Resveratrol-loaded chitosan–γ-poly(glutamic acid) nanoparticles: Optimization, solubility, UV stability, and cellular antioxidant activity

The objective of this study was to investigate the effects of the particle size of resveratrol (RSV)-loaded nanoparticles (NPs) on their solubility and stability and to optimize their preparation conditions for their solubility and stability. RSV-loaded NPs were prepared using chitosan and γ-poly(glutamic acid) (γ-PGA). Although the solubility and stability of RSV have been significantly increased using chitosan/γ-PGA nanoencapsulation, as the NP size decreased, the solubility increased, but the stability decreased. In order to understand the interrelationship of particle size, solubility, and stability, the target values of RSV solubility and ultraviolet (UV) stability for the aforementioned optimization were determined at two levels: solubility >153 μg/mL, UV stability >12 % (S153U12) and solubility >150 μg/mL, UV stability >18 % (S150U18). The S150U18-NPs (258 nm) showed a significantly higher UV stability and tyrosinase inhibition activity against UVA than S153U12-NPs (87 nm) (p < 0.01). Although insignificant, the S153U12-NPs exhibited higher solubility than the S150U18-NPs. In addition, the cellular antioxidant activity was significantly higher in the S153U12-NPs than the S150U18-NPs (p < 0.05). These results demonstrated that the solubility and stability of RSV-loaded NPs may be influenced by their particle size, which could be controlled by the chitosan and γ-PGA concentrations.