A photosensitized and caspase-responsive multifunctional nanoprobe was designed by assembling a porphyrin, a folate targeting-motif and a dye-labelled peptide in a metal-organic framework (MOF) cage, which significantly increases the singlet oxygen quantum yield of porphyrin by 6.2 times, and achieves high efficient cancer therapy and in situ therapeutic monitoring with caspase-3 activation. The integration of theranostic functions in a single nanocarrier holds great promise in precision cancer diagnosis and treatment.

We review the general principle of the design and functional modulation of nanoscaled MOF heterostructures, and biomedical applications in enhanced therapy.

Integration of a photodynamic therapy platform with a drug-delivery system in a porous structure is an urgent challenge for enhanced anticancer therapy. Here, an amino-functionalized metal-organic framework (MOF), which is useful as efficient delivery vehicle for drugs and provides the -NH group for postsynthetic modification, is chosen and well-designed for cell imaging and chemo-photodynamic therapy. The multifunctional MOF nanoprobe was first assembled with camptothecine drug via noncovalent encapsulation and then bound with folic acid as the targeted element and chlorine e6 (Ce6)-labeled CaB substrate peptide as the recognition moiety and signal switch. The designed MOF probe can realize cathepsin B-activated cancer cell imaging and chemo-photodynamic dual-therapy combining Ce6 as the photosensitizer and the camptothecine drug. Compared with the individual treatment, the dual-functional nanoprobe presents an enhanced treatment efficiency in terms of the time of chemotherapy, laser power, and irradiation time of the photodynamic therapy, which has been confirmed in cancer cells and in vivo assays. This work presents a significant example of the MOF nanoprobe as an intracellular switch and shows great potential in cancer cell targeted imaging and multiple therapies.

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