Chair-Shaped Indoline Donor Enabling Near-Infrared Imaging-Guided Type I Photodynamic Therapy

Imaging-guided photodynamic therapy (PDT) represents a promising treatment modality owing to its high precision and minimal invasiveness. However, insufficient oxygen supply within solid tumors and aggregation-caused quenching (ACQ) of photosensitizers (PSs) limit the clinical application of imaging-guided PDT. Herein, we developed a type I reactive oxygen species (ROS) predominant photosensitizer (IDL-CPy) based on a unique chair-shaped ultra-strong electron donor indoline with aggregation-induced emission (AIE) characteristics, enabling imaging-guided type I PDT. The electron-rich indoline structure enhances intramolecular charge transfer, which narrows the singlet-triplet energy gap, thereby facilitating type I ROS generation. Theoretical and experimental analyses demonstrate that IDL-CPy exhibits an ideal intersystem crossing rate and triplet excited state lifetime for generating ROS, contributing to potent anticancer efficacy in vitro (IC₅₀ = 0.34 μM). This research represents the first indoline-based AIE photosensitizers and provides a promising candidate for imaging-guided type I PDT.