Ethylene glycol modified 2-(2¡¬-aminophenyl)benzothiazoles at the amino site: The excited-state N-H proton transfer reactions in aqueous solution, micelles and potential application in live-cell imaging
Journal
Methods and Applications in Fluorescence
Journal Volume
4
Journal Issue
1
Date Issued
2016
Author(s)
Liu, B.-Q.
Chen, Y.-T.
Chen, Y.-W.
Chung, K.-Y.
Tsai, Y.-H.
Li, Y.-J.
Chao, C.-M.
Liu, K.-M.
Tseng, H.-W.
Abstract
Triethylene glycol monomethyl ether and poly(ethylene glycol) monomethyl ether modified 2-(2'-aminophenyl)benzothiazoles, namely ABT-P3EG, ABT-P7EG and ABT-P12EG varied by different chain length of poly(ethylene glycol) at the amino site, were synthesized to probe their photophysical and bio-imaging properties. In polar, aprotic solvents such as CH2Cl2 ultrafast excited-state intramolecular proton transfer (ESIPT) takes place, resulting in a large Stokes shifted tautomer emission in the green-yellow (550 nm) region. In neutral water, ABT-P12EG forms micelles with diameters of 15 �� 3 nm under a critical micelle concentration (CMC) of ~80 �gM, in which the tautomer emission is greatly enhanced free from water perturbation. Cytotoxicity experiments showed that all ABT-PnEGs have negligible cytotoxicity against HeLa cells even at doses as high as 1 mM. Live-cell imaging experiments were also performed, the results indicate that all ABT-PnEGs are able to enter HeLa cells. While the two-photon excitation emission of ABT-P3EG in cells cytoplasm shows concentration independence and is dominated by the anion blue fluorescence, ABT-P7EG and ABT-P12EG exhibit prominent green tautomer emission at > CMC and in part penetrate to the nuclei, adding an additional advantage for the cell imaging.
Type
journal article