Cell image based on reassembly of the host-guest complex of CB[8]

Being a relatively new class of host molecule, cucurbit[8]uril (CB[8], Scheme 1) has been studied extensively and used in many areas such as molecular machine, molecular switches and molecular wires etc[1–3]. While, acridine orange (AO)[4] is capable of cell-permeable, and interacts with DNA and RNA by intercalation or electrostatic attractions respectively, so it is widely used for cell staining, DNA intercalator, cell cycle determination and transmembrane pH-gradient probe etc. Reassembly of the host-guest complex between AO and CB[8] with DNA/RNA has been studied and employed to fluorescent detect DNA/RNA. The dye is observed to leave the cavity of CB[8] and reassemble (bind) with DNA/RNA immediately, accompanying a strong fluorescence increasing effect, the fluorescence intensities are linearly proportional to the amount of DNA/RNA added, the sensitivity can be improved because the background signals of AO can be significantly decreased due to the dimeric dye formed in CB[8] cavity.[5] When AO is replaced by another dye pyronine Y (PYY), no efficient response can be observed on RNA, which can be used to distinguish DNA from RNA. Not much difference can be observed on fluorescence ratio image of Hela cells for the tricyclic basic dyes before and after including of CB[8], demonstrating a potential application of this method, which can be employed as a convenient and efficient way, to solve autofluorescence problem of the tricyclic basic dyes instead of normally complicated organic synthesis.