Lysosome‐Targeted Bifunctional Fluorescent Probe and Type I/II Photosensitizer for Viscosity Imaging and Cancer Photodynamic Therapy

ABSTRACT Abnormal lysosomal viscosity is closely associated with cancer progression, underscoring the need for bifunctional fluorescent probes and photosensitizers (PSs) that can both monitor viscosity and facilitate imaging‐guided therapy for simultaneous cancer diagnosis and treatment. Despite advances in lysosome‐targeted PSs development, few have demonstrated the ability to generate both Type I and Type II reactive oxygen species (ROS). In this study, we present BTTPA , a lysosome‐targeted fluorescent probe and photosensitizer, designed to integrate cancer diagnosis via viscosity imaging and cancer treatment through photodynamic therapy (PDT). Our findings reveal that BTTPA selectively targets lysosomes, enabling dynamic monitoring of cellular viscosity and distinguishing cancer cells from normal cells. Upon light activation, BTTPA efficiently generates both Type I and Type II ROS. Apoptosis assays further confirm BTTPA 's effectiveness in inducing cancer cell apoptosis, highlighting its potential as a powerful tool for cancer diagnosis and therapy.