Application of Edible Montmorillonite Clays for the Adsorption and Detoxification of Microcystin

Mitigation of PFAS toxicity through sorbent treatment in Sprague-Dawley rats during prenatal and postnatal exposure

PFAS (per- and polyfluoroalkyl substances) are prevalent and persistent environmental pollutants with significant toxicity, especially during critical windows of exposure such as pregnancy and lactation. This study investigated the prenatal and postnatal effects of PFAS exposure on the serum and liver of Sprague-Dawley rats, and the mitigating efficacy of orally administered sorbents. Animal groups included vehicle control, PFAS (0.95 mg/kg-bw/day), and PFAS co-treated with calcium montmorillonite (CM), CM-carnitine, CM-choline, activated carbon (AC), or acid processed montmorillonite (APM). Oral administration of PFAS resulted in accumulation in serum and liver by postnatal day (PND) 21, especially for PFOS. PFAS exposure also reduced body weight gain by 24 % in females and 35 % in males via reduced food and water conversion rates, impaired liver histopathological structure, caused hepatocellular hypertrophy, disrupted serum biochemistry, and reduced vitamins A and B2 in both sexes. Additionally, PFAS exposure increased oxidative stress and liver damage as evidenced by reduced antioxidants (GSH, SOD, GST), induced ALT, AST and pro-inflammatory cytokines (TGF-β and TNF-α), and suppressed CRP. Importantly, CM-carnitine and CM-choline were the most effective mitigating sorbents, significantly reducing PFAS bioavailability in the liver and serum and restoring biochemical parameters such as cholesterol, total protein, and glucose in serum. All sorbent treatments alleviated oxidative stress, normalized inflammatory markers, and improved nutrient levels in both serum and liver. Furthermore, the study revealed sex-specific responses, with females showing greater susceptibility to PFAS-induced metabolic changes and a more prominent response to sorbent mitigation. This study highlights the toxic effect of PFAS exposure in serum and liver during vulnerable windows of exposure such as pregnancy and lactation, and establishes the proof of concept for the oral administration of sorbents, particularly CM-carnitine, CM-choline, and a mixture of sorbents, as preventive mitigation strategies.

NutriClayZn Binds Aflatoxin B1 and Suppresses Enterotoxigenic Salmonella and Escherichia coli

Salmonella Typhimurium and Escherichia coli represent foodborne pathogens that can trigger diarrhea and diminish weight gains in livestock, as well as cause gastroenteritis in humans. Although prophylactic antibiotics have been used historically on the farm to limit bacterial pathogens and promote animal growth, this practice may also foster antimicrobial resistant (AMR) strains of bacteria and deplete our arsenal of effective antibiotic therapies. Incorporation of free chemical zinc oxide (ZnO) into animal feed, at doses far above nutritional requirements, has largely replaced prophylactic antibiotics; however, environmental concerns are mounting around unabsorbed zinc (excreted in feces) impacting soil microbes and thereby contributing to the AMR threat. Here, NutriClayZn is introduced as an analog of montmorillonite (MMT) clay with potent efficacy against foodborne bacterial pathogens and slow release of low concentrations of zinc. Bacterial propagation was assessed in culture experiments using NutriClayZn dosages aligned with current dietary MMT clay practices for the control of aflatoxin in production animals. Zinc release was quantified by inductively coupled plasma mass spectrometry. Significant (p < 0.05) growth reduction of Salmonella Typhimurium was observed following NutriClayZn exposures releasing less zinc than that contained within free chemical ZnO positive controls. Moreover, NutriClayZn displayed dose-dependent efficacy against an AMR strain of Escherichia coli O157:H7, while also binding aflatoxin B1 with kinetics similar to its parent MMT clay. These findings suggest that NutriClayZn could serve as a dual-purpose dietary substance, binding aflatoxin B1 and suppressing enterotoxigenic bacteria that can compromise the food supply.

