Drug resistance is a major obstacle to the efficient therapy of drug-resistant cancer. To overcome this problem, we constructed a multifunctional DNA origami-based nanocarrier for codelivery of a chemotherapeutic drug (doxorubicin, Dox) and two different antisense oligonucleotides (ASOs; B-cell lymphoma 2 (Bcl2) and P-glycoprotein (P-gp)) into drug-resistant cancer cells for enhanced therapy. To increase the targeting ability of origami, staple strands with 5′-end extended MUC1 sequences were used in the preparation of aptamer-functionalized origami carrying ASOs (Apt-origami-ASO). Dox-loaded Apt-origami-ASO (Apt-Dox-origami-ASO) was prepared by electrostatic adsorption of Dox in origami. Atomic force microscopy (AFM) images demonstrated the successful preparation of Apt-origami-ASO. In vitro studies showed that the Apt-Dox-origami-ASO (Apt-DOA) could controllably release Dox in pH 5.0 phosphate-buffered saline (PBS) buffer and release ASOs in response to glutathione. Further experiments revealed that the origami could protect ASOs against nuclease degradation in 10% FBS. Confocal imaging showed that the Apt-DOA nanocarrier could efficiently enter the Hela/adriamycin (ADR) cells and escape from lysosomes for codelivery of Dox and ASOs into the cytoplasm. The quantitative reverse transcriptase polymerase chain reaction (qRT-PCR) and western blot assays testified the efficient silencing of Bcl2 and P-gp mRNA and downregulation of the corresponding protein expressions by Apt-DOA in Hela/ADR cells. Moreover, with the synergetic effect by codelivery of multi-ASOs and Dox, the anticancer assay showed that Apt-DOA could circumvent multidrug resistance and significantly enhance cancer therapy in Hela/ADR and MCF-7/ADR cells. Hence, this multifunctional origami-based codelivery nanocarrier presents a new strategy for efficient therapy of drug-resistant cancer.

Multiple drug resistance is a persistent obstacle for efficient chemotherapy of cancer. Herein, we report a novel drug delivery platform. A zeolitic imidazole framework-8 (ZIF-8) film with a few nanometer thickness was in situ synthesized on the surface of carboxylated mesoporous silica (MSN-COOH) nanoparticles (NPs) for pore blocking and efficient loading of small interfering RNAs to fabricate a pH-responsive drug delivery system. The ZIF-8 film could convert the charge of MSN-COOH from negative to positive for efficient loading of siRNA via electrostatic interactions and protect siRNA from nuclease degradation. The positively charged ZIF-8 film facilitates cellular uptake and endo-lysosome escape of the NPs. In addition, the ultrathin ZIF-8 film can decompose in the acidic endo-lysosome and trigger the intracellular release of siRNAs and chemotherapeutic drugs, leading to a significantly enhanced chemotherapeutic efficacy for multidrug-resistant cancer cells including MCF-7/ADR and SKOV-3/ADR cells as demonstrated by the confocal laser scanning microscopy image, cell viability assay, Annexin V&PI staining, and flow cytometry. This approach provides a promising strategy for pH-triggered, stimuli-responsive delivery of nucleic acid drugs and chemotherapeutic agents with remarkably enhanced chemotherapeutic efficacy.

The enzymatic amplification strategy in living cells faces challenges of highly efficient intracellular codelivery of amplification reagents including DNA polymerase. In this work, we develop biomineralized metal−organic framework nanoparticles (MOF NPs) as a carrier system for intracellular codelivery of ϕ29 DNA polymerase (ϕ29DP) and nucleic acid probes and realize a polymerization amplification reaction in living cells. A pH-sensitive biodegradable MOF NP of zeolitic imidazolate framework-8 (ZIF-8) is utilized to encapsulate ϕ29DP and adsorb nucleic acid probes. After uptake into cells, the encapsulated ϕ29DP and surface-adsorbed DNA probes are released and escaped from endolysosomes. In the presence of ϕ29DP and deoxyribonucleotide triphosphates (dNTPs), the intracellular miRNA-21 triggers a rolling circle amplification (RCA) reaction and the autonomous synthesized Mg 2+ -dependent DNAzyme cleaves the fluorogenic substrate, providing a readout fluorescence signal for the monitoring of miRNA-21. This is the first example of the intracellular RCA reaction in living cells. Therefore, the proposed method provides new opportunities for achieving enzymatic amplification reaction in living cells.