Fe(III)-Tannic Acid Complex Derived Fe3C Decorated Carbon

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Characterization, Synthesis, and Modifications

Fe(III)- tannic acid complex derived Fe3C decorated carbon nanofibers for triple-enzyme mimetic activity and their biosensing application Sihui Chen, Yixian Wang, Mengxiao Zhong, Dahai Yu, Ce Wang, and Xiaofeng Lu ACS Biomater. Sci. Eng., Just Accepted Manuscript • DOI: 10.1021/acsbiomaterials.8b01552 • Publication Date (Web): 31 Jan 2019 Downloaded from http://pubs.acs.org on February 3, 2019

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ACS Biomaterials Science & Engineering

Fe(III)- tannic acid complex derived Fe3C decorated carbon nanofibers for triple-enzyme mimetic activity and their biosensing application Sihui Chen†, Yixian Wang†, Mengxiao Zhong†, Dahai Yu*,‡, Ce Wang†, Xiaofeng Lu*,†

†Alan

G. MacDiarmid Institute, College of Chemistry, Jilin University, 2699 Qianjin Street, Chaoyang District, Changchun, 130012, P. R. China.

‡Key

Laboratory for Molecular Enzymology and Engineering of Ministry of Education, College

of Life Science, Jilin University, 2699 Qianjin Street, Chaoyang District, Changchun, 130012, P. R. China. *Corresponding author: Tel: +86-431-85168292; Fax: +86-431-85168292; Email: [email protected]; [email protected]

KEYWORDS: Fe(III)-tannic acid (TA) complex, Fe3C/C nanofibers, triple-enzyme mimetic property, colorimetric biosensing

ABSTRACT In the last one decade, nanomaterials-based artificial enzymes have been emerged as a hot spot in the field of catalysis. However, it is a significant challenge to fabricate functional nanomaterials for multiple-enzyme mimetic activity. In this work, we have presented an efficient catalytic 1 ACS Paragon Plus Environment

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platform to mimic peroxidase, oxidase and catalase-like activity by Fe3C decorated carbon nanofibers (Fe3C/C NFs). First, polyacrylonitrile nanofibers (PAN NFs) are prepared via an electrospinning technique. Next, Fe(III)-tannic acid (TA) complex is formed on the surface of PAN NFs through a wet chemical reaction. Finally, Fe3C/C NFs are obtained from the carbonization of the PAN/Fe(III)-TA complex nanofibers. The prepared Fe3C/C NFs show an excellent triple-enzyme mimetic property including peroxidase-like, oxidase-like and catalaselike activity, which is investigated thoroughly by the colorimetric experiment of the 3,3’,5,5’tetramethyl benzidine oxidation and the degradation of H2O2. Thanks to the superior catalytic performance of Fe3C/C NFs for oxidase mimicking, a facile and colorimetric way to determine glutathione with a high sensitivity and favorable selectivity has been achieved. This work provides an efficient platform for multiple enzyme mimicking, which may expand their promising applications in biosensing, biomedicine, and environmental technology.

INTRODUCTION Over the last few decades, much attention has been devoted to the research of artificial enzymes. The ultimate goal is to emulate the brilliant catalytic efficiency and outstanding selectivity of natural enzymes, as well as realize a much higher stability than natural enzymes.1,2 Since ferromagnetic nanoparticles were demonstrated to hold peroxidase-like activity, which was comparable to horse radish peroxidase (HRP), a large quantity and varied types of nanomaterials have been revealed to exhibit favorable enzyme-like catalytic efficiency and excellent stability.3 A term of “nanozyme” has been put forward for a comprehensive generalization of the nanomaterials-based enzymes.1,2,4 The nanozymes which can catalyze the generation of reactive oxygen species (ROS) are divided into the following main categories: peroxidase-like, oxidase-like, catalase-like 2 ACS Paragon Plus Environment

