPs), polymers, biomolecules, enzymes, and peptides have been reported in many studies, possess a broad range of antibacterial activity when incorporated with carbon nanotubes (CNTs). It is crucial to understand the mechanism which governs the antimicrobial activity of these CNT-based nanocomposite materials, including the decoupling individual and synergistic effects on the cells. In this review, the interaction behavior between microorganisms and different types of CNT-based nanocomposites is summarized to understand the respective antimicrobial performance in different conditions. Besides, the current development stage of CNT-based nanocomposite materials, the technical challenges faced, and the exceptional prospect of implementing potential antimicrobial CNT-based nanocomposite materials are also discussed.

Utilizing literature-based rodent toxicology data to derive potency estimates for quantitative risk assessment

Evaluating the potential occupational health risk of engineered nanomaterials is an ongoing need. The objective of this meta-analysis, which consisted of 36 studies containing 86 materials, was to assess the availability of published in vivo rodent pulmonary toxicity data for a variety of nanoscale and microscale materials and to derive potency estimates via benchmark dose modeling. Additionally, the potency estimates based on particle mass lung dose associated with acute pulmonary inflammation were used to group materials based on toxicity. The commonalities among the physicochemical properties of the materials in each group were also explored. This exploration found that a material's potency tended to be associated primarily with the material class based on chemical composition and form (e.g. carbon nanotubes, TiO₂, ZnO) rather than with particular physicochemical properties. Limitations in the data available precluded a more extensive analysis of these associations. Issues such as data reporting and appropriate experimental design for use in quantitative risk assessment are the main reasons publications were excluded from these analyses and are discussed.

Comparative assessments of the biodistribution and toxicity of oxidized single-walled carbon nanotubes dispersed with two different reagents after intravenous injection

The present study compared the effects of two commonly-used dispersants, bovine serum albumin (BSA) and polyethylene glycol (PEG), on the biodistribution and toxicity of oxidized super-growth single-wall carbon nanotubes (oxSG) injected intravenously into mice over 3 months. About 1-2% of the injected dose (ID) of oxSG dispersed in BSA (oxSG-BSA) was present in the lungs at all time points. By contrast, about 15% of the ID of oxSG dispersed in PEG (oxSG-PEG) was present in the lungs at 1 day (D1), with accumulation decreasing to about 5% of the ID at 90 days (D90). About 70-80% of the IDs of both oxSG-BSA and oxSG-PEG were present in the liver at D1; by D90, about 15% of the IDs were cleared slowly (oxSG-BSA) or rapidly (oxSG-PEG). In the spleen, about 7% of the IDs of both oxSG-BSA and oxSG-PEG were present at all time points. The toxicities of oxSG-BSA and oxSG-PEG were comparable: no obvious signs of inflammation were observed on histological assessments of the lungs, liver, and spleen and on measurements of cytokine activity in blood plasma and tissue lysates. Concentrations of aspartate transaminase slightly increased at some time points in blood plasma, suggesting that oxSG-BSA and oxSG-PEG were slightly hepatoxic. Taken together, these results indicated that the dispersants had limited effect on the biodistribution and toxicity of oxSGs.

Current understanding of nanoparticle toxicity mechanisms and interactions with biological systems

Nanotechnology is an emerging science involving the manipulation of matter on the nanometer scale.

Inhaled multi-walled carbon nanotubes differently modulate global gene and protein expression in rat lungs

Inhalation of multi-walled carbon nanotubes (MWCNTs) induces lung inflammation. Depending on industrial applications, CNTs with different physicochemical characteristics are produced and workers can potentially be exposed. This raises concerns about the long-term health effects of these nanomaterials. Because of the wide variety of MWCNTs, it is essential to study the toxicological effects of CNTs of various shapes and to better understand the impact physical and chemical properties have on their toxicity. In this study, rats were exposed by nose-only to two pristine MWCNTs with different morphologies: the long and thick NM-401 or the short and thin NM-403. After four weeks of inhalation, animals were euthanized at four different times during the recovery period: three days (short-term), 30 and 90 days (intermediate-term) and 180 days (long-term). Analyses of the transcriptome in the whole lung and the proteome in the bronchoalveolar lavage fluid of exposed animals were performed to understand the MWCNT underlying mechanisms of toxicity. Following inhalation of NM-401, we observed a dose-dependent increase in the number of differentially expressed genes and proteins, whereas there is no clear difference between the two concentrations of NM-403. After NM-403 inhalation, the number of differentially expressed genes and proteins varied less between the four post-exposure times compared to NM-401, which supports the postulation of a persistent effect of this type of CNT. Our toxicogenomics approaches give insights into the different toxicological profile following MWCNT exposure.

