clay and beidellite

Studies on the immobilization of oxindolimine‑copper(II) or zinc(II) complexes [ML] in synthetic beidellite (BDL) clay were developed to obtain a suitable inorganic carrier capable of promoting the modified-release of metallopharmaceuticals. Previous investigations have shown that the studied metal complexes are promising antitumor agents, targeting DNA, mitochondria, and some proteins. They can bind to DNA, causing oxidative damage via formation of reactive oxygen species (ROS). In mitochondria they lead to a decrease in membrane potential, acting as decoupling agents, and therefore efficiently inducing apoptosis. Additionally, they inhibit human topoisomerase IB and cyclin dependent kinases, proteins involved in the cell cycle. BDL clays in the sodium form were synthesized under hydrothermal conditions and characterized by a set of physicochemical techniques while the BDL-[ML] hybrid materials were prepared by ion exchange method. The characterization of pristine clay and the obtained hybrids were performed by Infrared, Raman, electron paramagnetic resonance and energy dispersive X-ray spectroscopies, thermogravimetric analysis, scanning electron microscopy, X-ray powder diffraction, specific surface area, zeta potential and surface ionic charge measurements. The [ML] release assays under the same cell incubation conditions were performed monitoring metals by X-ray fluorescence. The BDL-[CuL] hybrid materials were stable and able to derail tumor HeLa cells, with corresponding IC

Topics: Antineoplastic Agents; Clay; Coordination Complexes; DNA; HeLa Cells; Humans; Zinc

Chitosan (CS) and purified sodium beidellite (Na-Bd) were used to obtain a nanocomposite able to carry anionic pharmaceutical ingredients. Diclofenac sodium (DS) was chosen as a model drug and was loaded by intercalation solution technique. Solid state characterization of the resultant hybrids was performed, including X-ray diffraction, Fourier transformed infrared spectroscopy, Thermal analysis and high resolution transmission electron microscopy coupled with energy dispersive X-Ray analysis. Drug loading capacity and encapsulation efficiency were quantified by measuring equilibrium concentration by UV-Vis spectroscopy at 276 nm. Solid-state characterization of the samples confirmed both chemical and physical interaction of DS with the nanocomposites. High drug loading along with a modified cumulative release of the drug in simulated intestinal fluid was obtained. The developed clay/polymer hybrids can act as potential candidates for the design of modified dosage forms of anionic drugs.

Topics: Aluminum Silicates; Calorimetry, Differential Scanning; Chitosan; Clay; Diclofenac; Drug Carriers; Drug Compounding; Drug Delivery Systems; Drug Liberation; Nanocomposites; Spectrometry, X-Ray Emission; Spectroscopy, Fourier Transform Infrared; Thermogravimetry; X-Ray Diffraction

Exploring the interaction of nucleic acids with clay minerals is important to understand such issues as the persistence in soils of biomolecules and the appearance of genetic polymers in prebiotic environments. Colloidal dispersions of double stranded DNA and clay nanosheets may also provide interesting model systems to study the statistical physics of mixtures of semi-flexible rods and plates. Here, we show that adding very small amounts of DNA to liquid-crystalline montmorillonite and beidellite smectite clay suspensions strongly widens the isotropic/nematic phase coexistence region. Moreover, a spectroscopic study shows that, upon DNA addition, the first DNA molecules adsorb onto the clay particles. Remarkably, synchrotron small-angle X-ray scattering experiments reveal that the average distance between the clay sheets, in the nematic phase at coexistence, decreases with increasing DNA concentration and that the inhibition of swelling by DNA becomes almost independent of clay concentration. We interpret this DNA-mediated attraction between clay nanosheets by bridging conformations of DNA strands (plates on a string structure). In addition to bridging, DNA chains can form "loops" between sections adsorbed on the same particle, giving rise to sheet repulsions due to protruding loops. This interpretation agrees with the observed inter-clay spacings being dependent only on the DNA concentration.

Topics: Aluminum Silicates; Bentonite; Clay; Colloids; DNA; Liquid Crystals; Molecular Conformation; Nanostructures; Nucleic Acid Conformation; Soil

The external invertase isoform 1 (EINV1) was immobilised on eight differently modified beidellite nanoclays. Modifications were composed of organo-modification with different amounts of surfactant - hexadecyl trimethylammonium cation (HDTMA), pillaring with Al/Fe containing polyhydroxy cations and acid modification of Na-enriched and pillared clays. The modified nanoclays were characterised by XRD, N2-physisorption, SEM and FT-IR spectroscopy. The amount of bound enzyme activity was significantly influenced by the modification of beidellite ranging from 50 to remarkable 2200U/g. Biochemical characterization was performed for five modified nanoclays showing the highest enzyme activity after invertase immobilisation. The investigation demonstrated that after immobilisation the structure and the catalytic properties of invertase were preserved, while Km values were slightly increased from 26 to 37mM. immobilisation significantly improved thermal and storage stability of EINV1. Results indicate that beidellite nanoclays obtained by low cost modifications can be applied as a suitable support for the immobilisation of invertase. The immobilizate can be efficiently engaged in sucrose hydrolysis in batch reactor.

