A type I and II compatible vinyl-pyridine modified BODIPY dimer photosensitizer for photodynamic therapy in A-549 cells

Abstract

In this paper, the vinyl-pyridine group was used to modify the BODIPY dimer photosensitizer (T-BDP₂) to obtain a VP-BDP₂ photosensitizer. Compared with the T-BDP₂ photosensitizer, the VP-BDP₂ photosensitizer could work under pure water conditions, the singlet oxygen yield was increased from 9.38% to 22.2%, the charge transfer rate was increased from about 30 ps to about 10 ps, and the red emission was enhanced in fluorescence imaging. In addition, the VP-BDP₂ photosensitizer could also generate the superoxide radical (O₂˙⁻) under pure water conditions. The ROS generation mechanism of the VP-BDP₂ photosensitizer was considered to be the spin–orbit charge-transfer intersystem crossing (SOCT-ISC) mechanism, which was verified by fs-transient absorption spectra and theoretical calculation. In the photodynamic therapy of A-549 cells, the VP-BDP₂ photosensitizers could generate singlet oxygen and superoxide radicals (O₂˙⁻) under biological conditions, and showed high phototoxicity with the IC₅₀ value at 12.1 μM under light at 525 nm. Additionally, the multiple dipolar configuration meant that the VP-BDP₂ photosensitizer could be used in two-photon fluorescence zebrafish imaging under 800 nm excitation, which sets the stage for future two-photon photodynamic therapy.