D-glutamic acid-doped forsythia carbon quantum dots, a preparation method and application thereof
By preparing D-glutamic acid-doped Forsythia carbon quantum dots, bacterial cell walls are disrupted and enzyme activity is inhibited, solving the problem of poor efficacy of existing inhibitors and achieving a highly efficient and stable bacterial inhibition effect.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- QINGDAO AGRI UNIV
- Filing Date
- 2024-03-15
- Publication Date
- 2026-07-07
AI Technical Summary
Existing inhibitors of bacterial cell wall synthesis have limited antibacterial effects or unstable activity. Some of these drugs also have side effects and are prone to drug resistance, necessitating the development of novel inhibitors.
Forsythia carbon quantum dots doped with D-glutamic acid were prepared by hydrothermal reaction. These quantum dots were used to disrupt bacterial cell walls, bind to MurD enzyme to inhibit enzyme activity, increase cell wall permeability, induce bacteria to produce reactive oxygen species, and accelerate bacterial apoptosis.
It significantly enhances the antibacterial effect against Escherichia coli and Staphylococcus aureus, destroys cell walls, increases permeability, induces the production of reactive oxygen species, inhibits bacterial growth, and is less likely to induce drug resistance.
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Figure CN118185624B_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of bacterial control technology, specifically relating to a D-glutamic acid-doped Forsythia carbon quantum dot, its preparation method, and its application. Background Technology
[0002] Peptidoglycan is an important component of bacterial cell walls, and amide ligases MurC, MurD, MurE, and MurF are involved in peptidoglycan synthesis. Amide ligases catalyze the binding of intermediate products to D-glutamate to form peptidoglycan. MurD enzymes have a strong affinity for D-glutamate.
[0003] Bacterial cell walls protect the bacterial cell from osmotic pressure fluctuations. When cell wall synthesis is inhibited, the cell wall is damaged, the cell loses its protection, and the bacteria gradually die. Different drugs interfere with bacterial cell wall synthesis through different mechanisms. Currently, different inhibitors have been developed based on the different stages of drug action. Inhibitors that act on the first stage of the bacterial cell wall synthesis pathway include MurA inhibitors, MurB inhibitors, and MurC-F inhibitors; those that act on the second stage include MurY inhibitors and MurG inhibitors; and those that act on the third stage include transglycosylase inhibitors and transpeptidase inhibitors.
[0004] Clinically, commonly used drugs that inhibit cell wall synthesis include penicillins, cephalosporins, carbapenems, and fosfomycin. Fosfomycin is a MurA inhibitor. MurA (pyruvate transferase) is the target of fosfomycin, a widely used antibiotic in clinical practice. Fosfomycin's mechanism of action involves competing with phosphoenolpyruvate for pyruvate transferase, thereby inhibiting the first step of cell wall synthesis. Carbapenems work by binding to bacterial transglycosylases, specifically penicillin-binding proteins, to achieve their antibacterial effect; they are transglycosylase inhibitors. Penicillins and cephalosporins are typical transpeptidase inhibitors, inhibiting enzyme activity by competing with substrates for the active site of transpeptidases. Currently used drugs that inhibit bacterial cell wall synthesis have significant antibacterial effects, but some antibiotics have certain side effects and are prone to drug resistance. Therefore, there is a need to develop novel bacterial inhibitors.
[0005] Inhibitors that are not widely used also suffer from problems such as weak or unstable antibacterial activity. For example, the efficacy of MurB inhibitors is affected by MurA, which is why they are not widely used; most MurC-F inhibitors have no antibacterial activity or no significant antibacterial activity, and warrant further investigation. Summary of the Invention
[0006] This invention provides a method for preparing D-glutamic acid-doped Forsythia carbon quantum dots, the steps of which are as follows:
[0007] Forsythia powder and D-glutamic acid were added to water for a hydrothermal reaction. The reaction solution was centrifuged, the supernatant was collected and filtered, and the filtrate was dried to obtain D-glutamic acid-doped Forsythia carbon quantum dots.
[0008] In the above preparation method, the mass parts of each component are as follows: 1.25-1.5 parts of Forsythia powder, 0.2-0.5 parts of D-glutamic acid, and 60-66 parts of water.
[0009] In one specific implementation, the mass fractions of each component are as follows: 1.25 parts of Forsythia suspensa powder, 0.2 parts of D-glutamic acid, and 60 parts of water.
[0010] In the above preparation method, the hydrothermal reaction conditions are selected from: heating the reaction at 180-200℃ for 6-8 hours.
[0011] This invention provides D-glutamic acid-doped forsythia carbon quantum dots prepared by the above method.
[0012] This invention provides the application of the above-mentioned D-glutamic acid-doped Forsythia carbon quantum dots in the preparation of formulations or drugs that inhibit pathogenic bacteria. The pathogenic bacteria are preferably Escherichia coli and / or Staphylococcus aureus.
