High-resolution intravascular photoacoustic (IVPA) imaging can potentially improve the identification of atherosclerosis plaque. However, the absorption of water and the low coupled laser energy resulted in insufficient excitation energy provided by the single-mode fiber-based IVPA endoscope to achieve high-resolution and deep-penetration plaque imaging. In this paper, we developed a 1 mm diameter IVPA endoscope assembled with a Ø25-Ø9 μm tapered fiber. Owing to high coupling efficiency and the small output facula of tapered fiber, the IVPA endoscope has an optimal lateral resolution of 18 μm and a large imaging-depth covering from the intima to the peri-adventitial adipose, as confirmed by imaging results respectively. Furthermore, IVPA imaging in the blood has confirmed that the tapered fiber-based endoscope can display the distribution and the relative concentration of lipid in ex vivo plaque precisely. By the obtained histology-like images, IVPA imaging shows great potential for accurately imaging atherosclerosis plaque.

Rupture or erosion of inflammatory atherosclerotic vulnerable plaque is essential to acute coronary events, while the target intervene of vulnerable plaque is very challenging, due to the relatively small volume, high hemodynamic shear stress, and multifactorial nature of the lesion foci. Herein, we utilize the biological functionality of neutrophil and the versatility of microbubble in the acoustic field, to form Neu-balloon through CD11b antibody binding. The Neu-balloon inherits the advantage of neutrophils on firming the endothelium adhesion even at shear stress up to 16 dyne/cm ² and also maintains the acoustic enhancement property from the microbubble, to accumulate at atherosclerotic lesions under acoustic in an atherosclerotic Apo E ^-/- mice model. Interestingly, Neo-balloon also has high and broad drug loading capacity, which enables the delivery of indocyanine green and miR-126a-5p into vulnerable plagues in vivo . Overall, the bionic Neu-balloon holds great potential to boost on-demand drug transportation into plaques in vivo .

Intravascular photoacoustic (IVPA) imaging, benefiting from high optical contrast, large imaging depth and absorption specificity, is of great potential for lipid-rich plaque detection. However, the diameters of reported IVPA endoscopes are too big to intervene into the coronary artery branches. Here, by designing an ultracompact house embedded with a side-fire fiber and a miniature single-element ultrasound transducer, we developed an ultrafine IVPA endoscope with a diameter of 0.7 mm aiming at coronary artery branches atherosclerotic plaque detection. The reliability and feasibility of the ultrafine IVPA endoscope was demonstrated by imaging a stent with a 1.6 mm inner diameter. Furthermore, the photoacoustic imaging and ultrasound imaging of a mouse thoracic aorta with an inner diameter of 1.15 mm was conducted to verify the clinical potentiality of the endoscope, and the PA images have good consistency with histological staining results. To the best of our knowledge, this is the first time we have achieved the IVPA imaging in fine vessel by the 0.7 mm diameter ultrafine photoacoustic endoscope, which paved a way for the translation of the IVPA endoscope to clinical application.