A dual-state emission luminogen for lipid droplet imaging and photodynamic therapy

Organic luminogens with dual-state emission (DSE) have garnered widespread attention due to their versatility in the forms of both dilute solutions and solids. Despite the growing interest, most research on DSE focuses primarily on molecule design and photophysical investigation, with limited exploration of their practical applications. In this study, we introduce a novel fluorescent molecule, PCT, featuring a distinct D-π(A)-D' electronic structure. PCT exhibited efficient DSE properties, with high quantum yields in both dilute solutions (Φ_THF = 52.3 %) and solid-state (Φ_solid = 74.6 %). Taking advantage of PCT's lipophilicity, we demonstrated its potential for targeted lipid droplet (LD) imaging in living cells and its utility in monitoring LD depletion during cellular starvation. To further enhance its applicability in photodynamic therapy (PDT), PCT was encapsulated within the amphiphilic triblock copolymer Pluronic F127, forming PCT@F127 nanoparticles with improved colloidal stability. These nanoparticles efficiently generated singlet oxygen (¹O₂) under white light irradiation, achieving a ¹O₂ quantum yield of 57.2 %. In vitro studies on MCF-7 cells revealed significant ¹O₂ generation and potent phototoxicity, leading to marked cell apoptosis and necrosis. These results underscore PCT's multifunctionality as a DSEgen, with promising applications in both bioimaging and PDT.