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Design of tyrosine based stimuli responsive antibacterial drug delivery system with potential application in cancer therapy.

International audience; The emission of polar volatile organic compounds (VOCs) is a major worldwide concern of air quality and equally impacts the preservation of cultural heritage (CH). The challenge is to design highly efficient adsorbents able to selectively capture traces of VOCs such as acetic acid (AA) in the presence of relative humidity (RH) normally found at storage in museums (40-80%). Although the selective capture of VOCs over water is still challenging, Metal-Organic Frameworks (MOFs) possess highly tunable features (Lewis, Bronsted or redox metal sites, functional groups, hydrophobicity…) suitable to selectively capture a large variety of VOCs. In this context, we have explored the adsorption efficiency of a series of MOFs thin films (ZIF-8(Zn), MIL-101(Cr) and UiO-66(Zr)-2CF3) for the selective capture of AA based on a UV/Vis and FT-IR spectroscopic ellip-sometry in operando study (2-6% of relative pressure of AA under 40% of RH), namely conditions close to the realistic envi-ronmental storage conditions of cultural artefacts. For that purpose, optical quality thin films of MOFs were prepared by dip-coating and their AA adsorption capacity and selectivity were evaluated under humid conditions by measuring the variation of the refractive index as a function of the vapor pressures while the chemical nature of the co-adsorbed analytes (water and AA) was identified by FT-IR ellipsometry. While thin films of ZIF-8(Zn) strongly degraded when exposed to AA/water va-pors, films of MIL-101(Cr) and UiO-66(Zr)-2CF3 present a high chemical stability under those conditions. It was shown that MIL-101(Cr) presents a high AA adsorption capacity due to its high pore volume, but exhibits a poor AA adsorption selectivi-ty under humid conditions. In contrast, UiO-66(Zr)-2CF3 was shown to overpass MIL-101(Cr) in terms of AA/ H2O adsorp-tion selectivity and AA adsorption/desorption cycling stability thanks to its high hydrophobic character, suitable pore size for adequate confinement and specific interactions.

Volatile methylsiloxanes (VMSs) are common silicone degradation byproducts that cause serious concern for the contamination of sensitive electronics and optics, among others. With the goal of fast, online detection of VMS, we herein highlight the mesoporous MIL-101(Cr) MOF as a promising mass sensing layer for integration with a quartz crystal microbalance (QCM), using an in-house modified gravimetric adsorption system capable of achieving extremely low concentrations of siloxane D4 (down to 0.04 ppm), targeting applications for monitoring in indoor spaces and spacecraft. Our developed MIL-101(Cr)@QCM sensor achieves near-perfect reversibility with no hysteresis alongside excellent repeatability over cycling and fast response/recovery times under 1 min. We attribute this capability to optimum host/guest interactions as uncovered through molecular simulations.

Surface-enhanced Raman spectroscopy (SERS) of semiconducting TiO2 was used for studying binding modes and surface reactions of molecules bound at the interface but is generally limited by low signa...

International audience; Owing to their high and tunable porosity as well as great chemical diversity, metal–organic frameworks (MOFs) have shown great promise over the past 20 years for a wide range of applications, including gas storage/separation, catalysis, and biomedicine. To date, MOF nanoparticles (NPs) have mostly been obtained as polycrystalline powders or spherical nanocrystals while anisotropic MOFs nanocrystals have been less explored and are of interest in the fields of catalysis, sensing, and electronics. One of the main challenges for the practical application of MOFs is thus to control the crystal size, morphology, and multiscale porosity of these materials while developing adequate shaping strategies. In this review, we cover recent advances in the different synthetic strategies of one-dimensional (1D) MOF nanocrystals as well as hierarchical porous superstructures based on tubular MOFs. We describe the architectures based on MOFs nanotubes (NTs), nanowires (NWs), and nanorods (NRs). Our discussion is focused on the synthetic approaches that drive the structure, crystallinity, size, and morphology of these hierarchical porous hybrid materials. Finally, their potential for different applications is presented.

We report the selective formation of endoperoxides by aerobic TiO2 photocatalysis through the cyclic addition of dioxygen and a non-conjugated diene, the first heterogeneous catalytic system for endoperoxide synthesis. This green protocol does not require any additive and the photocatalyst is abundant and recyclable, providing a yield up to 64% and >20:1 diastereoselectivity. Mechanistic investigations were carried out by using product analysis, kinetic studies, O-18 labelling experiments, electron-spin resonance and a set of quenching experiments. Superoxide (but not singlet oxygen, triplet oxygen or peroxide) is directly involved in the reaction cascade to form the endoperoxide product. The new findings may be helpful for future for designing eco-friendly and energy sustainable strategies for selective oxygenation reactions using semiconductors, O2 and sunlight.

