Coumarin-Quinazolinone based photosensitizers: Mitochondria and endoplasmic reticulum targeting for enhanced phototherapy via different cell death pathways

Organelle-targeted photosensitizers (PSs) offer valuable tools for improving photodynamic therapy (PDT), yet systematic studies on how different organelles influence phototherapeutic outcomes are limited. In particular, the connection between organelle targeting and various modes of programmed cell death remains unclear. In this study, we developed a series of PSs using the Coumarin-Quinazolinone (CQ) scaffold, each designed to target different organelles, including the mitochondria, endoplasmic reticulum (ER), lysosome, and nucleolus. Our results show that their PDT performance is highly dependent on their localization, with phototoxic index (PI) ranging from 2 to 245. Notably, the mitochondria-targeted CQ-Mito and ER-targeted CQ-ER exhibited profound phototherapeutic performances, with PI of 167 and 245 respectively. Our further study reveals that CQ-Mito causes cell death by both apoptosis and ferroptosis, while CQ-ER primarily triggers ferroptosis. This study not only provides new agents for PDT but also offers insights into how organelle targeting influences cell death mechanisms, which can shed light on the design of PSs for controlled cell death.