Functionalised carbon nanotubes: From intracellular uptake and cell-related toxicity to systemic brain delivery

Nanomaterials for Cardiac Tissue Engineering

End stage heart failure is a major cause of death in the US. At present, organ transplant and left-ventricular assist devices remain the only viable treatments for these patients. Cardiac tissue engineering presents the possibility of a new option. Nanomaterials such as gold nanorods (AuNRs) and carbon nanotubes (CNTs) present unique properties that are beneficial for cardiac tissue engineering approaches. In particular, these nanomaterials can modulate electrical conductivity, hardness, and roughness of bulk materials to improve tissue functionality. Moreover, they can deliver bioactive cargo to affect cell phenotypes. This review covers recent advances in the use of nanomaterials for cardiac tissue engineering.

Poly(ethylene glycol) based nanotubes for tuneable drug delivery to glioblastoma multiforme

Glioblastoma multiforme (GBM) is the most aggressive type of malignant brain tumour, which is associated with a poor two-year survival rate and a high rate of fatal recurrence near the original tumour. Focal/local drug delivery devices hold promise for improving therapeutic outcomes for GBM by increasing drug concentrations locally at the tumour site, or by facilitating the use of potent anti-cancer drugs that are poorly permeable across the blood brain barrier (BBB). For inoperable tumours, stereotactic delivery to the tumour necessitates the development of nanoscale/microscale injectable drug delivery devices. Herein we assess the ability of a novel class of polymer nanotube (based on poly(ethylene glycol) (PEG)) to load doxorubicin (a mainstay breast cancer therapeutic with poor BBB permeability) and release it slowly. The drug loading properties of the PEG nanotubes could be tuned by varying the degree of carboxylic acid functionalisation and hence the capacity of the nanotubes to electrostatically bind and load doxorubicin. 70% of the drug was released over the first seven days followed by sustained drug release for the remaining two weeks tested. Unloaded PEG nanotubes showed no toxicity to any of the cell types analysed, whereas doxorubicin loaded nanotubes decreased GBM cell viability (C6, U-87 and U-251) in a dose dependent manner in 2D in vitro culture. Finally, doxorubicin loaded PEG nanotubes significantly reduced the viability of in vitro 3D GBM models whilst unloaded nanotubes showed no cytotoxicity. Taken together, these findings show that polymer nanotubes could be used to deliver alternative anti-cancer drugs for local therapeutic strategies against brain cancers.

Carbon nanotubes and their polymeric composites: the applications in tissue engineering

Carbon nanotubes (CNTs), with unique graphitic structure, superior mechanical, electrical, optical and biological properties, has attracted more and more interests in biomedical applications, including gene/drug delivery, bioimaging, biosensor and tissue engineering. In this review, we focus on the role of CNTs and their polymeric composites in tissue engineering applications, with emphasis on their usages in the nerve, cardiac and bone tissue regenerations. The intrinsic natures of CNTs including their physical and chemical properties are first introduced, explaining the structure effects on CNTs electrical conductivity and various functionalization of CNTs to improve their hydrophobic characteristics. Biosafety issues of CNTs are also discussed in detail including the potential reasons to induce the toxicity and their potential strategies to minimise the toxicity effects. Several processing strategies including solution-based processing, polymerization, melt-based processing and grafting methods are presented to show the 2D/3D construct formations using the polymeric composite containing CNTs. For the sake of improving mechanical, electrical and biological properties and minimising the potential toxicity effects, recent advances using polymer/CNT composite the tissue engineering applications are displayed and they are mainly used in the neural tissue (to improve electrical conductivity and biological properties), cardiac tissue (to improve electrical, elastic properties and biological properties) and bone tissue (to improve mechanical properties and biological properties). Current limitations of CNTs in the tissue engineering are discussed and the corresponded future prospective are also provided. Overall, this review indicates that CNTs are promising “next-generation” materials for future biomedical applications.

Carbon nanostructures: The drug and the delivery system for brain disorders

Neurodegenerative disorders and brain tumors are major pathological conditions affecting the brain. The delivery of therapeutic agents into the brain is not as easy as to other organs or systems. The presence of the blood-brain barrier (BBB) makes the drug delivery into the brain more complicated and challenging. Many techniques have been developed to overcome the difficulties with BBB and to achieve brain-targeted drug delivery. Incorporation of the drugs into nanocarriers capable to penetrate BBB is a simple technique. Different nanocarriers have been developed including polymeric nanoparticles, carbon nanoparticles, lipid-based nanoparticles, etc. Carbon nanostructures could make a superior position among them, because of their good biocompatibility and easy penetration of BBB. Carbon-family nanomaterials consist of different carbon-based structures including zero-dimensional fullerene, one-dimensional carbon nanotube, two-dimensional graphene, and some other related structures like carbon dots and nanodiamonds. They can be used as efficient carriers for drug delivery into the brain. Apart from the drug delivery applications, they can also be used as a central nervous system (CNS) therapeutic agent; some of the carbon nanostructures have neuroregenerative activity. Their influence on neuronal growth and anti-amyloid action is also interesting. This review focuses on different carbon nanostructures for brain-targeted drug delivery and their CNS activities. As a carrier and CNS therapeutic agent, carbon nanostructures can revolutionize the treatment of brain disorders.

