Bioadhesive Alginate/Chitosan Hydrogels for Sustained Probiotic Delivery and Enhanced Antibacterial Treatment of Oral Ulcers

Recurrent aphthous ulcers (RAU) are highly prevalent oral mucosal lesions, while current therapies are limited by short residence time and poor efficacy in the dynamic oral environment. Probiotics such as Lactobacillus reuteri (L. reuteri) exhibit antimicrobial, immunomodulatory, and tissue-repair functions; however, their direct application is restricted by low stability and retention in the oral cavity. In this study, L. reuteri-loaded sodium alginate/chitosan composite hydrogels were developed via ionic crosslinking as a bioadhesive platform for local delivery. The hydrogels exhibited well-defined porous structures, favorable viscoelastic properties, and tunable swelling and degradation behaviors under simulated physiological conditions. Importantly, the system enabled sustained probiotic release and maintained high viability during 30 days of storage. In vitro antibacterial assays demonstrated that the hydrogels effectively inhibited the growth of Staphylococcus aureus and Candida albicans. Among the formulations, the hydrogel with 10 mg·mL−1 chitosan achieved an optimal balance between structural stability and mass transfer, resulting in enhanced release performance and antibacterial efficacy. Overall, this study presents a microecology-oriented hydrogel system for efficient probiotic delivery in oral environments, offering a promising bioadhesive probiotic delivery platform with potential applications in RAU management and advancing the development of bioactive, mucosa-adaptive therapeutic platforms.