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and superoxide oxidase (SOD)-like mimics. However, up to now, most of the reported nanozymes are peroxidase mimics rather than the other enzyme-like activities. For instance, a large number of metals,5,6 metal oxides,7-9 chalcogenides,10,11 metal-organic frameworks

(MOFs)12

and

carbon-based

nanomaterials13-15

have

been

widely

demonstrated to hold peroxidase-like property. While some achievements have also been achieved for oxidase and catalase mimicking, generally, most of nanozymes only show one characteristic enzyme mimetic property. It is a great challenge to construct efficient nanozymes with multiple enzymatic mimetic properties, which show potential applications for sensing applications. Iron-based nanomaterials including iron oxides, iron hydroxides and multiferroic compounds showed rosy applications in catalysis, energy storage and conversation, and environmental technology.16-19 Among various types of iron-based nanomaterials, Fe3C plays a significant role in many electrochemically catalytic processes, such as oxygen reduction reaction, dye-sensitized solar cells and lithium ion batteries, etc.20-22 Recently, Fe3C-based nanomaterials have been demonstrated to hold oxidase-like property. For example, Zhang and co-workers prepared nitrogen-doped Fe3C@C composites through pyrolyzing Prussian blue (PB) cubes, exhibiting an excellent oxidase-like property.23 The carbon materials deliver a good electrical conductivity and stabilization to the Fe3C nanoparticles. Although some achievements have been realized for the Fe3C-based enzyme mimics, it is a big challenge to fabricate Fe3C-based nanomaterials for multiple enzyme mimicking. In this work, we have prepared Fe(III)-tannic acid (TA) complex derived Fe3C/C nanofibers (Fe3C/C NFs), which exhibit prominent triple-enzyme mimetic properties. It is well known that Fe(III) can chelate with TA to form Fe(III)-TA complex

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decorated on some typical supports.24,25 Herein, Fe(III)-TA complex was fabricated on electrospun polyacrylonitrile nanofibers (PAN NFs). Then the derived Fe3C/C NFs can be obtained through a carbonization process at 900 °C in Ar atmosphere. The morphology of long nanofibers provides a relatively large aspect ratio and the unique structure with Fe3C nanoparticles outside of the carbon nanofibers (CNFs) ensures the rapid electron transfer and fast contact of the reactants with the active sites. The as-obtained Fe3C/C NFs show satisfactory peroxidase- and oxidase-like activities, which are able to catalyze 3,3’,5,5’tetramethyl benzidine (TMB) oxidation both in the presence or absence of H2O2. Additionally, the Fe3C/C NFs are also proved to be efficient catalase mimics, which can catalyze the H2O2 decomposition into oxygen and water. Furthermore, based on the oxidase-like property of Fe3C/C NFs, a facile and colorimetric way to determine glutathione (GSH) with a low detection limit of 0.02 µM and favorable selectivity has been achieved.

EXPERIMENTAL SECTION Chemicals PAN (Mw=80,000 g·mol-1) was obtained from Jilin Chemical Plant. Fe(NO3)3·9H2O was available from Tianjin Yongsheng Fine Chemical Co., Ltd. TA was obtained from Tianjin Guangfu Fine Chemical Research Institute. N,N’-dimethylformamide (DMF) was received from Tianjin Tiantai Fine Chemical Co., Ltd. TMB was bought from Sinopharm Chemical Reagent Co., Ltd. Dihydroethidium (DHE) was obtained from Sigma-Aldrich. Dimethylsulfoxide (DMSO) and p-phthalic acid (PTA) were purchased from Aladdin. Other reagents including ethanol and hydrogen peroxide (H2O2) were commercially available from Beijing Chemical