Millimeter-Deep Detection of Single Shortwave-Infrared-Emitting Polymer Dots through Turbid Media

Fluorescence imaging at longer wavelengths, especially in the shortwave-infrared (SWIR: 1000-1700 nm) region, leads to a substantial decrease in light attenuation, scattering, and background autofluorescence, thereby enabling enhanced penetration into biological tissues. The limited selection of fluorescent probes is a major bottleneck in SWIR fluorescence imaging. Here, we develop SWIR-emitting nanoparticles composed of donor-acceptor-type conjugated polymers. The bright SWIR fluorescence of the polymer dots (primarily attributable to their large absorption cross-section and high fluorescence saturation intensity (as high as 113 kW·cm^-2)) enables the unprecedented detection of single particles as small as 14 nm through millimeter-thick turbid media. Unlike most SWIR-emitting nanomaterials, which have an excited-state lifetime in the range of microseconds to milliseconds, our polymer dots exhibit a subnanosecond excited-state lifetime. These characteristics enable us to demonstrate new time-gated single-particle imaging with a high signal-to-background ratio. These findings expand the range of potential applications of single-particle deep-tissue imaging.

Single-Walled Carbon Nanotubes Attenuate Cytotoxic and Oxidative Stress Response of Pb in Human Lung Epithelial (A549) Cells

Combined exposure of single-walled carbon nanotubes (SWCNTs) and trace metal lead (Pb) in ambient air is unavoidable. Most of the previous studies on the toxicity of SWCNTs and Pb have been conducted individually. There is a scarcity of information on the combined toxicity of SWCNTs and Pb in human cells. This work was designed to explore the combined effects of SWCNTs and Pb in human lung epithelial (A549) cells. SWCNTs were prepared through the plasma-enhanced vapor deposition technique. Prepared SWCNTs were characterized by x-ray diffraction, x-ray photoelectron spectroscopy, scanning electron microscopy, and dynamic light scattering. We observed that SWCNTs up to a concentration of 100 µg/mL was safe, while Pb induced dose-dependent (5-100 µg/mL) cytotoxicity in A549 cells. Importantly, cytotoxicity, cell cycle arrest, mitochondrial membrane potential depletion, lipid peroxidation, and induction of caspase-3 and -9 enzymes following Pb exposure (50 µg/mL for 24 h) were efficiently attenuated by the co-exposure of SWCNTs (10 µg/mL for 24 h). Furthermore, generation of Pb-induced pro-oxidants (reactive oxygen species and hydrogen peroxide) and the reduction of antioxidants (antioxidant enzymes and glutathione) were also mitigated by the co-exposure of SWCNTs. Inductively coupled plasma-mass spectrometry results suggest that the adsorption of Pb on the surface of SWCNTs could attenuate the bioavailability and toxicity of Pb in A549 cells. Our data warrant further research on the combined effects of SWCNTs and Pb in animal models.

Hydroxyl functionalized multi-walled carbon nanotubes modulate immune responses without increasing 2009 pandemic influenza A/H1N1 virus titers in infected mice

Growing use of carbon nanotubes (CNTs) have garnered concerns regarding their association with adverse health effects. Few studies have probed how CNTs affect a host's susceptibility to pathogens, particularly respiratory viruses. We reported that exposure of lung cells and mice to pristine single-walled CNTs (SWCNTs) leads to significantly increased influenza virus H1N1 strain A/Mexico/4108/2009 (IAV) titers in concert with repressed antiviral immune responses. In the present study, we investigated if hydroxylated multi-walled CNTs (MWCNTs), would result in similar outcomes. C57BL/6 mice were exposed to 20 μg MWCNTs on day 0 and IAV on day 3 and samples were collected on day 7. We investigated pathological changes, viral titers, immune-related gene expression in lung tissue, and quantified differential cell counts and cytokine and chemokine levels in bronchoalveolar lavage fluid. MWCNTs alone caused mild inflammation with no apparent changes in immune markers whereas IAV alone presented typical infection-associated inflammation, pathology, and titers. The co-exposure (MWCNTs + IAV) did not alter titers or immune cell profiles compared to the IAV only but increased concentrations of IL-1β, TNFα, GM-CSF, KC, MIPs, and RANTES and inhibited mRNA expression of Tlr3, Rig-i, Mda5, and Ifit2. Our findings suggest MWCNTs modulate immune responses to IAV with no effect on the viral titer and modest pulmonary injury, a result different from those reported for SWCNT exposures. This is the first study to show that MWCNTs modify cytokine and chemokine responses that control aspects of host defenses which may play a greater role in mitigating IAV infections.

Nanotechnology-based Drug Delivery, Metabolism and Toxicity

BACKGROUND

Nanoparticles (NPs) are being used extensively owing to their increased surface area, targeted delivery and enhanced retention. NPs have the potential to be used in many disease conditions. Despite widespread use, their toxicity and clinical safety still remain a major concern.

OBJECTIVE

The purpose of this study was to explore the metabolism and toxicological effects of nanotherapeutics.

