Xanthan-based nanocomplexes: modulating colloidal properties, model compound encapsulation and mucoadhesion via...

Xanthan gum (XG) and diethylaminoethyl dextran (DD) electrostatic nanocomplexes (NCs) are prepared at the native (NCs) and thermally denatured state of XG (den-NCs). Dynamic and static light scattering (DLS and SLS) and transmission electron microscopy (TEM) reveal well-defined, spherical NCs with mean hydrodynamic and gyroscopic radii of 100-200 nm at charge ratios (ratio of anionic XG to cationic DD monomers) between 0.4 and 5. Their size increases at CR > 1 possibly due to XG-XG double helix formation. Surface potential shifts from positive to negative between CR 1 and 1.25, suggesting stoichiometric neutralization. NCs remain stable for over one month without significant aggregation. Fluorescence measurements with pyrene and 8-Anilino-1-naphthalenesulfonate (ANS) indicate the presence of hydrophobic domains inside the NCs attributed to DD's ethyl groups, which renders them suitable for the encapsulation of hydrophobic compounds. High loading efficiency (∼48 %) and loading capacity (∼19 %) for β-carotene (β-C) is found for native NCs at CR 0.4 and 2.5, whereas den-NCs show significantly lower encapsulation. NCs interact with porcine gastric mucin (PGM) in PGM solutions as it is confirmed by NC-PGM aggregation. Mucoadhesion is also examined with mucus-mimicking PGM-immobilized alginate beads. Positively charged NCs exhibit enhanced mucoadhesion relative to negatively charged ones. Overall, XG/DD NCs display tunable properties promising for drug delivery applications with notable stability, encapsulation and mucoadhesive capabilities.