Can Carbon Nanotubes Deliver on Their Promise in Biology? Harnessing Unique Properties for Unparalleled Applications

Magnetic carbon nanotubes modified with proteins and hydrophilic monomers: Cytocompatibility, in-vitro toxicity assays and permeation across biological interfaces

Carbon nanotubes are promising materials for biomedical applications like delivery systems and tissue scaffolds. In this paper, magnetic carbon nanotubes (M-CNTs) covered with bovine serum albumin (M-CNTs-BSA) or functionalized with hydrophilic monomers (M-CNTs-HL) were synthesized, characterized, and evaluated concerning their interaction with Caco-2 cells. There is no comparison between these two types of functionalization, and this study aimed to verify their influence on the material's interaction with the cells. Different concentrations of the nanotubes were applied to investigate cytotoxicity, cell metabolism, oxidative stress, apoptosis, and capability to cross biomimetic barriers. The materials showed cytocompatibility up to 100 μg mL-1 and a hemolysis rate below 2 %. Nanotubes' suspensions were allowed to permeate Caco-2 monolayers for up to 8 h under the effect of the magnetic field. Magnetic nanoparticles associated with the nanotubes allowed estimation of permeation through the monolayers, with values ranging from 0.50 to 7.19 and 0.27 to 9.30 × 10-3 μg (equivalent to 0.43 to 6.22 and 0.23 to 9.54 × 10-2 % of the initially estimated mass of magnetic nanoparticles) for cells exposed and non-exposed to the magnets, respectively. Together, these results support that the developed materials are promising for applications in biomedical and biotechnological fields.

Pulmonary Surfactant Homeostasis Dysfunction Mediates Multiwalled Carbon Nanotubes Induced Lung Fibrosis via Elevating Surface Tension

Multiwalled carbon nanotubes (MWCNTs) have been widely used in many disciplines and raised great concerns about their negative health impacts, especially environmental and occupational exposure. MWCNTs have been reported to induce fibrotic responses; however, the underlying mechanisms remain largely veiled. Here, we reported that MWCNTs inhalation induced lung fibrosis together with decreased lung compliance, increased elastance in the mice model, and elevated surface tension in vitro. Specifically, MWCNTs increased surface tension by impairing the function of the pulmonary surfactant. Mechanistically, MWCNTs induced lamellar body (LB) dysfunction through autophagy dysfunction, which then leads to surface tension elevated by pulmonary surfactant dysfunction in the context of lung fibrosis. This is a study to investigate the molecular mechanism of MWCNTs-induced lung fibrosis and focus on surface tension. A direct mechanistic link among impaired LBs, surface tension, and fibrosis has been established. This finding elucidates the detailed molecular mechanisms of lung fibrosis induced by MWCNTs. It also highlights that pulmonary surfactants are expected to be potential therapeutic targets for the prevention and treatment of lung fibrosis induced by MWCNTs.

How to fix a broken heart-designing biofunctional cues for effective, environmentally-friendly cardiac tissue engineering

Cardiovascular diseases bear strong socioeconomic and ecological impact on the worldwide healthcare system. A large consumption of goods, use of polymer-based cardiovascular biomaterials, and long hospitalization times add up to an extensive carbon footprint on the environment often turning out to be ineffective at healing such cardiovascular diseases. On the other hand, cardiac cell toxicity is among the most severe but common side effect of drugs used to treat numerous diseases from COVID-19 to diabetes, often resulting in the withdrawal of such pharmaceuticals from the market. Currently, most patients that have suffered from cardiovascular disease will never fully recover. All of these factors further contribute to the extensive negative toll pharmaceutical, biotechnological, and biomedical companies have on the environment. Hence, there is a dire need to develop new environmentally-friendly strategies that on the one hand would promise cardiac tissue regeneration after damage and on the other hand would offer solutions for the fast screening of drugs to ensure that they do not cause cardiovascular toxicity. Importantly, both require one thing-a mature, functioning cardiac tissue that can be fabricated in a fast, reliable, and repeatable manner from environmentally friendly biomaterials in the lab. This is not an easy task to complete as numerous approaches have been undertaken, separately and combined, to achieve it. This review gathers such strategies and provides insights into which succeed or fail and what is needed for the field of environmentally-friendly cardiac tissue engineering to prosper.

Self-Assembled Crystalline Bundles in Soluble Metal-Organic Nanotubes

The use of nanotubes in the solution state is crucial not only for the exploration of physical and chemical behaviors at the molecular level but also for application such as thin-film fabrication. Surface modification is generally used to solubilize carbon nanotubes (CNTs) and various synthetic nanotubes; however, this method may affect the surface properties of the original nanotubes, and the detailed crystal structure obtained after modification is unclear. Here, we report the synthesis of a crystalline and soluble metal-organic nanotube consisting of a cationic tubular framework and an anion with a long alkyl chain. The nanotubular structures are formed not only in the solid state but also in the solution state, as confirmed by an X-ray structural analysis, optical measurements, and electron microscopy studies. This nanotube system is realized in different states without any surface modification, which is quite different from typical CNTs and synthetic nanotubes. In addition, self-assembled crystalline bundles are directly observed using transmission electron microscopy (TEM) for the first time in a metal-organic nanotube system. The bundle structures are also confirmed by atomic force microscopy (AFM) observations of thin nanotube films. We envisage a systematic design of such soluble metal-organic nanotubes that will enable direct observation of mass transport behavior in channels of bundles or a single nanotube, as well as a wide range of thin-film applications.

Preparation, characterization and properties of three different nanomaterials either alone or loaded with nystatin or fluconazole antifungals

Engineered nanoparticles have enabled the development of novel uses, particularly in disease management. In this investigation, we synthesized and studied three distinct nanomaterials: solid lipid nanoparticles (SLNPs), chitosan nanoparticles (CSNPs), and carbon nanotubes (CNTs), either alone or loaded with two antifungals, nystatin, and fluconazole. The purpose of this study is to investigate the different properties of the produced nanomaterials, either alone or in combination with antifungals. Drug release studies revealed that about 55% from SLNPs, 43% from CSNPs and 97% from CNTs of nystatin drug were released at the longest time point assessed (12 h). In addition, about 89% from SLNPs, 84% from CSNPs and 81% from CNTs of fluconazole drug were released at the longest time point assessed (12 h). This research will expand the understanding of nanomaterials as a viable technique for the management of different fungal diseases that harm several agricultural crops.