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Works. Preparation of PAN/Fe(III)-TA complex nanofibers PAN NFs were fabricated through a versatile and simple electrospinning method. In general, a certain amount of PAN was dissolved in DMF to obtain electrospinning precursor and the concentration of PAN was fixed at 8 wt%. Then, the precursor solution was injected into the jet and the electrospinning was performed under a voltage of 18 kV. The distance from the jet to the collector was around 15 cm, and the ambient temperature and air humidity were 25-30 °C and 30-40 %, respectively. Next, 50 mg of PAN NFs were put into 20 mL of deionized water by a homogenizer, then 100 mg of Fe(NO3)3·9H2O were added in the suspension, and the suspension was stirred for 1 h. After that, 100 mg of TA was added into the above suspension, immediately the color of suspension changed into dark blue. After further stirring for 12 h, the as-obtained PAN/Fe(III)TA complex NFs were centrifuged and washed thoroughly with deionized water for several times. Finally, the product was dried through freeze-drying process. Preparation of Fe3C/C NFs Fe3C/C NFs was obtained via the calcination of PAN/Fe(III)-TA complex NFs. In a typical procedure, the PAN/Fe(III)-TA NFs were placed in a tube furnace and heated to 900 °C for 2 h with a heating rate of 2 °C/min in Ar atmosphere. Eventually, a black powder of the Fe3C/C NFs was obtained. Triple-enzyme mimetic activity of Fe3C/C NFs The catalytic activities of Fe3C/C NFs for peroxidase and oxidase mimicking were measured through a colorimetric route. To investigate the catalytic activity for oxidase mimicking, 20 μL of TMB (15 mM in DMSO) and 20 μL of Fe3C/C NFs suspension (3 5 ACS Paragon Plus Environment


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mg mL-1) were put into acetate buffer (3 mL, pH=4.0). Then, the absorbance was recorded by UV-Vis spectra after 10 min. The exploration of the catalytic property for peroxidase mimicking is similar to the above experiment except with the addtion of H2O2. In detail, 20 μL of TMB (15 mM in DMSO), 20 μL of H2O2 (30 %) and 20 μL of Fe3C/C NFs suspension (3 mg mL-1) were put into acetate buffer (3 mL, pH=4.0). The absorbance change of the reaction medium was recorded by UV-Vis spectra after 10 min. For testing the catalase-like catalytic activity, 50 μL of H2O2 (30%) was injected into different concentrations of aqueous Fe3C/C NFs suspension (0, 5, 10, 20, 30 μg mL-1), the total volume was 10 mL, the concentration of O2 generated was measured by a dissolved oxygen meter. Steady-state kinetic experiment The kinetic experiment was carried out for the peroxidase-like catalytic efficiency of Fe3C/C NFs. Two substrates of TMB and H2O2 were put into acetate buffer solution (3 mL, pH=4.0), and the concentration of one remained unchanged while the other varied. Then 20 μL of Fe3C/C NFs suspension (3 mg mL-1) was added, meanwhile, the changes of absorbance values at 651 nm were recorded in time course, the Michaelis-Menten constant could be calculated according to the following equation: 1/v=(Km/Vmax)·(1/[S])+1/Vmax

(1)

where v represents the initial velocity, Km stands for the Michaelis-Menten constant, Vmax refers to the maximal reaction velocity, and [S] is the concentration of the substrate.26 Detection of GSH