METHODS

Comprehensive, time-bound literature search was done covering the period from 2010 till date. The primary focus was on the metabolism of NP including their adsorption, degradation, clearance, and bio-persistence. This review also focuses on updated investigations on NPs with respect to their toxic effects on various in vitro and in vivo experimental models.

RESULTS

Nanotechnology is a thriving field of biomedical research and an efficient drug delivery system. Further their applications are under investigation for diagnosis of disease and as medical devices.

CONCLUSION

The toxicity of NPs is a major concern in the application of NPs as therapeutics. Studies addressing metabolism, side-effects and safety of NPs are desirable to gain maximum benefits of nanotherapeutics.

Microenvironmental Alterations in Carbon Nanotube-Induced Lung Inflammation and Fibrosis

Carbon nanotube (CNT)-induced pulmonary inflammation and fibrosis have been intensively observed and characterized in numerous animal studies in the past decade. Remarkably, CNT-induced fibrotic lesions highly resemble some human fibrotic lung diseases, such as IPF and pneumoconiosis, regarding disease development and pathological features. This notion leads to a serious concern over the health impact of CNTs in exposed human populations, considering the rapidly expanding production of CNT materials for diverse industrial and commercial applications, and meanwhile provides the rationale for exploring CNT-induced pathologic effects in the lung. Accumulating mechanistic understanding of CNT lung pathology at the systemic, cellular, and molecular levels has demonstrated the potential of using CNT-exposed animals as a new disease model for the studies on inflammation, fibrosis, and the interactions between these two disease states. Tissue microenvironment plays critical roles in maintaining homeostasis and physiological functions of organ systems. When aberrant microenvironment forms under intrinsic or extrinsic stimulation, tissue abnormality, organ dysfunction, and pathological outcomes are induced, resulting in disease development. In this article, the cellular and molecular alterations that are induced in tissue microenvironment and implicated in the initiation and progression of inflammation and fibrosis in CNT-exposed lungs, including effector cells, soluble mediators, and functional events exemplified by cell differentiation and extracellular matrix (ECM) modification, are summarized and discussed. This analysis would provide new insights into the mechanistic understanding of lung inflammation and fibrosis induced by CNTs, as well as the development of CNT-exposed animals as a new model for human lung diseases.

Genes expression profiling of alveolar macrophages exposed to non-functionalized, anionic and cationic multi-walled carbon nanotubes shows three different mechanisms of toxicity

Functionalized multi-walled carbon nanotubes (MWCNT) have become the focus of increased research interest, particularly in their application as tools in different areas, such as the biomedical field. Despite the benefits associated with functionalization of MWCNT, particularly in overcoming issues relating to solubility, several studies have demonstrated that these functionalized nanoparticles display different toxicity profiles. For this study, we aim to compare NR8383 cells responses to three well-characterized MWCNT with varying functional groups. This study employed cytotoxicity assays, transcriptomics and proteomics to assess their toxicity using NR8383 rat alveolar macrophages as an in vitro model. The study findings indicated that all MWCNT altered ribosomal protein translation, cytoskeleton arrangement and induced pro-inflammatory response. Only functionalized MWCNT alter mTOR signaling pathway in conjunction with increased Lamtor gene expression. Furthermore, the type of functionalization was also important, with cationic MWCNT activating the transcription factor EB and inducing autophagy while the anionic MWCNT altering eukaryotic translation initiation factor 4 (EIF4) and phosphoprotein 70 ribosomal protein S6 kinase (p70S6K) signaling pathway as well as upregulation Tlr2 gene expression. This study proposes that MWCNT toxicity mechanisms are functionalization dependent and provides evidence that inflammatory response is a key event of carbon nanotubes toxicity.

Nanomaterials and Their Negative Effects on Human Health

Mesostructured silica, dendrimers, and allotropes of carbon were exhaustively used in biomedical, cosmetics, semiconductors, and food industry applications. Considering the huge prospect of nanomaterials, their potential hazards on exposure to humans and their related ecotoxicological effects needs to be summarized. Nanoparticles with size below 100 nm could pass into the lung and then to blood through inhalation, ingestion, and skin contact. As nanotechnology innovation is expected to achieve $ 2231 million by 2025, humans will be exposed ever increasingly in day-to-day life and in industries. In this review, the latest synthetic methodology of silica, dendrimers, and CNTs, their biological applications (in vitro and in vivo) related to toxicity were discussed. In terms of structured silica, the toxic and non-toxic effect induced by specific templates (cetylpyridinium bromide, cetyltrimethylammonium bromide, dipalmitoylphosphatidylcholine, C16L-tryptophan, C16-L-histidine, and C16-L-poline) that are used to generate mesoporous silica, silica nanoparticle sizes (25, 50, 60, 115, and 500 nm), and silane functionalization (NH₂ and COOH) were discussed. The recent applications of different generations (G3, G4, G5, and G6) of amphiphilic Janus dendrimers were discussed along with toxicity effect of different charged dendrimers (cationic and anionic) and effect of PEGylation. Recent synthesis, advantages, and disadvantages of carbon nanotubes (CNTs) were presented for structures like single walled carbon nanotubes (SWCNTs) and multiwalled carbon nanotubes (MWCNTs). The influence of diameter of SWCNTs (linear and short), thickness (thin and thick), effect of oxidation, metal oxide species (TiO₂, Fe, and Au), and biocompatible polymers (polyethylene glycol, bisphosphonate, and alendronate) were shown in relation to molecular pathways in animal cells.

