Biomimetic delivery systems for overcoming drug resistance in gastrointestinal cancers.

Gastrointestinal (GI) cancers remain a major cause of cancer-related mortality worldwide, and multidrug resistance (MDR) is a critical barrier to durable therapeutic response. In GI malignancies, MDR arises from multilayered and interdependent factors, including insufficient intracellular drug accumulation, altered drug activation and metabolic detoxification, target rewiring and phenotypic plasticity, apoptosis-autophagy-mediated stress adaptation, and extrinsic protection from the tumor microenvironment, cancer stem cells, metastatic niches, and microbiome-associated mechanisms. Biomimetic delivery systems (BDSs), including cell membrane-coated nanocarriers, extracellular vesicles, and living or virus-mediated platforms, provide biological interface functions that may improve drug circulation, tumor recognition, tissue penetration, membrane interaction, and active trafficking. However, their therapeutic value in MDR GI cancers should not be judged merely by improved delivery efficiency, but by whether they address defined resistance bottlenecks and generate evidence of genuine re-sensitization in resistant disease contexts. Current evidence indicates that many BDSs remain at the level of exposure enhancement or mechanism-aligned sensitization, whereas only a limited subset has demonstrated functional restoration of treatment response in established resistant models. This review organizes current BDS strategies according to their dominant mechanistic functions: enhancing drug accumulation and intratumoral delivery, reversing cellular drug resistance, remodeling resistance-supportive tumor microenvironment, targeting cancer stem cells (CSCs) and metastatic niches, and enabling site-directed intervention using living carriers and living therapeutics. By linking GI cancer-focused MDR biology to function-oriented biomimetic design, this review establishes an evidence-based framework for distinguishing delivery enhancement from true MDR reversal and outlines platform-specific requirements for clinical translation.