An electrochemical chiral sensor capable of identifying non-electroactive amino acid enantiomers and its preparation method and application

Abstract

The present invention discloses an electrochemical chiral sensor capable of identifying non-electroactive amino acid enantiomers, and a preparation method and application thereof, which belong to the technical field of nanomaterials. The preparation method of the present invention comprises 1. weighing multi-walled carbon nanotubes and β-cyclodextrin, magnetically stirring after ultrasonic dispersion, centrifuging to obtain a precipitate, washing, drying and dispersing in water to obtain a multi-walled carbon nanotube-β-cyclodextrin chiral solution; 2. applying to the electrode surface, volatilizing the solvent under infrared light irradiation, and obtaining a multi-walled carbon nanotube-β-cyclodextrin modified electrode; 3. The multi-walled carbon nanotube-β-cyclodextrin modified electrode is placed in a methylene blue solution for incubation to obtain a methylene blue / multi-walled carbon nanotube-β-cyclodextrin modified electrode. The present invention realizes the selective recognition of non-electroactive amino acid enantiomers, solves the problem that the non-electroactive amino acid enantiomers cannot be recognized by electrochemical technology, and has important application value in electrochemical recognition.

Description

Technical Field

[0001] The invention belongs to the technical field of nanomaterials, and in particular relates to an electrochemical chiral sensor capable of identifying non-electroactive amino acid enantiomers, and a preparation method and application thereof. Technical Background

[0002] Chirality is a common phenomenon in nature, and enantiomers of different configurations generally exhibit completely different biological activities. Electrochemical chiral sensors have attracted the attention of scientists in recent years due to their outstanding advantages such as simple operation, high sensitivity, and broad application prospects. People have used electrochemical technology to identify various chiral isomers with electroactive units, but there is less research on non-electroactive samples because they do not have electroactive units themselves, which makes it impossible for electrochemical technology to identify their chirality.

[0003] Among various nanomaterials, multi-walled carbon nanotubes (MWCNTs) have advantages such as narrow distribution size, large specific surface area, and good conductivity, which make them of high research value. β-cyclodextrin (abbreviated as β-CD) is a molecule with the special properties of hydrophobic inner cavity and hydrophilic outer cavity. Its inner cavity has high molecular recognition and enrichment ability, and can selectively bind a variety of compounds to its hydrophobic cavity to form host-guest inclusion complexes, which makes it of important application value in the construction of chiral sensors. At present, a variety of electrochemical methods based on β-CD have been developed to identify electroactive chiral molecules.

[0004] In order to solve the problem of identifying non-electroactive chiral enantiomers by electrochemical technology, the present invention selects electroactive probe methylene blue (MB for short) as an electrochemical indicator. Due to the host-guest interaction, MB enters the inner cavity of β-cyclodextrin. When non-electroactive amino acid enantiomers exist, they can also form a host-guest with β-cyclodextrin, thereby replacing MB molecules through competitive interaction, resulting in different degrees of reduction in MB oxidation peak current. According to the reduction value of MB oxidation peak current on the electrode surface, selective recognition of proline (Pro) and histidine (His) enantiomers is achieved. Summary of the invention

[0005] In view of the problems existing in the above-mentioned prior art, the purpose of the present invention is to design and provide an electrochemical chiral sensor capable of identifying non-electroactive amino acid enantiomers, and a preparation method and application thereof. The present invention realizes the selective identification of non-electroactive amino acid enantiomers based on the reduction value of the oxidation peak current of methylene blue on the electrode surface, solves the problem that non-electroactive amino acid enantiomers cannot be identified using electrochemical technology, and has important application value in electrochemical identification.

[0006] In order to achieve the above object, the present invention adopts the following technical solutions:

[0007] In one aspect, the present invention provides a method for preparing an electrochemical chiral sensor capable of recognizing non-electroactive amino acid enantiomers, comprising the following steps:

[0008] (1) weighing multi-walled carbon nanotubes, adding β-cyclodextrin, ultrasonically dispersing, magnetically stirring, centrifuging to obtain a precipitate, washing, drying, and dispersing in water to obtain a multi-walled carbon nanotube-β-cyclodextrin chiral solution;

[0009] (2) applying the multi-walled carbon nanotube-β-cyclodextrin chiral solution obtained in step (1) above to the electrode surface, and volatilizing the solvent under infrared light to obtain a multi-walled carbon nanotube-β-cyclodextrin modified electrode;

[0010] (3) The multi-walled carbon nanotube-β-cyclodextrin modified electrode obtained in the above step (2) is placed in a methylene blue solution for incubation to obtain an electroactive probe methylene blue / multi-walled carbon nanotube-β-cyclodextrin modified electrode.

