Single-walled carbon nanotubes-mediated in vivo and in vitro delivery of siRNA into antigen-presenting cells

Smart nanoparticles for cancer therapy

Smart nanoparticles, which can respond to biological cues or be guided by them, are emerging as a promising drug delivery platform for precise cancer treatment. The field of oncology, nanotechnology, and biomedicine has witnessed rapid progress, leading to innovative developments in smart nanoparticles for safer and more effective cancer therapy. In this review, we will highlight recent advancements in smart nanoparticles, including polymeric nanoparticles, dendrimers, micelles, liposomes, protein nanoparticles, cell membrane nanoparticles, mesoporous silica nanoparticles, gold nanoparticles, iron oxide nanoparticles, quantum dots, carbon nanotubes, black phosphorus, MOF nanoparticles, and others. We will focus on their classification, structures, synthesis, and intelligent features. These smart nanoparticles possess the ability to respond to various external and internal stimuli, such as enzymes, pH, temperature, optics, and magnetism, making them intelligent systems. Additionally, this review will explore the latest studies on tumor targeting by functionalizing the surfaces of smart nanoparticles with tumor-specific ligands like antibodies, peptides, transferrin, and folic acid. We will also summarize different types of drug delivery options, including small molecules, peptides, proteins, nucleic acids, and even living cells, for their potential use in cancer therapy. While the potential of smart nanoparticles is promising, we will also acknowledge the challenges and clinical prospects associated with their use. Finally, we will propose a blueprint that involves the use of artificial intelligence-powered nanoparticles in cancer treatment applications. By harnessing the potential of smart nanoparticles, this review aims to usher in a new era of precise and personalized cancer therapy, providing patients with individualized treatment options.

4',7-dihydroxyflavone conjugated carbon nanotube formulation demonstrates improved efficacy against Leishmania parasite

One of the global problems of rising concern is the spread of the neglected tropical disease, leishmaniasis. There are several drugs used for the treatment of the disease but the repertoire of drugs has drawbacks like toxicity and low therapeutic value. Considering the need for new drugs, we studied the synthesis of 4',7-dihydroxyflavone conjugated multi-walled carbon nanotubes (47DHF-MWCNTs) and evaluated their anti-leishmanial activity against Leishmania donovani. The compound 47DHF was conjugated to the acid oxidized MWCTNs by Steglich esterification. The synthesized 47DHF-MWCNTs were characterized by UV spectroscopy, and, from the zeta value of 35 mV, they were found to be stable. 47DHF-MWCNTs possessed 84% drug loading efficiency and 63% cumulative drug release at intra-macrophage pH of 5.8. Moreover, the evaluation of 47DHF-MWCNTs for activity showed an IC50 value of 0.051 ± 0.01 μg/ml and 0.072 ± 0.01 μg/ml against the promastigote and amastigote form, respectively. 47DHF-MWCNTs exhibited an infectivity index of 42 and selectivity index of 95, suggesting the activity of 47DHF-MWCNTs against intracellular amastigotes in the study. The 47DHF-MWCNTs also had low cytotoxicity towards macrophage cells. Fascinatingly, the 47DHF-MWCNTs treatment causes a high accumulation of ROS in the promastigotes suggesting the mechanism of anti-leishmanial activity to be ROS mediated. Summarizing from our results, we propose for the first time a novel 47DHF conjugated MWCNTs capable of anti-leishmanial activity with lower cytotoxicity that has a huge potential to be a formulation against leishmaniasis.

PEGylated single-walled carbon nanotubes as co-adjuvants enhance expression of maturation markers in monocyte-derived dendritic cells

Aim: This study investigated the application of phospholipid-PEGylated single-walled carbon nanotubes (PL-PEG-SWCNTs) as a safe co-adjuvant for the commercial recombinant hepatitis B virus vaccine to enhance induction of monocyte-derived dendritic cells (MDDCs) differentiation and activation in vitro as an immune response initiator cell to prompt a long-term immune response after a single dose injection. Methods: Immature MDDCs were exposed to PL-PEG-SWCNTs alone and in combination with hepatitis B vaccine. Results & conclusion: Study results confirm the enhanced expression of maturation markers in human immature MDDCs after PL-PEG-SWCNT exposure. The results suggest that PL-PEG-SWCNT is an efficient co-adjuvant for the commercial recombinant hepatitis B virus vaccine to enhance dendritic cell response stimulation in vitro.

In vivo methods for acute modulation of gene expression in the central nervous system

Accurate and timely expression of specific genes guarantees the healthy development and function of the brain. Indeed, variations in the correct amount or timing of gene expression lead to improper development and/or pathological conditions. Almost forty years after the first successful gene transfection in in vitro cell cultures, it is currently possible to regulate gene expression in an area-specific manner at any step of central nervous system development and in adulthood in experimental animals in vivo, even overcoming the very poor accessibility of the brain. Here, we will review the diverse approaches for acute gene transfer in vivo, highlighting their advantages and disadvantages with respect to the efficiency and specificity of transfection as well as to brain accessibility. In particular, we will present well-established chemical, physical and virus-based approaches suitable for different animal models, pointing out their current and future possible applications in basic and translational research as well as in gene therapy.

