Photocatalytic Production of Hydrogen Peroxide in Hypoxic Cancer Cells Enabled by Loose Ordered-Assembled Photosensitizer

The stepwise reduction of oxygen into O2•–, H2O2, and ·OH
by photosensitizers (PSs)
has a great advantage in killing cancer cells. Intensive attention
has been drawn to how to initiate the first step of yielding O2•–, yet the following transformations
have always been taken for granted. Herein, by regulating the assembly
behavior of triphenylamine and pyridine salt-based PSs with different
counteranions, the loose ordered-assembled structure of TPA-BPh4 accomplished the production of H2O2 and ·OH, while only O2•– but no ·OH can be detected for the other four PSs. The TPA-BPh4 displayed an ordered arrangement
with a larger intermolecular distance, favoring the adsorption of
H2O on the TPA-BPh4 and fostering the transformation into H2O2. The generated H2O2 triggered the Haber–Weiss
reaction to relieve intracellular hypoxia, efficiently killing cancer
cells. This work provides a new avenue for the design of photosensitizers
for the generation of H2O2 and ·OH.