Cardiovascular diseases are the leading cause of death worldwide. While current pharmaceutical therapies are beneficial, they still have several limitations regarding efficacy and side effects. This issue stems from the inadequate targeting of cardiomyocytes and the difficulties that certain therapeutic molecules face in penetrating the intact cell membrane.

We aim to develop a delivery system specifically designed to target cardiomyocytes using liposomes functionalized with our cardiac-targeting peptides. We will evaluate their effectiveness in delivering therapeutic molecules directly to cardiomyocytes in vitro.

PEGylated liposomes were produced using the thin lipid film hydration method followed by extrusion. The post-insertion method was used to functionalize the liposomes with various fluorescent labels and peptides. Additionally, direct labeling of liposomes with rhodamine was used to evaluate cellular internalization. Dissociated neonatal rat ventricular cardiomyocytes (NRVM) were incubated for two hours with rhodamine-liposomes to compare three formulations: naked liposomes (LipoRho), liposomes functionalized with the non-specific cell-penetrating peptide TAT (LipoRho+TAT), and liposomes functionalized with a specific cardiac-homing peptide (LipoRho+SCHoP) (Fig. 1).

The produced liposomes exhibited a uniform population approximately 140nm in size and had a negative surface charge. The optimized post-insertion protocol for functionalizing the liposomes showed an efficiency of about 80% for the SCHoP peptide. Spinning disk confocal images revealed that the liposomes successfully transduced cardiomyocytes. Specifically, LipoRho+TAT and LipoRho+SCHoP showed increased internalization in NRVM compared to non-functionalized liposomes (LipoRho).

This promising data tackles the unresolved challenge of targeting the heart tissue by demonstrating that a cardiac-targeting peptide can efficiently decorate a liposome surface and enhance its internalization in cardiomyocytes.