Length effects on the dynamic process of cellular uptake and exocytosis of single-walled carbon nanotubes in murine macrophage cells

Cellular uptake and exocytosis of SWCNTs are fundamental processes determining their intracellular concentration and effects. Despite the great potential of acid-oxidized SWCNTs in biomedical field, understanding of the influencing factors on these processes needs to be deepened. Here, we quantitatively investigated uptake and exocytosis of SWCNTs in three lengths-630 (±171) nm (L-SWCNTs), 390 (±50) nm (M-SWCNTs), and 195 (±63) nm (S-MWCNTs) in macrophages. The results showed that the cellular accumulation of SWCNTs was a length-independent process and non-monotonic in time, with the most SWCNTs (3950 fg/cell) accumulated at 8 h and then intracellular SWCNTs dropped obviously with time. The uptake rate of SWCNTs decreased with increasing concentration, suggesting that intracellular SWCNTs accumulation is a saturable process. After refreshing culture medium, we found increasing SWCNTs in supernatant and decreasing intracellular SWCNTs over time, confirming the exocytosis occurred. Selective inhibition of endocytosis pathways showed that the internalization of SWCNTs involves several pathways, in the order of macropinocytosis> caveolae-mediated endocytosis> clathrin-dependent endocytosis. Intriguingly, clathrin-mediated endocytosis is relatively important for internalizing shorter SWCNTs. The dynamic processes of SWCNTs uptake and exocytosis and the mechanisms revealed by this study may render a better understanding on SWCNT toxicity and facilitate the design of CNT products with mitigated toxicity and desired functions.

Carbon nanotubes: a novel material for multifaceted applications in human healthcare

Remarkable advances achieved in modern material technology, especially in device fabrication, have facilitated diverse materials to expand the list of their application fields.

Recent advances in siRNA delivery

In the 1990s an unexpected gene-silencing phenomena in plants, the later called RNA interference (RNAi), perplexed scientists. Following the proof of activity in mammalian cells, small interfering RNAs (siRNAs) have quickly crept into biomedical research as a new powerful tool for the potential treatment of different human diseases based on altered gene expression. In the past decades, several promising data from ongoing clinical trials have been reported. However, despite surprising successes in many pre-clinical studies, concrete obstacles still need to be overcome to translate therapeutic siRNAs into clinical reality. Here, we provide an update on the recent advances of RNAi-based therapeutics and highlight novel synthetic platforms for the intracellular delivery of siRNAs.

[Effects of Xenobiotics on Drug Pharmacokinetics and Safety]

The use of nanotechnology has increased over the past 10 years, and various nanomaterials with a wide range of applications have been developed. Carbon nanotubes (CNTs), which are cylindrical molecules consisting of hexagonally arranged carbon atoms, are nanomaterials with high utility. Recently, applications of single-walled CNT (SWCNT) in the medical field for drug-delivery and as gene-delivery agents have been proposed. Due to its structural characteristics and physicochemical properties, the inhalation of SWCNT could be considered as one route for targeted drug delivery into the lungs. Therefore, it is necessary to investigate the effects of SWCNT on the physiological state and response of the cells upon delivery into the lung. We clarified the different response of two carcinoma cell lines to SWCNT exposure, and determined these differences may be due to different cell functions. Furthermore, SWCNT exposure resulted in a global downregulation of stress-responsive genes in normal human bronchial epithelial cells, thereby indicating that the factors involved in the stress responses were not activated by SWCNT. We then tried to ascertain the possible effect of SWCNT on the fate of drugs delivered with SWCNT. Exposure to SWCNT down-regulated the mRNA expression and enzymatic activity of CYP1A1 and CYP1B1 by preventing the binding of activated aryl hydrocarbon receptors to the enhancer region of these genes. This review provides basic information for the prediction of human responses to SWCNT exposure by inhalation, and in its use as a drug delivery carrier.

Non-covalent polymer wrapping of carbon nanotubes and the role of wrapped polymers as functional dispersants

Carbon nanotubes (CNTs) have been recognized as a promising material in a wide range of applications from biotechnology to energy-related devices. However, the poor solubility in aqueous and organic solvents hindered the applications of CNTs. As studies have progressed, the methodology for CNT dispersion was established. In this methodology, the key issue is to covalently or non-covalently functionalize the surfaces of the CNTs with a dispersant. Among the various types of dispersions, polymer wrapping through non-covalent interactions is attractive in terms of the stability and homogeneity of the functionalization. Recently, by taking advantage of their stability, the wrapped-polymers have been utilized to support and/or reinforce the unique functionality of the CNTs, leading to the development of high-performance devices. In this review, various polymer wrapping approaches, together with the applications of the polymer-wrapped CNTs, are summarized.

Carbon-dot-based two-photon visible nanocarriers for safe and highly efficient delivery of siRNA and DNA

A simple and versatile nanoparticulate siRNA and DNA delivery vehicle is reported, based on photonic Cdots by using Alkyl-PEI2k for surface passivation.

