NIR‐II Cyanine Nanoparticles for Imaging‐Guided Tumor Targeting Photothermal Therapy with Vitamin C Enhanced Efficacy

Abstract Cyanine dyes in the near‐infrared‐II (NIR‐II) region are among the most promising photothermal agents, due to their high photothermal conversion efficiency, strong tumor targeting capability, and deep tissue penetration. The application of cyanine‐based photothermal agents remains limited, however, due to the invasive nature and spread of tumors as well as the potential for inflammatory responses during the treatment process. In this work, a naphtho[cd]indolium‐based heptamethine cyanine with NIR‐II emission is utilized to prepare PEGylated nanoparticles for studies of photothermal treatment. The results demonstrate that the nanoparticles have excellent NIR‐II imaging and tumor targeting capabilities. As a result of the light harvesting property of naphtho[cd]indolium‐based heptamethine cyanine, these nanoparticles demonstrate a photothermal conversion efficiency of 61%. The tumor‐targeting properties of these nanoparticles enable them to accumulate effectively at limbs containing tumors. Photothermal therapy shows almost complete disappearance of all tumors after eight days of treatment. In addition, hematoxylin‐eosin stains (H&E stains) of major organs show no discernible lesions throughout the treatment process. Furthermore, simultaneous injection of natural vitamin C during the treatment significantly improves the therapeutic effect of photothermal therapy.