pH-sensitive metal-phenolic network capsules for targeted photodynamic therapy against cancer cells.

Photodynamic therapy (PDT) is an effective and promising method for cancer treatment, which is proposed for more than one century. However, the specific delivery of photosensitizer to target carcinoma cells to reduce the side effect is still a great challenge. This work provides a strategy to deliver photosensitizers to cancer cells by utilizing pH-sensitive polyethylene glycol metal-phenolic network (PEG-MPN) capsules to encapsulate haematoporphyrin monomethyl ether (HMME). With the assistance of folic acid (FA), HMME-doped PEG-MPN capsules (MPN@HMMEs) accumulate in carcinoma cells selectively followed by releasing HMME in the lysosomes because of the physiologically relevant acidic pH environment. From the fluorescent ratiometric sensing and reactive oxygen species (ROS) regionality distribution of MPN@HMMEs, we demonstrated the encapsulated photosensitizers are diffused from lysosomes to cytoplasm. Under irradiation at 638 nm laser, ROS generated from the photosensitizers induced cancer cells undergoing apoptosis while normal cells survive. Therefore, MPN@HMME could be applied as a new strategy for targeted PDT against cancer and PEG-MPN capsules are expected to be general carries for drug delivering.