Carbon Nanomaterials with SOD-like Activity: The Effect of the Ionic Strength.

Electrogenerated hydrophilic carbon (EHC) nanomaterials emerge as a highly attractive option for mimicking the activity of the superoxide dismutase enzyme (SOD) due to their exceptional water solubility and electron-transfer reversibility. Motivated by these properties, the EHC nanomaterials were utilized to assess the effect of ionic strength on the SOD-like activity. Superoxide anion radicals (O2•-) were generated using the hypoxanthine-xanthine oxidase system, with nitro blue tetrazolium chloride serving as the detecting system. A significant boost in the SOD-like activity was found via the addition of an electrolyte to the as-prepared nanomaterial solution. The effect of the electrolyte cation (Na+ and K+), as well as its counterion (Cl-, CH3COO-, and H2PO4-/HPO42-) were analyzed. Based on these studies, a new formulation for the preparation of the carbon-based nanomaterial was established. It was demonstrated that the SOD-like activity follows an enzyme-type catalytic activity rather than the stoichiometric scavenging of the superoxide anion radical. It was concluded that 12.71 µg/mL of the EHC nanomaterial exhibits catalytic activity comparable to 15.46 µg/mL of the native Cu/Zn-SOD enzyme. This study provides a starting point for the development of a new nanotool to fight the oxidative stress associated with pathophysiological conditions where SOD activity is depleted.

Hydrophilic Carbon Nanomaterials: Characterisation by Physical, Chemical, and Biological Assays.

A highly hydrophilic carbon nanomaterial was generated by using an electrochemical approach, and its structure, chemical composition, redox properties, antioxidant activity and effects on cells were characterised. It was found that the nanomaterial possesses a structure dominated by sp2 carbon atoms in a non-ordered carbon network formed by small clusters (<2 nm) of a carbonaceous material. This material has an outstanding capability for donating electrons and an unusual ability to bind metal cations. Antioxidant activity assays showed that it displays a high scavenging activity against both 2,2-diphenyl-1-picrylhydrazyl and 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) radicals, and a concentration-dependent ability to protect mitochondrial lipids and intracellular thiol groups from oxidation promoted by external oxidising agents. Cell-based assays also revealed that the nanomaterial has the ability to protect neuronal cells against oxidative damage and toxicity promoted by tert-butyl hydroperoxide and amyloid-ß1-42 peptide. These results, combined with the attractive methodology for generating this hydrophilic carbon-based nanomaterial, make this study the first step in addressing the therapeutic application of this new material.