Cinnamaldehyde rapid detection electrochemical sensor and preparation and application thereof

Abstract

The invention discloses a cinnamyl aldehyde rapid detection electrochemical sensor as well as preparation and application thereof, and relates to the field of electrochemical sensors. The method comprises the following steps: preparing an N-G dispersion liquid, preparing an N-G-coated GCE modified electrode, and preparing the MIP / N-G-coated GCE molecularly imprinted electrochemical sensor. According to the preparation method, cinnamyl aldehyde is taken as a template molecule, methacrylic acid is taken as a functional monomer, a molecularly imprinted polymer film is prepared on the surface of a nitrogen-doped graphene modified glassy carbon electrode in a self-assembly manner, and the molecularly imprinted electrochemical sensor MIP / N-G-GCE which is high in selectivity, high in sensitivity and rapid in detection of the index component cinnamyl aldehyde and is used for evaluating the quality of cinnamon is developed. The sensor shows relatively low detection limit, relatively wide linear range and relatively high selectivity, and when the molecularly imprinted electrochemical sensor is used for analyzing cinnamyl aldehyde in a traditional Chinese medicine extract, the recovery rate is relatively high, so that the molecularly imprinted electrochemical sensor has a good application prospect.

Description

Technical Field

[0001] The present invention relates to the field of electrochemical sensors, and in particular to a cinnamaldehyde rapid detection electrochemical sensor and a preparation method and application thereof. Background Art

[0002] The traditional Chinese medicine cinnamon (Cinnamomum cassia Presl), the dried bark of the cinnamon tree of the Lauraceae family, is a representative example of traditional Chinese medicinal and edible plants. Its history of use can be traced back to the Shennong Bencao Jing (Shen Nong's Classic of Materia Medica), where it is listed as a top-grade medicinal material. Cinnamon is not only widely cultivated in Fujian, Guangdong, Guangxi, and Yunnan provinces of China, but has also become a global hotspot in natural medicine research due to its unique pharmacological activities. Modern pharmacological research has shown that cinnamon exhibits antibacterial, anti-inflammatory, antioxidant, anti-diabetic, and potentially anti-cancer properties. Its core active ingredient, cinnamaldehyde, is key to these biological activities. Cinnamaldehyde, a monoterpene aldehyde, not only promotes blood circulation, relieves muscle spasms, and relieves rheumatic pain, but has also been shown to inhibit the release of inflammatory factors by regulating the NF-κB and MAPK signaling pathways, showing promising potential in the prevention and treatment of chronic diseases. Furthermore, cinnamaldehyde is increasingly used in the food industry as a natural preservative and flavoring. Therefore, accurate and rapid detection of the cinnamaldehyde content in cinnamon medicinal materials and their derivatives is not only the key to ensuring their medicinal and economic value, but also the necessary technical support for promoting the modernization and internationalization of traditional Chinese medicine.

[0003] Currently, the detection of cinnamaldehyde relies primarily on traditional analytical techniques such as high-performance liquid chromatography (HPLC) and gas chromatography-mass spectrometry (GC-MS). While these methods offer high sensitivity and accuracy, their limitations are significant. HPLC requires complex pretreatment steps and expensive columns, GC-MS's reliance on volatile components limits its application in complex matrices, and spectroscopic methods are susceptible to matrix interference, resulting in limited selectivity. Furthermore, these methods are generally limited by bulky instruments, long detection cycles, and specialized operator requirements, making them inadequate for point-of-care testing in traditional Chinese medicine production sites, distribution channels, and end-use markets. A low-cost, portable, and highly sensitive detection method is urgently needed to achieve comprehensive quality control from raw materials to finished products. In recent years, electrochemical sensing technology has become a research hotspot in the analytical field due to its advantages such as rapid response, low cost, and amenability to miniaturization. Molecularly imprinted electrochemical sensing technology, among others, has been widely used in various fields, including pharmaceutical analysis and food testing, due to its fast response, ease of operation, ease of on-site analysis, low preparation cost, and high stability. Summary of the Invention

[0004] The present invention addresses the aforementioned deficiencies in the prior art and aims to provide an electrochemical sensor for rapid detection of cinnamaldehyde, as well as its preparation and application. The present invention develops a highly selective and sensitive molecularly imprinted electrochemical sensor for rapid detection of cinnamaldehyde. This facilitates rapid monitoring of cinnamaldehyde, an intrinsic microscopic component of cinnamon, in formulas, simplifies detection procedures, reduces testing costs, and shortens testing cycles. This plays a crucial role in ensuring the high quality, efficacy, and overall quality control of cinnamon-containing compound preparations. It also provides a forward-looking exploration of the application of electrochemical analysis technology in the quality evaluation and medication safety of traditional Chinese medicines.

