Discrimination of DNA from RNA with the host–guest complexes of tricyclic basic dyes and cucurbituril†
Cucurbituril (CB) forms strong host–guest complexes with tricyclic basic dyes acridine orange (AO) and pyronine Y (PYY) with a 2 : 1 stoichiometry, respectively. Compared with that of the same dye in dilute solutions, the fluorescence intensity of the inclusion complexes is dramatically quenched due to the dimeric dye formed in the CB cavity. This has been employed to fluorescence detect DNA and RNA. In the case of AO, the dye was observed to leave the cavity of CB and bind to DNA and RNA immediately, accompanying an intense fluorescence increasing effect. The fluorescence intensities were linearly proportional to the amount of DNA and RNA added. When AO was replaced by PYY, the same trend was kept for DNA, while no efficient response can be followed for RNA, providing a potential method to discriminate DNA from RNA. No difference can be observed in the Hela cell staining process under a confocal fluorescence microscope for the tricyclic basic dyes before and after inclusion into CB, demonstrating that the host–guest chemistry of CB does not affect the dyeing behavior and it is a convenient way to solve the autofluorescence background of the tricyclic basic dyes.