Preparation and characterization of rifampicin-PLGA microspheres/sodium alginate in situ gel combination delivery system

► We used PLGA microspheres as the first-level drug carrier, in situ gel-alginate sodium was used as the second-level carrier. ► Drug can be slowly released from microspheres while in situ gel can help microspheres adhere to the targeted tissue. ► In vivo imaging system was used in this study to evaluate the retention property of our complex system.