Synthesis and application of intercellular Ca2 +-sensitive fluorescent probe based on quantum dots

Abstract

A novel Ca2+-sensitive fluorescent probe was synthesized and characterized with a coupled method that coupled di[2-(N,N-dicarboxylmethyl)amino]ethyl ether (EGTA) to the surface of mercaptoethylamine-modified CdTe quantum dots (CdTe/MA-EGTA QDs). The application of this probe to detect intercellular Ca2+ change in the leaf cells of Arabidopsis thaliana was studied. Results from transmission electron micrographs showed that the particle size of CdTe/MA-EGTA was about 3–4nm; the fluorescent spectrum indicated that the excitation spectral ranged from 350 to 490nm with a narrow and symmetric emission spectral peak at 565nm when excited by 400nm, and capillary electrophoresis demonstrated that CdTe/MA-EGTA was obtained by a coupling reaction. When the detected conditions were set as an excitation wavelength of 514nm and detection wavelength of 561–604nm, the increase of Ca2+ in A. thaliana leaf cells and the rapidly quenching effect of fluorescence signal induced by exogenous treatment of jasmonate acid (JA) could be measured using laser scanning confocal microscopy. The quenching rate of traditional Ca2+-sensitive fluorescent probe Fluo-3 reached about 80% within a minute when exciting at 488nm, which was much faster than the novel fluorescent probe CdTe/MA-EGTA. CdTe/MA-EGTA, however, was better at resisting photo bleaching and was more suitable for long-term tracking and monitoring than Fluo-3.