In many fields of chemistry and molecular biology, DNA detection is essential in order to study different phenomena. This can be achieved by dyes techniques employingfluorescent probes. The most commonly used dye is ethidium bromide (EtBr). It is an intercalating agent which is also known for its toxicity andmutagenicity. So, the development of fluorescent probes capable to interact with DNA has attracted much attention. Several ligands interact with DNA through covalent and electrostatic binding or intercalation. Compounds with rigid and planar structures are good candidates for DNA intercalation. In addition, some of these compounds are used in chemotherapeutic treatments to inhibit DNA replication in rapidly growing cells.
In this work, we synthetizedthioxoimidazolidin-4-one derivatives (TH, 1a-cand 2a-c, figure 1), studied their luminescence properties and evaluated thepossibility of their application in the detection of double stranded DNA(dsDNA). These compounds are good candidates as fluorescent probes due to theirplanar structure and the heteroatoms that may form hydrogen bonds.
The fluorescent profile wasexamined in the absence and presence of fish dsDNA. Solutions of the sampleswere prepared in DMSO rising a final concentration of 0.3 mM. Ethidium bromidewas analyzed at a lower concentration of 15µM due to its high fluorescenceemission. All the analyses andincubation times were performed at a controlled temperature (30°C). Thecomparative results for the unsubstituted compounds (1a and 2a) are shown in figure 2 togetherwith the spectrum for ethidium bromide at the concentration needed to reachsimilar emission intensities ([TH]/[EtBr]=20).
Compound 1a presents a rather modest fluorescence emission which somewhatincreases after incubation with dsDNA. In contrast, 2a, whose fluorescence emission is comparable to 1a, rises 20 times after 4 h ofincubation with dsDNA. As it is possible to see, compound 2a interacts better with DNA because it has a bigger planarstructure. In addition, compounds 1present tautomerism which is a well-known mechanism of fluorescence deactivation.
In spite of the higherconcentration of the fused‑thiohydantoin derivatives compared to ethidiumbromide (ratio of concentrations ~20), we believe that thepresenting compounds could perform as fluorescent probes because their emissionappear well within the visible region besides of its reduced toxicity.
