Abstract: Various aspects of the present disclosure are directed toward implantable medical devices, systems, and methods for cardiac assistance.

Abstract: The present invention relates to vehicles for delivering macromolecules into cells. More particularly, embodiments of the invention relate to compounds and methods for binding and compacting nucleic acids into nanoparticles for transferring the polynucleotides into cells and which can be configured to provide a mechanism for visualization of the delivery vehicles on the nm/?m scale by microscopy and on the sub-mm scale by magnetic resonance imaging. Polycations according to embodiments of the invention have been designed to contain repeated oligoethyleneamines, for binding and compacting nucleic acids into nanoparticles, and lanthanide (Ln) chelates (for example, using luminescent europium Eu3+ and paramagnetic gadolinium Gd3+).