Natural deep eutectic solvents assisted the encapsulation of curcumin in gellan gum hydrogels

In this study, curcumin (Cur) was encapsulated within a gellan gum (GG) gel using natural deep eutectic solvents (NADES) to enhance its gastrointestinal retention. Three NADES-composed of malic acid-glucose (MA-Glu), malic acid-xylitol (MA-Xyl), and betaine-malic acid (Bet-MA)-were introduced to combine with GG to form hydrogels. The initial elastic moduli of GG hydrogels increased approximately 5-, 7-, and 20-fold with the incorporation of NADES(MA-Glu), NADES(MA-Xyl), and NADES(Bet-MA), respectively. The microstructure of the corresponding systems transformed from large pores to dense mesh networks with solid walls, accompanied by 1-3-fold increases in percentage area, junction number, and total vessel length, along with a 25%-53% decrease in lacunarity compared to pure GG hydrogels. The most obvious blue shift in the OH band was observed in the NADES(Bet-MA)/GG systems in comparison to GG and NADES. The most effective protection against Cur from releasing in the gastrointestinal tract, with the lowest release rate of 29%, was observed in NADES(Bet-MA)/GG-Cur. Molecular dynamics simulations further confirmed that the NADES(Bet-MA)/GG-Cur systems had the lowest total water energy compared with other systems. Therefore, it is suggested that NADES(Bet-MA)/GG could serve as a new and environmentally friendly Cur loading system, with potential application prospects in edible packaging and functional foods.