Astaxanthin-loaded nanoparticles enhance its cell uptake, antioxidant and hypolipidemic activities in multiple cell lines

Astaxanthin is a natural carotenoid pigment, which provides many benefits to human health and nutrition. However, the human body has a low bioavailability of astaxanthin due to its poor solubility in the water phase. This study aimed to prepare astaxanthin nanoparticles using an emulsification/solvent evaporation method and then to evaluate bioavailability of nano-astaxanthin for biomedical applications. The results showed that the combinative use of cremophor RH40 as surfactants and polyethylene glycol–polylactic acid copolymer as an encapsulation agent generated well-defined astaxanthin nanoparticles with 5% astaxanthin content. These nanoparticles exhibited spherical morphology with average particle diameters of 90 nm. Nanoastaxanthin had high DPPH free radical scavenging activity and significantly improved cell uptake compared to the free astaxanthin. Astaxanthin nanoparticles showed no cytotoxicity against HT29, HepG2 and RAW264.7 cells up to a concentration of 500 μg/mL and event showed a more powerful cytoprotective effect on H2O2-induced oxidative HepG2 cell damage at concentrations of 50 and 100 μg/mL. Besides that, the activity of antioxidant enzymes (catalase and glutathione peroxidase) and gene expressions of Nrf2, HO-1 and NQO1 increased concentration-dependently, while the mRNA level of Keap1 significantly decreased in cells incubated with nanoastaxanthin compared to astaxanthin and control groups. Moreover, hepatocytes and murine RAW264.7 macrophages treated with nanoastaxanthin, but not with free astaxanthin, displayed to reduce cellular lipid accumulation compared with control cells via altering the expression of key genes in lipid metabolism (LDLR, CYP7A1, FAS, PPARα, CPT-1 and LXRα in HepG2 cells and ABCA1 and G1 in RAW264.7 cells). Our results highlight the great potential of nanoastaxanthin for applications in human health and nutrition.