Abstract
The photophysical and biological properties of two new phenanthroline-based ligand ruthenium complexes were investigated in detail. Their DNA interaction modes were determined to be the intercalation mode using spectra titration and viscosity measurements. Under irradiation, obvious photo-reduced DNA cleavages were observed in the two complexes via singlet oxygen generation. Furthermore, complex 2 showed higher DNA affinity, photocleavage activity, and singlet oxygen quantum yields than complex 1. The two complexes showed no toxicity towards tumor cells (HeLa, A549, and A375) in the dark. However, obvious photocytotoxicities were observed in the two complexes. Complex 2 exhibited large PIs (phototherapeutic indices) (ca. 400) towards HeLa cells. The study suggests that these complexes may act as DNA intercalators, DNA photocleavers, and photocytotoxic agents.
Highlights
The DNA-binding behaviors of small molecules have provoked intense interest because DNA has usually been regarded as the most important drug target for anti-tumor activity [1,2,3,4,5,6,7,8]
Many studies have revealed that changes in the structure of ligands can lead to interesting differences in DNA affinity, reactive oxygen species (ROS) quantum yields, and the DNA photocleavage abilities of ruthenium-based compounds, such as their substituent effect, and the shape and planarity of ligands
Precursor Ru complexes and pni were combined in ethylene glycol and refluxed for 8 h to create the desired ruthenium complex (Scheme 1)
Summary
The DNA-binding behaviors of small molecules have provoked intense interest because DNA has usually been regarded as the most important drug target for anti-tumor activity [1,2,3,4,5,6,7,8]. Ruthenium complexes have been frequently considered for their possible application as important biological agents due to their strong DNA binding abilities, rich photoactivity and constructed coordination geometry [15,16,17,18,19,20,21,22,23,24] Most of these applications are regarded to originate from the high DNA affinity of ruthenium-based compounds. Ruthenium complexes have been found to activate molecular oxygen into singlet oxygen (1 O2 ) and to display favorable singlet oxygen quantum yields This indicates that ruthenium-based compounds have the potential to act as PDT agents. The DNA interaction, DNA photocleavage abilities, cytotoxicities in the dark, and photocytotoxicities of the two complexes were further studied
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