Au Bipyramids as NIR-II Contrast Agents for In Vivo Plant Imaging

In vivo plant imaging is crucial for understanding plant biology and the influence of external factors on plant health. While exogenous contrast agents are widely used in animal bioimaging to enhance contrast, track flows, and provide molecular specificity, their application in plant tissue remains challenging and underexplored. Herein, we highlight the shortcomings of contrast agents in optical coherence tomography of plant tissue while demonstrating the successful use of Au bipyramids (AuBPs) as effective NIR-II contrast agents in photoacoustic imaging, enabling spatiotemporal flow tracking in live Buttercrunch lettuce over 5 days. Furthermore, rigorous plant health studies showed no adverse effects of the AuBPs on the physiological properties of Buttercrunch lettuce 7 days postinfiltration. The use of AuBPs as contrast agents in plant imaging, combined with the versatility of their surface chemistry, opens the possibilities for studies with molecular specificity.