Polymer Platform for Peroxynitrite Detection Utilizing Benzopyrylium Chemistry

Continuous detection of peroxynitrite, a highly reactive oxygen and nitrogen species linked to the onset and severity of oxidative stress, is essential for real-time monitoring of disease progression. While benzopyrylium (BZP)-based two-photon fluorogenic probes offer promising selectivity, small molecule designs are hampered by short detection lifetimes, poor solubility, narrow pH stability, limited modularity, and rapid clearance in vivo. Here, we report the first polymeric BZP-based peroxynitrite probes, enabled by ring-opening metathesis polymerization (ROMP) of norbornene-functionalized BZP monomers (M2). These macromolecular platforms exhibit broad pH stability, enhanced selectivity, and modular tunability. Upon self-assembly into nanoparticles, the resulting systems display bathochromic shifts toward near-infrared two-photon emission for high-resolution, ratiometric sensing. Exposure to peroxynitrite triggers progressive nanoparticle aggregation and swelling into complex globular morphologies, resulting in prolonged detection lifetimes and tunable response kinetics. Compared to their small molecule counterparts, these nanoparticle probes show significantly improved cytocompatibility in healthy CHO and SKOV3 cells. This modular polymeric platform sets the stage for next-generation, high-performance oxidative stress sensors capable of continuous, disease-relevant monitoring in biological environments.