Preparation, morphology, antiradical and biological activity of quercetin-containing nanoparticles of zein and their submicron aggregates

Abstract

Nanoparticles of corn prolamine protein zein (NPQ) containing 0.005–0.26 g/g quercetin (Q) were prepared by desolvation of a 25–30 mg/mL ethanol protein solution containing the encapsulated compound with an aqueous polystyrene sulfonate. The size of zein nanoparticles and their aggregates was characterized by dynamic light scattering and atomic force microscopy; the quercetin content – by the Folin-Ciocalteu assay. While the quercetin/zein ratio in solution is less than 0.08 g/g, the polyphenol is quantitatively included in the nanoparticles, and their hydrodynamic diameter is 60–75 nm. As the quercetin/zein ratio rises to 0.20 g/g, the average particle diameter increases to 150 nm. In concentrated dispersions, aggregates with a diameter of 500–600 nm are formed. The kinetics of quercetin release from NPQ with different mass fractions of Q in distilled water and solutions simulating the environment of the stomach and intestines at 37 °C were studied.Zein nanoparticles exhibit weak activity in the reaction with ABTS cation-radicals. Quercetin encapsulated in the zein matrix generally retains the antiradical activity characteristic of the free flavonoid, however, the rate of decolorization of ABTS cation-radicals decreases due to the prolonged release of quercetin from NPQ. The cytoprotective properties of quercetin in zein nanoparticles are significantly reduced and manifest themselves only in partial preservation of the integrity of cell membranes and a decrease in the release of lactate dehydrogenase from UV-C irradiated HaCaT cells. In contrast to free quercetin, the introduction of Q in zein nanoparticles or their submicron aggregates increases the number of metabolically dead UV-C-irradiated HaCaT cells, enhancing the cytotoxic effect of UV radiation. Empty zein aggregates of submicron size have a similar effect.