Sub-molecular spectroscopy and temporary molecular charging of Ni-phthalocyanine on graphene with STM.

In this study, the self-assembled molecular network and electronic properties of Ni-phthalocyanine (NiPc) molecules on monolayer graphene (MLG)/6H-SiC(0001) were studied by room temperature Scanning Tunnelling Microscopy (STM) and Density Functional Theory (DFT) calculations. In this study, a very weak electronic coupling between the graphene and the NiPc molecules is found. This is due to the very small charge transfer of only 0.035e- per molecule. The weak molecule-graphene interaction has two observable consequences: sub-molecular resolution was obtained in the STM spectroscopy at room-temperature with the molecules adsorbed directly on the graphene, and the occupied and unoccupied molecular resonance peaks were observed to shift their position in energy as a function of the tip-surface distance. This is due to the temporary local charging (either positive or negative) that is achieved by decreasing the surface voltage under the STM tip. This may have important consequences for future studies of the opto-electronic properties of such hybrid graphene-molecule systems.

Synthetic Modification of 9α- and 9ß-Hydroxyparthenolide by Heck or Acylation Reactions and Evaluation of Cytotoxic Activities.

Motivated by the widely reported anticancer activity of parthenolides and their derivatives, a series of new substituted parthenolides was efficiently synthesized. Structural modifications were performed at the C-9 and C-13 positions of 9α- and 9ß-hydroxyparthenolide, which were isolated from the aerial parts of Anvillea radiata. Twenty-one derivatives were synthesized and evaluated for their in vitro cytotoxic activity against HS-683, SK-MEL-28, A549, and MCF-7 human cancer cell lines using the MTT colorimetric assay. Among the derivatives, seven exhibited excellent activity compared to 5-fluorouracil and etoposide against the four cell lines tested, with IC50 values ranging from 1.1 to 9.4 µM.

Theoretical demonstration of the potentiality of boron nitride nanotubes to encapsulate anticancer molecule.

Anticancer drug transport is now becoming an important scientific challenge since it would allow localizing the drug release near the tumor cell, avoiding secondary medical effects. We present theoretical results, based on density functional theory and molecular dynamics simulations, which demonstrate the stability of functionalized single (10,10) boron nitride nanotubes (BNNTs) filled with anticancer molecule such as carboplatin (CPT). For this functionalized system we determine the dependence of the adsorption energy on the molecule displacement near the inner BNNTs surface, together with their local morphological and electrical changes and compare the values to the adsorption energy obtained on the outer surface. Quantum simulations show that the most stable physisorption state is located inside the nanotube, with no net charge transfer. This demonstrates that chemotherapeutic encapsulation is the most favorable way to transport drug molecules. The solvent effect and dispersion repulsion contributions are then taken into account using molecular dynamics simulations. Our results confirm that carboplatin therapeutic agents are not affected when they are adsorbed inside BNNTs by the surrounding water molecules.

Molecular chemisorption on passivated and defective boron doped silicon surfaces: a "forced" dative bond.

We investigate the adsorption mechanism of a single trans 4-pyridylazobenzene molecule (denoted by PAB) on a doped boron Si(111)√3×√3R30° surface (denoted by SiB) with or without boron-defects, by means of density functional theory calculations. The semiempirical approach proposed by Grimme allows us to take the dispersion correction into account. The role of the van der Waals correction in the adsorption geometries and energies is presented. In particular, two adsorption configurations are electronically studied. In the first one, the molecule is parallel to the surface and interacts with the SiB surface via the -N=N- bond. In the presence of a boron-defect, a Si-N chemical bond between the molecule and the surface is then formed, while electrostatic or/and van der Waals interactions are observed in the defectless surface. In the second adsorption configuration, the molecule presents different orientations with respect to the surface and interacts via the nitrogen atom of the pyridyl part of the PAB molecule. If the molecule is perpendicular to the perfect SiB surface, the lone-pair electrons associated with the heterocyclic nitrogen atom fill the empty dangling bond of a silicon adatom via a dative bond. Finally, in the presence of one boron-defect, the possibility of a "forced" dative bond, corresponding to a chemical bond formation between the PAB molecule and the silicon electron occupied dangling bond, is emphasized.

Quantum study of boron nitride nanotubes functionalized with anticancer molecules.

