clay and hydroxide-ion

Clay-based bio-inorganic nanohybrids, such as layered double hydroxides (LDH), have been extensively researched in the various fields of biomedicine, particularly for drug delivery and bio-imaging applications. Recent trends indicate that such two-dimensional LDH can be hybridized with a variety of photo-active biomolecules to selectively achieve anti-cancer benefits through numerous photo/chemotherapies (PCT), including photothermal therapy, photodynamic therapy, and magnetic hyperthermia, a combination of therapies to achieve the best treatment regimen for patients that cannot be treated either by surgery or radiation alone. Among the novel two-dimensional clay-based bio-inorganic nanohybrids, LDH could enhance the photo-stability and drug release controllability of the PCT agents, which would, in turn, improve the overall phototherapeutic performance. This review article highlights the most recent advances in LDH-based two-dimensional clay-bio-inorganic nanohybrids for the aforementioned applications.

Topics: Clay; Drug Delivery Systems; Humans; Hydroxides; Photochemotherapy

RNA interference is triggered in plants by the exogenous application of double-stranded RNA or small interfering RNA (siRNA) to silence the expression of target genes. This approach can potentially provide insights into metabolic pathways and gene function and afford plant protection against viruses and other plant pathogens. However, the effective delivery of biomolecules such as siRNA into plant cells is difficult because of the unique barrier imposed by the plant cell wall. Here, we demonstrate that 40-nm layered double hydroxide (LDH) nanoparticles are rapidly taken up by intact Nicotiana benthamiana leaf cells and by chloroplasts, following their application via infiltration. We also describe the distribution of infiltrated LDH nanoparticles in leaves and demonstrate their translocation through the apoplast and vasculature system. Furthermore, we show that 40-nm LDH nanoparticles can greatly enhance the internalization of nucleic acids by N. benthamiana leaf cells to facilitate siRNA-mediated downregulation of targeted transgene mRNA by >70% within 1 day of exogenous application. Together, our results show that 40-nm LDH nanoparticle is an effective platform for delivery of siRNA into intact plant leaf cells.

Topics: Clay; Nanoparticles; Plant Leaves; RNA Interference; RNA, Double-Stranded; RNA, Small Interfering

The current study shows an advanced synesthetic technique of a nitrate-fertilizer with a controlled release behavior into different soils (normal and acidic agriculture soils solutions) at different climate temperatures. The environmentally friendly and the biocompatible layered double hydroxide (LDH) clay material was used as a host to accommodate the nitrate anion into its interlayer gallery by applying a reconstruction-incorporation technique (the memory effect property of LDH that allows calcined LDH to memorize its original structure). The prepared materials were characterized by different spectroscopic techniques including; X-ray powder spectroscopy, IR, SEM, TEM, and TGA analyses. A remarkable loading ratio of the nitrate anion fertilizer was recorded into the LDH structure. Around 90 wt% of the intercalated nitrate anion was released in a sustained controlled behavior over around 24 days, while the same amount of nitrate was released over 10 days in the acidic soil. Accordingly, the present study offers a new passway for the formulation of controlled release fertilizers by using the hosting anionic clay LDH materials.

Topics: Clay; Delayed-Action Preparations; Fertilizers; Hydroxides; Nitrates

Some seventy years ago, John Desmond Bernal proposed a role for clays in the origin of life. While much research has since been dedicated to the study of silicate clays, layered double hydroxides, believed to be common on the early Earth, have received only limited attention. Here we examine the role that layered hydroxides could have played in prebiotic peptide formation. We demonstrate how these minerals can concentrate, align and act as adsorption templates for amino acids, and during wetting-drying cycles, promote peptide bond formation. This enables us to propose a testable mechanism for the growth of peptides at layered double hydroxide interfaces in an early Earth environment. Our results provide insights into the potential role of mineral surfaces in mimicking aspects of biochemical reaction pathways.

Topics: Aluminum Silicates; Amino Acids; Clay; Earth, Planet; Hydroxides; Minerals; Origin of Life; Peptides; Surface Properties

A series of nanocomposite adsorbents were prepared by heterocoagulation of negatively charged delaminated montmorillonite (Mt) and positively charged synthetic layered double hydroxide (LDH) colloids with different LDH loading amounts. The mineralogy and physicochemical properties of the resulting nanocomposites were characterized. Their potential applications for phosphate (P) removal from aqueous solution, as a function of P concentration (2.5-200 mg/L), contact time (1 min-48 h) and pH (3-10), were evaluated by using batch adsorption modes. It was found that the adsorption data could be well described by both Freundlich and Langmuir isotherm models. The maximum adsorption capacity of three different LDH heterocoagulated montmorillonites (LDH-Mts) for P removal was found to increase with LDH loadings, reaching 12.6, 16.2 and 23.3 mg/g respectively; Adsorption kinetic data revealed that 90% of adsorption onto LDH-Mts was completed within 1 h (h) and the adsorption process could be well described by the pseudo-second-order model. These results demonstrated that heterocoagulation of Mt and LDH could preserve the adsorption capacity of LDH for P and enhance the stability of both clay minerals, and LDH-Mts could be effectively used as a potential promising filtration medium for P removal.

