Functionalized carbon nanotubes for potential medicinal applications

Properties of ultrathin cholesterol and phospholipid layers surrounding silicon-carbide nanotube: MD simulations

Computer simulation technique was used to study the dynamics of cholesterol and POPC phospholipid molecules forming a thin layer on the surface of the carbon and silicon-carbide nanotubes. Each nanotube was surrounded by an ultra-thin film formed by n lipid molecules, where n varies from 15 to 50. All studies were done for five temperatures, including physiological one (T=260, 285, 310, 335 and 360K). The influence of a nanotube on the dynamics of cholesterol or phospholipid molecules in a layer is presented and discussed. The water is ubiquitous in all biological milieus, where the cholesterol or lipids occur. Thus, simulations were performed in a water environment. Moreover, to show different behavior of lipids in systems with water the results were compared with the samples without it. The dynamical and structural observables, such as the mean square displacement, diffusion coefficient, radial distribution function, and activation energy were calculated to qualitatively investigate the behavior of cholesterol and phospholipid molecules in the layers. We observed remarkable differences between the cholesterol dynamics depending whether the ultrathin film surrounds carbon or silicon-carbide nanotube and whether the water environment appeared.

Multiwall Carbon Nanotube-Induced DNA Damage and Cytotoxicity in Male Human Peripheral Blood Lymphocytes

Carbon nanotubes (CNTs) have been introduced recently as a novel carrier system for both small and large therapeutic molecules. Biotin-functionalized single-wall CNTs have been conjugated with the anticancer agent taxoid using a cleavable linker, and multiwall carbon nanotubes (MWCNTs) conjugated with iron nanoparticles have been efficiently loaded with doxorubicin. The MWCNTs are effective transporters for biological macromolecules and drugs to target cells and tissues, thereby attracting the attention of the biomedical industry. Administrating MWCNTs for medical application invariably involves intravenous administration and ultimate contact with human peripheral blood lymphocytes (HPBLs), yet toxicological studies on the effect of MWCNTs on HPBLs are lacking. Accordingly, this study evaluated the cytotoxic and genotoxic effects of MWCNTs on healthy male HPBLs. Healthy male HPBLs were treated with MWCNTs at 3 different concentrations (12.5, 25, and 50 μg/mL) for 48 hours. Under these conditions, the MWCNTs induced significant cell growth retardation, DNA damage, and cytotoxicity. The MWCNT-treated HPBLs also exhibited an increased intracellular reactive oxygen species level during the experimental period, which leads to cell damage and death, proliferation inhibition, DNA damage, and an inflammatory response.

Functionalized Multiwalled Carbon Nanotubes as Carriers of Ruthenium Complexes to Antagonize Cancer Multidrug Resistance and Radioresistance

Multidrug resistance and radioresistance are major obstacles for successful cancer therapy. Due to the unique characteristics of high surface area, improved cellular uptake, and the possibility to be easily bound with therapeutics, carbon nanotubes (CNTs) have attracted increasing attention as potential nanodrug delivery systems. In this study, a CNT-based radiosensitive nanodrug delivery system was rationally designed to antagonize the multidrug resistance in hepatocellular carcinoma. The nanosystem was loaded with a potent anticancer ruthenium polypyridyl complex (RuPOP) via π-π interaction and formation of a hydrogen bond. The functionalized nanosystem (RuPOP@MWCNTs) enhanced the cellular uptake of RuPOP in liver cancer cells, especially drug-resistant R-HepG2 cells, through endocytosis. Consistently, the selective cellular uptake endowed the nanosystem amplified anticancer efficacy against R-HepG2 cells but not in normal cells. Interestingly, RuPOP@MWCNTs significantly enhanced the anticancer efficacy of clinically used X-ray against R-HepG2 cells through induction of apoptosis and G0/G1 cell cycle arrest, with the involvement of ROS overproduction, which activated several downstream signaling pathways, including DNA damage-mediated p53 phosphorylation, activation of p38, and inactivation of AKT and ERK. Moreover, the nanosystem also effectively reduces the toxic side effects of loaded drugs and prolongs the blood circulation in vivo. Taken together, the results demonstrate the rational design of functionalized carbon nanotubes and their application as effective nanomedicine to overcome cancer multidrug resistance.

