A highly sensitive sensor based on a computer-designed magnetic molecularly imprinted membrane for the determination of acetaminophen

Journal Pre-proof A highly sensitive sensor based on a computer-designed magnetic molecularly imprinted membrane for the determination of acetaminophen Changlin Su, Zhiyang Li, Di Zhang, Zhimei Wang, Xin Zhou, Lifu Liao, Xilin Xiao PII:

S0956-5663(19)30898-X

DOI:

https://doi.org/10.1016/j.bios.2019.111819

Reference:

BIOS 111819

To appear in:

Biosensors and Bioelectronics

Received Date: 1 June 2019 Revised Date:

15 October 2019

Accepted Date: 23 October 2019

Please cite this article as: Su, C., Li, Z., Zhang, D., Wang, Z., Zhou, X., Liao, L., Xiao, X., A highly sensitive sensor based on a computer-designed magnetic molecularly imprinted membrane for the determination of acetaminophen, Biosensors and Bioelectronics (2019), doi: https://doi.org/10.1016/ j.bios.2019.111819. This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. © 2019 Published by Elsevier B.V.

Credit Author Statement

Outlining all authors' individual contributions: Changlin Su: Conceptualization, Roles/Writing - original draft, Writing - review & editing; Zhiyang Li, Conceptualization, Data curation, Validation, Software; Di Zhang, Conceptualization, Data curation, Formal analysis, Visualization; Xilin Xiao, Conceptualization, Funding acquisition, Resources, Supervision; Zhimei Wang, Investigation, Data curation, Formal analysis; Xin Zhou, Methodology, Project administration, Resources; Lifu Liao, Conceptualization, Project administration, Resources;

A highly sensitive sensor based on a computer-designed magnetic molecularly imprinted membrane for the determination of acetaminophen 1

*

Changlin Su , Zhiyang Li1, Di Zhang1, Zhimei Wang1, Xin Zhou1, Lifu Liao1, Xilin Xiao1,2,3 1

School of Chemistry and Chemical Engineering, Hunan Province Key Laboratory for the Design and

Application of Actinide Complexes, University of South China, Hengyang City, Hunan Province 421001, P.R. China 2

School of Resource & Environment and Safety Engineering, University of South China, Hengyang

City, Hunan Province 421001, P.R. China 3

State Key Laboratory of Chemo/Biosensing and Chemometrics, Hunan University, Changsha 410082,

P.R. China

Abstract: In this paper, a sensor based on a magnetic surface molecularly imprinted membrane (MMIP) was prepared for the highly sensitive and selective determination of acetaminophen (AP). Before the experiment, the appropriate functional monomers and solvents required for the polymer were screened, and the molecular electrostatic potentials (MEPs) were calculated by the DFT/B3LYP/6-31+G method. MMIP with high recognition of AP was synthesized based on Fe3O4@SiO2nanoparticles (NPs) with excellent core-shell structure. Next, a carbon paste electrode (CPE) was filled with a piece of neodymium-iron-boron magnet to make magnetic electrode (MCPE), and MMIP/MCPE sensor was obtained by attaching a printed polymer to the surface of the electrode under the strong magnetic. Due to the stable molecular structure of the electrode surface, the sensor is highly effective and accurate for detection of AP using DPV. The DPV response of the sensor exhibited a linear dependence on the concentration of AP from 6×10-8 to 5×10-5 mol L-1 and 5×10-5 to 2×10-4 mol L-1, with a detection limit based on the lower linear range of 1.73×10-8 mol L-1(S/N=3). When used for determination of AP in actual samples, the recovery of the sensor to the sample was 95.80 - 103.76%, and the RSD was 0.78% - 3.05%. Keywords: Magnetic molecularly imprinted membrane; Acetaminophen; Electrochemical sensor; Carbon paste electrode

1.

Introduction Acetaminophen (AP), chemically known as 4-acetamidophenol or N-(4-hydroxyphenyl)acetamide,

is used to treat fever, neuralgia, and migraine headaches, as well as for pain relief after surgery. AP is widely used in Chinese and Western medicines (Ennis et al. 2016). Because the effects of AP on the human body are mild, long-lasting and safe (Lancaster et al. 2015), it is especially suitable for patients who cannot tolerate drugs based on carboxylic acids (Heard et al. 2016). However, with excessive use of AP, patients may develop symptoms of nausea, anorexia, and even liver necrosis and kidney failure,

*

Corresponding author: Tel. / fax: +86 734 8282375.

