Idarubicin/mithramycin-acridine orange combination drugs co-loaded by DNA nanostructures: Different effects of intercalation and groove binding on drug release and cytotoxicity

Abstract

The co-loading of chemotherapy-phototherapy (CTPT) combination drugs by aptamer-targeted DNA nanostructures has significant advantages in improving anticancer effects and overcoming the multidrug resistance of cancer cells. The different binding modes of drugs to DNA nanostructures may impact CTPT therapy. Here, the anti-drug resistance effects of idarubicin (IDA) or acridine orange (AO) as single drug, as well as IDA/mithramycin (MTR) dimers ((MTR)2Zn2+) + AO combination drugs loaded by AS1411-tethered DNA nanotrains (AS1411NTrs), were studied. The intercalative binding mode between IDA/AO and AS1411NTrs was verified through measurements of viscosity, changes in melting temperature, and potassium iodide quenching. A series of thermodynamic parameters such as the binding constant and the number of binding sites were obtained through fluorescence spectroscopy, isothermal titration calorimetry, and differential scanning calorimetry. The high binding constants and the number of binding sites indicated that AS1411NTrs had a high loading capacity for IDA and AO. An in vitro release study showed that the release rate and release model of IDA/(MTR)2Zn2+/AO in the binary and ternary systems with or without deoxyribonuclease I were related to their binding mode and order of addition. An in vitro cytotoxicity study proved that the cytotoxicity and synergistic effects of the three drugs to human breast cancer MCF-7 cells and multidrug-resistant MCF-7/ADR cells were enhanced due to loading of AS1411NTrs. The IDA/(MTR)2Zn2+ + AO combination drugs could more obviously enhance apoptosis of MCF-7/ADR cells as confirmed by cell apoptosis assays. The cell uptake study demonstrated that IDA/(MTR)2Zn2+/AO loaded by AS1411NTrs was mainly concentrated in the nucleus of MCF-7/ADR cells. This work will provide theoretical information for combination therapy of IDA/(MTR)2Zn2+ and AO based on DNA nanostructures.