ZIF-8 Film Coatings Render Polymeric Device Surfaces Addressable by ¹H/¹²⁹Xe MRI

Metal-organic framework (MOF) films synergize molecular-scale porosity with conformal surface chemistry on polymer substrates. We report a spectrally selective coating in which a ZIF-8 film, seeded by a Zn(II)-polydopamine (Zn-PDA) interlayer on polytetrafluoroethylene (PTFE), enables hyperpolarized ^{1 2 9}Xe MRI detection of the polymer surface, while conventional ¹H MRI delineates anatomy. The coating produces a film-bound ^{1 2 9}Xe resonance at 82.0 ppm in both water and fetal bovine serum. After 60 min, the resonance position remained unchanged, with signal-to-noise ratios decreasing by only 14.9% and 17.2%, respectively. Selective excitation yields coating-specific positive contrast on the ^{1 2 9}Xe channel; correspondingly, ¹H MRI reveals a distinct surface appearance likely due to altered local proton density and magnetic susceptibility. In phantoms, ^{1 2 9}Xe and ¹H images were co-registered with a center-point offset of 0.34 mm; in a flow simulator, the offset was 0.26 mm. A rat airway experiment confirmed in vivo spectral selectivity with a film-bound resonance near 92 ppm, co-localizing with ^{1 2 9}Xe ventilation and ¹H anatomical references. While demonstrated here using coated PTFE segments and direct xenon bubbling, these results provide a robust proof of concept for MOF-coated polymers as spectrally selective ^{1 2 9}Xe MRI labels, warranting future physiological translation.