<i>In vitro</i> evaluation of 3D-printed conductive chitosan–polyaniline scaffolds with exosome release for enhanced angiogenesis and cardiomyocyte protection

Myocardial infarction (MI) often results in significant damage to heart tissues, leading to cardiac dysfunction, fibrosis, and diminished cell-cell communication. Exosomes (EXOs) from stem cells show great potential in promoting tissue repair and angiogenesis, but their rapid clearance and degradation <i>in vivo</i> limit therapeutic efficacy. Here, we introduce a 3D-printed <i>in vitro</i> scaffold using a conductive biomaterial ink composed of chitosan (CS) and polyaniline (PANI). This scaffold combines the bioactivity of EXOs with the conductive properties of PANI to protect cardiac cells under ischemic stress. Using an <i>in vitro</i> hypoxia/reoxygenation (H/R) model with HL-1 cardiomyocytes, we simulated key aspects of myocardial ischemia-reperfusion injury. The addition of PANI improved the electrical conductivity of the scaffold, which was essential for enhancing cardiomyocyte viability and intercellular connectivity under hypoxic conditions. EXOs significantly promoted angiogenic activity <i>in vitro</i>, as evidenced by enhanced human umbilical vein endothelial cell (HUVEC) migration and robust tube formation, highlighting their role in stimulating new blood vessel growth. Molecular analyses revealed that EXOs positively influence processes such as angiogenesis and inflammation regulation in HL-1 cells. Additionally, EXOs improved HUVEC migration, emphasizing their pro-angiogenic role. These findings indicate that combining PANI and EXOs in a 3D-printed scaffold yields synergistic benefits, improving cardiomyocyte function and promoting endothelial angiogenesis <i>in vitro</i>, thereby providing insights for future cardiac repair strategies.