Highly efficient molecular delivery into mammalian cells using carbon nanotube spearing

Synthesis of superparamagnetic nanotubes as MRI contrast agents and for cell labeling

AIMS

Magnetic nanoparticles have been studied widely as MRI contrast agents to increase the sensitivity of this technique. This work describes the synthesis and characterization of magnetic nanotubes (MNTs) as a novel MRI contrast agent.

METHODS

MNTs with high saturation magnetization were fabricated by the synthesis of superparamagnetic iron oxide nanoparticles (SPIONs) directly in the pores of silica nanotubes (SNTs). The MNTs were characterized by electron microscopy, superconducting quantum interference device and MRI. Preliminary studies on in vitro cytotoxicity and cell labeling were carried out.

RESULTS

The MNTs retained the superparamagnetic characteristics in bulk solutions with a considerably high saturation magnetization of 95 emu/gFe. The nuclear magnetic resonance (NMR) relaxivities for MNTs of 500 nm in length and of 60 nm in diameter were r(1) = 1.6 +/- 0.3 mM(-1)s(-1) and r(2) = 264 +/- 56 mM(-1)s(-1) and, for the MNTs of 2 microm in length and 70 nm in diameter, the r(1) and r(2) were 3.0 +/- 1.3 and 358 +/- 65 mM(-1)s(-1), respectively. In vitro cell labeling showed promising results with excellent labeling efficiency. No cellular toxicity was observed in vitro.

CONCLUSIONS

The integration of SPIONs with SNTs imparts the superparamagnetic characteristics of SPIONs onto the SNTs, creating unique magnetic nanoparticles with multifunctionality. The MNTs showed promising results as a MRI contrast agent with high NMR relaxivities, little cytotoxicity and high cell-labeling efficiency.

Nanoparticles as nonviral gene delivery vectors

Gene therapy, as therapeutic treatment to genetic or acquired diseases, is attracting much interest in the research community, leading to noteworthy developments over the past two decades. Although this field is still dominated by viral vectors, nonviral vectors have recently received an ever increasing attention in order to overcome the safety problems of their viral counterpart. This review presents the biological aspects involved in the gene delivery process and explores the recent developments and achievements of nonviral gene carriers.

A generally adoptable radiotracing method for tracking carbon nanotubes in animals

Carbon nanotube (CNT) mediated drug delivery systems have currently aroused a great deal of interest. Such delivery systems for drugs, proteins and genes have been preliminarily studied using cellular and animal models. For the further study of the pharmacokinetics and related biological behaviours of CNTs in vivo, a fast and convenient tracing method is particularly demanded. In this paper, we developed a generally adoptable tracing method for the biodistribution study of functionalized CNTs in vivo. Taurine covalently functionalized multi-walled carbon nanotubes (tau-MWNTs) and Tween-80 wrapped MWNTs (Tween-MWNTs) were labelled with (125)I, and then their distribution in mice was determined. It is interesting that Tween-80 can reduce the RES uptake of MWNTs remarkably. The resulting distribution of (125)I-tau-MWNTs was very consistent with that using (14)C-taurine-MWNTs as the CNTs tracer, which means the easy (125)I labelling method is reliable and effective.

Bench-to-bedside review: Mitochondrial injury, oxidative stress and apoptosis--there is nothing more practical than a good theory

Apoptosis contributes to cell death in common intensive care unit disorders such as traumatic brain injury and sepsis. Recent evidence suggests that this form of cell death is both clinically relevant and a potential therapeutic target in critical illness. Mitochondrial reactive oxygen species (ROS) have become a target for drug discovery in recent years since their production is characteristic of early stages of apoptosis. Among many antioxidant agents, stable nitroxide radicals targeted to mitochondria have attracted attention due to their ability to combine electron and free radical scavenging action with recycling capacities. Specific mechanisms of enhanced ROS generation in mitochondria and their translation into apoptotic signals are not well understood. This review focuses on several contemporary aspects of oxidative stress-mediated mitochondrial injury, particularly as they relate to oxidation of lipids and their specific signaling roles in apoptosis and phagocytosis of apoptotic cells.

Magnetic nanoparticles for gene and drug delivery

Investigations of magnetic micro- and nanoparticles for targeted drug delivery began over 30 years ago. Since that time, major progress has been made in particle design and synthesis techniques, however, very few clinical trials have taken place. Here we review advances in magnetic nanoparticle design, in vitro and animal experiments with magnetic nanoparticle-based drug and gene delivery, and clinical trials of drug targeting.

