Blood‐Triggering Phase Transformational Hydrogel for Endovascular Embolization

Abstract Hydrogels exhibit potential as embolic agents; however, external stimuli for gelation in vessels are difficult to operate or have poor biocompatibility, and shear‐thinning hydrogels are under the risk of being washed away. Herein, a blood‐triggering phase transformational hydrogel for endovascular embolization is reported. First, quaternized chitosan (QCS), tannic acid (TA) and iohexol (I) solutions are mixed to prepare a radiopaque and injectable QCS/TA/I (QTI) hydrogel. Upon contacting blood, Na⁺ in blood can form coordination bonds with gel network to increase cross‐linking densities, resulting in phase transformation from a soft and injectable hydrogel to a casted and stiffened QTI‐blood hydrogel without any other operation. Moreover, the injection force and complete transformation time of the QTI hydrogels as well as the mechanical properties of their derived hydrogels are adjustable, which is helpful for customizing embolic agents according to different lesions. In animal experiments, QTI hydrogel has demonstrated its efficacy and safety in embolizing renal artery and ruptured femoral artery in rabbits, as well as the renal artery, profunda femoral artery (≈4 mm in diameter), and retia mirabilia with plexiform structure in pigs. This work not only develops a novel liquid embolic agent but also reveals a new strategy for blood‐triggering phase transformation.