[0005] In order to achieve the above object, the present invention adopts the following technical solutions: In a first aspect, the present invention provides a method for preparing a cinnamaldehyde rapid detection electrochemical sensor, comprising the following steps: (1) Preparation of NG dispersion Weigh 2 mg of nitrogen-doped graphene (NG) and disperse it in deionized water. Ultrasonic dispersion was performed for 2 h to obtain a 2 mg / mL NG dispersion. The dispersion was stored in a refrigerator at 4 °C until ready for use. (2) Preparation of NG@GCE modified electrodes A glassy carbon electrode (GCE) was polished to a mirror finish on chamois leather using 0.3 μm and 0.05 μm alumina powders, respectively. The GCE was then ultrasonically cleaned for 3 minutes with ultrapure water and anhydrous ethanol, dried at room temperature, and set aside. 10 μL of NG dispersion was drop-coated on the dried GCE surface and dried under an infrared lamp to obtain an NG@GCE modified electrode. (3) Preparation of MIP / NG@GCE molecularly imprinted electrochemical sensor 0.5 mg of cinnamaldehyde was dissolved in a mixed solution of 90 μL of methacrylic acid (MAA) and 0.5 mL of dimethyl sulfoxide (DMSO) and sonicated at room temperature for 10 min to form a pre-assembled system. 1.2 mL of ethylene glycol dimethacrylate (EGDMA) and 4.3 mg of azobisisobutyronitrile (AIBN) were added and sonicated for another 10 min to prepare a MIP prepolymer solution. 2 μL of the MIP prepolymer solution was evenly drop-coated on an NG@GCE modified electrode and dried in an oven at 40°C for 2 h. Cyclic voltammetry was performed at a scan rate of 100 mV / s between -0.4 V and 0.8 V. The prepared MIP / NG@GCE modified electrode was immersed in a methanol / acetic acid mixture with a volume ratio of 9:1 for 15 min and then gently rinsed with distilled water to remove the attached acetic acid and cinnamaldehyde, thereby obtaining a MIP / NG@GCE molecularly imprinted electrochemical sensor.

[0006] In a second aspect, the present invention provides a cinnamaldehyde rapid detection electrochemical sensor, which is prepared by the above-mentioned preparation method.

[0007] In a third aspect, the present invention proposes an application of a cinnamaldehyde rapid detection electrochemical sensor for detecting the cinnamaldehyde content in cinnamon Chinese medicinal materials or compound preparations containing cinnamon. The cinnamaldehyde rapid detection electrochemical sensor has a good linear relationship between the oxidation peak current value and the cinnamaldehyde concentration in the cinnamaldehyde concentration range of 0.1 to 1000 ng / mL, with a correlation coefficient of 0.87292. The linear regression equation is expressed as Ip=-0.00564C+17.291, and the detection limit is 5.3×10 -2 ng / mL, signal-to-noise ratio S / N=3, Ip is the oxidation peak current, unit is μA, C is the concentration, unit is ng / mL.

[0008] Compared with the prior art, the present invention has the following beneficial technical effects: the present invention uses cinnamaldehyde as a template molecule and methacrylic acid (MAA) as a functional monomer to prepare a molecularly imprinted polymer film by self-assembly on the surface of a nitrogen-doped graphene (NG)-modified glassy carbon electrode, and develops a molecularly imprinted electrochemical sensor MIP / NG@GCE with high selectivity, high sensitivity and rapid detection of cinnamaldehyde, an indicator component for cinnamon quality evaluation. The sensor exhibits a low detection limit, a wide linear range and high selectivity. When the molecularly imprinted electrochemical sensor is used to analyze cinnamaldehyde in traditional Chinese medicine extracts, the recovery rate is high, and the sensor has good application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] Figure 1 This is a schematic diagram of the construction principle of a cinnamaldehyde rapid detection electrochemical sensor in an embodiment of the present invention.

