The study by F. Collette et al. on page 176 focuses on a new flexible approach for the synthesis of drug delivery submicroparticles functionalized by several molecules (therapeutic agent, fluorescent dye, etc.). Particles are obtained by copolymerization of norbornene with a functionalized-norbornenyl poly(ethylene oxide) macromonomer in dispersion. An accumulation of the drugs carriers in tumor tissues is due to the enhanced permeability and retention effect. Nanoparticles are then internalized in human cells by endocytocis. During this intracellular mechanism, any bioactive molecules found at the surface of the particles, which possesses an acido-sensitive bond, can be released by acidic hydrolysis. Efficient nanoparticle endocytosis has been observed by microscopy in mesothelioma and adenocarcinoma cells using rhodamine B as fluorescent dye.