Study of oxygen-deficient W18O49-based drug delivery system readily absorbed through cellular internalization pathways in tumor-targeted chemo-/photothermal therapy

W 18 O 49 -mediated photothermal therapy (PTT) is affected by the easily oxidized property and its direct exposure to physiological environment can cause biological events, which limit its development in the biomedical field. Herein, a composite nanoparticle PVP-W 18 O 49 @C (PW@C), with significant antioxidant and excellent biocompatibility, was constructed to overcome the limitations of W 18 O 49 in the medical field. Oxygen-deficient W 18 O 49 , with irregular defect structure , was combined with hollow carbon nanospheres treated by reflux to obtain W 18 O 49 @C (W@C) similar to sea urchins. Compared with W 18 O 49 , W@C shows stronger antioxidant properties, and it still has the ability to convert light energy to heat energy after 6 months. In addition, polyvinyl pyrrolidone is coated on the surface of W@C to construct PW@C, which significantly improves biocompatibility of W@C. The photothermal conversion efficiency of PW@C was 42.9 ± 1.3. PWD (PW@C loaded with DOX·HCl) showed controllable drug release behavior under pH and NIR stimulation, and the drug release rate reached 69.1 ± 1.6% at pH = 5.0. Notably, PWD was readily absorbed by cells through clathrin/caveolae-mediated internalization channels, and the viability of HeLa cells treated with PWD + NIR was only 21.5 ± 1.0%. Through photothermal, drug delivery/release and cytotoxicity evaluation, PWD was proved to be an effective platform for chemo-/photothermal combinational tumor therapy.