Confined Micellar Environments Modulate Thiol Reactivity and Nitrite Release From 4-Nitronaphthalimide Nitric Oxide...

Nitric oxide (NO) is a key signaling molecule in human physiology, and its controlled delivery from small-molecule prodrugs remains a major challenge. 4-Nitronaphthalimides (4-NNs) have recently been identified as glutathione (GSH)-mediated nitrite (NO2^-) donor prodrugs, with accelerated release observed in cellular compared to cell-free environments. We hypothesized that confined reaction spaces play a crucial role in this reactivity. Here we show that micelles, as cellular confinement mimics, markedly influence the thiol-mediated nitrite release from 4-NNs. Systematic studies under micellar and non-micellar conditions, with varied surfactants, thiols, and pH, reveal that confined microenvironments and the nature of micellar assemblies critically control reaction rates. Confocal fluorescence and lifetime imaging visualized micelle localization and reactivity differences, while DOSY-NMR, DLS, and zeta potential measurements established that 4-NNs reside in the palisade layer of cationic micelles, rendering them accessible to thiol nucleophiles. Moreover, 4-NN analogues with cationic-surfactant-like structures exhibited further enhanced nitrite release, underscoring the catalytic role of micellar confinement. These findings highlight confined environments as powerful modulators of NO-prodrug activation.