Dendrimer-coated carbon nanotubes deliver dsRNA and increase the efficacy of gene knockdown in the red flour beetle Tribolium castaneum

In this study, the use of dendrimer-coated carbon nanotubes (CNTs) as a delivery vehicle for dsRNA was assessed in Tribolium castaneum. Exposure to low dosages of polyamidoamine dendrimer carbon nanotubes (PAMAM-CNTs) did not affect T. castaneum larval mortality. Expression of key apoptotic factors, Dronc (Tc12580), Dredd (Tcn-like, Tc014026) and Buffy, (Tcinhib apop1), which can act as toxicity indicators, were not altered in T. castaneum larvae following injection of PAMAM-CNTs. The level of knockdown of two target genes, α-tubulin and mitochondrial RNA polymerase (mtpol), were significantly increased when larvae were injected with double-stranded RNA bound to CNTs (PAMAM-CNT-dsRNA), compared to those injected with target dsRNA alone. PAMAM-CNTs were visualised in cellular vacuoles and in the cell nucleus. Increase occurrence of a blistered wing phenotype was found in a subset of PAMAM-CNT-dsRNA_αtub injected larvae, relative to the level seen in larvae injected with naked dsRNA_αtub alone. These results suggest that the use of functionalised CNTs for dsRNA delivery could increase the efficacy of RNA interference in insect pest species.

Enhancement of single-walled carbon nanotube accumulation in glioma cells exposed to low-strength electric field: Promising approach in cancer nanotherapy

The objective of the study is to determine the patterns of regulation of single-walled carbon nanotube accumulation, distribution, and agglomeration in glioma cells exposed to an external electric field. C6 glioma cells were treated with 5 μg/ml DNA wrapped single-walled carbon nanotubes and exposed to bi-phasic electric pulses (6.6 V/m, 200 Hz, pulse duration 1 ms). Nanotube accumulation was determined by Raman microspectroscopy and their intracellular local concentration was evaluated using the G-band intensity in Raman spectra of single-walled carbon nanotubes. It was revealed that the low-frequency and low-strength electric field stimulation of glioma cells exposed to single-walled carbon nanotubes led to facilitation and, thus, to amplification of nanotube accumulation inside the cells. The number of nanotubes in intracellular agglomerates increased from (28.8 ± 13.1) un./agglom. and (84.0 ± 28.7) un./agglom. in control samples to (60.6 ± 21.4) un./agglom. and (184.2 ± 53.4) un./agglom. for 1 h and 2 h stimulation, respectively. Thus, the tumor exposure to an external electric field makes it possible to more effectively regulate the accumulation and distribution of carbon nanotubes inside glioma cells allowing to reduce the applied therapeutic doses of carbon nanomaterial delivered anticancer drugs.

Naringenin-Functionalized Multi-Walled Carbon Nanotubes: A Potential Approach for Site-Specific Remote-Controlled Anticancer Delivery for the Treatment of Lung Cancer Cells

Multi-walled carbon nanotubes functionalized with naringenin have been developed as new drug carriers to improve the performance of lung cancer treatment. The nanocarrier was characterized by Transmission Electron Microscopy (TEM), Fourier-Transform Infrared Spectroscopy (FTIR), X-ray photoelectron spectroscopy, Raman Spectroscopy, and Differential Scanning Calorimetry (DSC). Drug release rates were determined in vitro by the dialysis method. The cytotoxic profile was evaluated using the MTT assay, against a human skin cell line (hFB) as a model for normal cells, and against an adenocarcinomic human alveolar basal epithelial (A569) cell line as a lung cancer in vitro model. The results demonstrated that the functionalization of carbon nanotubes with naringenin occurred by non-covalent interactions. The release profiles demonstrated a pH-responsive behavior, showing a prolonged release in the tumor pH environment. The naringenin-functionalized carbon nanotubes showed lower cytotoxicity on non-malignant cells (hFB) than free naringenin, with an improved anticancer effect on malignant lung cells (A549) as an in vitro model of lung cancer.

When polymers meet carbon nanostructures: expanding horizons in cancer therapy

The development of hybrid materials, which combine inorganic with organic materials, is receiving increasing attention by researchers. As a consequence of carbon nanostructures high chemical versatility, they exhibit enormous potential for new highly engineered multifunctional nanotherapeutic agents for cancer therapy. Whereas many groups are working on drug delivery systems for chemotherapy, the use of carbon nanohybrids for radiotherapy is rarely applied. Thus, nanotechnology offers a wide range of solutions to overcome the current obstacles of conventional chemo- and/or radiotherapies. Within this review, the structure and properties of carbon nanostructures (carbon nanotubes, nanographene oxide) functionalized preferentially with different types of polymers (synthetic, natural) are discussed. In short, synthesis approaches, toxicity investigations and anticancer efficacy of different carbon nanohybrids are described.

Surface modification of carbon nanotube with gelatin via mussel inspired method

Carbon nanotube (CNT) has aroused much attention in biomedical field. However, the cytotoxicity and aggregation are critical factors that affect the application of carbon nanotube (CNT). Herein, gelatin was grafted on the surface of CNT via mussel-inspired method. The gelatin modified CNT can disperse homogeneously in water. The in vitro test showed that gelatin modified CNT showed much better biocompatibility than the native CNT, which may improve its potential application in biomedical field.

