Metal organic framework coated MnO 2 nanosheets delivering doxorubicin and self-activated DNAzyme for chemo-gene combinatorial treatment of cancer.

The RNA-cleaving DNAzyme (DZ) holds promising potential for RNA interference (RNAi) applications and is favored over siRNA owing to its high chemical stability, biocompatibility, predictable activity, and substrate versatility. However, its pharmaceutical applications for disease treatment are limited by the requirement of metal cofactor for activation, as well as the lack of effective co-delivery systems to combine with other therapeutic modalities. Herein, we designed and constructed metal organic framework (MOF) coated MnO ₂ nanosheets to realize the co-delivery of a survivin inhibiting DZ and doxorubicin (DOX) for chemo-gene combinatorial treatment of cancer. In our design, the DOX was adsorbed on MnO ₂ planar surface, and the DZ was loaded into the MOF shell layer through the coordination between Mn ²⁺ and tannic acid. The nano-system could stably encapsulate the payloads under physiological condition, but rapidly degraded after endocytose into tumor cells in response to intracellular stimuli, resulting in triggered drugs release. Notably, the coreleased Mn ²⁺ could act as metal cofactor for effective DZ activation. Both in vitro and in vivo studies have demonstrated the enhanced anti-tumor efficacy of the nanosystem, with co-contributions from anti-neoplastic DOX, survivin silencing effect of DZ, and to some extent, ROS generation by Mn ²⁺ . This work provides an ingenious strategy to address the key limitation of DZ for RNAi applications and realize the combination of DZ with other therapeutic modalities, in which the DZ can be in-situ activated for target gene silencing.
Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
(Copyright © 2020 Elsevier B.V. All rights reserved.)