Preparation method and application of fluorescent carbon quantum dots taking apigenin as carbon source
The preparation of apigenin carbon quantum dots by hydrothermal method solved the problem of poor solubility of apigenin, achieved efficient photodynamic antibacterial properties, and broadened its application in the biomedical field.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- CHANGZHOU UNIV
- Filing Date
- 2024-04-16
- Publication Date
- 2026-06-30
AI Technical Summary
Apigenin has poor solubility in water, resulting in poor antibacterial effect. Furthermore, it is easily affected by gastrointestinal enzymes and pH in vivo, thus limiting its clinical application.
A bottom-up approach was used to prepare apigenin carbon quantum dots with fluorescent effects by ultrasonically dispersing apigenin powder with 0.01-1M KOH solution, followed by hydrothermal reaction and freeze-drying.
The prepared apigenin carbon quantum dots have nanoscale size, good water solubility and efficient photodynamic antibacterial properties, which broadens their application in the biomedical field.
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Figure CN118374282B_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of fluorescent and antibacterial carbon nanomaterials technology, specifically relating to a method for preparing and applying fluorescent carbon quantum dots using apigenin as a carbon source. Background Technology
[0002] Apigenin is a flavonoid compound and a major active ingredient in plants such as *Selaginella tamariscina* (family Selaginellaceae) and *Apium sempervirens* (family Apiaceae). It possesses antitumor, anti-inflammatory, antibacterial, antiviral, antihypertensive, and anti-atherosclerotic effects. Apigenin has significant development potential, but its water solubility is only 1.35 μg / mL, and its low dissolution rate makes it susceptible to the effects of gastrointestinal enzymes and pH in vivo. This low water solubility may lead to drug delivery problems, such as poor transdermal absorption, unstable absorption, and low oral bioavailability, thus limiting its clinical application. Currently, there are reports on the formulation of apigenin into phospholipid complexes, self-microemulsions, and nanosuspensions. However, phospholipid complexes have poor stability, self-microemulsion formulations contain large amounts of surfactants, and nanosuspensions have the problem of residual dimethyl sulfoxide.
[0003] Carbon quantum dots (CQDs) have attracted widespread attention due to their excellent physical and chemical properties. CQDs are generally produced using a bottom-up approach, which is low-cost, reliable, and allows for large-scale production from natural resources via a green route. The resulting CQDs have a richer surface area with more functional groups, making them easier to derivatize and functionalize, thus readily yielding CQDs with specific properties and functions. Furthermore, CQDs exhibit significant advantages in water solubility, modifiability, and resistance to photobleaching, while also possessing low biotoxicity and good biocompatibility, making them potentially valuable for applications in bioimaging, biosensing, and drug delivery. Natural products already used for CQD preparation include chitosan, lotus root, curcumin, and mango peel. However, these natural substances require pretreatment to extract components soluble in the aqueous or organic phases for use as raw materials for CQD preparation. The complex composition and susceptibility to variations in raw material type and geographical region lead to uncertainties and instabilities in the synthesized CQDs, ultimately affecting their application performance. Summary of the Invention
[0004] The purpose of this invention is to provide a method for preparing apigenin carbon quantum dots with highly efficient photodynamic antibacterial properties, so as to overcome the problems of poor solubility of apigenin and the resulting poor antibacterial effect.
[0005] The method for preparing fluorescent carbon quantum dots provided by this invention includes the following steps:
[0006] (1) Dissolution: Apigenin powder was dispersed in 0.01-1M KOH solution by ultrasonic dispersion to obtain a yellow transparent solution;
[0007] (2) Reaction: The yellow transparent solution was transferred to a high-pressure reactor for hydrothermal reaction to obtain a brownish-red apigenin carbon quantum dot dispersion;
[0008] (3) Filtration and freeze drying: After heating is completed, the carbon quantum dot dispersion is naturally cooled to room temperature, filtered, pH is adjusted and freeze-dried to obtain apigenin carbon quantum dots with fluorescent effect.
