Janus Gold Nanodiscs with an Asymmetrically Positioned Polyaniline Nano-Urchin for Photothermal Therapy and Multimodal Imaging in the Second Near-Infrared Window.

The second near-infrared (NIR-II) window (1000-1700 nm) offers advantages in biomedical applications such as deeper tissue penetration and superior imaging contrast. Despite this potential, existing NIR-II probes are limited by biocompatibility concerns, photobleaching, and poor photostability, issues that constrain their clinical utility. This study introduces Janus-type gold nanodiscs having an asymmetrically integrated hierarchical polyaniline (PANI) structure, optimized for use as multifunctional agents for NIR-II photothermal therapy and multimodal imaging. By shifting the localized surface plasmon resonance of the gold nanodiscs─the foundation of the Janus structure─from NIR-I to NIR-II, the developed AuPANI nanodiscs achieve remarkable deep-tissue photoacoustic imaging, up to 15 mm, while also enabling highly sensitive positron emission tomography imaging through stable radiolabeling. The nanodiscs also exhibit superior photostability and notable efficacy as photoacoustic-guided photothermal therapy agents under 1064 nm irradiation. This study positions AuPANI nanodiscs as a versatile platform for NIR-II theranostics, addressing limitations of current probes and advancing their potential for precise and effective cancer treatment.