Hybrids of Gallic Acid@SiO and {Hyaluronic-Acid Counterpats}@SiO against Hydroxyl (OH) Radicals Studied by EPR: A Comparative Study vs Their Antioxidant Hydrogen Atom Transfer Activity.

Hydrogen atom transfer (HAT) and single electron transfer (SET) are two fundamental pathways for antiradical/antioxidant processes; however, a systematic operational evaluation of the same system is lacking. Herein, we present a comparative study of the HAT and SET processes applied to a library of well-characterized hybrid materials SiO@GA, SiO@GLA, SiO@GLAM, and the doubly hybrid material {GLA@SiO@GLAM}. Hydroxyl radicals (OH), produced by a Fenton system, react via the single electron transfer (SET) pathway and hydrogen atom transfer, through oxygen- and carbon-atoms, respectively, while the stable-radical DPPH via the HAT pathway through oxygen-atoms.

Nanoantioxidant Materials: Nanoengineering Inspired by Nature.

Oxidants are very active compounds that can cause damage to biological systems under specific environmental conditions. One effective way to counterbalance these adverse effects is the use of anti-oxidants. At low concentrations, an antioxidant is defined as a compound that can delay, control, or prevent an oxidative process.

Antioxidant Hydrogen-Atom-Transfer to DPPH Radicals by Hybrids of {Hyaluronic-Acid Components}@SiO.

Hydrogen-atom-transfer (HAT) is among the key mechanisms of antioxidant and antiradical activity in natural systems. Hyaluronic acid (HyA) is currently used extensively in health and cosmetics applications. Herein it is shown that {HyA@SiO} hybrids based on hyaluronic acid (HyA) components grafted on SiO nanoparticles enable significant HAT activity versus DPPH radicals, while the homogeneous HyA counterparts are practically inactive.