A hierarchical MgF2/polyurethane/pitavastatin coating alleviates degradation and enhances endothelialization of bioresorbable magnesium alloy stents

Abstract

Rare-earth-free magnesium (Mg) alloy bioresorbable stent (BRS) exhibits significant potential in vascular intervention due to its exceptional biosafety. However, its susceptibility to corrosion complicates surface functionalization and renders existing coating strategies ineffective for degradation-remodeling kinetics, resulting in delayed re-endothelialization and excessive lumen loss. Herein, a hierarchical MgF₂/polyurethane (PU)/pitavastatin (PTV) coating system is constructed on Mg-Zn-Mn BRS using elastomeric PU as an intermediate layer. Studies confirm the PU layer effectively accommodates stent deformation, alleviates stress concentrations, and confines corrosion propagation triggered by deformation-induced MgF₂ microcracks. The in situ formed MgF₂ layer concurrently decreases substrate reactivity, establishes stable interfaces with PU, and synergistically enhances the corrosion resistance. The surface PTV-loaded poly-L-lactic acid layer maintains sustained drug release through PU-mediated interfacial stability while serving as an initial corrosion barrier. In vivo evaluations demonstrate the MgF₂/PU/PTV-functionalized stent significantly suppresses neointimal hyperplasia in rabbit models while achieving synchronized degradation-remodeling kinetics. This hierarchical coating architecture, which synergistically integrates controlled drug elution with degradation modulation, provides a viable solution to clinical challenges of post-implant restenosis and vascular remodeling mismatch.