E-mail address:xiaoxl2001@ 163.com

which can be life-threatening (Ohlsson and Shah 2018; Pang et al. 2016). Therefore, the detection of AP content is of great significance, both in clinical applications and in physiological functions. Currently, several analytical techniques have been used in extensive research on AP, including fluorescence spectroscopy (Montaseri and Forbes 2017), spectrophotometry (Youssef et al. 2018), thermogravimetric analysis (Khanmohammadi et al. 2012), and gas chromatography (Yao et al. 2007). However, these approaches are limited because of their complicated operation or high price. Consequently, electrochemical approaches, especially imprinting techniques based on electrochemical sensors, have received widespread attention due to their advantages of easy monitoring, low cost and high sensitivity (Labib et al. 2016; Maduraiveeran et al. 2018; Shumyantseva et al. 2017; Xiang et al. 2017; Yin et al. 2018; Zhang et al. 2017). Molecular imprinting technology refers to the preparation of polymers with selective recognition capability for a specific molecule. The specific steps of the molecular imprinting preparation method are as follows: linkage of the template molecule and functional monomer by a covalent bond or a non-covalent bond to form a complex; addition of a crosslinking agent and initiator to polymerize the monomer complexes under photothermal conditions; elution of the template molecules in the polymer, to leave binding sites with specific recognition for the template molecule, and recombination of these specific sites with the template molecule in standard solutions or the unknown (Kan et al. 2009; Wang et al. 2017; Zhang and Liu 2019). This technology has been skillfully applied in various fields in recent years due to its advantages of high selectivity, low cost, simple operation, and low detection limits (Ding and Heiden 2014; Saylan et al. 2017). Molecular imprints may be prepared by bulk imprinting and surface imprinting techniques. The application of surface molecular imprinting is to design the molecular recognition site on or near the surface of the carrier and has beneficial properties: improve recognition ability, reduce mass transfer resistance, convenient molecular eluting (Gast et al. 2019; Hai-Juan et al. 2006). Therefore, the surface molecularly imprinted technology is also skillfully applied in this work. Recently, magnetic molecularly imprinted polymers (MMIPs) are prepared by using magnetic nanoparticles as carriers in MIP, which have large specific surface area, superparamagnetic behavior and strong response to electrochemical signals (Babamiri et al. 2018; Tang et al. 2018). In addition, since MMIPs have strong magnetic properties, they can be separated from other sample components using an external magnetic field (Yang et al. 2017; Zhang et al. 2011). For the carriers, Fe3O4@SiO2 magnetic NPs are the most common substance in molecular imprinting technology due to their stable chemical properties, strong physical structure, high mechanical strength and the like. In addition, the silica surface can greatly expose the action sites and reduce the “embedding” phenomenon, thus improving the adsorption-desorption kinetic properties (Fan et al. 2012; Li et al. 2018; Yang et al. 2018). So Fe3O4@SiO2 magnetic NPs are used as carrier for research in this paper. Selection of functional monomers, solvents and other conditions for the preparation of the polymers can be challenging. There is lack of theoretical guidance, resulting in high cost, long preparation time, and poor experimental effects. Therefore, the development of computer technology and quantum chemistry theory is particularly important for applications of molecular imprinting systems (Li et al. 2018; Lu et al. 2018). In this paper, molecular simulation calculations were applied in this research based on the DFT/B3LYP/6-31+G method with Gaussian 09 software, resulting in

reduced cost, enhanced effectiveness, and improved experimental efficiency. In this work, an innovative and high performance electrochemical sensor was developed for the detection of AP. First, a suitable functional monomer and solvent for the template molecule were selected by molecular simulation calculations (Rostamizadeh et al. 2012; Yang et al. 2016).After forming a core-shell polymer on the Fe3O4@SiO2NPs carrier (Attallah et al. 2018), the MCPE was fabricated by embedding a magnet in a carbon paste electrode. Then, the MMIP was transferred to the MCPE by magnetic attraction, making the polymer on the electrode surface stronger and more stable for a series of subsequent tests.