Impact of carbon nanotubes and graphene on immune cells

It has been recently proposed that nanomaterials, alone or in concert with their specific biomolecular conjugates, can be used to directly modulate the immune system, therefore offering a new tool for the enhancement of immune-based therapies against infectious disease and cancer. Here, we revised the publications on the impact of functionalized carbon nanotubes (f-CNTs), graphene and carbon nanohorns on immune cells. Whereas f-CNTs are the nanomaterial most widely investigated, we noticed a progressive increase of studies focusing on graphene in the last couple of years. The majority of the works (56%) have been carried out on macrophages, following by lymphocytes (30% of the studies). In the case of lymphocytes, T cells were the most investigated (22%) followed by monocytes and dendritic cells (7%), mixed cell populations (peripheral blood mononuclear cells, 6%), and B and natural killer (NK) cells (1%). Most of the studies focused on toxicity and biocompatibility, while mechanistic insights on the effect of carbon nanotubes on immune cells are generally lacking. Only very recently high-throughput gene-expression analyses have shed new lights on unrecognized effects of carbon nanomaterials on the immune system. These investigations have demonstrated that some f-CNTs can directly elicitate specific inflammatory pathways. The interaction of graphene with the immune system is still at a very early stage of investigation. This comprehensive state of the art on biocompatible f-CNTs and graphene on immune cells provides a useful compass to guide future researches on immunological applications of carbon nanomaterials in medicine.

Role of pH controlled DNA secondary structures in the reversible dispersion/precipitation and separation of metallic and semiconducting single-walled carbon nanotubes

Single-stranded DNA (ss-DNA) oligomers (dA20, d[(C3TA2)3C3] or dT20) are able to disperse single-walled carbon nanotubes (SWNTs) in water at pH 7 through non-covalent wrapping on the nanotube surface. At lower pH, an alteration of the DNA secondary structure leads to precipitation of the SWNTs from the dispersion. The structural change of dA20 takes place from the single-stranded to the A-motif form at pH 3.5 while in case of d[(C3TA2)3C3] the change occurs from the single-stranded to the i-motif form at pH 5. Due to this structural change, the DNA is no longer able to bind the nanotube and hence the SWNT precipitates from its well-dispersed state. However, this could be reversed on restoring the pH to 7, where the DNA again relaxes in the single-stranded form. In this way the dispersion and precipitation process could be repeated over and over again. Variable temperature UV-Vis-NIR and CD spectroscopy studies showed that the DNA-SWNT complexes were thermally stable even at ∼90 °C at pH 7. Broadband NIR laser (1064 nm) irradiation also demonstrated the stability of the DNA-SWNT complex against local heating introduced through excitation of the carbon nanotubes. Electrophoretic mobility shift assay confirmed the formation of a stable DNA-SWNT complex at pH 7 and also the generation of DNA secondary structures (A/i-motif) upon acidification. The interactions of ss-DNA with SWNTs cause debundling of the nanotubes from its assembly. Selective affinity of the semiconducting SWNTs towards DNA than the metallic ones enables separation of the two as evident from spectroscopic as well as electrical conductivity studies.

Methylene blue covalently attached to single stranded DNA as electroactive label for potential bioassays

Methylene blue is an electroactive molecule that has been employed for the detection of the DNA hybridization event in electrochemical sensors. However, its use as a covalent label is very scarce and in most of the cases, non-covalent interactions (hydrophobic, electrostatic) are employed. Although it has advantages as simplicity and fewer number of procedure steps, the covalent attachment is less exploited in the development of these sensors. In this article, the electrochemical behavior of methylene blue attached to different DNA-strands is studied. Several lengths (15- and 30-mer) and different degree of DNA modification (MB-DNA, MB-DNA-MB and MB-DNA-SH) have been studied. The highest signals were obtained for longer strands with two MB molecules. In all the cases the signal is enhanced by CNT-nanostructuration of the electrode. Adsorption on these modified screen-printed electrodes allowed the amplification by employing an accumulation time. In this way, a sensitivity of -0.2864 μA μM-1 and a limit of detection of 800 nM for a 120 s accumulation time were obtained.

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.

Carbon nanotubes: properties, synthesis, purification, and medical applications

Current discoveries of different forms of carbon nanostructures have motivated research on their applications in various fields. They hold promise for applications in medicine, gene, and drug delivery areas. Many different production methods for carbon nanotubes (CNTs) have been introduced; functionalization, filling, doping, and chemical modification have been achieved, and characterization, separation, and manipulation of individual CNTs are now possible. Parameters such as structure, surface area, surface charge, size distribution, surface chemistry, and agglomeration state as well as purity of the samples have considerable impact on the reactivity of carbon nanotubes. Otherwise, the strength and flexibility of carbon nanotubes make them of potential use in controlling other nanoscale structures, which suggests they will have a significant role in nanotechnology engineering.

