Nano-carriers (NCs) provide drugs with protective and oriented strategies. Despite their success in parenteral administration, NCs still need to be optimized to meet the more serious obstacles encountered in the gastrointestinal tract (GIT). The main defense mechanisms include renewing mucus, epithelial obstacles and digestion by GIT segments. These hurdles pose challenges even before NCs target molecules or proteins, which has often led to unsatisfactory delivery efficiency. Therefore, a critical focus is the exemption from negative effects of GIT. A series of adapted NCs have been designed based on surface strategies to form an expected distribution and increase gastrointestinal utilization. In this paper, we review the strategies and efforts of NCs to adapt to gastrointestinal defense components, including the mucus, epithelium and gastrointestinal segments; the related gastrointestinal mechanisms and functions are also summarized synchronously. Last, we discuss the delivery challenges in terms of physiopathological GIT and surface properties of the NCs.

纳米载体（NCs）为药物提供了保护性和针对性的策略。尽管在肠胃外给药方面取得了成功，但NC仍需要进行优化，以克服胃肠道（GIT）遇到的更严重的障碍。主要防御机制包括更新粘液，上皮障碍和GIT片段的消化。这些障碍甚至在NCs靶向分子或蛋白质之前就构成了挑战，这通常导致递送效率不令人满意。因此，一个关键的重点是避免GIT的负面影响。已经根据表面策略设计了一系列适应性NC，以形成预期的分布并提高胃肠道利用率。在本文中，我们回顾了NCs适应胃肠道防御组件（包括粘液，上皮和胃肠段；同步总结了相关的胃肠道机制和功能。最后，我们从生理病理学GIT和NC的表面特性方面讨论了传递方面的挑战。