a, Mature neutrophils (NEs) are isolated from the mouse bone marrow using fluorescence-activated cell sorting. Paclitaxel (PTX) is encapsulated into cationic liposomes (CLs) containing a synthetic cationic lipid, 1,5-dioctadecyl-N-histidyl-l-glutamate (HG2C18). The positively charged PTX-CL surface facilitates uptake by NEs through electrostatic adsorption. Therefore, purified NEs are loaded with PTX-CL through simple incubation. The generated PTX-CL/NEs are then injected intravenously in mice. b, The therapeutic effect involves the following steps: (i) PTX-CL/NE extravasate into the brain by crossing the BBB at sites of inflammation that are generated by the resection of the brain tumour. (ii) PTX-CL/NEs migrate throughout the inflammatory site (light blue circle) by responding to a chemotactic gradient. (iii) Inflammatory factors trigger the burst of PTX-CL/NEs and release of PTX-CL (red circles). (iv) PTX-CL are absorbed by tumour cells and PTX (black dots) is released inside the cytoplasm. (v) PTX toxicity causes tumour cell death. SPC, soy phosphatidylcholine; Chol, cholesterol.