Photodynamic therapy (PDT) has gained widespread acceptance as a clinical cancer treatment modality and has been attracting intensive attention on developing novel PDT strategies. However, the hypoxic environment in tumors is considered as a significant challenge for efficient type II PDT, based on the inference of the highly oxygen-concentration-related O generation. Contrary to this conventional understanding, our research demonstrates oxygen concentration independence in the photosensitized generation of O, as evidenced through steady-state and transient spectroscopy for chlorin e6 and methylene blue from normoxic to hypoxic conditions. We propose an oxygen-concentration-independent kinetic model, suggesting that efficient O generation can take place as long as the triplet-state lifetime ratio of the photosensitizer (τ/τ) is in a similar range to pO/pO. Our findings provide insights into PDT mechanisms and indicate that the oxygen concentration reduction concerns may not be critical for effective PDT in hypoxic tumor environments.
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http://dx.doi.org/10.1021/acs.jpclett.4c02547 | DOI Listing |
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