Multifunctional hybrid-carbon nanotubes: new horizon in drug delivery and targeting

Carbon nanotubes (CNTs) have emerged as an intriguing nanotechnological tool for numerous biomedical applications including biocompatible modules for the bioactives delivery ascribed to their unique properties, such as greater loading efficiency, biocompatibility, non-immunogenicity, high surface area and photoluminescence, that make them ideal candidate in pharmaceutical and biomedical science. The design of multifunctional hybrid-CNTs for drug delivery and targeting may differ from the conventional drug delivery system. The conventional nanocarriers have few limitations, such as inappropriate availability of surface-chemical functional groups for conjugation, low entrapment/loading efficiency as well as stability as per ICH guidelines with generally regarded as safe (GRAS) prominences. The multifunctional hybrid-CNTs will sparked and open a new door for researchers, scientist of the pharmaceutical and biomedical arena. This review summarizes the vivid aspects of CNTs like characterization, supramolecular chemistry of CNTs-dendrimer, CNTs-nanoparticles, CNTs-quantum dots conjugate for delivery of bioactives, not discussed so far.

Cationic Liposome- Multi-Walled Carbon Nanotubes Hybrids for Dual siPLK1 and Doxorubicin Delivery In Vitro

Purpose

To formulate f-MWNTs-cationic liposome hybrids for the simultaneous delivery of siPLK1 and doxorubicin to cancer cells.

Method

f-MWNTs-cationic liposome hybrids were prepared by the thin film hydration method where the lipid film was hydrated with 100 μg/ml or 1 mg/ml of ox-MWNTs-NH₃⁺ or MWNTs-NH₃⁺ in 5% dextrose. siRNA complexation and protection ability was determined by agarose gel electrophoresis. f-MWNTs and liposome interaction was evaluated using Nile Red (NR) fluorescence spectroscopy. Cellular uptake in A549 cells was assessed by flow cytometry. Silencing of target proteins was determined by Luciferase and MTT assays. Sub-G1 analysis was performed to evaluate apoptosis following co-delivery of siPLK1 and Doxorubicin (Dox).

Results

Zeta potential and siRNA complexation profile obtained for all hybrids were comparable to those achieved with cationic liposomes. ox-MWNTs-NH₃⁺ showed greater extent of interaction with cationic liposomes compared to MWNTs-NH₃⁺. ox-MWNTs-NH₃⁺ was able to protect siRNA from nuclease-mediated degradation. Enhanced cellular uptake of both the carrier and loaded siRNA in A549 cell, were observed for this hybrid compared to the liposomal carrier. A synergistic pro-apoptotic effect was obtained when siPLK1 silencing was combined with doxorubicin treatment for the hybrid:siRNA complexes compared to the lipoplexes, in A549 cells in vitro.

Conclusions

f-MWNTs-cationic liposome hybrid designed in this study can serve as a potential vehicle for the co-delivery of siRNA and cytotoxic drugs to cancer cells in vitro.

Electronic supplementary material

The online version of this article (doi:10.1007/s11095-015-1707-1) contains supplementary material, which is available to authorized users.

Bucky Tubes Induce Oxidative Stress Mediated Cell Death in Human Lung Cells

Unique physicochemical properties of carbon nanomaterials (CNMs) have opened a new era for therapeutics and diagnosis (known as theranostics) of various diseases. This exponential increase in application makes them important for toxicology studies. The present study was aimed at exploring the toxic potential of one of the CNMs, that is, bucky tubes (BTs), in human lung adenocarcinoma (A549) cell line. BTs were characterised by electron microscopy (TEM), dynamic light scattering (DLS), Fourier transform spectroscopy (FTIR), and X-ray diffraction (XRD). Flow cytometric study showed a concentration and time dependent increase in intracellular internalization as well as reduction in cell viability upon exposure to BTs. However, a significant increase in intracellular reactive oxygen species (ROS) production was observed as evident by increased fluorescence intensity of 2′,7′-dichlorofluorescein (DCF). BTs induced oxidative stress in cells as evident by depletion in glutathione with concomitant increase in lipid peroxidation with increasing concentrations. A significant increase in micronucleus formation and apoptotic cell population and loss of mitochondrial membrane potential (MMP) as compared to control were observed. Moreover, in the present study, BTs were found to be mild toxic and it is encouraging to conclude that BTs having outer diameter in the range of 7–12 nm and length 0.5–10 μm can be used for theranostics.

Filling of carbon nanotubes and nanofibres

The reliable production of carbon nanotubes and nanofibres is a relatively new development, and due to their unique structure, there has been much interest in filling their hollow interiors. In this review, we provide an overview of the most common approaches for filling these carbon nanostructures. We highlight that filled carbon nanostructures are an emerging material for biomedical applications.