Screening of preservatives and evaluation of sterilized cellulose nanofibers for toxicity studies

OBJECTIVES

The aim of this study is to establish a sterilization method for cellulose nanofibers (CNFs) dispersions that uses multiple preservatives with different hydrophilicities without affecting the physical and chemical properties of CNFs, and to provide useful information for sample preparation in future toxicity study of CNFs.

METHODS

Various preservatives were added to the phosphorylated CNF dispersions, endotoxin level and the numbers of bacteria and fungi in the CNF dispersion were analyzed. The pH values and viscosity of sterilized CNF dispersions were compared with those of control and autoclaved CNF dispersions.

RESULTS

Phosphorylated CNF dispersions at a concentration of 2.0 mg/mL or lower and the addition of 10 µg/mL benzalkonium chloride alone or 250 µg/mL methyl parahydroxybenzoate and 250 µg/mL propyl parahydroxybenzoate in combination can sterilize CNF dispersions without changing the physical and chemical properties of CNFs.

CONCLUSIONS

We developed sterilization method for CNF dispersions that uses multiple preservatives with different hydrophilicities without affecting the physical and chemical properties of CNFs. This sterilization method for CNFs dispersions can be applied to the safety assessment of CNF with different physicochemical properties in the future.

Toxicity of Carbon Nanotubes as Anti-Tumor Drug Carriers

Nanoparticle drug formulations have enormous application prospects owing to achievement of targeted and sustained release drug delivery, improvement in drug solubility and reduction of adverse drug reactions. Recently, a variety of efficient drug nanometer carriers have been developed, among which carbon nanotubes (CNT) have been increasingly utilized in the field of cancer therapy. However, these nanotubes exert various toxic effects on the body due to their unique physical and chemical properties. CNT-induced toxicity is related to surface modification, degree of aggregation in vivo, and nanoparticle concentration. This review has focused on the potential toxic effects of CNTs utilized as anti-tumor drug carriers. The main modes by which CNTs enter target sites, the toxicity expressive types and the factors affecting toxicity are discussed.

Single-Walled Carbon Nanotube-Assisted Antibiotic Delivery and Imaging in S. epidermidis Strains Addressing Antibiotic Resistance

Although conventional antibiotics have evolved as a staple of modern medicine, increasing antibiotic resistance and the lack of antibiotic efficacy against new bacterial threats is becoming a major medical threat. In this work, we employ single-walled carbon nanotubes (SWCNTs) known to deliver and track therapeutics in mammalian cells via intrinsic near-infrared fluorescence as carriers enhancing antibacterial delivery of doxycycline and methicillin. SWCNTs dispersed in water by antibiotics without the use of toxic bile salt surfactants facilitate efficacy enhancement for both antibiotics against Staphylococcus epidermidis strain showing minimal sensitivity to methicillin. Doxycycline to which the strain did not show resistance in complex with SWCNTs provides only minor increase in efficacy, whereas the SWCNTs/methicillin complex yields up to 40-fold efficacy enhancement over antibiotics alone, suggesting that SWCNT-assisted delivery may circumvent antibiotic resistance in that bacterial strain. At the same time SWCNT/antibiotic formulations appear to be less toxic to mammalian cells than antibiotics alone suggesting that nanomaterial platforms may not restrict potential biomedical applications. The improvement in antibacterial performance with SWCNT delivery is tested via 3 independent assays-colony count, MIC (Minimal Inhibitory Concentration) turbidity and disk diffusion, with the statistical significance of the latter verified by ANOVA and Dunnett's method. The potential mechanism of action is attributed to SWCNT interactions with bacterial cell wall and adherence to the membrane, as substantial association of SWCNT with bacteria is observed-the near-infrared fluorescence microscopy of treated bacteria shows localization of SWCNT fluorescence in bacterial clusters, scanning electron microscopy verifies SWCNT association with bacterial surface, whereas transmission electron microscopy shows individual SWCNT penetration into bacterial cell wall. This work characterizes SWCNTs as novel advantageous antibiotic delivery/imaging agents having the potential to address antibiotic resistance.

Cellular Toxicity and Immunological Effects of Carbon-based Nanomaterials

BACKGROUND

Carbon nanomaterials are a growing family of materials featuring unique physicochemical properties, and their widespread application is accompanied by increasing human exposure.

