Microbial exopolysaccharide based nanoemulsions containing β-carotene: Stability, digestion, cytotoxicity, and uptake effects in Macrophages and Caco-2 cells.

The aim of this study was to develop and characterize nanoemulsions stabilized with microbial exopolysaccharide (EPS) (NE) and explore their performance in encapsulating β-carotene (βC-NE), in addition to evaluating their proliferative effects and uptake colorectal adenocarcinoma cells (Caco-2). βC-NE was obtained by ultrasonic homogenization followed by encapsulation of 0.1 % (w/v) β-carotene dispersed in the oil phase and was characterized by Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC), proton nuclear magnetic resonance (H NMR), and observed by transmission electron microscopy (TEM) and scanning electron microscopy (SEM). The long-term stability was evaluated under different pH and temperature conditions, as well as mechanical and thermal stress, and simulated digestion. Additionally, in vitro tests were conducted to assess cytotoxicity and cellular uptake in J774A.1 macrophages and Caco-2 cells. Spherical shaped NE showed a mean diameter size of 298.70 ± 1.60 nm and a polydispersity index (PDI) of 0.25, while βC-NE showed 515.20 ± 6.45 nm and a PDI of 0.22 with an encapsulation efficiency of 98.86 ± 0.83 %. In the simulated digestion, the size and PDI of NE and βC-NE increased, which resulted in the release of 40.37 % of β-carotene after 48 h, revealing the ability of the active compound to be constantly released into the intestinal fluid and the bioavailability for absorption. The MTT assay revealed that the formulations are not toxic to macrophages and Caco-2 cells, with cellular uptake in the first 15 min. Therefore, it was possible to develop an oil/water NE, stabilized only with microbial EPS, which can effectively transport and protect β-carotene. Thus, NE and βC-NE are promising for incorporation into food and future in vivo efficiency studies.