Mitochondria-Targeting Boron Dipyrromethene Based Photosensitizers for Enhanced Photodynamic Therapy: Synthesis, Optical Properties, and in vitro Biological Activity.

Increasing Investigations show that photosensitizers (PSs) which target mitochondria are useful for enhancing photodynamic therapy (PDT) efficacy. Herein, we carefully designed and synthesized four triphenylphosphonium (TPP)-modified boron dipyrromethene (BDP)-based PSs through Cu(I)-assisted "3+2" cycloaddition reaction. All of them exhibit intense red light absorption with maxima between 659 and 663 nm, considerable fluorescence emission with quantum yields of 0.16-0.23, high singlet oxygen generation efficiency ranging from 0.22 to 0.34, excellent mitochondria-targeting ability, and good biocompatibility. Upon illumination, they induce significant cancer cell death through a mitochondria-related apoptosis pathway. The IC 50 values of these BDP dyes against MCF-7 cells were determined to be as low as 0.046-0.113 μM under rather low dosage of light irradiation (1.5 J ⋅ cm -2 ).