Shape and Size Effects of Gold Nanoparticles for Tumor Photoacoustic Imaging and Photothermal Therapy Within the NIR‐I and NIR‐II Biowindows

Gold nanoparticles (AuNPs) have emerged as promising tools in cancer theranostics, particularly in applications involving photoacoustic imaging (PAI) and photothermal therapy (PTT). The optical and thermal properties of AuNPs can be precisely tuned by adjusting their shape and size, which, in turn, influences their performance within the first (NIR-I) and second near-infrared (NIR-II) bio-windows. This study explores how variations in the morphology of AuNPs, such as nanorods and nanodumbbells, affect their longitudinal surface plasmon resonance peaks, penetration depth, heating efficiency, and photoacoustic performance. Special attention is given to the superior capabilities of PEGylated NIR-II AuNPs in deep tissue imaging, photothermal conversion efficiency, effective tumor ablation, and biocompatibility compared to their NIR-I counterparts. NIR-II AuNPs also demonstrate significantly enhanced photoacoustic intensity, making them highly promising for clinical PAI. These findings underscore the potential of NIR-II-optimized AuNPs as potent agents for cancer theranostics, providing valuable insights into how the shape and size of AuNPs influence the aspect ratio, thereby optimizing imaging precision and treatment efficacy across the NIR-I to NIR-II spectrum.