Construction of anisotropic cellulose roll capsules via directional freeze casting for pH-responsive probiotic...

Probiotics offer diverse health benefits, but their efficacy is compromised by gastrointestinal stress and burst release in conventional encapsulation systems, limiting the efficacy of probiotics in functional foods. Herein, an alginate-coated cellulose roll capsule with anisotropic porous structures and sustained release property was developed via a combined strategy of directional freeze casting and ethanol coagulation bath, which avoids the need for energy-intensive freeze-drying. The pH-responsive alginate shell and layered cellulose roll core synergistically blocked acidic penetration and enhanced probiotic survival in the gastric environment, while the gradual dissolution of alginate shell and unfolding of cellulose roll led to controlled release of probiotics from the aligned microchannels in the intestinal environment. The design endowed the capsule with excellent survival rate (91.03%), high release count (1.82 × 10⁸ CFU), prolonged release duration (9 h) and zero-order release kinetics. This study is based on in vitro simulated digestion using a single probiotic strain, and future work will address in vivo validation with additional probiotic species. This bioinspired system provides a strategy for functional food delivery by addressing the burst release challenge of probiotic encapsulation.