Photo-killing mechanism of 2-demethoxy-2,3-ethylenediamino hypocrellin B (EDAHB) to HeLa cells.

2-Demethoxy-2,3-ethylenediamino hypocrellin B (EDAHB) is a diamino-substituted hypocrellin B (HB) with high absorption of red light and high quantum yield of both singlet oxygen ((1)O(2)) and superoxide anions (O(2)(-)). Here we reported the cellular uptake, subcellular location, and cytotoxicity of EDAHB, as well as EDAHB-mediated photodynamic therapy (PDT) efficiency, and cell apoptosis. Results showed that EDAHB accumulated in HeLa cells rapidly up to 1h, with a subsequent decrease in the rate of uptake. EDAHB distributed with well-defined spots throughout the cytoplasm of the cells. EDAHB showed a much higher photopotentiation factor than HB. The phototoxicity of EDAHB to HeLa cells occurred via a mitochondria/caspase apoptosis pathway. This study showed EDAHB to be a promising candidate of photosensitizer for anti-tumor PDT.