Computer modeling in biotechnology: a partner in development

Computational modeling can be a useful partner in biotechnology, in particular, in nanodevice engineering. Such modeling guides development through nanoscale views of biomolecules and devices not available through experimental imaging methods. We illustrate the role of computational modeling, mainly of molecular dynamics, through four case studies: development of silicon bionanodevices for single molecule electrical recording, development of carbon nano-tube-biomolecular systems as in vivo sensors, development of lipoprotein nanodiscs for assays of single membrane proteins, and engineering of oxygen tolerance into the enzyme hydrogenase for photosynthetic hydrogen gas production. The four case studies show how molecular dynamics approaches were adapted to the specific technical uses through (i) multi-scale extensions, (ii) fast quantum chemical force field evaluation, (iii) coarse graining, and (iv) novel sampling methods. The adapted molecular dynamics simulations provided key information on device behavior and revealed development opportunities, arguing that the "computational microscope" is an indispensable nanoengineering tool.

Inducible RNA interference-mediated gene silencing using nanostructured gene delivery arrays

RNA interference (RNAi) has become a powerful biological tool over the past decade. In this study, a tetracycline-inducible small hairpin RNA (shRNA) vector system was designed for silencing cyan fluorescent protein (CFP) expression and delivered alongside the yfp marker gene into Chinese hamster ovary cells using impalefection on spatially indexed vertically aligned carbon nanofiber arrays (VACNFs). The VACNF architecture provided simultaneous delivery of multiple genes, subsequent adherence and proliferation of interfaced cells, and repeated monitoring of single cells over time. Following impalefection and tetracycline induction, 53.1% +/- 10.4% of impalefected cells were fully silenced by the inducible CFP-silencing shRNA vector. Additionally, efficient CFP silencing was observed in single cells among a population of cells that remained CFP-expressing. This effective transient expression system enables rapid analysis of gene-silencing effects using RNAi in single cells and cell populations.

Overview of drug delivery and alternative methods to electroporation

This chapter provides an overview of the application of electroporation to areas other than gene delivery. These areas include the delivery of drugs and vaccines to tissues and tumors as well as into and through the skin. Achievements and limitations of electroporation in these areas are presented. Alternative physical methods for gene and drug delivery besides electroporation are described. The advantages and drawbacks of electroporation, compared with these methods, are also discussed.

Dendrimer-modified magnetic nanoparticles enhance efficiency of gene delivery system

Magnetic nanoparticles (MNP) with a diameter of 8 nm were modified with different generations of polyamidoamine (PAMAM) dendrimers and mixed with antisense survivin oligodeoxynucleotide (asODN). The MNP then formed asODN-dendrimer-MNP composites, which we incubated with human tumor cell lines such as human breast cancer MCF-7, MDA-MB-435, and liver cancer HepG2 and then analyzed by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide, quantitative reverse transcription-PCR, Western blotting, laser confocal microscopy, and high-resolution transmission electron microscopy. Results showed that the asODN-dendrimer-MNP composites were successfully synthesized, can enter into tumor cells within 15 min, caused marked down-regulation of the survivin gene and protein, and inhibited cell growth in dose- and time-dependent means. No.5 generation of asODN-dendrimer-MNP composites exhibits the highest efficiency for cellular transfection and inhibition. These results show that PAMAM dendrimer-modified MNPs may be a good gene delivery system and have potential applications in cancer therapy and molecular imaging diagnosis.

Single-walled carbon nanotube interactions with HeLa cells

This work concerns exposing cultured human epithelial-like HeLa cells to single-walled carbon nanotubes (SWNTs) dispersed in cell culture media supplemented with serum. First, the as-received CoMoCAT SWNT-containing powder was characterized using scanning electron microscopy and thermal gravimetric analyses. Characterizations of the purified dispersions, termed DM-SWNTs, involved atomic force microscopy, inductively coupled plasma - mass spectrometry, and absorption and Raman spectroscopies. Confocal microRaman spectroscopy was used to demonstrate that DM-SWNTs were taken up by HeLa cells in a time- and temperature-dependent fashion. Transmission electron microscopy revealed SWNT-like material in intracellular vacuoles. The morphologies and growth rates of HeLa cells exposed to DM-SWNTs were statistically similar to control cells over the course of 4 d. Finally, flow cytometry was used to show that the fluorescence from MitoSOXtrade mark Red, a selective indicator of superoxide in mitochondria, was statistically similar in both control cells and cells incubated in DM-SWNTs. The combined results indicate that under our sample preparation protocols and assay conditions, CoMoCAT DM-SWNT dispersions are not inherently cytotoxic to HeLa cells. We conclude with recommendations for improving the accuracy and comparability of carbon nanotube (CNT) cytotoxicity reports.

