Curcumin-loaded zein/pectin nanoparticles: Caco-2 cellular uptake and the effects on cell cycle arrest and apoptosis of human hepatoma cells (HepG2)

Curcumin is a natural plant component with enormous in vitro anticancer effects. However, the bioavailability of curcumin is limited due to its poor solubility in water. Our previous studies showed that zein pectin core/shell nanoparticle-encapsulated curcumin (En-CUR) improved the solubility and bioaccessibility of curcumin. In this study, the transportation mechanism of En-CUR into Caco-2 cells and the inhibitory effects of En-CUR on HepG2 cell proliferation were investigated. The results showed that the uptake of En-CUR by Caco-2 cells required energy consumption. Caveolae-mediated endocytosis, clathrin-dependent endocytosis, and macropinocytosis were involved in the uptake of En-CUR by Caco-2 cells. The apoptosis rate of HepG2 cells after En-CUR treatment was 31.2%, which was approximately two-fold higher than that of the CUR-treated cells treated with curcumin at a concentration of 10 μg/mL, and the early apoptosis rate of En-CUR-treated cells was 2.7–3.3 times higher than that of CUR-treated cells. En-CUR-treated HepG2 cells exhibited more significant cell cycle arrest at cell cycle checkpoints S and G2/M than CUR-treated cells. En-CUR also decreased mitochondrial membrane potential. Western blot analysis revealed that En-CUR increased Bax protein expression, activated caspase-3 and caspase-9, and increased cytochrome c and p53 protein levels in HepG2 cells. Our results suggested that zein-pectin core/shell nanoparticles were desirable curcumin delivery systems and exhibited superior cancer cell antiproliferative effects.