[0011] The method for preparing an electrochemical chiral sensor capable of identifying non-electroactive amino acid enantiomers, wherein the mass volume ratio of multi-walled carbon nanotubes, β-cyclodextrin and water in step (1) is 2-8 mg: 3.4-11.3 mg: 1-5 mL, and the concentration of β-cyclodextrin is 3-10 mM.

[0012] In the method for preparing an electrochemical chiral sensor capable of identifying non-electroactive amino acid enantiomers, the volume of the multi-walled carbon nanotube-β-cyclodextrin chiral solution in step (2) is 1 to 10 μL, and the electrode comprises a glassy carbon electrode.

[0013] In the method for preparing an electrochemical chiral sensor capable of identifying non-electroactive amino acid enantiomers, the concentration of the methylene blue solution in step (3) is 0.02 to 0.07 mM, and the incubation time is 5 to 35 minutes.

[0014] In a second aspect, the present invention provides an electrochemical chiral sensor capable of identifying non-electroactive amino acid enantiomers, which is obtained by any of the preparation methods described above.

[0015] In a third aspect, the present invention provides an application of the electrochemical chiral sensor in identifying non-electroactive amino acid enantiomers, characterized in that the non-electroactive amino acid enantiomers include proline enantiomers and histidine enantiomers.

[0016] In a fourth aspect, a method for identifying non-electroactive amino acid enantiomers using an electrochemical chiral sensor employs differential pulse voltammetry to identify non-electroactive amino acid enantiomers.

[0017] The method specifically includes: taking an electrochemical chiral sensor, placing it in an L-amino acid solution and a D-amino acid solution for incubation, then taking it out and rinsing it with a phosphate buffer solution, placing it in a phosphate buffer solution, and testing and identifying it using differential pulse voltammetry under the electrochemical window.

[0018] In the method, the concentrations of the L-amino acid solution and the D-amino acid solution are both 0.1-1 mM, the volumes are both 20-30 mL, and the incubation time is 5-35 min.

[0019] In the method, the concentration of the phosphate buffer solution is 0.1M and the pH is 7.0; the voltage of the electrochemical window is -0.35 to -0.05V.

[0020] Compared with the prior art, the present invention has the following beneficial effects:

[0021] In the present invention, an electroactive substance MB (methylene blue) and an inactive amino acid enantiomer are selected as a signal probe and a target molecule, respectively, and a competitive host-guest recognition system is constructed for electrochemical recognition of the inactive amino acid enantiomer. Due to the host-guest interaction, MB enters the inner cavity of β-cyclodextrin. When the inactive amino acid enantiomer exists, they can also form a host-guest with β-cyclodextrin, thereby replacing the MB molecule through competitive interaction, resulting in a different degree of reduction in the MB oxidation peak current. According to the reduction value of the MB oxidation peak current, the selective recognition of Pro and His enantiomers is achieved, the problem of using electrochemical technology to recognize inactive chiral samples is solved, and the range of electrochemical chiral recognition is expanded. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 The scanning electron microscope images of MWCNTs (A), MWCNTs-β-CD (B) and MB / MWCNTs-β-CD (C) in Example 1 and the EDS mapping elemental image of MB / MWCNTs-β-CD (D);

[0023] Figure 2 is the infrared spectra of MWCNTs, β-CD and MWCNTs-β-CD in Example 1;

[0024] Figure 3 GCE, MWCNTs / GCE, MWCNTs-β-CD / GCE and MB / MWCNTs-β-CD / GCE in Example 2 were prepared in the presence of 5 mM [Fe(CN)6] 4- / 3- Cyclic voltammogram in 0.1M KCl solution;

[0025] Figure 4GCE, MWCNTs / GCE, MWCNTs-β-CD / GCE and MB / MWCNTs-β-CD / GCE in Example 2 were prepared in the presence of 5 mM [Fe(CN)6] 4- / 3- The AC impedance diagram in 0.1M KCl solution;

