Ferrocene-Functionalized Black Phosphorus Nanoplatform Enables Targeted and Prolonged MRI Visualization of Atherosclerotic Plaques.

Despite the critical role of contrast-enhanced magnetic resonance imaging (MRI) in clinical diagnostics, current contrast agents face dual challenges: metallic formulations provoke biosafety concerns while organic radicals exhibit transient imaging windows. To overcome these limitations, a radical-engineered 2D black phosphorus (2D BP) nanoplatform is reported through atomic-scale conjugation of aminoferrocene, creating a stable complex with enhanced electron spin resonance, named FcP. The covalent coupling strategy establishes persistent T2-weighted contrast capability. Subsequent hyaluronic acid (HA) functionalization endows the HA-FcP system with CD44-specific targeting, achieving 1.7-fold higher plaque accumulation than non-targeted counterparts in apolipoprotein E-deficient models. Remarkably, this nanostructure enables continuous MRI visualization of atherosclerotic lesions for 120 h post-injection. Systematic biosafety evaluation demonstrates >90% cell viability and normal hematological parameters. This work pioneers a new paradigm for MRI contrast agents through spin state manipulation of 2D materials, providing a translational platform for precision cardiovascular diagnostics.