Chlorophyll-Amended Organoclays for the Detoxification of Ochratoxin A

Climate change has been associated with outbreaks of mycotoxicosis following periods of drought, enhanced fungal growth, and increased exposure to mycotoxins. For detoxification, the inclusion of clay-based materials in food and drinking water has resulted in a very promising strategy to reduce mycotoxin exposure. In this strategy, mycotoxins are tightly sorbed to high-affinity clay particles in the gastrointestinal tract, thus decreasing bioavailability, uptake to blood, and potential toxicity. This study investigated the ability of chlorophyll and chlorophyllin-amended montmorillonite clays to decrease the toxicity of ochratoxin A (OTA). The sorption mechanisms of OTA binding to surfaces of sorbents, as well as binding parameters such as capacity, affinity, enthalpy, and free energy, were examined. Chlorophyll-amended organoclay (CMCH) demonstrated the highest binding (72%) and was better than the chlorophyllin-amended hydrophilic clay (59%), possibly due to the hydrophobicity of OTA (LogP 4.7). In silico studies using molecular dynamics simulations showed that CMCH improves OTA binding in comparison to parent clay in line with experiments. Simulations depicted that chlorophyll amendments on clay facilitated OTA molecules binding both directly, through enhancing OTA binding on the clay, or predominantly indirectly, through OTA molecules interacting with bound chlorophyll amendments. Simulations uncovered the key role of calcium ions in OTA binding, particularly in neutral conditions, and demonstrated that CMCH binding to OTA is enhanced under both neutral and acidic conditions. Furthermore, the protection of various sorbents against OTA-induced toxicity was carried out using two living organisms (Hydra vulgaris and Caenorhabditis elegans) which are susceptible to OTA toxicity. This study showed the significant detoxification of OTA (33% to 100%) by inclusion of sorbents. Organoclay (CMCH) at 0.5% offered complete protection. These findings suggest that the chlorophyll-amended organoclays described in this study could be included in food and feed as OTA binders and as potential filter materials for water and beverages to protect against OTA contaminants during outbreaks and emergencies.

β-Lactoglobulin Enhances Clay and Activated Carbon Binding and Protection Properties for Cadmium and Lead

The removal of heavy metals from wastewater remains a challenge due to the limitations of current remediation methods. This study aims to develop multicomponent composites as inexpensive and environmentally friendly sorbents with enhanced capture of cadmium (Cd) and lead (Pb). The composites are based on calcium montmorillonite (CM) and activated carbon (AC) because of their proven effectiveness as sorbents for diverse toxins in environmental settings. In this study, we used a combination of computational and experimental methods to delineate that β-lactoglobulin enhances CM and AC binding and protection properties for Cd and Pb. Modeling and molecular dynamics simulations investigated the formation of material systems formed by CM and AC in complex with β-lactoglobulin and predicted their capacity to bind heavy metal ions at neutral pH conditions. Our simulations suggest that the enhanced binding properties of the material systems are attributed to the presence of several binding pockets formed by β-lactoglobulin for the two heavy metal ions. At neutral pH conditions, divalent Cd and Pb shared comparable binding propensities in all material systems, with the former being consistently higher than the latter. To validate the interactions depicted in simulations, two ecotoxicological models (L. minor and H. vulgaris) were exposed to Cd, Pb, and a mixture of the two. The inclusion of CM-lactoglobulin (β-lactoglobulin amended CM) and AC-lactoglobulin (β-lactoglobulin amended AC) at 0.05-0.2% efficiently and dose-dependently reduced the severe toxicity of metals and increased the growth parameters. This high efficacy of protection shown in the ecotoxicological models may result from the numerous possible interaction pockets of the β-lactoglobulin-amended materials depicted in simulations. The ecotoxicological models support the agreement with computations. This study serves as a proof of concept on how computations in tandem with experiments can be used in the design of multicomponent clay- and carbon-based sorbent amended systems with augmented functionalities for particular toxins.

Adsorption and removal of polystyrene nanoplastics from water by green-engineered clays

