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.