Zinc oxide (ZnO) nanoparticles (NPs) are used as a food additive Zn supplement due to the role of Zn in biological functions. They are directly added to complex processed foods or Zn-fortified functional foods. Hence, the interactions between ZnO NPs and nutritional or functional components can occur. In this study, the effects of ZnO NP interactions with two polyphenols (quercetin and rutin) on cytotoxicity, antioxidant activity, ex vivo intestinal absorption, and solubility were evaluated. Moreover, the characterization on the interactions was carried out by analyzing crystallinity, surface chemical bonding, chemical composition, and surface chemistry. The results demonstrate that the interactions caused higher cytotoxicity, ex vivo intestinal transport, and solubility of ZnO NPs than pristine ZnO NPs but did not affect antioxidant activity nor intestinal absorption of the polyphenols. The interaction effects were more evident by ZnO NPs interacted with quercetin than with rutin. The crystallinity of ZnO NPs was not influenced, but the degree of exposure of the chemical bondings, elemental compositions, and chemical group intensities on the surface of ZnO NPs, quercetin, or rutin were quenched or decreased to some extent by the interactions, especially by ZnO NPs interacted with quercetin. It is, therefore, concluded that the interactions affect chemical characteristics and surface chemical sates of ZnO NPs, quercetin, or rutin, which can cause high cytotoxicity, intestinal absorption, and solubility of ZnO NPs. Further study is required to elucidate the mechanism of action of the interactions.
Keywords: biological responses; characteristics; interactions; quercetin; rutin; surface chemistry; zinc oxide nanoparticles.