Extraction issues of paclitaxel in nanocrystals

Nano-carrier systems have become an attractive alternative in the formulation of hydrophobic drugs, and the number of scientific and patent publications per year on nanoparticles has experienced exponential growth since 2000. As these drugs are carried by different nano-carriers, their pharmacokinetics (PK) and biodistribution will be greatly affected. Therefore, PK and biodistribution have become important parameters to evaluate the nano-systems, which are commonly performed by HPLC. This study looks at certain issues in extraction and HPLC analysis encountered in conducting biodistribution studies for paclitaxel (PTX) nanocrystals. We report here for the first time that the extraction efficiency of PTX depends on the nano-carriers, i.e., nanocrystals and nanomicelles. A selected solvent had to be added prior to extraction to totally destruct the nano-carrier structure to resolve this difference. It was also found that the extraction recovery of PTX carried by the nanocrystals was organ specific. Therefore, it will be critical to consider this difference when studying the distribution of drugs in nano-carriers. We hope that our findings would highlight certain issues to be aware of when conducting PK and biodistribution studies for nano-drug carriers.