[0026] Figure 5 The differential pulse voltammograms of MB / β-CD / GCE, MWCNTs-β-CD / GCE and MB / MWCNTs-β-CD / GCE in 0.1 M PBS at pH 7.0 in Example 3;

[0027] Figure 6 is a graph showing the relationship between MB oxidation peak current and the incubation time of MWCNTs-β-CD / GCE in MB solution in Example 4;

[0028] Figure 7 This is the differential pulse voltammogram of the MB / MWCNTs-β-CD / GCE incubated with the Pro enantiomer in 0.1 M PBS at pH 7.0 in Example 5;

[0029] Figure 8 This is the differential pulse voltammogram of MB / MWCNTs-β-CD / GCE incubated with His enantiomer in 0.1 M PBS at pH 7.0 in Example 6;

[0030] Fig. 9 is the differential pulse voltammogram of Pro enantiomer incubated with GCE in Comparative Example 1 in 0.1 M PBS at pH 7.0;

[0031] Fig.10 This is the differential pulse voltammogram of the His enantiomer incubated with GCE in Comparative Example 2 in 0.1 M PBS at pH 7.0. DETAILED DESCRIPTION

[0032] The present invention will be further described below in conjunction with the accompanying drawings and embodiments. The following embodiments are intended to illustrate the present invention rather than to further limit the present invention.

[0033] The MB / MWCNTs-β-CD modified electrode (methylene blue / multi-walled carbon nanotubes-β-cyclodextrin modified electrode) of the present invention recognizes Pro and His enantiomers according to the following method:

[0034] R=ΔI L / ΔI D

[0035] In the formula, R represents the recognition efficiency; △I LIt indicates the decrease of MB oxidation peak current after MB / MWCNTs-β-CD modified electrode was incubated in L-amino acid solution; △I D It indicates the decrease of MB oxidation peak current after the MB / MWCNTs-β-CD modified electrode was incubated in D-amino acid solution.

[0036] Embodiment 1:

[0037] The preparation of MB / MWCNTs-β-CD modified electrodes with electroactive probes includes the following steps:

[0038] (1) Weigh 2 mg of MWCNTs, add 1 mL of 10 mM β-CD solution, ultrasonically disperse for 30 min, magnetically stir for 12 h to fully mix, centrifuge the obtained solid, wash, and dry. Take 2 mg of the obtained solid and disperse it in 1 mL of water to obtain a 2 mg / mL MWCNTs-β-CD chiral solution;

[0039] (2) using a pipette to transfer 5 μL of the chiral solution prepared in step (1) and drop it onto the surface of the glassy carbon electrode, and evaporating the solvent under infrared light to obtain a MWCNTs-β-CD modified electrode;

[0040] (3) Incubate the modified electrode prepared in step (2) in a 0.05 mM MB solution for 30 min to obtain an electroactive probe MB / MWCNTs-β-CD modified electrode.

[0041] like Figure 1 As shown in the figure, the morphology of MWCNTs, MWCNTs-β-CD, and MB / MWCNTs-β-CD was studied by scanning electron microscopy, and the EDS mapping element analysis of MB / MWCNTs-β-CD was also performed. Figure 1 As shown in A, the surface of MWCNTs presents a typical nanotube structure entangled with each other, with a tube diameter of about 29 nm. Figure 1 B shows that the diameter of β-CD functionalized MWCNTs becomes thicker, about 49 nm. Figure 1 A has larger pores, which is conducive to the entry of guest molecules. Figure 1 C is the SEM image of MB after incubation with MWCNTs-β-CD. The pore structure is still retained after incubation, indicating that its surface morphology is not destroyed. EDS was used to analyze the elemental composition of MB / MWCNTs-β-CD, confirming the presence of C, O, S and N elements ( Figure 1 D), where the S and N elements are derived from MB, confirming that MB can bind to MWCNTs-β-CD via host-guest interactions.

[0042] like Figure 2The infrared spectra of MWCNTs, β-CD and MWCNTs-β-CD are shown in Figure 2. For MWCNTs, 1536 cm -1 The peak at 3424 cm is a typical C=C stretching vibration peak. -1 The peak at 1161 cm -1 The peak at 1083 cm corresponds to the C–O–C asymmetric glycoside vibration. -1 The peak at 1035 cm corresponds to the stretching vibration of C–C. -1 The peak at corresponds to the stretching vibration of C–O. The above characteristic peaks of MWCNTs and β-CD can be observed in the FT-IR image of MWCNTs-β-CD.

