The Interaction of Boronic Acid-Substituted Viologens with Pyranine:  The Effects of Quencher Charge on Fluorescence Quenching and Glucose Response

Abstract

The fluorescence sensing of several monosaccharides using boronic acid-substituted viologen quenchers in combination with the fluorescent dye pyranine (HPTS) is reported. In this two-component sensing system, fluorescence quenching by the viologen is modulated by monosaccharides to provide a fluorescence signal. A series of viologen quenchers with different charges were prepared and tested for their ability both to quench the fluorescence of HPTS and to sense changes in glucose concentration in aqueous solution at pH 7.4. Both quenching efficiency and sugar sensing were found to be strongly dependent upon viologen charge. The molar ratio between HPTS and each of the viologen quenchers was varied in order to obtain an optimal ratio that provided a fairly linear fluorescence signal across a physiological glucose concentration range. Both the quenching and sugar sensing results are explained by electrostatic interaction between dye and quencher.

Fluorescent Quantum Dots with Boronic Acid Substituted Viologens To Sense Glucose in Aqueous Solution

“…[13,14] When experimenting with several different quencher/QD ratios, we observed generally the same behavior as with traditional organic dyes, in which higher ratios tended to give larger, more-linear fluorescence signals in response to the introduction of glucose (Figure 3). …”

“…[13][14][15] Signal modulation occurs when glucose binds to the boronic acid receptor moiety, which at pH 7.4 exists in its trigonal neutral form in the absence of glucose. [16] Formation of the more-acidic glucose boronate ester shifts the acid-base equilibrium of the boronic acid towards its anionic tetrahedral "-ate" form.…”

“…Our previous studies showed that viologens were extremely efficient in statically quenching the fluorescence of many organic dyes through complex formation with the fluorophore. [13,14] We reasoned that the fluorescence of core-shell QDs that bear polar surface groups such as carboxy and amine groups might be similarly quenched through complex formation with our boronic acid substituted viologen quenchers.…”

Dual Roles of Polyhydroxy Matrices in the Homocoupling of Arylboronic Acids Catalyzed by Gold Nanoclusters under Acidic Conditions

“…[7,14] The significant pH-dependent equilibria between phenylboronic acid and a generic diol are shown in Scheme 2. [14][15][16] Both phenylboronic acid (A) itself and its conjugate base, the phenylboronate anion (B) , bind reversibly to the diol fragments with the liberation of two molecules of water. The binding affinity between carbohydrates and boronic acid depends mainly on the pK a value of boronic acid and the pH of the solution.…”

Fluorescence Response Mechanism of d-Glucose Selectivity for Supramolecular Probes Composed of Phenylboronic-acid-modified β-Cyclodextrin and Styrylpyridinium Dyes

“…1,2 Although several types of saccharide receptors having different recognition mechanisms are available, the most well-understood receptors are arylboronic acids. [3][4][5][6][7][8][9][10] The advantage of arylboronic acids as saccharide receptors originates in the favorable stability of cyclic boronate esters that are formed on reacting arylboronic acids with saccharides, even in water. In addition, it is easy to read out photophysical signals, such as UV-visible and fluorescence signals, associated with the formation of cyclic boronate esters.…”