Intrinsic catalytic activity of rhodium nanoparticles with respect to reactive oxygen species scavenging: implication for diminishing cytotoxicity.

Noble metal nanoparticles (NPs) and their hybrids have demonstrated a strong potential to mimic the catalytic activity of natural enzymes and diminish oxidative stress. There is a large space to explore the intrinsic catalytic activity of Rh NPs with respect to reactive oxygen species (ROS) scavenging. We found that Rh NPs can quench H2O2, •OH, O2•-, 1O2 and inhibit lipid peroxidation under physiological conditions. In vitro cell experiments proved that Rh NPs have great biocompatibility and protect cells from oxidative damage caused by H2O2. This study can provide important insights that could inform future biological applications.

Spectroelectrochemical Reverse Engineering DemonstratesThat Melanin's Redox and Radical Scavenging Activities Are Linked.

Melanins are ubiquitous in nature but their biological activities and functions have been difficult to discern. Conventional approaches to determine material function start by resolving structure and then characterize relevant properties. These approaches have been less successful for melanins because of their complex structure and insolubility, and because their relevant properties are not readily characterized by conventional methods. Here, we report a novel spectroelectrochemical reverse engineering approach that focuses on redox and radical scavenging activities. In this method, the melanin is immobilized in a permeable hydrogel film adjacent to an electrode and this immobilized melanin is probed using diffusible mediators and complex electrical inputs. Response characteristics are measured using two modalities, electrochemical currents associated with the reaction of diffusible mediators, and optical absorbance associated with the presence of diffusible free radicals. Using this method, we observed that both Sepia and fungal melanins are redox active and can repeatedly exchange electrons to be switched between oxidized and reduced states. Further, we observed that these melanins can quench radicals either by donating or accepting electrons. Finally, we demonstrate that the melanins' radical scavenging activities are dependent on their redox state such that a melanin must be reduced to have donatable electrons to quench oxidative free radicals, or must be oxidized to accept electrons from reductive free radicals. While the observation that melanin is redox-active is consistent with their well-accepted beneficial (radical-scavenging) and detrimental (pro-oxidant) activities, these observations may also support less well-accepted proposed functions for melanin in energy harvesting and redox communication.

A tubular one-dimensional polymer constructed from alternating clusters of europium(III)-water and copper(I) chloride bridged by 4-(pyridin-4-yl)benzoate.

A new 3d-4f heterometallic polymer, poly[[aqua-µ3-chlorido-[µ3-4-(pyridin-4-yl)benzoato]tris[µ2-4-(pyridin-4-yl)benzoato]dicopper(I)erbium(III)] dihydrate], {[Cu2Er(C12H8NO2)4Cl(H2O)]·2H2O}n, was synthesized by the hydrothermal reaction of Er2O3, CuCl2·2H2O and 4-(pyridin-4-yl)benzoic acid in the presence of HClO4. The asymmetric unit contains one Er(3+) cation, two Cu(+) cations, one Cl(-) anion, four deprotonated 4-(pyridin-4-yl)benzoate ligands, one coordinated aqua ligand and two solvent water molecules. This tubular one-dimensional polymer is constructed from alternating clusters of europium(III)-water and copper(I) chloride bridged by 4-(pyridin-4-yl)benzoate ligands. Extensive hydrogen-bonding interactions involving both the coordinated and the solvent water molecules provide further stabilization to the structure.