[0009] As a preferred embodiment of the method for preparing fluorescent carbon quantum dots with photodynamic antibacterial properties according to the present invention:
[0010] (1) The dissolution is as follows: accurately weigh 20-50 mg of apigenin into a beaker, add 20 mL of 0.01-1 MkOH solution, stir to dissolve, and obtain a yellow transparent solution.
[0011] (2) The reaction is as follows: the yellow transparent solution obtained in step (1) is transferred to a high-pressure reactor and hydrothermally reacted at 150-210℃ for 10h to obtain a brownish-red apigenin carbon quantum dot dispersion. The maximum wavelength of the fluorescence emission spectrum of the obtained apigenin carbon quantum dot dispersion is 550nm.
[0012] (3) Filtration and freeze-drying: After heating, the mixture was allowed to cool naturally to room temperature. The carbon quantum dot dispersion was filtered through a 0.22 μm microporous membrane. The pH of the filtrate was adjusted to 6-13 with 1M HCl solution. Finally, the mixture was freeze-dried at -56℃ and a vacuum of 5 Pa for 48 h to obtain fluorescent carbon quantum dots with highly efficient photodynamic antibacterial properties. The mixture was then stored at 4℃ in the dark for later use.
[0013] The fluorescent carbon quantum dots obtained by the above method are used as photodynamic antibacterial materials.
[0014] The beneficial effects of this invention are as follows:
[0015] (1) The apigenin carbon quantum dots prepared by the present invention have nanoscale size, good water solubility and superior fluorescence properties.
[0016] (2) The apigenin carbon quantum dots prepared by the present invention have efficient photodynamic antibacterial properties and good antibacterial performance under 400nm ultraviolet light irradiation, which can broaden the research and application of apigenin in the biomedical field.
[0017] (3) The preparation method of this invention is simple, green and environmentally friendly. It uses a low concentration of KOH solution to prepare apigenin carbon quantum dots by hydrothermal method, which provides a new way for the preparation of carbon quantum dots. Attached image description:
[0018] Figure 1 This is a transmission electron microscope image of the apigenin carbon quantum dots prepared in Example 1;
[0019] Figure 2 This is the infrared absorption spectrum of the apigenin carbon quantum dots prepared in Example 1;
[0020] Figure 3 These are the fluorescence emission spectra of apigenin carbon quantum dots prepared in Examples 1-6 under different pH conditions;
[0021] Figure 4 These are the fluorescence emission spectra of apigenin carbon quantum dots prepared in Examples 1, 7, and 8 at different reaction temperatures;
[0022] Figure 5 These are the fluorescence emission spectra of the apigenin carbon quantum dots prepared in Examples 1, 9, and 10;
[0023] Figure 6 This is a diagram showing the antibacterial effect of apigenin carbon quantum dots prepared in Example 1 on Escherichia coli and Staphylococcus aureus in a dark environment.
[0024] Figure 7 This is a diagram showing the antibacterial effect of apigenin carbon quantum dots prepared in Example 1 on Escherichia coli and Staphylococcus aureus under 400nm ultraviolet light. Detailed Implementation
[0025] The present invention will be described in further detail below with reference to specific embodiments. These embodiments are merely illustrative of the invention and are not intended to limit the scope of the invention in any way.
[0026] Example 1
[0027] Weigh 50 mg of apigenin into a beaker, add 20 mL of 0.1 M KOH solution, and stir until dissolved to obtain a yellow transparent solution. Transfer the solution to a high-pressure reactor and react at 210 °C for 10 h to obtain a brownish-red apigenin carbon quantum dot dispersion. After heating, allow it to cool naturally to room temperature. Filter the carbon quantum dot dispersion through a 0.22 μm microporous membrane. After filtration, adjust the pH of the reaction solution to 10 using 1 M HCl solution. Finally, freeze-dry (-56 °C, vacuum 5 Pa) for 48 h to obtain apigenin carbon quantum dots with highly efficient photodynamic antibacterial properties.
