Fluorescence Turn-on of Tetraphenylethylene Derivative by Transfer from Cyclodextrin to Liposomes, HeLa Cells, and E. coli

Herein, trimethyl-β-cyclodextrin (TMe-β-CDx) and γ-cyclodextrin (γ-CDx) could dissolve a tetraphenylethylene derivative (TPE−OH₄) in water through high-speed vibration milling. The fluorescence intensity of the TMe-β-CDx−TPE−OH₄ complex was much higher than that of the γ-CDx−TPE−OH₄ complex, as the rotation of the central C=C double bond of TPE−OH₄ after photoactivation was inhibited in a smaller TMe-β-CDx cavity in comparison with the γ-CDx cavity. In contrast, the fluorescence intensity of the γ-CDx−TPE−OH₄ complex was very weak; nevertheless, it increased after the addition of liposomes due to the transfer of TPE−OH₄ from the γ-CDx cavity to the lipid membrane as a “turn-on” phenomenon. Furthermore, to apply temperature sensor, it was demonstrated that the fluorescence intensity in the liposomes depended on the phase-transition temperature. By using the fluorescence turn-on phenomenon, TPE−OH₄ could detect the presence of HeLa cells and E. coli by fluorescence.