Targeted for drug delivery

The concept of targeted drugs is not new, but dates back to 1906 when Ehrlich(1) first postulated the 'magic bullet'. The durability of this concept is a strong indication of its appeal, but the 'magic bullet' continues to be a challenge to implement in the clinic. The challenge has been on three fronts: finding the proper target for a particular disease state; finding a drug that effectively treats this disease; and finding a means of carrying the drug in a stable form to specific sites while avoiding the immunogenic and nonspecific interactions that efficiently clear foreign material from the body. Nanoparticles are potentially useful as carriers of active drugs and, when coupled with targeting ligands, may fulfill many attributes of a 'magic bullet'. This review focuses on targeted drug delivery using nanoparticles as a modality that couples a ligand to a nanosized, drug-loaded vehicle as a potential means to achieve increased efficacy of a drug at the site of interest.