Cationic Carbon Nanotubes Research Articles

Gene transfer to German chamomile (L chamomilla M) using cationic carbon nanotubes

The use of nanoparticles to transfer genes to plant cells can solve some problems encountered in other gene transfer methods, including limited host range in the use of Agrobacterium, cell wall removal in the use of polyethylene glycol and electroporation, and high cell damage while using a gene gun. In this research, cationic carbon nanotubes (CNTs) were used to transfer ssDNA-FITC to German chamomile cells. The ability of nanoparticles to interact with and protect of DNA against enzymes and ultrasound damages was investigated using 0.8 % agarose gel. To investigate the morphology of CNTs loaded with DNA (Nanotube- Polyethyleneimine/DNA nanoparticles), scanning electron microscopy (SEM) was used. The biocompatibility effect of CNTs (Nanotube- Polyethyleneimine) on German chamomile cells was also determined by trypan blue staining. Agarose gel images showed that CNTs have a high ability to interact with DNA and can effectively protect it from damage by ultrasound and digestive enzymes. In addition, the SEM images of CNTs/DNA nanoparticles showed that these nanoparticles were rod-shaped with lengths around 100–200 nm. The fluorescence microscope results from German chamomile cells treated with CTNs/ssDNA-FITC nanoparticles showed the ability of these nanoparticles to transfer ssDNA-FITC to German chamomile cells. The results also revealed that the simultaneous use of ultrasound and CNTs significantly increased the transfer efficiency of ssDNA-FITC.

Synthesizing carbon nanotubes in space

Context. As the fourth most abundant element in the universe, carbon (C) is widespread in the interstellar medium (ISM) in various allotropic forms (e.g. fullerenes have been identified unambiguously in many astronomical environments, the presence of polycyclic aromatic hydrocarbon molecules in space has been commonly acknowledged, and presolar graphite, as well as nanodiamonds, have been identified in meteorites). As stable allotropes of these species, whether carbon nanotubes (CNTs) and their hydrogenated counterparts are also present in the ISM or not is unknown. Aims. The aim of the present works is to explore the possible routes for the formation of CNTs in the ISM and calculate their fingerprint vibrational spectral features in the infrared (IR). Methods. We studied the hydrogen-abstraction and acetylene-addition (HACA) mechanism and investigated the synthesis of nanotubes using density functional theory (DFT). The IR vibrational spectra of CNTs and hydrogenated nanotubes (HNTs), as well as their cations, were obtained with DFT. Results. We find that CNTs could be synthesized in space through a feasible formation pathway. CNTs and cationic CNTs, as well as their hydrogenated counterparts, exhibit intense vibrational transitions in the IR. Their possible presence in the ISM could be investigated by comparing the calculated vibrational spectra with astronomical observations made by the Infrared Space Observatory, Spitzer Space Telescope, and particularly the upcoming James Webb Space Telescope.

Layer-by-layer deposition of cationic and anionic carbon nanotubes into thin films with improved electrical properties

In this study, the electrical properties of carbon nanotubes (CNTs) assembled into different architectures using the layer-by-layer technique have been investigated. The CNTs were modified with either anionic water-soluble polyaniline blend poly(sodium 4-styrenesulfonate) (PANI-PSS) or cationic poly(diallydimethyl ammonium chloride) (PDADMAC) to form negatively charged CNT− and positively charged CNT+. PANI-PSS was synthesized by interfacial polymerization of aniline using PSS as template. The first of the three architectures studied was assembled by the LbL deposition of anionic CNT− and cationic CNT+ while the two others were prepared by the deposition of only 1 type of CNTs (CNT+ or CNT−) with an oppositely charged polyelectrolyte to form PDADMAC/CNT− and PANI-PSS/CNT+. The thickness and surface roughness of the three different films were characterized by atomic force microscopy (AFM) while the electrical and optical properties were measured using a four points probe setup and a UV–vis spectrophotometer, respectively. The dispersion of the CNTs using PANI-PSS as capping agent was the least efficient when compared to the PDADMAC leading to a lower adsorption on a charged substrate. Interestingly, the layer-by-layer deposition of the CNT−/CNT+ films had a slower growth but displayed a superior electrical conductivity when compared to the other two architectures.

Polyamine functionalized carbon nanotubes: synthesis, characterization, cytotoxicity and siRNA binding

In this work we have synthesized a new series of cationic carbon nanotubes (CNTs) for siRNA binding. Both single- and multi-walled CNTs have been modified by addition or amidation reaction with short linear polyamine chains including putrescine, spermidine and spermine. All the new conjugates have been characterized with several spectroscopic and microscopic techniques. Their cytotoxic effects have been assessed on human lung carcinoma cell line. Finally, we have analyzed their capacity to bind siRNA towards the development of new carriers for gene silencing applications. The dispersibility properties and the capacity to complex siRNA of the different conjugates were found to be strongly dependent on the position of the functional groups on CNTs (i.e. mainly at the tips following the amidation reaction or on the sidewalls by direct C–C addition).

Layer-by-layer electrostatic self-assembly of anionic and cationic carbon nanotubes

The layer-by-layer (LBL) self-assembly of anionic and cationic multi-walled carbon nanotubes (MWNTs) through electrostatic interaction has been carried out to fabricate all-MWNT multilayer films. The alternate uniform assembly of anionic and cationic MWNTs was investigated by UV–vis spectroscopy. Scanning electron microscopy (SEM) images displayed the growth of the MWNT films.

Functionalized Carbon Nanotubes in Drug Design and Discovery

Carbon nanotubes (CNTs) have been proposed and actively explored as multipurpose innovative carriers for drug delivery and diagnostic applications. Their versatile physicochemical features enable the covalent and noncovalent introduction of several pharmaceutically relevant entities and allow for rational design of novel candidate nanoscale constructs for drug development. CNTs can be functionalized with different functional groups to carry simultaneously several moieties for targeting, imaging, and therapy. Among the most interesting examples of such multimodal CNT constructs described in this Account is one carrying a fluorescein probe together with the antifungal drug amphotericin B or fluorescein and the antitumor agent methotrexate. The biological action of the drug in these cases is retained or, as in the case of amphotericin B constructs, enhanced, while CNTs are able to reduce the unwanted toxicity of the drug administered alone. Ammonium-functionalized CNTs can also be considered very promising vectors for gene-encoding nucleic acids. Indeed, we have formed stable complexes between cationic CNTs and plasmid DNA and demonstrated the enhancement of the gene therapeutic capacity in comparison to DNA alone. On the other hand, CNTs conjugated with antigenic peptides can be developed as a new and effective system for synthetic vaccine applications. What makes CNTs quite unique is their ability, first shown by our groups in 2004, to passively cross membranes of many different types of cells following a translocation mechanism that has been termed the nanoneedle mechanism. In that way, CNTs open innumerable possibilities for future drug discovery based on intracellular targets that have been hard to reach until today. Moreover, adequately functionalized CNTs as those shown in this Account can be rapidly eliminated from the body following systemic administration offering further encouragment for their development. CNT excretion rates and accumulation in organs and any reactivity with the immune system will determine the CNT safety profile and, consequently, any further pharmaceutical development. Caution is advised about the need for systematic data on the long-term fate of these very interesting and versatile nano-objects in correlation with the type of CNT material used. CNTs are gradually plyaing a bigger and more important role in the emerging field of nanomedicine; however, we need to guarantee that the great opportunities they offer will be translated into feasible and safe constructs to be included in drug discovery and development pipelines.