Multifunctional hierarchical nanohybrids perform triple antitumor theranostics in a cascaded manner for effective tumor treatment

Gene therapy based on transfection of RNAs/DNAs offers tremendous promise for tumor treatment. However, the relatively weak therapeutic efficiency of current genetic nanohybrids in vivo has limited the application of this strategy. Herein, we fabricated multifunctional core-shell-corona nanohybrids by combining cascaded theranostics for enhanced gene therapy. The nanohybrids consist of polydopamine-modified Fe3O4 nanoparticles as core, anti-miRNA-21 oligonucleotides (anti-miRNA) strands as shell, and doxorubicin (DOX)-conjugated DNA-8pb (DOX-DNA-8bp) as corona. The polydopamine/Fe3O4 core not only serves as an active agent for local photothermal therapy under NIR irradiation, but it also provides magnetic targeting to tumor tissue for accurate treatment, which could enhance the therapeutic effect and reduce the undesired side effects to healthy tissues. The DOX-DNA-8bp corona was grafted on the anti-miRNA shell through base pairing, which could be replaced by overexpressed miRNA-21 in tumor cells due to the strong interaction between miRNA-21 and anti-miRNA, resulting in tumor-specific gene therapy through tumorigenic miRNA-21 consumption and tumor selective chemotherapy through miRNA-21-triggered DOX-DNA-8bp release in tumor cells. Moreover, the intelligent controlled release system can gradually stop the release of DOX to prevent side effects caused by drug overdose, once sufficient damage of tumor cells has occurred, due to the downregulation of miRNA-21. The results of both in vitro and in vivo analyses showed that the nanohybrids combining cascaded chemo-photo-gene therapy could effectively inhibit tumor growth, promote the survival of tumor-bearing mice, and show no visible adverse effects on these mice, resulting in a promising nanoplatform for tumor treatment. Gene therapy based on transfection of RNAs/DNAs offers tremendous promise for cancer treatment. However, the relatively weak therapeutic efficiency of current genetic nanovectors in vivo that results in insufficient tumor targeting and easy decomposition/elimination of RNAs/DNAs during therapy has limited its application. Although some approaches have combined photothermal agents or antitumor drugs with RNA/DNA nanocarriers to achieve better treatment, the spatiotemporal differences in photothermal therapy, chemotherapy, and gene therapy using current nanohybrids may hinder their synergistic effect. In the present study, we fabricated multifunctional core-shell-corona nanohybrids (Fe3O4@PDA@a