Full DFT-D2 calculations were carried out to study the interactions between single wall (10,10) boron nitride nanotubes (BNNTs) and different molecules, such as azomethine (C2H5N) and an anticancer agent (Pt(IV) complex) linked to an amino-derivative chain. The geometry of the (10,10) BNNT-azomethine and the BNNT-amino derivative system was optimised by considering different molecular configurations on the inner and outer surfaces of the nanotube. Simulation results showed that the most stable physisorption state for both molecules was located inside the nanotube in a parallel configuration. We showed also that the molecular chemisorption was possible only when the azomethine was present above two adjacent B and N atoms of a hexagon. The attachment of an azomethine plus a subsequent drug did not perturb the cycloaddition process. Moreover, all theoretical results showed that the therapeutic agent complex was not affected when it was attached onto BNNTs.

A new assisted molecular cycloaddition on boron doped silicon surfaces: a predictive DFT-D study.

In the framework of the Density Functional Theory (DFT-D), we investigate the phthalocyanine (H2Pc) molecule adsorption on SiC(0001)3 × 3 and Si(111)√3 × âˆš3R30°-B (SiB) surfaces, and particularly compare the involved molecular adsorptions. In the H2Pc-SiC(0001)3 × 3 system, the molecular adsorption can be ascribed to a [10+2] cycloaddition. The H2Pc-SiB system is considered in three cases: defectless SiB surface (denoted SiB-0D) and SiB surfaces presenting one or two boron defects (denoted SiB-1D and SiB-2D respectively). The SiB-0D surface is passivated by a charge transfer from the Si adatoms to the boron atoms and therefore no chemical bond between the molecule and the substrate is observed. A similar molecular adsorption as already evidenced in the H2Pc-SiC(0001)3 × 3 system is involved in the SiB-2D case. In the case of the SiB-1D surface, two Si-N bonds (Si1-N1 and Si2-N2) are observed. One of them, Si1-N1, is nearly similar to that found in the H2Pc-SiB-2D system, but the Si2-N2 bond is unexpected. The Bader charge analysis suggests that, in the presence of the H2Pc molecule, the boron atoms behave like an electron reservoir whose availability varies following the involved molecular adsorption process. In the SiB-1D case, charges are transferred from the substrate to the molecule, allowing the Si2-N2 bond formation. Such a kind of molecular adsorption, not yet observed, could be designed by "assisted pseudo cycloaddition".

C60 molecules grown on a Si-supported nanoporous supramolecular network: a DFT study.

C60 fullerene assemblies on surfaces have attracted considerable attention because of their remarkable electronic properties. Now because of the competition between the molecules-substrate and the molecule-molecule interactions, an ordered C60 array is rather difficult to obtain on silicon surfaces. Here we present density functional theory simulations on C60 molecules deposited on a TBB (1,3,5-tri(1'-bromophenyl)benzene) monolayer lying on the Si(111)-boron surface (denoted SiB). The C60 molecules are located in the nanopores formed by the TBB network. Adsorption energy calculations show that the SiB surface governs the C60 vertical position, whereas the TBB network imposes the C60 lateral position, and stabilizes the molecule as well. The low charge density between the C60 and the SiB substrate on one hand, and on the other hand between the C60 and the TBB molecules, indicates that no covalent bond is formed between the C60 and its environment. However, according to charge density differences, a drastic charge reorganisation takes place between the Si adatoms and the C60 molecule, but also between the C60 and the surrounding TBB molecules. Finally, calculations show that a C60 array sandwiched between two TBB molecular layers is stable, which opens up the way to the growth of 3D supramolecular networks.

Optoelectronic Readout of Single Er Adatom's Electronic States Adsorbed on the Si(100) Surface at Low Temperature (9 K).

