Synthesis of Fe^(3+)-doped Aminated Lignin as A Peroxidase Mimic for Colorimetric Detection of H_(2)O_(2) and Glucose

Peroxidase plays an important role in living systems;however,its storage difficulty and easy inactivation have limited its applications in complex environments.To address these problems,herein,we proposed a method to synthesize peroxidase mimics by amination,carbonization,and Fe^(3+)-doping of industrial alkali lignin.The Fe^(3+)-doped lignin-based peroxidase mimic(Fe-LPM),with active centers of coordination between Fe^(3+)and N atoms,showed higher tolerance to pH value and temperature than natural peroxidase.Using Fe-LPM,10-100 mmol/L of H_(2)O_(2) and glucose could be colorimetrically detected with the lowest detection limits of 80μmol/L and 1.5 mmol/L and visual detection limits of 1.0 mmol/L and 10 mmol/L,respectively.The Fe-LPM maintained peroxidase-like activity after 10 cycles and could even be used for H_(2)O_(2) detection in practical samples.This work not only provides a new approach to synthesize peroxidase mimics using biomass materials but also promotes the high-value utilization of lignin.

Detection mechanism and classification of design principles of peroxidase mimic based colorimetric sensors: A brief overview

Synthesis and characterization of enzyme mimics with characteristic stability and high catalytic efficiency is an interesting field for researchers.Especially,with the development of nanoscience and introducing of Fe3O4 magnetic nanoparticles as peroxidase mimics in 2007,various nanomaterials such as noble metals,metal oxides,and carbon materials were introduced as enzyme mimics(nanozymes).Various nanomaterials exhibit peroxidaselike activity,hence,most of the nanozymes are peroxidase mimetics.Although the nanozyme based sensors were previously classified,the classifications have been focused on the type of nanozyme action.Therefore,the nanozyme based sensors were classified as peroxidase,hydrolase,and urease mimic-based sensors.However,heretofore,these sensors are not classified based on the detection mechanism and principles of system design.The aim of this review is the focus on the peroxidase mimic based colorimetric sensors as the most common nanozyme-based sensors and their classification based on principles of sensor design and review of the detection mechanism of the current mimic peroxidase based sensors.Moreover,some current challenges and future developments in this field are discussed.

Gold nanoparticle-decorated MoSe_(2) nanosheets as highly effective peroxidase-like nanozymes for total antioxidant capacity assay

A visual colorimetric detection strategy is reported for total antioxidant capacity(TAC)assay by using 3,3',5,5'-tetramethylbenzidine(TMB)oxidation as chromogenic substrate based on gold nanoparticle-decorated MoSe_(2) nanosheets(Au@MoSe_(2)).Au@MoSe_(2) nanostructures exhibit high peroxidase-like activity and can catalyze H_(2)O_(2)to oxidize TMB.Based on inhibition effect of ascorbic acid(AA)on TMB oxidation,a facile and sensitive colorimetric method was developed for AA detection.Under optimal conditions,the proposed method showed a sensitivity for AA in a concentration range from 2 to 120μM and limit of detection was 0.41μM.Furthermore,the method was employed for TAC assay in actual samples,including commercial beverages and vitamin C tablets.This work represents a model in nanostructure design and will lead to further development of TAC assay in evaluation of antioxidant food quality.

Porous Ruthenium Selenide Nanoparticle as a Peroxidase Mimic for Glucose Bioassay

Nanozyme is a promising field that offers the substitution for natural enzymes using various nanomaterials.Various nanoma-terials with peroxidase-like activity were investigated.Among them,transition metal chalcogenides were explored as promis-ing nanozymes due to their excellent enzyme-mimicking activities.However,ruthenium selenide has not been studied as a peroxidase mimic because of the difficulty for synthesis.Herein,we prepared ruthenium selenide nanomaterial with ordered mesoporous structure(P-RuSe_(2))employing KIT-6 silica as the template.The composition and structure of P-RuSe_(2) were fully characterized.Further,its peroxidase-like activity was investigated.P-RuSe_(2) possessed excellent peroxidase-mimicking activ-ity,which catalyzed the oxidation of peroxidase substrates,including 3,3′,5,5′-tetramethylbenzidine,o-phenylenediamine,and 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid)in the presence of H_(2)O_(2).Moreover,P-RuSe_(2) exhibited higher peroxidase-like activity when compared with several representative nanozymes as well as bulk RuSe_(2).To demonstrate its potential applications,the colorimetric detection systems for H_(2)O_(2) and glucose were successfully constructed based on P-RuSe_(2) nanozyme.

A photonanozyme with light-empowered specific peroxidasemimicking activity

Although nanozymes have been widely developed,directly utilizing light to drive catalytic reactions like natural photoenzymes still remains challenging.Herein,we propose that photonanozymes(PNZs),as a novel kind of nanozyme,exclusively possess enzyme-mimicking activity under illumination.Only in the presence of visible light,the as-synthesized TiO_(2) proposed in this contribution shows excellent specificity of peroxidase-like without any oxidase-or catalase-like activity.The driving force of the light-empowered peroxidase-like photonanozymatic activity is explicated in terms of the photogenerated hot charge carriers in TiO_(2) PNZs and the accompanied reactive oxygen species.The co-substrates for photonanozymatic reaction over TiO_(2) PNZs facilitate the formation of the precarious and reactive peroxo-oxygen bridge between TiO_(2) and H_(2)O_(2),enabling the catalytic specificity.With the TiO_(2) PNZ-based biosensing platform for visual glucose detection exemplifying the concept of the application of PNZs,this work may evoke more inspirations to explore strategies for enlarging the scope of photoenzyme mimics.

Peroxidase-like properties of Ruthenium nanoframes

This work reports the inherent peroxidase-like properties of Ruthenium （Ru） nanoframes. After templating with Palladium （Pd） seeds, Ru nanoframes with an octa- hedral shape, average edge length of 6.2 nm, and thickness of 1.8 nm were synthesized in high purity （〉95 %） and good uniformity. Using the oxidation of 3,3t,5,5＇-tetram- ethylbenzidine （TMB） by H202 as a model catalytic reac- tion, the Ru frames were demonstrated to be approximately three times more active than natural peroxidases in cat- alyzing the formation of colored products. As compared to their natural counterparts, Ru frames have a stronger binding affinity to TMB as well as a weaker binding affinity to hydrogen peroxide during the catalysis. The Ru frames as peroxidase mimics proved to be chemically and thermally stable. This work represents the first demonstration of Ru nanostructure-based peroxidase mimics and is therefore expected to inspire future research on bio-applications of Ru nanomaterials.

Radical synthesis of tetrameric lignin model compound

The lack of suitable lignin model compound limits the understanding of the characteristics of lignin, and hence hinders the efficient utilization of this kind of bioresource. A tetramer phenolic lignin model compound composed of 5-5, α-O-4 and β-5 linkages was prepared by a two-step of free radical reaction with hydrogen peroxide/horseradish peroxidase and S2O8^2- /Fe^2＋ as the initiator. Compared with enzymatic process, this synthetic process gives a higher yield of 33.8% within a shorter time. HRMS and ^13C NMR spectroscopy show that synthesized model compound contains phenylpropane structure linked by 5-5, α-O-4 and β-5 bonds, which can mimic some chemical characteristics of lignin.