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

A novel Ca 2   + -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 Ca 2   + 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 3–4   nm; the fluorescent spectrum indicated that the excitation spectral ranged from 350 to 490   nm with a narrow and symmetric emission spectral peak at 565   nm when excited by 400   nm, 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 514   nm and detection wavelength of 561–604   nm, the increase of Ca 2   + 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 Ca 2   + -sensitive fluorescent probe Fluo-3 reached about 80% within a minute when exciting at 488   nm, 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.