Because of the increasing prevalence of multidrug resistance feature, several investigations have been so far reported regarding the antibiotic alternative supramolecular bioactive agents made of hybrid assemblies. In this regard, it is well-established that combinational therapy inherited by assembled supramolecular structures can improve the bioactivity to some extent, but their mode of action has not been studied in detail. We provide first direct evidence that the improved mechanism of action of antimicrobial supra-amphiphilic nanocomposites differs largely from their parent antimicrobial peptide-based polymers. For the construction of a hybrid combinational system, we have synthesized side-chain peptide-based antimicrobial polymers via RAFT polymerization and exploited their cationic nature to decorate supra-amphiphilic nanocomposites via interaction with anionic polyoxometalates. Because of cooperative antimicrobial properties of both the polymer and polyoxometalate, the nanocomposites show an enhanced antimicrobial activity with a different antimicrobial mechanism. The cationic stimuli-responsive peptide-based polymers attack bacteria via membrane disruption mechanism, whereas free radical-mediated cell damage is the likely mechanism of polymer-polyoxometalate-based supra-amphiphilic nanocomposites. Thus, our study highlights the different antimicrobial mechanism of combinational systems in detail, which improves our understanding of enhanced antimicrobial efficacy.

Simultaneous CO2 reduction and water oxidation as a coupled process is an important challenge in the quest of clean energy production. Herein, we report a metal oxide based heterogeneous catalytic system, which not only couples CO2 reduction with water oxidation, but also provides very high turnover number for CO2 reduction with scalability. Such a catalytic system can simultaneously oxidize water and release the generated electrons for reduction of CO2 with a maximum turnover number and turnover frequency as high as 1.4 × 106 and 610 s−1, respectively, following effective catalyst concentration; whereas, turnover number and turnover frequency is 1366 and 1380 h−1 per mole of catalyst, respectively. The starting materials for this catalytic process are CO2 and water while the end products are oxygen and formic acid and in few cases, formaldehyde. The prospect of using the formic acid generated during our process in fuel cells to generate green energy is also worth mentioning.

In this study we have shown dislocations/defects can be introduced in the form of supramolecularly bound polyacrylic acid and urea based scaffold networks and metal oxide nanoparticles in concrete. By virtue of their supramolecular bonding sites, polyacrylic acid and urea create a network of struts. These struts act as dislocations in an otherwise uniform concrete structure which in turn increase the strength of the concrete. We have also shown that the length of these struts can also be controlled. Such a control over the strut length also led to influencing the strength of the concrete. In short we have shown that effective stress for unit matrix area can be reduced by introducing defects/dislocations in the form of struts which distribute the external applied stress. Consequently the higher the extent of dislocation, the larger is the capacity of the concrete matrix to withstand externally applied stress, the higher is its mechanical strength. We further added ZrO2 and TiO2 nanoparticles to the concrete matrix which enhance the thermal resistivity of the concrete.

A supramolecular poly-electrolyte complex (SPEC) comprising poly-electrolyte acrylic acid with supramolecularly complexed guanidium is reported. This complex shows pH responsive phase transitions, which are described and characterized using microscopy, spectroscopy, density functional theory studies and Monte Carlo simulations. The phase behaviour of the SPEC is exploited by loading a dye like perylene and a drug, viz., doxorubicin, and their pH dependent controlled release is demonstrated, owing to the pH dependent phase change of the SPEC.

DOI: 10.1021/acs.inorgchem.5b02570 URL: http://pubs.acs.org/doi/abs/10.1021/acs.inorgchem.5b02570 Filiació URV: SI The formation pathway of a closed spherical cluster [Mo132], starting from a library of building blocks of molybdate anions, has been reported. Electrospray ionization mass spectrometry, Raman spectroscopy, and theoretical studies describe the formation of such a complex cluster from a reduced and acidified aqueous solution of molybdate. Understanding the emergence of such an enormous spherical model cluster may lead to the design of new clusters in the future. Formation of such a highly symmetric cluster is principally controlled by charge balance and the emergence of more symmetric structures at the expense of less symmetric ones.

Along with other properties, superior gas permeation behavior would impart an extra dimension to multifunctional natural rubber (NR) nanocomposites used in various applications, like tires. For the first time, the impact on thermodynamics and kinetics of oxygen transport has been evaluated for nano, micro, and dual filler based multifunctional NR nanocomposites through oxygen permeation studies at three different temperatures. It is seen that, the kinetics is less affected by platelet like nanofillers, while the thermodynamics and eventual permeability are not altered much by fibrous nanofillers. The permeability of the nanocomposites decreased in the presence of nanofillers due to high aspect ratio and exquisite dispersion, as ascertained from morphological studies, which caused increment in tortuosity and the reduction in free volume. Relative permeabilities were compared to predictions of existent permeation models and a novel function was successfully introduced to address deviations in a model. Finally, nearly 60% decrement in permeability of dual filler based nanocomposites explained by the formation of zeta potential driven filler associations indicate potency in development of thinner, but stronger and more durable multifunctional materials with longer air retention capabilities. These could be applied in tire research to reduce material, energy costs and increase fuel efficiencies. Copyright © 2011 John Wiley & Sons, Ltd.

