Mucoadhesive Biopolymer Nanoparticles for Encapsulation of Lipophilic Nutrients With Enhanced Bioactivity

Biopolymer-based nanoparticles, prepared from stearic acid-chitosan derivative, sodium caseinate (NaCas) and oxidized dextran (Odex), have been shown to have high biocompatibility and exceptional gastrointestinal (GI) stability. However, the mucoadhesive properties of such nanoparticles have yet to be analyzed. Therefore, interactions between the nanoparticles and mucin, the major protein of the mucus layer, were evaluated through rheological studies, quartz crystal microbalance with dissipation (QCM-D) analysis, and adsorption testing. There was an increase in the elastic and viscous properties of mucin when complexed with the nanoparticles during the frequency sweep, denoting rheological synergism. The nanoparticles exhibited rapid decreases in frequency and increases in dissipation during the QCM-D analysis, denoting successful adsorption onto the mucin layer. Following adsorption testing, peak adsorption (91 %) was found to be at a ratio of 1:4 at mucin/nanoparticles (weight/weight). Once the role of the nanoparticles’ mucoadhesive properties in GI stability was determined, astaxanthin (ASTX) was utilized as a model nutrient for enhanced bioavailability via encapsulation. The effect of encapsulation on ASTX was determined through measuring particulate properties. Encapsulated ASTX exhibited enhanced antioxidant activity compared to free ASTX in ABTS and DPPH antioxidant assays. This study suggests that the as-prepared biopolymer nanoparticles exhibit mucoadhesive properties that could beneficially interact with the mucus layer of the GI tract. Given their enhanced mucoadhesive properties, the nanoparticles make an excellent candidate for the encapsulation of nutrients with low bioavailability such as the lipophilic ASTX.