REVIEW OF METAL, CARBON AND POLYMER NANOPARTICLES FOR INFRARED PHOTOTHERMAL THERAPY

The aim of this review is to provide an up-to-date overview of nanoparticles developed for use as photothermal therapy agents (PTT) over the past five years. The main emphasis is on nanoparticles that absorb near infrared (NIR) light for PTT of cancer. Mild hyperthermia, including drug delivery, versus thermal ablation is also discussed. Recent advances in the synthesis of highly anisotropic novel metal nanoparticles for PTT are described. New metals and metal oxide complexes, as well as the use of quantum dots for PTT and as imaging agents are newer areas of development that are explained. This review also highlights current progress in the development of carbon nanoparticles, including reduced graphene oxide for both thermal ablation as well as drug delivery. The review culminates in the recent use electrically conductive polymer nanoparticles for hyperthermia. The advantages and unique features of these contemporary nanoparticles being used for PTT are highlighted. The goal of the present work is to describe the recent evolution of nanoparticles for NIR stimulated PTT, and highlight the innovations and future directions.

Mechanisms of toxicity by carbon nanotubes

Carbon nanotubes (CNTs) consist of a family of carbon built nanoparticles, whose biological effects depend on their physical characteristics and other constitutive chemicals (impurities and functions attached). CNTs are considered the twenty first century material due to their unique physicochemical characteristics and applicability to industrial product. The use of these materials steadily increases worldwide and toxic outcomes need to be studied for each nanomaterial in depth to prevent adverse effects to humans and the environment. Entrance into the body is physical, and usually few nanoparticles enter the body; however, once there, they are persistent due to their limited metabolisms, so their removal is slow, and chronic cumulative health effects are studied. Oxidative stress is the main mechanism of toxicity but size, agglomeration, chirality as well as impurities and functionalization are some of the structural and chemical characteristic contributing to the CNTs toxicity outcomes. Among the many toxicity pathways, interference with cytoskeleton and fibrous mechanisms, cell signaling, membrane perturbations and the production of cytokines, chemokines and inflammation are some of the effects resulting from exposure to CNTs. The aim of this review is to offer an up-to-date scope of the effects of CNTs on biological systems with attention to mechanisms of toxicity.

Magneto-Fluorescent Carbon Nanotube-Mediated siRNA for Gastrin-Releasing Peptide Receptor Silencing in Neuroblastoma

We demonstrate a newly-developed magneto-fluorescent carbon nanotube (CNT) mediated siRNA (CNT-siRNA) delivery system, which significantly silences our target of interest, gastrin-releasing peptide receptor (GRP-R), in neuroblastoma. CNT-siGRP-R resulted in a 50% silencing efficiency and a sustained efficacy of 9 days for one-time siRNA treatment in vitro, whereas siRNA delivered by the commercial transfection reagent couldn't knockdown GRP-R expression. We further show that CNT-siRNA efficiently inhibits the growth of subcutaneous xenograft tumors in vivo. This system allows us to track the CNT-siRNA distribution via both near-infrared fluorescence and magnetic resonance imaging. Moreover, our delivery system can be used to knockdown GRP-R expression in other cancer cell types, such as human breast cancer cells. The high efficiency and sustained efficacy may indicate that the natural stacking interactions between CNTs and siRNAs can protect siRNAs from degradation and enhance their stability during the delivery process.

A novel polyethyleneimine-coated adeno-associated virus-like particle formulation for efficient siRNA delivery in breast cancer therapy: preparation and in vitro analysis

Background

Systemic delivery of small interfering RNA (siRNA) is limited by its poor stability and limited cell-penetrating properties. To overcome these limitations, we designed an efficient siRNA delivery system using polyethyleneimine-coated virus-like particles derived from adeno-associated virus type 2 (PEI-AAV2-VLPs).

Methods

AAV2-VLPs were produced in insect cells by infection with a baculovirus vector containing three AAV2 capsid genes. Using this method, we generated well dispersed AAV2-VLPs with an average diameter of 20 nm, similar to that of the wild-type AAV2 capsid. The nanoparticles were subsequently purified by chromatography and three viral capsid proteins were confirmed by Western blot. The negatively charged AAV2-VLPs were surface-coated with PEI to develop cationic nanoparticles, and the formulation was used for efficient siRNA delivery under optimized transfection conditions.

Results

PEI-AAV2-VLPs were able to condense siRNA and to protect it from degradation by nucleases, as confirmed by gel electrophoresis. siRNA delivery mediated by PEI-AAV2-VLPs resulted in a high transfection rate in MCF-7 breast cancer cells with no significant cytotoxicity. A cell death assay also confirmed the efficacy and functionality of this novel siRNA formulation towards MCF-7 cancer cells, in which more than 60% of cell death was induced within 72 hours of transfection.

Conclusion

The present study explores the potential of virus-like particles as a new approach for gene delivery and confirms its potential for breast cancer therapy.

Carbon Nanotubes: Solution for the Therapeutic Delivery of siRNA?

Carbon nanotubes have many unique physical and chemical properties that are being widely explored for potential applications in biomedicine especially as transporters of drugs, proteins, DNA and RNA into cells. Specifically, single-walled carbon nanotubes (SWCNT) have been shown to deliver siRNA to tumors in vivo. The low toxicity, the excellent membrane penetration ability, the protection afforded against blood breakdown of the siRNA payload and the good biological activity seen in vivo suggests that SWCNT may become universal transfection vehicles for siRNA and other RNAs for therapeutic applications. This paper will introduce a short review of a number of therapeutic applications for carbon nanotubes and provide recent data suggesting SWCNT are an excellent option for the delivery of siRNA clinically.

