A novel fiber-optic pH sensor incorporating carboxy SNAFL-2 and fluorescent wavelength-ratiometric detection

Abstract

A fiber-optic pH sensor was prepared using the self-referencing fluorescent pH probe carboxy seminaphtho-fluorescein (SNAFL-2). The ratio of the emission from the base form of this dye and the emission near the isoemissive point is insensitive to variations in the excitation intensity and photobleaching. The carboxy SNAFL-2 and a photoaffinity crosslinker, 4-azido-2,3,5,6-tetrafluorobenzoic acid, succinimidyl ester, were attached onto poly(acrylamide-co-vinylamine) to form a hydrophilic functional membrane for the fiber-optic sensor. Photo crosslinking was used to create a crosslinked pH-sensing membrane and covalently bind the membrane onto the surface of the PMMA optical fiber. The fluorescent properties of the membrane-fiber conjugate have been determined. The membrane is stable, and the pH sensor shows a fast response time and excellent resolution in a wide pH range of 3 to 11.

Microfabricated protein-containing poly(ethylene glycol) hydrogel arrays for biosensing

“…This property allows the response of the fluorophore to be correlated to the ratio of the fluorescent intensities at the two peaks. Such a wavelength-ratiometric measurement allows the suppression of errors due to interferences such as instrumental artifacts, photobleaching and scatter [22]. Similar to earlier studies, we observed a red shift in the peaks upon conjugation to the enzymes by about 5 nm [1,2].…”

Biological Imaging and Spectroscopy of pH

“…Fluorescent pH probes incorporated in optical pH sensors, optrodes, have additional advantage beyond sensitivity because they measure the Stockes-shifted fluorescence emission and may use a single fiber for both dye excitation and collection of signal-carrying light [13,44,45]. Moreover, an application of optical sensors based on energy-transfer between a dye pair [46] allows the use of an absorbance-based pH indicator while retaining the advantage of fluorescence detection.…”

Highly Photostable Near-Infrared Fluorescent pH Indicators and Sensors Based on BF2-Chelated Tetraarylazadipyrromethene Dyes

“…13,14 The most frequently used fluorescent pH indicators are 8-hydroxypyrene-1,3,6-trisulfonic acid (HPTS), carboxyfluorescein derivatives, seminaphthorhodafluors (SNARFs), and hydroxycoumarins. 15−19 However, these indicators suffer from several drawbacks. For example, carboxyfluorescein has only moderate photostability, and the photostability of 2′,7′-dihexylfluorescein (suitable for measurements in seawater) is very poor; 20 the p K a value of HPTS is highly dependent on ionic strength of solution; and most coumarins are excitable only by high-energy radiation in the range from 350 to 450 nm.…”