Single-walled carbon nanotubes protect photosynthetic reactions in Chlamydomonas reinhardtii against photoinhibition

Single-walled carbon nanotubes (SWCNTs) are among the most exploited carbon allotropes in nanosensing, bioengineering, and photobiological applications, however, the interactions of nanotubes with the photosynthetic process and structures are still poorly understood. We found that SWCNTs are not toxic to the photosynthetic apparatus of the model unicellular alga Chlamydomonas reinhardtii and demonstrate that this carbon nanomaterial can protect algal photosynthesis against photoinhibition. The results show that the inherent phytotoxicity of the nanotubes may be overcome by an intentional selection of nanomaterial characteristics. A low concentration (2 μg mL-1) of well-dispersed, purified and small SWCNTs did not alter the growth and pigment accumulation of the cultures. Indeed, under the photoinhibitory conditions of our experiments, SWCNT-enriched samples were characterized by a lower rate of PSII inactivation, reduced excitation pressure in PSII, a higher rate of photosynthetic electron transport, and an increased non-photochemical quenching in comparison with the controls. In addition, SWCNTs change the distribution of energy between the photosystems in favour of PSII (state 1). The underlying mechanism of this action is not yet understood but possibly, electrons or energy can be exchanged between the redox active nanotubes and photosynthetic components, and probably other redox active intra-chloroplast constituents. Alternatively, nanotubes may promote the formation of an NPQ conformation of PSII. Our results provided evidence for such electron/energy transfer from photosynthetic structures toward the nanotubes. The discovered photoprotective effects can potentially be used in photobiotechnology to maintain the photosynthetic activity of microorganisms under unfavourable conditions.

Application of carbon nanotubes in sensing/monitoring of pancreas and liver cancer

Liver and pancreatic tumors are among the third leading causes of cancer-associated death worldwide. In addition to poor prognosis, both cancer types are diagnosed at advanced and metastatic stages without typical prior symptoms. Unfortunately, the existing theranostic approaches are inefficient in cancer diagnosis and treatment. Carbon nanotubes (CNTs) have attracted increasing attention in this context due to their distinct properties, including variable functionalization capability, biocompatibility, and excellent thermodynamic and optical features. As a consequence, they are now regarded as one of the most promising materials for this application. The current review aims to summarize and discuss the role of CNT in pancreatic and liver cancer theranostics. Accordingly, the breakthroughs achieved so far are classified based on the cancer type and analyzed in detail. The most feasible tactics utilizing CNT-based solutions for both cancer diagnosis and treatment are presented from the biomedical point of view. Finally, a future outlook is provided, which anticipates how the R&D community can build on the already developed methodologies and the subsequent biological responses of the pancreatic and liver cancer cells to the directed procedures.

Enzymatic and Cellular Degradation of Carbon-Based Biconcave Nanodisks

The assessment of the biodegradability of nanomaterials is of pragmatic importance for understanding the interactions between nanomaterials and biological systems and for the determination of ultimate fate of these materials as well as their potential use. We recently developed carbon-based biconcave nanodisks (CBBNs) serving as a versatile nanocarrier for enhanced accumulation in tumors and combined photothermal-chemotherapy. Here, we investigate both the enzymatic and cellular degradation of CBBNs by monitoring their cellular response with electron microscopy, near-infrared absorbance spectroscopy, and cell viability and oxidative stress assessments. Our results show that CBBNs underwent significant degradation in solutions catalyzed by horseradish peroxidase (HRP) and hydrogen peroxide (H₂O₂), or in the presence of macrophage cells. The ability of CBBNs to be degraded in biological systems provides suitability for their future biomedical applications.

Pyrene-polyethylene glycol-modified multi-walled carbon nanotubes: Genotoxicity in V79-4 fibroblast cells

The genotoxicity of pyrene-polyethylene glycol-modified multi-walled carbon nanotubes (MWCNT-PyPEG), engineered as a nanoplatform for bioapplication, was evaluated. Toxicity was assessed in hamster lung fibroblast cells (V79-4). MTT and Cell Titer Blue methods were used to evaluate cell viability. Genotoxicity was measured by the comet assay and the cytokinesis-block micronucleus cytome (CBMN-Cyt) assay, and fluorescence in situ hybridization (FISH) was used to test induction of structural chromosome aberrations (clastogenic activity) and/or numerical chromosome changes (aneuploidogenic activity). Exogenous metabolic activation enzymes were used in the CBMN-Cyt and FISH tests. Only with metabolic activation, the hybrids caused chromosomal damage, by both clastogenic and aneugenic processes.

Semiconducting Carbon Nanotube-Based Nanodevices for Monitoring the Effects of Chlorphenamine on the Activities of Intracellular Ca2+ Stores

We report a flexible and noninvasive method based on field-effect transistors hybridizing semiconducting single-walled carbon nanotubes for monitoring the effects of histamine on Ca²⁺ release from the intracellular stores of a nonexcitable cell. These nanodevices allowed us to evaluate the real-time electrophysiological activities of HeLa cells under the stimulation of histamine via the recording of the conductance changes of the devices. These changes resulted from the binding of histamine to its receptor type 1 on the HeLa cell membrane. Moreover, the effects of chlorphenamine, an antihistamine, on the electrophysiological activities of a single HeLa cell were also evaluated, indicating that the pretreatment of the cell with chlorpheniramine decreased intracellular Ca²⁺ release. Significantly, we only utilized a single nanodevice to perform the measurements for multiple cells pretreated with various concentrations of chlorphenamine. This enabled the statistically meaningful analysis of drug effects on cells without errors from device variations. Obtained results indicated the novel advantages of our method such as real-time monitoring and quantitative capability. Our devices, therefore, can be efficient tools for biomedical applications such as electrophysiology research and drug screening.

Myeloid ABCG1 Deficiency Enhances Apoptosis and Initiates Efferocytosis in Bronchoalveolar Lavage Cells of Murine Multi-Walled Carbon Nanotube-Induced Granuloma Model

