Dyes, photostability

The excitation and emission maxima of Alexa Fluor 647, 680, and 750 (the numbers indicate approximate absorption maxima in nanometers), and the molar absorptivities are in the same range as those for Cy5, Cy5.5, and Cy7, but Alexa Fluor dyes are reported to have major advantages in terms of their photostability,... 

The photostability of ring-substituted squaraines, especially dicyanomethylene-and f/no-squaraines is, in general, higher compared to oxo-squaraines and cyanines (Fig. 2). Increasing of the number of sulfo groups further improves the photostability of these dyes the photostability for hydrophilic dyes increases in the order 10b < 13b < Cy5 < 41h < 41i 41j < 41f < 41g [18]. Thio-squaraine dyes... 

Compared to oxo-squaraines or other ring-substituted squaraines, amino-squaraines 39 [45, 52, 112] have ionic character, similar to open-chain cyanine dyes, and due to the positive net charge, these dyes are to some extend water-soluble. Amino-squaraines absorb and emit at longer wavelength than the corresponding oxo-squaraines the absorption maxima are between 650-710 nm (eM = 85,000-300,000 M-1cm-1) [45, 112], The increase in solvent polarity is accompanied by a hypsochromic shift of the absorption. Amino-squaraine dyes are potentially used as fluorescent probes but because their photostability is inferior to those of oxo-squaraines and other ring substituted squaraines of similar structure, their applications are rather limited. 

The commercially available dicyanomethylene squaraine dye Seta-670-mono-NHS showed extremely low blinking effects and good photostability when used in single-molecule studies of multiple-fluorophore labeled antibodies [113]. Seta-670-mono-NHS and Seta-635-NH-mono-NHS were covalently labeled to antibodies and used in a surface-enhanced immunoassay [114]. From the fluorescence intensity and lifetime changes determined for a surface that had been coated with silver nanoparticles, both labeled compounds exhibited a 15- to 20-fold... 

Kim SH, Hwang SH (1997) Synthesis and photostability of functional squarylium dyes. Dyes Pigm 35 111-121... 

Song B, Zhang Q, Ma WH, Peng XJ, Fu XM, Wang BS (2009) The synthesis and photostability of novel squarylium indocyanine dyes. Dyes Pigm 82 396-400... 

Fluorophores containing 4,4-difluoro-4-bora-3a,4a-diaza-s-indacene as a core skeleton are commonly designated as BODIPY fluorophores. Due to their useful photophysical properties including high fluorescence quantum yields, high molar absorption coefficient, narrow absorption and emission band width, and their high photostability [50], BODIPY dyes are proven to be extremely versatile and useful in many biological applications Fig. 11 [68]. 

The indole- and benzindole-cyanine dyes illustrated in Scheme 6 are used by many major manufacturers in optical disk recording applications. These types of dye tend to be more light-stable than many other readily synthesized polymethine dyes. To increase the photostability, the dyes are used in combination with various types of stabilizers such as nickel dithiolato complexes and selected tertiary aromatic amine compounds.199 The application of cyanine dyes for optical storage media was primarily developed in Japan203 and several dyes and compatible stabilizers are commercially available in pure form from Japanese suppliers.199... 

Phthalocyanine-based dyes are especially useful for CD-R, as the chromophore absorption band falls in the desirable spectral range, and they are noted for excellent photostability. Unlike cyanine dyes, phthalocyanines tend to have very poor solubility, particularly in solvents such as alcohols and aliphatic hydrocarbons (which do not attack polycarbonate and are therefore used for spin coating). Therefore, the main barrier to the wider use of these dyes is the relatively high cost of synthesizing soluble derivatives. Suitable modifications to the Pc core which have been developed, notably by Mitsui Toatsu, are shown in Scheme 7. The bulky R groups reduce undesirable molecular association (which in turn lower the extinction coefficient and hence reflectivity), whereas partial bromination allows fine-tuning of the film absorbance and reflectivity. The metal atom influences the position of the absorption band, the photostability, and the efficiency of the radiationless transition from the excited state.199 This material is marketed by Ciba as Supergreen.204... 

The members of Wolfbeis team constructed an optical sensor for ammonia-based on ion pairing76. They immobilized pH-sensitive dye (bromophenol blue) as an ion pair with cetyltrimethylammonium bromide (CTABr) in a silicone polymer matrix. Bromophenol blue, while contact the ammonia (both in water as well as in gaseous form) changes its color reversibly from yellow to blue. The immobilized dye shows long wave absorption with a good photostability. 

Ow et al. (2005) developed an improved method of incorporating fluorescent molecules into silica particles using a modified Stober synthesis, which resulted in both enhanced fluorescence and photostability of the encapsulated dyes. In this two-stage procedure, reactive organic dyes... 

An initial use of reflectance spectroscopy in the characterization of pharmaceutical solids concerned studies of the stability of coloring agents in tablet formulations. With the description of a device that enabled the surface of intact tablets to be studied [14], the photostability of various dyes and lakes in tablets was followed [15,16]. Exposure of formulations to both normal and exaggerated light conditions was investigated, and the kinetics of the photodegradation evaluated. In most cases, the photoreactions appeared to follow first-order kinetics. 

In general, the kinetics associated with the fading of the various dyes studied was found to vary over wide ranges. Lakes prepared from several dyes were found to exhibit less photostability than did the corresponding dyes [16]. In most instances, the initial rates of decomposition were significantly faster than the rates observed at later time points. 

Albert H. Coons was the first to attach a fluorescent dye (fluorescein isocyanate) to an antibody and to use this antibody to localize its respective antigen in a tissue section. Fluorescein, one of the most popular fluorochromes ever designed, has enjoyed extensive application in immunofluorescence labeling. For many years, classical fluorescent probes such as FITC or Texas red (TR) have been successfully utilized in fluorescence microscopy. In recent decades, brighter and more stable fluorochromes have continually been developed (see Table 14.1). Marketed by a number of distributors, cyanine dyes, Cy2, Cy3, Cy5, Cy7, feature enhanced water solubility and photostability as well as a higher fluorescence emission intensity as compared to many of the traditional dyes, such as FITC or TR. 

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