Nanocomposites used in various applications, like tires, diaphragms etc. must exhibit superior gas permeation behavior along with other properties. Oxygen permeability characteristics of such multifunctional styrene butadiene rubber based nanocomposites, including thermodynamics and kinetic aspects of transport have been discussed here. For the first time, these characteristics have been determined for nano, micro and dual filler based multifunctional nanocomposites. The permeability of the nanocomposites was remarkably decreased by the presence of high loadings of montmorillonite due to high aspect ratio and exquisite dispersion, ascertained from morphological studies. The results were explained by the increment in tortuosity and also correlated with the reduction in free volume. Relative permeabilities were compared to predictions of existing permeation models and a novel function was successfully introduced to address deviations. Finally, the enhanced barrier properties of dual filler based nanocomposites have been explained by the formation of zeta potential driven “nano-blocks” and “nano-channels”.

An inexpensive, facile, and environmentally benign method has been developed for the preparation of stimuli-responsive and self-healing polyacrylic acid–chitosan-based supramolecular hydrogels. Guanidine hydrochloride is used as the supramolecular crosslinker to form an interconnected network with polyacrylic acid–chitosan complex. Because of the dynamic equilibrium between the hydrogen-bonding sites of the components, the hydrogels were found to be self-healable and sensitive to biochemical-stimulus, such as pH. Controlled loading of drug like doxorubicin and its significant anticancer activity of such hydrogels is worth mentioning.

Supramolecular Thermo Aero-able Gelators (STAGs): tartaric acid, urea, and guanidine with amide and imine moieties as supramolecular synthons are introduced to cross-link and aerate ('aero-able') polyacrylate networks for synthesis of hydrogels. They are bi-functional hence present a greener alternative to the existing cross-linkers and gelators., 9 pages, 9 figures

The thermal stability of short alkanethiol $CH_3(CH_2)_7SH (C_8)$ and long $C_1_8$ self-assembled monolayers (SAMs) is investigated using grazing angle reflection-absorption infrared spectroscopy, cyclic voltammetry, and molecular dynamics simulation. We track the disordering of SAM by untilting and gauche defect accumulation with increasing temperature in the 300-440 K range, a range of interest to tribology. Molecular dynamics simulation with both fully covered and partially covered $C_6, C_8, and C_1_8$ monolayers brings out the morphological changes in the SAM, which may be associated with the observed thermal stability characteristics. The molecular dynamics simulations reveal that short-chain $C_6$ and $C_8$ alkanethiols are more defective at lower temperature than the long-chain $C_1_8$ alkanethiol. With increasing temperature disorder in the SAM, as reflected in both untilting and gauche defect accumulation, tends to saturate at temperatures below 360 K for short-chain SAMs such that any further increase in temperature, until desorption, does not lead to any significant change in conformational order. In contrast the disorder in the long-chain $C_1_8$ SAM increases monotonically with temperature beyond 360 K. Thus, in a practical range of temperature, the ability of a SAM to retain order with increasing thermal perturbations is governed by the state of disorder prior to heat treatment. This deduction derived from molecular dynamics simulation helps to rationalize the significant difference we have observed experimentally between the thermal response of short- and long-chain thiol molecules.

Thermal stability behavior of 1H, 1H,2H,2H-perfluorooctyl trichlorosilane self-assembled on aluminum substrates is characterized using a grazing-angle Fourier transform infrared spectrometer, Fourier transform-Raman spectroscopy, and contact angle measurements. The self-assembled monolayer (SAM) is heated quasi-statically from room temperature to above 633 K with a heating rate of 1 K/s. Variations in peak frequencies, integrated areas of intensities of symmetric and antisymmetric CF2 stretches, and the relative tilt angle of the SAM are reported. We find that the conformational order in the SAM is not disrupted because of thermal cycling when the peak temperature is below 423 K. When the peak temperature is between 423 and 603 K, the cycling results in only a partial retention of the original order. When the peak temperature is above 603 K, the process is completely irreversible. Surface-enhanced Raman spectroscopy and contact angle measurements support these observations. We confirm these trends for a longer chain (1H,1H,2H,2H-perfluordecyl trichlorosilane) molecule of the same family using the same techniques. We discuss the possible reasons for the changes in light of the tilting-untilting and uncoiling-coiling of the helical silane monolayer.

DOI: 10.1021/acs.inorgchem.5b02570 URL: http://pubs.acs.org/doi/abs/10.1021/acs.inorgchem.5b02570 Filiació URV: SI The formation pathway of a closed spherical cluster [Mo132], starting from a library of building blocks of molybdate anions, has been reported. Electrospray ionization mass spectrometry, Raman spectroscopy, and theoretical studies describe the formation of such a complex cluster from a reduced and acidified aqueous solution of molybdate. Understanding the emergence of such an enormous spherical model cluster may lead to the design of new clusters in the future. Formation of such a highly symmetric cluster is principally controlled by charge balance and the emergence of more symmetric structures at the expense of less symmetric ones.