[0010] Figure 2 : are the physical and chemical structure characterization diagrams of the materials in the embodiments of the present invention, where a is the SEM image of MIP / NG@GCE before elution, b is the SEM image of MIP / NG@GCE after elution, c is the XRD diagram of NG, and d is the FT-IR diagram of NG.

[0011] Figure 33 is an electrochemical characterization diagram of the basic electrode in an embodiment of the present invention in a 2 mM potassium ferrocyanide / potassium ferrocyanide base solution, a is the CV curve of (a) GCE and (b) NG@GCE, b is the EIS curve of (a) GCE and (b) NG@GCE, c is the CV curve of MIP / NG@GCE at a scan rate of 10 to 130 mV / s, d is the relationship between peak current and scan rate, e is the chronocoulometry curve of (a) GCE, (b) NG@GCE, (c) MIP / NG@GCE before elution, and (d) MIP / NG@GCE after elution; f is the Q-t1 / 2 curve of (a) GCE, (b) NG@GCE, (c) MIP / NG@GCE before elution, and (d) MIP / NG@GCE after elution.

[0012] Figure 4 Figure 2 is the electrochemical characterization diagram of the MIP / NG@GCE electrochemical sensor in an embodiment of the present invention in a base solution containing 2 mM potassium ferrocyanide / potassium ferrocyanide, (a) is the CV curve of MIP / NG@GCE before elution, (b) MIP / NG@GCE after elution, (c) recombined MIP / NG@GCE, and (d) NIP / NG@GCE after elution, (b) is the EIS curve of MIP / NG@GCE before elution, (b) MIP / NG@GCE after elution, (c) recombined MIP / NG@GCE, and (d) NIP / NG@GCE after elution.

[0013] Figure 5 Figure 3 is a DPV characterization diagram of the MIP / NG@GCE electrochemical sensor in an embodiment of the present invention in a base solution containing 2 mM potassium ferrocyanide / potassium ferrocyanide. (a) shows the DPV response of cinnamaldehyde at different concentrations of 0.1 ng to 1000 ng / mL, and (b) shows the linear relationship between different concentrations of cinnamaldehyde and the corresponding DPV values.

[0014] Figure 6 Detection results of (a) repeatability, (b) reproducibility, (c) stability, and (d) specificity of the MIP / NG@GCE electrochemical sensor in the embodiment of the present invention. DETAILED DESCRIPTION

[0015] The following is a clear and complete description of the technical solutions of the present invention in conjunction with the embodiments. Obviously, the embodiments described are only some of the embodiments of the present invention, not all of them. All other embodiments derived by persons of ordinary skill in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0016] In the present invention, unless otherwise specified, all raw materials involved are commercially available products well known in the art.

[0017] Example like Figure 1 As shown, the present embodiment provides a method for preparing a cinnamaldehyde rapid detection electrochemical sensor, which uses nitrogen-doped graphene (NG) as a glassy carbon electrode (GCE) modification material, cinnamaldehyde as a template molecule, and methacrylic acid (MAA) as a functional monomer. A molecularly imprinted polymer film is prepared by self-assembly on the surface of the nitrogen-doped graphene-modified glassy carbon electrode, and a molecularly imprinted electrochemical sensor with high selectivity, high sensitivity and rapid detection of cinnamaldehyde, an indicator component of cinnamon quality evaluation, is developed. The specific steps are as follows: (1) Preparation of NG dispersion Weigh 2 mg of nitrogen-doped graphene (NG) and disperse it in deionized water. Ultrasonic dispersion was performed for 2 h to obtain a 2 mg / mL NG dispersion. The dispersion was stored in a refrigerator at 4 °C until ready for use. (2) Preparation of NG@GCE modified electrodes A glassy carbon electrode (GCE) was polished to a mirror finish on chamois leather using 0.3 μm and 0.05 μm alumina powders, respectively. The GCE was then ultrasonically cleaned for 3 minutes with ultrapure water and anhydrous ethanol, dried at room temperature, and set aside. 10 μL of NG dispersion was drop-coated on the dried GCE surface and dried under an infrared lamp to obtain an NG@GCE modified electrode. (3) Preparation of MIP / NG@GCE molecularly imprinted electrochemical sensor 0.5 mg of cinnamaldehyde was dissolved in a mixed solution of 90 μL of methacrylic acid (MAA) and 0.5 mL of dimethyl sulfoxide (DMSO) and sonicated at room temperature for 10 min to form a pre-assembled system. 1.2 mL of ethylene glycol dimethacrylate (EGDMA) and 4.3 mg of azobisisobutyronitrile (AIBN) were added and sonicated for another 10 min to prepare a MIP prepolymer solution. 2 μL of the MIP prepolymer solution was evenly drop-coated on an NG@GCE modified electrode and dried in an oven at 40°C for 2 h. Cyclic voltammetry was performed at a scan rate of 100 mV / s between -0.4 V and 0.8 V. The prepared MIP / NG@GCE modified electrode was immersed in a methanol / acetic acid mixture with a volume ratio of 9:1 for 15 min and then gently rinsed with distilled water to remove the attached acetic acid and cinnamaldehyde, thereby obtaining a MIP / NG@GCE molecularly imprinted electrochemical sensor.