[0028] Figure 1 This is a TEM image of the apigenin carbon quantum dots prepared in Example 1, with a size range of 4.0-12.5 nm and an average size of 7.8 nm.
[0029] Figure 2 This is the infrared spectrum of the apigenin carbon quantum dots prepared in Example 1, with the image showing 3380 cm⁻¹. -1 The peak at 2975 cm⁻¹ represents the stretching vibration of the phenolic hydroxyl group (O–H). -1 With 1410cm -1The peak is the CH2 stretching vibration peak, 1661 cm⁻¹. -1 and 1627cm -1 Characteristic peaks at 1579 cm⁻¹, respectively, are assigned to C=O and C=C. -1 The skeletal peak of the aromatic ring is 1280 cm⁻¹. -1 Characteristic peaks for cyclic ethers, 1170 and 1008 cm⁻¹ -1 The peak at this location corresponds to the stretching vibration of C–O–C.
[0030] Figure 6 The image shows the antibacterial effect of apigenin carbon quantum dots (6 mg / mL) prepared in Example 1 on Escherichia coli (left) and Staphylococcus aureus (right) under light-free conditions. No obvious antibacterial effect was observed.
[0031] Figure 7 The image shows the antibacterial effect of apigenin carbon quantum dots (6 mg / mL) prepared in Example 1 on Escherichia coli (left) and Staphylococcus aureus (right) under 400 nm ultraviolet light irradiation for 40 min. The antibacterial rate against Escherichia coli reached 95%, and the antibacterial rate against Staphylococcus aureus reached 87%.
[0032] Example 2
[0033] Weigh 50 mg of apigenin into a beaker, add 20 mL of 0.1 M KOH solution, and stir until dissolved. Transfer the solution to a high-pressure reactor and react at 210 °C for 10 h. Filter using a 0.22 μm microporous membrane, and adjust the pH of the reaction solution to 13 using 1 M HCl solution. Finally, freeze-dry (-56 °C, vacuum 5 Pa) for 48 h to obtain apigenin carbon quantum dots.
[0034] Example 3
[0035] Weigh 50 mg of apigenin into a beaker, add 20 mL of 0.1 M KOH solution, and stir until dissolved. Transfer the solution to a high-pressure reactor and react at 210 °C for 10 h. Filter using a 0.22 μm microporous membrane, and adjust the pH of the reaction solution to 9 using 1 M HCl solution. Finally, freeze-dry (-56 °C, vacuum 5 Pa) for 48 h to obtain apigenin carbon quantum dots.
[0036] Example 4
[0037] Weigh 50 mg of apigenin into a beaker, add 20 mL of 0.1 M KOH solution, and stir until dissolved. Transfer the solution to a high-pressure reactor and react at 210 °C for 10 h. Filter using a 0.22 μm microporous membrane, and adjust the pH to 8 with 1 M HCl solution after filtration. Finally, freeze-dry (-56 °C, vacuum 5 Pa) for 48 h to obtain apigenin carbon quantum dots.
[0038] Example 5
[0039] Weigh 50 mg of apigenin into a beaker, add 20 mL of 0.1 M KOH solution, and stir until dissolved. Transfer the solution to a high-pressure reactor and react at 210 °C for 10 h. Filter using a 0.22 μm microporous membrane, and adjust the pH of the reaction solution to 7 using 1 M HCl solution. Finally, freeze-dry (-56 °C, vacuum 5 Pa) for 48 h to obtain apigenin carbon quantum dots.
[0040] Example 6
[0041] Weigh 50 mg of apigenin into a beaker, add 20 mL of 0.1 M KOH solution, and stir until dissolved. Transfer the solution to a high-pressure reactor and react at 210 °C for 10 h. Filter using a 0.22 μm microporous membrane, and adjust the pH of the reaction solution to 6 using 1 M HCl solution. Finally, freeze-dry (-56 °C, vacuum 5 Pa) for 48 h to obtain apigenin carbon quantum dots.