Topics: Aluminum Silicates; beta-Fructofuranosidase; Catalysis; Clay; Enzyme Stability; Enzymes, Immobilized; Hydrogen-Ion Concentration; Nanostructures; Saccharomyces cerevisiae; Spectroscopy, Fourier Transform Infrared; X-Ray Diffraction

Aqueous suspensions of swelling clay minerals exhibit a rich and complex rheological behaviour. In particular, these repulsive systems display strong shear-thinning at very low volume fractions in both the isotropic and gel states. In this paper, we investigate the evolution with shear of the orientational distribution of aqueous clay suspensions by synchrotron-based rheo-SAXS experiments using a Couette device. Measurements in radial and tangential configurations were carried out for two swelling clay minerals of similar morphology and size, Wyoming montmorillonite and Idaho beidellite. The shear evolution of the small angle x-ray scattering (SAXS) patterns displays significantly different features for these two minerals. The detailed analysis of the angular dependence of the SAXS patterns in both directions provides the average Euler angles of the statistical effective particle in the shear plane. We show that for both samples, the average orientation is fully controlled by the local shear stress around the particle. We then apply an effective approach to take into account multiple hydrodynamic interactions in the system. Using such an approach, it is possible to calculate the evolution of viscosity as a function of shear rate from the knowledge of the average orientation of the particles. The viscosity thus recalculated almost perfectly matches the measured values as long as collective effects are not too important in the system.

Topics: Aluminum Silicates; Bentonite; Clay; Computer Simulation; Hydrodynamics; Particle Size; Rheology; Scattering, Small Angle; Shear Strength; Suspensions; Viscosity; Water; X-Ray Diffraction

We investigated the sorption of three triazine herbicides (atrazine, simazine, and metribuzin) by saponite and beidellite clay minerals saturated with K+, Cs+, Na+, and Ca2+. Saponite clay sorbed a larger fraction of each pesticide from aqueous solution than did beidellite clay. The lower cation-exchange capacity in saponite compared to that in beidellite presumably results in a less crowded interlayer, with more siloxane surface being available for adsorption. Generally, Cs-saturated clays sorbed more triazines than did clays saturated by K+, Na+, or Ca2+. We attribute this to the smaller hydrated radius of Cs+, which again increases the siloxane surface that is available for sorption. Furthermore, the relatively weak hydration of Cs+ reduces the swelling of clay interlayers, thus making sorption domains less hydrated and more receptive to hydrophobic molecules. The Cs-saponite manifested a sorption of more than 1% atrazine by weight above equilibrium concentrations of 6 mg/L, which to our knowledge is the largest sorption of neutral atrazine from water yet reported for an inorganic sorbent. Molecular dynamics simulations indicate that atrazine interacts both with clay basal planes and with multiple cations in the clay interlayer.

Topics: Adsorption; Aluminum Silicates; Atrazine; Clay; Environmental Pollution; Herbicides; Simazine; Triazines; Water

Molecular dynamics simulations were performed to provide a systematic study of aqueous uranyl adsorption onto the external surface of 2:1 dioctahedral clays. Our understanding of this key process is critical in predicting the fate of radioactive contaminants in natural groundwaters. These simulations provide atomistic detail to help explain experimental trends in uranyl adsorption onto natural media containing smectite clays. Aqueous uranyl concentrations ranged from 0.027 to 0.162 M. Sodium ions and carbonate ions (0.027-0.243 M) were also present in the aqueous regions to more faithfully model a stream of uranyl-containing groundwater contacting a mineral system comprised of Na-smectite. No adsorption occurred near the pyrophyllite surface, and there was little difference in uranyl adsorption onto the beidellite and montmorillonite, despite the difference in location of clay layer charge between the two. At low uranyl concentration, the pentaaquouranyl complex dominates in solution and readily adsorbs to the clay basal plane. At higher uranyl (and carbonate) concentrations, the mono(carbonato) complex forms in solution, and uranyl adsorption decreases. Sodium adsorption onto beidellite occurred both as inner- and outer-sphere surface complexes, again with little effect on uranyl adsorption. Uranyl surface complexes consisted primarily of the pentaaquo cation (85%) and to a lesser extent the mono(carbonato) species (15%). Speciation diagrams of the aqueous region indicate that the mono(carbonato)uranyl complex is abundant at high ionic strength. Oligomeric uranyl complexes are observed at high ionic strength, particularly near the pyrophyllite and montmorillonite surfaces. Atomic density profiles of water oxygen and hydrogen atoms are nearly identical near the beidellite and montmorillonite surfaces. Water structure therefore appears to be governed by the presence of adsorbed ions and not by the location of layer charge associated with the substrate. The water oxygen density near the pyrophyllite surface is similar to the other cases, but the hydrogen density profile indicates reduced hydrogen bonding between adsorbed water molecules and the surface.

Topics: Adsorption; Aluminum Silicates; Bentonite; Clay; Computer Simulation; Hydrogen-Ion Concentration; Models, Chemical; Surface Properties; Thermodynamics; Uranium; Water