[0018] Without adding the template molecule cinnamaldehyde, the non-imprinted composite electrode NIP / NG@GCE was prepared according to the above steps in the example.

[0019] like Figure 2As shown in the figure, after the MIP / NG@GCE modified electrode was constructed, it was characterized by infrared spectroscopy, XRD, and SEM electron microscopy. Figure 2 The test results show that NG dispersion, NG@GCE modified electrode and MIP / NG@GCE molecular imprinting electrochemical sensor were successfully prepared.

[0020] Electrochemical characterization is then carried out, aiming to characterize the preparation and performance of the electrode through electrochemical testing methods.

[0021] In the presence of 5mmol [Fe(CN)6] 3- / 4- The modified electrodes were characterized by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) in 0.1 mol KCl and 0.1 mol KCl solutions. CV measurements were performed at a potential range of –0.4 V to 0.8 V and a scan rate of 100 mV / s. EIS measurements were performed at an amplitude of 0.005 V, a voltage of 0.2 V, and a frequency range of 0.1 to 10 5 Hz.

[0022] Cyclic voltammetry (CV) scanning was performed on GCE and NG@GCE, and the results were as follows: Figure 3 As shown. Compared with GCE, the peak current of NG@GCE is significantly larger, indicating that NG enhances the conductivity of the electrode. This may be because the modification of NG increases the specific surface area of ​​the electrode and increases the charge transfer efficiency on the electrode surface. In the EIS spectrum, the diameter of the semicircle can be used to evaluate the charge transfer resistance (Rct) of the electrode. The larger the semicircle diameter, the greater the charge transfer resistance. Figure 3 Figure b shows the charge transfer resistance: GCE (950 Ω) > NG (707 Ω). The NG-modified electrode significantly reduces resistance, demonstrating its excellent conductivity. Comparing the EIS results with those from cyclic voltammetry confirms their mutual support, demonstrating that the modified electrode exhibits enhanced electron transfer capabilities.

[0023] Figure 3 The test results showed that NG dispersion and NG / GCE modified electrodes were successfully prepared; the electrochemical effective specific surface areas of GCE and NG / GCE electrodes were 0.107 cm 2 、0.168cm 2 .

[0024] CV and EIS methods were used to characterize the MIP-NG@GCE before elution, after elution, and recombined MIP-NG@GCE. Figure 4 As can be seen in a, the current changes significantly before and after the template molecule is eluted, indicating that the elution effect is good. Figure 4b shows the EIS results, combined with the following: MIP / NG@GCE (1871 Ω); MIP / NG@GCE before elution (2837 Ω); NIP / NG@GCE (1020.8 Ω); and MIP / NG@GCE after elution (692 Ω). The resistance values ​​of the imprinted and non-imprinted electrodes before template removal are similar. This is because the adsorption of template molecules on the electrode surface hinders electron transfer from the probe molecules. The polymer layer on the non-imprinted composite electrode cannot accelerate electron transfer, resulting in higher resistance for both electrodes. The resistance of MIP / NG@GCE after elution is the lowest, as the elution leaves many cavities on the electrode surface that can provide electron transfer for the probe molecules, resulting in a lower resistance.

[0025] Under the optimized conditions, the gradient concentration samples were tested and the test results were as follows. Figure 5 It can be seen that within the cinnamaldehyde concentration range of 0.1 to 1000 ng / mL, the oxidation peak current value and the cinnamaldehyde concentration have a good linear relationship, with a correlation coefficient of 0.87292. The linear regression equation is expressed as Ip=-0.00564C+17.291, and the detection limit is 5.3×10 -2 ng / mL, signal-to-noise ratio S / N=3, Ip is the oxidation peak current, unit is μA, C is the concentration, unit is ng / mL.

