clay and hectorite

In the last years, the use of clay minerals for pharmaceutical purposes has increased due to their interesting properties. Hectorite (Ht) is a clay belonging to the smectite group which has attracted attention for applications in biology, tissue engineering and as drug carrier and delivery system. However, the mechanisms involved in Ht cellular uptake and transport into cells, are still unclear. Herein, we used a labeled Ht (Ht/1Cl) to study both the cellular uptake, by confocal laser scanning microscopy, and internalization pathways involved in the cellular uptake, by various endocytosis-inhibiting studies and fluorescence microscopy. These studies highlighted that Ht can penetrate the cellular membrane, localizing mainly in the cytoplasm. The main intracellular transport mechanisms are the ATP-dependent ones and those where filaments and microtubules are involved. Finally, as proof of concept for the potential of Ht as carrier system, we envisaged the covalent grafting of the anticancer molecule methotrexate (MTX), chosen as model, to obtain the Ht-MTX nanomaterial. The covalent linkage was confirmed by several techniques and the morphology of the obtained nanomaterial was imaged by SEM and TEM investigations. The kinetic release of the drug from the Ht-MTX nanomaterial in physiological conditions was studied as well. Furthermore, cytotoxic studies on different cell lines, namely, HL-60, HL-60R, MCF-7, 5637, UMUC3 and RT112 showed that Ht could be a promising material for anticancer therapy.

Topics: Clay; Drug Carriers; Methotrexate; Silicates

Sodium alginate (SA) is a linear biopolymer, which is the nontoxic, biodegradable, and rich in carboxyl and hydroxyl groups. In the paper, the SA-based hydrogel bead was prepared by the cationic hectorite clay and anionic sodium alginate with a simple ionic gelation method under freeze-drying, and the adsorption properties were evaluated by the removal of copper ions from aqueous solutions. The composites were characterized by X-ray diffraction (XRD), nitrogen adsorption-desorption isotherm (BET), thermal analysis (TG), and Fourier transform infrared spectroscopy (FT-IR). The pseudo-first-order and pseudo-second-order kinetic models were used to describe the kinetic data and the Langmuir, Freundlich, Dubinin-Radushkevich (D-R), and Temkin models were applied to describe the adsorption isotherms. The results showed that the adsorption process was found to follow the Freundlich isotherm model and the maximum sorption capacity was observed to be 160.28 mg/g under the initial concentration from 10 to 700 mg/L at 45 °C. Adsorption kinetics data fitted well with pseudo-second-order rate model. The porous structure of the composite was responsible for the adsorption of Cu

Topics: Adsorption; Alginates; Clay; Copper; Hydrogels; Hydrogen-Ion Concentration; Kinetics; Models, Chemical; Porosity; Silicates; Spectroscopy, Fourier Transform Infrared; Thermogravimetry; Water; Water Pollutants, Chemical; X-Ray Diffraction

Currently, there are few strategies for controlling pathogenic bacteria, especially the pathotypes of Escherichia coli which are an emerging threat to public health worldwide. Here, multivalent vaccine formulations are reported for control of pathogenic E. coli. The formulations utilised clay nanoparticles, either layered double hydroxides (LDH) or hectorite (HEC), to complex with a cocktail of three recombinant antigens, intimin β (IB), proprietary antigen 1 (PAg1) and proprietary antigen 2 (PAg2). Acting as nano-adjuvants, LDH and HEC were able to stimulate strong, durable and balanced immune responses in mice. Moreover, LDH-IB-PAg1-PAg2 and HEC-IB-PAg1-PAg2 immunised mice developed potent mucosal immune responses and efficiently prevented adherence of enterohemorrhagic E. coli serotype O26 to mammalian cells. Notably, the multi-faceted immune responses elicited by the clay nanoparticle formulations were significantly higher than those induced by a QuilA formulation, without antigenic competition observed for the first time. The results of this study suggest that LDH and HEC offer considerable promise as effective multivalent vaccine carriers against important pathogens such as enteropathogenic E. coli.

