Enhancing the therapeutic efficacy of photodynamic therapy in colon cancer based on an ECN-mediated targeted drug delivery strategy

Photodynamic therapy (PDT) has attracted considerable interest in tumor treatment due to its precise temporal and spatial control. However, the off-target effects of photosensitizers and the hypoxic tumor microenvironment limit the production of reactive oxygen species (ROS), reducing PDT effectiveness. To address this challenge, we utilized Escherichia coli Nissle 1917 (ECN) as host cells and employed tannate (TA) and FeCl₃ in a bio-warp method to encapsulate IR775 on the surface of ECN forming TA@Fe@IR775@ECN (notes as T@I@E). At the tumor site, Fe³⁺ decomposes H₂O₂ to release O₂ within the tumor microenvironment, which interacts with IR775 to increase ROS production locally. Compared to non-living drug delivery methods, T@I@E actively targets tumor cells, achieving approximately 6-fold higher accumulation of IR775 at the tumor site and alleviating tumor hypoxic to enhance PDT efficacy. The favorable biocompatibility of T@I@E further supports its potential for clinical application, establishing T@I@E as a promising candidate for tumor therapy as a living material.