Theoretical study of ciprofloxacin antibiotic trapping on graphene or boron nitride oxide nanoflakes.

Reactions between the antibacterial fluoroquinolone agent ciprofloxacin (CIP) and organic hydrophilic nanoflakes (graphene oxide and boron nitride oxide) have been studied in aqueous medium using density functional theory (DFT), time-dependent density functional theory (TD-DFT), and molecular dynamics (MD) simulations. We found that CIP molecules in π-π electron donor-acceptor (EDA) reaction preserve their optical properties in water when adsorbed on hydrophilic nanoflakes. Moreover, MD calculations aimed at studying the diffusive translocation of CIP to lipid membrane showed that the choice of the hydrophilic nanovectors is primordial to stabilize the molecule on the cellular membrane and improve cytotoxic effects.

TRAIL-NP hybrids for cancer therapy: a review.

Cancer is a worldwide health problem. It is now considered as a leading cause of morbidity and mortality in developed countries. In the last few decades, considerable progress has been made in anti-cancer therapies, allowing the cure of patients suffering from this disease, or at least helping to prolong their lives. Several cancers, such as those of the lung and pancreas, are still devastating in the absence of therapeutic options. In the early 90s, TRAIL (Tumor Necrosis Factor-related apoptosis-inducing ligand), a cytokine belonging to the TNF superfamily, attracted major interest in oncology owing to its selective anti-tumor properties. Clinical trials using soluble TRAIL or antibodies targeting the two main agonist receptors (TRAIL-R1 and TRAIL-R2) have, however, failed to demonstrate their efficacy in the clinic. TRAIL is expressed on the surface of natural killer or CD8+ T activated cells and contributes to tumor surveillance. Nanoparticles functionalized with TRAIL mimic membrane-TRAIL and exhibit stronger antitumoral properties than soluble TRAIL or TRAIL receptor agonist antibodies. This review provides an update on the association and the use of nanoparticles associated with TRAIL for cancer therapy.

Encapsulation capacity and natural payload delivery of an anticancer drug from boron nitride nanotube.

The behavior of confined anticancer carboplatin (CPT) molecules in a single (10, 10) boron nitride nanotube (BNNT) was studied by means of molecular dynamics simulations. Our study revealed a very large storage capacity of BNNT. Analysis of the energy profiles depending on the number of confined molecules, and on their spatial organization allowed us to quantify the ability of BNNT to vectorize CPT. Indeed, BNNT despite its small radius presented a large inner volume that favored stable encapsulation of multiple active anticancer molecules. Moreover, in our molecular dynamics simulations, the empty BNNT and the BNNT filled with CPT diffused spontaneously to the cell membrane and were able to passively enter inside lipid bilayers by a lipid-assisted mechanism. This property has been used to deliver naturally anticancer drugs to cellular targets. Using this enhanced drug delivery system, we have provided a definitive solution to the problem of drug release and have thus opened up a new way of targeting cancer cells. Indeed, regardless of the mode of action of the platinum complex towards the cell, the delivery of the drug on site should limit the side effects of the drug.

Experimental and simulation studies of unusual current blockade induced by translocation of small oxidized PEG through a single nanopore.

Detection of a single macromolecule based on the use of artificial nanopores is an attractive and promising field of research. In this work, we report a device based on a 5 nm single nanopore with a high length/diameter ratio, tailored by the track etching and atomic layer deposition techniques. The translocation of neutral polyethylene glycol (PEG) and charged polyethylene glycol-carboxylate (PEG-carboxylate) molecules of low molar masses (200 and 600 g mol(-1)) through this nanodevice was studied. It was shown that charged PEG-carboxylate molecules, which permeate through the pore, promote an unusual blockade of ionic current whereas the neutral PEG molecules do not show such behaviour. The molecular dynamics simulation shows that both neutral and charged PEGs permeate through the nanopore close to its inner surface. The main difference between the two macromolecules is the existence of a structured shell of cations around the charged PEG, which is likely to cause the observed unusual current blockade.

Supramolecular self-assembly of brominated molecules on a silicon surface.

Hydrogen and halogen bonds have been associated for the growth of 2D compact supramolecular networks on a silicon surface. These interactions have been elucidated in a complete monolayer of a 4,4''-dibromo-p-terphenyl (DBT) molecule on a Si(111)-B surface by combining scanning tunneling microscopy (STM) and density functional theory (DFT) calculations.

