Abstract: Myocardial infarction (MI) continues to be the primary cause of death globally. Oxidative stress in the initial phase of MI, followed by uncontrolled and excessive myocardial fibrosis, significantly impedes cardiac repair efficiency post-MI, culminating in adverse ventricular remodeling and potential heart failure. To address the diverse pathological stages of MI, an injectable composite hydrogel containing versatile nanoparticles was developed. In this study, mesoporous silicon nanoparticles (MSNs) served as carriers for encapsulating microRNA-29b (miR-29b) mimics with antifibrotic activity, subsequently coated with a complex of natural antioxidant tannic acid and zinc ions (TA/Zn). These nanoparticles were then embedded into a biocompatible alginate hydrogel to enhance retention within the infarcted myocardium. Upon injection into the infarcted region of MI mice, the composite hydrogel gradually released the nanoparticles as it degraded. Initially, the TA/Zn complex on the outer layer scavenged reactive oxygen species, thereby inhibiting cell apoptosis. The subsequent dissociation of the TA/Zn complex led to the release of the encapsulated miR-29b mimics that could inhibit the activation of cardiac fibroblasts and collagen production, thereby alleviating fibrosis progression. Overall, this composite hydrogel demonstrated the potential to reduce infarct size and improve cardiac function, suggesting its promise as a synergistic therapeutic approach for repairing infarcted myocardium.

Key words: Myocardial infarction, Injectable hydrogel, Antioxidant, Myocardial fibrosis