Intracellular MR Contrast Agents Based on Cationic Cell Penetrating Peptides: A Comparative Study

For the development of intracellular Magnetic Resonance contrast agents (CAs) it is a prerequisite that they cross the plasma membrane. Cell penetrating peptides (CPPs) are known to transport cargo molecules attached to it into cells. We synthesized intracellular CAs containing known CPPs or modified peptides. Gd-diethylenetriaminepenta-acetic acid (Gd-DTPA) was coupled to CPPs for MR visualization and fluorescence imaging agent fluorescein isothiocyanate (FITC) for tracking the agent inside cells by optical imaging. Compared on the basis of these measurements, modifications in CPPs enhanced the intracellular delivery ability of our CAs providing a tool for stable labeling of cells for MR imaging