Nanoparticles from Ancient Ink Endowing a Green and Effective Strategy for Cancer Photothermal Therapy in the Second Near-Infrared Window

[Image: see text] Photothermal therapy (PTT) in the second near-infrared window (NIR-II, 1000–1350 nm) has presented great superiority in cancer treatment recently. However, it is generally limited to a few photothermal agents and most of them often suffer from intricate design and complicated synthesis. Herein, by subtly extracting nanoparticles from ancient ink (AINPs), a versatile AINP dispersion with definite ingredients, good biosafety, and excellent photothermal effect in the NIR-II window was obtained. In vivo trials demonstrated that the obtained AINP dispersion provides a promising alternative for tumor sentinel lymph node (SLN) mapping. Besides, under the guidance of photoacoustic imaging, the metastatic SLNs could be accurately eliminated by NIR-II laser irradiation. The preliminary biosafety of AINP dispersion has also been systematically confirmed. Therefore, we believe this work would provide a green and effective strategy for PTT of tumor in the NIR-II window.