Figure 2.

Schematic diagram of pH responsive mesoporous silica nanoparticle for the sequential delivery of CPT and 5-fluorouracil. The pores in the mesoporous silica nanoparticles (MCM-41) were loaded with CPT (Drug 1). Then, the pores were capped with 5-fluorouracil derivative (Drug 2) to prevent premature release at physiological pH through a stable H bond created with the Stalk located on the surface of the MCM-41. At acidic pH, the protonation of Stalk triggers the release of 5-fluorouracil followed by the release of CPT through disruption of Stalk-cap bonds. Reproduced from [141] with permission from The Royal Society of Chemistry.