The peculiar size and temperature dependence of water diffusion in carbon nanotubes studied with 2D NMR diffusion-relaxation D -T 2eff spectroscopy

It is well known that water inside hydrophobic nano-channels diffuses faster than bulk water. Recent theoretical studies have shown that this enhancement depends on the size of the hydrophobic nanochannels. However, experimental evidence of this dependence is lacking. Here, by combining two-dimensional nuclear magnetic resonance diffusion-relaxation ( D - T 2 e f f ) spectroscopy in the stray field of a superconducting magnet and molecular dynamics simulations, we analyze the size dependence of water dynamics inside Carbon Nanotubes (CNTs) of different diameters ( 1.1 - 6.0  nm), in the temperature range of 265 - 305  K. Depending on the CNT diameter, the nanotube water is shown to resolve in two or more tubular components acquiring different self-diffusion coefficients. Most notably, a favorable CNT diameter range ( 3.0 - 4.5  nm) is experimentally verified for the first time, in which water molecule dynamics at the center of the CNTs exhibits distinctly non-Arrhenius behavior, characterized by ultrafast diffusion and extraordinary fragility, a result of significant importance in the efforts to understand water behavior in hydrophobic nanochannels.

Functionalized Carbon Nanostructures Versus Drug Resistance: Promising Scenarios in Cancer Treatment

Carbon nanostructures (CN) are emerging valuable materials for the assembly of highly engineered multifunctional nanovehicles for cancer therapy, in particular for counteracting the insurgence of multi-drug resistance (MDR). In this regard, carbon nanotubes (CNT), graphene oxide (GO), and fullerenes (F) have been proposed as promising materials due to their superior physical, chemical, and biological features. The possibility to easily modify their surface, conferring tailored properties, allows different CN derivatives to be synthesized. Although many studies have explored this topic, a comprehensive review evaluating the beneficial use of functionalized CNT vs G or F is still missing. Within this paper, the most relevant examples of CN-based nanosystems proposed for MDR reversal are reviewed, taking into consideration the functionalization routes, as well as the biological mechanisms involved and the possible toxicity concerns. The main aim is to understand which functional CN represents the most promising strategy to be further investigated for overcoming MDR in cancer.

Novel Nanohybrids Based on Supramolecular Assemblies of Meso-tetrakis-(4-sulfonatophenyl) Porphyrin J-aggregates and Amine-Functionalized Carbon Nanotubes

The ability of multiwalled carbon nanotubes (MWCNTs) covalently functionalized with polyamine chains of different length (ethylenediamine, EDA and tetraethylenepentamine, EPA) to induce the J-aggregation of meso-tetrakis(4-sulfonatophenyl)porphyrin (TPPS) was investigated in different experimental conditions. Under mild acidic conditions, protonated amino groups allow for the assembly by electrostatic interaction with the diacid form of TPPS, leading to hybrid nanomaterials. The presence of only one pendant amino group for a chain in EDA does not lead to any aggregation, whereas EPA (with four amine groups for chain) is effective in inducing J-aggregation using different mixing protocols. These nanohybrids have been characterized through UV/Vis extinction, fluorescence emission, resonance light scattering and circular dichroism spectroscopy. Their morphology and chemical composition have been elucidated through transmission electron microscopy (TEM) and scanning transmission electron microscopy (STEM). TEM and STEM analysis evidence single or bundles of MWCNTs in contact with TPPS J-aggregates nanotubes. The nanohybrids are quite stable for days, even in aqueous solutions mimicking physiological medium (NaCl 0.15 M). This property, together with their peculiar optical features in the therapeutic window of visible spectrum, make them potentially useful for biomedical applications.

Safe Administration of Carbon Nanotubes by Intravenous Pathway in BALB/c Mice

Carbon nanotubes (CNTs) are nanomaterials with multiple possible uses as drug carriers or in nanovaccine development. However, the toxicity of CNTs administered intravenously in in vivo models has not been fully described to date. This work aimed to evaluate the toxic effect of pristine multi-walled CNTs (UP-CNTs), purified (P-CNTs), or CNTs functionalized with fluorescein isothiocyanate (FITC-CNTs) administered by intravenous injection in BALB/c mice. Biochemical and histopathological parameters were analyzed at 1, 14, 29, and 60 days post-exposure. Pristine CNTs were the most toxic nanoparticles in comparison with P-CNTs or FITC-CNTs, increasing serum AST (≈ 180%), ALT (≈ 300%), and LDH (≈ 200%) levels at one day post-exposure. The urea/creatinine ratio suggested pre-renal injury at the 14th day accompanied of extensive lesions in kidneys, lungs, and liver. Biochemical and histological findings in mice exposed to P-CNTs had not significant differences compared to the controls. A lower toxic effect was detected in animals exposed to FITC-CNTs which was attributable to FITC toxicity. These results demonstrate that the purification process of CNTs reduces in vivo toxicity, and that toxicity in functionalized CNTs is dependent on the functionalized compound. Therefore, P-CNTs are postulated as potential candidates for safe biomedical applications using an intravenous pathway.

Using macropinocytosis for intracellular delivery of therapeutic nucleic acids to tumour cells

Nucleic acids are a rapidly emerging therapeutic modality with the potential to become the third major drug modality alongside antibodies and small molecules. Owing to the unfavourable physico-chemical characteristics of nucleic acids, such as large size and negative charge, intracellular delivery remains a fundamental challenge to realizing this potential. Delivery technologies such as lipids, polymers and peptides have been used to facilitate delivery, with many of the most successful technologies using macropinocytosis to gain cellular entry; mostly by default rather than design. Fundamental knowledge of macropinocytosis is rapidly growing, presenting opportunities to better tailor design strategies to target this pathway. Furthermore, certain types of tumour cells have been observed to have high levels of macropinocytic activity and traffic cargo to favourable destinations within the cell for endosomal release, providing unique opportunities to further use this entry route for drug delivery. In this article, we review the delivery systems reported to be taken up by macropinocytosis and what is known about the mechanisms for regulating macropinocytosis in tumour cells. From this analysis, we identify new opportunities for exploiting this pathway for the intracellular delivery of nucleic acids to tumour cells. This article is part of the Theo Murphy meeting issue 'Macropinocytosis'.