[0043] Embodiment 2:

[0044] The MB / MWCNTs-β-CD modified electrode prepared in Example 1, as well as the GCE (i.e., glassy carbon electrode), MWCNTs modified electrode, and MWCNTs-β-CD modified electrode were placed in a solution containing 5 mM [Fe(CN)6] 4- / 3- The cyclic voltammetry method was used to test the electrochemical performance in the electrochemical window of –0.6 to 0.6 V in 0.1 M KCl solution.

[0045] like Figure 3 As shown, GCE exhibits a pair of obvious [Fe(CN)6] 4- / 3- Redox peak, which is attributed to the solution [Fe(CN)6] 4- / 3- After modification of MWCNTs, [Fe(CN)6] 4- / 3- The redox peak current was significantly enhanced, which was mainly attributed to the super strong electron transfer ability of MWCNTs, which accelerated the electron transfer and led to a significant increase in the peak current. 4- / 3- The redox peak current value decreased because the conductivity of β-CD was weak, which hindered the electron transfer. The MWCNTs-β-CD / GCE modified electrode was further incubated in MB solution for 30 min, [Fe(CN)6] 4- / 3- The redox peak current further decreased compared with that of MWCNTs-β-CD / GCE, which may be because β-CD can form an inclusion complex with MB, thereby preventing the redox probe [Fe(CN)6] 4- / 3- Since MB is an electroactive probe, a pair of smaller redox current peaks were observed at –0.17 to –0.21 V, indicating that MB has bound to β-CD through host-guest interaction. Figure 4The AC impedance diagram of different modified electrodes shows the following trend according to the size of charge transfer impedance: GCE (98.84Ω) > MB / MWCNTs-β-CD / GCE (41.67Ω) > MWCNTs-β-CD / GCE (28.67Ω) > MWCNTs / GCE (10.31Ω). The AC impedance test results of different electrodes are consistent with the cyclic voltammetry results of each electrode.

[0046] Embodiment 3:

[0047] The MB / MWCNTs-β-CD modified electrode prepared in Example 1 and the MB / β-CD and MWCNTs-β-CD modified electrodes were tested by differential pulse voltammetry in a 0.1 M PBS solution with a pH of 7.0 at an electrochemical window of -0.35 to -0.05 V.

[0048] like Figure 5 As shown in the figure, after MWCNTs-β-CD / GCE was incubated in MB solution, the oxidation peak current of MB was observed at about –0.21V, while no MB oxidation peak appeared on MWCNTs-β-CD / GCE without incubation in MB solution, indicating that β-CD and MB successfully formed a host-guest inclusion complex. It is worth noting that the oxidation peak current of MB / MWCNTs-β-CD / GCE is much larger than that of MB / β-CD / GCE, because MWCNTs can enhance the electron transport capacity, and its large specific surface area can stably load β-CD, thereby combining more MB through host-guest inclusion.

[0049] Embodiment 4:

[0050] The MWCNTs-β-CD modified electrode obtained in Example 1 was used to investigate the changes in the oxidation peak current of MB in 0.1M PBS with a pH of 7.0 after the electrode was incubated in 0.05mM MB solution for different time periods. Figure 6 It can be seen that the oxidation peak current of MB increases with the increase of incubation time and reaches the maximum value at 30 min. Therefore, 30 min was selected as the optimal incubation time of the modified electrode in MB solution.

[0051] Embodiment 5:

[0052] The MB / MWCNTs-β-CD / GCE prepared in Example 1 was incubated in 25 mL of 1 mM L-Pro and D-Pro solutions for 30 min, respectively, taken out of the solution and rinsed with 0.1 M PBS, and the changes in the oxidation peak current of MB were recorded by differential pulse voltammetry.

[0053] like Figure 7As shown, compared with before incubation, the oxidation peak current of MB after binding with the Pro enantiomer decreased to varying degrees. According to the reduction value of the oxidation peak current of MB, the selective recognition of the Pro enantiomer was achieved, and the recognition efficiency reached 2.16.

[0054] Embodiment 6:

[0055] The MB / MWCNTs-β-CD / GCE prepared in Example 1 was incubated in 25 mL of 1 mM L-His and D-His solutions for 30 min, respectively, taken out of the solution and rinsed with 0.1 M PBS, and the changes in the oxidation peak current of MB were recorded by differential pulse voltammetry.

