Design and investigation of nanoemulsified carrier based on amphiphile-modified hyaluronic acid

Hyaluronic acid (HA) was modified into an amphiphile through esterification between the carboxyl and hydroxyl moieties on glycerol-α-monostearate (GMS). The conjugation was verified via FT/IR and 1H NMR. Ultrasonification and solvent evaporation were used to prepare a fine oil/water/surfactant (O/W/S) nanoemulsion consisting of methylene chloride as the oil phase (O), HA water solution (W), and non-ionic Tween-80 and Span-20 as surfactant (S). The optimal ratio of the disperse phase was screened in nanoemulsion formed without HA-GMS. Tween-80 and Span-20 at the required hydrophilic–lipophilic balance (HLB) of 12.5 and a ratio of O/S (ROS) of 60, which accounted for 5% (w/w) in the emulsion system, was determined to be the optimal disperse phase ratio, giving rise to the smallest droplet size (39.7 nm) and lower protein dispersibility (0.341). The smallest droplet size of the HA-GMS nanoemulsion was 42.0 nm, with contraction to 38.9 nm evident after 96 h storage. Higher degree of substitution or lower molecular weight was favorable for the formation of smaller emulsified droplets. Nanoemulsions were characterized morphologically by electronic microscopy.