MAIN BODY

Considerable efforts have been made to characterize the potential toxicity of carbon nanomaterials in vitro and in vivo. Many studies have reported various toxicology profiles of carbon nanomaterials. The different results of the cytotoxicity of the carbon-based materials might be related to the differences in the physicochemical properties or structures of carbon nanomaterials, types of target cells and methods of particle dispersion, etc. The reported cytotoxicity effects mainly included reactive oxygen species generation, DNA damage, lysosomal damage, mitochondrial dysfunction and eventual cell death via apoptosis or necrosis. Despite the cellular toxicity, the immunological effects of the carbon-based nanomaterials, such as the pulmonary macrophage activation and inflammation induced by carbon nanomaterials, have been thoroughly studied. The roles of carbon nanomaterials in activating different immune cells or inducing immunosuppression have also been addressed.

CONCLUSION

Here, we provide a review of the latest research findings on the toxicological profiles of carbon-based nanomaterials, highlighting both the cellular toxicities and immunological effects of carbon nanomaterials. This review provides information on the overall status, trends, and research needs for toxicological studies of carbon nanomaterials.

Effect of polyethylene glycol surface charge functionalization of SWCNT on the in vitro and in vivo nanotoxicity and biodistribution monitored noninvasively using MRI

The current study evaluated in vitro and in vivo toxicity of carboxyl or amine polyethylene glycol (PEG) surface functionalization of single-walled carbon nanotubes (SWCNTs). Assessments of cytotoxicity, genotoxicity, immunotoxicity, and oxidative stress were performed in vitro and in vivo (in a 1-month follow-up study). The SWCNT biodistribution was investigated using noninvasive magnetic resonance imaging (MRI). Results confirmed the enhanced biocompatibility of PEG-functionalized SWCNTs compared to non-functionalized materials with significant decreases (p < 0.05) in the percentage of cell viability and increases in ROS generation, mitochondrial membrane potential, cell apoptosis, oxidative stress generation, and oxidative DNA damage in vitro. PEG-functionalized SWCNTs with amine terminals were found to induce prominent increases in ROS generation, mitochondrial membrane potential, and oxidative stress compared to carboxy functionalization. No significant difference in the biodistribution of either functionalized SWCNTs was observed in MRI. In vivo assessments revealed a statistically significant increase (p < 0.05) in oxidative stress as early as 24 h in serum and liver; however, all values normalized at 2 weeks' investigation time point. DNA damage was minimal with either PEG-COOH or PEG-NH₂ functionalized SWCNTs after 2 weeks' exposure. The negatively charged SWCNTs caused lesser DNA damage compared to positively charged samples. Carboxy-functionalized SWCNTs did not cause substantial changes in inflammatory mediators and were found to be significantly safer than non-functionalized SWCNTs and may pave the way for novel biomedical applications in cancer diagnosis and therapy.

Biological Response to Carbon-Family Nanomaterials: Interactions at the Nano-Bio Interface

During the last few decades, several studies have suggested that carbon-based nanomaterials, owing to their unique properties, could act as promising candidates in biomedical engineering application. Wide-ranging research efforts have investigated the cellular and molecular responses to carbon-based nanomaterials at the nano-bio interfaces. In addition, a number of surface functionalization strategies have been introduced to improve their safety profile in the biological environment. The present review discusses the general principles of immunological responses to nanomaterials. Then, it explains essential physico-chemical properties of carbon-familynanomaterials, including carbon nanotubes (CNTs), graphene, fullerene, carbon quantum dots (CDs), diamond-like carbon (DLC), and mesoporous carbon biomaterials (MCNs), which significantly affect the immunological cellular and molecular responses at the nano-bio interface. The discussions also briefly highlight the recent studies that critically investigated the cellular and molecular responses to various carbon-based nanomaterials. It is expected that the most recent perspective strategies for improving the biological responses to carbon-based nanomaterials can revolutionize their functions in emerging biological applications.

Single wall and multiwall carbon nanotubes induce different toxicological responses in rat alveolar macrophages

Human exposure to airborne carbon nanotubes (CNT) is increasing because of their applications in different sectors; therefore, they constitute a biological hazard. Consequently, developing studies on CNT toxicity become a necessity. CNTs can have different properties in term of length, size and charge. Here, we compared the cellular effect of multiwall (MWCNTs) and single wall CNTs (SWCNTs). MWCNTs consist of multiple layers of graphene, while SWCNTs are monolayers. The effects of MWCNTs and SWCNTs were evaluated by the water-soluble tetrazolium salt cell proliferation assay on NR8383 cells, rat alveolar macrophage cell line (NR8383). After 24 hours of exposure, MWCNTs showed higher toxicity (50% inhibitory concentration [IC₅₀ ] = 3.2 cm² /cm² ) than SWCNTs (IC₅₀  = 44 cm² /cm² ). Only SWCNTs have induced NR8383 cells apoptosis as assayed by flow cytometry using the annexin V/IP staining test. The expression of genes involved in oxidative burst (Ncf1), inflammation (Nfκb, Tnf-α, Il-6 and Il-1β), mitochondrial damage (Opa) and apoptotic balance (Pdcd4, Bcl-2 and Casp-8) was determined. We found that MWCNT exposure predominantly induce inflammation, while SWCNTs induce apoptosis and impaired mitochondrial function. Our results clearly suggest that MWCNTs are ideal candidates for acute inflammation induction. In vivo studies are required to confirm this hypothesis. However, we conclude that toxicity of CNTs is dependent on their physical and chemical characteristics.