Integrating nanoscale optoelectronic functions is vital for applications such as optical emitters, detectors, and quantum information. Lanthanide atoms show great potential in this endeavor due to their intrinsic transitions. Here, we investigate Er adatoms on Si(100)-2×1 at 9 K using a scanning tunneling microscope (STM) coupled to a tunable laser. Er adatoms display two main adsorption configurations that are optically excited between 800 and 1200 nm while the STM reads the resulting photocurrents. Our spectroscopic method reveals that various photocurrent signals stem from the bare silicon surface or Er adatoms. Additional photocurrent peaks appear as the signature of the Er adatom relaxation, triggering efficient dissociation of nearby trapped excitons. Calculations using density functional theory with spin-orbit coupling correction highlight the origin of the observed photocurrent peaks as specific 4f→4f or 4f→5d transitions. This spectroscopic technique can facilitate optoelectronic analysis of atomic and molecular assemblies by offering insight into their intrinsic quantum properties.

Cell surface lectin array: parameters affecting cell glycan signature.

Among the "omics", glycomics is one of the most complex fields and needs complementary strategies of analysis to decipher the "glycan dictionary". As an alternative method, which has developed since the beginning of the 21st century, lectin array technology could generate relevant information related to glycan motifs, accessibility and a number of other valuable insights from molecules (purified and non-purified) or cells. Based on a cell line model, this study deals with the key parameters that influence the whole cell surface glycan interaction with lectin arrays and the consequences on the interpretation and reliability of the results. The comparison between the adherent and suspension forms of Chinese Hamster Ovary (CHO) cells, showed respective glycan signatures, which could be inhibited specifically by neoglycoproteins. The modifications of the respective glycan signatures were also revealed according to the detachment modes and cell growth conditions. Finally the power of lectin array technology was highlighted by the possibility of selecting and characterizing a specific clone from the mother cell line, based on the slight difference determination in the respective glycan signatures.

Electrophoretically mediated microanalysis for in-capillary electrical cell lysis and fast enzyme quantification by capillary electrophoresis.

In this study, a novel capillary electrophoresis (CE)-based enzymatic assay was developed to evaluate enzymatic activity in whole cells. ß-Galactosidase expression was used as an example, as it is a biomarker for assessing replicative senescence in mammalian cells. It catalyzes the hydrolysis of para-nitrophenyl-ß-D-galactopyranoside (PNPG) into para-nitrophenol (PNP). The CE-based assay consisted of four main steps: (1) hydrodynamic injection of whole intact cells into the capillary, (2) in-capillary lysis of these cells by using pulses of electric field (electroporation), (3) in-capillary hydrolysis of PNPG by the ß-galactosidase--released from the lysed cells--by the electrophoretically mediated microanalysis (EMMA) approach, and (4) on-line detection and quantification of the PNP formed. The developed method was applied to Escherichia coli as well as to human keratinocyte cells at different replicative stages. Results obtained by CE were in excellent agreement with those obtained from off-line cell lysates which proves the efficiency of the in-capillary approach developed. This work shows for the first time that cell membranes can be disrupted in-capillary by electroporation and that the released enzyme can be subsequently quantified in the same capillary. Enzyme quantification in cells after their in-capillary lysis has never been conducted by CE. The developed CE approach is automated, economic, eco-friendly, and simple to conduct. It has attractive applications in bacteria or human cells for early disease diagnostics or insights for development in biology.

Full DFT-D description of a nanoporous supramolecular network on a silicon surface.

We present a full density-functional-theory study taking into account the van der Waals interactions of a 2D supramolecular network adsorbed on the Si(111)√3x√3R30°-boron surface denoted SiB. We show that, contrarily to the previous calculations [B. Baris, V. Luzet, E. Duverger, Ph. Sonnet, F. Palmino, and F. Chérioux, Angew. Chem., Int. Ed. 50, 4094 (2011)] molecule-molecule interactions are attractive, thanks to van der Waals corrections which are essential to describe such systems. We confirm the importance of the substrate effect to achieve the molecular network on the boron doped silicon surface without covalent bond. Our simulated STM images, calculated in the framework of the bSKAN code, give better agreement with the experimental STM images than those obtained by the integrated LDOS calculations within the Tersoff-Hamann approximation. The tungsten tip presence is essential to retrieve three paired lobes as observed experimentally. The observed protrusions arise from the phenyl arms located above silicon adatoms.

Nanovectorization of Ivermectin to avoid overdose of drugs.