Carbon nanotubes activate macrophages into a M1/M2 mixed status: recruiting naïve macrophages and supporting angiogenesis

The potential of carbon nanotubes (CNTs) in medical applications has been attracting constant research interest as well as raising concerns related to toxicity. The immune system serves as the first line of defense against invasion. In this work, interactions of oxidized multiwalled carbon nanotubes (MWCNT) with macrophages were investigated to unravel the activation profile of macrophages, using cytokine array, ELISA assay, transwell assay, confocal microscopy, and reactive oxygen species examination. Results show that MWCNT initiate phagocytosis of macrophages and upregulate CD14, CD11b, TLR-4/MD2, and CD206, which does not alter the MHCII expression of the macrophages. The macrophages engulfing MWCNT (MWCNT-RAW) secrete a large amount of MIP-1α and MIP-2 to recruit naïve macrophages and produce angiogenesis-related cytokines MMP-9 and VEGF, while inducing much lower levels of proinflammatory cytokines than those activated by LPS. In conclusion, MWCNT activate macrophages into a M1/M2 mixed status, which allows the cells to recruit naïve macrophages and support angiogenesis.

Multi-walled carbon nanotubes promote cementoblast differentiation and mineralization through the TGF-β/Smad signaling pathway

Excretion of cementum by cementoblasts on the root surface is a process indispensable for the formation of a functional periodontal ligament. This study investigated whether carboxyl group-functionalized multi-walled carbon nanotubes (MWCNT-COOH) could enhance differentiation and mineralization of mammalian cementoblasts (OCCM-30) and the possible signaling pathway involved in this process. Cementoblasts were incubated with various doses of MWCNT-COOH suspension. Cell viability was detected, and a scanning electron microscopy (SEM) observed both the nanomaterials and the growth of cells cultured with the materials. Alizarin red staining was used to investigate the formation of calcium deposits. Real-time PCR and western blot were used to detect cementoblast differentiation and the underlying mechanisms through the expression of the osteogenic genes and the downstream effectors of the TGF-β/Smad signaling. The results showed that 5 µg/mL MWCNT-COOH had the most obvious effects on promoting differentiation without significant toxicity. Alp, Ocn, Bsp, Opn, Col1 and Runx2 gene expression was up-regulated. Smad2 and Smad3 mRNA was up-regulated, while Smad7 was first down-regulated on Day 3 and later up-regulated on Day 7. The elevated levels of phospho-Smad2/3 were also confirmed by western blot. In sum, the MWCNT-COOH promoted cementoblast differentiation and mineralization, at least partially, through interactions with the TGF-β/Smad pathway.

Advances in the biomedical application of polymer-functionalized carbon nanotubes

Water soluble carbon nanotubes as multivalent nanomaterials for biomedical applications have been discussed.

Comparative assessment of the in vitro toxicity of some functionalized carbon nanotubes and fullerenes

Carbon nanotubes and fullerenes with different surface coatings are evaluated for their potential cytotoxicity on a panel of cell lines.

Carboxylated short single-walled carbon nanotubes but not plain and multi-walled short carbon nanotubes show in vitro genotoxicity

Long carbon nanotubes (CNTs) resemble asbestos fibers due to their high length to diameter ratio and they thus have genotoxic effects. Another parameter that might explain their genotoxic effects is contamination with heavy metal ions. On the other hand, short (1-2 µm) CNTs do not resemble asbestos fibers, and, once purified from contaminations, they might be suitable for medical applications. To identify the role of fiber thickness and surface properties on genotoxicity, well-characterized short pristine and carboxylated single-walled (SCNTs) and multi-walled (MCNTs) CNTs of different diameters were studied for cytotoxicity, the cell's response to oxidative stress (immunoreactivity against hemoxygenase 1 and glutathione levels), and in a hypoxanthine guanine phosphoribosyltransferase (HPRT) assay using V79 chinese hamster fibroblasts and human lung adenocarcinoma A549 cells. DNA repair was demonstrated by measuring immunoreactivity against activated histone H2AX protein. The number of micronuclei as well as the number of multinucleated cells was determined. CNTs acted more cytotoxic in V79 than in A549 cells. Plain and carboxylated thin (<8 nm) SCNTs and MCNTs showed greater cytotoxic potential and carboxylated CNTs showed indication for generating oxidative stress. Multi-walled CNTs did not cause HPRT mutation, micronucleus formation, DNA damage, interference with cell division, and oxidative stress. Carboxylated, but not plain, SCNTs showed indication for in vitro DNA damage according to increase of H2AX-immunoreactive cells and HPRT mutation. Although short CNTs presented a low in vitro genotoxicity, functionalization of short SCNTs can render these particles genotoxic.

