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.