Ivermectin is an antiparasitic drug that results in the death of the targeted parasites using several mechanical actions. While very well supported, it can induce in rare cases, adverse effects including coma and respiratory failure in case of overdose. This problem should be solved especially in an emergency situation. For instance, the first pandemic of the 21th century was officially declared in early 2020, and while several vaccines around the worlds have been used, an effective treatment against this new strain of coronavirus, better known as SARS-CoV-2, should also be considered, especially given the massive appearance of variants. From all the tested therapies, Ivermectin showed a potential reduction of the viral portability, but sparked significant debate around the dose needed to achieve these positive results. To answer this general question, we propose, using simulations, to show that the nanovectorization of Ivermectin on BN oxide nanosheets can increase the transfer of the drug to its target and thus decrease the quantity of drug necessary to cope with the disease. This first application could help science to develop such nanocargo to avoid adverse effects.Communicated by Ramaswamy H. Sarma.

DFT-D studies of single porphyrin molecule on doped boron silicon surfaces.

We present a theoretical study in the framework of density functional calculations, taking into account the van der Waals interactions (DFT-D) of isolated Cu-5,10,15,20-tetrakis(3,5-di-tert-butyl-phenyl) porphyrin (Cu-TBPP) molecules in a C2v conformation adsorbed on a Si(111)√3x√3R30°-boron surface [denoted Si(111)-B]. With this approach, we investigate interactions between perfect or boron-defect Si(111)-B substrates and the Cu-TBPP molecule as well as the consequences of demetallation of Cu-TBPP. For each model, we determine the structural equilibrium, the spatial charge-density distribution and the electronic properties of the ground state. We conclude that there is potential for Si adatom capture by a porphyrin without strong modification of the porphyrin response, as seen from simulated scanning tunneling microscopy (STM) images.

A potential solution to avoid overdose of mixed drugs in the event of Covid-19: Nanomedicine at the heart of the Covid-19 pandemic.

Since 2020, the world is facing the first global pandemic of 21st century. Among all the solutions proposed to treat this new strain of coronavirus, named SARS-CoV-2, the vaccine seems a promising way but the delays are too long to be implemented quickly. In the emergency, a dual therapy has shown its effectiveness but has also provoked a set of debates around the dangerousness of a particular molecule, hydroxychloroquine. In particular, the doses to be delivered, according to the studies, were well beyond the acceptable doses to support the treatment without side effects. We propose here to use all the advantages of nanovectorization to address this question of concentration. Using quantum and classical simulations we will show in particular that drug transport on boron nitrogen oxide nanosheets increases the effectiveness of the action of these drugs. This will definitely allow to decrease the drug quantity needing to face the disease.

Two-Dimensional Functionalized Ultrathin Semi-Insulating CaF2 Layer on the Si(100) Surface at a Low Temperature for Molecular Electronic Decoupling.

The ability to precisely control the electronic coupling/decoupling of adsorbates from surfaces is an essential goal. It is important for fundamental studies not only in surface science but also in several applied domains including, for example, miniaturized molecular electronic or for the development of various devices such as nanoscale biosensors or photovoltaic cells. Here, we provide atomic-scale experimental and theoretical investigations of a semi-insulating layer grown on a silicon surface via its epitaxy with CaF2. We show that, following the formation of a wetting layer, the ensuing organized unit cells are coupled to additional physisorbed CaF2 molecules, periodically located in their surroundings. This configuration shapes the formation of ribbons of stripes that functionalize the semiconductor surface. The obtained assembly, having a monolayer thickness, reveals a surface gap energy of ∼3.2 eV. The adsorption of iron tetraphenylporphyrin molecules on the ribbons of stripes is used to estimate the electronic insulating properties of this structure via differential conductance measurements. Density functional theory (DFT) including several levels of complexity (annealing, DFT + U, and nonlocal van der Waals functionals) is employed to reproduce our experimental observations. Our findings offer a unique and robust template that brings an alternative solution to electronic semi-insulating layers on metal surfaces such as NaCl. Hence, CaF2/Si(100) ribbon of stripe structures, whose lengths can reach more than 100 nm, can be used as a versatile surface platform for various atomic-scale studies of molecular devices.

Influence of nanotube section on carboplatin confinement.