PEG/PEI-functionalized single-walled carbon nanotubes as delivery carriers for doxorubicin: synthesis, characterization, and in vitro evaluation

Single-walled carbon nanotubes (SWCNTs) have attracted great interest regarding drug-delivery applications. However, their application has been limited by some inherent disadvantages. In this study, raw SWCNTs were purified with different oxidizing acids, and the resulting shortened CNTs were conjugated with poly(ethylene glycol) (PEG) and polyethylenimine (PEI). The different nanocarriers, that is, CNTs-COOH (CNTs), CNTs-PEG and CNTs-PEG-PEI, were systematically characterized and evaluated in terms of drug loading, in vitro release, cytotoxicity towards MCF-7 cells and cellular uptake. The results showed that all CNT carriers had a high drug loading capacity. In comparison with CNTs-COOH and CNTs-PEG, CNTs-PEG-PEI showed a more rapid drug release under acidic conditions and a higher antitumor activity. Furthermore, fluorescence detection and flow cytometry (FCM) analysis results indicated that the internalization into cells of CNTs-PEG-PEI was significantly enhanced, thus inducing tumor cell death through apoptosis more efficiently. The above series of benefits of CNTs-PEG-PEI may be attributed to their good dispersibility and comparably higher affinity to tumor cells due to the difunctionalization. In summary, the PEG- and PEI-conjugated CNTs may be used as novel nanocarriers and the findings will contribute to the rational design of multifunctional delivery vehicles for anticancer drugs.

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.

Balanced Th1/Th2 immune response induced by MSP1a functional motif coupled to multiwalled carbon nanotubes as anti-anaplasmosis vaccine in murine model

Anaplasmosis is one of the most prevalent tick-borne diseases of cattle caused by Anaplasma marginale. MSP1a surface protein has been shown to be involved in eliciting immunity to infected cattle. Carbon nanotubes (CNTs) has been increasingly highlighted due to their needle like structure, which contain multiple attachment sites for biomolecules and may interact with or cross biological membranes, increasing antigen availability to immune system. Here, we have successfully designed a nanocomplex of a synthetic peptide noncovalently attached to multiwalled CNT (MWCNT). Peptide comprising the core motif of the MSP1a was efficiently adsorb onto the nanoparticle surface. The MWCNT-Am1 nanocomplex exhibited high stability and good dispersibility and in vivo immunization showed high levels of IgG1 and IgG2a, followed by increased expression of pro-inflammatory and anti-inflammatory cytokines. This is a proof-of-concept of a nanovaccine that was able to generate a strong immune response compared to the common antigen-adjuvant vaccine without the nanoparticles.

Carbon nanotubes: An effective platform for biomedical electronics

Cylindrical fullerenes (or carbon nanotubes (CNTs)) have been extensively investigated as potential sensor platforms due to effective and practical manipulation of their physical and chemical properties by functionalization/doping with chemical groups suitable for novel nanocarrier systems. CNTs play a significant role in biomedical applications due to rapid development of synthetic methods, structural integration, surface area-controlled heteroatom doping, and electrical conductivity. This review article comprehensively summarized recent trends in biomedical science and technologies utilizing a promising nanomaterial of CNTs in disease diagnosis and therapeutics, based on their biocompatibility and significance in drug delivery, implants, and bio imaging. Biocompatibility of CNTs is essential for designing effective and practical electronic applications in the biomedical field particularly due to their growing potential in the delivery of anticancer agents. Furthermore, functionalized CNTs have been shown to exhibit advanced electrochemical properties, responsible for functioning of numerous oxidase and dehydrogenase based amperometric biosensors. Finally, faster signal transduction by CNTs allows charge transfer between underlying electrode and redox centres of biomolecules (enzymes).

Quantification of blood-brain barrier transport and neuronal toxicity of unlabelled multiwalled carbon nanotubes as a function of surface charge

Nanoparticles capable of penetrating the blood-brain barrier (BBB) will greatly advance the delivery of therapies against brain disorders. Carbon nanotubes hold great potential as delivery vehicles due to their high aspect-ratio and cell-penetrating ability. Studies have shown multiwalled carbon nanotubes (MWCNT) cross the BBB, however they have largely relied on labelling methods to track and quantify transport, or on individual electron microscopy images to qualitatively assess transcytosis. Therefore, new direct and quantitative methods, using well-defined and unlabelled MWCNT, are needed to compare BBB translocation of different MWCNT types. Using highly controlled anionic (-), cationic (+) and non-ionic (0) functionalized MWCNT (fMWCNT), we correlate UV-visible spectroscopy with quantitative transmission electron microscopy, quantified from c. 270 endothelial cells, to examine cellular uptake, BBB transport and neurotoxicity of unlabelled fMWCNT. Our results demonstrate that: (i) a large fraction of cationic and non-ionic, but not anionic fMWCNT become trapped at the luminal brain endothelial cell membrane; (ii) despite high cell association, fMWCNT uptake by brain endothelial cells is low (<1.5% ID) and does not correlate with BBB translocation, (iii) anionic fMWCNT have highest transport levels across an in vitro model of the human BBB compared to non-ionic or cationic nanotubes; and (iv) fMWCNT are not toxic to hippocampal neurons at relevant abluminal concentrations; however, fMWCNT charge has an effect on carbon nanotube neurotoxicity at higher fMWCNT concentrations. This quantitative combination of microscopy and spectroscopy, with cellular assays, provides a crucial strategy to predict brain penetration efficiency and neurotoxicity of unlabelled MWCNT and other nanoparticle technologies relevant to human health.