[0056] like Figure 8 As shown, compared with before incubation, the oxidation peak current of MB after binding with the His enantiomer decreased to varying degrees. According to the reduction value of the oxidation peak current of MB, the selective recognition of the His enantiomer was achieved, and the recognition efficiency reached 1.99.

[0057] Comparative Example 1:

[0058] GCE recognition of Pro enantiomers: GCE was placed in 25 mL of 1 mM L-Pro and D-Pro solutions for 30 min, then removed from the solution and rinsed with 0.1 M PBS. The changes in the oxidation peak current of MB were recorded by differential pulse voltammetry. Fig. 9 As shown, bare GCE is unable to recognize the inactive Pro enantiomer.

[0059] Comparative Example 2:

[0060] GCE recognition of His enantiomers: GCE was placed in 25 mL of 1 mM L-His and D-His solutions for 30 min, then removed from the solution and rinsed with 0.1 M PBS. The changes in the oxidation peak current of MB were recorded by differential pulse voltammetry. Fig.10 As shown, naked GCE is unable to recognize the non-electroactive His enantiomer.

[0061] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A method for preparing an electrochemical chiral sensor capable of identifying non-electroactive amino acid enantiomers, characterized in that: The following steps are involved: (1) weighing multi-walled carbon nanotubes, adding β-cyclodextrin, ultrasonically dispersing, magnetically stirring, centrifuging to obtain a precipitate, washing, drying, and dispersing in water to obtain a multi-walled carbon nanotube-β-cyclodextrin chiral solution; (2) applying the multi-walled carbon nanotube-β-cyclodextrin chiral solution obtained in step (1) to the electrode surface, and volatilizing the solvent under infrared light to obtain a multi-walled carbon nanotube-β-cyclodextrin modified electrode; (3) The multi-walled carbon nanotube-β-cyclodextrin modified electrode obtained in the above step (2) is placed in a methylene blue solution for incubation to obtain an electroactive probe methylene blue / multi-walled carbon nanotube-β-cyclodextrin modified electrode.

2. The method for preparing an electrochemical chiral sensor capable of identifying non-electroactive amino acid enantiomers according to claim 1, characterized in that: In the step (1), the mass volume ratio of multi-walled carbon nanotubes, β-cyclodextrin and water is 2-8 mg: 3.4-11.3 mg: 1-5 mL, and the concentration of β-cyclodextrin is 3-10 mM.

3. The method for preparing an electrochemical chiral sensor capable of identifying non-electroactive amino acid enantiomers according to claim 1, characterized in that: In the step (2), the volume of the multi-walled carbon nanotube-β-cyclodextrin chiral solution is 1 to 10 μL, and the electrode comprises a glassy carbon electrode.

4. The method for preparing an electrochemical chiral sensor capable of identifying non-electroactive amino acid enantiomers according to claim 1, characterized in that: In the step (3), the concentration of the methylene blue solution is 0.02-0.07 mM, and the incubation time is 5-35 min.

5. An electrochemical chiral sensor capable of identifying non-electroactive amino acid enantiomers, characterized in that The method is obtained by the preparation method according to any one of claims 1 to 4.

6. Use of the electrochemical chiral sensor according to claim 5 in identifying non-electroactive amino acid enantiomers, characterized in that: The non-electroactive amino acid enantiomers include proline enantiomers and histidine enantiomers.

7. A method for identifying non-electroactive amino acid enantiomers using an electrochemical chiral sensor as claimed in claim 5, characterized in that: Identification of electroactive amino acid enantiomers using differential pulse voltammetry.

8. The method according to claim 7, characterized in that Specifically include: Take the electrochemical chiral sensor, place it in L-amino acid solution and D-amino acid solution for incubation respectively, then take it out and rinse it with phosphate buffer solution, place it in phosphate buffer solution, and use differential pulse voltammetry to test and identify it in the electrochemical window.

9. The method according to claim 8, characterized in that The concentrations of the L-amino acid solution and the D-amino acid solution are both 0.1-1 mM, the volumes are both 20-30 mL, and the incubation time is 5-35 min.

10. The method according to claim 8, characterized in that The concentration of the phosphate buffer solution is 0.1M, and the pH is 7.0; the voltage of the electrochemical window is -0.35 to -0.05V.

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