Carbon nanotubes: potential medical applications and safety concerns

Carbon nanotubes (CNTs) have unique atomic structure, as well as outstanding thermal, mechanical, and electronic properties, making them extremely attractive materials for several different applications. Many research groups are focusing on biomedical applications of carbon-based nanomaterials, however the application of CNTs to the biomedical field is not developing as fast as in other areas. While CNTs-based products are already being used in textiles, polymer matrices to strengthen materials, sports articles, microelectronics, energy storage, etc., medicinal products and medical devices for in vivo application based on CNTs have not been commercialized yet. However, CNTs for biomedical application, i.e., CNTs conjugated to siRNA for cancer therapy, or CNTs for imaging of colorectal cancer and many other products may enter clinical trials in the next years. Concerns related to the toxicity of CNTs must be overcome in order to have these products commercialized in a near future. This article reviews emerging biomedical applications of CNTs, specifically for therapy. It also deals with challenges associated with possible medical applications of CNTs, such as their not fully understood toxicological profile in the human body.

Toxicity of single-walled carbon nanotubes

Carbon nanotubes (CNTs) are an important class of nanomaterials, which have numerous novel properties that make them useful in technology and industry. Generally, there are two types of CNTs: single-walled nanotubes (SWNTs) and multi-walled nanotubes. SWNTs, in particular, possess unique electrical, mechanical, and thermal properties, allowing for a wide range of applications in various fields, including the electronic, computer, aerospace, and biomedical industries. However, the use of SWNTs has come under scrutiny, not only due to their peculiar nanotoxicological profile, but also due to the forecasted increase in SWNT production in the near future. As such, the risk of human exposure is likely to be increased substantially. Yet, our understanding of the toxicological risk of SWNTs in human biology remains limited. This review seeks to examine representative data on the nanotoxicity of SWNTs by first considering how SWNTs are absorbed, distributed, accumulated and excreted in a biological system, and how SWNTs induce organ-specific toxicity in the body. The contradictory findings of numerous studies with regards to the potential hazards of SWNT exposure are discussed in this review. The possible mechanisms and molecular pathways associated with SWNT nanotoxicity in target organs and specific cell types are presented. We hope that this review will stimulate further research into the fundamental aspects of CNTs, especially the biological interactions which arise due to the unique intrinsic characteristics of CNTs.

Multifunctional PEGylated multiwalled carbon nanotubes for enhanced blood pool and tumor MR imaging

Long-circulating multifunctional Gd(III)-loaded multiwalled carbon nanotubes (MWCNTs) modified with polyethylene glycol are designed and synthesized. The formed MWCNTs are water-dispersible, stable, and have good cytocompatibility and antifouling property. With the low r 2 /r 1 relaxivity ratio and relatively long blood circulation time, the multifunctional MWCNTs are able to be used as a platform for enhanced blood pool and tumor MR imaging.

Oxygen-carbon nanotubes as a chemotherapy sensitizer for paclitaxel in breast cancer treatment

Objective

To study the in vivo and in vitro effects of adding oxygen carbon nanotubes (CNTs) to chemotherapy for breast cancer.

Methods

MCF-7 and SK-BR-3 breast cancer cells were co-cultured with paclitaxel and then exposed to oxygen-CNTs under hypoxic conditions. Cell proliferation, viability, and apoptosis rate were analyzed. Hypoxia-inducible factor-1 alpha (HIF-1α) expression was measured using reverse transcription-polymerase chain reaction (RT-PCR) and western blot. Nude mice were used as a human breast cancer model to explore the impact of oxygen-CNTs on the in vivo chemotherapeutic effect of paclitaxel.

Results

Oxygen-CNTs had no significant effects on the growth of breast cancer cells under normoxia and hypoxia. However, in the hypoxic environment, oxygen-CNTs significantly enhanced the inhibitory effect of paclitaxel on cell proliferation, as well as the apoptosis rate. Under hypoxia, downregulation of HIF-1α and upregulation of caspase-3, caspase-8, caspase-9, LC3 and Beclin-1 were observed when paclitaxel was combined with oxygen-CNT. Furthermore, addition of oxygen-CNTs to chemotherapy was found to significantly reduce tumor weight in the tumor-bearing mice model.

