Controlled drug-release systems which integrate specific biological stimulation with multifunctional nanomaterial complexes have received considerable attention due to their promising biomedical applications in detection, diagnosis, and therapy. In their Full Paper on page 1381 ff., B. G. Xing et al. demonstrate such a novel enzyme responsive silica iron oxide magnetic hybrid nanoparticle complex, in which an antitumor-drug-conjugated enzyme-cleavable peptide is covalently tethered on the surface of nanoparticles through “click chemistry”. This enzyme-responsive nanoparticle conjugate can selectively induce intracellular drug delivery in the tumor cells with high cathepsin B expression. It also provides the platform to real-time monitor the cellular trafficking process by using various imaging techniques.