Synthesis and enhanced antioxidant and membrane-protective activity of curcumin@AlOOH nanoparticles.

The ever increasing demand for nanoantioxidants with minimized toxicity dictates the necessity to develop new biocompatible materials. One promising approach is the immobilization of polyphenols on metal (oxy)hydroxide nanoparticles (NPs) that possess the desired chemical and colloidal stability while also allowing to dispose of the antioxidants more safely and effectively. In this paper we modify sol-gel synthesized γ-AlOOH NPs with curcumin molecules. The prepared colloidal systems are hydrosols, stable in acidic, neutral and slightly basic pH values. UV-vis and FTIR spectroscopies suggest that the mechanism of curcumin binding lies in the H-bonding of its functional groups to hydroxyls of pseudoboemite. Modification of AlOOH nanoparticles shifts its isoelectric point from 9.7 to 9.3 due to the weak acidic centers of the polyphenol. Immobilization of curcumin molecules on pseudoboehmite allows to achieve good solubility of the phenol in water and to reduce the level of its hemolytic activity (indicating good biocompatibility). At the same time, it preserves radical scavenging activity and in some experimental designs even enhances antioxidant and membrane-protective activity (enhancement ≥30%) in vitro on cellular and non-cellular models.