Vitamin K1 As A Potential Molecule For Reducing Single-Walled Carbon Nanotubes-Stimulated α-Synuclein Structural Changes And Cytotoxicity

Aims

Different kinds of vitamins can be used as promising candidates to mitigate the structural changes of proteins and associated cytotoxicity stimulated by NPs. Therefore, the structural changes of α-syn molecules and their associated cytotoxicity in the presence of SWCNTs either alone or co-incubated with vitamin K1 were studied by spectroscopic, bioinformatical, and cellular assays.

Methods

Intrinsic and ThT fluorescence, CD, and Congo red absorption spectroscopic approaches as well as TEM investigation, molecular docking, and molecular dynamics were used to explore the protective effect of vitamin K1 on the structural changes of α-syn induced by SWCNTs. The cytotoxicity of α-syn/SWCNTs co-incubated with vitamin K1 against SH-SY5Y cells was also carried out by MTT, LDH, and caspase-3 assays.

Results

Fluorescence spectroscopy showed that vitamin K1 has a significant effect in reducing SWCNT-induced fluorescence quenching and aggregation of α- syn. CD, Congo red adsorption, and TEM investigations determined that co-incubation of α- syn with vitamin K1 inhibited the propensity of α-syn into the structural changes and amorphous aggregation in the presence of SWCNT. Docking studies determined the occupation of preferred docked site of SWCNT by vitamin K1 on α- syn conformation. A molecular dynamics study also showed that vitamin K1 reduced the structural changes of α- syn induced by SWCNT. Cellular data exhibited that the cytotoxicity of α- syn co-incubated with vitamin K1 in the presence of SWCNTs is less than the outcomes obtained in the absence of the vitamin K1.

Conclusion

It may be concluded that vitamin K1 decreases the propensity of α- syn aggregation in the presence of SWCNTs and induction of cytotoxicity.

Multi-walled carbon nanotubes upregulate mitochondrial gene expression and trigger mitochondrial dysfunction in primary human bronchial epithelial cells

Nanomaterials are a relatively new class of materials that acquire novel properties based on their reduced size. While these materials have widespread use in consumer products and industrial applications, the potential health risks associated with exposure to them remain to be fully characterized. Carbon nanotubes are among the most widely used nanomaterials and have high potential for human exposure by inhalation. These nanomaterials are known to penetrate the cell membrane and interact with intracellular molecules, resulting in a multitude of documented effects, including oxidative stress, genotoxicity, impaired metabolism, and apoptosis. While the capacity for carbon nanotubes to damage nuclear DNA has been established, the effect of exposure on mitochondrial DNA (mtDNA) is relatively unexplored. In this study, we investigated the potential of multi-walled carbon nanotubes (MWCNTs) to impair mitochondrial gene expression and function in human bronchial epithelial cells (BECs). Primary BECs were exposed to sub-cytotoxic doses (up to 3 μg/ml) of MWCNTs for 5 d and assessed for changes in expression of all mitochondrial protein-coding genes, heteroplasmies, and insertion/deletion mutations (indels). Exposed cells were also measured for cytotoxicity, metabolic function, mitochondrial abundance, and mitophagy. We found that MWCNTs upregulated mitochondrial gene expression, while significantly decreasing oxygen consumption rate and mitochondrial abundance. Confocal microscopy revealed induction of mitophagy by 2 hours of exposure. Mitochondrial DNA heteroplasmy and insertion/deletion mutations were not significantly affected by any treatment. We conclude that carbon nanotubes cause mitochondrial dysfunction that leads to mitophagy in exposed BECs via a mechanism unrelated to its reported genotoxicity.

Nanoformulations for glioblastoma multiforme: a new hope for treatment

Glioblastoma multiforme (GBM) is the most common primary malignant brain tumor in adults, associated with a high mortality rate and a survival of between 12 and 15 months after diagnosis. Due to current treatment limitations involving surgery, radiotherapy and chemotherapy with temozolamide, there is a high rate of treatment failure and recurrence. To try to overcome these limitations nanotechnology has emerged as a novel alternative. Lipid, polymeric, silica and magnetic nanoparticles, among others, are being developed to improve GBM treatment and diagnosis. These nanoformulations have many advantages, including lower toxicity, biocompatibility and the ability to be directed toward the tumor. This article reviews the progress that have been made and the large variety of nanoparticles currently under study for GBM.

Antagonistic Interactions between Benzo[a]pyrene and Fullerene (C60) in Toxicological Response of Marine Mussels

This study aimed to assess the ecotoxicological effects of the interaction of fullerene (C60) and benzo[a]pyrene (B[a]P) on the marine mussel, Mytilus galloprovincialis. The uptake of nC60, B[a]P and mixtures of nC60 and B[a]P into tissues was confirmed by Gas Chromatography-Mass Spectrometry (GC-MS), Liquid Chromatography-High Resolution Mass Spectrometry (LC-HRMS) and Inductively Coupled Plasma Mass Spectrometer (ICP-MS). Biomarkers of DNA damage as well as proteomics analysis were applied to unravel the interactive effect of B[a]P and C60. Antagonistic responses were observed at the genotoxic and proteomic level. Differentially expressed proteins (DEPs) were only identified in the B[a]P single exposure and the B[a]P mixture exposure groups containing 1 mg/L of C60, the majority of which were downregulated (~52%). No DEPs were identified at any of the concentrations of nC60 (p < 0.05, 1% FDR). Using DEPs identified at a threshold of (p < 0.05; B[a]P and B[a]P mixture with nC60), gene ontology (GO) and Kyoto encyclopedia of genes and genomes (KEGG) pathway analysis indicated that these proteins were enriched with a broad spectrum of biological processes and pathways, including those broadly associated with protein processing, cellular processes and environmental information processing. Among those significantly enriched pathways, the ribosome was consistently the top enriched term irrespective of treatment or concentration and plays an important role as the site of biological protein synthesis and translation. Our results demonstrate the complex multi-modal response to environmental stressors in M. galloprovincialis.