The application of carbon nanotubes in target drug delivery systems for cancer therapies

Among all cancer treatment options, chemotherapy continues to play a major role in killing free cancer cells and removing undetectable tumor micro-focuses. Although chemotherapies are successful in some cases, systemic toxicity may develop at the same time due to lack of selectivity of the drugs for cancer tissues and cells, which often leads to the failure of chemotherapies. Obviously, the therapeutic effects will be revolutionarily improved if human can deliver the anticancer drugs with high selectivity to cancer cells or cancer tissues. This selective delivery of the drugs has been called target treatment. To realize target treatment, the first step of the strategies is to build up effective target drug delivery systems. Generally speaking, such a system is often made up of the carriers and drugs, of which the carriers play the roles of target delivery. An ideal carrier for target drug delivery systems should have three pre-requisites for their functions: (1) they themselves have target effects; (2) they have sufficiently strong adsorptive effects for anticancer drugs to ensure they can transport the drugs to the effect-relevant sites; and (3) they can release the drugs from them in the effect-relevant sites, and only in this way can the treatment effects develop. The transporting capabilities of carbon nanotubes combined with appropriate surface modifications and their unique physicochemical properties show great promise to meet the three pre-requisites. Here, we review the progress in the study on the application of carbon nanotubes as target carriers in drug delivery systems for cancer therapies.

Single wall carbon nanotubes enter cells by endocytosis and not membrane penetration

Background

Carbon nanotubes are increasingly being tested for use in cellular applications. Determining the mode of entry is essential to control and regulate specific interactions with cells, to understand toxicological effects of nanotubes, and to develop nanotube-based cellular technologies. We investigated cellular uptake of Pluronic copolymer-stabilized, purified ~145 nm long single wall carbon nanotubes (SWCNTs) through a series of complementary cellular, cell-mimetic, and in vitro model membrane experiments.

Results

SWCNTs localized within fluorescently labeled endosomes, and confocal Raman spectroscopy showed a dramatic reduction in SWCNT uptake into cells at 4°C compared with 37°C. These data suggest energy-dependent endocytosis, as shown previously. We also examined the possibility for non-specific physical penetration of SWCNTs through the plasma membrane. Electrochemical impedance spectroscopy and Langmuir monolayer film balance measurements showed that Pluronic-stabilized SWCNTs associated with membranes but did not possess sufficient insertion energy to penetrate through the membrane. SWCNTs associated with vesicles made from plasma membranes but did not rupture the vesicles.

Conclusions

These measurements, combined, demonstrate that Pluronic-stabilized SWCNTs only enter cells via energy-dependent endocytosis, and association of SWCNTs to membrane likely increases uptake.

Differential effects of single-walled carbon nanotubes on cell viability of human lung and pharynx carcinoma cell lines

Carbon nanotubes (CNTs) are attracting significant attention as a novel material for future innovations. Many in vitro studies have assessed the cytotoxicity of CNTs, but the effects of CNTs differ depending on the cell lines and the synthetic method adopted for fabricating CNTs. In the present study, the differential effects of single-walled CNTs (SWCNTs) on the cell viability of A549 cells from human lung carcinomas and FaDu cells from human head and neck carcinomas were investigated. The SWCNTs used in the present study were synthesized with nickel and yttrium (SO-SWCNTs), and iron (FH-P-SWCNTs) as catalysts. Cell viability was evaluated on the basis of cell-membrane biomass, adenosine triphosphate (ATP) content, and intracellular metabolic capacity. After 24-hr exposure of A549 and FaDu cells to 1.0 mg/ml SO-SWCNTs, the cell-membrane biomass of A549 cells decreased to 43% as compared to the control cells, whereas that of FaDu cells remained over 90%. After 24-hr exposure of A549 and FaDu cells to 1.0 mg/ml SO-SWCNT, the intracellular metabolic capacity decreased to 24% and 37%, respectively, and the ATP content decreased to 40% and 54%, respectively. SWCNTs had a greater impact on the viability values of A549 cells than on those of FaDu cells. In addition, cells exposed to FH-P-SWCNTs exhibited a higher viability than those exposed to SO-SWCNTs. Caspase 3/7 activity was not increased at maximum concentration of 1.0 mg/ml SO-SWCNTs. It was surmised that sensitivity to SWCNTs differs among the 2 cell lines; additionally, SWCNT characteristics may produce different effects on these cell lines.

