Wavelength–Ratiometric Probes for the Selective Detection of Fluoride Based on the 6-Aminoquinolinium Nucleus and Boronic Acid Moiety

Abstract

Herein we report a set of new water-soluble fluorescent probes (N -boronobenzyl-6-aminoquinolinium bromides, BAQBAs) sensitive to aqueous fluoride. These probes shows spectral shifts and intensity changes in the presence of fluoride, in a wavelength ratiometric and colorimetric manner, enabling the detection of fluoride concentrations at visible wavelengths, in the concentration range ≈1-300 mM. Although the sensing mechanism is different for fluoride as compared to the other halides, we have tested the utility of these probes towards the other halides, and the results reveal that the BAQBAs are in fact potential candidates towards the sensing of the all the halides, but in different concentration ranges. As the probes are based on the boronic acid moiety, which is a well-known fluoride and sugar chelator group, we have investigated the response of sugars (such as glucose and fructose, which are present in biological fluids and foodstuffs) as interferences in fluoride detection using these probes. Interestingly, the BAQBAs show a suppressed sugar response potentially allowing for the predominant fluoride sensitivity. In addition to physiological sugars, we also have assessed the response of aqueous halides as potential interferents, or indeed analytes to be sensed, and show that the new boronic acid containing probes respond well to aqueous fluoride in the presence of a high background of other species, such as in a biological cocktail of 50 mM Glucose, 50 mM aqueous Chloride and 5 mM Fructose.

Noninvasive Diagnostic Devices for Diabetes through Measuring Tear Glucose

“…They are being considered by at least three research groups who are working with such sensors as an alternative tool to continuously and noninvasively monitor the level of glucose in tears. [41][42][43] Luminescent/fluorescent contact lens-based sensors are a feasible technique because there are no electrodes or electric circuits. The fluorescence emission intensity (F) is described as…”

“…44 To our best knowledge, two different optical probes are used and incorporated into contact lenses, i.e., fluorescent labeled protein and glucose interactions, 41 and boronic acid and glucose. [42][43][44] The first one uses the competition reaction; the bonding between the glucose and enzyme is stronger than that between the fluorescent molecules and enzyme. The second one uses the direct reaction of analyte and fluorescent molecules.…”

Fluorescence Sensing of Monosaccharides by Bis-boronic Acids Derived from Quinolinium Dicarboxamides: Structural and Spectroscopic Studies

“…In this line, several quinolinium salts bearing monoboronic acid moieties have been studied by Geddes as optical sensors for glucose and fructose − as well as for CN – and F – ions. − In all cases, addition of fructose/glucose quenched the emission by a photoinduced electron transfer mechanism operating via the formation of the sp 3 -boronate anion with the normal selectivity of fructose > glucose and small binding constants of about 20 M –1 . Another strategy to enhance glucose affinity is through a two-point recognition using diboronic acids-based receptors capable of ditopic chelating binding of glucose but no other monosaccharides.…”

Regression Methods for Ophthalmic Glucose Sensing Using Metamaterials

“…Luminescent/fluorescent contact-lens-based sensors represent a feasible technique because they require no electrodes or electric circuits. Further efforts are needed to improve the resolution and sensitivity of the new device and to determine a physiologically relevant and baseline tear glucose concentration [8,9].…”