Disposable Nitric Oxide Generator Based on a Structurally Deformed Nitrite-Type Layered Double Hydroxide

The inhalation of nitric oxide (NO), which acts as a selective vasodilator of pulmonary blood vessels, is an established medical treatment. However, its wide adoption has been limited by the lack of a convenient delivery technique of this unstable gas. Here we report that a solid mixture of Fe^IISO₄·7H₂O and a layered double hydroxide (LDH) containing nitrite (NO₂^-) in the interlayer spaces (NLDH) stably generates NO at a therapeutic level (∼40 ppm over 12 h from freshly mixed solids; ∼80 ppm for 5-10 h from premixed solids) under air flow (0.25 L min^-1) if the NLDH has been prepared by using a reconstruction method. Mg/Al-type LDH was calcined at 550 °C to remove interlayer CO₃^2- and then treated with NaNO₂ in water to reconstruct the NLDH. This one-pot, organic solvent-free process can be performed at large scales and is suitable for mass production. Humid air promotes anion exchange between NO₂^- and SO₄^2- in the solid mixture, resulting in persistent interactions of NO₂^- and Fe²⁺, generating NO. In contrast to the previously reported NLDH prepared using an anion-exchange method, the reconstructed NLDH exhibits stable and persistent generation of NO because of partial deformation of the layered structures (e.g., particle aggregation, reduced crystallinity, and enhanced basicity). Degradation of the solid mixture is suppressed under dry conditions, so that a portable cartridge column that is readily available as an NO source for emergency situations can be prepared. This work demonstrates that the interlayer nanospace of LDH serves as a reaction mediator for excellent controllability of solid-state reactions. This inexpensive and disposable NO generator will facilitate NO inhalation therapy in developing countries and nonhospital locations.