Conjugated hypercrosslinked polymers imprinted with 3,5-dinitrosalicylic acid for the fluorescent determination of α-amylase activity

• Published in: Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy Vol. 291; p. 122383
• Main Authors: Yan, Ru-Yu, Lin, Wen-Hsin, Lu, Te-Ling, Chen, Jian-Lian
• Format: Journal Article
• Language: English
• Published: England Elsevier B.V 15.04.2023
• Subjects: 3,5-Dinitrosalicylic acid; Adsorption; alpha-Amylases; Coloring Agents; Conjugated; Friedel–Crafts; Hypercrosslinked; Imprinted; Micropore; Molecular Imprinting - methods; Polymers - chemistry; Spectrometry, Fluorescence - methods; α-amylase; Hypercrosslinked; α-amylase; 3,5-Dinitrosalicylic acid; Micropore; Conjugated; Friedel–Crafts; Imprinted
• ISSN: 1386-1425; 1873-3557
• DOI: 10.1016/j.saa.2023.122383

Schematic of the preparation of π-conjugated molecularly imprinted hypercrosslinked polymers (MIHCPs) and the fluorescent determination of α-amylase activity by MIHCPs. [Display omitted] •Hypercrosslinked polymer (HCP) was molecularly imprinted for the first time.•The 3,5-dinitrosalicylic acid (DNS) imprinted HCP was a fluorescent probe for DNS.•α-amylase activity was fluorescently determined using the DNS-imprinted HCP.•Microbial, salivary, and pancreatic α-amylase activities were determined. The discovery of a series of coupling reactions between various building blocks has driven the development of porous organic polymers, but the common usage of expensive and air-sensitive organometallic catalysts and complex procedures in harsh syntheses has limited their expansion. A microporous hypercrosslinked polymer (HCP) was synthesized by polymerizing a naphthalene monomer and a 1,4-dimethoxybenzene crosslinker using Friedel–Crafts alkylation over an FeCl3 catalyst and imprinted with 3,5-dinitrosalicylic acid (DNS). The DNS-molecularly-imprinted HCPs (MIHCPs) were characterized as having IUPAC Type I mesoporosity, a specific surface area of 1134 m2 g−1, a monolayer adsorption capacity of 116 cm2 g−1, pore sizes ranging from 5 to 8.5 Å, amorphous frameworks, and distinctive absorption and emission bands by N2 adsorption/desorption analyses, scanning and transmission electron microscopies, and FTIR, UV–Vis, and fluorescence spectrometries. The π-conjugated imprinted framework endowed the MIHCPs with 405-nm fluorescent emission at a 330-nm excitation and dynamic quenching, which was confirmed by changes in fluorescence lifetime and followed a linear Stern-Volmer plot against 1.0–200 μM DNS template molecules under optimized conditions of a pH 7.0 buffer, an MIHCP concentration of 125 μg mL−1, and a 3.0-min equilibration time. The MIHCPs exhibited a high imprinted factor of 8.7 against nonimprinted HCP and a selectivity of 8.63 against reduced DNS, which enabled fluorometric detection of DNS molecules produced by the hydrolysis of starch with microbial, salivary, and pancreatic α-amylases and the subsequent redox incubation with the DNS oxidant. The fluorometric measurement of α-amylase activity was higher in accuracy and precision (RSD: 2.6–2.8% vs. 3.9–4.0%) than conventional UV–Vis spectrometry because the excellent fluorescent sensitivity and imprinting selectivity of the MIHCP probes enabled the use of higher dilution factors with weaker matrix effects.