2. Experimental 2.1. Reagents and instruments Electrochemical workstation (ChenHua Co. Ltd. China), SEM(Quanta FEG 250), TEM(Tecnai G2 F20) Vendors

for

acetaminophen

(AP),4-vinylpyridine

(4-VP),

methacrylic

acid

(MAA),

3-aminophenylboronic acid (3-APBA), ethylene glycol dimethacrylate (EGDMA), dopamine (DA), divinylbenzene (DVB), FeCl3•6H2O, acrylamide (AM), methacryl (MAA), methanol (MT), trimethylolpropanetrimethacrylate (TRIM), ethanol (EA), acetonitrile (ACN), dimethyl sulfoxide (DMSO) ), chloroform (TCM), tetrahydrofuran (THF), toluene (TL), ethylene glycol, NaAc, tetraethyl orthosilicate (TEOS) were purchased from Aladdin Reagents Co.Ltd.

2.2. Magnetic molecular imprinting films designed by molecular simulation

The choice of functional monomers is a key to the success of synthesizing MIPs with excellent properties. The conformational optimizations for the complexes and molecules were obtained (Huynh et al. 2015; Rostamizadeh et al. 2012), and the binding energy (∆E) (Fizir et al. 2018) of the complexes was calculated according to: ∆E = EC - ET - ∑EM

(1)

Where ∆E is the binding energy difference, EC is the energy of the complex of AP and functional monomer, ET is the energy of AP, and ∑EM is the sum of the energies of the functional monomer. The energy of the compound was calculated by the polarizing continuous model (PCM) (Attallah et al. 2018; Salajegheh et al. 2019), and the interaction between solvent and imprinted component was determined based on the energy |∆E*|(Dong et al. 2007), calculated as: |∆E*| = Es - Ev

(2)

In equation 2, Es is the interaction energy between the functional monomer and imprinted molecule in the solvent environment, and Ev is the interaction energy between the functional monomer and imprinted molecule in vacuum. In addition, MEP analysis of the selected functional monomers and template molecule were carried out to further verify whether the synthesized polymers would yield the most suitable MMIP.

2.3. Fabrication of MMIP/MCPE

First, Fe3O4 (Hu et al. 2010) and Fe3O4@SiO2 (Zhang et al. 2011) were prepared according to the references. Next, the product of the prepared MMIP was separated and purified by a magnet (Fig.S1). As

a

reference,

the

non-molecular

magnetic

imprinted

polymer

(MNIP)

and

Fe3O4@SiO2-free-MIP/MCPE were prepared using the same procedure. Finally, the MCPE was prepared according to the literature (Peng et al. 2011). Detailed preparation steps are provided in the supporting materials. One mg of the above prepared polymer was ultrasonically dispersed in 1 mL of tetrahydrofuran. The MMIP/MCPE sensor (Fig.S2) was obtained by uniformly dropping 25 µL of the suspension onto the surface of the MCPE, and the sensor was stored in a refrigerator at 4°C until use (Li et al. 2018; Wang et al. 2019). The specific steps are shown in Scheme 1.

2.4. Electrochemical detection

A CHI660C electrochemical workstation was used as the detection platform. With MCPE as the working electrode, calomel electrode as the reference electrode, and a platinum electrode as the counter electrode, electrochemical experiments were carried out according to the optimized conditions. Before each experiment, the working electrode was immersed in 5.0 mL of AP standard solution for 25 min; then it was washed with distilled water to remove surface impurities and immersed in 5.0 mL of 0.2 mmol L-1 PBS buffer. The DPV experiment was performed in a potential range from 0V to 0.8V with a pulse width of 170ms, a potential increment of 20 mV, pulse amplitude of 50 mV, and a scan rate 25 mV s-1.

3. Results and discussion

3.1. Molecular simulation design molecularly imprinted polymer

3.1.1. Selection of functional monomers

We screened several possible functional monomers, including 3-aminophenylboronic acid (3-APBA), dopamine (DA), 4-vinylpyridine (4-VP), acrylamide (AM), and methacrylic acid (MAA) by computational chemistry. We optimized the molecular structures of the individual molecules and combinations (Dong et al. 2005; Manickam et al. 2017), as shown in Fig.S3 and Fig.S4. The binding energies of the optimized template-functional monomer (AM, 4-AP, MAA, 3-APBA, DA) complexes were calculated, as shown in Table S1. Even though DA and 3-APBA structures have strong interactions with MIPs (Manickam et al. 2017) (hydrogen bonds, π-π stacking, B Lewis acid binding sites), there is still a large spatial distance between the template molecules. According to the value of binding energies, AP+4-VP+MAA were chosen as the appropriate combination of synthetic monomers, as shown in Fig.S5. Because AP and MAA with simple structure have smaller steric hindrance when combined with template molecules, thus hydrogen bonds between them and AP are easier to form. In

addition, the number of hydrogen bonds formed is larger. Therefore, the binding ability of AP+4-VP+MAA is also the largest.