Nanosecond pulse electrical fields used in conjunction with multi-wall carbon nanotubes as a potential tumor treatment

The objectives of this communication were to fabricate pure samples of multi-walled carbon nanotubes (MWCNTs) and to determine their toxicity in tumor cell lines. MWCNTs were dispersed in a concentration of the surfactant T80 that was minimally toxic. Cell-type variation in toxicity to MWCNTs was observed but was not significantly different to unexposed controls. Additionally, we investigated the increased cell killing of the pancreatic cancer cell line PANC1 when exposed to ultrashort (nanosecond) pulsed electrical fields (nsPEF) in the presence of MWCNTs as a potential form of cancer therapy. We hypothesized that the unique electronic properties of MWCNTs disrupt cell function, leading to cell death, when cells are exposed to nsPEF. We observed a 2.3-fold reduction in cell survival in cells pulsed in the presence of MWCNTs compared to pulsed controls. This study demonstrates that ultrashort pulse electrical field applications have enhanced killing effects when cells are previously grown in the presence of MWCNTs, suggesting that the electrical properties of MWCNTs play a vital role in this process and is suggestive of a synergistic interaction between these nanomaterials and electrical fields.

Barriers to non-viral vector-mediated gene delivery in the nervous system

Efficient methods for cell line transfection are well described, but, for primary neurons, a high-yield method different from those relying on viral vectors is lacking. Viral transfection has several drawbacks, such as the complexity of vector preparation, safety concerns, and the generation of immune and inflammatory responses when used in vivo. However, one of the main problems for the use of non-viral gene vectors for neuronal transfection is their low efficiency when compared with viral vectors. Transgene expression, or siRNA delivery mediated by non-viral vectors, is the result of multiple processes related to cellular membrane crossing, intracellular traffic, and/or nuclear delivery of the genetic material cargo. This review will deal with the barriers that different nanoparticles (cationic lipids, polyethyleneimine, dendrimers and carbon nanotubes) must overcome to efficiently deliver their cargo to central nervous system cells, including internalization into the neurons, interaction with intracellular organelles such as lysosomes, and transport across the nuclear membrane of the neuron in the case of DNA transfection. Furthermore, when used in vivo, the nanoparticles should efficiently cross the blood-brain barrier to reach the target cells in the brain.

Distribution and clearance of PEG-single-walled carbon nanotube cancer drug delivery vehicles in mice

AIMS

To study the distribution and clearance of polyethylene glycol (PEG)-ylated single-walled carbon nanotube (SWCNTs) as drug delivery vehicles for the anticancer drug cisplatin in mice.

MATERIALS & METHODS

PEG layers were attached to SWCNTs and dispersed in aqueous media and characterized using dynamic light scattering, scanning transmission electron microscopy and Raman spectroscopy. Cytotoxicity was assessed in vitro using Annexin-V assay, and the distribution and clearance pathways in mice were studied by histological staining and Raman spectroscopy. Efficacy of PEG-SWCNT-cisplatin for tumor growth inhibition was studied in mice.

RESULTS & DISCUSSION

PEG-SWCNTs were efficiently dispersed in aqueous media compared with controls, and did not induce apoptosis in vitro. Hematoxylin and eosin staining, and Raman bands for SWCNTs in tissues from several vital organs from mice injected intravenously with nanotube bioconjugates revealed that control SWCNTs were lodged in lung tissue as large aggregates compared with the PEG-SWCNTs, which showed little or no accumulation. Characteristic SWCNT Raman bands in feces revealed the presence of bilary or renal excretion routes. Attachment of cisplatin on bioconjugates was visualized with Z-contrast scanning transmission electron microscopy. PEG-SWCNT-cisplatin with the attached targeting ligand EGF successfully inhibited growth of head and neck tumor xenografts in mice.

CONCLUSIONS

PEG-SWCNTs, as opposed to control SWCNTs, form more highly dispersed delivery vehicles that, when loaded with both cisplatin and EGF, inhibit growth of squamous cell tumors.

Interfacing carbon nanotubes with living mammalian cells and cytotoxicity issues

The unique structures and properties of carbon nanotubes (CNTs) have attracted extensive investigations for many applications, such as those in the field of biomedical materials and devices, biosensors, drug delivery, and tissue engineering. Anticipated large-scale productions for numerous diversified applications of CNTs might adversely affect the environment and human health. For successful applications in the biomedical field, the issue of interfacing between CNTs and mammalian cells in vitro needs to be addressed before in vivo studies can be carried out systematically. We review the important studies pertaining to the internalization of CNTs into the cells and the culturing of cells on the CNT-based scaffold or support materials. The review will focus on the description of a variety of factors affecting CNT cytotoxicity: type of CNTs, impurities, lengths of CNTs, aspect ratios, dispersion, chemical modification, and assaying methods of cytotoxicity.

Advancement in carbon nanotubes: basics, biomedical applications and toxicity

Objectives

Carbon nanotubes (CNTs) have attracted much attention by researchers worldwide in recent years for their small dimensions and unique architecture, and for having immense potential in nanomedicine as biocompatible and supportive substrates, as a novel tool for the delivery of therapeutic molecules including peptides, RNA and DNA, and also as sensors, actuators and composites.

Key findings

CNTs have been employed in the development of molecular electronic, composite materials and others due to their unique atomic structure, high surface area-to-volume ratio and excellent electronic, mechanical and thermal properties. Recently they have been exploited as novel nanocarriers in drug delivery systems and biomedical applications. Their larger inner volume as compared with the dimensions of the tube and easy immobilization of their outer surface with biocompatible materials make CNTs a superior nanomaterial for drug delivery. Literature reveals that CNTs are versatile carriers for controlled and targeted drug delivery, especially for cancer cells, because of their cell membrane penetrability.

