Scheme 1. Schematic Illustration of Coassembled PSFG Micelle and GSH Dual-Responsive Drug Release and Bioimaging.

The co-assembly of two independent polymers into PSFG micelles results in a “turn off” of the fluorescence and ¹⁹F MR signals. Once taken up by tumor cells, PSFG micelles are disintegrated by highly expressed GSH in the cytoplasm. When FCy7 and GEM are released, the “OFF” to “ON” changes in the fluorescence, and ¹⁹F nuclear magnetic resonance (NMR)/MRI signals can not only reflect the content of GSH in tumor cells but also visualize the process of GEM release. GEM is phosphorylated by the action of deoxycytidine kinase (DCK), which inhibits DNA synthesis and induces apoptosis.