3.1.2. Selection of solvent

The solvent for the experimental reaction requires high solubility of the reaction components without effect on the binding between the template molecule and the functional monomers (Dong et al. 2007). Next, on the premise that AP:4-VP:MAA is 1:1:1, we calculated solvation energies in methanol (MT), ethanol (EA), acetonitrile (ACN), dimethyl sulfoxide (DMSO), chloroform (TCM), tetrahydrofuran (THF), toluene (TL), acetone (ACT), and water (H2O)(Table S2). The |∆E*| in increasing order was found to be: TL
3.1.3. Determination of active sites of functional monomers and template molecules

In order to forecast active sites of functional monomers and template molecules, the molecular electrostatic potentials (MEPs) of AP, MAA and 4-VP were calculated (Liang et al. 2016; Zhang et al. 2018), and the active sites of these substances were determined by their electron cloud distributions. According to the scale shown in the Fig.S6, the stronger the atom’s positive charge is, the closer the electrostatic potential map is to blue, and the more vulnerable the atom will be to attack by nucleophiles. The closer the electrostatic potential graph is to red, the more vulnerable the atom is to the attack by electrophiles. Detailed information provided in the supporting materials. This result further verified that the H12 of AP and the N38 of 4-VP can form a hydrogen bond, and the O20 of AP with H24 of MAA can also form a hydrogen bond.

3.2. Electrochemical characterization of MMIP/MCPE sensors

3.2.1. Characterization by cyclic voltammetry (CV)

As shown in the Fig.1, after the bare electrode MCPE (Fig.1a) and MMIP/MCPE (Fig.1b) were recombined in 1 mmolL-1 AP solution, the cyclic voltammograms were obtained in a PBS buffer solution at pH=6.5. For the bare MCPE electrode, the pair of redox peaks was weak, and for the MMIP/MCPE electrode, the redox peak current was larger, indicating the successful preparation of the MMIP. The results also indirectly indicated that Fe3O4@SiO2 NPs have good coordination ability with AP (Attallah et al. 2018). The cyclic voltammograms on the MMIP/MCPE electrode exhibited an oxidation peak at 0.44V and a reduction peak at 0.38V, indicating that the ratio of the number of electrons and the number of

protons involved in reaction was 1:1. According to the structure of AP, it was inferred that the reaction mechanism that occurs may be as Fig S7.

3.2.2. Template elution and recombination experiments

DPV was used to study the intensity of the oxidation peak current of on different modified electrodes. The AP/Fe3O4@SiO2/MCPE (Fig.S8a) showed a significant oxidation peak current at 0.44V. The peak current on the electrode after elution was basically zero, indicating that the AP had been effectively removed (Fig.S8b). The bare electrodes of MCPE, NIP/MCPE (Fig.S8e), MMIP/MCPE, and Fe3O4@SiO2-free-MIP/MCPE were continuously to be studied in PBS solution after recombination in 80 µmolL-1 AP solution. Compared with other electrodes, the MMIP/MCPE (Fig.S8c) showed a higher current, indicating superior memory recognition ability and binding ability of molecularly imprinted holes to the template molecule. Because the oxidation potential value of AP on the MMIP/MCPE electrode in smaller than that on the bare electrodes MCPE (Fig.S8f) and Fe3O4@SiO2-free-MIP/MCPE (Fig.S8d), the influence of interfering substances can be avoided. 3.2.3. Characterization of effective electrode area

The effective surface areas of different electrodes were explored by cyclic voltammetry (Wang et al. 2018). The average effective area of the MMIP/MCPE after elution of the template molecule was determined to be 0.127±0.004 cm2, which is 1.57 times the effective area of AP/ Fe3O4@SiO2/MCPE (0.081±0.003 cm2), 1.8 times that of NIP/MCPE. (0.070±0.003cm2), 2.8 times that of the bare electrode CPE (0.045±0.002cm2). These results showed that the effective removal of template molecules from the MMIP/MCPE surface left many holes on the surface and increased the specific surface area. In addition, Fe3O4@SiO2 magnetic NPs also increased the effective area of the electrode. 3.2.4. Analysis by Electrochemical Impedance Spectroscopy

Electrochemical impedance spectroscopy (EIS) was used to determine the performance of the electrode surface (Chen et al. 2018). The results in Fig.S9, showed that the MMIP was successfully attached to the electrode, and the electrochemical sensor has excellent performance. The detailed explanation is given in the supporting materials.