The use of carbon nanotubes has increased in the past few decades. Carbon nanotubes are implicated in the pathogenesis of pulmonary sarcoidosis, a chronic granulomatous inflammatory condition. We developed a murine model of chronic granulomatous inflammation using multiwall carbon nanotubes (MWCNT) to investigate mechanisms of granuloma formation. Using this model, we demonstrated that myeloid deficiency of ATP-binding cassette (ABC) cholesterol transporter (ABCG1) promotes granuloma formation and fibrosis with MWCNT instillation; however, the mechanism remains unclear. Our previous studies showed that MWCNT induced apoptosis in bronchoalveolar lavage (BAL) cells of wild-type (C57BL/6) mice. Given that continual apoptosis causes persistent severe lung inflammation, we hypothesized that ABCG1 deficiency would increase MWCNT-induced apoptosis thereby promoting granulomatous inflammation and fibrosis. To test our hypothesis, we utilized myeloid-specific ABCG1 knockout (ABCG1 KO) mice. Our results demonstrate that MWCNT instillation enhances pulmonary fibrosis in ABCG1 KO mice compared to wild-type controls. Enhanced fibrosis is indicated by increased trichrome staining and transforming growth factor-beta (TGF-β) expression in lungs, together with an increased expression of TGF-β related signaling molecules, interleukin-13 (IL-13) and Smad-3. MWCNT induced more apoptosis in BAL cells of ABCG1 KO mice. Initiation of apoptosis is most likely mediated by the extrinsic pathway since caspase 8 activity and Fas expression are significantly higher in MWCNT instilled ABCG1 KO mice compared to the wild type. In addition, TUNEL staining shows that ABCG1 KO mice instilled with MWCNT have a higher percentage of TUNEL positive BAL cells and more efferocytosis than the WT control. Furthermore, BAL cells of ABCG1 KO mice instilled with MWCNT exhibit an increase in efferocytosis markers, milk fat globule-EGF factor 8 (MFG-E8) and integrin β3. Therefore, our observations suggest that ABCG1 deficiency promotes pulmonary fibrosis by MWCNT, and this effect may be due to an increase in apoptosis and efferocytosis in BAL cells.

The Role of Temperature on the Degree of End-Closing and Filling of Single-Walled Carbon Nanotubes

Carbon nanotubes (CNTs), owing to their high surface area-to-volume ratio and hollow core, can be employed as hosts for adsorbed and/or encapsulated molecules. At high temperatures, the ends of CNTs close spontaneously, which is relevant for several applications, including catalysis, gas storage, and biomedical imaging and therapy. This study highlights the influence of the annealing temperature in the range between 400 and 1100 °C on the structure and morphology of single-walled CNTs. The nitrogen adsorption and density functional theory calculations indicate that the fraction of end-closed CNTs increases with temperature. Raman spectroscopy reveals that the thermal treatment does not alter the tubular structure. Insight is also provided into the efficacy of CNTs filling from the molten phase, depending on the annealing temperature. The CNTs are filled with europium (III) chloride and analyzed by using electron microscopy (scanning electron microscopy and high-resolution transmission electron microscopy) and energy-dispersive X-ray spectroscopy, confirming the presence of filling and closed ends. The filling yield increases with temperature, as determined by thermogravimetric analysis. The obtained results show that the apparent surface area of CNTs, fraction of closed ends, and amount of encapsulated payload can be tailored via annealing.

Advances and Perspectives in the Use of Carbon Nanotubes in Vaccine Development

Advances in nanobiotechnology have allowed the utilization of nanotechnology through nanovaccines. Nanovaccines are powerful tools for enhancing the immunogenicity of a specific antigen and exhibit advantages over other adjuvant approaches, with features such as expanded stability, prolonged release, decreased immunotoxicity, and immunogenic selectivity. We introduce recent advances in carbon nanotubes (CNTs) to induce either a carrier effect as a nanoplatform or an immunostimulatory effect. Several studies of CNT-based nanovaccines revealed that due to the ability of CNTs to carry immunogenic molecules, they can act as nonclassical vaccines, a quality not possessed by vaccines with traditional formulations. Therefore, adapting and modifying the physicochemical properties of CNTs for use in vaccines may additionally enhance their efficacy in inducing a T cell-based immune response. Accordingly, the purpose of this study is to renew and awaken interest in and knowledge of the safe use of CNTs as adjuvants and carriers in vaccines.

Ivermectin-functionalized multiwall carbon nanotube enhanced the locomotor activity and neuropathic pain by modulating M1/M2 macrophage and decrease oxidative stress in rat model of spinal cord injury

Since the inflammation and oxidative stress is the main pathophysiological pathway of neural damage in spinal cord injury (SCI), we tried to evaluate the role of ivermectin (IVM) combined with multi-walled carbon nanotube (MWCNT) in the treatment settings of SCI and its underlying mechanism. Wistar rats with T9 vertebra laminectomy in five groups of: sham-operated, vehicle, IVM (0.1 mg/kg), IVM-MWCNT (0.1 mg/kg), and minocycline (90 mg/kg) were used. We evaluated the locomotor scaling and other behavioral tests for neuropathic pain. Also, tissue samples were obtained to evaluate the expression of M1 and M2 macrophage marker, concentration of TNF-α, IL-1β, and IL-1, and oxidative stress level to assess neuroinflammatory changes. Both IVM and IVM-MWCNT after induction of SCI significantly enhanced the experimental tasks' outcomes, including locomotion and neuropathic tests. Also, decreasing in pro-inflammatory cytokines including TNF-α, IL-1β, and IL-1 in the spinal cord and dorsal root ganglion tissues was also notable in both IVM and IVM-MWCNT-treated groups 28 days after induction of SCI in compared to the vehicle-treated SCI group. Both IVM and IVM-MWCNT significantly decreased oxidative stress, induced by SCI, based on the results of ROS and NADPH activity. IVM-MWCNT-treated animals indicated better outcome in every previous experiment in comparison to IVM-treated animals. The effectiveness of IVM-MWCNT was similar to minocycline treatment in all experimental task (as positive control group). IVM-MWCNT might be a novel treatment in spinal cord injury, which could act through decreasing the oxidative stress and increase the polarization of M1 in comparison to M2 macrophages.

Applications of nanomaterials in tissue engineering

Recent advancement in nanotechnology has brought prominent benefits in tissue engineering, which has been used to repair or reconstruct damaged tissues or organs and design smart drug delivery systems. With numerous applications of nanomaterials in tissue engineering, it is vital to choose appropriate nanomaterials for different tissue engineering applications because of the tissue heterogeneity. Indeed, the use of nanomaterials in tissue engineering is directly determined by the choice. In this review, we mainly introduced the use of nanomaterials in tissue engineering. First, the basic characteristics, preparation and characterization methods of the types of nanomaterials are introduced briefly, followed by a detailed description of the application and research progress of nanomaterials in tissue engineering and drug delivery. Finally, the existing challenges and prospects for future applications of nanomaterials in tissue engineering are discussed.

Scientific description about the types, synthesis, functionalization, characterization application, challenges and prospects of nanomaterials in tissue engineering.

Investigation of Fractal Carbon Nanotube Networks for Biophilic Neural Sensing Applications

We propose a carbon-nanotube-based neural sensor designed to exploit the electrical sensitivity of an inhomogeneous fractal network of conducting channels. This network forms the active layer of a multi-electrode field effect transistor that in future applications will be gated by the electrical potential associated with neuronal signals. Using a combination of simulated and fabricated networks, we show that thin films of randomly-arranged carbon nanotubes (CNTs) self-assemble into a network featuring statistical fractal characteristics. The extent to which the network's non-linear responses will generate a superior detection of the neuron's signal is expected to depend on both the CNT electrical properties and the geometric properties of the assembled network. We therefore perform exploratory experiments that use metallic gates to mimic the potentials generated by neurons. We demonstrate that the fractal scaling properties of the network, along with their intrinsic asymmetry, generate electrical signatures that depend on the potential's location. We discuss how these properties can be exploited for future neural sensors.

