From the "Magic Bullet" to Advanced Nanomaterials for Active Targeting in Diagnostics and Therapeutics

Paul Ehrlich, recipient of the Nobel Prize in Medicine in 1908 for his fundamental contributions to the understanding of the immune system, introduced the visionary concept of "magic bullet," referring to an ideal therapeutic agent that selectively targets a pathogen, a cancer cell, or a toxin at sufficiently low concentrations that prevent any harm to the healthy cells of the patient. Many years later and primarily motivated by the urgent need to improve the diagnosis and chemotherapy of cancer, the conceptual revolution introduced by Ehrlich became the moto of drug designers and it was also embraced by the nanomedicine field, paving the way for the design of a plethora of innovative nanomaterials that owing to their small size and uniquely fine-tuned shape and surface properties target specific cell populations, tissues and organs by different passive and active pathways. This chapter will overview the most outstanding hallmarks in this thrilling way to realizing his pioneering vision with focus on the developments done in cancer, a disease that owing to its broad incidence worldwide became the flagship of the nanomedicine field.