Some unusual staining properties of tannic acid in plants

Magnetic-Propelled Janus Yeast Cell Robots Functionalized with Metal-Organic Frameworks for Mycotoxin Decontamination

Cell robots that transform natural cells into active platforms hold great potential to enrich the biomedical prospects of artificial microrobots. Here, we present Janus yeast cell microrobots (JYC-robots) prepared by asymmetrically coating Fe₃O₄ nanoparticles (NPs) and subsequent in situ growth of zeolitic imidazolate framework-67 (ZIF-67) on the surface of yeast cells. The magnetic actuation relies on the Fe₃O₄ NPs wrapping. As the compositions of cell robots, the cell wall with abundant polysaccharide coupling with porous and oxidative ZIF-67 can concurrently remove mycotoxin (e.g., zearalenone (ZEN)). The magnetic propulsion accelerates the decontamination efficiency of JYC-robots against ZEN. Although yeast cells with fully coating of Fe₃O₄ NPs and ZIF-67 (FC-yeasts) show faster movement than JYC-robots, higher toxin-removal efficacy is observed for JYC-robots compared with that of FC-yeasts, reflecting the vital factor of the yeast cell wall in removing mycotoxin. Such design with Janus modification of magnetic NPs (MNPs) and entire coating of ZIF-67 generates active cell robot platform capable of fuel-free propulsion and enhanced detoxification, offering a new formation to develop cell-based robotics system for environmental remediation.

Design, characterization and in vitro evaluation of thin films enriched by tannic acid complexed by Fe(III) ions

Materials based on carbohydrate polymers may be used for biomedical application. However, materials based on natural polymers have weak physicochemical properties. Thereby, there is a challenge to improve their properties without initiation of toxicity. The alternative method compared to toxic chemical agents’ addition is the use of metal complexation method. In this study, chitosan/tannic acid mixtures modified by Fe(III) complexation are proposed and tested for potential applications as wound dressings. Thereby, surface properties, blood compatibility as well as platelet adhesion was tested. In addition, the periodontal ligament stromal cells compatibility studies were carried out. The results showed that the iron(III) addition to chitosan/tannic acid mixture improves properties due to a decrease in the surface free energy and exhibited a reduction in the hemolysis rate (below 5%). Moreover, cells cultured on the surface of films with Fe(III) showed higher metabolic activity. The current findings allow for the medical application of the proposed materials as wound dressings.

Study of Complexes of Tannic Acid with Fe(III) and Fe(II)

UV-Vis absorption spectra of tannic acid were gained at pH 1.0∼9.0. Due to the pH value dependence of complex, the stoichiometry of tannic acid with iron ions was tested in buffer solution by the mole ratio method. The result suggests that the complex ratio of tannic acid to Fe(III) is 1 : 1 and to Fe(II) 3 : 1 in the carbonate buffer solution, and the complex ratio of iron-tannic complexes is 1 : 1 at pH 2.2. Due to the different color changes of tannic acid with iron ions in the coordination reactions, a tannic acid test paper was designed. The concentrations of Fe(III) more than 5.000 × 10^-6 mol/L and the concentrations of Fe(II) more than 1.000 × 10^-5 mol/L in aqueous solution can be detected by this test paper.