3.2.5. Morphological characterization of MMIPs based on Fe3O4@SiO2 NPs As shown in Fig.2, the core-shell structure can be seen clearly in the transmission electron microscopy (TEM) images of Fe3O4@SiO2(A) and MMIP(B). The average particle size of A and B were 296 nm and 342 nm, respectively. The scanning electron microscopy images of Fe3O4@SiO2 (C) and MMIP(D) showed the diameters to be 313 nm and 364 nm, respectively. In addition, the thickness of the imprinted layer was shown to be approximately 25 nm.

3.3. Optimization of experimental conditions

3.3.1. Conditional optimization of synthetic MMIP

The effect of each substance on the synthesis of MIPs was investigated by orthogonal array design (OAD) with an OA9(34) matrix, where A represents the amount of AP, B represents the amount of MAA, C represents the amount of 4-VP, and D represents the amount of nanoparticles. According to the results listed in Table S3, the largest oxidation peak current intensity is the A1B2C2D3.

3.3.2. Optimization of eluent and recombination time

In this paper, acetonitrile, ethanol, SDS, methanol, methanol-acetic acid (volume ratios of 9:1, 8:2, and 7:3) were used as eluents, as shown in Fig.S10. The combined eluent of methanol: acetic acid = 8:2 showed the best experimental results. Recombination can increase the amount of AP and improve the sensitivity of the sensor. The recombination times of MMIP/MCPE (Fig.S11A), Fe3O4@SiO2-free MIP/MCPE (Fig.S11B) and NIP/MCPE (Fig.S11C) were studied in 60 µmol L-1 AP. Compared with the other two electrodes, AP showed a high signal response on the surface of the MMIP/MCPE electrode, and it can be seen that the imprinted molecular polymer has a remarkable ability to recognize the template molecule. Moreover, the interaction between Fe3O4@SiO2 and the molecularly imprinted membrane made the sensor more selective. With increasing accumulation time, the peak current of MMIP/MCPE also increased rapidly, and the current was close to saturation within 25 min. Hence, the optimal accumulation time of 25 min was chosen.

3.3.3. Selection of crosslinking agent

The crosslinking agent is an indispensable linker for the formation of MIPs. If the interaction between the crosslinker and the template molecule is too weak, a stable polymer cannot be formed. On the other hand, a strong interaction will lead to competition between the cross-linking agent and the functional monomer, and the polymers will not easily release the template molecule. Therefore, in this paper, four crosslinkers were experimentally studied: EGDMA, TRIM, TEOS and DVB. The four kinds of cross-linking agents were incorporated into different MMIP/MCPE, and the electrochemical effect was detected by DPV. As shown in Fig.S12, TEOS was more appropriate to the prepared sensor and thus TEOS was selected as the cross-linking agent.

3.3.4. Effect of pH

The

pH

of

the

analyte

solution

also

has

a

large

influence

on the peak current (IP) and the reduction peak voltage (Ep) of the electrode surface. In this experiment,

MMIP/MCPE was reconstituted in a standard solution of 60 µmol L-1, and the peak current was detected in PBS buffer at pH 3.0-8.0. As shown in the Fig.S13, the peak current was the highest at pH 6.5. Because hydroxyl groups of template molecules (AP) and functional monomer (MAA) will dissociate when the buffer solution is too acidic, and reduce the probability of forming MIPs. Furthermore, the electrochemical oxidation is a process in which two protons and two electrons participate, and it is not conducive to the reaction when the buffer solution is alkaline. According to the experimental results, pH 6.5 PBS solution was set as the optimum value. At the same time, it can be clearly seen that Ep decreases linearly with increasing pH value. The linear equation is: Ep = 0.8140-0.0579 pH (r=0.999), and the slope is approximately the theoretical value given by the Nernst equation -0.059V/pH. Further, it is stated that the number of protons and the number of electrons in the reaction are equal.