Nanobiosensor Reports on CDK1 Kinase Activity in Tumor Xenografts in Mice

Probing the dynamics and quantifying the activities of intracellular protein kinases that coordinate cell growth and division and constitute biomarkers and pharmacological targets in hyperproliferative and pathological disorders remain a challenging task. Here engineering and characterization of a nanobiosensor of the mitotic kinase CDK1, through multifunctionalization of carbon nanotubes with a CDK1-specific fluorescent peptide reporter, are described. This original reporter of CDK1 activity combines the sensitivity of a fluorescent biosensor with the unique physico-chemical and biological properties of nanotubes for multifunctionalization and efficient intracellular penetration. The functional versatility of this nanobiosensor enables implementation to quantify CDK1 activity in a sensitive and dose-dependent fashion in complex biological environments in vitro, to monitor endogenous kinase in living cells and directly within tumor xenografts in mice by fluorescence imaging, thanks to a ratiometric quantification strategy accounting for response relative to concentration in space and in time.

Synthesis of covalent bonding MWCNT-oligoethylene linezolid conjugates and their antibacterial activity against bacterial strains

Nowadays, infectious diseases caused by drug-resistant bacteria have become especially important. Linezolid is an antibacterial drug active against clinically important Gram positive strains; however, resistance showed by these bacteria has been reported. Nanotechnology has improved a broad area of science, such as medicine, developing new drug delivery and transport systems. In this work, several covalently bounded conjugated nanomaterials were synthesized from multiwalled carbon nanotubes (MWCNTs), a different length oligoethylene chain (S_n), and two linezolid precursors (4 and 7), and they were evaluated in antibacterial assays. Interestingly, due to the intrinsic antibacterial activity of the amino-oligoethylene linezolid analogues, these conjugated nanomaterials showed significant antibacterial activity against various tested bacterial strains in a radial diffusion assay and microdilution method, including Gram negative strains as Escherichia coli (11 mm, 6.25 μg mL⁻¹) and Salmonella typhi (14 mm, ≤0.78 μg mL⁻¹), which are not inhibited by linezolid. The results show a significant effect of the oligoethylene chain length over the antibacterial activity. Molecular docking of amino-oligoethylene linezolid analogs shows a more favorable interaction of the S₂-7 analog in the PTC of E. coli.

New MWCNTs amino-oligoethylene linezolid conjugates having outstanding activity against Gram negative strains.

Biomolecule-Directed Carbon Nanotube Self-Assembly

The strategy of combining biomolecules and synthetic components to develop biohybrids is becoming increasingly popular for preparing highly customized and biocompatible functional materials. Carbon nanotubes (CNTs) benefit from bioconjugation, allowing their excellent properties to be applied to biomedical applications. This study reviews the state-of-the-art research in biomolecule-CNT conjugates and discusses strategies for their self-assembly into hierarchical structures. The review focuses on various highly ordered structures and the interesting properties resulting from the structural order. Hence, CNTs conjugated with the most relevant biomolecules, such as nucleic acids, peptides, proteins, saccharides, and lipids are discussed. The resulting well-defined composites allow the nanoscale properties of the CNTs to be exploited at the micro- and macroscale, with potential applications in tissue engineering, sensors, and wearable electronics. This review presents the underlying chemistry behind the CNT-based biohybrid materials and discusses the future directions of the field.

Safe Nanoparticles: Are We There Yet?

The field of nanotechnology has grown over the last two decades and made the transition from the benchtop to applied technologies. Nanoscale-sized particles, or nanoparticles, have emerged as promising tools with broad applications in drug delivery, diagnostics, cosmetics and several other biological and non-biological areas. These advances lead to questions about nanoparticle safety. Despite considerable efforts to understand the toxicity and safety of these nanoparticles, many of these questions are not yet fully answered. Nevertheless, these efforts have identified several approaches to minimize and prevent nanoparticle toxicity to promote safer nanotechnology. This review summarizes our current knowledge on nanoparticles, their toxic effects, their interactions with mammalian cells and finally current approaches to minimizing their toxicity.

Selective Uptake of Carboxylated Multi-Walled Carbon Nanotubes by Class A Type 1 Scavenger Receptors and Impaired Phagocytosis in Alveolar Macrophages

The production and applications of multi-walled carbon nanotubes (MWNTs) have increased despite evidence that MWNTs can be toxic. Recently, we reported that the binding of Pluronic^® F-108 (PF108)-coated carboxylated MWNTs (C-MWNTs) to macrophages is inhibited by class A scavenger receptors (SR-As) antagonists (R. Wang et al., 2018. Nanotoxicology 12:677-690). The current study investigates the uptake of PF108-coated MWNTs by macrophages lacking SR-A1 and by CHO cells that ectopically express SR-A1. Macrophages without SR-A1 failed to take up C-MWNTs and CHO cells that expressed SR-A1 did take up C-MWNTs, but not pristine MWNTs (P-MWNTs) or amino-functionalized MWNTs (N-MWNTs). The dependence of C-MWNT uptake on SR-A1 is strong evidence that SR-A1 is a receptor for C-MWNTs. The consequences of SR-A1-dependent C-MWNT accumulation on cell viability and phagocytic activity in macrophages were also studied. C-MWNTs were more toxic than P-MWNTs and N-MWNTs in cell proliferation and colony formation tests. C-MWNTs reduced surface SR-A1 levels in RAW 264.7 cells and impaired phagocytic uptake of three known SR-A1 ligands, polystyrene beads, heat-killed E. coli, and oxLDL. Altogether, results of this study confirmed that SR-A1 receptors are important for the selective uptake of PF108-coated C-MWNTs and that accumulation of the C-MWNTs impairs phagocytic activity and cell viability in macrophages.

