Therapeutic embolic agents for targeted drug delivery in transcatheter therapies: a review

Embolization has evolved from a purely mechanical occlusion technique to a multifunctional platform that supports imaging enhancement and therapeutic functions, including localized drug delivery, immunotherapy, and vascular remodeling. Although reviews on embolic agents have been published, the therapeutic performance of embolic platforms has not yet been systematically examined from a materials perspective linking material design and formation mechanisms to drug loading, release behavior, and therapeutic outcomes. In this review, we discuss the embolic system design principles and mechanisms underlying both clinically used and emerging embolic agents, emphasizing liquid/gel systems and microsphere (MS)-based platforms with integrated therapeutic functionality. We highlight how material design governs catheter delivery, vascular penetration, occlusion stability, and controlled drug release, key factors that govern the performance of all embolic categories. For liquid/gel embolics, we summarize clinical formulations alongside their reported outcomes, and we review emerging systems according to their mechanisms of solidification and biological interaction, including thermoresponsive gels, chemically triggered networks, complex coacervates, and shear-thinning nanocomposites. For MS embolics, we summarize clinically used materials and discuss emerging systems, focusing on how polymer chemistry, cross-linking, and network architecture regulate drug loading and release. Finally, we discuss key translational challenges in the emerging embolic systems and highlight opportunities for future embolic platforms that enable more precise and durable therapeutic control.