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GSH was detected based on the oxidase-like catalytic property of Fe3C/C NFs. In general, GSH with different concentrations in acetate buffer solution (pH=4.0) was prepared, then 20 μL of TMB (15 mM in DMSO) and 20 μL of Fe3C/C NFs suspension (3 mg mL-1) were added. After 10 min, the absorbance of the reaction system was monitored by a UV-Vis absorption spectrum. To investigate the selectivity of the detection system, different species of amino acids and oxidized glutathione (GSSG) as well as glucose were chosen for comparison. In a typical procedure, 20 μL of TMB (15 mM in DMSO) and 20 μL of inhibitor solution (30 mM) were added into acetate buffer solution (3 mL, pH=4.0), then 20 μL of Fe3C/C NFs suspension (3 mg mL-1) was injected to the reaction system, and the absorbance of the solution was monitored after 10 min by UV-Vis spectra. Characterization The morphologies of as-obtained PAN nanofibers, PAN/Fe(III)-TA NFs and Fe3C/C NFs were observed by field-emission scanning microscopy (SEM, FEI Nova NanoSEM) and transmission electron microscopy (TEM, JEOL JEM-1200 EX). More fine morphology features and energy dispersive X-ray (EDX) analysis were characterized by a FEI Tecnai G2 F20 and JEM-2100F high resolution TEM (HRTEM). The crystallographic features were obtained by X-ray diffraction (XRD, PAN-alytical B. V. Empyrean) with Cu Kα radiation and Raman spectra (Lab RAM HR Evolution). X-ray diffraction measurements were carried out from 10º to 70º, the step size was set as 0.026º/step. X-ray photoelectron spectroscopy (XPS, Thermo Scientific ESCALAB250) with an excitation source of Al Kα radiation was used to analyze surface composition of the as-obtained Fe3C/C NFs. In addition, the peroxidase-like and oxidase-like catalytic



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properties were investigated by ultraviolet-visible (UV-Vis, Shimadzu UV-2501 PC spectrometer) measurement, the catalase-like catalytic activity was recorded by a dissolved oxygen meter (REXDCH, JPBJ-608). The detection of radicals was studied on F97Pro fluorospectro photometer (Lengguang, Shanghai).

RESULTS AND DISCUSSION Morphology and chemical structure of Fe3C/C NFs In recent years, electrospinning technique has been widely used to construct a large variety of one-dimensional (1D) nanostructures for broad promising applications,27,28 In this study, we have prepared Fe3C/C NFs through a three-step approach (Figure 1). First, PAN NFs were fabricated through an electrospinning approach. Then, Fe(III)-tannic acid (TA) complex was formed on the surface of PAN NFs via a wet chemical reaction. At last, the PAN/Fe(III)-TA complex NFs were converted to Fe3C/C NFs through a carbonization process. As shown in Figure 2a, electrospun PAN NFs possess uniform 1D morphology with a large length-diameter ratio. The diameter of the PAN NFs is ranging from 310 to 380 nm. After the formation of Fe(III)-TA complex on PAN fibers, the color of the samples changed from white to dark blue, with a slight increment of the fibers diameter (Figure 2b). Furthermore, after calcination, the morphology of the prepared Fe3C/C NFs remained almost unchanged, while the color of the sample became black therewith. The diameter of the resultant Fe3C/C NFs ranges from 200 to 300 nm (Figure 2c and d).


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Figure 1. Schematic presentation of the synthesis procedure of Fe3C/C NFs.

More fine morphological features are further characterized by a HRTEM measurement. As shown in Figure 3a, the Fe3C nanoparticles with a diameter ranging from several to tens of nanometers distributed on the surface of carbon NFs are legible, the lattice spacing of 0.21 nm exhibited in Figure 3b is related to (211) plane of cohenite of Fe3C.29 Furthermore, the EDX spectrum represents the presence of C, N, O, Si, Cu and Fe species, demonstrating the formation of Fe3C nanoparticles on CNFs (Figure 3c). The existence of Si and Cu might be relevant to the copper grid and the instrument, respectively. The element mapping shows the distribution of C, N and Fe elements more intuitively, manifesting that Fe3C nanoparticles mainly distributed on the surface of CNFs (Figure 3d).



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Figure 2. SEM image of a) PAN nanofibers; b) PAN/Fe(III)-TA complex nanofibers; c) Fe3C/C NFs and d) TEM image of Fe3C/C NFs. The insets are photographs corresponding to the samples.

