Antioxidant activity of noble metal (gold, platinum)-biopolymer nanocomposites

Three different platinum-biopolymer nanocomposites have been prepared independently in the presence of hexachloroplatinic acid and biopolymers like fucoidan, alginic acid and sodium hyaluronate (NaHA) via sodium borohydride reduction. The average particle diameter of platinum nanoparticles using fucoidan becomes slightly smaller, with a decrease of the concentration of fucoidan, ranging from 3.1 to 2.6nm. On the other hand, the average particle diameter of platinum nanoparticles using NaHA becomes slightly larger, with a decrease of the concentration of NaHA, ranging from 3.4nm to 3.8nm. The average particle diameter of platinum nanoparticles using alginic acid is 3.2-3.4nm which is independent of the biopolymer concentrations. The antioxidant activities of the platinum-biopolymer nanoconiposites upon elimination of hydroxyl radicals formed in an H 2 O 2 /FeSO 4 system have been studied using a spin-trapping method; All the nanocomposites exhibit high catalytic activities that are affected by the concentration and the kind of the biopolymer. In addition, the activities of the platinum-biopolymer nanocomposites are higher than those of the gold biopolymer nanocomposites. The highest antioxidant activity for the platinum-alginic acid nanocomposites was 110 times higher than that of ascorbic acid.