ABSTRACT
Catheters navigating through complex vessels, such as sharp turns or multiple U-turns, remain challenging for vascular embolization. Here, we propose a novel multistage vascular embolization strategy for hard-to-reach vessels that releases untethered swimming shape-memory magnetic microrobots (SMMs) from the prior catheter to the vessel bifurcation. SMMs, made of organo-gel with magnetic particles, ensure biocompatibility, radiopacity, thrombosis, and fast thermal and magnetic responses. An SMM is initially a linear shape with a 0.5-mm diameter at 20 °C inserted in a catheter. It transforms into a predetermined helix within 2 s at 38 °C blood temperature after being pushed out of the catheter into the blood. SMMs enable agile swimming in confined and tortuous vessels and can swim upstream using helical propulsion with rotating magnetic fields. Moreover, we validated this multistage vascular embolization in living rabbits, completing 100-cm travel and renal artery embolization in 2 min. After 4 weeks, the SMMs maintained the embolic position, and the kidney volume decreased by 36%.
ABSTRACT
Endovascular embolization using microcoils can be an effective technique to treat artery aneurysms. However, microcoils with fixed designs are difficult to adapt to all aneurysm types. In this paper, a photocurable ultratough shape memory organogel with a curing time of only 2 s and megapascal-level mechanical properties is proposed. Then, it is used to manufacture the personalized 4D microcoil with a wire diameter of only 0.3 mm. The improved mechanical modulus (511.63 MPa) can reduce the possibility of microcoils' fracture during embolization. Besides, the fast body-temperature-triggering shape memory ability makes the 4D microcoil applicable in vivo. These 4D microcoils are finally delivered into the rabbit, and successfully blocked the blood flow inside different aneurysms, with neoendothelial cells and collagen fibers growing on the microcoil surface snugly, indicating full aneurysm recovery. This 4D organogel microcoil can potentially be used in personalized clinical translation on human beings.