Ultralong Organic Phosphorescent Nanocrystals with Long-Lived Triplet Excited States for Afterglow Imaging and Photodynamic Therapy

The
development of novel applications of ultralong organic phosphorescent
(UOP) materials is highly desired. Herein, a series of UOP materials
(EDCz, E = O, S, Se, and Te) for bacterial afterglow
imaging and photodynamic therapy (PDT) is reported. By structurally
bonding with the chalcogen atoms with π-conjugated scaffolds, EDCz not only absorbs visible light but also emits UOP with
an efficiency of ca. 0.01–6.8% and a long
lifetime of 0.08–0.318 s under ambient conditions. Benefiting
from the long-lived triplet excited states, the SeDCz nanocrystals (NCs) possessed the best optical properties in the
series, generating 1O2 under white light irradiation
and performing as an agent for Staphylococcus aureus afterglow imaging and PDT at a low concentration (98 ng mL–1). The SeDCz NCs are also utilized as real-time UOP
imaging agents and promoted healing of infected wounds in living mice.
To the best of our knowledge, this study presents the first example
of UOP-based bacterial photodynamic theranostic agents and creates
a platform for the next-generation efficient UOP-based photosensitizers
for bioimaging and skin regeneration.