Figure 2. a) TEM image, b) HRTEM image and c) EDX spectrum of Fe3C/C NFs; d-1) dark field STEM image and EDX element mapping of d-2) Fe-K, d-3) C-K, d-4) N-K in Fe3C/C NFs. 10 ACS Paragon Plus Environment

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XRD measurements and Raman spectroscopy are utilized to characterize the crystalline features and chemical structure of the PAN/Fe(III)-TA NFs and the prepared Fe3C/C NFs. As seen in XRD patterns (Figure 4a), the peak situated at 16.9° and a broad noncrystalline peak between 20° and 30° are corresponding to PAN phase.30 While in the XRD pattern of Fe3C/C NFs, the peaks which are mainly centered at around 45° can be perfectly attributed to cohenite structure of Fe3C (JCPDS No.35-0772).31 Besides, the peak situated at around 25° is resulting from CNFs. This result demonstrates the successful fabrication of Fe3C/C NFs. Raman spectrum provides a more detailed characterization of the chemical structure of Fe3C/C NFs (Figure 4b). In the PAN/Fe(III)-TA NFs, the complex formed by the interaction between Fe(III) and TA is coated on the surface of PAN NFs, accordingly, the characteristic peak of Fe(III)-TA complex centered at 1588 cm-1 is observed,32 while other peaks are resulting from pristine electrospun PAN NFs. Compared with the PAN/Fe(III)-TA NFs, the carbonized Fe3C/C NFs exhibit two characteristic peaks at around 1329.5 and 1585.3 cm-1, which are owing to the D-band and Gband of CNFs.33 This result demonstrates that PAN has been completely converted to CNFs in the hybrid NFs.

Figure 3. a) XRD patterns of PAN/Fe(III)-TA NFs and Fe3C/C NFs; b) Raman spectra of PAN/Fe(III)-TA NFs and Fe3C/C NFs. 11 ACS Paragon Plus Environment


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To further explore the surface composition of the fabricated Fe3C/C NFs, XPS measurement was carried out. It is clearly seen the characteristic peaks of C, N, O, Fe elements in the widescan XPS spectrum (Figure 5a). In Fe 2p region, the characteristic peaks ascribed to Fe 2p3/2 and Fe 2p1/2 were observed at 710.8 eV and 726.0 eV, respectively (Figure 5b).34 In addition, a faint satellite peak at 719.0 eV also proves the possible co-existence of Fe(II) and Fe(III).16 The C 1s spectrum has been divided into three typical peaks, the major one centered at 284.7 eV is consistent with C-C,35 the other two bands at 281.6 eV and 288.9 eV can be assigned to C-Fe and C=O species (Figure 5c).36,37 The N 1s spectrum has also been fitted into two major bands, which are located at 400.8 eV and 398.4 eV. The fitted bands can be indexed to graphitic N and pyridinic N, respectively (Figure 5d).38-40 The presence of N might be caused by the doping state in the CNFs during the carbonization of PAN NFs. Additionally, the O 1s spectrum is fitted into two peaks, which can be assigned to C=O and C-O species, suggesting a certain oxidation state of the CNFs (Figure 5e).35


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Figure 4. XPS spectra of the fabricated Fe3C/C NFs, a) wide-scan spectrum; b) Fe 2p; c) C 1s; d) N 1s and e) O 1s region.

Triple-enzyme mimetic activity of Fe3C/C NFs Iron-based nanomaterials with diverse structures play an important role in the field of artificial enzyme catalysis. In this work, the prepared Fe3C/C NFs exhibit surprising triple-enzyme mimetic activity at the same time. As represented in Figure 6a, an obvious absorbance peak at 651 nm appears when both TMB and Fe3C/C NFs exist in an acetate 13 ACS Paragon Plus Environment


