Bioorthogonal Activation of Deep Red Photoredox Catalysis Inducing Pyroptosis

The revolutionary impact of photoredox catalytic processes has ignited novel avenues for exploration, empowering us to delve into nature in unprecedented ways and to pioneer innovative biotechnologies for therapy and diagnosis. However, integrating artificial photoredox catalysis into living systems presents significant challenges, primarily due to concerns over low targetability, low compatibility with complex biological environments, and the safety risks associated with photocatalyst toxicity. To address these challenges, herein, we present a novel bioorthogonally activatable photoredox catalysis approach. In this approach, potent photocatalyst selection via atom replacement of the rhodamine core yielded the bioorthogonally activatable photocatalyst (PC-Tz). The introduction of 1,2,4,5-tetrazine quenched its photocatalytic properties, which were restored upon an intracellular inverse electron-demand Diels-Alder (iEDDA) reaction with trans-cyclooctene (TCO) localized in mitochondria. This reaction led to remarkable photocatalytic oxidation of nicotinamide adenine dinucleotide (NADH), effectively manipulating the mitochondrial electron transport chain (ETC) under hypoxic conditions in cancer cells. Additionally, photocatalytic pyroptotic cell death was observed through a caspase-3/gasdermin E (GSDME) pathway, achieving notable antitumor efficacy and adenosine triphosphate (ATP) reduction in tumor cells. To the best of our knowledge, this represents the first example of bioorthogonally activatable photoredox catalysis, opening new avenues for chemists to spatiotemporally control activity in specific cell organelles without disrupting other native biological processes.