Theoretical study of amino derivatives and anticancer platinum drug grafted on various carbon nanostructures.

Density functional theory calculations with van der Waals approximation have been conducted to analyze the functionalization of various carbon-based nanostructures (fullerene, metallic, and semi-conducting nanotubes) with amino derivative groups. The results obtained with azomethine, show the formation of a five membered ring on fullerenes, and on nanotubes consistent with experimental observations. The attachment of an azomethine plus subsequent drug like a Pt(IV) complex does not perturb the cycloaddition process. Moreover, all theoretical results show that the length of different amino derivatives with subsequent Pt(IV) complex does not affect the complexed therapeutic agent when it is attached onto these carbon-based nanostructures.

Insertion kinetics of small nucleotides through single walled carbon nanotube.

We report molecular dynamic simulations showing that a DNA molecule constituted by five unique bases can be spontaneously inserted into single walled carbon nanotube (SWCNT) in normal conditions (P, T and water environment) depending on the tube radius value. The van der Waals and electrostatic interactions play a central role for the rapid insertion process. Our study shows also that the Guanine molecule inserts the fastest compared to thymine, adenine and cytosine bases, respectively. The differences of insertion time could be exploited for applications concerning for example DNA sequencing.

Benefit of adjuvant trastuzumab-based chemotherapy in T1ab node-negative HER2-overexpressing breast carcinomas: a multicenter retrospective series.

BACKGROUND: Randomized clinical trials showed the benefit of adjuvant trastuzumab-based chemotherapy (ATBC) for node-positive and/or >1 cm HER2+ breast carcinomas. No efficacy data have been published on ATBC in large series of pT1abN0 HER2+ tumors. PATIENTS AND METHODS: This retrospective study evaluated 276 cases of pT1abN0 HER2+ breast tumors in eight French cancer centers. Factors associated with prognosis and ATBC prescription were analyzed. RESULTS: A total of 129 cases (47%) were treated with ATBC (ATBC+), 19 with chemotherapy alone, 5 with trastuzumab alone, and 123 (45%) with neither trastuzumab nor chemotherapy (ATBC-). ATBC use was associated with the date of diagnosis (before or after June 2005) and with poor prognostic features. At a median follow-up of 44 months, there were 13 recurrences in the ATBC- group and 2 in the ATBC+ group. ATBC was associated with a significant survival benefit (99% 40-month disease-free survival for ATBC+ versus 93% for ATBC- cases; P = 0.018). Lack of hormone receptors (HRs) and the presence of lymphovascular invasion (LVI) were significantly associated with a poor prognosis and a greater benefit of ATBC. CONCLUSIONS: ATBC was associated with a significantly reduced risk of recurrence in pT1abN0 HER2+ tumors, and was more beneficial in HR- and/or LVI+ tumors.

Control of carbon nanotube handedness using a supramolecular chiral surface.

Sorting diameter and handedness of carbon nanotubes still appears as an important challenge in nanotechnology. In this context, supramolecular structures formed by self-assembled chiral molecules deposited on well-defined metal surfaces can be used to discriminate the two isomers of carbon nanotubes. Calculations are carried out to determine the adsorption energy of nanotube enantiomers on alaninate coated Cu(110) surface. The results show a significant discrimination of the L and R handed isomers by such a surface and an additional selectivity in terms of small and large tube diameters.

Chiral interaction in double-wall carbon nanotubes: simple rules deduced from a large sampling of tubes.

We study a large sampling of chiral double-wall carbon nanotubes to propose simple formula describing the dependence of the interwall energy, the chiral discrimination energy, and the radial breathing mode frequencies as a function of the main characteristics of the tubes, i.e., their radius, length and chiral angle. It is shown that tube pairs with the same handedness are more stable than enantiomeric pairs, and this discrimination, though small, mainly occurs in the first step of the growth of an inner tube inside an outer one. Chiral splittings of the breathing mode frequencies for the two DWCNT diastereoisomers (n(i),m(i))@(n(o),m(o)) and (m(i),n(i))@(n(o),m(o)) can reach a few wave numbers.

Detection of amino acids encapsulation and adsorption with dielectric carbon nanotube.

