Development of probiotic microencapsulated Limosilactobacillus reuteri films using mucoadhesive polymers as a delivery system – strategies to improve bacterial viability

Abstract

Dysbiosis, an imbalance within the oral microbiome, is associated with several diseases, particularly periodontitis, which is characterized by a transition towards Gram-negative bacteria. Conventional treatments, including antibiotics and surgery, have limitations, which have led to an exploration of alternative methods. The application of probiotic bacteria to restore a balanced microbiome is such a minimally invasive alternative. In practice, the use of probiotic bacteria is hampered by the insufficient survival rate of the bacteria in the formulations. Using Limosilactobacillus strains as an example, this study addresses these challenges and discusses three concrete measures to extend the duration of the bacterial viability. First, bacterial cultures were exposed to stress inducers during cultivation, such as osmotic stress or acidic pH, to induce protective physiological responses and enhance resilience. Next, the probiotic bacteria were microencapsulated via spray-drying with Eudragit® EPO & RL30D. Besides the protective effects, the aim of microencapsulation is to ensure the gradual release of the bacteria, i.e. Limosilactobacillus reuteri (formerly known as Lactobacillus reuteri). Finally, films comprising mucoadhesive polymers were created with the objective of prolonging the residence of bacteria in the oral cavity through mucoadhesive interactions and rendering the bacteria in a form that is suitable for application. Our research underscores the significance of cultivation conditions in improving bacterial survival in subsequent formulation steps. We confirm the efficacy of microencapsulation of L. reuteri through spray-drying. Its success is evidenced by the controlled release identified during the dissolution process. A suitable method for the production of mucoadhesive polymer films is described. Encountered challenges when embedding microencapsulated bacteria in polymer films are discussed and a set of conditions, including growth phase, pH, and osmotic stress, was evaluated to identify factors influencing survival. In summary, the results enhance the progress of focused measures for preserving dental health, highlighting the capability of mucoadhesive polymer films as delivery vehicles for microencapsulated probiotic bacteria.