Adaptive Size Evolution of an MOFs-in-MOF Nanovehicle for Enhanced Nucleus-Targeted Tumor Chemotherapy

A metal–organic frameworks (MOFs)-in-MOF nanovehicle (160 nm), which was constructed with newly prepared ultrasmall Cu(I)Cu(II)-BTC MOFs (UCMs, 2.95 nm) loaded with doxorubicin (DOX) and a nuclear localization signal (NLS) peptide as multicores (UCMDNs) and ZIF-8 as the shell MOF, was proposed to cross layers of biological barriers with adaptive size evolution capacity for achieving efficient nucleus-targeted drug delivery. It first enhanced tumor tissue penetration through its larger nanosize effect. Then the acidic tumor environment made the ZIF-8 shell degrade, releasing small-sized UCMDNs to enter into the cell and into the nucleus under the guidance of NLS. Furthermore, due to the distinct surface structural characteristics of UCMs, UCMDNs remained stable in the cytoplasm and collapsed in the nucleus due to the DOX–DNA interaction to deliver DOX precisely. It showed superior performance in the nucleus-directed delivery of DOX (delivery efficiency up to 56.7%) and a high tumor growth inhibition rate (96.4%), offering promising prospects in tumor chemotherapy.