Conclusions

Oxygen-CNTs can significantly increase the chemotherapeutic effect of paclitaxel on breast cancer cells. Oxygen-CNTs may be a potential chemosensitizer in breast cancer therapy.

Delivery of nitric oxide to the interior of mammalian cell by carbon nanotube: MD simulation

Computer simulations have been performed to study the nanoindentation of phospholipid bilayer by the single-walled armchair carbon nanotube, filled with the nitric oxide molecules. The process has been simulated by means of molecular dynamics (MD) technique at physiological temperature T = 310 K with a constant pulling velocity of the nanotube. The force acting on the nanotube during membrane penetration has been calculated. We show that the indentation by carbon nanotube does not permanently destroy the membrane structure (self-sealing of the membrane occurs). The mobility of nitric oxide molecules during the membrane nanoindentation is discussed.

Tuning cell autophagy by diversifying carbon nanotube surface chemistry

The induction of autophagy by nanoparticles causes nanotoxicity, but appropriate modulation of autophagy by nanoparticles may have therapeutic potential. Multiwalled carbon nanotubes (MWCNTs) interact with cell membranes and membrane-associated molecules before and after internalization. These interactions alter cellular signaling and impact major cell functions such as cell cycle, apoptosis, and autophagy. In this work, we demonstrated that MWCNT-cell interactions can be modulated by varying densely distributed surface ligands on MWCNTs. Using a fluorescent autophagy-reporting cell line, we evaluated the autophagy induction capability of 81 surface-modified MWCNTs. We identified strong and moderate autophagy-inducing MWCNTs as well as those that did not induce autophagy. Variation of the surface ligand structure of strong autophagy nanoinducers led to the induction of different autophagy-activating signaling pathways, presumably through their different interactions with cell surface receptors.

Carbon nanotubes hybrid hydrogels in drug delivery: a perspective review

The use of biologics, polymers, silicon materials, carbon materials, and metals has been proposed for the preparation of innovative drug delivery devices. One of the most promising materials in this field are the carbon-nanotubes composites and hybrid materials coupling the advantages of polymers (biocompatibility and biodegradability) with those of carbon nanotubes (cellular uptake, stability, electromagnatic, and magnetic behavior). The applicability of polymer-carbon nanotubes composites in drug delivery, with particular attention to the controlled release by composites hydrogel, is being extensively investigated in the present review.

Green silver nanobioarchitectures with amplified antioxidant and antimicrobial properties

A novel, simple and cost-effective bottom-up approach was developed to achieve antioxidant and antimicrobial biohybrids based on biomimetic membranes, phyto-nanosilver and single-walled carbon nanotubes.

Carbon nanomaterials as new tools for immunotherapeutic applications

The possibility to exploit carbon-based nanostructures such as carbon nanotubes and graphene as immunotherapeutic agents has interesting future prospects. In particular, their applications for anticancer treatment, imaging and vaccine development, together with their immunomodulator properties are highlighted.

Nanomaterials based electrochemical sensors for biomedical applications

A growing variety of sensors have increasingly significant impacts on everyday life. Key issues to take into consideration toward the integration of biosensing platforms include the demand for minimal costs and the potential for real time monitoring, particularly for point-of-care applications where simplicity must also be considered. In light of these developmental factors, electrochemical approaches are the most promising candidate technologies due to their simplicity, high sensitivity and specificity. The primary focus of this review is to highlight the utility of nanomaterials, which are currently being studied for in vivo and in vitro medical applications as robust and tunable diagnostic and therapeutic platforms. Highly sensitive and precise nanomaterials based biosensors have opened up the possibility of creating novel technologies for the early-stage detection and diagnosis of disease related biomarkers. The attractive properties of nanomaterials have paved the way for the fabrication of a wide range of electrochemical sensors that exhibit improved analytical capacities. This review aims to provide insights into nanomaterials based electrochemical sensors and to illustrate their benefits in various key biomedical applications. This emerging discipline, at the interface of chemistry and the life sciences, offers a broad palette of opportunities for researchers with interests that encompass nanomaterials synthesis, supramolecular chemistry, controllable drug delivery and targeted theranostics in biology and medicine.

