Syntheses, spectroscopic characterization and application to DNA determination of novel fluorescent pyridophenazine derivatives

• A series of alkylamino substituted pyridophenazine derivatives were efficiently synthesized.
• The absorption and emission properties of the pyridophenazine derivatives were studied.
• The DNA intercalation was examined for an aminoethylpiperidine substituted pyridophenazine.
• The limit of detection for DNA determination of the aminoethylpiperidine substituted pyridophenazine was determined.

A series of pyridophenazine derivatives were synthesized and characterized as DNA intercalating fluorophores. These pyridophenazines showed absorption maxima at ca. 450 nm, and some compounds exhibited strong fluorescence at ca. 530 nm with excellent quantum yields in ethyl acetate solution. DNA binding properties of these pyridophenazines to calf thymus DNA (CT DNA) were studied in phosphate buffered saline at pH 7.4 by means of fluorescence titration. All compounds showed high binding affinity toward CT DNA with binding constant values in the range of 106 M−1, with fluorescence enhancement upon their binding to CT DNA. The fluorescent aminoethylpiperidine substituted pyridophenazine was employed as a sensitive agent for DNA determination with a limit of detection of 65 nM over a linear range of 100–1000 nM. The fluorescence titration and Top1 mediated DNA unwinding assay showed that this derivative exhibited DNA intercalation.

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