Use of degradable and nondegradable nanomaterials for controlled release

Drug-delivery devices are fundamentally important in improving the pharmacological profiles of therapeutic molecules. Nanocontrolled-release systems are attracting a lot of attention currently owing to their large surface area and their ability to target delivery to specific sites in the human body. In addition, they can penetrate the cell membrane for gene, nucleic acid and bioactive peptide/protein delivery. Representative applications of nanodrug-delivery systems include controlled-release wound dressings, controlled-release scaffolds for tissue regeneration and implantable biodegradable nanomaterial-based medical devices integrated with drug-delivery functions. We review the present status and future perspectives of various types of nanocontrolled-release systems. Although many of the well-established degradable and nondegradable controlled-release vehicles are being investigated for their processing into nanocarriers, several new emerging nanomaterials are being studied for their controlled-release properties. The release of multiple bioactive agents, each with its own kinetic profile, is becoming possible. In addition, integration of the nanocontrolled-release systems with other desirable functions to create new, cross-discipline applications can also be realized.

Multifunctional nanorods for biomedical applications

Multifunctional nanorods have shown significant potential in a wide range of biomedical applications. Nanorods can be synthesized by a top down or bottom-up approach. The bottom-up approach commonly utilizes a template deposition methodology. A variety of metal segments can easily be incorporated into the nanorods. This permits high degrees of chemical and dimensional control. High aspect-ratio nanorods have a large surface area for functionalization. By varying the metal segments in the nanorods, spatial control over the binding of functional biomolecules that correspond with the unique surface chemistry of the metal segment can be achieved. Functionalized multicomponent nanorods are utilized in applications ranging from multiplexing, protein sensing, glucose sensing, imaging, biomolecule-associated nanocircuits, gene delivery and vaccinations.

Nanomedicine in the diagnosis and therapy of neurodegenerative disorders

Neurodegenerative and infectious disorders including Alzheimer's and Parkinson's diseases, amyotrophic lateral sclerosis, and stroke are rapidly increasing as population's age. Alzheimer's disease alone currently affects 4.5 million Americans, and more than $100 billion is spent per year on medical and institutional care for affected people. Such numbers will double in the ensuing decades. Currently disease diagnosis for all disorders is made, in large measure, on clinical grounds as laboratory and neuroimaging tests confirm what is seen by more routine examination. Achieving early diagnosis would enable improved disease outcomes. Drugs, vaccines or regenerative proteins present "real" possibilities for positively affecting disease outcomes, but are limited in that their entry into the brain is commonly restricted across the blood-brain barrier. This review highlights how these obstacles can be overcome by polymer science and nanotechnology. Such approaches may improve diagnostic and therapeutic outcomes. New developments in polymer science coupled with cell-based delivery strategies support the notion that diseases that now have limited therapeutic options can show improved outcomes by advances in nanomedicine.

Luminescent silica nanobeads: characterization and evaluation as efficient cytoplasmatic transporters for T-lymphocytes

We report the fabrication and characterization of neutravidin-conjugated silica nanobeads doped with a ruthenium-complex luminophore and functionalized with antihuman CD3, antihuman CD28, and an acid-sensitive polymer. We observed that the nanobeads were readily delivered into Jurkat T leukemia cells by endocytosis, transported into lysosomes and subsequently into the cytoplasm as revealed by pH-sensitive luminescence. Since signs of cytotoxicity were not observed, the reported nanobeads could be an excellent and nontoxic building block for efficient intracellular transporters.

A cell nanoinjector based on carbon nanotubes

Technologies for introducing molecules into living cells are vital for probing the physical properties and biochemical interactions that govern the cell's behavior. Here, we report the development of a nanoscale cell injection system (termed the nanoinjector) that uses carbon nanotubes to deliver cargo into cells. A single multiwalled carbon nanotube attached to an atomic force microscope (AFM) tip was functionalized with cargo via a disulfide-based linker. Penetration of cell membranes with this "nanoneedle" was controlled by the AFM. The following reductive cleavage of the disulfide bonds within the cell's interior resulted in the release of cargo inside the cells, after which the nanoneedle was retracted by AFM control. The capability of the nanoinjector was demonstrated by injection of protein-coated quantum dots into live human cells. Single-particle tracking was used to characterize the diffusion dynamics of injected quantum dots in the cytosol. This technique causes no discernible membrane or cell damage, and can deliver a discrete number of molecules to the cell's interior without the requirement of a carrier solvent.

