Fluorescence 6-carboxyfluorescein

Fig. 4 Cleavage of ChemChrome V6 by esterases to yield the green fluorescent carboxyfluorescein...

Liao, R. S. Rennie, R. R Talbot, J. A. Comparative evaluation of a new fluorescent carboxyfluorescein diacetate-modified microdilution method for antifungal susceptibility testing of Candida albicans isolates. Antimicrob. Agents Chemother. 2002, 46, 3236-3242. 

Khanna, P.L., and Ullman, E.F. (1980) 4, 5 -dimethoxy-6-carboxyfluorescein A novel dipole-dipole coupled fluorescence energy transfer acceptor useful for fluorescence immunoassays. Anal. Biochem. 108,156. 

Figure 5 shows two typical core-shell structures (a) contains a metal core and a dye doped silica shell [30, 32, 33, 78-85] and (b) has a dye doped silica core and a metal shell [31, 34]. There is a spacer between the core and the shell to maintain the distance between the fluorophores and the metal to avoid fluorescence quenching [30, 32, 33, 78-80, 83]. Usually, the spacer is a silica layer in this type of nanostructures. Various Ag and Au nanomaterials in different shapes have been used for fluorescence enhancement. Occasionally, Pt and Au-Ag alloys are selected as the metal. A few fluorophores have been studied in these two core-shell structures including Cy3 [30], cascade yellow [78], carboxyfluorescein [78], Ru(bpy)32+ [31, 34], R6G [34], fluorescein isothiocyanate [79], Rhodamine 800 [32, 33], Alexa Fluor 647 [32], NIR 797 [82], dansylamide [84], oxazin 725 [85], and Eu3+ complexes [33, 83]. 

None of the involved species are fluorescent. Therefore, for fluorescence signaling of citrate recognition, carboxyfluorescein is first added to the medium because binding to the receptor in the absence of citrate is possible and causes deprotonation of carboxyfluorescein, which results in high fluorescence. Citrate is then added, and because it has a better affinity for the receptor than carboxyfluorescein, it replaces the latter, which emits less fluorescence in the bulk solvent as a result of protonation. Note that this molecular sensor operates in a similar fashion to antibody-based biosensors in immunoassays. It was succes-fully tested on a variety of soft drinks. 

Tatsu et a/.(106) reported a novel immunosensor using immobilized liposomes doped with carboxyfluorescein and dinitrophenyl (DNP) hapten on the tip of an optical fiber. On complement-mediated immunolysis by anti-DNP-antibody, the fluorescent signal of the liberated carboxyfluorescein was measured. 

Y. Tatsu, S. Yamamura, and S. Yoshikawa, Fluorescent fibre-optic immunosensing system based on complement lysis of liposome containing carboxyfluorescein, Biosens. Bioelectron. 7(10), 741-745 (1992). 

Probes can be differently labeled with hapten labels, for example carboxyfluorescein (6-FAM), digoxigenin (DIG) and biotin can be bound to LNA oligos. The choice of probe label depends on experimental design and the techniques available in the laboratory. The hapten label provides a template for crucial signal amplification since the FITC label on the oligo itself is not sufficient to allow detection in standard epifluorescence. In this study, the fluorescence signal was obtained with the TSA-FITC substrate, which allowed detection of miR-21 and miR-205. 

Fig. 2 Determination of IgE using aptamer-based APCE. (A) Electropherograms obtained for 500 nM of A with 0 (left) and 500 nM (right) IgE. Migration buffer was 10 mM phosphate at pH 7.4, and 10 nM fluorescein was used as internal standard (IS). Injector-to-detector length was 20 cm. (B) Separation of same solutions in 10 mM phosphate at pH 8.2 and gravity-induced flow of 0.02 cm/s. (C) Solutions of 300 nM of A with no IgE (left), 300 nM IgE (middle), and 1 nM IgE (right) were separated with injector-to-detector length of 7 cm. After 48 s of separation, a vacuum was applied to the outlet to rapidly pull the complex to the detector. 4(5)-Carboxyfluorescein (5 nM) was used as internal standard. Fluorescent signal scale for the 1 nM IgE sample is expanded by 10-fold relative to the other electropherograms. (From Ref. 26.)...

Chromophoric change. UV/vis- or fluorescent-active and water-soluble chromophores such as pyranine and carboxyfluorescein are encapsulated in... 

Membrane permeabilization activity of peptides is currently measured by the use of artificial membrane bilayers, such as liposomes or erythrocytes. The hposome leakage assay can be performed by using spectrofluorimetry with a concentration-dependent quenching of a dye (calcein, carboxyfluorescein) encapsulated in liposomes. Disruption of hposomes in the presence of peptide-inducing leakage will lead to an increase in the fluorescence intensity of the liposome solution. Erythrocyte lysis assay is based on the absorption of hemoglobin, which can be measured once released into the extracellular medium upon erythrocyte lysis in the presence of peptide. 

Liposomes applied on the skin were also investigated for their delivery proprieties to the pilosebaceous units [15,23 28]. The in vitro skin penetration behavior of carboxyfluorescein incorporated in multilamellar liposomes (phosphatidylcholine cholesterol phosphatidylser-ine) and in another four nonliposomal systems (HEPES pH 7.4 buffer 5% propylene glycol 10% ethanol and 0.05% sodium lauryl sulfate) was studied by Lieb et al. [25]. Using two fluorescent techniques the authors found a higher accumulation of the probe within skin follicles when delivered from liposomes [25], Further, in an interesting setup of in vitro and in vivo experiments in mice, Hoffman s group observed liposomal delivery of the active Lac-Z gene and its expression mostly in the hair follicles [26,28]. 

By combining the concentration and temperature gradients, the fluorescent intensity of a dye (carboxyfluorescein) was measured to illustrate the capability of the device to obtain three-dimensional information (see Figure 3.26) [447]. In a subsequent study, measurements of the dephosphorylation of a fluorogenic substrate were performed simultaneously at different temperatures in order to extract the activation energy information [448]. 

FIGURE 3.26 Three-dimensional plot of fluorescence intensity of carboxyfluorescein dye molecules in aqueous solution as a function of their concentration (0.00715—0.266 pM) and temperature (28-74°C). The plot was mapped over 110 data points (excluded for clarity) gained from 11 temperature measurements across 10 microchannels [447]. Reprinted with permission from the American Chemical Society. 

FIGURE 24.2 Uptake of the fluid-state PC (a) and the gel-state HPC (b) by the skin after a 3 h exposure as visualized by the fluorescent dye carboxyfluorescein.24... 

---