The confinement of anticancer carboplatin molecules (CBPT) in boron nitride nanotubes (BNNTs) with various sections was studied by means of density functional theory and molecular dynamic simulations. We show that the molecular insertion in BNNT is favored depending on the tube radius. The range of the energy adsorption varied from -1 eV to -2 eV depending on BNNT dimension. We also determined the critical diameter for the possible vectorization of the anticancer molecule. Indeed, the hydrophobicity of small BNNT radius R < 5.5 Å) is so large that CBPT encapsulation is impossible to achieve. On the contrary, a larger radius could offer an ideal situation to enhance drug delivery and allow a progressive release of the therapeutic near its target. Comparison with carbon nanotubes allowed us to draw conclusions on the best adapted nanovector for CBPT.

Complete supramolecular self-assembled adlayer on a silicon surface at room temperature.

The engineering of a complete adlayer of organic nanolines by supramolecular self-assembly has been achieved for the first time on a silicon-based surface at room temperature and has been studied by scanning tunneling microscopy. This complete adlayer has been successfully obtained thanks to the combination of a specific Si(111)-B square root 3x square root 3R30 degrees semiconductive surface and of strong hydrogen bonds between a pair of dipolar molecules.

Room-temperature electronic template effect of the SmSi(111)-8x2 interface for self-alignment of organic molecules.

This work describes an innovative concept for the development of organized molecular systems based on the template effect of the pre-structured semi-conductive SmSi(111) interface. This substrate is selected because Sm deposition in the submonolayer range leads to a 8x2-reconstruction, which is a well-defined one-dimensional semi-metallic structure. Adsorption of aromatic molecules [1,4-di-(9-ethynyltriptycenyl)-benzene] on SmSi(111)- 8x2 and Si(111)-7x7 interfaces is investigated by scanning tunneling microscopy (STM) at room temperature. Density functional theory (DFT) and semi-empirical (ASED+) calculations define the nature of the molecular adsorption sites of the target molecule on SmSi as well as their self-alignment on this interface. Experimental data and theoretical results are in good agreement.

Molecular characterization of cell death induced by a compatible interaction between Fusarium oxysporum f. sp. linii and flax (Linum usitatissimum) cells.

The cellular and molecular events associated with cell death during compatible interaction between Fusarium oxysporum sp. linii and a susceptible flax (Linum usitatissimum) cell suspension are reported here. In order to determine the physiological and molecular sequence of cell death of inoculated cells, reactive oxygen species (ROS) production, mitochondrial potential, lipoxygenase, DNase, protease and caspase-3-like activities, lipid peroxidation and secondary metabolite production were monitored. We also used microscopy, in situ terminal deoxynucleotidyl transferase-mediated dUTP nick end labelling (TUNEL) and DNA fragmentation assay. Cell death was associated with specific morphological and biochemical changes that are generally noticed in hypersensitive (incompatible) reaction. An oxidative burst as well as a loss of mitochondrial potential of inoculated cells, an activation of lipoxygenase and lipid peroxidation were noted. Enzyme-mediated nuclear DNA degradation was detectable but oligonucleosomal fragmentation was not observed. Caspase-3-like activity was dramatically increased in inoculated cells. Phenylpropanoid metabolism was also affected as demonstrated by activation of PAL and PCBER gene expressions and reduced soluble lignan and neolignan contents. These results obtained in flax suggest that compatible interaction triggers a cell death sequence sharing a number of common features with the hypersensitive response observed in incompatible interaction and in animal apoptosis.

Simulations of a Graphene Nanoflake as a Nanovector To Improve ZnPc Phototherapy Toxicity: From Vacuum to Cell Membrane.

We propose a new approach to improving photodynamic therapy (PDT) by transporting zinc phthalocyanine (ZnPc) in biological systems via a graphene nanoflake, to increase its targeting. Indeed, by means of time-dependent density functional theory simulations, we show that the ZnPc molecule in interaction with a graphene nanoflake preserves its optical properties not only in a vacuum but also in water. Moreover, molecular dynamic simulations demonstrate that the graphene nanoflake/ZnPc association, as a carrier, permits one to stabilize the ZnPc/graphene nanoflake system on the cellular membrane, which was not possible when using ZnPc alone. We finally conclude that the graphene nanoflake is a good candidate to transport and stabilize the ZnPc molecule near the cell membrane for a longer time than the isolated ZnPc molecule. In this way, the choice of the graphene nanoflake as a nanovector paves the way to ZnPc PDT improvement.