Introduction: Although oral administration of Bifidobacterium  is a promising approach for diseases, lack of resistance to harsh conditions and real-time tracking in gastrointestinal system in vivo are still major challenges in basic research and clinical applications. 
Materials and methods: In this study, we fabricated a chitosan-coated alginate microcapsule loaded with in situ synthesized barium sulfate (CA/BaSO₄ microcapsule) for oral Bifidobacterium  delivery and real-time X-ray computed tomography (CT) imaging. CA/BaSO₄ microcapsules containing the Bifidobacterium  were prepared in situ by one-step electrostatic spraying method, and then coated with chitosan. 
Results: The results indicated that CA/BaSO₄ microcapsules with an average diameter of approximately 200 µm possessed favorable mechanical stability and X-ray attenuation capacity. Encapsulation of Bifidobacteria  in the CA/BaSO₄ microcapsules exhibited superior resistance to cryopreservation and gastric acid environment in vitro. After oral administration in mice, these CA/BaSO₄ microcapsules could be real-time visualized by CT imaging and readily reached the intestine to release Bifidobacteria .
Conclusion: The radiopaque CA/BaSO₄ microcapsules provide a novel platform for efficient protection, non-invasive real-time monitoring and intestinal-targeted Bifidobacterium  delivery.
Keywords: alginate, microcapsule, CT imaging, intestinal-targeted, Bifidobacterium