Facile oxidation of superaligned carbon nanotube films for primary cell culture and genetic engineering

A material that can simultaneously support mammalian cell growth and preserve their physiological function is highly desirable in biomedical research. To meet this need, we fabricated superaligned carbon nanotube (SACNT) thin films and modified their surface using a convenient oxidization method. Our analysis demonstrated that the physical properties of oxidized SACNT films became more biocompatible. It supported the attachment and growth of primary mouse fibroblast cells as well as neonatal rat cardiomyocytes. Moreover, when cultured on oxidized SACNT films, neonatal rat cardiomyocytes spread normally and displayed calcium influx. Finally, we showed that, as oxidized SACNT films retained their electrical conductivity, attached cells can be electrotransfected in situ on them. Strong and prolonged expression of green fluorescence proteins (GFPs) or red fluorescence proteins (RFPs) was observed upon cell electroporation on oxidized SACNT films. In summary, our results provide evidence that simple oxidation greatly improved the biocompatibility of carbon nanotube films, which becomes more suitable for future applications in cell and genetic engineering.

Nanoparticle systems as tools to improve drug delivery and therapeutic efficacy

Nanoparticle-based drug delivery systems are appealing because, among other properties, they are easily manufactured and have the capacity to encapsulate a wide variety of drugs, many of which are not directly miscible with water. This review classifies nanoparticles into three broad categories based upon material composition: bio-inspired systems, synthetic systems, and inorganic systems. Each has distinct properties suitable for drug delivery applications, including their structure, composition, and pharmacokinetics (including clearance and uptake mechanisms), making each uniquely suitable for certain types of drugs. Furthermore, nanoparticles can be customized, making them ideal for a variety of applications. Advantages and disadvantages of the different systems are discussed. Strategies for improving nanoparticle efficacy include adding targeting agents on the nanoparticle surface, altering the degradation profile to control drug release, or PEGylating the surface to increase circulation times and reduce immediate clearance by the kidneys. The future of nanoparticle systems seems to be focused on further improving overall patient outcome by increasing delivery accuracy to the target area.

Determinants of carbon nanotube toxicity

In the last few years questions have been raised regarding the potential toxicity of carbon nanotubes (CNTs) to humans and environment. It is believed that the physico-chemical characteristics of these materials are key determinants of CNT interaction with living organisms, and hence determine their toxicity. As for other nanomaterials, the most important of these characteristics are the length, diameter, surface area, tendency to agglomerate, bio-durability, presence and nature of catalyst residues as well as chemical functionalization of the CNT. This review highlights the recent advancements in the understanding of the CNT properties which are essential in determining CNT toxicity. Hence the focus is on CNT dimensions, surface properties, bio-durability and corona formation as these fields have evolved greatly in recent years. A deeper understanding of these events and their underlying mechanisms could provide a molecular explanation of the biological and physiological responses following CNT administration and therefore help in the development of safe by design materials.

Endowing carbon nanotubes with biological and biomedical properties by chemical modifications

The scope of nanotechnology is gaining importance in biology and medicine. Carbon nanotubes (CNTs) have emerged as a promising tool due to their unique properties, high specific surface area, and capacity to cross biological barriers. These properties offer a variety of opportunities for applications in nanomedicine, such as diagnosis, disease treatment, imaging, and tissue engineering. Nevertheless, pristine CNTs are insoluble in water and in most organic solvents; thereby functionalization of their surface is necessary to increase biocompatibility. Derivatization of CNTs also gives the possibility to conjugate different biological and bioactive molecules including drugs, proteins, and targeting ligands. This review focuses on the chemical modifications of CNTs that have been developed to impart specific properties for biological and medical purposes. Biomolecules can be covalently grafted or non-covalently adsorbed on the nanotube surface. In addition, the inner core of CNTs can be exploited to encapsulate drugs, nanoparticles, or radioactive elements.

Carbon nanotubes: applications in pharmacy and medicine

Carbon nanotubes (CNTs) are allotropes of carbon, made of graphite and constructed in cylindrical tubes with nanometer in diameter and several millimeters in length. Their impressive structural, mechanical, and electronic properties are due to their small size and mass, their strong mechanical potency, and their high electrical and thermal conductivity. CNTs have been successfully applied in pharmacy and medicine due to their high surface area that is capable of adsorbing or conjugating with a wide variety of therapeutic and diagnostic agents (drugs, genes, vaccines, antibodies, biosensors, etc.). They have been first proven to be an excellent vehicle for drug delivery directly into cells without metabolism by the body. Then other applications of CNTs have been extensively performed not only for drug and gene therapies but also for tissue regeneration, biosensor diagnosis, enantiomer separation of chiral drugs, extraction and analysis of drugs and pollutants. Moreover, CNTs have been recently revealed as a promising antioxidant. This minireview focuses the applications of CNTs in all fields of pharmacy and medicine from therapeutics to analysis and diagnosis as cited above. It also examines the pharmacokinetics, metabolism and toxicity of different forms of CNTs and discusses the perspectives, the advantages and the obstacles of this promising bionanotechnology in the future.