Human exposure to micro- and nanoplastics (MNPs) commonly occurs through the consumption of contaminated drinking water. Among these, polystyrene (PS) is well-characterized and is one of the most abundant MNPs, accounting for 10 % of total plastics. Previous studies have focused on carbonaceous materials to remove MNPs by filtration, but most of the work has involved microplastics since nanoplastics (NPs) are smaller in size and more difficult to measure and remove. To address this need, green-engineered chlorophyll-amended sodium and calcium montmorillonites (SMCH and CMCH) were tested for their ability to bind and detoxify parent and fluorescently labeled PSNP using in vitro, in silico, and in vivo assays. In vitro dosimetry, isothermal analyses, thermodynamics, and adsorption/desorption kinetic models demonstrated 1) high binding capacities (173-190 g/kg), 2) high affinities (103), and 3) chemisorption as suggested by low desorption (≤42 %) and high Gibbs free energy and enthalpy (>|-20| kJ/mol) in the Langmuir and pseudo-second-order models. Computational dynamics simulations for 30 and 40 monomeric units of PSNP depicted that chlorophyll amendments increased the binding percentage and contributed to the sustained binding. Also, 64 % of PSNP bind to both the head and tail of chlorophyll aggregates, rather than the head or tail only. Fluorescent PSNP at 100 nm and 30 nm that were exposed to Hydra vulgaris showed concentration-dependent toxicity at 20-100 µg/mL. Importantly, the inclusion of 0.05-0.3 % CMCH and SMCH significantly (p ≤ 0.01) and dose-dependently reduced PSNP toxicity in morphological changes and feeding rate. The bioassay validated the in vitro and in silico predictions about adsorption efficacy and mechanisms and suggested that CMCH and SMCH are efficacious binders for PSNP in water.

Kinetics of glyphosate and aminomethylphosphonic acid sorption onto montmorillonite clays in soil and their translocation to genetically modified corn

The co-occurrence of glyphosate (GLP) and aminomethylphosphonic acid (AMPA) in contaminated water, soil, sediment and plants is a cause for concern due to potential threats to the ecosystem and human health. A major route of exposure is through contact with contaminated soil and consumption of crops containing GLP and AMPA residues. However, clay-based sorption strategies for mixtures of GLP and AMPA in soil, plants and garden produce have been very limited. In this study, in vitro soil and in vivo genetically modified corn models were used to establish the proof of concept that the inclusion of clay sorbents in contaminated soils will reduce the bioavailability of GLP and AMPA in soils and their adverse effects on plant growth. Effects of chemical concentration (1-10 mg/kg), sorbent dose (0.5%-3% in soil and 0.5%-1% in plants) and duration (up to 28 days) on sorption kinetics were studied. The time course results showed a continuous GLP degradation to AMPA. The inclusion of calcium montmorillonite (CM) and acid processed montmorillonite (APM) clays at all doses significantly and consistently reduced the bioavailability of both chemicals from soils to plant roots and leaves in a dose- and time-dependent manner without detectable dissociation. Plants treated with 0.5% and 1% APM inclusion showed the highest growth rate (p ≤ 0.05) and lowest chemical bioavailability with up to 76% reduction in roots and 57% reduction in leaves. Results indicated that montmorillonite clays could be added as soil supplements to reduce hazardous mixtures of GLP and AMPA in soils and plants.

Lecithin-amended montmorillonite clays enhance the antibacterial effect of barrier creams

The objective of this study was to assess in vitro antibacterial activity of barrier cream (EVB) formulations containing either calcium montmorillonite (CM) or lecithin-amended montmorillonite (CML). All ingredients were generally recognized as safe (GRAS), and clay minerals were specifically studied due to their known ability to adsorb numerous toxins of human clinical relevance. Characterization of the EVB formulations showed good spreadability, pH, appearance, unity, viscosity, and no evidence of phase separation. Colony forming, disk diffusion susceptibility, and agar dilution assays were used to determine the minimal bactericidal concentration (MBC) of total EVB formulations, as well as respective individual ingredients, against E. coli. Active ingredients within the base EVB formulation were found to be essential oils and zinc oxide. EVB-CML at 0.5-25 mg/mL dose-dependently and significantly (p ≤ 0.01) enhanced the antibacterial activity of the base EVB formulation. MBC values for EVB-CML were 2.5 mg/mL in the colony forming assay and 0.75 mg/mL in the agar dilution test, with a zone of inhibition. Both EVB and EVB-CML displayed stronger antibacterial activity than four antimicrobial creams currently marketed in the United States. Moreover, this effect was rapid, favored by high temperature, and product stability testing suggested a shelf life of at least 10 months. Taken together, these findings demonstrate the ability of CML to enhance the antibacterial effect of the base EVB formulation against E. coli. This novel EVB-CML formulation represents a promising advancement toward improved antibacterial efficacy beyond current industry standards for commercial skin creams and sunscreens.