3.4 Performance evaluation of MCPEs

3.4.1. Analysis of detection limits of sensors

As shown in the Fig.3, under the optimized experimental conditions, the oxidation peak current of AP has a linear relationship with the concentration in two concentration ranges from 6×10-8 to 5×10-5 and from 5×10-5 to 2×10-4 mol L-1. The linear equation in the range of 6×10-8 to 5×10-5 mol L-1 was Ip(µA)=0.484+0.469c(µmol L-1), r=0.9982, as shown in the left side of Figure 3b, and the linear regression equation in the range of 5×10-5 to 2×10-4 mol L-1 was Ip(µA)=23.193+0.122c(µmolL-1), r=0.9973 (Mojtaba and Maryam 2013), as shown in the right side of Figure 3b.

3.4.2. Repeatability, stability and reproducibility AP solutions of 20, 60, 100µmol L-1 were analyzed 6 times by DPV using the same MMIP/MCPE, and the corresponding RSD values were 2.89%, 2.26% and 3.60%, respectively. The prepared sensor was placed in a clean environment, and the electrochemical signal was detected every other week. After 30 days of storage, the electrochemical response signal was the 94.86% of the initial value. At the same time, the reproducibility of the sensor was evaluated by the response of another six independent sensors at the above three concentrations, and the RSDs of the peak currents for 20, 60, 100 µmol L-1 solutions were 3.84%, 3.15%, 3.20%, respectively.

3.4.3. Experimental study on interference of MCPEs

The prepared sensor was used to investigate the selectivity. This article explored substances similar to AP structure, such as para-aminophenol (PAP), acetanilide (AAA) (Fig.S14) and other potentially interfering substances to further evaluate the specificity for AP. As shown in Table S4, the

results were not affected (the error caused by the interference was less than 5%), and a detailed description is given in the supporting materials.

3.4.4. Detection of in actual samples

As shown in Table 1, the sensor prepared in this experiment was evaluated in several actual samples. Tablets (50mg), granules (25mg), Altapharmas (30mg), oral solution (10ml), human serum and urine samples were analyzed by the proposed method. At the 95% confidence level, the results obtained for tablets, granules, effervescent tablets and oral liquid were consistent with those published by the manufacturer. The accuracy of the method and the effect of the sample matrix were studied by recovery experiments. In the appropriate linear range, 10 µM, 50 µM and 100 µM of AP were added to the samples and used for measurements three times. From the results shown in Table 1, it indicating that interference in human serum and urine samples has no influence on the determination of AP. The rates of recovery were from 95.80 to 103.76%, and the RSD range from 0.78% to 3.05%, indicating that the MMIP-based sensor prepared in this experiment be suitable for determining levels of in actual samples. The method of this experiment is compared with other electrochemical methods and non-electrochemical methods are shown in Table 2 and Table S5. As can be seen from the comparison in the tables, the MMIP/MCPE sensor designed in this experiment is more novel and interesting, and the sensor has higher precision and wider linear range for AP. Furthermore, the preparation method is simpler, the cost is lower, and the sensitivity is higher, so this technology has made great contributions to trace analysis of other substances. 4. Conclusion In this paper, an electrochemical sensor based on MMIP was successfully prepared for the determination of AP. Prior to preparing the polymer, the optimal reaction solvent and functional monomers were rationally screened by simulation calculation. This not only saved experimental time and cost, but also made the synthesized product structure more stable and the performance better. Because the synthesized products based on Fe3O4@SiO2 magnetic NPs have strong magnetic properties, the processing of the products was convenient under the action of an external magnetic field. The synergistic effect of Fe3O4@SiO2 and MMIP on the modification of the electrode allowed the electrode surface to have a larger specific surface area and a stronger electrochemical response signal, and realized direct signal conversion between imprinted holes and sensing elements. At the same time, MMIP/MCPE showed obvious performance, avoiding the influence of impurities on the experiment at high electrode potential. Furthermore, MCPE was obtained by embedding a magnet in a CPE electrode, so that it is only necessary to simply fix the magnetic imprinted polymer to the electrode surface under the attraction of a magnetic field without requiring complicated processes. Moreover, the structure of MIPs immobilized on the electrode surface was stable and complete. The next series of electrochemical experiments of MMIP/MCPE in background solutions minimally caused other interference problems, such as template shedding, making the entire sensor more effective and accurate in the detection of AP. In summary, the above-mentioned sensor has many advantages, such as simple operation, low cost,

high sensitivity, high selectivity, good stability, and reproducibility. In addition, the novel sensor developed in this paper lays the foundation for the detection of other substances.