Topics: Adsorption; Aluminum Silicates; Bentonite; Clay; Colloids; Hydroxides; Kinetics; Microscopy, Electron, Scanning; Models, Theoretical; Nanocomposites; Phosphates; Surface Properties; Water Pollutants, Chemical; Water Purification; X-Ray Diffraction

Methotrexate (MTX), an anticancer agent, was successfully intercalated into the anionic clay, layered double hydroxides to form a new nanohybrid drug. The coprecipitation and subsequent hydrothermal method were used to prepare chemically, structurally, and morphologically well-defined two-dimensional drug-clay nanohybrid. The resulting two-dimensional drug-clay nanohybrid showed excellent colloidal stability not only in deionized water but also in an electrolyte solution of Dulbecco's Modified Eagle's Medium with 10% fetal bovine serum, in which the average particle size in colloid and the polydispersity index were determined to be around 100 and 0.250 nm, respectively. The targeting property of the nanohybrid drug was confirmed by evaluating the tumor-to-blood and tumor-to-liver ratios of the MTX with anionic clay carrier, and these ratios were compared to those of free MTX in the C33A orthotopic cervical cancer model. The biodistribution studies indicated that the mice treated with the former showed 3.5-fold higher tumor-to-liver ratio and fivefold higher tumor-to-blood ratio of MTX than those treated with the latter at 30 minutes postinjection.

Topics: Aluminum Silicates; Animals; Anions; Antimetabolites, Antineoplastic; Cattle; Cell Proliferation; Cell Survival; Clay; Drug Delivery Systems; Female; Humans; Hydroxides; Methotrexate; Mice; Nanoparticles; Tissue Distribution; Tumor Cells, Cultured; Uterine Cervical Neoplasms; Xenograft Model Antitumor Assays

Kaolin suspensions were coagulated with AlCl₃ and a high-basicity PACl at pH 7, at dosages that gave zeta potentials close to zero. The actions of the two coagulants were completely different. With AlCl₃, the formation of an amorphous hydroxide precipitate played a dominant role. When the coagulant was added to the suspension, flocs grew rapidly and incorporated most of the kaolin particles within the hydroxide precipitate. When the suspension was added some time after the coagulant, the clay particles were found to be mainly on the outer floc surfaces, although the floc size was about the same. The light scattering properties of the flocs were very dependent on the number and location of particles in the precipitate. With PACl, delaying the addition of kaolin had no influence on the final floc properties. In further tests, different suspensions over a range of concentrations were coagulated with alum at pH 7. Monitoring by a 'turbidity fluctuation' technique showed an apparent increase in floc size with increasing particle concentration. However, floc sizes determined from microscope images were very nearly constant, independent of particle nature and concentration. With different particle types, the monitoring results were greatly dependent on the light scattering properties of the particles. Particles incorporated within hydroxide flocs appeared to have no influence on floc properties, such as size and strength.

Topics: Aluminum Chloride; Aluminum Compounds; Aluminum Hydroxide; Aluminum Silicates; Chlorides; Clay; Flocculation; Hydroxides; Waste Disposal, Fluid

Despite the importance of Fe redox cycling in clay minerals, the mechanism and location of electron transfer remain unclear. More specifically, there is some controversy whether electron transfer can occur through both basal and edge surfaces. Here we used Mössbauer spectroscopy combined with selective chemical extractions to study electron transfer from Fe(II) sorbed to basal planes and edge OH-groups of clay mineral NAu-1. Fe(II) sorbed predominantly to basal planes at pH values below 6.0 and to edge OH-groups at pH value 7.5. Significant electron transfer occurred from edge OH-group bound Fe(II) at pH 7.5, whereas electron transfer from basal plane-sorbed Fe(II) to structural Fe(III) in clay mineral NAu-1 at pH 4.0 and 6.0 occurred but to a much lower extent than from edge-bound Fe(II). Mössbauer hyperfine parameters for Fe(II)-reacted NAu-1 at pH 7.5 were consistent with structural Fe(II), whereas values found at pH 4.0 and 6.0 were indicative of binding environments similar to basal plane-sorbed Fe(II). Reference experiments with Fe-free synthetic montmorillonite SYn-1 provided supporting evidence for the assignment of the hyperfine parameters to Fe(II) bound to basal planes and edge OH-groups. Our findings demonstrate that electron transfer to structural Fe in clay minerals can occur from Fe(II) sorbed to both basal planes and edge OH-groups. These findings require us to reassess the mechanisms of abiotic and microbial Fe reduction in clay minerals as well as the importance of Fe-bearing clay minerals as a renewable source of redox equivalents in subsurface environments.