Nanotechnology for the Treatment of Spinal Cord Injury

Spinal cord injury (SCI) affects the central nervous system (CNS) and there is currently no treatment with the potential for rehabilitation. Although several clinical treatments have been developed, they are still at an early stage and have not shown success in repairing the broken fiber, which prevents cellular regeneration and integral restoration of motor and sensory functions. Considering the importance of nanotechnology and tissue engineering for neural tissue injuries, this review focuses on the latest advances in nanotechnology for SCI treatment and tissue repair. The PubMed database was used for the bibliographic survey. Initial research using the following keywords "tissue engineering and spinal cord injury" revealed 970 articles published in the last 10 years. The articles were further analyzed, excluding those not related to SCI or with results that did not pertain to the field of interest, including the reviews. It was observed that a total of 811 original articles used the quoted keywords. When the word "treatment" was added, 662 articles were found and among them, 529 were original ones. Finally, when the keywords "Nanotechnology and spinal cord injury" were used, 102 articles were found, 65 being original articles. A search concerning the biomaterials used for SCI found 700 articles with 589 original articles. A total of 107 articles were included in the discussion of this review and some are used for the theoretical framework. Recent progress in nanotechnology and tissue engineering has shown promise for repairing CNS damage. A variety of in vivo animal testing for SCI has been used with or without cells and some of these in vivo studies have shown successful results. However, there is no translation to humans using nanotechnology for SCI treatment, although there is one ongoing trial that employs a tissue engineering approach, among other technologies. The first human surgical scaffold implantation will elucidate the possibility of this use for further clinical trials. This review concludes that even though tissue engineering and nanotechnology are being investigated as a possibility for SCI treatment, tests with humans are still in the theoretical stage. Impact statement Thousands of people are affected by spinal cord injury (SCI) per year in the world. This type of lesion is one of the most severe conditions that can affect humans and usually causes permanent loss of strength, sensitivity, and motor function below the injury site. This article reviews studies on the PubMed database, assessing the publications on SCI in the study field of tissue engineering, focusing on the use of nanotechnology for the treatment of SCI. The review makes an evaluation of the biomaterials used for the treatment of this condition and the techniques applied for the production of nanostructured biomaterials.

Nanomaterials and Annelid Immunity: A Comparative Survey to Reveal the Common Stress and Defense Responses of Two Sentinel Species to Nanomaterials in the Environment

Simple Summary

Nanotechnology is a dynamically developing field producing large amounts of nanocompounds that are applied in industry, daily life, and health care. During production, use, and waste these materials could end up in water or soil. Large scale contaminations of our environment are a threat to public health. Pollution can have harmful effects on the immune system, as revealed by numerous studies in humans and other vertebrates. The relative simplicity of invertebrate immune functions offers potentially sensitive and accessible means of monitoring the effects and complex interactions of nanoparticles which ultimately affect host resistance. Among terrestrial and freshwater invertebrates, earthworms and leeches are the “keystone” species to evaluate the health of our ecosystems. In this review we compare the conserved stress and immune responses of these invertebrate model organisms toward nanoparticles. The obtained knowledge provides exciting insights into the conserved molecular and cellular mechanisms of nanomaterial-related toxicity in invertebrates and vertebrates. Understanding the unique characteristics of engineered nanoproducts and their interactions with biological systems in our environment is essential to the safe realization of these materials in novel biomedical applications.

Abstract

Earthworms and leeches are sentinel animals that represent the annelid phylum within terrestrial and freshwater ecosystems, respectively. One early stress signal in these organisms is related to innate immunity, but how nanomaterials affect it is poorly characterized. In this survey, we compare the latest literature on earthworm and leeches with examples of their molecular/cellular responses to inorganic (silver nanoparticles) and organic (carbon nanotubes) nanomaterials. A special focus is placed on the role of annelid immunocytes in the evolutionarily conserved antioxidant and immune mechanisms and protein corona formation and probable endocytosis pathways involved in nanomaterial uptake. Our summary helps to realize why these environmental sentinels are beneficial to study the potential detrimental effects of nanomaterials.

Impaired mitochondrial function of alveolar macrophages in carbon nanotube-induced chronic pulmonary granulomatous disease

Human exposure to carbon nanotubes (CNT) has been associated with the development of pulmonary sarcoid-like granulomatous disease. Our previous studies demonstrated that multi-walled carbon nanotubes (MWCNT) induced chronic pulmonary granulomatous inflammation in mice. Granuloma formation was accompanied by decreased peroxisome proliferator-activated receptor gamma (PPARγ) and disrupted intracellular lipid homeostasis in alveolar macrophages. Others have shown that PPARγ activation increases mitochondrial fatty acid oxidation (FAO) to reduce free fatty acid accumulation. Hence, we hypothesized that the disrupted lipid metabolism suppresses mitochondrial FAO. To test our hypothesis, C57BL/6 J mice were instilled by an oropharyngeal route with 100 μg MWCNT freshly suspended in 35 % Infasurf. Control sham mice received vehicle alone. Sixty days following instillation, mitochondrial FAO was measured in permeabilized bronchoalveolar lavage (BAL) cells. MWCNT instillation reduced the mitochondrial oxygen consumption rate of BAL cells in the presence of palmitoyl-carnitine as mitochondrial fuel. MWCNT also reduced mRNA expression of mitochondrial genes regulating FAO, carnitine palmitoyl transferase-1 (CPT1), carnitine palmitoyl transferase-2 (CPT2), hydroxyacyl-CoA dehydrogenase subunit beta (HADHB), and PPARγ coactivator 1 alpha (PPARGC1A). Importantly, both oxidative stress and apoptosis in alveolar macrophages and lung tissues of MWCNT-instilled mice were increased. Because macrophage PPARγ expression has been reported to be controlled by miR-27b which is known to induce oxidative stress and apoptosis, we measured the expression of miR-27b. Results indicated elevated levels in alveolar macrophages from MWCNT-instilled mice compared to controls. Given that inhibition of FAO and apoptosis are linked to M1 and M2 macrophage activation, respectively, the expression of both M1 and M2 key indicator genes were measured. Interestingly, results showed that both M1 and M2 phenotypes of alveolar macrophages were activated in MWCNT-instilled mice. In conclusion, alveolar macrophages of MWCNT-instilled mice had increased miR-27b expression, which may reduce the expression of PPARγ resulting in attenuation of FAO. This reduction in FAO may lead to activation of M1 macrophages. The upregulation of miR-27b may also induce apoptosis, which in turn can cause M2 activation of alveolar macrophages. These observations indicate a possible role of miR-27b in impaired mitochondrial function in the chronic activation of alveolar macrophages by MWCNT and the development of chronic pulmonary granulomatous inflammation.