Smart nanocarrier-based drug delivery systems for cancer therapy and toxicity studies: A review

Nonspecific distribution and uncontrollable release of drugs in conventional drug delivery systems (CDDSs) have led to the development of smart nanocarrier-based drug delivery systems, which are also known as Smart Drug Delivery Systems (SDDSs). SDDSs can deliver drugs to the target sites with reduced dosage frequency and in a spatially controlled manner to mitigate the side effects experienced in CDDSs. Chemotherapy is widely used to treat cancer, which is the second leading cause of death worldwide. Site-specific drug delivery led to a keen interest in the SDDSs as an alternative to chemotherapy. Smart nanocarriers, nanoparticles used to carry drugs, are at the focus of SDDSs. A smart drug delivery system consists of smart nanocarriers, targeting mechanisms, and stimulus techniques. This review highlights the recent development of SDDSs for a number of smart nanocarriers, including liposomes, micelles, dendrimers, meso-porous silica nanoparticles, gold nanoparticles, super paramagnetic iron-oxide nanoparticles, carbon nanotubes, and quantum dots. The nanocarriers are described in terms of their structures, classification, synthesis and degree of smartness. Even though SDDSs feature a number of advantages over chemotherapy, there are major concerns about the toxicity of smart nanocarriers; therefore, a substantial study on the toxicity and biocompatibility of the nanocarriers has been reported. Finally, the challenges and future research scope in the field of SDDSs are also presented. It is expected that this review will be widely useful for those who have been seeking new research directions in this field and for those who are about to start their studies in smart nanocarrier-based drug delivery.

Flexible and Stretchable Bio-Integrated Electronics Based on Carbon Nanotube and Graphene

Scientific and engineering progress associated with increased interest in healthcare monitoring, therapy, and human-machine interfaces has rapidly accelerated the development of bio-integrated multifunctional devices. Recently, compensation for the cons of existing materials on electronics for health care systems has been provided by carbon-based nanomaterials. Due to their excellent mechanical and electrical properties, these materials provide benefits such as improved flexibility and stretchability for conformal integration with the soft, curvilinear surfaces of human tissues or organs, while maintaining their own unique functions. This review summarizes the most recent advanced biomedical devices and technologies based on two most popular carbon based materials, carbon nanotubes (CNTs) and graphene. In the beginning, we discuss the biocompatibility of CNTs and graphene by examining their cytotoxicity and/or detrimental effects on the human body for application to bioelectronics. Then, we scrutinize the various types of flexible and/or stretchable substrates that are integrated with CNTs and graphene for the construction of high-quality active electrode arrays and sensors. The convergence of these carbon-based materials and bioelectronics ensures scalability and cooperativity in various fields. Finally, future works with challenges are presented in bio-integrated electronic applications with these carbon-based materials.

Carbon nanotubes as antimicrobial agents for water disinfection and pathogen control

Waterborne diseases significantly affect human health and are responsible for high mortality rates worldwide. Antibiotics have been known for decades for treatment of bacterial strains and their overuse and irrational applications are causing increasing bacteria resistance. Therefore, there is a strong need to find alternative ways for efficient water disinfection and microbial control. Carbon nanotubes (CNTs) have demonstrated strong antimicrobial properties due to their remarkable structure. This paper reviews the antimicrobial properties of CNTs, discusses diverse mechanisms of action against microorganisms as well as their applicability for water disinfection and microbial control. Safety concerns, challenges of CNTs as antimicrobial agents and future opportunities for their application in the water remediation process are also highlighted.

Insight into the heterogeneous adsorption of humic acid fluorescent components on multi-walled carbon nanotubes by excitation-emission matrix and parallel factor analysis

The heterogeneous adsorption behavior of commercial humic acid (HA) on pristine and functionalized multi-walled carbon nanotubes (MWCNTs) was investigated by fluorescence excitation-emission matrix and parallel factor (EEM- PARAFAC) analysis. The kinetics, isotherms, thermodynamics and mechanisms of adsorption of HA fluorescent components onto MWCNTs were the focus of the present study. Three humic-like fluorescent components were distinguished, including one carboxylic-like fluorophore C1 (λ_ex/λ_em= (250, 310) nm/428nm), and two phenolic-like fluorophores, C2 (λ_ex/λ_em= (300, 460) nm/552nm) and C3 (λ_ex/λ_em= (270, 375) nm/520nm). The Lagergren pseudo-second-order model can be used to describe the adsorption kinetics of the HA fluorescent components. In addition, both the Freundlich and Langmuir models can be suitably employed to describe the adsorption of the HA fluorescent components onto MWCNTs with significantly high correlation coefficients (R²> 0.94, P< 0.05). The dissimilarity in the adsorption affinity (K_d) and nonlinear adsorption degree from the HA fluorescent components to MWCNTs was clearly observed. The adsorption mechanism suggested that the π-π electron donor-acceptor (EDA) interaction played an important role in the interaction between HA fluorescent components and the three MWCNTs. Furthermore, the values of the thermodynamic parameters, including the Gibbs free energy change (ΔG°), enthalpy change (ΔH°) and entropy change (ΔS°), showed that the adsorption of the HA fluorescent components on MWCNTs was spontaneous and exothermic.

