A pH-Responsive Gel Macrosphere Based on Sodium Alginate and Cellulose Nanofiber for Potential Intestinal Delivery of Probiotics

Intestinal delivery of probiotics to modulate microbiome compositions has potential effects on the treatment of plenty of human diseases. However, the gastric acid in the stomach can greatly reduce the number of viable probiotics that reach the intestine. Here, sodium alginate/cellulose nanofiber gel macrospheres (ACMs) were fabricated by extruding a mixture of sodium alginate (SA) and TEMPO-oxidized cellulose nanofiber (CNF) into CaCl2 solutions for cross-linking. These gel macrospheres were evaluated as capsules for the encapsulation of probiotics. The structure of ACMs was studied by Fourier-transform infrared spectroscopy (FTIR) and X-ray diffractometry (XRD). The thermal properties, morphological properties, swelling properties, and cell viability of ACMs were also investigated. Moreover, the proliferation of probiotics in ACMs and in vitro release of probiotics from ACMs were evaluated. The results show that ACMs are stabilized in simulated gastric fluid, ensuring better protection of encapsulated probiotics in acidic environment. On the contrary, they will swell in simulated intestinal fluid, contributing to the release of encapsulated probiotics. The pH-responsive property of ACMs make them available to protect probiotics in simulated gastric fluids as well as release probiotics in simulated intestinal fluids, indicating potential application for intestinal-targeted delivery of probiotics.