Designer DNA-silica/carbon nanotube nanocomposites for traceable and targeted drug delivery

Due to their unique properties like porosity, high water content, softness and biocompatibility, hydrogels are of great interest for biomedical applications such as tissue engineering and drug delivery. We describe a programmable drug delivery system that is based on highly biocompatible SiNP/CNT-DNA nanocomposites, which can be synthesized in a highly modular fashion from DNA-functionalized carbon nanotubes and silica nanoparticles via enzymatic rolling circle amplification. Specific molecular recognition properties were implemented into the materials by DNA sequence design, as demonstrated by incorporation of GC/CG-rich stem loop and aptamer motifs that enable selective binding of intercalating drugs and cell surface receptors, respectively. In a proof-of-concept study we demonstrate the utility of this approach by targeting nanocomposites loaded with the anthracycline drug doxorubicin to HeLa cancer cells. Our observation that these designer materials work more efficiently than the pure drug alone suggests that further developments of the concept might be useful to selectively trigger more complex cellular pathways.

Recent Advances in Carbon Nanotubes for Nervous Tissue Regeneration

Regenerative medicine has taken advantage of several nanomaterials for reparation of diseased or damaged tissues in the nervous system involved in memory, cognition, and movement. Electrical, thermal, mechanical, and biocompatibility aspects of carbon-based nanomaterials (nanotubes, graphene, fullerenes, and their derivatives) make them suitable candidates to drive nerve tissue repair and stimulation. This review article focuses on key recent advances on the use of carbon nanotube- (CNT-) based technologies on nerve tissue engineering, outlining how neurons interact with CNT interfaces for promoting neuronal differentiation, growth and network reconstruction. CNTs still represent strong candidates for use in therapies of neurodegenerative pathologies and spinal cord injuries.

Neutron Activated 153Sm Sealed in Carbon Nanocapsules for in Vivo Imaging and Tumor Radiotherapy

Radiation therapy along with chemotherapy and surgery remain the main cancer treatments. Radiotherapy can be applied to patients externally (external beam radiotherapy) or internally (brachytherapy and radioisotope therapy). Previously, nanoencapsulation of radioactive crystals within carbon nanotubes, followed by end-closing, resulted in the formation of nanocapsules that allowed ultrasensitive imaging in healthy mice. Herein we report on the preparation of nanocapsules initially sealing "cold" isotopically enriched samarium (152Sm), which can then be activated on demand to their "hot" radioactive form (153Sm) by neutron irradiation. The use of "cold" isotopes avoids the need for radioactive facilities during the preparation of the nanocapsules, reduces radiation exposure to personnel, prevents the generation of nuclear waste, and evades the time constraints imposed by the decay of radionuclides. A very high specific radioactivity is achieved by neutron irradiation (up to 11.37 GBq/mg), making the "hot" nanocapsules useful not only for in vivo imaging but also therapeutically effective against lung cancer metastases after intravenous injection. The high in vivo stability of the radioactive payload, selective toxicity to cancerous tissues, and the elegant preparation method offer a paradigm for application of nanomaterials in radiotherapy.

Mapping of the available standards against the regulatory needs for nanomedicines

Appropriate documentary standards and reference materials are crucial building blocks for the development of innovative products. In order to support the emerging sector of nanomedicine, relevant standards must be identified and/or developed before the products will enter into the regulatory approval process. The anticipation of standardization needs requires a good understanding on the regulatory information requirements that can be triggered by the particularities of nanomedicines. However, robust datasets allowing firm conclusions on regulatory demands are not yet available due to a lack of regulatory experience with innovative products. Such a catch-22 situation can only be advanced in an iterative process by monitoring continuously the scientific evidence and by promoting intensive knowledge exchange between all involved stakeholders. In this study, we have compiled information requirements released by regulatory scientists so far and mapped it against available standards that could be of relevance for nanomedicines. Our gap analysis clearly demonstrated that for some endpoints such as drug release/loading and the interaction of nanomedicines with the immune system no standards are available so far. The emerging nanomedicine sector could benefit from cross-sector collaboration and review the suitability of standards that have been developed for nanomaterials used for other industrial applications. Only a concerted action of all parties can lead to a smooth translation of nanomedicines to clinical application and to the market. This is in particular important because nanotechnology-based drug delivery systems are key for the development and implementation of personalized medicine. This article is characterized under: Toxicology and Regulatory Issues in Nanomedicine > Regulatory and Policy Issues in Nanomedicine.

Interactions of Functionalized Multi-Wall Carbon Nanotubes with Giant Phospholipid Vesicles as Model Cellular Membrane System

Carbon Nanotubes (CNTs) are considered alternative materials for the design of advanced drug and gene delivery vectors. However, the mechanism responsible for the cellular membrane intake of CNTs is not well understood. In the present study, we show how multi-walled carbon nanotubes (MWCNTs) owning different surface properties, interact with giant unilamellar vesicles (GUVs), a simple model system for cellular membranes. In particular, we want to address the hydrophilic/hydrophobic interactions between MWCNTs and lipid membranes and the subsequent mechanical properties changes of the systems. In order to elucidate this interaction, we made the following chemical modifications on MWCNTs: oxidized MWCNTs (ox-MWCNTs) displaying reduced hydrophobic surface character, pristine MWCNTs (p-MWCNTs), and alkyl functionalized MWCNTs (alk-MWCNTs) exhibiting enhanced hydrophobic surface properties, were put in contact with GUVs and observed by confocal microscopy. Our observations revealed that the interaction between the CNTs and GUVs depends on the type of chemical functionalization: ox-MWCNTs remain at the membrane interacting with the polar head of the phospholipids, p-MWCNTs internalize GUVs spontaneously, and alk-MWCNTs persist inside the membrane. The mechanical properties of MWCNTs@GUVs systems were measured using the electrodeformation method, which shows an increased bending stiffness (κ) of the GUVs as MWCNTs concentration increases. High concentrations of p-MWCNTs and alk-MWCNTs induced vesicle adhesion; p-MWCNTs produced a considerable reduction in the average size of the GUVs, while alk-MWCNTs form complex stable structures inside the membrane. The statistical analyses of the experimental results are compared with available computer simulations. The picture emerging from our results is that the interaction between GUVs and MWCNTs is due mainly to hydrophobicity.

Toxicological status of nanoparticles: What we know and what we don't know

The field of nanotechnology has grown exponentially during the last few decades, due in part to the use of nanoparticles in many manufacturing processes, as well as their potential as clinical agents for treatment of diseases and for drug delivery. This has created several new avenues by which humans can be exposed to nanoparticles. Unfortunately, investigations assessing the toxicological impacts of nanoparticles (i.e. nanotoxicity), as well as their possible risks to human health and the environment, have not kept pace with the rapid rise in their use. This has created a gap-in-knowledge and a substantial need for more research. Studies are needed to help complete our understanding of the mechanisms of toxicity of nanoparticles, as well as the mechanisms mediating their distribution and accumulation in cells and tissues and their elimination from the body. This review summarizes our knowledge on nanoparticles, including their various applications, routes of exposure, their potential toxicity and risks to human health.