Calculations of the interaction energy and dielectric responses of single-walled carbon nanotubes to the presence of amino acid inside (encapsulation) or outside (adsorption) the nanotube are carried out. It is shown that the frequency shifts of selected nanotubes conveniently tailored to the size of the probed molecules and used in a resonator configuration can selectively detect the position (encapsulated or adsorbed in the tube) of different species. We demonstrate in particular that adsorption outside the nanotube is better detected than encapsulation whatever the amino acid tested. Without explicitly dealing with drug delivery, these calculations represent the first step toward the detection of amino acids encapsulation in potential drug vector.

Enantioselectivity of amino acids using chiral sensors based on nanotubes.

The selective detection of amino acid enantiomers can be achieved by considering chiral nanotubes used in a resonator configuration. We show that this enantioselectivity is appreciably increased when a peptide molecule is inserted in the tube. The chiral polarization of the nanotube at the linear and nonlinear levels due to the inserted polar peptide is very sensitive to the adsorption of left- or right-handed alanine molecules. This leads to a difference in the resonance frequency of the sensor which can increase to 12 MHz when the nanotube is not chiral (instead of 0 for the bare tube) and can reach 38 MHz for a chiral tube (instead of 14 MHz for the bare tube). The influence of the various parameters which are responsible for such a differential frequency shift, i.e., the tube hyperpolarizability, the polar electric properties of the peptide, and the screening effect due to the tube on the peptide-alanine interactions, is discussed and some general rules are given regarding the optimization of the enantioselectivity of these sensors.

Chiral response of single walled carbon nanotube based sensors to adsorption of amino acids: a theoretical model.

Calculations of the interaction energy and dielectric responses of chiral single walled carbon nanotubes to the presence of amino acid enantiomers are carried out. A theoretical study is developed to show that the frequency shifts of selected nanotubes conveniently tailored to the size of the probed molecules and used in a resonator configuration can selectively detect different species of amino acids and the left- and right-handed enantiomers of these species. Criteria for an optimization of the adsorption energy and frequency response on the size and chiral angle of the nanotubes are given. It is found that a very small set of carbon tubes obeys these conditions.

Characterization of single wall carbon nanotubes by means of rare gas adsorption.

Based on the formalisms of Langmuir and Fowler, theoretical adsorption isotherms are calculated for different bundle geometries of single wall carbon nanotubes in a triangular lattice. The authors show the dependence of the adsorption properties on the nanotube diameter and on the specific morphology of the bundles they constitute. The authors demonstrate how isotherm curve analysis can help to experimentally determine what kinds of tubes form a given bundle and the ratio of open to closed tubes in a sample having undergone a complete or incomplete opening protocol. In spite of the model's simplicity, quite satisfactory agreement is observed between experiments and the authors' calculations.

Long nanotube dielectric properties used as sensors of large molecules: a semicontinuum approach.

A semicontinuum approach on the basis of an effective polarizability tensor per length and radius units is used to describe the dielectric response of a long single wall nanotube to the adsorption of an extended molecule. Changes in the permittivity ratio of the nanotube+molecule over the nanotube alone, which are directly connected to frequency shifts of the nanotube in a resonator configuration due to the presence of the molecule, provide a test of sensitivity of the system. The behavior of this ratio is analyzed for linear and circular geometries of the molecule, as a function of the tube characteristics (length and radius) and of the molecular size and polarizability distribution. Extension to three dimensional systems with a large set of polarizable centers is discussed in terms of self-polarization of the centers and morphology of the surface of the sensed system.

Influence of molecular adsorption on the dielectric properties of a single wall nanotube: a model sensor.

Recent measurements of the resonance frequency of a copper disk covered with carbon nanotube bundles have shown characteristic resonance shifts during exposure with various gas molecules. The shifts were interpreted as the change of the dielectric permittivity of the system forming the sensor due to the electric properties of the adsorbed molecules. Starting from a simplified sensor model formed by one single wall nanotube, we develop a self-consistent approach to describe the variation of the linear dielectric susceptibility of the tube at the atomic scale when molecules are adsorbed at its external surface. The sensitivity of this model sensor is tested as a function of the apolar or polar nature of the admolecules, their adsorption geometry, their concentration, and the characteristics of the tube (length, diameter,...). The comparison with data on dielectric constant changes vs adsorption, coming from measurements of the resonance frequency shifts, displays striking agreement for most of the molecular species considered.