Biocompatible metal-free organic phosphorescent nanoparticles for efficiently multidrug-resistant bacteria eradication

Organic phosphorescence materials with longlived triplet excitons that can highly generate active singlet oxygen (¹O₂) through the energy transfer with the molecular oxygen under photoexcitation, serve as highly efficient antibacterial agent. Herein, we report bright red-emissive organic phosphorescent nanoparticles (PNPs) based on a metal-free organic phosphor encapsulated with biocompatible block copolymers. The obtained PNPs with an ultra-small particle size of around 5 nm and a long emission lifetime of up to 167 µs showed effective 1O2 generation ability under visible light (410 nm) excitation in aqueous media, which can efficiently eradicate multi-drug resistant bacteria both in vitro and in vivo. This is the first demonstration of metal-free organic PNPs for photodynamic antimicrobial therapy, expanding the application scope of metal-free organic room temperature phosphorescent materials.