Adsorption mechanism of an antimicrobial peptide on carbonaceous surfaces: A molecular dynamics study

Peptides are versatile molecules with applications spanning from biotechnology to nanomedicine. They exhibit a good capability to unbundle carbon nanotubes (CNT) by improving their solubility in water. Furthermore, they are a powerful drug delivery system since they can easily be uptaken by living cells, and their high surface-to-volume ratio facilitates the adsorption of molecules of different natures. Therefore, understanding the interaction mechanism between peptides and CNT is important for designing novel therapeutical agents. In this paper, the mechanisms of the adsorption of antimicrobial peptide Cecropin A-Magainin 2 (CA-MA) on a graphene nanosheet (GNS) and on an ultra-short single-walled CNT are characterized using molecular dynamics simulations. The results show that the peptide coats both GNS and CNT surfaces through preferential contacts with aromatic side chains. The peptide packs compactly on the carbon surfaces where the polar and functionalizable Lys side chains protrude into the bulk solvent. It is shown that the adsorption is strongly correlated to the loss of the peptide helical structure. In the case of the CNT, the outer surface is significantly more accessible for adsorption. Nevertheless when the outer surface is already covered by other peptides, a spontaneous diffusion, via the amidated C-terminus into the interior of the CNT, was observed within 150 ns of simulation time. We found that this spontaneous insertion into the CNT interior can be controlled by the polarity of the entrance rim. For the positively charged CA-MA peptide studied, hydrogenated and fluorinated rims, respectively, hinder and promote the insertion.

Similar and Differential Canonical Pathways and Biological Processes Associated With Multiwalled Carbon Nanotube and Asbestos-Induced Pulmonary Fibrosis: A 1-Year Postexposure Study

Respiratory exposure to multiwalled carbon nanotubes (MWCNT) or asbestos results in fibrosis; however, the mechanisms to reach this end point may be different. A previous study by our group identified pulmonary effects and significantly altered messenger RNA (mRNA) signaling pathways following exposure to 1, 10, 40, and 80 µg MWCNT and 120 µg crocidolite asbestos on mouse lungs over time at 1-month, 6-month, and 1-year postexposure following pulmonary aspiration. As a continuation to the above study, this current study took an in-depth look at the signaling pathways involved in fibrosis development at a single time point, 1 year, and exposure, 40 µg MWCNT, the lowest exposure at which fibrosis was pathologically evident. The 120 µg asbestos exposure was included to compare MWCNT-induced fibrosis with asbestos-induced fibrosis. A previously validated computational model was used to identify mRNAs with expression profiles matching the fibrosis pathology patterns from exposed mouse lungs. mRNAs that matched the pathology patterns were then input into ingenuity pathway analysis to determine potential signaling pathways and physiological disease functions inherent to MWCNT and asbestos exposure. Both MWCNT and asbestos exposure induced changes in mouse lungs regarding gene expression, cell proliferation, and survival, while MWCNT uniquely induced alterations in pathways involved in oxidative phosphorylation, mitochondrial dysfunction, and transcription. Asbestos exposure produced unique alterations in pathways involved in sustained inflammation. Although typically considered similar due to scale and fiber-like appearance, the different compositional properties inherent to either MWCNT or asbestos may play a role in their ability to induce fibrosis after pulmonary exposure.

Incorporation of Levodopa into Biopolymer Coatings Based on Carboxylated Carbon Nanotubes for pH-Dependent Sustained Release Drug Delivery

Four drug delivery systems were formulated by non-covalent functionalization of carboxylated single walled carbon nanotubes using biocompatible polymers as coating agent (i.e., Tween 20, Tween 80, chitosan or polyethylene glycol) for the delivery of levodopa, a drug used in Parkinson’s disease. The chemical interaction between the coating agent and carbon nanotubes-levodopa conjugate was confirmed by Fourier transform infrared (FTIR) and Raman studies. The drug release profiles were revealed to be dependent upon the type of applied coating material and this could be further adjusted to a desired rate to meet different biomedical conditions. In vitro drug release experiments measured using UV-Vis spectrometry demonstrated that the coated conjugates yielded a more prolonged and sustained release pattern compared to the uncoated conjugate. Cytotoxicity of the formulated conjugates was studied by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay using normal mouse embryonic fibroblast 3T3 cell line. Compared to the non-coated conjugate, the MTT data indicated that the coating procedure improved the biocompatibility of all systems by 34–41% when the concentration used exceeded 100 μg/mL. In conclusion, the comprehensive results of this study suggest that carbon nanotubes-based drug carrier coated with a suitable biomaterial may possibly be a potential nanoparticle system that could facilitate drug delivery to the brain with tunable physicochemical properties.

Carbon nanotubes in the delivery of anticancer herbal drugs

Cancer is estimated to be a significant health problem of the 21st century. The situation gets even tougher when it comes to its treatment using chemotherapy employing synthetic anticancer molecules with numerous side effects. Recently, there has been a paradigm shift toward the adoption of herbal drugs for the treatment of cancer. In this context, a suitable delivery system is principally warranted to deliver these herbal biomolecules specifically at the tumorous site. To achieve this goal, carbon nanotubes (CNTs) have been widely explored to deliver anticancer herbal molecules with improved therapeutic efficacy and safety. This review uniquely expounds the biopharmaceutical, clinical and safety aspects of different anticancer herbal drugs delivered through CNTs with a cross-talk on their outcomes. This review will serve as a one-stop-shop for the readers on various anticancer herbal drugs delivered through CNTs as a futuristic delivery device.

Evaluation of carbon nanotube based copper nanoparticle composite for the efficient detection of agroviruses

We report a biosensor that combines the construction of a three-dimensional nanocomposite with electrochemical methods for the detection of viruses in plants. This is the first report, where carbon nanotubes are used as a conductive frame to anchor highly electrolytic agglomerates of copper nanoparticles to detect agroviruses. Morphological analysis of nanocomposite revealed the presence of carbon nanotubes having a diameter of 50-100nm with copper nanoparticles of 20-100nm, attached in the form of bunches. This material was applied to assess the infection caused by geminiviruses which are a major threat to the cotton plants in Asian and African countries. The hybridization events were studied by monitoring differential pulse voltammetry signals using methylene blue as a redox indicator. In the presence of target DNA, sensor signals decreased from 7×10^-4 to 1×10^-4Ampere. The probe exhibited 97.14% selectivity and the detection limit was found to be 0.01ngμL^-1. The developed biosensor is stable for at least four weeks, losing only 4.3% of the initial signal value. This sensor was able to detect the presence of viruses in sap extracted from cotton leaves, thus providing a promising platform to detect a range of other crops-infecting viruses.

