Hypoxia is a hallmark of many malignant solid
tumors. The inadequate
oxygen concentration in the hypoxic regions of a solid
tumor impedes the efficiency of
photodynamic therapy (
PDT) because the generation of
reactive oxygen species during the
PDT process is directly dependent on the available
oxygen. To enhance the therapeutic efficacy of
PDT, we have developed a novel catalytic nanoplatform (nGO-hemin-Ce6) by co-encapsulating
hemin as a
catalase-mimetic nanozyme and
chlorin e6 (Ce6) as a
photosensitizer into
Pluronic-coated nanographene
oxide through simple hydrophobic interaction and π-π stacking. The nanosystem showed high cellular uptake in the
breast cancer cells but did not show any cytotoxicity in the dark condition. nGO-hemin-Ce6 showed efficient O2 generation capacity in the presence of H2O2, through the
catalase-mimetic activity of
hemin. In the in vitro cell experiments, only nGO-hemin-Ce6 could show comparable
PDT effect in normoxia as well as
hypoxia due to the in situ O2 generation capability. Upon
intravenous administration, nGO-hemin-Ce6 nanosystem showed high
tumor accumulation through passive targeting owing to their small size (~ 50 nm). Within the
tumor,
hemin generated O2 from the endogenous H2O2 and attenuated
hypoxia as evidenced by the reduced expression of HIF-1α, a prominent
hypoxia marker. Meanwhile, catalytically generated O2 markedly improved the therapeutic efficiency of
PDT in a mouse
tumor xenograft model by aiding the light-induced ROS production by Ce6. Compared to a control nanosystem without
hemin (nGOCe6), the catalytic nanosystem of nGO-hemin-Ce6 exhibited significantly higher
tumor suppression ability.