Single-walled carbon nanotubes modulate pulmonary immune responses and increase pandemic influenza a virus titers in mice

Background

Numerous toxicological studies have focused on injury caused by exposure to single types of nanoparticles, but few have investigated how such exposures impact a host’s immune response to pathogen challenge. Few studies have shown that nanoparticles can alter a host’s response to pathogens (chiefly bacteria) but there is even less knowledge of the impact of such particles on viral infections. In this study, we performed experiments to investigate if exposure of mice to single-walled carbon nanotubes (SWCNT) alters immune mechanisms and viral titers following subsequent influenza A virus (IAV) infection.

Methods

Male C57BL/6 mice were exposed to 20 μg of SWCNT or control vehicle by intratracheal instillation followed by intranasal exposure to 3.2 × 10⁴ TCID₅₀ IAV or PBS after 3 days. On day 7 mice were euthanized and near-infrared fluorescence (NIRF) imaging was used to track SWCNT in lung tissues. Viral titers, histopathology, and mRNA expression of antiviral and inflammatory genes were measured in lung tissue. Differential cell counts and cytokine levels were quantified in bronchoalveolar lavage fluid (BALF).

Results

Viral titers showed a 63-fold increase in IAV in SWCNT + IAV exposed lungs compared to the IAV only exposure. Quantitation of immune cells in BALF indicated an increase of neutrophils in the IAV group and a mixed profile of lymphocytes and neutrophils in SWCNT + IAV treated mice. NIRF indicated SWCNT remained in the lung throughout the experiment and localized in the junctions of terminal bronchioles, alveolar ducts, and surrounding alveoli. The dual exposure exacerbated pulmonary inflammation and tissue lesions compared to SWCNT or IAV single exposures. IAV exposure increased several cytokine and chemokine levels in BALF, but greater levels of IL-4, IL-12 (P70), IP-10, MIP-1, MIP-1α, MIP-1β, and RANTES were evident in the SWCNT + IAV group. The expression of tlr3, ifnβ1, rantes, ifit2, ifit3, and il8 was induced by IAV alone but several anti-viral targets showed a repressed trend (ifits) with pre-exposure to SWCNT.

Conclusions

These findings reveal a pronounced effect of SWCNT on IAV infection in vivo as evidenced by exacerbated lung injury, increased viral titers and several cytokines/chemokines levels, and reduction of anti-viral gene expression. These results imply that SWCNT can increase susceptibility to respiratory viral infections as a novel mechanism of toxicity.

Electronic supplementary material

The online version of this article (10.1186/s12985-017-0909-z) contains supplementary material, which is available to authorized users.

A 104-week pulmonary toxicity assessment of long and short single-wall carbon nanotubes after a single intratracheal instillation in rats

We compared long-term pulmonary toxicities after a single intratracheal instillation of two types of dispersed single-wall carbon nanotubes (SWCNTs), namely, those with relatively long or short linear shapes with average lengths of 8.6 and 0.55 µm, respectively. Both types of SWCNTs were instilled intratracheally in male F344 rats at 0.2 or 1.0 mg/kg (long SWCNTs) or 1.0 mg/kg (short SWCNTs). Pulmonary responses were characterized at 26, 52 and 104 weeks after a single instillation. Inflammatory changes, test substance deposition, test substance engulfment by macrophages, and alveolar wall fibrosis were observed in the lungs of almost all test rats at 52 and 104 weeks after short nanotube instillation. The incidences of these changes were much lower in the long nanotube-treated groups. In almost all rats of the long nanotube-treated groups, fibrosis and epithelium loss in the terminal bronchiole with test substance deposition were observed. These bronchiolar changes were not observed after administering short nanotubes. Both bronchiolo-alveolar adenoma and carcinoma were found in the negative-control group, the high-dose long-nanotube group, and the short-nanotube group at 104 weeks post-instillation, although the incidences were not statistically different. The genotoxicity of the SWCNTs was also evaluated by performing in vivo comet assays with lung cells obtained 26 weeks post-instillation. No significant changes in the percent tail deoxyribonucleic acid were found in any group. These findings suggested that most long SWCNTs were deposited at the terminal bronchioles and that a considerable amount of short SWCNTs reached the alveolus, resulting in chronic inflammatory responses, but no genotoxicity in the lungs.

