Avoiding ischemic necrosis after flap transplantation remains a significant clinical challenge. Developing an effective pretreatment method to promote flap survival postoperatively is crucial. Cobalt chloride (CoCl₂) can increase cell tolerance to ischemia and hypoxia condition by stimulating hypoxia-inducible factor-1 (HIF-1) expression. However, the considerable toxic effects severely limit the clinical application of CoCl₂. In this study, cobalt-based metal-organic frameworks (Co-MOF) encapsulated in a microneedle patch (Co-MOF@MN) was developed to facilitate the transdermal sustained release of Co²⁺ for rapid, minimally invasive rapid pretreatment of flap transplantation. The MN patch was composed of a fully methanol-based two-component cross-linked polymer formula, with a pyramid structure and high mechanical strength, which satisfied the purpose of penetrating the skin stratum corneum of rat back to achieve subcutaneous vascular area administration. Benefiting from the water-triggered disintegration of Co-MOF and the transdermal delivery via the MN patch, preoperative damage and side effects were effectively mitigated. Moreover, in both the oxygen-glucose deprivation/recovery (OGD/R) cell model and the rat dorsal perforator flap model, Co-MOF@MN activated the HIF-1α pathway and its associated downstream proteins, which reduced reperfusion oxidative damage, improved blood supply in choke areas, and increased flap survival rates post-transplantation. This preprotection strategy, combining MOF nanoparticles and the MN patch, meets the clinical demands for trauma minimization and uniform administration in flap transplantation. STATEMENT OF SIGNIFICANCE: Cobalt chloride (CoCl₂) can stimulate the expression of hypoxia-inducible factor (HIF-1) and improve the tolerance of cells to ischemia and hypoxia conditions. However, the toxicity and narrow therapeutic window of CoCl₂ severely limit its clinical application. Herein, we explored the role of Co-MOF as a biocompatible nanocage for sustained release of Co²⁺, showing the protective effect on vascular endothelial cells in the stress model of oxygen-glucose deprivation. To fit the clinical needs of minimal trauma in flap transplantation, a Co-MOF@MN system was developed to achieve local transdermal delivery at the choke area, significantly improving blood supply opening and flap survival rate. This strategy of two-step delivery of Co²⁺ realized the enhancement of biological functions while ensuring the biosafety.

#	Concept	H-Index	Publications	Citations
1	Medicine	7	7	369
2	Pharmacology	5	5	271
3	Microbiology	2	2	96
4	Immunology	1	1	35
5	Pathogenesis	1	1	35

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