Background:

Pyranine as a new class of fluorescent chemosensor for the Cu+ ion is reported.

Pyranine is capable of discriminating ranges of cations from the Cu+ ion, even in competing environment. Pyranine displays a rapid fluorescence response (t1/2=1.66 min) towards the Cu+ ion, and the micromolar detection limit enables the detection of the ion in environmental samples. The observed stoichiometry of complexation between Pyranine and Cu+ is 2:1[1]. The pH-sensitive fluorescent indicator Pyranine is studied to determine its usefulness as probes for the living cornea and anterior chamber. Pyranine has properties which render it almost ideally suited for this purpose. Adequate concentrations are reached in the cornea and anterior chamber after topical administration; measurements can be made by fluorophotometry for many hours. The pH is calculated by measuring the ratio of fluorescent intensity at two excitation wavelengths, I463/I404, a measurement which is dependent on pH but independent of the concentration of the fluorophore and other variables which can alter the intensity. In the rabbit eye, Pyranine in the cornea and anterior chamber is observed to undergo easily measurable changes in fluorescent ratios associated with lid closure and contact lens wear, indicating its sensitivity to mild changes in pH[2]. Pyranine (Py) is a fluorescence probe[3].

[1]. Saha T, et al. In vitro sensing of Cu(+) through a green fluorescence rise of pyranine. Photochem Photobiol Sci. 2014 Oct;13(10):1427-33. [2]. Thomas JV, et al. The fluorescent indicator pyranine is suitable for measuring stromal and cameral pH in vivo. Exp Eye Res. 1990 Mar;50(3):241-9. [3]. Evingür GA, et al. Kinetic models for the dynamical behavior of polyacrylamide (PAAm)-κ-carrageenan (κC) composite gels. J Biol Phys. 2015 Jan;41(1):37-47.