Ultrasonic fabrication of polysaccharide capsules: Unraveling the xanthan gum-chitosan shell formation mechanism

Aim

This study establishes the mechanism of stable emulsion capsules formation using sulfhydryl-free polysaccharides (xanthan gum, chitosan, and their mixtures), comparing ultrasonic versus conventional mechanical preparation methods.

Methods

Capsules were fabricated using both mechanical and ultrasonic processing, followed by comprehensive characterization through DLS, CLSM, CRYO electron microscopies, XPS, FTIR, AFM, XRD, and TGA.

Results

Ultrasonically processed xanthan gum/chitosan capsules exhibit a well-defined morphology (1 μm average size), stable surface characteristics (−19 mV zeta potential), and enhanced resistance to aggregation and coalescence. The results demonstrate not only formation of polyelectrolyte complexes in the mixed shells (with xanthan gum/chitosan ratios of 1 and 1.17 for mechanically and ultrasonically prepared capsules, respectively, with an initial 1:1 polymer solution ratio), but also reveals molecular scissoring effects. Structural characterization reveals semi-crystalline shell organization with significantly improved mechanical strength, as evidenced by the 48 kPa Young's modulus. The capsules exhibit excellent hemocompatibility (hemolysis rate < 0.02 μL/mL) for intravenous delivery applications.

Conclusion

Our findings reveal fundamental insights into polysaccharide behavior on the phase interface under ultrasonication, demonstrating how acoustic energy drives molecular reorganization to create structurally superior capsules. This work provides a new paradigm for polysaccharide-based drug carrier design to create high-performance delivery systems with enhanced stability.