Bacterial extracellular vesicles: mechanisms, engineering strategies, and therapeutic potential for inflammatory bowel disease.

Clinical management of inflammatory bowel disease (IBD) is hampered by limited therapeutic targets, primary non-response, secondary loss of efficacy, and safety risks, which undermine clinical outcomes. Probiotics and postbiotics represent promising preclinical candidates to alleviate these unmet clinical bottlenecks. Bacterial extracellular vesicles (BEVs) are naturally secreted bacterial nanovesicles carrying abundant bioactive cargos, whose bioactivity and safety are highly strain-dependent. Probiotics-derived BEVs can remodel gut homeostasis, repair epithelial barriers, and regulate mucosal immunity to suppress the inflammatory vicious cycle in IBD, while pathogen-/pathobiont-derived BEVs loaded with lipopolysaccharide and virulence factors exacerbate intestinal inflammation. Native BEVs are restricted by low cargo loading, poor gastrointestinal stability and inadequate colon tropism. Rational engineering strategies, including surface modification, self-loading hybridization, genetic manipulation, and pH-responsive coating, can optimize the therapeutic performance of BEVs. This review systematically summarizes BEVs biological mechanisms, engineering approaches, and translational obstacles and outlines prospects for the design of intelligent multifunctional BEVs and standardized large-scale manufacturing as future directions, providing theoretical support for oral BEVs nanotherapies against IBD.