[0042] Figure 3 The images show a comparison of the fluorescence intensity of apigenin carbon quantum dots prepared in Examples 1-6 at an excitation wavelength of 500 nm. The carbon quantum dots exhibit the highest fluorescence intensity at pH=10, and the solution displays green fluorescence under ultraviolet light.
[0043] Example 7
[0044] Weigh 50 mg of apigenin into a beaker, add 20 mL of 0.1 M KOH solution, and stir until dissolved. Transfer the solution to a high-pressure reactor and react at 180 °C for 10 h. Filter using a 0.22 μm microporous membrane, and adjust the pH of the reaction solution to 10 using 1 M HCl solution. Finally, freeze-dry (-56 °C, vacuum 5 Pa) for 48 h to obtain apigenin carbon quantum dots.
[0045] Example 8
[0046] Weigh 50 mg of apigenin into a beaker, add 20 mL of 0.1 M KOH solution, and stir until dissolved. Transfer the solution to a high-pressure reactor and react at 150 °C for 10 h. Filter using a 0.22 μm microporous membrane, and adjust the pH of the reaction solution to 10 using 1 M HCl solution. Finally, freeze-dry (-56 °C, vacuum 5 Pa) for 48 h to obtain apigenin carbon quantum dots.
[0047] Figure 4 The fluorescence emission spectra of apigenin carbon quantum dots prepared at three different reaction temperatures in Examples 1, 7, and 8 show that the fluorescence intensity increases with increasing reaction temperature.
[0048] Example 9
[0049] 20 mg of apigenin was weighed into a beaker and 20 mL of 0.1 M KOH solution was added and stirred until dissolved. The solution was transferred to a high-pressure reactor and reacted at 210 °C for 10 h. The mixture was filtered through a 0.22 μm microporous membrane, and the pH of the reaction solution was adjusted to 10 using 1 M HCl solution. Finally, the mixture was freeze-dried (-56 °C, vacuum 5 Pa) for 48 h to obtain apigenin carbon quantum dots. Fluorescence emission spectroscopy analysis showed that the fluorescence intensity of the carbon quantum dots was weak at this stage, and no obvious photoluminescence properties were observed.
[0050] Example 10
[0051] Weigh 35 mg of apigenin into a beaker, add 20 mL of 0.1 M KOH solution, and stir until dissolved. Transfer the solution to a high-pressure reactor and react at 210 °C for 10 h. Filter using a 0.22 μm microporous membrane, and adjust the pH of the reaction solution to 10 using 1 M HCl solution. Finally, freeze-dry (-56 °C, vacuum 5 Pa) for 48 h to obtain apigenin carbon quantum dots. Figure 5 The fluorescence emission spectra of Examples 1, 9, and 10 are shown. The fluorescence intensity of Examples 9 and 10 is significantly weaker than that of Example 1.
[0052] Example 11
[0053] 10 mg of apigenin (at maximum solubility) was weighed into a beaker, and 20 mL of 0.01 M KOH solution was added and stirred until dissolved. The solution was transferred to a high-pressure reactor and reacted at 210 °C for 10 h. The mixture was filtered through a 0.22 μm microporous membrane, and the pH of the reaction solution was adjusted to 10 using 0.1 M HCl solution. Finally, the mixture was freeze-dried (-56 °C, vacuum 5 Pa) for 48 h to obtain apigenin carbon quantum dots. Fluorescence emission spectroscopy analysis showed that the fluorescence intensity of the carbon quantum dots was weak at this stage, possibly due to the low concentration of carbon quantum dots.
[0054] Example 12
[0055] 50 mg of apigenin was placed in a beaker, and 20 mL of 1 M KOH solution was added and stirred until dissolved. The solution was transferred to a high-pressure reactor and reacted at 210 °C for 10 h. The mixture was filtered through a 0.22 μm microporous membrane, and the pH of the reaction solution was adjusted to 10 using 1 M HCl solution. Finally, the mixture was freeze-dried (-56 °C, vacuum 5 Pa) for 48 h to obtain apigenin carbon quantum dots. Fluorescence emission spectroscopy analysis showed that the fluorescence intensity of the carbon quantum dots was significantly weaker than that in Example 1, and no obvious photoluminescence properties were observed.
