Nanoparticles that respond to changes in pH have the ability to identify tumor cells over normal cells or specific intracellular compartments for the targeted delivery of drugs.

Jinming Gao and colleagues, UT Southwestern Medical Center at Dallas, USA, have developed micellar nanoparticles that target the endocytic organelles in living cells. Selective targeting of different endocytic compartments by is difficult due to short nanoparticle residence times (on the order of minutes) and the small pH differences in these compartments (less than 1 pH unit between early endosomes and lysosomes). The nanoparticles created by Gao’s team have overcome these difficulties by having a fluorescence emission that can be switched on or off quickly (<5 ms) and which is triggered by very small changes in pH (0.25 pH units).

• Tunable, Ultrasensitive pH-Responsive Nanoparticles Targeting Specific Endocytic Organelles in Living Cells
  K. Zhou, Y. Wang, X. Huang, K. Luby-Phelps, B. D. Sumer, J. Gao,
  Angew. Chem. Int. Ed. 2011.
  DOI: 10.1002/anie.201100884