Atul Asati

Oxidase activity of polymeric coated cerium oxide nanoparticles

Inorganic enzyme? Ceria nanoparticles exhibit unique oxidase-like activity at acidic pH values. These redox catalysts can be used in immunoassays (ELISA) when modified with targeting ligands (see picture; light blue and yellow structures are nanoparticles with attached ligands). This modification allows both for binding and for detection by the catalytic oxidation of sensitive colorimetric dyes (e.g. TMB).

Synthesis of Biocompatible Dextran‐Coated Nanoceria with pH‐Dependent Antioxidant Properties

Recent reports indicate that cerium oxide nanoparticles (nanoceria) are potent free-radical scavengers with neuroprotective, radioprotective, and anti-inflammatory properties. Nanoceria also have the unique property of being regenerative or autocatalytic. These results point to the possibility of engineering nanoceria with selective antioxidant properties that promote cell survival under conditions of oxidative stress. However, most of these studies have been done with nanoparticles with poor water solubility or synthesized by procedures involving toxic solvents, therefore hindering their potential clinical use. Herein, we report a facile synthesis of monodisperse, water-soluble, and highly crystalline dextran-coated nanoceria (DNC). The improved water solubility of DNC allowed for studies that show a unique pHdependent antioxidant activity that could have important applications in the design of improved therapeutics and in tailoring its antioxidant properties. Our synthetic procedure involves the alkaline-based precipitation of cerium oxide (Ce2O3:CeO2) from a solution containing cerium salt and dextran. Briefly, an aqueous solution of cerium nitrate and dextran was added to an ammonia solution under continuous stirring. Upon formation of the cerium oxide nanocrystals, molecules of dextran coat the nanoparticles’ surface, preventing further growth and resulting in dextran-coated nanoceria (DNC). The DNC preparation is stable in phosphate-buffered saline (PBS) at concentrations of 40mM or higher for months. DNC demonstrates good water stability even after several heating cycles (70–80 8C) with no sedimentation upon centrifugation at 8000 rpm for 30min. These characteristics make our waterbased synthetic method advantageous over organic-solventbased preparations, which are prone to aggregation when suspended in aqueous media.

Nanoceria facilitates the synthesis of poly(o-phenylenediamine) with pH-tunable morphology, conductivity, and photoluminescent properties.

Poly(ortho-phenylenediamine) synthesis enabled by the catalytic oxidase-like activity of nanoceria was accomplished for applications in electronics, medicine, and biotechnology. The polymer shows unique morphology, conductivity, and photoluminescence based on pH of the solution during synthesis. The various poly(ortho-phenylenediamine) preparations were characterized by UV-visible spectroscopy, scanning electron microscopy, fluorescence spectroscopy, fluorescence microscopy, high-pressure liquid chromatography, and cyclic voltammetry. Poly(ortho-phenylenediamine) synthesized at pH 1.0 by nanoceria was selected to be extensively studied on the basis of the fast synthetic kinetics and the resulting conductive and photoluminescent properties for various applications.