Multifunctional magnetic nanoparticles for targeted delivery.

A major problem associated with drug therapy is the inability to deliver pharmaceuticals to a specific site of the body without causing nonspecific toxicity. Development of magnetic nanoparticles and techniques for their safe transport and concentration in specific sites in the body would constitute a powerful tool for gene/drug therapy in vivo. Furthermore, drug delivery in vitro could improve further if the drugs were modified with antibodies, proteins, or ligands. For in vivo experiments, magnetic nanoparticles were conjugated with plasmid DNA expressing enhanced green fluorescent protein (EGFP) and then coated with chitosan. These particles were injected into mice through the tail vein and directed to the heart and kidneys by means of external magnets of 25 gauss or 2kA-kA/m. These particles were concentrated in the lungs, heart, and kidneys of mice, and the expression of EGFP in these sites were monitored. The expression of EGFP in specific locations was visualized by whole-body fluorescent imaging, and the concentration of these particles in the designated body locations was confirmed by transmission electron microscopy. In another model system, we used atrial natriuretic peptide and carcinoembryonic antigen antibodies coupled to the chitosan-coated magnetic nanoparticles to target cells in vitro. The present work demonstrates that a simple external magnetic field is all that is necessary to target a drug to a specific site inside the body without the need to functionalize the nanoparticles. However, the option to use magnetic targeting with external magnets on functionalized nanoparticles could prove as a more efficient means of drug delivery. FROM THE CLINICAL EDITOR: This paper addresses targeted drug delivery with magnetic nanoparticles. The authors demonstrate that a simple external magnetic field is sufficient to target a drug to specific sites in the body without the need for functionalized nanoparticles, at least in selected organs and diseases.