The flavonoid quercetin (QU) is a naturally occurring compound with several biological activities. However, the oral bioavailability of this compound is very low due to the high pre-systemic metabolism in the colon and liver and its low water solubility. In this context, the development of QU-loaded nanocarriers (NEs) is a promising approach to improve the drug oral bioavailability. This study investigates the variation of the concentration of 12-hydroxystearic acid-polyethylene glycol copolymer, lecithin and castor oil (CO) as to increase the amount of QU encapsulated while maintaining physicochemical characteristics described in previous studies. To better understand the ability to load and release the drug, we investigated the molecular interactions between QU and NE. Lipid-based NEs were prepared using CO as oily phase and PEG 660-stearate and lecithin as surfactants. Hot solvent diffusion and phase inversion temperature were methods employed to produce NEs. The QU-NEs were investigated for physicochemical characteristics and in vitro drug release. Molecular interactions between QU and the NEs were monitored through the complementary infrared (Fourier transform infrared) and NMR. The results revealed that it was possible to incorporate higher amounts of QU in a lipid-based NE with a reduced size (20 nm). The system developed allow a sustained release of QU probably due to the shell formed by the surfactants around the NE and the flavonoid ordering effect in the emulsion hydrophobic regions, which may reduce the system permeability.
Keywords: Quercetin; cryo-TEM; lipid nanocarriers; molecular interactions; nanotechnology.