Facile enzymatic preparation of fluorescent conjugated polymers of phenols and their application in sensing

Abstract

The recognized drawback of utilizing metal catalysts for the synthesis of fluorescent conjugated polymers (CP) is the requirement for extensive purification to ensure complete removal of residual catalyst that would otherwise quench the fluorescence. In addition, typical synthesis of fluorescent CP involves multiple steps, monomers and solvents with varying levels of toxicity. This work demonstrates the possibility of utilizing oxidoreductase enzymes as the catalyst, for the one step polymerization of naturally occurring phenols to yield fluorescent conjugated polyphenols. The metal in the active site of the enzyme remains chelated during the synthesis allowing the polymers to be fluorescent as synthesized without the need for extensive purification. Three natural phenols, 4‐hydroxyphenylacetic acid, hydroxytyrosol, and chlorogenic acid were polymerized using Horseradish peroxidase as the biocatalyst. Spectroscopic techniques, UV–vis, Fourier transform infrared Spectroscopy–Attenuated Total Reflectance, and fluorescence, are used to characterize chemical structure and photoluminescence of these polymers. The polyphenols exhibit fluorescence with significant stokes shift in the range 30–100 nm rendering them useful in fluorescence quenching‐based sensors. Preliminary studies on use of these polymers, in the detection of nitro‐aromatic compounds in solution through using fluorescence‐quenching are also presented. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018, 135, 46496.

Biocatalytic Synthesis of Fluorescent Conjugated Polyserotonin

“…Polyserotonin exhibits low fluorescence quantum yield values, compared to the monomer and reference material, most likely because of the highly articulated structure that results in self-quenching. The relationship between the molecular weight and fluorescence quantum yield value had been reported for natural phenolic compounds (such as catechin and epicatechin) and synthetic polyphenols (such as poly(4-hydroxyphenylacetic acid)) [10,32,33]. Fig.…”

“…In this research, polyserotonin has KSV value about 2700 M -1 for both DNT and TNT. In comparison to other polyphenols synthesized in the same procedure, polyserotonin exhibited moderate sensitivity in nitroaromatic compounds detection [10]. The limited sensitivity of this polymer is due to extensive of the polymer in solvent [17].…”

“…The FTIR of polyserotonin as shown in Fig. 3 showed broad peak in the range 3650-2000 cm -1 predominantly from moisture absorption [10]. However, in this region, it is hard to conclude a N(1)-C(4) linkage purely from the missing N-H absorption.…”

“…Both catalysts have been used for the synthesis of a variety of conjugated polymers such as polyanilines, polypyrroles and polyphenols (conducting polymers and high thermal-resistant polymers) [7,8]. However, there has been very few reports of fluorescent conjugated polymers synthesized using enzyme catalysis [9,10,11]. Recently, we have demonstrated the possibility of synthesizing fluorescent oligomers of indole using soybean peroxidase as catalyst under mild conditions [4].…”

Detection of o‐nitro aniline by bovine serum albumin based self‐fluorescent hydrogel via FRET process

“…Introduction of natural polymer as a fluorophore for detection mechanism is an effective practice for economic advantage, easy handling and faster and smother sensing process. [38][39][40][41] Innovation and adaptation of natural polymeric backbone as signaling fluorophore 42 could be an effective and healthy practice owing to (i) assured biodegradation, (ii) non toxicity on prolong exposure and often excess or repeat uses will not be harmful, (iii) safe to handling during application and (iv) after operation, the removal and recovery will be simple and possible for insoluble fluorophore. 43 Herein, a new strategy has been broadened to formulate hydrogel template as functionalized and autofluorescent BSA (bovine serum albumins) hydrogel to become aware of the indication of NAs and trace amount o-NA in presence of various nitro-aromatics without adding any external fluorophore moiety.…”