Chromium (VI) removal by magnetite nanoparticles immobilized with extracellular polymeric substances extracted from Lysinibacillus sp. WH.

Magnetite nanoparticles (nano-Fe3O4) and nano-Fe3O4 immobilized with bacterial extracellular polymeric substances (EPSs) extracted from Lysinibacillus sp. WH (Fe3O4/bact) were comparatively studied for the removal of Cr (VI) ions from aqueous solution in batch study. The objectives were to explore the removal of Cr (VI) efficiency by nano-Fe3O4 and Fe3O4/bact under varying bacterial concentrations at a range of acidic pH. Results indicated that 150 ppm Cr (VI) could be effectively removed by 5 g/L of nano-Fe3O4 at pH 4, with the efficiency of 89.2 ± 12%. The equilibrium time, determined by a pseudo-second-order model (R2 = 0.9983), was after 5 h, indicating chemical adsorption. The Cr (VI) removal by the nano-Fe3O4 immobilized with bacterial EPS was effective and steady under a wide range of acidic conditions although bacterial EPS has an alkaline nature. Here, we are the first to demonstrate that Cr (VI) removal efficiency by different concentrations of EPS was not significantly different, suggesting EPS concentration is possibly not the most crucial factor to be optimized for Cr (VI) removal in the future. This study shows the potential application of nano-Fe3O4 immobilized with bacterial EPS for wastewater treatment. PRACTITIONER POINTS: The equilibrium time for magnetite nanoparticles to remove Cr (VI) is 5 h, suggesting chemical adsorption. The Cr (VI) removal efficiency of either magnetite nanoparticles or bacterial EPS is stable under a wide range of acidic conditions. Magnetite nanoparticles immobilized with bacterial EPS extracted from Lysinibacillus sp. WH has a potential application for Cr (VI) removal in wastewater.

Magnetite nanoparticles: an emerging adjunctive tool for the improvement of cancer immunotherapy.

Cancer immunotherapy has emerged as a groundbreaking field, offering promising and transformative tools for oncological research and treatment. However, it faces several limitations, including variations in cancer types, dependence on the tumor microenvironments (TMEs), immune cell exhaustion, and adverse reactions. Magnetic nanoparticles, particularly magnetite nanoparticles (MNPs), with established pharmacodynamics and pharmacokinetics for clinical use, hold great promise in this context and are now being explored for therapeutic aims. Numerous preclinical studies have illustrated their efficacy in enhancing immunotherapy through various strategies, such as modulating leukocyte functions, creating favorable TMEs for cytotoxic T lymphocytes, combining with monoclonal antibodies, and stimulating the immune response via magnetic hyperthermia (MHT) treatment (Front Immunol. 2021;12:701485. doi: 10.3389/fimmu.2021.701485). However, the current clinical trials of MNPs are mostly for diagnostic aims and as a tool for generating hyperthermia for tumor ablation. With concerns about the adverse effects of MNPs in the in vivo systems, clinical translation and clinical study of MNP-boosted immunotherapy remains limited. The lack of extensive clinical investigations poses a current barrier to patient application. Urgent efforts are needed to ascertain both the efficacy of MNP-enhanced immunotherapy and its safety profile in combination therapy. This article reviews the roles, potential, and challenges of using MNPs in advancing cancer immunotherapy. The application of MNPs in boosting immunotherapy, and its perspective role in research and development is also discussed.

Influence of organic ligands on the stoichiometry of magnetite nanoparticles.

Magnetite, a ubiquitous mineral in natural systems, is of high interest for a variety of applications including environmental remediation, medicine, and catalysis. If the transformation of magnetite to maghemite through the oxidation of Fe2+ has been well documented, mechanisms involving dissolution processes of Fe2+ in aqueous solutions have been overlooked. Here, the effect of dissolved organic ligands (EDTA (ethylenediaminetetraacetic acid), acetic, lactic and citric acids) on Fe2+ solubility and on the stoichiometry (Fe(ii)/Fe(iii)) of magnetite-maghemite nanoparticles (∼10 nm) was investigated. These ligands were chosen because of their environmental relevance and because they are widely used as coating agents for nanotechnology applications. Results show an insignificant effect of 2 organic ligands (acetate and lactate) on the dissolution of Fe. By contrast, citrate and EDTA enhanced Fe solubility because of the formation of dissolved Fe(ii)- and Fe(iii)-ligand complexes. Both ligands selectively bound Fe(ii) over Fe(iii), but EDTA was much more selective than citrate. The combined effects of oxidation and H+- and ligand-promoted dissolution of Fe from magnetite were predicted using a magnetite-maghemite solid solution model, accounting for the formation of dissolved Fe(ii)- and Fe(iii)-ligand complexes. Therefore, these results show that citrate and EDTA (i) enhance Fe solubility in the presence of magnetite nanoparticles and (ii) modify magnetite stoichiometry, which affects its environmental behavior and its properties for nanotechnology applications.

Copper and chromium removal from industrial sludge by a biosurfactant-based washing agent and subsequent recovery by iron oxide nanoparticles.

Industrial wastewater treatment generates sludge with high concentrations of metals and coagulants, which can cause environmental problems. This study developed a sequential sludge washing and metal recovery process for industrial sludge containing > 4500 mg/kg Cu and > 5000 mg/kg Cr. The washing agent was formulated by mixing glycolipid, lipopeptide, and phospholipid biosurfactants from Weissella cibaria PN3 and Brevibacterium casei NK8 with a chelating agent, ethylenediaminetetraacetic acid (EDTA). These biosurfactants contained various functional groups for capturing metals. The optimized formulation by the central composite design had low surface tension and contained relatively small micelles. Comparable Cu and Cr removal efficiencies of 37.8% and 38.4%, respectively, were obtained after washing the sludge by shaking with a sonication process at a 1:4 solid-to-liquid ratio. The zeta potential analysis indicated the bonding of metal ions on the surface of biosurfactant micelles. When 100 g/L iron oxide nanoparticles were applied to the washing agent without pH adjustment, 83% Cu and 100% Cr were recovered. In addition, X-ray diffraction and X-ray absorption spectroscopy of the nanoparticles showed the oxidation of nanoparticles, the reduction of Cr(V) to the less toxic Cr(III), and the absorption of Cu. The recovered metals could be further recycled, which will be beneficial for the circular economy.