Abstract

DEVELOPMENT AND CHARACTERIZATION OF CAPRYLATE–CHITOSAN/ALGINATE-BASED MUCOADHESIVE MICROSPHERES FOR SUSTAINED ORAL DELIVERY OF DIPHTHERIA AND TETANUS TOXOIDS

Vaishali S. Raundal*, Sapana V. Khonde, Vasant B. Kadam

ABSTRACT

The present study describes the formulation, characterization, and evaluation of a dual-toxoid-loaded mucoadhesive microparticulate system based on caprylate-substituted chitosan and sodium alginate for sustained oral vaccine delivery. The microspheres were prepared by coacervation and polyelectrolyte complexation using low-molecular-weight water-soluble chitosan, sodium alginate, sodium caprylate, and cetyl trimethyl ammonium bromide (CTAB). Diphtheria toxoid (DT) and tetanus toxoid (TT) were encapsulated with the aim of achieving prolonged antigen release, protection from gastrointestinal degradation, and enhanced mucosal immunogenicity. Physicochemical characterization included Fourier Transform Infrared Spectroscopy (FT-IR), Field Emission Scanning Electron Microscopy (FE-SEM), and Energy-Dispersive X-ray Spectroscopy (EDS). Entrapment efficiency, loading capacity, swelling index, and in-vitro releasekinetics were determined. The optimized formulation exhibited high antigen entrapment (above 90%), a minimal initial burst (12%), and sustained release for up to 19 days. Kinetic modeling indicated non-Fickian diffusion for DT release and relaxation-controlled release for TT. EDS confirmed the presence and subsequent loss of nitrogen and sodium from the microspheres, consistent with degradation and release. The findings demonstrate that CTAB and caprylate-substituted chitosan/alginate microspheres provide a promising oral vaccine delivery platform with improved stability, bioadhesion, and controlled antigen release.

Keywords: Chitosan, Sodium Alginate, Caprylate, CTAB, Mucoadhesive Microspheres, Oral Vaccine Delivery, Diphtheria Toxoid, Tetanus Toxoid, Sustained Release.