Nicotinamide-functionalized multiwalled carbon nanotubes increase insulin production in pancreatic beta cells via MIF pathway

Recent data in the literature support the role of nicotinamide (NA) as a pharmacologic agent that stimulates pancreatic beta-cells to produce insulin in vitro. There are data showing that carbon nanotubes may be useful in initiating and maintaining cellular metabolic responses. This study shows that administration of multiwalled carbon nanotubes (MWCNTs) functionalized with nicotinamide (NA-MWCNTs) leads to significant insulin production compared with individual administration of NA, MWCNTs, and a control solution. Treatment of 1.4E7 cells for 30 minutes with NA-MWCNTs at concentrations ranging from 1 mg/L to 20 mg/L resulted in significantly increased insulin release (0.18 ± 0.026 ng/mL for 1 mg/L, 0.21 ± 0.024 ng/mL for 5 mg/L, and 0.27 ± 0.028 ng/mL for 20 mg/L). Thus, compared with cells treated with NA only (0.1 ± 0.01 ng/mL for 1 mg/L, 0.12 ± 0.017 ng/mL for 5 mg/L, and 0.17 ± 0.01 ng/mL for 20 mg/L) we observed a significant positive effect on insulin release in cells treated with NA-MWCNTs. The results were confirmed using flow cytometry, epifluorescence microscopy combined with immunochemistry staining, and enzyme-linked immunosorbent assay techniques. In addition, using immunofluorescence microscopy techniques, we were able to demonstrate that MWCNTs enhance insulin production via the macrophage migration inhibitory factor pathway. The application and potential of NA combined with MWCNTs as an antidiabetic agent may represent the beginning of a new chapter in the nanomediated treatment of diabetes mellitus.

Study of cytotoxic effects of single-walled carbon nanotubes functionalized with different chemical groups on human MCF7 cells

Functionalization is an important technique to increase the solubility and biocompatibility of single-wall carbon nanotubes (SWCNTs). In this study, we investigated the cytotoxicity of four types of SWCNTs functionalized with hydroxyl, amino, carboxyl and polyethyleneglycol on MCF7 cells. These functionalized SWCNTs (f-SWCNTs) have insignificant effects on mitochondrial activity and ROS production in MCF7 cells at all test concentrations. However, explicit results revealed that all the tested f-SWCNTs could cause changes of cell morphology, induce cell membrane damage, decrease cell adhesion, and increase cell apoptosis. Therefore, this study shows the potential side effects of f-SWCNTs accompanying with the increase of dispersibility and stability in environment or serum (to prevent their aggregation), and highlights the need for further research to examine the potential toxicity of f-SWCNTs before they are used in the environmental and biomedical fields.

Protective role of functionalized single walled carbon nanotubes enhance ex vivo expansion of hematopoietic stem and progenitor cells in human umbilical cord blood

In this study, carboxylic acid functionalized single walled carbon nanotubes (f-SWCNT-COOH) was shown to support the viability and ex vivo expansion of freeze-thawed, non-enriched hematopoietic stem and progenitor cells (HSPC) in human umbilical cord blood-mononucleated cells (UCB-MNC). Our in vitro experiments showed that f-SWCNT-COOH increased the viability of the CD45(+) cells even without cytokine stimulation. It also reduced mitochondrial superoxides and caspase activity in CD45(+) cells. f-SWCNT-COOH drastically reduced the proportions of CD45(-) cells in the non-enriched UCB-MNC. Phenotypic expression analysis and functional colony forming units (CFU) showed significant ex vivo expansion of HSPC, particularly of CD45(+)CD34(+)CD38(-) population and granulocyte-macrophage (GM) colonies, in f-SWCNT-COOH augmented cultures supplemented with basal cytokines. In vivo data suggested that f-SWCNT-COOH expanded UCB-MNC could repopulate immunodeficient mice models with minimal acute or sub-acute symptoms of graft-versus-host disease (GVHD) and f-SWCNT-COOH dependent toxicity.