Shape effects of filaments versus spherical particles in flow and drug delivery

Interaction of spherical particles with cells and within animals has been studied extensively, but the effects of shape have received little attention. Here we use highly stable, polymer micelle assemblies known as filomicelles to compare the transport and trafficking of flexible filaments with spheres of similar chemistry. In rodents, filomicelles persisted in the circulation up to one week after intravenous injection. This is about ten times longer than their spherical counterparts and is more persistent than any known synthetic nanoparticle. Under fluid flow conditions, spheres and short filomicelles are taken up by cells more readily than longer filaments because the latter are extended by the flow. Preliminary results further demonstrate that filomicelles can effectively deliver the anticancer drug paclitaxel and shrink human-derived tumours in mice. Although these findings show that long-circulating vehicles need not be nanospheres, they also lend insight into possible shape effects of natural filamentous viruses.

Single cell transfection using plasmid decorated AFM probes

Eukaryotic cells were individually transfected using commercially available atomic force microscope tips decorated with plasmidic DNA encoding for the fluorescent protein EGFP. In a typical transfection attempt, the tip is forcibly incorporated into the cell thus allowing for the transfer of the genetic material through the cell membrane. A sharp discontinuity, corresponding to the passage of the tip through the cell membrane can be easily detected when monitoring the cellular deformation as a function of the applied force. In order for the transfection to be successful, the tip must reversibly penetrates the membrane without causing disturbance or damage to the cell. Transfection success rate (30%), cell survival, and growth are confirmed by epifluorescence microscopy. This technique provides an alternative tool to the transfection toolbox, allowing the transfection of specific individual cells with minimal disturbance.

Internalization of MWCNTs by microglia: Possible application in immunotherapy of brain tumors

There is a pressing need for new therapeutic, diagnostic, and drug delivery approaches for treating brain cancers. Nanotechnology offers a new method for targeted brain cancer therapy and could play a major role in gene and drug delivery. The goals of our study were to visualize in vitro ingestion, cytotoxicity, and loading capacity of Multi-Walled Carbon Nanotubes (MWCNTs) in microglia. Furthermore, we investigated internalization differences between microglia and glioma cells. BV2 microglia and GL261 glioma cells were incubated with MWCNTs, which were synthesized through catalytic chemical vapor deposition technique. Real-time RT-PCR, cell proliferation analysis, siRNA and DNA loading, electron microscopy, and flow cytometry were performed. We demonstrated that MWCNTs do not result in proliferative or cytokine changes in vitro, are capable of carrying DNA and siRNA and are internalized at higher levels in phagocytic cells as compared to tumor cells. This study suggests MWCNTs could be used as a novel, non-toxic, and biodegradable nano-vehicles for targeted therapy in brain cancers. Further studies are needed to demonstrate the full capacity of MWCNTs as nanovectors.

Nanostructured materials for applications in drug delivery and tissue engineering

Research in the areas of drug delivery and tissue engineering has witnessed tremendous progress in recent years due to their unlimited potential to improve human health. Meanwhile, the development of nanotechnology provides opportunities to characterize, manipulate and organize matter systematically at the nanometer scale. Biomaterials with nano-scale organizations have been used as controlled release reservoirs for drug delivery and artificial matrices for tissue engineering. Drug-delivery systems can be synthesized with controlled composition, shape, size and morphology. Their surface properties can be manipulated to increase solubility, immunocompatibility and cellular uptake. The limitations of current drug delivery systems include suboptimal bioavailability, limited effective targeting and potential cytotoxicity. Promising and versatile nano-scale drug-delivery systems include nanoparticles, nanocapsules, nanotubes, nanogels and dendrimers. They can be used to deliver both small-molecule drugs and various classes of biomacromolecules, such as peptides, proteins, plasmid DNA and synthetic oligodeoxynucleotides. Whereas traditional tissue-engineering scaffolds were based on hydrolytically degradable macroporous materials, current approaches emphasize the control over cell behaviors and tissue formation by nano-scale topography that closely mimics the natural extracellular matrix (ECM). The understanding that the natural ECM is a multifunctional nanocomposite motivated researchers to develop nanofibrous scaffolds through electrospinning or self-assembly. Nanocomposites containing nanocrystals have been shown to elicit active bone growth. Drug delivery and tissue engineering are closely related fields. In fact, tissue engineering can be viewed as a special case of drug delivery where the goal is to accomplish controlled delivery of mammalian cells. Controlled release of therapeutic factors in turn will enhance the efficacy of tissue engineering. From a materials point of view, both the drug-delivery vehicles and tissue-engineering scaffolds need to be biocompatible and biodegradable. The biological functions of encapsulated drugs and cells can be dramatically enhanced by designing biomaterials with controlled organizations at the nanometer scale. This review summarizes the most recent development in utilizing nanostructured materials for applications in drug delivery and tissue engineering.

