Two-in-One Dual-Channel Boronic Ester Block Copolymer for the Colorimetric Detection of Cysteine and Glucose at Neutral pH

Abstract

Developing a chemosensor to recognize more than one biologically important molecule from a single polymeric entity is essential. In this study, a block copolymer probe [PPBA-b-PDMA (P1)] of (2-phenylboronic esters-1,3-dioxane-5-ethyl) methyl acrylate (PBA) and N,N′-dimethylacrylamide (DMA) was synthesized by reversible addition−fragmentation chain transfer polymerization using a cysteine-detectable aldehydefunctionalized azobenzene chain transfer agent. P1 was selfassembled in water to form micelles at neutral pH. The colorimetric detection was not observed upon adding cysteine to the micellar solution since water-soluble cysteine could not reach the aldehyde group of the azo receptor hidden in the micelles' center. However, with the introduction of glucose, micelles became swollen since the PPBA block changed its behavior to hydrophilic by transforming a boronic ester to boronic acid. Thus, the azo receptor became exposed to cysteine, leading to the colorimetric detection of cysteine. Glucose detection was also demonstrated by titrating P1 solution with glucose at a fixed amount of cysteine. Therefore, a unique platform with a dual-detection capacity of cysteine and glucose is proposed.

A water-soluble azobenzene-dicyano pendant polymeric chemosensor for the colorimetric detection of cyanide in 100% aqueous media and food samples

“…The detection limit was calculated by using the following equation:Detection limit = 3 σ / k where σ is the standard deviation of the blank measurement, and k denotes the slope of the curve at various concentrations of CN − . 41,42…”

“…where s is the standard deviation of the blank measurement, and k denotes the slope of the curve at various concentrations of CN À . 41,42 Paper-strip preparation P1 in THF (50 mM concentration of azo-dicyano units; assuming 6% incorporation of azobenzene units in the polymer chain) was prepared and a 2 Â 2 cm 2 piece of cellulose-based filter paper (Whatman s , Grade 1) was soaked and dried under room temperature. Cyanide solution in deionized water was sprayed onto each piece of paper under room temperature.…”

Thin Polymeric Films for Real-Time Colorimetric Detection of Hydrazine Vapor with Parts-per-Million Sensitivity

“…LOD was estimated using an UV–vis spectrometer. To obtain the LOD value, fixed concentrations of M1 and/or P1 solutions were titrated with different concentrations of hydrazine, and the detection limit was determined by the following equation: where k denotes the slope of the curve at various hydrazine concentrations and σ is the standard deviation of blank measurements. , …”