Structural design and delivery performance of resistant starch-containing delivery systems: A comprehensive review from material fundamentals to colon-targeted applications.

Resistant starch (RS) is a dietary fiber that escapes small-intestinal digestion and reaches the colon, offering inherent colon-targeting potential, bioactive protection, and prebiotic benefits. However, native RS often shows limited mechanical strength and high hydrophilicity, driving the development of modified and composite delivery systems. This review summarizes the functional advantages of RS and evaluates representative RS-containing delivery systems according to carrier architecture and the functional role of RS, including particulate carriers, Pickering emulsions, hydrogels, nanoparticles, film-coated microparticles, and emerging three-dimensional (3D) printed matrices. Particular attention is given to how RS type (RS1-RS5), crystallinity, amylose/amylopectin ratio, chemical modification, particle structure, processing parameters, and environmental conditions influence encapsulation efficiency, gastrointestinal stability, and release behavior. RS-containing systems can protect sensitive bioactive compounds and probiotics during upper-gastrointestinal transit and support colon-region release through hydration, molecular diffusion, matrix erosion, and microbiota-mediated degradation. Remaining challenges include thermal sensitivity, mechanical damage, batch uniformity, limited in vivo validation, incomplete understanding of microbiota-dependent behavior, and insufficient integration of in vitro release with biodistribution, bioavailability, metabolism, and clinical outcomes. By linking RS structural hierarchy and functional location within carriers to processing-induced microstructure and gastrointestinal transformation, this review provides a mechanistic basis for designing RS-containing systems with improved encapsulation efficiency, upper-gastrointestinal protection, and controlled colon-region release.