[0056] Comparative Example 1
[0057] 20 mg of apigenin was weighed and dissolved in 20 mL of ethanol by stirring. The solution was then transferred to a high-pressure reactor and reacted at 210 °C, 200 °C, and 180 °C for 10 h each. After the reaction, the solution was filtered through a 0.22 μm microporous membrane to obtain a carbon quantum dot dispersion. Fluorescence emission spectroscopy analysis showed that the dispersion did not exhibit obvious photoluminescence properties, and transmission electron microscopy revealed no formation of carbon quantum dots.
[0058] Comparative Example 2
[0059] 20 mg of apigenin was weighed into a beaker, and 5 mL of DMF and 10 mL of deionized water were added and stirred until dissolved. The solution was transferred to a high-pressure reactor and reacted at 210 °C, 200 °C, and 180 °C for 10 h each. After the reaction, the solution was filtered through a 0.22 μm microporous membrane to obtain a carbon quantum dot dispersion. Fluorescence emission spectroscopy analysis showed that the dispersion did not exhibit obvious photoluminescence properties, and transmission electron microscopy revealed no formation of carbon quantum dots.
[0060] When ethanol and DMF are used as solvents, the carbon quantum dot solution does not exhibit obvious photoluminescence properties. This invention reveals that apigenin is difficult to prepare into carbon quantum dots in organic solvents such as ethanol and DMF, as well as in water, but can be successfully prepared in KOH solution. This is likely because KOH solution is alkaline, which causes the phenolic hydroxyl groups in apigenin to lose protons, forming anion, which then forms a salt with K ions, thus allowing it to exist stably in water.
[0061] Unless otherwise specified, specific conditions were applied in the embodiments. Reagents and instruments used, unless otherwise stated, are all commercially available products. Unless otherwise specified, the methods used in this invention are conventional methods in the art. The above descriptions are merely preferred embodiments of the present invention and are not intended to limit the invention. Any modifications made to the above embodiments based on the technical essence of this invention are included within the scope of protection of this invention.
Claims
1. A fluorescent carbon quantum dot using apioin as a carbon source, characterized by: The preparation method of the carbon quantum dots is as follows: 1) Dissolution: Dissolve apigenin powder in KOH solution to form a yellow transparent solution; the mass-to-volume ratio of apigenin to KOH solution is 5mg:2ml, and the concentration of KOH solution is 0.1M; 2) Reaction: The yellow transparent solution was transferred to a high-pressure reactor for hydrothermal reaction to obtain a brownish-red apigenin carbon quantum dot dispersion; the hydrothermal reaction temperature was 150-210℃ and the hydrothermal reaction time was 10h. 3) Filtration and freeze-drying: After filtering the carbon quantum dot dispersion, the pH was adjusted and then freeze-dried to obtain apigenin carbon quantum dots with fluorescent effect; The freeze-drying conditions are: -56℃, vacuum degree 5Pa. 2.The fluorescent carbon quantum dots according to claim 1, characterized in that: The hydrothermal reaction is as follows: the KOH solution of apigenin is transferred to a 50mL high-pressure reactor, and a brownish-red apigenin carbon quantum dot dispersion is obtained after the reaction.
3. The fluorescent carbon quantum dot according to claim 1, characterized in that: The maximum emission wavelength of the fluorescence emission spectrum of the apigenin carbon quantum dot dispersion is 550 nm.
4. The fluorescent carbon quantum dot according to claim 1, characterized in that: The process of adjusting pH after filtration and then freeze-drying involves filtering the cooled carbon quantum dot dispersion through a 0.22 μm microporous membrane, adjusting the pH of the dispersion to 6-13, and then freeze-drying to obtain apigenin carbon quantum dots, which are then stored at 4°C in the dark for later use.
5. An application of the fluorescent carbon quantum dot according to any one of claims 1-4, characterized in that: The fluorescent carbon quantum dots are used as photodynamic antibacterial materials.