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buffer solution and its color changes from colorless to blue after ten minutes, which can be explained that the oxidation state of TMB (TMB+) is generated due to excellent oxidase-like activity of Fe3C/C NFs. By contrast, the individual TMB solution or Fe3C/C NFs suspension alone does not show obvious peak at 651 nm. Furthermore, after the addition of H2O2 in the reaction medium containing TMB and Fe3C/C NFs, the color turns from colorless into blue-green and the intensity of the absorbance peak at 651 nm is enhanced significantly (Figure 6b). Similarly, the control experiments exhibit that no obvious absorbance peak arises in the systems of TMB+H2O2 and Fe3C/C NFs+H2O2, implying that Fe3C/C NFs also show an outstanding peroxidase-like activity. The effect of pH values on the oxidase- and peroxidase-like activities has also been studied (Figure 6c). It is found that both the oxidase- and peroxidase-like activities are achieved at a pH value of 4.0, which is in accordance with the previously reported oxidase and peroxidase mimics. To better understand the mechanism underlying the peroxidase and oxidase-like properties of Fe3C/C NFs, fluorescence experiments are carried out to detect radicals produced during the enzyme-like reaction. PTA is used as a fluorescence probe for detecting hydroxyl radical (·OH) due to its property of capturing ·OH. As shown in Figure S1a, after PTA was added into the reaction system containing H2O2 and Fe3C/C NFs for ten minutes, characteristic fluorescence peak at around 435 nm can be observed, indicating the generation of 2-hydroxy terephthalic acid (TAOH). This result further confirms that ·OH is generated in the peroxidase-like reaction.41 In terms of oxidase-like property of Fe3C/C NFs, a specific fluorescence probe DHE is introduced into the reaction system for the capture of superoxide radical (O2·-). Then a distinct fluorescent


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emission can be observed at around 615 nm, which can prove that O2·- exist in the oxidase-like reaction system (Figure S1b).42 What can be concluded from the above is that Fe3C/C NFs can disintegrate H2O2 and the physically or chemically absorbed O2 into different ROS species, then Fe3C/C NFs exhibit remarkable peroxidase-like and oxidaselike catalytic activities in this way. Furthermore, Fe3C/C NFs also show distinct catalase-like catalytic property, which is able to catalyze H2O2 into oxygen and water. It can be investigated by measuring the concentration of generated dissolved O2. When the concentration of H2O2 is controlled unchanged and the ambient temperature is similar, the concentration of dissolved oxygen increases with the concentration of Fe3C/C NFs, confirming that Fe3C/C NFs process superior catalase-like properties (Figure 6d). Extremely small amounts of Fe3C/C NFs are used to generate sufficient oxygen, indicating that Fe3C/C NFs hold superior catalase-like performance compared to other nanocatalysts that have been reported previously.43-45



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Figure 6. a, b) UV-Vis absorption spectra and optical photographs of varied reaction systems with 10 min reaction time; c) the line chart corresponding to relationship between pH values and the relative peroxidase- and oxidase-like activity; d) effect of the Fe3C/C NFs concentration on O2 generated during H2O2 decomposition (concentration of Fe3C/C NFs: 0, 5, 10, 20, 30 μg mL1).

Steady-state kinetic analysis Kinetic analysis was also carried out for a better understanding of the catalytic nature of the as-obtained Fe3C/C NFs for peroxidase mimicking.26 Typical Michaelis-Menten curves are plotted by changing the concentration of one substrate while the other one remains unchanged (Figure S2a and c). The initial velocity of the reaction increases as the concentration of TMB or H2O2 increases. Furthermore, a linear curve between the reciprocal value of initial velocity and the reciprocal value of concentration of substrate is 16 ACS Paragon Plus Environment

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obtained, which can supply the typical kinetic parameters including Michaelis constant (Km) and the maximal reaction velocity (Vmax) (Figure S2b and d). Km value is often regarded to reflect the affinity between the substrate and catalyst.46 It is found that the Km values of the Fe3C/C NFs for peroxidase mimicking with H2O2 (5.65 mM) and TMB (1.78 mM) as substrates are both a little higher than those for HRP (3.7 mM and 0.43 mM),3 indicating that a larger TMB or H2O2 concentration is necessary to realize the maximal peroxidase-like efficiency. While the Vmax values are calculated as 21.28×10-8 M s-1 and 203.25×10-8 M s-1 by using H2O2 and TMB as substrates, significantly superior to those of HRP (8.71×10-8 M s-1 and 10.0×10-8 M s-1).3 The kinetic result demonstrates that the obtained Fe3C/C NFs are a kind of ideal peroxidase mimics.

