Glutathione-depleting photosensitizers for tumor-specific imaging and pyroptosis-driven photodynamic therapy

<b>Rationale:</b> Selective initiation of pyroptosis in malignant cells can amplify the immunological benefits of photodynamic therapy (PDT), but conventional photosensitizers (PSs) often lack tumor specificity and require complex subcellular targeting motifs. Here we describe a glutathione (GSH)-responsive PDT platform based on PSs that integrate fluorescence turn-on, GSH depletion, and restoration of reactive oxygen species (ROS) generation into a single molecular design. <b>Methods:</b> GSH-activated photosensitizers MTP-NO₂ and NTP-NO₂ were synthesized based on donor-acceptor structure, with their GSH-triggered activation, GSH depletion, ROS restoration, and caspase-1/GSDMD-mediated pyroptosis systematically demonstrated in 4T1 cells, while tumor accumulation, biodistribution, <i>in vivo</i> activation, and photodynamic antitumor efficacy of PSs nanoparticles were comprehensively assessed in 4T1 tumor-bearing mice through fluorescence imaging and immunohistochemical analyses. <b>Results:</b> Among a library of donor-acceptor scaffolds, the π-extended acene derivative NTP-NO₂, equipped with a para-dinitrophenoxybenzyl pyridinium quencher, exhibited strong optical activation and ROS production upon reaction with elevated GSH in tumor cells. This dual action, antioxidant depletion and ROS restoration, triggered caspase-1/gasdermin-D-mediated pyroptosis, IL-1β/IL-18 release, and robust immunogenic cell death. Nanoparticle delivery of NTP-NO₂ achieved high tumor accumulation, precise imaging, and pronounced antitumor efficacy <i>in vivo</i>. <b>Conclusion:</b> By exploiting tumor GSH overexpression-activated photodynamic therapy, the NTP-NO₂ depletes GSH and promotes caspase-1/GSDMD pathway to trigger robust pyroptosis, eliciting inflammatory/immune responses both <i>in vitro</i> and <i>in vivo</i>. This chemically defined approach provides a PS design that unites selective activation, immune-stimulatory cell death, and precise photodynamic tumor ablation.