ROS generation and p-38 activation contribute to montmorillonite-induced corneal toxicity in vitro and in vivo

BACKGROUND

Montmorillonite (Mt) and its derivatives are now widely used in industrial and biomedical fields. Therefore, safety assessments of these materials are critical to protect human health after exposure; however, studies on the ocular toxicity of Mt are lacking. In particular, varying physicochemical characteristics of Mt may greatly alter their toxicological potential. To explore the effects of such characteristics on the eyes, five types of Mt were investigated in vitro and in vivo for the first time, and their underlying mechanisms studied.

RESULTS

The different types of Mt caused cytotoxicity in human HCEC-B4G12 corneal cells based on analyses of ATP content, lactate dehydrogenase (LDH) leakage, cell morphology, and the distribution of Mt in cells. Among the five Mt types, Na-Mt exhibited the highest cytotoxicity. Notably, Na-Mt and chitosan-modified acidic Na-Mt (C-H-Na-Mt) induced ocular toxicity in vivo, as demonstrated by increases corneal injury area and the number of apoptotic cells. Na-Mt and C-H-Na-Mt also induced reactive oxygen species (ROS) generation in vitro and in vivo, as indicated by 2',7'-dichlorofluorescin diacetate and dihydroethidium staining. In addition, Na-Mt activated the mitogen-activated protein kinase signaling pathway. The pretreatment of HCEC-B4G12 cells with N-acetylcysteine, an ROS scavenger, attenuated the Na-Mt-induced cytotoxicity and suppressed p38 activation, while inhibiting p38 activation with a p38-specific inhibitor decreased Na-Mt-induced cytotoxicity.

CONCLUSIONS

The results indicate that Mt induces corneal toxicity in vitro and in vivo. The physicochemical properties of Mt greatly affect its toxicological potential. Furthermore, ROS generation and p38 activation contribute at least in part to Na-Mt-induced toxicity.

Adsorption and detoxification of glyphosate and aminomethylphosphonic acid by montmorillonite clays

The co-occurrence of mixtures of glyphosate (GLP) and aminomethylphosphonic acid (AMPA) in contaminated water, soil, sediment, and plants is a cause for concern due to potential threats to the ecosystem and human health. Major routes of exposure include contact with contaminated water and soil and through consumption of crops containing GLP and AMPA residues. Calcium montmorillonite (CM) and acid-processed montmorillonite (APM) clays were investigated for their ability to tightly sorb and detoxify GLP and AMPA mixtures. In vitro adsorption and desorption isotherms and thermodynamic analysis indicated saturable Langmuir binding of both chemicals with high capacities, affinities, enthalpies, and free energies of sorption and low desorption rates. In silico computational modeling indicated that both GLP and AMPA can be readily absorbed onto clay surfaces through electrostatic interactions and hydrogen bonding. The safety and efficacy of the clays were confirmed using well-established living organisms, including an aquatic cnidarian (Hydra vulgaris), a soil nematode (Caenorhabditis elegans), and a floating plant (Lemna minor). Low levels of clay inclusion (0.05% and 0.2%) in the culture medium resulted in increased growth and protection against chemical mixtures based on multiple endpoints. Results indicated that montmorillonite clays may be used to bind mixtures of GLP and AMPA in water, soil, and plants.

Development and characterization of chlorophyll-amended montmorillonite clays for the adsorption and detoxification of benzene

After disasters, such as forest fires and oil spills, high levels of benzene (> 1 ppm) can be detected in the water, soil, and air surrounding the disaster site, which poses a significant health risk to human, animal, and plant populations in the area. While remediation methods with activated carbons have been employed, these strategies are limited in their effectiveness due to benzene's inherent stability and limited retention to most surfaces. To address this problem, calcium and sodium montmorillonite clays were amended with a mixture of chlorophyll (a) and (b); their binding profile and ability to detoxify benzene were characterized using in vitro, in silico, and well-established ecotoxicological (ecotox) bioassay methods. The results of in vitro isothermal analyses indicated that chlorophyll-amended clays showed an improved binding profile in terms of an increased binding affinity (Kf = 668 vs 67), increased binding percentage (52% vs 11%), and decreased rates of desorption (28% vs 100%), compared to the parent clay. In silico simulation studies elucidated the adsorption mechanism and validated that the addition of the chlorophyll to the clays increased the adsorption of benzene through Van der Waals forces (i.e., aromatic π-π stacking and alkyl-π interactions). The sorbents were also assessed for their safety and ability to protect sensitive ecotox organisms (Lemna minor and Caenorhabditis elegans) from the toxicity of benzene. The inclusion of chlorophyll-amended clays in the culture medium significantly reduced benzene toxicity to both organisms, protecting C. elegans by 98-100% from benzene-induced mortality and enhancing the growth rates of L. minor. Isothermal analyses, in silico modeling, and independent bioassays all validated our proof of concept that benzene can be sequestered, tightly bound, and stabilized by chlorophyll-amended montmorillonite clays. These novel sorbents can be utilized during disasters and emergencies to decrease unintentional exposures from contaminated water, soil, and air.

