Exfoliation of montmorillonite in protein solutions

Correlation of montmorillonite exfoliation with interlayer cations in the preparation of two-dimensional nanosheets

Varying exfoliation properties of Na– and Ca–MMTs were first investigated through AFM and molecular dynamics simulation.

Mitigation of colitis with NovaSil clay therapy

BACKGROUND/AIMS

Five million people currently live with Crohn's disease (CD) or ulcerative colitis, the two major forms of inflammatory bowel disease. Available treatments frequently result in side effects that compromise the immune health of the patient. Consequently, alternative therapies that cause fewer systemic effects are needed. Dioctahedral smectite clays have been utilized to treat medical conditions, including diarrheal and enteric disease. Herein, we report the ability of a refined dioctahedral smectite (NovaSil, NS) to sorb inflammatory proteins and reduce inflammation in a TNBS (2,4,6-trinitrobenzenesulfonic acid) mouse model of CD. We also investigated whether NS could rescue gut microbial diversity in TNBS-induced mice.

METHODS

ELISA, X-ray diffraction, and transmission electron microscopy were employed to characterize the NS-cytokine interaction in vitro. A TNBS mouse colitis model was utilized to study the efficacy of NS supplementation for 4 weeks. The three treatment groups included control, TNBS, and TNBS + NS. DNA was extracted from feces and sorted for bacterial phylogenetic analysis.

RESULTS

Results suggest that NS binds TNFα in vitro. In TNBS-treated mice, supplementation with NS significantly reduced weight loss, and serum proinflammatory cytokine levels (IL-2, IL-6, and IL-12, TNFα, IFNγ) compared with the TNBS group. TNBS-treated mice demonstrated a significant reduction in gut microbiota species richness when compared with the TNBS + NS group and control group.

CONCLUSIONS

NovaSil mitigated the effects of TNBS-induced colitis based on reduction in systemic markers of inflammation, significant improvement in weight gain, and intestinal microbial profile.

Adsorption, aggregation, and desorption of proteins on smectite particles

We report on adsorption of lysozyme (LYS), ovalbumin (OVA), or ovotransferrin (OVT) on particles of a synthetic smectite (synthetic layered aluminosilicate). In our approach we used atomic force microscopy (AFM) and quartz crystal microbalance (QCM) to study the protein-smectite systems in water solutions at pH ranging from 4 to 9. The AFM provided insights into the adhesion forces of protein molecules to the smectite particles, while the QCM measurements yielded information about the amounts of the adsorbed proteins, changes in their structure, and conditions of desorption. The binding of the proteins to the smectite surface was driven mainly by electrostatic interactions, and hence properties of the adsorbed layers were controlled by pH. At high pH values a change in orientation of the adsorbed LYS molecules and a collapse or desorption of OVA layer were observed. Lowering pH to the value ≤ 4 caused LYS to desorb and swelling the adsorbed OVA. The stability of OVT-smectite complexes was found the lowest. OVT revealed a tendency to desorb from the smectite surface at all investigated pH. The minimum desorption rate was observed at pH close to the isoelectric point of the protein, which suggests that nonspecific interactions between OVT and smectite particles significantly contribute to the stability of these complexes.

Structural studies of adsorbed protein (betalactoglobulin) on natural clay (montmorillonite)

Adsorption of betalactoglobulin on montmorillonite leads to structural changes of the protein accompanied by a partial exfoliation of clay.

Understanding the relationship of performance with nanofiller content in the biomimetic layered nanocomposites

Montmorillonite/poly(vinyl alcohol) (MMT/PVA) nanocomposites spanning the complete range of MMT content (0-100 wt%) are prepared by simple evaporation-induced assembly. Effects of MMT content on the structure and mechanical properties of nanocomposites are systematically investigated and exhibit two important transitions at MMT contents of 30 wt% and 70 wt%. In the range of 0-30 wt%, the nanocomposites show a random structure. With the content of PVA increasing, the mechanical properties of the resultant nanocomposites were dramatically enhanced and were higher than that by prediction according to the conventional composite model. In the range of 30-70 wt%, the nanocomposites show a nacre-like layered structure with alternating MMT platelets and PVA layers, and all PVA is completely restricted by MMT platelets. The mechanical properties of nanocomposites were further improved by increasing the content of MMT, and reached the maximum value at the MMT content of 70 wt%. The 70 wt% MMT/PVA nanocomposite has a tensile strength of 219 ± 19 MPa, which is 5.5 times higher than that of a pure PVA film and surpasses nacre and reported biomimetic layered clay/PVA composites. When the MMT content is higher than 70 wt%, the layered structure is transformed to tactoids, which deteriorate mechanical properties. These results offer comprehensive understanding for developing high-performance biomimetic layered nanocomposite materials with high nanofiller loading.

Swelling and gel/sol formation of perchlorate-type layered double hydroxides in concentrated aqueous solutions of amino acid-related zwitterionic compounds

ClO(4)(-)MgAl-LDH3, a MgAl (Mg/Al = 3) layered double hydroxide (LDH) containing perchlorate, swells and forms colloidal suspensions (sols) via the gel state in concentrated aqueous solutions of zwitterionic compounds related to amino acids. In total, 36 zwitterionic compounds with different molecular structures and additional functional groups were examined at various concentrations, and the sol-formation ability was judged by the transmittance (at λ = 589 nm) of the resulting suspensions. At low concentration, the obtained suspensions were turbid, with transmittances of ~0%. However, above the threshold concentration (0.3-1.0 M), osmotic swelling occurred and the transmittances of the suspensions increased sharply with increases in concentration to reach maximum values of 70-95%. The threshold concentration and maximum transmittance value depended on the structure and the location of the functional groups. The enhancement of the permittivity of water by the zwitterions and the formation of H-bond networks were assumed to be the reasons for the swelling phenomenon. Similar gel/sol formation was observed for ClO(4)(-)LDHs with Mg/Al = 2, Ni/Al = 2, 3, and Co/Al = 2 and some NO(3)(-)LDHs. Large ClO(4)(-)LDH films could be prepared by filtration of the colloidal suspensions followed by washing and drying processes.