Recent advances in graphene-based nanomaterials: properties, toxicity and applications in chemistry, biology and medicine

This review (with 239 refs.) summarizes the progress that has been made in applications of graphene-based nanomaterials (such as plain graphene, graphene oxides, doped graphene oxides, graphene quantums dots) in biosensing, imaging, drug delivery and diagnosis. Following an introduction into the field, a first large section covers the toxicity of graphene and its derivatives (with subsections on bacterial toxicity and tissue toxicity). The use of graphene-based nanomaterials in sensors is reviewed next, with subsections on electrochemical, FET-based, fluorescent, chemiluminescent and colorimetric sensors and probes. The large field of imaging is treated next, with subchapters on optical, PET-based, and magnetic resonance based methods. A concluding section summarizes the current status, addresses current challenges, and gives an outlook on potential future trends. Graphical Abstract Schematic presentation of the potential applications of graphene-based materials in life science and biomedicine, emphatically reflected in some vital areas such as DNA analysis, biological monitoring, drug delivery, in vitro labelling, in vivo imaging, tumor target, etc.

Application of Virus Targeting Nanocarrier Drug Delivery System in Virus-Induced Central Nervous System Disease Treatment

Virus-induced central nervous system (CNS) diseases represent a significant burden to animal health worldwide. The difficulty in treating these diseases is mainly attributable to the elaborate barrier system, which limits the transport of drugs to the infected sites. Therefore, it is necessary to develop smart delivery technologies for treatment of these diseases. In the study, viral nervous necrosis disease was studied as a model to evaluate the feasibility of multiwalled carbon nanotubes (MWCNTs) conjugated with virus-specific nanobody and antiviral drug for targeted therapy of virus-induced CNS diseases. The virus (named as PGNNV) was isolated, identified and purified from diseased grouper. A naïve phage-displayed alpaca nanobody library was constructed, and the purified PGNNV was used for biopanning of PGNNV-specific nanobody from the library. The targeted delivery system based on MWCNTs conjugated with polyethylenimine, ribavirin, and PGNNV-specific nanobody was constructed and designated as MWCNTs-PEI-R-Nb. Targeting ability and treatment effects of the MWCNTs-PEI-R-Nb were checked both in vitro and in vivo. MWCNTs-PEI-R-Nb showed an increasing distribution in PGNNV-infected cells, and an obvious accumulation in the brain of PGNNV-infected zebrafish larvae. MWCNTs-PEI-R-Nb also showed a strong anti-PGNNV ability both in vitro and in vivo. The mortality of larvae treated with MWCNTs-PEI-R-Nb (equivalent to 100 mg/L ribavirin) was 27% during 10 days post infection, whereas it was 100% for the control group. The results so far indicate that MWCNTs conjugated with antiviral drugs and viral-specific antibody are effective means for virus-induced CNS disease targeted therapy.

The influence of Climate Change on the fate and behavior of different carbon nanotubes materials and implication to estuarine invertebrates

The widespread use of Carbon nanotubes (CNTs) has been increasing exponentially, leading to a significant potential release into the environment. Nevertheless, the toxic effects of CNTs in natural aquatic systems are related to their ability to interact with abiotic compounds. Considering that salinity variations are one of the main challenges in the environment and thus may influence the behavior and toxicity of CNTs, a laboratory experiment was performed exposing the tube-building polychaete Diopatra neapolitana (Delle Chiaje 1841) for 28 days to pristine multi-walled carbon nanotube (MWCNTs) and carboxylated MWCNTs, maintained at control salinity 28 and low salinity 21. An innovative approach based on thermogravimetric analysis (TGA) was adopted for the first time to assess the presence of MWCNTs aggregates in the organisms. Both CNTs generated toxic impacts in terms of regenerative capacity, energy reserves and metabolic capacity as well as oxidative and neuro status, however greater toxic impacts were observed in polychaetes exposed to carboxylated MWCNTs. Moreover, both CNTs maintained under control salinity (28) generated higher toxic impacts in the polychaetes compared to individuals maintained under low salinity (21), indicating that exposed polychaetes tend to be more sensitive to the alteration induced by salinity variations on the chemical behavior of both MWCNTs in comparison to salt stress.

Advanced biomedical applications of carbon nanotube

With advances in nanotechnology, the applications of nanomaterial are developing widely and greatly. The characteristic properties of carbon nanotubes (CNTs) make them the most selective candidate for various multi-functional applications. The greater surface area of the CNTs in addition to the capability to manipulate the surfaces and dimensions has provided greater potential for this nanomaterial. The CNTs possess greater potential for applications in biomedicine due to their vital electrical, chemical, thermal, and mechanical properties. The unique properties of CNT are exploited for numerous applications in the biomedical field. They are useful in both therapeutic and diagnostic applications. They form novel carrier systems which are also capable of site-specific delivery of therapeutic agents. In addition, CNTs are of potential application in biosensing. Many recently reported advanced systems of CNT could be exploited for their immense potential in biomedicine in the future.