Summary

This review enlightens the biomedical application of CNTs with special emphasis on utilization in controlled and targeted drug delivery, as a diagnostics tool and other possible uses in therapeutic systems. The review also focuses on the toxicity aspects of CNTs, and revealed that genotoxic potential, mutagenic and carcinogenic effects of different types of CNTs must be explored and overcome by formulating safe biomaterial for drug delivery. The review also describes the regulatory aspects and clinical and market status of CNTs.

Nonviral vectors for the delivery of small interfering RNAs to the CNS

While efficient methods for cell line transfection are well described, for primary neurons a high-yield method different from those relying on viral vectors is lacking. Viral vector-based primary neuronal infection has several drawbacks, including complexity of vector preparation, safety concerns and the generation of immune and inflammatory responses, when used in vivo. This article will cover the different approaches that are being used to efficiently deliver genetic material (both DNA and small interfering RNA) to neuronal tissue using nonviral vectors, including the use of cationic lipids, polyethylenimine derivatives, dendrimers, carbon nanotubes and the combination of carbon-made nanoparticles with dendrimers. The effectiveness, both in vivo and in vitro, of the different methods to deliver genetic material to neural tissue is discussed.

Carbon nanotubes in cancer theragnosis

Carbon nanotubes as a unique and novel class of nanomaterials have shown considerable promise in cancer therapy and diagnosis amidst the myriad of nanocarriers. The presence of a large surface area enables the engineering of the surface of nanotubes, thus making them biocompatible, and large benefits can be harnessed from them. Together with their ability to encapsulate small molecules, stacking interactions and conjugation, nanotubes have improved the profile of anticancer agents. The propensity to absorb the body transparent NIR radiation also envisages photothermal and photoacoustic therapy using nanotubes. This article sheds light on the role of carbon nanotubes in cancer therapy and diagnosis based on recent findings.

Carbon nanotubes in the biological interphase: the relevance of noncovalence

With the increasing interest in the biological applications of carbon nanotubes, their interactions in the biological interphase and their general cytotoxicity have become major issues. In spite of their salient properties, major hurdles still exist for their use in biological applications, due to their main characteristics, including their hydrophobic surfaces and tendency to aggregate, as well as their unknown interactions in the cellular interphase. In this Research News, these characteristics of carbon nanotubes, a model nanomaterial, are investigated. Thus, the cytotoxicity of carbon nanotubes, the influence of functionalization, as well as their interactions with different mammalian cell lines are studied. Moreover, suggestions for the improvement of their biocompatibility and the design of biocompatible carbon nanotube-based systems are provided.

Delivery of RNAi mediators

Delivering polynucleotides into animals has been a major challenge facing their success as therapeutic agents. Given the matured understanding of antibody‐mediated delivery techniques, it is possible to rationally design delivery vehicles that circulate in the blood stream and are specifically delivered into target organs. If the targeting moiety is designed to contain the cargo of an RNAi mediator without impacting its paratope, directed delivery can be achieved. In this article, we review the state of art in delivery technology for RNA mediators and address how this technique could soon be used to enhance the efficacy of the numerous small RNA therapeutic programs currently under evaluation. Copyright © 2010 John Wiley & Sons, Ltd.

This article is categorized under: 1

Regulatory RNAs/RNAi/Riboswitches > RNAi: Mechanisms of Action

2

RNA Methods > RNA Analyses in Cells

3

RNA in Disease and Development > RNA in Disease

DNA and carbon nanotubes as medicine

The identification of disease-related genes and their complete nucleotide sequence through the human genome project provides us with a remarkable opportunity to combat a large number of diseases with designed genes as medicine. However, gene therapy relies on the efficient and nontoxic transport of therapeutic genetic medicine through the cell membranes, and this process is very inefficient. Carbon nanotubes, due to their large surface areas, unique surface properties, and needle-like shape, can deliver a large amount of therapeutic agents, including DNA and siRNAs, to the target disease sites. In addition, due to their unparalleled optical and electrical properties, carbon nanotubes can deliver DNA/siRNA not only into cells, which include difficult transfecting primary-immune cells and bacteria, they can also lead to controlled release of DNA/siRNA for targeted gene therapy. Furthermore, due to their wire shaped structure with a diameter matching with that of DNA/siRNA and their remarkable flexibility, carbon nanotubes can impact on the conformational structure and the transient conformational change of DNA/RNA, which can further enhance the therapeutic effects of DNA/siRNA. Synergistic combination of the multiple capabilities of carbon nanotubes to deliver DNA/siRNAs will lead to the development of powerful multifunctional nanomedicine to treat cancer or other difficult diseases. In this review, we summarized the current studies in using CNT as unique vehicles in the field of gene therapy.