[0026] To verify the practicality of the sensor of the embodiment, a MIP / NG / GCE electrode was prepared under the optimal experimental conditions and tested 5 times continuously. The test results are as follows: Figure 6 As shown in a. The calculated RSD is 0.75%, indicating that the sensor has good repeatability. Figure 6 As shown in Figure b, 5 electrodes were prepared under the same conditions and the same concentration of cinnamaldehyde was detected to explore the reproducibility of the electrode. The calculated RSD was 0.51%, indicating that the sensor has good reproducibility. Figure 6 As shown in c, in order to explore the stability of the sensor prepared in this study, the prepared electrode was placed at room temperature and measured and recorded every 5 days. The change ranges were 2.81%, 1.86%, 1.49%, and 0.83%, respectively. The results show that the sensor has good stability. In order to further explore the specificity of the sensor, the sensor was tested with four different interfering substances (the concentration of the interfering substance was 10 times the concentration of the target substance). The selected interfering substances were cinnamic acid, benzaldehyde, formaldehyde, and acetic acid. After the interfering substances were added to the detection system, the change ranges of the peak current were 3.62% for benzaldehyde, 0.37% for cinnamic acid, 1.64% for formaldehyde, and 3.00% for acetic acid. Figure 6d It can be seen that the effect of interfering substances on the ability of the sensor to specifically recognize cinnamaldehyde is negligible, which indicates that the sensor has good specificity.

[0027] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent replacements and improvements made within the technical solution and conceptual invention of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for preparing a cinnamaldehyde rapid detection electrochemical sensor, characterized in that: The following steps are involved: (1) Preparation of NG dispersion Weigh 2 mg of NG and disperse it in deionized water. Ultrasonic dispersion was performed for 2 h to obtain a 2 mg / mL NG dispersion. The solution was stored in a refrigerator at 4 °C until use. (2) Preparation of NG@GCE modified electrode GCE was polished to a mirror finish using 0.3 μm and 0.05 μm alumina powders on suede, followed by ultrasonic cleaning with ultrapure water and anhydrous ethanol for 3 minutes, respectively, and dried at room temperature for later use. 10 μL of NG dispersion was drop-coated on the dried GCE surface and dried under an infrared lamp to obtain an NG@GCE modified electrode. (3) Preparation of MIP / NG@GCE molecularly imprinted electrochemical sensor 0.5 mg of cinnamaldehyde was dissolved in a mixed solution containing 90 μL of MAA and 0.5 mL of DMSO, and sonicated at room temperature for 10 min to form a pre-assembled system. 1.2 mL of EGDMA and 4.3 mg of AIBN were added and sonicated for another 10 min to prepare a MIP prepolymer solution. 2 μL of the MIP prepolymer solution was evenly drop-coated on an NG@GCE modified electrode and dried in an oven at 40°C for 2 h. Cyclic voltammetry was performed by scanning between -0.4 V and 0.8 V at a rate of 100 mV / s. The prepared MIP / NG@GCE modified electrode was immersed in a methanol / acetic acid mixed eluent with a volume ratio of 9:1 for 15 min. The eluted MIP / NG@GCE modified electrode was then gently rinsed with distilled water to remove the attached acetic acid and cinnamaldehyde, thereby obtaining a MIP / NG@GCE molecularly imprinted electrochemical sensor.

2. A cinnamaldehyde rapid detection electrochemical sensor, characterized in that: Prepared by the preparation method according to claim 1.

3. An application of the cinnamaldehyde rapid detection electrochemical sensor according to claim 2 in detecting the cinnamaldehyde content in cinnamon Chinese medicinal materials or compound preparations containing cinnamon, wherein the cinnamaldehyde rapid detection electrochemical sensor has a good linear relationship between the oxidation peak current value and the cinnamaldehyde concentration in the cinnamaldehyde concentration range of 0.1 to 1000 ng / mL, with a correlation coefficient of 0.87292, and its linear regression equation is expressed as Ip=-0.00564C+17.291, with a detection limit of 5.3×10 -2 ng / mL, signal-to-noise ratio S / N=3, Ip is the oxidation peak current, unit is μA, C is the concentration, unit is ng / mL.

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