Topics: Adhesins, Bacterial; Adsorption; Animals; Antibodies, Bacterial; Antigens, Bacterial; Clay; Escherichia coli; Escherichia coli Infections; Escherichia coli Proteins; Escherichia coli Vaccines; Female; Hydroxides; Immunoglobulin G; Mice, Inbred C57BL; Nanoparticles; Silicates

A standard procedure does not exist to distinguish between attached and unattached micro-organisms. In this study, we compared two methods to quantify between Escherichia coli attached to clay particles and E. coli freely suspended in solution: flow cytometry (attachment assay and viability assay) and settling (or centrifugation followed by settling).. Methods were tested using three environmental strains collected from swine facilities (A, B and C) and one purchased modified pathogenic strain (ATCC 43888); four clay particles: Hectorite, Kaolinite, Ca-Montmorillonite, Montmorillonite K-10; and a range of surface area ratios (particle surface area to E. coli surface area). When comparing the two methods, the per cent attached obtained from the flow cytometry was lower, but not significantly different from the per cent attached obtained from the settling method for all conditions except when the particle was Hectorite or Montmorillonite K-10; when the strain was C; and when the surface area ratio was below 100. Differences between the methods are likely because traditional culture-based methods cannot detect the viable but nonculturable (VBNC) population, whereas flow cytometry can detect the fraction of VBNC with intact membranes.. Our results indicate that flow cytometry is a rapid and culture-independent method for differentiating between attached and unattached micro-organisms.. Flow cytometry is useful for laboratory-based studies of micro-organism-particle interactions.

Topics: Aluminum Silicates; Bentonite; Clay; Escherichia coli; Flow Cytometry; Kaolin; Silicates

Self-healing hydrogels were proposed to be used as biomaterials, because of the capability of spontaneously healing injury, but most of the reported self-healing hydrogels do not possess high mechanical strength and fast self-healing at the same time. Herein, we prepared graphene oxide (GO)-hectorite clay-poly(N,N-dimethylacrylamide) (PDMAA) hybrid hydrogels with enhanced mechanical properties and fast self-healing capability realized by near-infrared (NIR) irradiation. The physical cross-linking between clay sheets and PDMAA chains provided the hydrogel with mechanical strength to maintain its stability in shape and architecture. GO sheets in the hybrid hydrogels acted as not only a collaborative cross-linking agent but also as a NIR absorber to absorb the NIR irradiation energy and transform it to thermal energy rapidly and efficiently, resulting in a rapid temperature increase of the GO containing gels. The chain mutual diffusion and the reformation of physical cross-linking occurred more quickly at higher temperature; consequently, the damaged hydrogel was almost completely recovered in a few minutes upon irradiation. We also demonstrated a potential application of the hybrid hydrogel as a self-healing surgical dressing.

Topics: Acrylamides; Aluminum Silicates; Bandages; Clay; Graphite; Hardness; Hydrogels; Infrared Rays; Materials Testing; Nanoparticles; Oxides; Particle Size; Silicates; Tensile Strength

We show experimentally that gaseous CO(2) intercalates into the interlayer space of the synthetic smectite clay Na-fluorohectorite at conditions not too far from ambient. The mean interlayer repetition distance of the clay when CO(2) is intercalated is found to be 12.5 Å for the conditions -20 °C and 15 bar. The magnitude of the expansion of the interlayer upon intercalation is indistinguishable from that observed in the dehydrated-monohydrated transition for H(2)O, but the possibility of water intercalation is ruled out by a careful analysis of the experimental conditions and repeating the measurements exposing the clay to nitrogen gas. The dynamics of the process is observed to be dependent on the pressure, with a higher intercalation rate at increased pressure. The rate of CO(2) intercalation at the studied conditions is found to be several orders of magnitude slower than the intercalation rate of water or humidity at ambient pressure and temperature.

Topics: Adsorption; Aluminum Silicates; Carbon Dioxide; Clay; Humidity; Intercalating Agents; Nitrogen; Pressure; Silicates; Sodium; Temperature; X-Ray Diffraction

A polymer-layered silicate nanocomposite coating is prepared by combining a novel synthetic lithium-hectorite and an UV-curable, cationic polyurethane. Oxygen transmission measurements clearly indicate the supremacy of the lithium-hectorite as compared to a standard montmorillonite. In addition, a very high degree of optical transparency of the nanocomposite coating is achieved, rendering this material highly interesting for flexible packaging and encapsulation applications.

