It is of great fundamental significance and practical application to understand the binding sites and dynamic process of the interaction between doxorubicin (DOX) and DNA molecules. Based on the Confocal Raman spectroscopy, the interaction between DOX and calf thymus DNA has been systemically investigated, and some meaningful findings have been found. DOX molecules can not only interact with all four bases of DNA molecules, i.e., adenine, thymine, cytosine, guanine, and phosphate, but also affect the DNA conformation. Meanwhile, the binding site of DOX and its derivatives such as daunorubicin and epirubicin is certain. Furthermore, the interaction between DOX and DNA molecules is a dynamic process since the intensities of each characteristic peaks of the base, e.g., adenine, cytosine, and phosphate, are all regularly changed with the interaction time. Finally, a dynamic mechanism model of the interaction between DOX and DNA molecules is proposed; that is, there are two kinds of interaction between DOX and DNA molecules: DOX-DNA acts to form a complex, and DOX-DOX acts to form a multimer. The two effects are competitive, as the former compresses DNA molecules, and the latter decompresses these DNA molecules. This work is helpful for accurately understanding and developing new drugs and pathways to improve and treat DOX-induced cytotoxicity and cardiotoxicity.

Bendamustine (BENDA) has both alkylating and purinergic antitumor activities and remains effective in some cancers that have developed drug resistance, and there are few studies on the interaction mechanism of BENDA with DNA. In this paper, the interaction mechanism between BENDA and calf thymus DNA (ctDNA) was systematically investigated at the single molecular level, mainly by using ultraviolet-visible spectroscopy (UV-vis), Confocal Raman spectroscopy, and molecular docking. In UV-vis absorption spectroscopy experiments, the effects of ctDNA solution concentration, temperature, time and Na+ ions on the spectral production were investigated, respectively, and the experimental results showed that the interaction mode between BENDA and ctDNA was external bonding, i.e., groove binding and electrostatic binding. In addition, the disappearance and shift of the corresponding characteristic peaks in the Raman peaks indicate that BENDA interacts mainly with the phosphate backbone and base G of the ctDNA molecule, and causes some shifts in other bases and deoxyribose. Molecular docking simulations show that BENDA binds in the minor groove region of DNA and that the N and O atoms in the BENDA structure form intermolecular hydrogen bonds with base G, respectively. The results of this paper help to understand the mechanism of action of anti-cancer drugs and provide some reference for the development of new drugs with less toxic side effects.