Procoagulant CaCO3-embedded embolic microspheres can potentiate transcatheter arterial embolization of hepatocellular carcinoma

Transcatheter arterial embolization (TAE) represents a preferred therapeutic modality with minimal invasiveness for unresectable intermediate and advanced hepatocellular carcinoma (HCC) patients. However, its therapeutic outcome is restricted by incomplete occlusion of the whole tumor vasculature and exacerbated tumor immunosuppression due to the lack of ideal embolic agents. Herein, procoagulant embolic microspheres with tunable sizes are prepared by loading thrombin into calcium carbonate (CaCO3) nanoparticle-embedded gelatin microspheres (Th-CaCO3@gelatin MSs) via a microfluidic process. In this system, the yielded Th-CaCO3@gelatin MSs are capable of occluding main tumor-feeding blood vessels, while the released thrombin and Ca2+ triggered by the acidic tumor microenvironment can synergistically promote the formation of intravascular blood clots to occlude tumor capillaries. Meanwhile, the embedded CaCO3 nanoparticles can work as proton sponges to neutralize tumor acidity and thus effectively reverse tumor immunosuppression. Resultantly, TAE treatment with Th-CaCO3@gelatin MSs exhibits the most effective tumor suppression efficacy on orthotopic N1S1 HCC rat xenografts without causing obvious toxic effects. Therefore, this study highlights that our biocompatible embolic microspheres are capable of potentiating conventional TAE treatment by promoting pH-responsive tumor vascular infarction and neutralizing the acidic tumor microenvironment, with great potential in clinical translation.