Toll-like receptor 9-overexpressing red blood cell biomimetic microbubbles adsorb cell-free DNA to relieve steatotic liver ischemia-reperfusion injury.

Patients with hepatic steatosis are highly susceptible to ischemia-reperfusion injury (IRI) but lack effective therapies. We identify elevated cell-free DNA (cfDNA) as a pathogenic driver and a therapeutic target. In metabolic dysfunction-associated steatotic liver disease (MASLD) patients and rat models, cfDNA levels correlate with IRI severity. Mechanistically, cfDNA acts as a damage-associated molecular pattern (DAMP) that activates endosomal TLR9-MyD88 and cytosolic cGAS-STING signaling cascades. These two pathways cooperatively promote M1 macrophage polarization and amplify the inflammatory response in steatotic liver IRI. To address this, we developed a biomimetic and theranostic approach: TLR9-overexpressing red blood cell membrane-biomimetic ultrasound microbubbles (RBC-MBs). These RBC-MBs mimic the natural cfDNA-scavenging function of erythrocytes, leading to efficient cfDNA adsorption, simultaneous suppression of both TLR9-MyD88 and cGAS-STING pathways, and re-polarization of macrophages to a protective M2 phenotype, thereby blocking the inflammatory cascade. This significantly alleviates hepatic IRI in MASLD rats while enabling concurrent ultrasound imaging. Our findings establish a novel translatable theranostic strategy that leverages a natural cfDNA clearance mechanism to treat steatotic liver IRI.