FROM THE CLINICAL EDITOR

In this paper a novel method is presented by using single wall functionalized carbon nanotubes to enhance viability and ex vivo expansion of freeze-thawed, non-enriched hematopoietic stem and progenitor cells in human umbilical cord blood -mononucleated cells. Detailed data is presented about enhanced viability, including improved repopulation of immunodeficient mice models with minimal acute or sub-acute symptoms of graft-versus-host disease.

PEGylated single-walled carbon nanotubes as nanocarriers for cyclosporin A delivery

Single-walled carbon nanotubes (SWCNTs) have attracted the attention of many researchers due to their remarkable physicochemical features and have been found to be a new family of nanovectors for the delivery of therapeutic molecules. The ability of these nanostructures to load large amounts of drug molecules on their outer surface has been considered as the main advantage by many investigators. Here, we report the development of a PEGylated SWCNT-mediated delivery system for cyclosporin A (CsA) as a potent immunosuppressive agent. The available OH group in the CsA structure was first linked to a bi-functional linker (i.e., succinic anhydride) in order to provide a COOH terminal group. CsA succinylation process was optimized by using the modified simplex method. The resulting compound, CsA-CO-(CH(2))(2)-COOH, was then grafted onto the exterior surface of SWCNTs, previously PEGylated with phospholipid-PEG(5000)-NH(2) conjugates, through the formation of an amide bond with the free amine group of PEGylated SWCNTs. Drug loading, stability of the PEGylated SWCNT-CsA complex, and in vitro release of the drug were evaluated. Loading efficiencies of almost 72% and 68% were achieved by UV spectrophotometry and elemental analysis methods, respectively. It was observed that 57.3% of cyclosporine was released from CsA-Pl-PEG(5000)-SWCNTs after 3 days. In this investigation, we conjugated CsA to an amine-terminated phospholipid-polyethylene glycol chain attached on SWCNTs via a cleavable ester bond and demonstrated the possible potential of PEGylated SWCNT-based systems for CsA delivery.

Intravenously delivered graphene nanosheets and multiwalled carbon nanotubes induce site-specific Th2 inflammatory responses via the IL-33/ST2 axis

Carbon-based nanomaterials (CBN), such as graphene nanosheets (GNS) and multiwalled carbon nanotubes (MWCNT), have been proposed for potential nanomedicine applications such as biomedical devices and carriers for drug delivery. However, our current understanding regarding the systemic toxicity of these CBN through intravenous (iv) injection is limited. In this study, we compare the immune response resulting from GNS and MWCNT exposure. We hypothesize that iv administration of GNS and MWCNT would result in divergent systemic inflammatory responses due to physicochemical differences between these two CBN. In the lungs of C57BL/6 mice, GNS actuate a Th2 immune response 1 day following iv administration, which consists of neutrophilic influx and a significant increase in interleukin (IL)-5, IL-13, IL-33, and its soluble receptor (sST2) in the bronchoalveolar lavage fluid. MWCNT elicited a significant increase in the messenger ribonucleic acid expression of cytokines in the spleen including IL-4 and IL-33, which are associated with an increase in splenic cell differentiation (CD)4⁺ and CD8⁺ T-cells in C57BL/6 mice following iv injection. The observed Th2 responses in both the lung and spleen are absent in ST2^−/− mice administrated GNS or MWCNT, suggesting a critical role for IL-33. In conclusion, the use of GNS or MWCNT as nanocarriers for drug delivery may result in Th2 immune responses that are mediated through the IL-33/ST2 axis and therefore may promote adverse allergic reactions.

Immunotoxicological impact of engineered nanomaterial exposure: mechanisms of immune cell modulation

Abstract Engineered nanomaterials (ENMs) are increasingly being utilized in many consumer products and various medical applications, thereby leading to the potentiality of increased human exposures. Assessment of the adverse effects on the immune system is an important component for evaluating the overall health and safety of ENM. Tasked with eliminating pathogens and removing cancerous cells, the immune system is constantly functioning to maintain homeostasis. Small modifications to the immune system, which may occur following ENM exposure, could lead to impaired protection or an inappropriate immune response resulting in autoimmunity and damage to the host. This review seeks to survey and evaluate the current literature to better understand the impact of ENM exposure on cells critical to the innate and adaptive immune systems.