Hydroxylated Single-Walled Carbon Nanotubes Inhibit Aβ42 Fibrillogenesis, Disaggregate Mature Fibrils, and Protect against Aβ42-Induced Cytotoxicity

The fibrillogenesis of amyloid-β protein (Aβ) is considered a crucial factor in the pathogenesis of Alzheimer's disease (AD). Hence, inhibiting Aβ fibrillogenesis is regarded as the primary therapeutic strategy for the prevention and treatment of AD. However, the development of effective inhibitors against Aβ fibrillogenesis has faced significant challenges. Previous studies have shown that pristine single-walled carbon nanotubes (SWNTs) can inhibit fibrillogenesis of some amyloid proteins. However, the poor dispersibility of SWNTs in an aqueous environment greatly hinders their inhibitory efficacy. Here, we examined the inhibitory activity of hydroxylated SWNTs (SWNT-OH) on the aggregation and cytotoxicity of Aβ₄₂ using thioflavin T (ThT) fluorescence, atomic force microscopy (AFM), cellular viability assays, and molecular dynamics (MD) simulations. ThT and AFM results showed that SWNT-OH inhibits Aβ₄₂ fibrillogenesis and disaggregates preformed amyloid fibrils in a dose-dependent manner. Furthermore, the ratio of hydroxyl groups in SWNT-OH is crucial for their effect against Aβ₄₂ aggregation. SWNT-OH exerted cytoprotective effects against Aβ₄₂ fibrillation-induced cytotoxicity. The results of free-energy decomposition studies based on MD simulations revealed that nonpolar interactions, and especially van der Waals forces, contributed most of the free energy of binding in the SWNT-OH-Aβ complex. Two regions of the Aβ pentamer were identified to interact with SWNT-OH, spanning H13-Q15 and V36-G38. The findings presented here will contribute to a comprehensive understanding of the inhibitory effect of hydroxylated nanoparticles against Aβ fibrillogenesis, which is critical for the search for more effective agents that can counteract amyloid-mediated pathologies.

Nanotheranostics, a future remedy of neurological disorders

INTRODUCTION

Effective therapy of various neurological disorders is hindered on account of the failure of various therapeutics crossing blood-brain-barrier (BBB). Nanotheranostics has emerged as a cutting-edge unconventional theranostic nanomedicine, capable of realizing accurate diagnosis together with effective and targeted delivery of therapeutics across BBB to the unhealthy regions of the brain for potential clinical success.

AREAS COVERED

We have tried to review the current status of nanotheranostic based approaches followed to manage neurological disorders. The focus has been majorly laid on to explore various theranostic nanoparticles and their application potential towards image-guided neurotherapies. Additionally, the usefulness of exceptional diagnostic, imaging techniques including magnetic resonance imaging and fluorescence imaging are being discussed by highlighting their promising opportunities in the detection, diagnosis, and treatment of the neurological disorders.

EXPERT OPINION

Inimitable diagnostic and therapeutic potential of nanotheranostics have accomplished the aim of personalized therapies by governing the therapeutic efficacy of the system along with facilitating patient pre-selection grounded on non-invasive imaging, thereby predicting the responses of patients to nanomedicine treatments. While these accomplishments are encouraging, they are still the minority and demands for a continuous effort to improve sensitivity and precision in screening/diagnosis along with improving therapeutic efficacy in various neural disorders.

An Overview of the Recent Progress in the Synthesis and Applications of Carbon Nanotubes

Carbon nanotubes (CNTs) are known as nano-architectured allotropes of carbon, having graphene sheets that are wrapped forming a cylindrical shape. Rolling of graphene sheets in different ways makes CNTs either metals or narrow-band semiconductors. Over the years, researchers have devoted much attention to understanding the intriguing properties CNTs. They exhibit some unusual properties like a high degree of stiffness, a large length-to-diameter ratio, and exceptional resilience, and for this reason, they are used in a variety of applications. These properties can be manipulated by controlling the diameter, chirality, wall nature, and length of CNTs which are in turn, synthesis procedure-dependent. In this review article, various synthesis methods for the production of CNTs are thoroughly elaborated. Several characterization methods are also described in the paper. The applications of CNTs in various technologically important fields are discussed in detail. Finally, future prospects of CNTs are outlined in view of their commercial applications.

Carbon nanotubes and central nervous system: Environmental risks, toxicological aspects and future perspectives

Due to their morphological and physicochemical properties, carbon nanotubes (CNTs) enhance the structural properties of several materials and are produced in great volumes. The production and the manufacturing of CNTs-incorporated products can lead to the potential environmental release of CNTs. For these reasons, CNTs can represent a serious concern for human health. Humans are exposed to nanoparticles through inhalation, ingestion and skin uptake. After their entrance, the particles can reach the Central Nervous System (CNS) through three different pathways: the systemic, olfactory and trigeminal pathways. In the first, through systemic blood circulation, nanoparticles cross both the blood-brain and blood-spinal cord barriers, which are highly selective semipermeable barriers that protect the CNS compartments. The second is the step from the nose to brain route and occurs along axons and via nerve bundles that cross the cribriform plate to the olfactory bulb. In the third, the compounds diffuse through the nasal cavity mucosa to reach the branches of the trigeminal nerve in the olfactory and respiratory regions, and they reach brain stem via axonal transport. After their entrance, CNTs reach the CNS where they may cause cytotoxicity of selected neurons in several CNS regions, impairing molecular pathways and contributing to the onset and progression of chronic brain inflammation, microglia activation and white matter abnormalities with an increased risk for autism spectrum disorders, lower IQ in children, neurodegenerative diseases and stroke. The large surface area to mass ratio of CNTs greatly increases surface reactivity. Despite this property considerable contributes to their toxicological profile in biological systems, also makes CNTs very attractive in the medical field, where they can be used as carriers of bioactive molecules, contrast agents, biological platforms and for many other applications in medicine.

