Magnetically targeted delivery of probiotics for controlled residence and accumulation in the intestine†

The effectiveness of orally delivered probiotics in treating gastrointestinal diseases is restricted by inadequate gut retention. In this study, we present a magnetically controlled strategy for probiotic delivery, which enables controlled accumulation and residence of probiotics in the intestine. The magnetically controlled probiotic is established by attaching amino-modified iron oxide (Fe₃O₄–NH₃⁺ NPs) to polydopamine-coated Lacticaseibacillus rhamnosus GG (LGG@P) through electrostatic self-assembly and named as LGG@P@Fe₃O₄. In a simulated gastrointestinal environment, LGG@P@Fe₃O₄ maintains both structural stability and probiotic viability. Furthermore, the LGG@P@Fe₃O₄ clusters can be easily manipulated by an external magnetic field, inducing directional movement and aggregation. In vitro simulations demonstrated significant accumulation and retention of LGG@P@Fe₃O₄ under a magnetic field, with the optical density (OD) value of the suspension decreasing from ∼1.17 to ∼0.29. In contrast, the OD value of the suspension without a magnetic field remained at its original level (∼1.15). In a mouse model with intragastrically administered LGG@P@Fe₃O₄, the group exposed to a magnet exhibited stronger gut fluorescence after 24 h. The magnetically controlled probiotic delivery strategy offers an easy manufacturing and feasible method to enhance the effectiveness of probiotics in treating gastrointestinal diseases.