Targeting of injectable drug nanocrystals.

"Nano" drug delivery carriers are established technologies for improving the therapeutic index of chemotherapeutic drugs and overcoming formulation challenges of poorly water-soluble compounds. Two important remaining challenges, however, are the need to formulate drugs on a case-by-case basis (due to the specific chemistry of each drug) and the difficulty associated with transporting large amounts of drug specifically to the site of the tumor (in part because of moderate to poor drug loadings). One of the most valuable "nano" opportunities in this field is to address these challenges by creating nanocarriers composed of the drug itself, in the form of so-called nanocrystals. However, "nano" creates both opportunities and challenges for targeted drug delivery, which are critically discussed in both in vitro and in vivo settings in this contribution.