pH-Triggered Doxorubicin Delivery Based on Hollow Nanoporous Silica Nanoparticles with Free-Standing Superparamagnetic Fe3O4 Cores

Superparamagnetic core/shell nanoparticles, composed of a free-standing Fe3O4 magnetic core inside a hollow nanoporous silica shell, have been synthesized, and their structures and magnetic and drug release behavior were systematically investigated. The hollow/nanoporous silica shells, containing secondary amine groups, were functionalized with 1, 2-cyclohexanedicarboxylic anhydride as click linkers, producing pH-sensitive amides and terminal carboxylic groups for the conjugation and release of the anticancer drug doxorubicin. The results show that the effective release occurred at pH 5 and was 3 times higher than that at pH 7.4. The kinetics of release was assumed as a Fickian diffusion process and fitted by the Higuchi model to uncover an intrinsic relationship of the released amount with time, temperature, and pH.