Magnetic nanostructured agents for the mitigation of mycotoxins and cyanotoxins in the food chain.

Natural toxins, such as mycotoxins and cyanotoxins, can contaminate food and feed, leading to toxicity in humans and animals. This study focused on using nine magnetic nanostructured agents to remove the main types of toxins. Initially, the efficacy of these materials was evaluated in water solutions, revealing that composites with sizes below 3 mm, containing magnetite, activated carbon, esterified pectin, and sodium alginate, removed up to 90% of mycotoxins and cyanotoxins with an adsorption of 873 ng/g. The application of the nanostructures was then assessed in beer, milk, Distillers Dried Grains with Solubles and water contaminated with cyanobacteria. The presence of matrix slightly decreases the adsorption capacity for some toxins. The maximum toxin removal capacity was calculated with cyanotoxins, composites achieved a removal of up to 0.12 mg/g, while nanocomposites (15 µm) reached 36.6 mg/g. Therefore, these findings point out the potential for using nanotechnology in addressing natural toxins contamination.

Nanostructured Magnetic Particles for Removing Cyanotoxins: Assessing Effectiveness and Toxicity In Vitro.

The rise in cyanobacterial blooms due to eutrophication and climate change has increased cyanotoxin presence in water. Most current water treatment plants do not effectively remove these toxins, posing a potential risk to public health. This study introduces a water treatment approach using nanostructured beads containing magnetic nanoparticles (MNPs) for easy removal from liquid suspension, coated with different adsorbent materials to eliminate cyanotoxins. Thirteen particle types were produced using activated carbon, CMK-3 mesoporous carbon, graphene, chitosan, 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO)-oxidised cellulose nanofibers (TOCNF), esterified pectin, and calcined lignin as an adsorbent component. The particles' effectiveness for detoxification of microcystin-LR (MC-LR), cylindrospermopsin (CYN), and anatoxin-A (ATX-A) was assessed in an aqueous solution. Two particle compositions presented the best adsorption characteristics for the most common cyanotoxins. In the conditions tested, mesoporous carbon nanostructured particles, P1-CMK3, provide good removal of MC-LR and Merck-activated carbon nanostructured particles, P9-MAC, can remove ATX-A and CYN with high and fair efficacy, respectively. Additionally, in vitro toxicity of water treated with each particle type was evaluated in cultured cell lines, revealing no alteration of viability in human renal, neuronal, hepatic, and intestinal cells. Although further research is needed to fully characterise this new water treatment approach, it appears to be a safe, practical, and effective method for eliminating cyanotoxins from water.

Role of Dipolar Interactions on the Determination of the Effective Magnetic Anisotropy in Iron Oxide Nanoparticles.

Challenging magnetic hyperthermia (MH) applications of immobilized magnetic nanoparticles require detailed knowledge of the effective anisotropy constant (Keff ) to maximize heat release. Designing optimal MH experiments entails the precise determination of magnetic properties, which are, however, affected by the unavoidable concurrence of magnetic interactions in common experimental conditions. In this work, a mean-field energy barrier model (ΔE), accounting for anisotropy (EA ) and magnetic dipolar (ED ) energy, is proposed and used in combination with AC measurements to a specifically developed model system of spherical magnetic nanoparticles with well-controlled silica shells, acting as a spacer between the magnetic cores. This approach makes it possible to experimentally demonstrate the mean field dipolar interaction energy prediction with the interparticle distance, dij , ED ≈ 1/dij 3 and obtain the EA as the asymptotic limit for very large dij . In doing so, Keff uncoupled from interaction contributions is obtained for the model system (iron oxide cores with average sizes of 8.1, 10.2, and 15.3 nm) revealing to be 48, 23, and 11 kJ m-3 , respectively, close to bulk magnetite/maghemite values and independent from the specific spacing shell thicknesses selected for the study.

Magnetic nanostructures for marine and freshwater toxins removal.

Marine and freshwater toxins contaminate water resources, shellfish and aquaculture products, causing a broad range of toxic effects in humans and animals. Different core-shell nanoparticles were tested as a new sorbent for removing marine and freshwater toxins from liquid media. Water solutions were contaminated with 20 µg/L of marine toxins and up to 50 µg/L of freshwater toxins and subsequently treated with 250 or 125 mg/L of nanoparticles. Under these conditions, carbon nanoparticles removed around 70% of saxitoxins, spirolides, and azaspiracids, and up to 38% of diarrheic shellfish poisoning toxins. In the case of freshwater toxins, the 85% of microcystin LR was eliminated; other cyclic peptide toxins were also removed in a high percentage. Marine toxins were adsorbed in the first 5 min of contact, while for freshwater toxins it was necessary 60 min to reach the maximum adsorption. Toxins were recovered by extraction from nanoparticles with different solvents. Gymnodinium catenatum, Prorocentrum lima, and Microcystis aeruginosa cultures were employed to test the ability of nanoparticles to adsorb toxins in a real environment, and the same efficacy to remove toxins was observed in these conditions. These results suggest the possibility of using the nanotechnology in the treatment of contaminated water or in chemical analysis applications.

Detoxification agents based on magnetic nanostructured particles as a novel strategy for mycotoxin mitigation in food.

Mycotoxins are toxic compounds that can be present in feed, food and beverages. In this work, 25 magnetic nanostructured materials were developed to remove the main types of mycotoxins from liquid food matrices. The efficiency for binding mycotoxins from contaminated aqueous solutions was studied. Nanocomposites (diameters lower to 15 µm) composed of mixtures of activated carbon, bentonite and aluminium oxide were able to eliminate up to 87% of mycotoxins with an adsorption efficiency of 450 µg/g. On the other hand, spheres with sizes below 3 mm and composed by biopolymers and activated carbon or graphene oxide removed up to 70% of mycotoxins (adsorption of 598 ng/g). These particles were tested for beer detoxification, and spheres composed of alginate and activated carbon or pectin maintain the ability to eliminate toxins from this beverage. Hence, this technology could be a useful tool for the food industry.

Novel Magnetic Nanostructured Beads for Cadmium(II) Removal.

This study presents an effective magnetic separation method for cadmium removal, based on the use of a novel nanostructured material as an adsorbent. This adsorbent involves the incorporation of magnetite nanoparticles (Fe3O4-NPs), synthesized by the reverse coprecipitation method, into sodium alginate and activated carbon to form spherical structures by crosslinking Ca2+ ions with the charged alginate chains, referred to as magnetic alginate activated carbon (MAAC) beads. The effect of the experimental parameters, such as pH, contacting time, adsorbent dosage, agitation type, and rotating speed were investigated and optimized for an efficient removal of Cd(II) ions at an initial concentration of 250 mg/L. The amount of adsorbed Cd(II) by MAAC beads increased at a pH of 6 with a removal efficiency over 90%. The maximum adsorption capacity reached was 70 mg/g of adsorbent at an initial Cd(II) concentration of 150 mg/L, whereas at 250 mg/L the adsorption capacity lowered until 60 mg/g. Sorption isotherms were calculated using Langmuir, Freundlich, Temkin, and Dubinin⁻Radushkevich equations, and were better described by the Freundlich and Temkin models. These results proved the removal efficiency and the potential use under real environmental conditions of the MAAC beads, due to their easy recovery from contaminated aqueous solutions.