Diagnostic Agents in Ophthalmology: Sodium Fluorescein and Other Dyes

Abstract

Sodium fluorescein (C2oHl00sNa2' resorcinolphthalein sodium, uranin, uranine yellow) is the dis odium salt of fluorescein, a weakly acidic dye of the xanthene series ( Fig. 1). It is an orange-red, odorless powder that is hygroscopic, freely soluble in water, and sparingly soluble in alcohol. Its molecular weight is 376 and its radius is 5.5 A. Fluorescein is synthesized by heating resorcinol with phthalic anhydride.Several properties of fluorescein contribute to its widespread use in ophthalmology. It is virtually nontoxic, shows only weak reversible tissue binding, and demonstrates the property of fluorescence. A fluorescent molecule absorbs light energy at a given wavelength. This results in excitation of electrons from the ground state to an excited state. Within a very short period oftime (about 10-9 s), the electrons return from the excitation state to the ground state and emit energy at a longer wavelength of light than that previously absorbed. The wavelengths at which fluorescein absorbs and emits light will vary, depending upon the pH of the solution, the thickness and concentration of the solution, the solvent, the presence of protein binding, the presence of hemoglobin, and other factors. Circulating fluorescein in the blood absorbs maximally at about 465-490 nm and has a peak emission at 520-530 nm. In the ocular fluids, the absorption peak is 480 nm and the emission peak is 520 nm. Fluorescein is a very efficient fluorescent molecule with a high quantum yield. Because of this, it can be detected at very low concentrations.Several additional properties of fluorescein mut be understood in order to appreciate its clinical uses. In general, the more intense the exciting light source, the greater will be the amount of fluorescence. Up to a point, increasing the concentration of fluorescein will result in increased fluorescence. At high concentrations, however, dimerization and polymerization occur and result in decreased fluorescence, with a shift in the emission spectrum to longer wavelengths. Quenching, a nonradiative dissipation ofthe absorbed energy, also occurs in concentrated solutions. Self-absorption of emitted light reduces fluorescence and the emission spectrum shifts toward longer wavelengths. For these reasons, highly concentrated so-

Healing of Microdefects in SSZ-13 Membranes via Filling with Dye Molecules and Its Effect on Dry and Wet CO2 Separations

“…The compound is an orange-red, odorless powder that is highly soluble in water (henceforth, the fluorescein sodium salt will be referred to as the dye). The conjugated system of xanthene in the chemical form of the dye allows for absorption of light and causes light emission at a specific wavelength . The molecular size of the dye is ∼1 nm, which is too large for the zeolite pores, but small enough to selectively block microdefects (< ∼2 nm).…”

“…The conjugated system of xanthene in the chemical form of the dye allows for absorption of light and causes light emission at a specific wavelength. 55 The molecular size of the dye is ∼1 nm, which is too large for the zeolite pores, but small enough to selectively block microdefects (< ∼2 nm).…”

Fluorophotometric determination of aqueous humor flow rates in red-tailed hawks (Buteo jamaicensis)

“…27 In addition, investigators in that aforementioned study 4 used an excitation filter set at 365 nm, despite the fact that the maximum excitation for sodium fluorescein is 480 nm. 38 Therefore, the fluorescein concentrations those other investigators 4 used for the AHFR calculations may have been erroneous. Interestingly, a technique of repetitive sampling of AH after administration of para-aminohippuric acid was used in another study 39 to calculate an AH turnover rate of 1.7% to 2%/min in clinically normal leghorn hens, which closely approximated the results of the study reported here.…”

Reversing protonation of weakly basic drugs greatly enhances intracellular diffusion and decreases lysosomal sequestration

“…The anti-cancer drug mitoxantrone (Shenkenberg and Von Hoff, 1986), and the glycogen synthase kinase GSK3 inhibitor SB216763 (Wagman et al, 2005). In addition, we monitored the diffusion of the diagnostic staining agent fluorescein disodium salt (Jampol and Cunha-Vaz, 1984), the fluorogenic substrate CCF2 (Zuverink and Barbieri, 2015) and boron dipyrromethene (BODIPY) analogues, which are used as fluorescent markers for lipids, membranes, and other lipophilic compounds (Poryvai et al, 2022).…”

“…We studied the following drugs with intrinsic fluorescence in the visible spectrum: the antimalarial drugs quinacrine dihydrochloride, 29 primaquine phosphate 30 and amidoquine; 31 the anti-cancer drug mitoxantrone; 32 the glycogen synthase kinase GSK3 inhibitor SB216763. 33 In addition, we monitored the diffusion of the diagnostic staining agent fluorescein disodium salt, 34 the fluorogenic substrate CCF2 35 and boron dipyrromethene (BODIPY) analogues, which are used as fluorescent markers for lipids, membranes, and other lipophilic compounds. 36 Measuring the diffusion coefficients of these compounds and their cellular distributions showed very slow diffusion of the basic compounds, low FRAP recovery and accumulation in lysosomes.…”