Length effects of single-walled carbon nanotubes on pulmonary toxicity after intratracheal instillation in rats

We aimed to evaluate the effects of the length of single-walled carbon nanotubes (SWCNTs) on pulmonary toxicity in rats. Each rat received a single intratracheal instillation of short (S-) (average length of 0.40 μm) or long (L-) (average length of 2.77 μm) SWCNTs at a dose of 1 mg/kg and was observed for the next 6 months. Neither S- nor L-SWCNTs affected clinical signs, body weight, or autopsy findings. An increase in lung weight was observed after instillation of S- or L-SWCNTs; however, lung weights were slightly higher in the rats that were administered the S-SWCNTs. Distinct differences in bronchoalveolar lavage fluid (BALF) composition were observed between the S- and L-SWCNT-treated rats as early as 7 days after the intratracheal instillations of the SWCNTs. The S-SWCNTs caused persistent lung injury and inflammation during the 6-month observational period. However, the L-SWCNTs induced minimal lung injury and inflammation. Although the S- and L-SWCNTs changed BALF parameters and histopathological features of the lung, the magnitudes of the changes observed after the S-SWCNT treatment were greater than the respective changes observed after the L-SWCNT treatment. These findings indicate that the severity of the pulmonary toxicity caused after intratracheal instillation of SWCNT depends on the length of the SWCNTs. It appears that shorter SWCNTs induce greater pulmonary toxicity than longer SWCNTs do.

Recent advances in green nanoparticulate systems for drug delivery: efficient delivery and safety concern

Nanotechnology manipulates therapeutic agents at the nanoscale for the development of nanomedicines. However, there are current concerns over nanomedicines, mainly related to the possible toxicity of nanomaterials used for health medications. Due to their small size, they can enter the human body more readily than larger sized particles. Green chemistry encompasses the green synthesis of drug-loaded nanoparticles by reducing the use of hazardous materials in the synthesis process, thus reducing the adverse health impacts of pharmaceutics. This would greatly expand their potential in biomedical treatments. This review highlights the potential risks of nanomedicine formulations to health, delivery routes of green nanomedicines, recent advances in the development of green nanoscale systems for biomedical applications and future perspectives for the green development of nanomedicines.

Long-term intravenous administration of carboxylated single-walled carbon nanotubes induces persistent accumulation in the lungs and pulmonary fibrosis via the nuclear factor-kappa B pathway

Numerous studies have demonstrated promising application of single-walled carbon nanotubes (SWNTs) in drug delivery, diagnosis, and targeted therapy. However, the adverse health effects resulting from intravenous injection of SWNTs are not completely understood. Studies have shown that levels of “pristine” or carboxylated carbon nanotubes are very high in mouse lungs after intravenous injection. We hypothesized that long-term and repeated intravenous administration of carboxylated SWNTs (c-SWNTs) can result in persistent accumulation and induce histopathologic changes in rat lungs. Here, c-SWNTs were administered repeatedly to rats via tail-vein injection for 90 days. Long-term intravenous injection of c-SWNTs caused sustained embolization in lung capillaries and granuloma formation. It also induced a persistent inflammatory response that was regulated by the nuclear factor-kappa B signaling pathway, and which resulted in pulmonary fibrogenesis. c-SWNTs trapped within lung capillaries traversed capillary walls and injured alveolar epithelial cells, thereby stimulating production of pro-inflammatory cytokines (tumor necrosis factor-alpha and interleukin-1 beta) and pro-fibrotic growth factors (transforming growth factor-beta 1). Protein levels of type-I and type-III collagens, matrix metalloproteinase-2, and the tissue inhibitor of metalloproteinase-2 were upregulated after intravenous exposure to c-SWNTs as determined by immunohistochemical assays and Western blotting, which suggested collagen deposition and remodeling of the extracellular matrix. These data suggest that chronic and cumulative toxicity of nanomaterials to organs with abundant capillaries should be assessed if such nanomaterials are applied via intravenous administration.

SWCNTs as novel theranostic nanocarriers for cancer diagnosis and therapy: towards safe translation to the clinics

With their unique physicochemical properties, single walled carbon nanotubes (SWCNTs) hold great promise for applications as drug delivery systems (DDS) for early and better diagnosis and therapy of cancer. While several in vitro and in vivo studies have validated their potential benefit, no SWCNT-based formulation has yet reached clinical trials. Towards prospective safe clinical applications, the main properties that were adopted to enhance the biocompatibility of SWCNTs were highlighted. Then, the recent progresses in the in vivo applications of SWCNTs as diagnostic nanoprobes using multimodality imaging techniques and as therapeutic nanocarriers delivering wide range of anticancer efficient drugs to tumors were reviewed. Finally, the efforts required for safe clinical applications of SWCNTs as DDS for cancer diagnosis and therapy were discussed.