Dual-Readout Tyrosinase Activity Assay Facilitated by a Chromo-Fluorogenic Reaction between Catechols and Naphthoresorcin

Abstract

Analyte-responsive chromo-fluorogenic reactions under accessible conditions are important for designing small-molecule spectroscopic probes. We describe a series of newly constructed motifs based on the chromo-fluorogenic reaction between catechol derivatives (typically hydroxytyrosol, dopamine, and levodopa) and naphthoresorcin (NR) in aqueous solution under ambient conditions. The weakly absorptive and fluorogenic catechols/NR was converted to products having visible absorption and bright fluorescence within several minutes. The chromo-fluorophores produced from this reaction had a maximum absorbance at 458 nm and emission at 480 nm with high fluorescence quantum yields (30–84%). Inspired by the tyrosinase-catalyzed hydroxylation of monophenols to catechols, the tyrosinase-enabled chromo-fluorogenic reaction was verified by using monophenol (typically tyrosol) as the substrate. In this regard, a dual-readout tyrosinase activity assay was developed by virtue of the in situ “turn-on” optical signals. Furthermore, a test of tyrosinase inhibition, by using a common inhibitor kojic acid, demonstrated the potential of the chromo-fluorogenic reaction for developing other tyrosinase related assays and signal transduction.

A Rapid Fluorescence Sensor for the Direct Quantification of Rongalite in Foodstuffs

“…The ion peaks of rongalite couldn’t be found at 117 (m/z, [M-H] − ), because of the high-temperature vaporization of rongalite. As shown in Figure S1c , the intense ion peak at 258.1 (m/z, [M-H] − ) was attributed to azamondardine (reaction product of dopamine and resorcinol, without purification), which was consistent with the previous research [ 25 ]. The intensity of azamondardine sharply decreased from 8.9 × 10 7 to 4.0 × 10 3 , when rongalite was presented in the reaction system ( Figure S1d ).…”

“…According to the previous reports, under the alkaline condition, the dopamine could react with resorcinol within several minutes, producing in situ azamonardine fluorophores via a nucleophilic attack (shown in Scheme 1 ) [ 25 ]. In this research, we introduced a rongalite solution in the reaction system, and a surprising decreased optical density and fluorescence intensity were observed in Scheme 1 .…”

“…For example, Acuna et al described a strong yield fluorophore (azamonardine product) that was prepared by a simple reaction of resorcinol and catecholamines, and then the fluorophore could be used for analytical and imaging techniques [ 21 ]. Based on the above study, some researchers employed dopamine (or resorcinol) as the catalytic product of tyrosinase (or alkaline phosphatase), and then added the incorporating substrate to induce a fluorescence response [ 22 , 23 , 24 , 25 ].…”

Fluorescence/Colorimetry/Smartphone Triple-Mode Sensing of Dopamine by a COF-Based Peroxidase-Mimic Platform

“…Utilizing DA as substrates, the Michaelis–Menten constant ( K m ) and the maximum reaction rate ( V max ) of Cu-BTA-COF peroxidase mimics were determined to be 4.76 × 10 –5 M and 3.03 × 10 –9 M s –1 by the Lineweaver–Burk plot (Figure S9), comparable to the previously reported results. , The plausible mechanism of the Cu-BTA-COF system for multi-mode sensing of DA was deduced. With the addition of H 2 O 2 , under acidic environments, DA can be oxidized to dopaquinone, which may further react with NR by intermolecular Michael addition, undergo subsequent intramolecular cyclization, and finally obtain a fluorophore product (FP) as depicted in Figure S10. , FP exhibited an emission peak at around 485 nm and the residual NR displayed a fluorescent peak at 376 nm. Though norepinephrine, epinephrine, metanephrine, and normetanephrine had similar structures to DA, the selectivity of the Cu-BTA-COF platform to DA over the above catecholamines probably resulted from the higher activity of the Michael addition and intramolecular cyclization during the reaction processes.…”

Interfacially Super-Assembled Tyramine-Modified Mesoporous Silica-Alumina Oxide Heterochannels for Label-Free Tyrosinase Detection

“…Tyrosinase (TYR), as a multifunctional copper-containing enzyme, is widely distributed in plants, animals, and microorganisms. − Since TYR catalyzes the reaction of hydroxylation of monophenols to diphenols, TYR has been found as the key enzyme within the biosynthetic pathway of endogenous melanin. ,,− In addition, the TYR activity is not only thought to be associated with melanoma cancer and skin diseases but is also the factor that influences the nutritional value of food. , Thus, monitoring the activity of TYR precisely possesses great significance from clinical diagnosis to the food industry. , In the past few years, a variety of methods have been reported for the detection of TYR, such as colorimetric, spectrophotometric, and fluorescence-based methods. ,,,− However, these approaches generally require fluorogenic- or chromogenic-labeled substrates, which are expensive, complicated, and time-consuming . Therefore, it is desirable to develop a simple, label-free, and high-performance sensor platform for the detection of TYR.…”