A hydroxyl radical-activated NIR-II hemicyanine photosensitizer for selective photodynamic cancer therapy

A water-soluble and heavy-atom-free hemicyanine photosensitizer, H-WBHcy, specifically activated by ˙OH (a tumor biomarker), was synthesized for the first time. H-WBHcy could sensitively respond to ˙OH (LOD = 8.7 nM), showing red-shifted absorption from 500 nm to 694/765 nm as well as fluorescence emission at 910 nm. Meanwhile, ˙OH was able to trigger the oxidized product of H-WBHcy to further produce ¹O₂ under 808 nm laser irradiation, which could significantly inhibit the growth of cancer cells. We believe this work provides a strategy for developing activatable near-infrared photosensitizers for precise photodynamic therapy.