Acid-Responsive Nanoparticles Expand To Deliver Drugs

Polymeric nanoparticles that expand to several hundred times their original size in response to a shift in pH show promise as an anticancer drug delivery system (J. Am. Chem. Soc., DOI: 10.1021/ja807416t). Mark W. Grinstaff of Boston University, Yolanda L. Colson of Brigham & Women's Hospital, in Boston, and colleagues designed the polymer nanoparticles specifically to encapsulate drug molecules. The nanoparticles are composed of cross-linked monomers studded with 2,4,6-trimethoxybenzaldehyde protecting groups. In response to a drop in pH—a condition that mimics cellular environments—the particles shed the protecting groups to expose hydrophilic hydroxyl groups. The particles then expand as they absorb water, spilling out their contents in the process. The researchers tested the particles' drug-releasing ability in mice that had been injected with doses of lung cancer cells. Mice injected with nanoparticles loaded with the anticancer drug paclitaxel developed no tumors, whereas mice that were given an equivalent dose of paclitaxel via the standard method, dissolved in an oil base, developed large tumors after 14 days.