Fabrication and characterisation of 3D printed MWCNT composite porous scaffolds for bone regeneration

Carbon nanotubes (CNTs) with exceptional physical and chemical properties are attracting significant interest in the field of tissue engineering. Several reports investigated CNTs biocompatibility and their impact in terms of cell attachment, proliferation and differentiation mainly using polymer/CNTs membranes. However, these 2D membranes are not able to emulate the complex in vivo environment. In this paper, additive manufacturing (3D printing) is used to create composite 3D porous scaffolds containing different loadings of multi-walled carbon nanotubes (MWCNT) (0.25, 0.75 and 3 wt%) for bone tissue regeneration. Pre-processed and processed materials were extensively characterised in terms of printability, morphological and topographic characteristics and thermal, mechanical and biological properties. Scaffolds with pore sizes ranging between 366 μm and 397 μm were successfully produced and able to sustain early-stage human adipose-derived mesenchymal stem cells attachment and proliferation. Results show that MWCNTs enhances protein adsorption, mechanical and biological properties. Composite scaffolds, particularly the 3 wt% loading of MWCNTs, seem to be good candidates for bone tissue regeneration.

Effect of the Aspect Ratio of Coiled-Coil Protein Carriers on Cellular Uptake

We showed previously that a rigid and fibrous-structured cationic coiled-coil artificial protein had cell-penetrating activity that was significantly greater when compared with a less-structured cell-penetrating peptide. Nanomaterials with anisotropic structures often show aspect-ratio-dependent unique physicochemical properties, as well as cell-penetrating activities. In this report, we have designed and demonstrated the cell-penetrating activity of a shorter cationic coiled-coil protein. An aspect ratio at 4.5:1 was found to be critical for ensuring that the cationic coiled-coil protein showed strong cell-penetrating activity. At an aspect ratio of 3.5:1, the cationic coiled-coil protein showed cell-penetrating activity that was similar to a less-structured short cationic cell-penetrating peptide. Interestingly, at an aspect ratio of 4:1, the cationic coiled-coil protein exhibited intermediate cell-penetrating activity. These findings should aid in the principle design of intracellular drug delivery carriers including coiled-coil artificial proteins, their derivatives, and α-helical cell-penetrating peptides as well as provide a framework for developing synthetic nanomaterials, such as metal nanorods and synthetic polymers.

Nanostructures: between natural environment and medical practice

Nanoparticles (NPs) are small structures under 100 nm in dimension. Interrelationships among the morphological parameters and toxicity of NPs have been the focus of several investigations that assessed potential health risk in environmentally-exposed subjects and the realistic uses of NPs in medical practice. In the current review, we provide a summary of the cellular mechanisms of membrane-mediated transport, including old and novel molecules that transport nanostructures across cellular membranes. The effects of geochemical exposure to natural NPs are evaluated through epidemiological data and cancerous pathways activated by Fe2+ NPs. Specifically, we discuss screening for papillary thyroid carcinomas in the inhabitants of the Sicilian volcanic area surrounding Mount Etna to compare the incidence of thyroid carcinoma in this population. Lastly, considering the increased production of carbon nanotubes (CNTs), we examine the toxicity and potential use of these engineered NPs in drug delivery of an extensive amount of therapeutic and imaging molecules (theranosis) that can be conjugated to CNTs.

Influence of Carbon Nanotubes and Its Derivatives on Tumor Cells In Vitro and Biochemical Parameters, Cellular Blood Composition In Vivo

The aim of the proposed work was to analyze the toxicity of oxidized carbon nanotubes (CNTox), functionalized by doxorubicin (CNT-Dox) and fluorescein (CNT-FITC) on cell and organism level. The cytotoxic effect of CNTox, CNT-Dox, and CNT-FITC was analyzed on tumor cells in vitro (2-D, 3-D cultures) and on Balb2/c mice model in vivo. As a result, it was demonstrated the possibility of doxorubicin immobilization on the surface of CNT and controlled release of doxorubicin (Dox) from the surface of CNT. Dox immobilization coincident with decreasing cytotoxic effect CNT-Dox compared with free Dox. Breakdown of peptide bonds with CNT surface led to the release of doxorubicin and dose-dependent enhancement of the cytotoxic effect of CNTs and Dox. The combined cytotoxic effect from CNTs, Dox, and trypsin on the survival of tumor cells was shown. At the organism level, it was investigated the effect of the obtained nanostructures on the state of hepatic enzymatic system, the protein metabolism, and cell blood composition of the experimental animals. CNTox influence in vivo model was statistically the same as control. CNT-Dox demonstrated lower total organism toxic effect compared to the pure doxorubicin. Deviations in the cell blood composition indicated a general toxic effect of CNT-Dox, but it was more moderate compared with of pure doxorubicin. From the data obtained, we concluded that binding CNTs with doxorubicin allows reducing toxicity of the doxorubicin on the general biochemical indicators of blood and violations in the blood cells composition in vivo. At the same time, the combined effect of CNTs and doxorubicin after drug release allowed us to achieve greater efficacy in suppressing tumor growth in vitro.