Stage-adaptive nanotherapeutic design for blood-brain barrier navigation in ischemic stroke.

Ischemic stroke remains one of the leading causes of mortality and long-term disability worldwide, yet effective pharmacological intervention is profoundly limited by the blood-brain barrier (BBB). As a highly selective and dynamically regulated interface, the BBB preserves neural homeostasis but simultaneously restricts the delivery of most neuroprotective agents. Nanomedicine has emerged as a promising approach to overcome this obstacle. However, many existing strategies remain largely decoupled from the evolving pathological landscape of the ischemic brain. This review presents a mechanism-driven framework for BBB navigation that explicitly integrates nanocarrier design with the spatiotemporal progression of ischemic pathology. The dynamic remodeling of the BBB is first outlined across distinct stages, from the hyperacute phase with largely intact barrier function, through acute disruption, to the subsequent repair phase. Building on this foundation, we analyze advanced delivery strategies that enable brain entry under these varying conditions, including receptor-mediated transcytosis (RMT), biomimetic transport via immune cell-inspired systems, and pharmacological or physical BBB modulation. Particular attention is given to stimuli-responsive nanocarriers that leverage pathological cues within the ischemic microenvironment-such as oxidative stress, acidosis, and enzyme activation-to achieve localized and on-demand drug release. Therapeutic effects are further discussed from a neurovascular unit (NVU) perspective, highlighting coordinated modulation of oxidative damage, inflammatory responses, neuronal survival, and vascular remodeling. Translational barriers remain substantial. Biological heterogeneity, limitations of current animal models, and the growing complexity of nanocarrier design continue to impede clinical progress. By linking BBB dynamics with engineering strategies and therapeutic mechanisms, this review provides a conceptual framework for the development of stage-adaptive and clinically translatable nanomedicine for ischemic stroke.