Alginate functionalized chitosan nanoparticles using multilayer co-axial electro-spraying for ovalbumin controlled release via oral delivery

Abstract

The current oral vaccine delivery presents numerous challenges due to physiological barriers in the gastrointestinal tract including antigen degradation by enzymes and gastric pH conditions. Contributing to overcome these problems, this work developed non-cross-linked chitosan (CHI) nanoparticles, with/without functionalization with alginate (ALG), using multilayer co-axial electro-spraying method, to orally deliver ovalbumin (OVA), a model antigen. The prepared OVA@CHI and OVA@CHI@ALG nanoparticles possessed spherical shape, uniform size and non-agglomeration, high OVA encapsulation efficiency of above 90 %, and core-shell structure with mean diameters of 276.9 ± 70.7 nm (for OVA@CHI) and 304.3 ± 63.9 nm (for OVA@CHI@ALG), determined via SEM images. The particle hydrodynamic diameters, analyzed by the DLS method, were 313.0 ± 72.4 nm for OVA@CHI and 367.6 ± 83.2 nm for OVA@CHI@ALG, in agreement with the SEM results. Additionally, the material functional group interactions and the polyelectrolyte complex formations were confirmed by FTIR spectra and TGA/DSC thermo-grams, indicating the successful formulation. Subsequently, the OVA@CHI@ALG nanoparticles revealed good stability in acidic environment under the presence of digestive enzymes. The OVA release profiles of OVA@CHI@ALG nanoparticles exhibited limited release in simulated gastric fluid (pH 1.2), followed by sustained release in simulated intestinal fluid (pH 6.8) and simulated colonic fluid (pH 7.4) over a 48-h test period. Interestingly, the primary structure of OVA, analyzed by SDS-PAGE analysis, was maintained during the preparation process and after the release test, while the OVA secondary structure, examined by circular dichroism measurement, demonstrated a decrease of α-helix and an increase of β-sheet contents. Finally, the in vitro mucin-binding study indicated a significant adhesive efficiency of 69.21 ± 4.24 % for OVA@CHI and 75.07 ± 2.58 % for OVA@CHI@ALG at pH 7.4. Conclusively, the OVA@CHI@ALG nanoparticles fabricated by tri-axial electro-spraying method could be a promising oral vaccine delivery system for sustained release of OVA.