Abstract: Near-infrared (NIR) light-induced photothermal therapy (PTT) has become a new method for precise tumor treatment due to its non-invasive, low toxicity, and targeted treatment.  Gold nanoparticles have become an ideal photothermal agents due to its unique surface plasmon resonance (SPR), efficient photothermal conversion efficiency, low biological toxicity and good photostability. High quality imaging technology is a reliable and powerful tool for achieving effective photothermal therapy, especially multimodal imaging technology, which has excellent performance compared to a single imaging method, providing the possibility for more comprehensive and accurate tumor imaging, thereby significantly improving the potential of non-invasive medical treatment. Owing to their rich 4f electronic structure, NIR light excited rare-earth doped upconversion nanoparticles (UCNPs) exhibit multifunctional properties such as magnetism, fluorescence, X-ray attenuation, and radiation, making them an important application prospect in multimodal imaging as contrast agents. Therefore, constructing NIR-induced Au NPs/UCNPs composite nanosystems for multimodal imaging-guided photothermal therapy is expected to become a new strategy for cancer diagnosis and treatment. In this paper, we briefly introduced the optical properties of Au and UCNPs.  In addition, this paper reviewed the latest research progress of PTT research on NIR induced UCNPs Au (nanoshell, nanorod, nanoclusters) composite nano system under the guidance of visual fluorescence imaging. The future prospects for achieving integrated diagnosis and treatment are presented, providing new ideas for its further research, development, and clinical application.
Key words: near-infrared; photothermal therapy; fluorescence imaging; upconversion nanoparticles; Au NPs
（Acta Laser Biology Sinica, 2023, 32(4): 297-303）