Acknowledgment The authors thank the National Natural Science Foundation of China (No. 11475079), the Scientific Research Foundation for the Returned Overseas Chinese Scholars, State Education Ministry (No. 2015jyb02) and Hunan Provincial Natural Science Foundation of China (No. 2019JJ40244) for financial support.

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Figure Captions

Scheme 1 (a) Schematic diagram of MMIP/MCPE; (b) template extraction-rebinding mechanism. Fig.1 Cyclic voltammograms on the bare electrode MCPE (a) and MMIP/MCPE(b)

Fig.2 The TEM images of Fe3O4@SiO2(A), MMIP(B) and the SEM images of Fe3O4@SiO2(C), MMIP(D) Fig.3 (a) CVs of MMIP/MCPE in different concentrations of AP (from bottom to top): 0.05, 0.1, 0.5, 5, 15, 20.0, 25.0, 40.0, 50.0, 60.0, 70.0 and 100 µmol L-1); (b) show the calibration curves of AP from 6×10-8 to 5×10-5 and from 5×10-5 to 2×10-4 mol L-1

Table legends

Table 1 Determination of AP in tablets, granules, Altapharmas, oral liquid, serum and urine (n=6) Table 2 This method is compared with other electrochemical methods for the determination of acetaminophen

Scheme 1 (a) Schematic diagram of MMIP/MCPE; (b) template extraction-rebinding mechanism.

Fig.1 Cyclic voltammograms on the bare electrode MCPE (a) and MMIP/MCPE(b)

Fig.2 The TEM images of Fe3O4@SiO2(A), MMIP(B) and the SEM images of Fe3O4@SiO2(C), MMIP(D)

Fig.3 (a) CVs of MMIP/MCPE in different concentrations of AP (from bottom to top): 0.05, 0.1, 0.5, 5, 15, 20.0, 25.0, 40.0, 50.0, 60.0, 70.0 and 100 µmol L-1); (b) show the calibration curves of AP from 6×10-8 to 5×10-5 and from 5×10-5 to 2×10-4 mol L-1

Table 1 Determination of AP in tablets, granules, Altapharmas, oral liquid, serum and urine (n=6) Detected by this method Sample

Declared Recovery

RSD

or Added

Found

(%)

(%)

Tablet

50

49.06

-

1.64

Granule

30

31.45

-

2.56

Altapharma

25

26.41

-

2.23

Oral liquid

10

9.12

-

1.21

10

10.21

102.10

0.78

50

51.88

103.76

2.56

100

101.89

101.89

3.05

10

9.58

95.80

0.81

50

49.02

98.04

1.24

100

100.21

100.21

0.98

Serum

Urine

Table 2 This method is compared with other electrochemical methods for the determination of acetaminophen Electrode

Method

Linear range

LOD

(mol L-1)

(mol L-1)

3.50 ×10-6-5.6×10-5

1.02 ×10-6

Au/ZIF-L/GCE

DPV

Au/NPCs–GCE

DPV

1.2×10-7-9.51×10-5

4.94×10-8

PTH/MWCNT/CFE

DPV

2.5×10-5-2.50×10-4

6×10-6

AuNP-PGA/SWCNT

DPV

5×10-5-3.0×10-4

1.5×10-5

5.6×10-5-5.6×10-4

References (Wang et al. 2018) (Li et al. 2019) (Ghica et al. 2015) (Lee et al. 2016) (Nadzirah

Pt/NGr

SWV

-8

-5

-8

-5

-5

-4

5×10 -9×10

8×10

-9

Sofia Anuar 2018)

6×10 -5×10 MMIP/MCPE

DPV

5×10 - 2×10

1.73×10-8

This work

Highlights

1. Development of an innovative magnetic surface molecularly imprinted membrane (MMIP) based on computer-aided design. 2. Fe3O4@SiO2 nanoparticles and molecularly imprinted polymers exhibit distinct synergic effect. 3. The MCPE/MMIP sensor showed highly sensitive and selective for acetaminophen.

Declaration of interest statement We declare that we have no financial and personal relationships with other people or organizations that can inappropriately influence our work, there is no professional or other personal interest of any nature or kind in any product, service and/or company that could be construed as influencing the position presented in the manuscript and supporting materials.

Conflict of interest We claim that we have no conflict of interest in this work. We declare that we do not have any conflict of interest related to the submitted work by a commercial or joint interest representative.