Polymer genomics: an insight into pharmacology and toxicology of nanomedicines

Synthetic polymers and nanomaterials display selective phenotypic effects in cells and in the body signal transduction mechanisms involved in inflammation, differentiation, proliferation, and apoptosis. When physically mixed or covalently conjugated with cytotoxic agents, bacterial DNA or antigens, polymers can drastically alter specific genetically controlled responses to these agents. These effects, in part, result from cooperative interactions of polymers and nanomaterials with plasma cell membranes and trafficking of polymers and nanomaterials to intracellular organelles. Cells and whole organism responses to these materials can be phenotype or genotype dependent. In selected cases, polymer agents can bypass limitations to biological responses imposed by the genotype, for example, phenotypic correction of immune response by polyelectrolytes. Overall, these effects are relatively benign as they do not result in cytotoxicity or major toxicities in the body. Collectively, however, these studies support the need for assessing pharmacogenomic effects of polymer materials to maximize clinical outcomes and understand the pharmacological and toxicological effects of polymer formulations of biological agents, i.e. polymer genomics.

Magnetic micro- and nano-particle-based targeting for drug and gene delivery

The use of magnetic micro- and nano-particles as carriers for in vivo targeting of therapeutic compounds was first proposed over 25 years ago. Since then, a variety of animal studies have demonstrated the efficacy of the technique, however, only a handful of Phase I/II clinical trials have taken place. While the theoretical underpinnings have been lacking, recent advances in mathematical modeling of magnetic targeting, as well as the development of novel magnetic nanoparticle carriers and implantable magnets, show promise in progressing this technology from the laboratory to the clinic.

Gene therapy progress and prospects: magnetic nanoparticle-based gene delivery

The recent emphasis on the development of non-viral transfection agents for gene delivery has led to new physics and chemistry-based techniques, which take advantage of charge interactions and energetic processes. One of these techniques which shows much promise for both in vitro and in vivo transfection involves the use of biocompatible magnetic nanoparticles for gene delivery. In these systems, therapeutic or reporter genes are attached to magnetic nanoparticles, which are then focused to the target site/cells via high-field/high-gradient magnets. The technique promotes rapid transfection and, as more recent work indicates, excellent overall transfection levels as well. The advantages and difficulties associated with magnetic nanoparticle-based transfection will be discussed as will the underlying physical principles, recent studies and potential future applications.

Functionalized carbon nanotubes as emerging nanovectors for the delivery of therapeutics

Functionalized carbon nanotubes (f-CNT) are emerging as a new family of nanovectors for the delivery of different types of therapeutic molecules. The application of CNT in the field of carrier-mediated delivery has become possible after the recent discovery of their capacity to penetrate into the cells. CNT can be loaded with active molecules by forming stable covalent bonds or supramolecular assemblies based on noncovalent interactions. Once the cargos are carried into various cells, tissues and organs they are able to express their biological function. In this review, we will describe the potential of f-CNT to deliver different types of therapeutic molecules.

Applications of carbon nanotubes in drug delivery

The development of new and efficient drug delivery systems is of fundamental importance to improve the pharmacological profiles of many classes of therapeutic molecules. Many different types of drug delivery systems are currently available. Within the family of nanomaterials, carbon nanotubes (CNT) have emerged as a new alternative and efficient tool for transporting and translocating therapeutic molecules. CNT can be functionalised with bioactive peptides, proteins, nucleic acids and drugs, and used to deliver their cargos to cells and organs. Because functionalised CNT display low toxicity and are not immunogenic, such systems hold great potential in the field of nanobiotechnology and nanomedicine.

Programmed assembly of multi-layered protein/nanoparticle-carbon nanotube conjugates

Biomolecular interactions are used to programme the assembly of multi-layer, multi-functional CNT-based conjugates.