Optoacoustic visualization of individual core-shell microparticles in vivo

The feasibility of real-time tracking of microparticles intravenously injected into living organisms can significantly facilitate the development of new biomedical applications, including blood flow characterization, drug delivery, and many others. However, existing imaging modalities generally lack the sensitivity to detect the weak signals generated by individual particles flowing through vascular networks deep within biological tissues. Also, the temporal resolution is usually insufficient to track the particles in an entire three-dimensional region. Herein, we capitalize on the unique advantages of a state-of-the-art high-frame-rate optoacoustic tomographic imaging system to visualize and track monodisperse core-shell microparticles with a diameter of 4m in the mouse brain vasculature. The feasibility of localizing individual solid particles smaller than red blood cells opens new opportunities for mapping the blood flow velocity, enhancing the resolution and visibility of optoacoustic images, and developing new biosensing assays.