Applications of the Photocatalytic and Photoacoustic Properties of Gold Nanorods in Contrast-Enhanced Ultrasound and Photoacoustic Imaging

The applications of ultrasound imaging are often limited due to low contrast, which arises from the comparable acoustic impedance of normal tissues and disease sites. To improve the low contrast, we propose a contrast agent called gas-generating laser-activatable nanorods for contrast enhancement (GLANCE), which enhances ultrasound imaging contrast in two ways. First, GLANCE absorbs near-infrared lasers and generates nitrogen gas bubbles through the photocatalytic function of gold nanorods and photolysis of azide compounds. These gas bubbles decrease the acoustic impedance and highlight the injection site from the surrounding tissues. Second, GLANCE exhibits photoacoustic properties owing to the gold nanorods that emit photoacoustic signals upon laser irradiation. Additionally, GLANCE offers several benefits for biomedical applications such as nanometer-scale size, adjustable optical absorption, and biocompatibility. These distinctive features of GLANCE would overcome the limitations of conventional ultrasound imaging and facilitate the accurate diagnosis of various diseases.