Detection of glutathione GSH is a kind of important biomolecules to defense against many types of diseases, which is necessary to be sensitively determined through distinct detection methods.47-49 In consideration of excellent catalytic nature for oxidase mimicking, Fe3C/C NFs are appropriate as a sensing platform to determine GSH. GSH is able to inhibit TMB oxidation to some extent because of its resistance to oxidation. Figure 7a shows that the absorbance value at 651 nm decreases with the increasing GSH concentration. As the concentration increases to 200 μM, the absorption peaks almost disappear, proving that TMB is barely oxidized. Figure 7b displays the relationship between ΔA (A (651nm, absence) A

(651nm, GSH))

values and GSH concentrations, which provides a detection limit for GSH

as low as 0.02 µM (S/N=3) with a linear range of 0.5-10 μM. The detection limit based



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on this approach is superior to most of the previous reports of nanozymes-based sensing platforms.43,49-52

Figure 7. a) UV-vis absorption spectra of the oxidase-like catalytic reaction systems with varied GSH concentrations; b) the response curve to determine GSH and the inset displays the linear calibration curve from 0.5-10 μM.

Selectivity is an important indicator of the enzyme-like detection system. It is worth noting that Fe3C/C NFs exhibit a favourable selectivity for the detection of GSH (Figure S3). Herein, various types of biological molecules, such as common amino acids, glucose, and GSSG, are used as interferences. It is found that the ΔA value with the addition of Lcysteine is similar with that of GSH because cysteine is also an efficient inhibitor towards the TMB oxidation. However, GSH differs from most of the other amino acids, glucose and GSSG, demonstrating a favourable selectivity to determine GSH. Nevertheless, the intracellular cysteine content is usually much lower than GSH content, thus GSH can be distinguished from the similar substances appropriately and the sensitive detection of GSH can be applicable in complicated living organisms or environmental systems.


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CONCLUSIONS In summary, Fe3C/C NFs which are derived from PAN/Fe(III)-TA complex were fabricated through a simple carbonization approach. The as-obtained Fe3C/C NFs exhibited brilliant peroxidase-, oxidase- and catalase-like catalytic activities meanwhile. Based on their oxidase-like activity, selective detection of GSH could be demonstrated. In addition, the oxidation of TMB can be further promoted with the addition of H2O2 due to their peroxidase-like activity. Fe3C/C NFs can also catalyze the decomposition of H2O2 under neutral conditions, showing the perfect catalase-like activity. This study provides a novel thought to apply Fe3C-based nanomaterials which are derived from Fe(III)-TA complex for enzyme mimicking. The unique and remarkable triple-enzyme mimetic property offers Fe3C/C NFs promising prospects in biosensing, biomedicine and environmental technology.

ASSOCIATED CONTENT Supporting information Fluorescence spectra to detect ·OH and O2·-; Kinetic studies of the catalytic reaction of the asobtained Fe3C/C NFs for peroxidase mimicking; Selectivity analysis to detect GSH.

AUTHOR INFORMATION Corresponding Author *(D.H.Y.) Email: [email protected] *(X.F.L.) E-mail: [email protected]



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ORCID Dahai Yu: 0000-0002-0594-5236 Xiaofeng Lu: 0000-0001-8900-9594 Notes The authors declare no competing financial interest. ACKNOWLEDGEMENTS This work was financially supported by the National Natural Science Foundation of China (51773075, 51473065, 21474043).

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For Table of Contents Use Only Synopsis Fe(III)-tannic acid complex derived Fe3C decorated carbon nanofibers with triple-enzyme mimetic activity have been developed.


Fe(III)-Tannic Acid Complex Derived Fe3C Decorated Carbon

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