Intracellular pH-induced fluorescence used to track nanoparticles in cells.

A nanoparticle with pH-induced fluorescence was reported for intracellular tracking. The fluorescence was evoked by the isomerization of the ring-closed form spiropyran (SP) to the ring-open form merocyanine (MC) in the weak acidic environment of cells. The SP-MC switch accelerated the dissociation of nanoparticles to trigger the release of trapped paclitaxel.