Nitric Oxide Uncaging from a Hydrophobic Chromium(III) PhotoNORM: Visible and Near-Infrared Photochemistry in Biocompatible Polymer Disks

Devices
consisting of polymer disks (PDs) of optically clear or
translucent, medical-grade silicone loaded with a new hydrophobic,
oxygen-stable, photoactivated nitric oxide-releasing moiety (photoNORM)
are described. The photoNORM is the new O-nitrito
chromium­(III) complex trans-[Cr­(PetA)­(ONO)2]­(BF4) (PetA = 5,14-dimethyl-7,12-diphenyl-1,4,8,11-tetraaza-cyclotetradecane),
of which the synthesis, X-ray crystal structure, and solution-phase
photochemistry are described. Several different commercially available
silicone polymers were tested with this photoNORM, and nitric oxide
photouncaging with 451 nm light from these systems is compared. In
addition, PDs were loaded with the photoNORM and neodymium-sensitized
upconverting nanoparticles (Nd-UCNPs). The Nd-UCNPs absorb NIR light
at ∼800 nm and activate NO release from the trans-[Cr­(PetA)­(ONO)2]+ cation. The use of such ensembles
as implants provides a potential strategy for the in vivo uncaging
of NO at physiological targets triggered by tissue-transmitting NIR
excitation. Also reported are the X-ray crystal structures of cis- and trans-{Cr­(PetA)­Cl2]­Cl.