Colloidal quantum dots with enhanced reactive oxygen species generation for photodynamic therapy by hydrogen peroxide via deionization

The colloidal quantum dots (QDs) with size-tunable electronic and photophysical properties, photostability, facile surface functionalization and photoactivated reactive oxygen species (ROS) generation capacity have emerged as dynamically developing materials for photodynamic therapy (PDT). Herein, high-quality water-soluble QDs with near-unity photoluminescence quantum yield (PL QY) and mono-exponential photoluminescence decay dynamics are constructed for investigating the effects of hydrogen peroxide (H₂O₂) overexpressed in the tumor microenvironment on photonics-driven ROS generation and PDT efficacy from a photophysical perspective. ROS are generated through interactions between photoexcited electron-hole pairs in QDs and molecular water/oxygen, and the formation of hydroxyl radical can be significantly enhanced in the presence of H₂O₂. Notably, spectroscopic signatures of photoexcited QDs, i.e. photoionization and deionization, are utilized to reveal the in-depth understanding of underlying mechanisms, which suggests that H₂O₂ participates in the excited-state electron transfer processes and replaces oxygen to promote the generation of ROS. Furthermore, in vitro studies show that QDs exhibit enhanced efficacy for cancer therapy in the presence of H₂O₂ and excellent fluorescent imaging capabilities for precisely pinpointing tumor areas. The results presented here shed new light on the comprehending and control of electrons, holes, and excitons in QDs, paving the way for a new generation of QDs-based PDT agents.