Meanwhile, tumor-overexpressed enzymes, such as matrix metalloproteases (MMPs), have also been used to trigger PEG detachment.488–491 Matrix metalloprotease 2 (MMP2)-cleavable peptides were utilized to link long PEG chains onto the surface of either a liposomal nanocarrier or a micellar nanopreparation to provide a steric shield for the surface-attached cell-penetrating peptide (TATp) during circulation in the bloodstream. Here, MMP2 is linked to neoplasm.