Development of acetylated inulin microparticles via coaxial electrospraying for enhanced intestinal delivery and probiotic protection of Lactobacillus reuteri

Abstract

Probiotic therapy provides clinical potential for systemic health, but its therapeutic efficacy is limited by low bioavailability in the harsh gastrointestinal environment. Natural polysaccharides, such as inulin, are promising candidates for bioactive delivery; however, they easily dissolve in water and rapidly break down under acidic conditions, limiting their function as protective materials. In this study, we applied chemical modification to create a stable, acid-resistant inulin shell to protect probiotics from the gastric environment and to improve their stability during gastrointestinal transit. We prepared acetylated inulin (In–Ac) through a controlled esterification process, verifying its molecular structure by 1H nuclear magnetic resonance (NMR), Fourier transform infrared spectroscopy, and X-ray diffraction. NMR analysis confirmed successful synthesis with a high degree of acetyl substitution (79.7% ± 3.0%). Using a coaxial electrospraying system, we encapsulated Lactobacillus reuteri within these In–Ac shells. An optimized coaxial electrospraying process using a 30% (w/v) shell solution produced well-defined spherical microparticles with an average diameter of 5.62 ± 2.13 µm. The In–Ac matrix exhibited good structural integrity under acidic conditions (pH 3.0), indicating resistance against acid-induced degradation. In HuH-6 and Caco-2 cell models, the material demonstrated excellent biocompatibility, with no significant toxicity at relevant concentrations; moreover, in an in vivo mouse model, the In–Ac matrix exhibited improved probiotic stability and delivery efficiency under physiological conditions. Overall, these findings reveal that In–Ac-based microparticles fabricated via electrospraying provide a stable, biocompatible delivery platform that effectively protects probiotics during gastrointestinal transit, offering a promising platform for enhanced intestinal delivery and probiotic protection.