Near-Infrared Imaging of Localized Longitudinal Nanoparticle Transport in Living Animals.

Visualizing the in vivo dynamic transport behavior of substances following acupoint injection has remained a significant challenge due to the limitations of conventional imaging techniques. Near-infrared (NIR) imaging, with its superior tissue penetration, reduced autofluorescence, and real-time tracking capability, presents a promising approach for acupoint-associated imaging; however, its application in this context is yet to be experimentally validated. Here, NIR imaging is utilized to uncover highly localized, longitudinal transport of nanoparticles on the body surface in an acupoint-injection mouse model. By employing three distinct NIR fluorophores-Cy5, Cy5-labeled tetrahedral DNA nanostructures (TDN-Cy5), and silver sulfide (Ag₂S) nanocrystals-it is demonstrated that acupoint injection induces directional migration along tissue-specific pathways, with nanoparticles exhibiting significantly prolonged retention compared to small molecules like Cy5. Notably, nanoparticles display minimal systemic distribution, with organ accumulation reduced to ≈1/50th of that observed with intravenous injection. This study underscores the unique capability of NIR imaging to visualize acupoint-associated transport dynamics, establishing a robust methodological framework to explore meridian-based substance delivery and its translational biomedical potential.