Conjugation of a GM3 lactone mimetic on carbon nanotubes enhances the related inhibition of melanoma-associated metastatic events

Carbon nanotubes conjugated to a mimetic of a melanoma-associated antigen interfere with adhesion, motility, and invasiveness of human melanoma cells.

Targeted dual-mode imaging and phototherapy of tumors using ICG-loaded multifunctional MWCNTs as a versatile platform

ICG-loaded MWCNTs can be synthesized and used as a theranostic platform for targeted dual-mode imaging and phototherapy of tumors.

Silicone Substrate with Collagen and Carbon Nanotubes Exposed to Pulsed Current for MSC Osteodifferentiation

Autologous human adipose tissue-derived mesenchymal stem cells (MSCs) have the potential for clinical translation through their induction into osteoblasts for regeneration. Bone healing can be driven by biophysical stimulation using electricity for activating quiescent adult stem cells. It is hypothesized that application of electric current will enhance their osteogenic differentiation, and addition of conductive carbon nanotubes (CNTs) to the cell substrate will provide increased efficiency in current transmission. Cultured MSCs were seeded and grown onto fabricated silicone-based composites containing collagen and CNT fibers. Chemical inducers, namely, glycerol phosphate, dexamethasone, and vitamin C, were then added to the medium, and pulsatile submilliampere electrical currents (about half mA for 5 cycles at 4 mHz, twice a week) were applied for two weeks. Calcium deposition indicative of MSC differentiation and osteoblastic activity was quantified through Alizarin Red S and spectroscopy. It was found that pulsed current significantly increased osteodifferentiation on silicone-collagen films without CNTs. Under no external current, the presence of 10% (m/m) CNTs led to a significant and almost triple upregulation of calcium deposition. Both CNTs and current parameters did not appear to be synergistic. These conditions of enhanced osteoblastic activities may further be explored ultimately towards future therapeutic use of MSCs.

Cellular responses induced by multi-walled carbon nanotubes: in vivo and in vitro studies on the medicinal leech macrophages

The core characteristics of multi-wall carbon nanotubes (MWCNTs) are impressive and attractive for technology however, since their production and use is steadily increasing, their environmental dispersion could be potentially hazardous to animal and human health. For this reason, the identification of new methods and of reliable models to better understand MWCNT effects is essential. Here we propose the medicinal leech as an alternative model to assess the effects of MWCNTs on immune system. Our previous studies have already demonstrated that in vivo MWCNT treatment induces the activation of leech’s macrophages. Here we will focus on the direct effects of MWCNTs on these cells by isolating and culturing leech's macrophages by means of the consolidated Matrigel technique, followed by MWCNT in vitro treatment. Our results indicate that MWCNT administration causes both the decrease of cell proliferation rate and the increase of the apoptotic rate. Furthermore, since oxidative stress is linked with inflammation, reactive oxygen species has been evaluated confirming that their production rate increases after MWCNT treatment. Our experimental approaches demonstrate the ability of MWCNTs inducing a powerful inflammatory response and confirm that the medicinal leech is a good alternative model to study the possible harmful effects of any nanomaterial.

Nanoparticles as Theranostic Vehicles in Experimental and Clinical Applications-Focus on Prostate and Breast Cancer

Prostate and breast cancer are the second most and most commonly diagnosed cancer in men and women worldwide, respectively. The American Cancer Society estimates that during 2016 in the USA around 430,000 individuals were diagnosed with one of these two types of cancers, and approximately 15% of them will die from the disease. In Europe, the rate of incidences and deaths are similar to those in the USA. Several different more or less successful diagnostic and therapeutic approaches have been developed and evaluated in order to tackle this issue and thereby decrease the death rates. By using nanoparticles as vehicles carrying both diagnostic and therapeutic molecular entities, individualized targeted theranostic nanomedicine has emerged as a promising option to increase the sensitivity and the specificity during diagnosis, as well as the likelihood of survival or prolonged survival after therapy. This article presents and discusses important and promising different kinds of nanoparticles, as well as imaging and therapy options, suitable for theranostic applications. The presentation of different nanoparticles and theranostic applications is quite general, but there is a special focus on prostate cancer. Some references and aspects regarding breast cancer are however also presented and discussed. Finally, the prostate cancer case is presented in more detail regarding diagnosis, staging, recurrence, metastases, and treatment options available today, followed by possible ways to move forward applying theranostics for both prostate and breast cancer based on promising experiments performed until today.

A Carbon Nanotube Optical Sensor Reports Nuclear Entry via a Noncanonical Pathway

Single-walled carbon nanotubes are of interest in biomedicine for imaging and molecular sensing applications and as shuttles for various cargos such as chemotherapeutic drugs, peptides, proteins, and oligonucleotides. Carbon nanotube surface chemistry can be modulated for subcellular targeting while preserving photoluminescence for label-free visualization in complex biological environments, making them attractive materials for such studies. The cell nucleus is a potential target for many pathologies including cancer and infectious diseases. Understanding mechanisms of nanomaterial delivery to the nucleus may facilitate diagnostics, drug development, and gene-editing tools. Currently, there are no systematic studies to understand how these nanomaterials gain access to the nucleus. Herein, we developed a carbon nanotube based hybrid material that elucidate a distinct mechanism of nuclear translocation of a nanomaterial in cultured cells. We developed a nuclear-targeted probe via cloaking photoluminescent single-walled carbon nanotubes in a guanidinium-functionalized helical polycarbodiimide. We found that the nuclear entry of the nanotubes was mediated by the import receptor importin β without the aid of importin α and not by the more common importin α/β pathway. Additionally, the nanotube photoluminescence exhibited distinct red-shifting upon entry to the nucleus, potentially functioning as a reporter of the importin β-mediated nuclear transport process. This work delineates a noncanonical mechanism for nanomaterial delivery to the nucleus and provides a reporter for the study of nucleus-related pathologies.

Applications of Functionalized Carbon Nanotubes for the Therapy and Diagnosis of Cancer

Carbon nanotubes (CNTs) are attractive nanostructures that serve as multifunctional transporters in biomedical applications, especially in the field of cancer therapy and diagnosis. Owing to their easily tunable nature and remarkable properties, numerous functionalizations and treatments of CNTs have been attempted for their utilization as hybrid nano-carriers in the delivery of various anticancer drugs, genes, proteins, and immunotherapeutic molecules. In this review, we discuss the current advances in the applications of CNT-based novel delivery systems with an emphasis on the various functionalizations of CNTs. We also highlight recent findings that demonstrate their important roles in cancer imaging applications, demonstrating their potential as unique agents with high-level ultrasonic emission, strong Raman scattering resonance, and magnetic properties.