Topics: Aluminum Silicates; Clay; Lithium; Nanocomposites; Nanotechnology; Oxygen; Photochemical Processes; Polymers; Silicates; Ultraviolet Rays

Within the wider context of water behavior in soils, and with a particular emphasis on clays surrounding underground radioactive waste packages, we present here the translational dynamics of water in clays in low hydrated states as studied by coupling molecular dynamics (MD) simulations and quasielastic neutron scattering experiments by neutron spin echo (NSE). A natural montmorillonite clay of interest is modeled by a synthetic clay which allows us to understand the determining parameters from MD simulations by comparison with the experimental values. We focus on temperatures between 300 and 350 K, i.e., the range relevant to the highlighted application. The activation energy Ea experimentally determined is 6.6 kJ/mol higher than that for bulk water. Simulations are in good agreement with experiments for the relevant set of conditions, and they give more insight into the origin of the observed dynamics.

Topics: Aluminum Silicates; Clay; Hydrodynamics; Mass Spectrometry; Models, Molecular; Neutrons; Radiation Protection; Silicates; Soil; Temperature

Topics: Aluminum Silicates; Clay; Fluorine; Microscopy, Electron, Scanning; Osmosis; Silicates

A hectorite (H) clay sample has been modified with 2-mercaptobenzimidazole (MBI) using homogeneous and heterogeneous routes. Both modification methodologies resulted in similar products, named H(HOM) and H(HET), respectively. These materials were characterized by CO(2) gas adsorption, elemental analysis, nuclear magnetic nuclei of carbon-13 and silicon-29. The effect of two variables (contact time and metal concentration) has been studied using batch technique at room temperature and pH 2.0. After achieving the best conditions for Cr(VI) adsorption, isotherms of this adsorbate on using the chosen adsorbents were obtained, which were fitted to non-linear Sips isotherm model. The maximum number of moles adsorbed was determined to be 11.63, 12.85 and 14.01 mmol g(-1) for H, H(HOM) and H(HET), respectively, reflecting the maximum adsorption order of H(HET)>H(HOM)>H. The energetic effects (Delta(int)H degrees , Delta(int)G degrees and Delta(int)S degrees ) caused by chromium ion adsorption were determined through calorimetric titrations.

Topics: Adsorption; Aluminum Silicates; Benzimidazoles; Calorimetry; Chromium; Clay; Hydrogen-Ion Concentration; Magnetic Resonance Spectroscopy; Models, Chemical; Models, Statistical; Silicates; Solutions; Thermodynamics; Water Pollutants, Chemical; Water Purification

Electron paramagnetic resonance spectroscopy is used to monitor the bioavailability of a nitroxide spin probe, 4-hydroxy-Tempo or Tempol, in Ca-hectorite suspensions and pastes, to bacteria capable of degrading this probe co-metabolically. In nutrient solutions with an initial probe concentration of 1.2 mM and in the absence of hectorite, bacteria are able to denature Tempol and eliminate its paramagnetic signal within 48 h. In the presence of hectorite and after flocculation, the effect of bacteria is significantly delayed, but almost complete denaturation still occurs, after roughly 120 h. When hectorite is added but the bacterial/clay suspension is not centrifuged, Tempol denaturation levels off after about 24 h and reaches a plateau with approximately 45% of Tempol remaining. This plateau does not constitute evidence of limited bioavailability, as is widely assumed, since subsequent addition of nutrients causes the denaturation reaction to proceed to a second plateau, with merely 10% of Tempol remaining.

Topics: Aluminum Silicates; Bacteria; Biodegradation, Environmental; Biological Availability; Clay; Cyclic N-Oxides; Electron Spin Resonance Spectroscopy; Environmental Monitoring; Silicates; Soil Pollutants; Spin Labels; Xenobiotics

Properties of interfacial water have been studied in saponite, hectorite and montmorillonite suspensions. These data, together with our previous results are explained by the presence of two water interfacial sites or by a fast exchange between them.

Topics: Aluminum Silicates; Bentonite; Clay; Deuterium; Magnetic Resonance Spectroscopy; Oxygen Isotopes; Silicates; Suspensions