Inclusion of Montmorillonite Clays in Environmental Barrier Formulations to Reduce Skin Exposure to Water-Soluble Chemicals from Polluted Water

Dermal exposures to environmental chemicals can significantly affect the morphology and integrity of skin structure, leading to enhanced and deeper penetration of toxic chemicals. This problem can be magnified during disasters where hazardous water-soluble chemicals are readily mobilized and redistributed in the environment, threatening the health of vulnerable populations at the impacted sites. To address this issue, barrier emulsion formulations (EVB) have been developed consisting of materials that are generally recognized as safe, with the inclusion of medical grade carbon or calcium and sodium montmorillonite clays (CM and SM). In this study, the adsorption efficacy of five highly toxic and commonly occurring contaminants of concern, including important hydrophilic pesticides (glyphosate, acrolein, and paraquat) and per- and polyfluoroalkyl substances were characterized. EVB showed properties such as high stability, spreadability, low rupture strength, and neutral pH that were suitable for topical application on the skin. The in vitro adsorption results indicated that EVB and EVB-SM were effective, economically feasible, and favorable barrier formulations for hazardous chemical adsorption, as supported by high binding percentage, low desorption rates for an extended period of time, and high binding affinity. A pseudo-second-order kinetic model was best fitted for the adsorption process and the Freundlich model fit the adsorption isotherms with negative enthalpy values indicating spontaneous reactions that involve physisorption. The study, with varying temperatures and pH, showed that the adsorption reaction was exothermic and persistent. The results indicated that EVB and EVB-SM can be used as effective barriers to block dermal contact from water-soluble toxic pollutants during disasters.

Montmorillonite clay-based sorbents decrease the bioavailability of per- and polyfluoroalkyl substances (PFAS) from soil and their translocation to plants

Consumption of food and water contaminated with per- and polyfluoroalkyl substances (PFAS) presents a significant risk for human exposure. There is limited data on high affinity sorbents that can be used to reduce the bioavailability of PFAS from soil and translocation to plants and garden produce. To address this need, montmorillonite clay was amended with the nutrients carnitine and choline to increase the hydrophobicity of the sorbent and the interlayer spacing. In this study, the binding of PFOA (perfluorooctanoic acid) and PFOS (perfluorooctanesulfonic acid) to parent and amended clays was characterized. Isothermal analyses were conducted at pH 7 and ambient temperature to simulate environmentally-relevant conditions. The data for all tested sorbents fit the Langmuir model indicating saturable binding sites with high capacities and affinities under neutral conditions. Amended montmorillonite clays had increased capacities for PFOA and PFOS (0.51-0.71 mol kg^-1) compared to the parent clay (0.37-0.49 mol kg^-1). Molecular dynamics (MD) simulations suggested that hydrophobic and electrostatic interactions at the terminal fluorinated carbon chains of PFAS compounds were major modes of surface interaction. The safety and efficacy of the clays were confirmed in a living organism (Lemna minor), where clays (at 0.1% inclusion) allowed for increased growth compared to PFOA and PFOS controls (p ≤ 0.01). Importantly, soil studies showed that 2% sorbent inclusion could significantly reduce PFAS bioavailability from soil (up to 74%). Studies in plants demonstrated that inclusion of 2% sorbent significantly reduced PFAS residues in cucumber plants (p ≤ 0.05). These results suggest that nutrient-amended clays could be included in soil to decrease PFAS bioavailability and translocation of PFAS to plants.