Topics: Adsorption; Aluminum Silicates; Bentonite; Clay; Hydrogen-Ion Concentration; Hydroxides; Iron; Spectroscopy, Mossbauer

Na(+)-montmorillonite clay (generally referred to as MMT) is very useful for reinforcing polymeric matrix at very low concentrations (typically, 2-5% wt). These clay particles are typically exfoliated before they can demonstrate the significant gains in heat deflection temperature, modulus, and elongation properties. In the case of hydrophilic biopolymer based matrices, such as carbohydrates and chitosan, exfoliating these nanoclay particles needs greater attention because the exfoliation is typically carried out using hydrophobic oligomers through ion-exchange. This study reports a new method of synthesizing completely hydrophilic MMT-assemblages using hydrophilic plasticizers for biopolymers. We used sugar alcohols (glycerol, xylitol with 3 and 5 hydroxyl groups) and polysaccharide maltodextrin to exfoliate the MMT. Sonication was conducted for MMT nanoclay and plasticizers at different weight ratios. It was confirmed that all plasticizer/modifier led to expansion of MMT gallery spacing (d-spacing) and the change in d-spacing could be related to the molecular structure of the plasticizer. Meanwhile, the extent of exfoliation was maximum with maltodextrin (fully exfoliation with 1:10 and 1:20 ratio of MMT:plasticizer) across all test samples and interestingly, glycerol and xylitol samples quickly established within the MMT galleries and exhibited minimal influence with further increase in relative concentrations.

Topics: Aluminum Silicates; Bentonite; Chemistry Techniques, Synthetic; Clay; Hydroxides; Nanoparticles; Plasticizers; Sodium; Sugar Alcohols; Ultrasonics

Methods for monitoring particle aggregation are briefly reviewed. Most of the techniques are based on some form of light scattering and may be greatly dependent on the optical properties of aggregates, which are not generally known. As fractal aggregates grow larger their density can become very low and this has important practical consequences for light scattering. For instance, the scattering coefficient may be much less than for solid objects, which means that the aggregates can appear much smaller than their actual size by a light transmission method. Also, for low-density objects, a high proportion of the scattered light energy is within a small angle of the incident beam, which may also be relevant for measurements with aggregates. Using the "turbidity fluctuation" technique as an example, it is shown how the apparent size of hydroxide flocs depends mainly on the included impurity particles, rather than the hydroxide precipitate itself. Results using clay suspensions with hydrolyzing coagulants and polymeric flocculants under different string conditions are discussed.

Topics: Alum Compounds; Aluminum Silicates; Clay; Ferric Compounds; Flocculation; Fractals; Hydroxides; Kaolin; Light; Nephelometry and Turbidimetry; Particle Size; Scattering, Radiation; Water

A comparison is made between the Raman and infrared spectra of ferruginous smectite and a nontronite using both absorption and emission techniques. Raman spectra show hydroxyl stretching bands at 3572, 3434, 3362, 3220 and 3102 cm(-1). The infrared emission spectra of the hydroxyl stretching region are significantly different to the absorption spectrum. These differences are attributed to the loss of water, absent in the emission spectrum, the reduction of the samples in the spectrometer and possible phase changes. Dehydroxylation of the two minerals may be followed by the loss of intensity of the hydroxyl stretching and hydroxyl deformation frequencies. Hydroxyl deformation modes are observed at 873 and 801 cm(-1) for the ferruginous smectite, and at 776 and 792 cm(-1) for the nontronite. Raman hydroxyl deformation vibrations are found at 879 cm(-1). Other Raman bands are observed at 1092 and 1032 cm(-1), assigned to the SiO stretching vibrations, at 675 and 587 cm(-1), assigned to the hydroxyl translation vibrations, at 487 and 450 cm(-1), attributed to OSiO bending type vibrations, and at 363, 287 and 239 cm(-1). The differences in the molecular structure of the two minerals are attributed to the Al/Fe ratio in the minerals.

Topics: Aluminum Silicates; Clay; Gastrointestinal Agents; Hydroxides; Iron Compounds; Silicates; Spectrophotometry, Infrared; Spectroscopy, Fourier Transform Infrared; Spectrum Analysis, Raman; Temperature; Water