Enzyme-responsive multifunctional magnetic nanoparticles for tumor intracellular drug delivery and imaging.

Enzyme-responsive, hybrid, magnetic silica nanoparticles have been employed for multifunctional applica- tions in selective drug delivery and in- tracellular tumor imaging. In this study, doxorubicin (Dox)-conjugated, enzyme-cleavable peptide precursors were covalently tethered onto the sur- face of uniform silica-coated magnetic nanoparticles through click chemistry. This enzyme-responsive nanoparticle conjugate demonstrated highly efficient Dox release upon specific enzyme in- teractions in vitro. It also exhibits mul- tiple functions in selective tumor intra- cellular drug delivery and imaging in the tumor cells with high cathepsin B expression, whereas it exhibited lower cytotoxicity towards other cells without enzyme expression.