Inhibitory RNA molecules in immunotherapy for cancer

Over the past few decades, our expanding knowledge of the mammalian immune system - how it is developed, activated, and regulated - has fostered hope that it may be harnessed in the future to successfully treat human cancer. The immune system activated by cancer vaccines may have the unique ability to selectively eradicate tumor cells at multiple sites in the body without inflicting damage on normal tissue. However, progress in the development of cancer vaccines that effectively capitalize on this ability has been limited and slow. The immune system is restrained by complex, negative feedback mechanisms that evolved to protect the host against autoimmunity and may also prevent antitumor immunity. In addition, tumor cells exploit a plethora of strategies to evade detection and elimination by the immune system. For these reasons, the field of cancer immunotherapy has suffered considerable setbacks in the past and faces great challenges at the present time. Some of these challenges may be overcome through the use of RNA interference, a process by which gene expression can be efficiently and specifically "knocked down" in cells. This chapter focuses on the current status and future prospects in the application of small interfering RNA and microRNA, two main forms of RNA interference, to treat cancer by curtailing mechanisms that attenuate the host immune response.

Convenient targeting of stealth siRNA-lipoplexes to cells with chelator lipid-anchored molecules

A major obstacle for the use of siRNAs as novel therapeutics is the requirement for functional delivery to specific cells in vivo. siRNA delivery by cationic agents is generally non-specific and a convenient targeting strategy has been lacking. This work explored the potential for using the chelator lipid 3(nitrilotriacetic acid)-ditetradecylamine (NTA(3)-DTDA) with neutral stealth liposomes to target siRNA to cells. A novel method for incorporating siRNAs into lipoplexes was developed which utilised helper lipids and the ionisable lipid 1,2-dioleoyl-3-dimethylammonium-propane (DODAP). This approach results in an efficient (>50%) incorporation of siRNA into lipoplexes, which when incorporated with Ni-NTA(3)-DTDA and engrafted with a His-tagged form of murine CD4 can target siRNA to murine A20 B cells, in vitro. Also, siRNA-lipoplexes engrafted with His-tagged peptides that target receptors on HEK-293 cells, or the receptor for tumour necrosis factor alpha expressed on the murine dendritic cell line DC2.4, could target siRNA and silence the expression of enhanced green fluorescence protein (EGFP). siRNA-lipoplexes produced by this method are approximately 240 nm dia, exhibit low zeta-potential (-1 mV), and target cells in serum-containing media. The results show that NTA(3)-DTDA can be used to target siRNA-lipoplexes to cells, and could provide a convenient approach for targeting siRNA to cells in vivo for therapeutic applications.

Targeted killing of cancer cells in vivo and in vitro with EGF-directed carbon nanotube-based drug delivery

Carbon nanotube-based drug delivery holds great promise for cancer therapy. Herein we report the first targeted, in vivo killing of cancer cells using a drug-single wall carbon nanotube (SWNT) bioconjugate, and demonstrate efficacy superior to nontargeted bioconjugates. First line anticancer agent cisplatin and epidermal growth factor (EGF) were attached to SWNTs to specifically target squamous cancer, and the nontargeted control was SWNT-cisplatin without EGF. Initial in vitro imaging studies with head and neck squamous carcinoma cells (HNSCC) overexpressing EGF receptors (EGFR) using Qdot luminescence and confocal microscopy showed that SWNT-Qdot-EGF bioconjugates internalized rapidly into the cancer cells. Limited uptake occurred for control cells without EGF, and uptake was blocked by siRNA knockdown of EGFR in cancer cells, revealing the importance of EGF-EGFR binding. Three color, two-photon intravital video imaging in vivo showed that SWNT-Qdot-EGF injected into live mice was selectively taken up by HNSCC tumors, but SWNT-Qdot controls with no EGF were cleared from the tumor region in <20 min. HNSCC cells treated with SWNT-cisplatin-EGF were also killed selectively, while control systems that did not feature EGF-EGFR binding did not influence cell proliferation. Most significantly, regression of tumor growth was rapid in mice treated with targeted SWNT-cisplatin-EGF relative to nontargeted SWNT-cisplatin.

RNA interference-mediated in vivo silencing of fas ligand as a strategy for the enhancement of DNA vaccine potency

Intradermal administration of DNA vaccines encoding luciferase represents a convenient method to assess gene expression in vivo. Gene silencing by intradermal gene gun administration of DNA encoding short hairpin RNA (shRNA) may represent an effective technique for the specific knockdown of gene expression in vivo. In the current study, we characterized luciferase gene expression over time in vivo by noninvasive bioluminescence imaging. Furthermore, we characterized in vivo luciferase gene silencing with DNA encoding shRNA targeting luciferase. We also characterized human papillomavirus type 16 (HPV-16) E7-specific CD8(+) T cell immune responses in mice immunized with E7 DNA and DNA encoding shRNA targeting Fas ligand (FasL), a key proapoptotic signaling protein. Our results indicated that coadministration of DNA encoding shRNA targeting luciferase significantly reduced luciferase expression in mice intradermally administered luciferase DNA. Furthermore, we observed that mice vaccinated with E7-expressing DNA coadministered with DNA encoding shRNA targeting FasL generated significantly enhanced E7-specific CD8(+) cytotoxic T cell responses as well as potent therapeutic antitumor effects against E7-expressing tumors. Thus, intradermal administration of DNA encoding shRNA represents a plausible approach to silence genes in vivo and a potentially useful tool to enhance DNA vaccine potency.