Liposomes loaded with dual clinical photosensitizers for enhanced photodynamic therapy of cervical cancer

Photodynamic therapy (PDT) has become a potential anti-cancer strategy owing to its negligible invasiveness, low toxicity, and high selectivity. The photosensitizer (PS) plays an indispensable role in PDT. Herein, a novel type of PS (Ce6-MB@Lips) which can be excited by a near-infrared (NIR) laser was designed and synthesized. Methylene blue (MB) and Chlorin e6 (Ce6), two organic dyes approved by the Food and Drug Administration (FDA), were used to prepare Ce6-MB@Lips by thin-film dispersion method, which improve the water solubility of Ce6 and reduce the cytotoxicity of MB. The Ce6-MB@Lips were shown to have a spherical nanostructure with an average particle size of 160.3 nm and excellent water solubility. Then the optical properties of Ce6-MB@Lips were further studied. Ce6-MB@Lips showed absorption peaks at 413 nm/670 nm and fluorescence peak at 697 nm. Compared with Ce6@Lips and MB@Lips, Ce6-MB@Lips showed better stability, stronger fluorescence intensity, and higher singlet oxygen (O-1(2)) generation ability. Cell experimental analysis exhibited that the stable Ce6-MB@Lips showed low cytotoxicity, high phototoxicity and high reactive oxygen species (ROS) production capacity. After effective cell internalization, the prepared Ce6-MB@Lips showed excellent ability to promote tumor cell apoptosis in vitro. The Ce6-MB@Lips could be a promising candidate for PDT of cervical cancer.