Bacteria-derived membrane vesicles to advance targeted photothermal tumor ablation

Nanoscale outer membrane vesicles (OMVs) secreted by Gram-negative bacteria are often applied in antibacterial treatment as adjuvants or antigens. Recently, OMVs have also been tested in a few anti-tumor treatment studies, in which OMVs are injected multiple times to achieve certain therapeutic effects, showing risks in repeated cytokine storms. Herein, we propose the use a single low dose of OMVs combined with photothermal therapy (PTT) for effective cancer treatment. It was found that single i. v. injection of OMVs could activate the immune system by boosting the secretion levels of anti-tumor related cytokines. In addition, single i. v. injection of OMVs could also lead to extravasation of red blood cells in the tumor mainly owing to the effect of lipopolysaccharide on the OMVs. Such effect was not observed in other normal organs. As the results, the tumors on OMV-treated mice showed obviously darkened color with greatly increased intratumoral optical absorbance in the near-infrared (NIR) region, further enabling effective photothermal ablation of those tumors by the NIR laser. Without causing obvious adverse responses, bacteria-derived OMVs may be a new type of therapeutic agent for cancer treatment with multiple functions.