[0013] The present invention provides an inhibitor for Escherichia coli and / or Staphylococcus aureus, the inhibitor containing the above-mentioned D-glutamic acid-doped Forsythia carbon quantum dots.
[0014] The beneficial effects of this invention are as follows:
[0015] In this invention, D-glutamic acid-doped Forsythia carbon quantum dots can disrupt bacterial cell walls, increase cell wall permeability, and even completely break down the cell walls, allowing contents to leak out. Simultaneously, the carbon quantum dots entering the bacterial interior can induce the production of reactive oxygen species, accelerating bacterial apoptosis. Furthermore, the carbon quantum dots described in this invention can inhibit the activity of MurD ligase by competitively binding to D-glutamic acid, thereby inhibiting bacterial wall synthesis. Attached Figure Description
[0016] Figure 1 TEM images of LQ-CDs and D / LQ-CDs; the left image is of LQ-CDs and the right image is of D / LQ-CDs.
[0017] Figure 2 FT-IR spectra of LQ-CDs and D / LQ-CDs;
[0018] Figure 3 XRD patterns of LQ-CDs and D / LQ-CDs; where the upper curve represents LQ-CDs and the lower curve represents D / LQ-CDs.
[0019] Figure 4 The images show the fluorescence emission spectra of LQ-CDs and D / LQ-CDs; the left image represents LQ-CDs, and the right image represents D / LQ-CDs.
[0020] Figure 5 The inhibition rates of LQ-CDs and D / LQ-CDs against Escherichia coli and Staphylococcus aureus;
[0021] Figure 6 The results are from the coating experiment;
[0022] Figure 7 SEM images of Escherichia coli and Staphylococcus aureus treated with LQ-CDs and D / LQ-CDs;
[0023] Figure 8 The results of the experiment were influenced by the biofilm.
[0024] Figure 9 Results of bacterial conductivity measurement;
[0025] Figure 10 These are the results of reactive oxygen species measurement;
[0026] Figure 11 This is the result of the total protein content determination;
[0027] Figure 12 The results are from the determination of the amount of nucleic acid leakage.
[0028] Figure 13 This is the result of ATPase activity assay. Detailed Implementation
[0029] The materials used in this invention are as follows:
[0030] Forsythia was purchased from the wholesale market in Chengyang District, Qingdao City, and D-glutamic acid was purchased from Aladdin (Shanghai) Reagent Company.
[0031] Other materials used in this invention, unless otherwise stated, are commercially available. Other terms used in this invention, unless otherwise specified, generally have the meanings commonly understood by those skilled in the art. The invention is further described in detail below with reference to specific embodiments and data. The following embodiments are merely illustrative and not intended to limit the scope of the invention in any way.
[0032] Example 1
[0033] Preparation of carbon quantum dots from Forsythia suspensa:
[0034] Forsythia suspensa was ground into powder. 1.25 g of the powder was mixed thoroughly with 60 mL of ultrapure water, and the mixture was transferred to a hydrothermal reactor lined with 100 mL of polytetrafluoroethylene. The mixture was heated at 180 °C for 6 h. The resulting product was centrifuged at 10000 g for 30 min. After centrifugation, the supernatant was filtered through a 0.22 μm aqueous PES filter. The filtrate was collected and centrifuged at 3000 g for 20 min using a 10 kDa ultrafiltration centrifuge tube. The resulting filtrate was then freeze-dried under vacuum to obtain Forsythia suspensa carbon quantum dot powder, i.e., LQ-CDs.
[0035] Example 2
[0036] Preparation of D-glutamic acid-doped Forsythia carbon quantum dots:
[0037] Forsythia suspensa was ground into powder. 1.25 g of Forsythia suspensa powder, 0.2 g of D-glutamic acid, and 60 mL of ultrapure water were mixed thoroughly. The mixture was transferred to a hydrothermal reactor lined with 100 mL of polytetrafluoroethylene. The mixture was heated at 180 °C for 6 h. The resulting product was centrifuged at 10000 g for 30 min. After centrifugation, the supernatant was filtered through a 0.22 μm aqueous PES filter. The filtrate was collected and centrifuged at 3000 g for 20 min through a 10 kDa ultrafiltration centrifuge tube. The resulting filtrate was then freeze-dried under vacuum to obtain D-glutamic acid-doped Forsythia suspensa carbon quantum dot powder, i.e., D / LQ-CDs.
[0038] I. Characterization of carbon quantum dots
[0039] The two types of carbon quantum dots, LQ-CDs and D / LQ-CDs, were characterized as follows:
[0040] The morphology of carbon quantum dots (CDs) was analyzed using transmission electron microscopy (TEM). XRD images were obtained using X-ray polycrystalline diffraction. FT-IR spectra were recorded using Fourier transform infrared spectroscopy (FT-IR); FT-IR spectroscopy can analyze the surface functional groups of CDs. The UV absorption spectra and fluorescence spectra of carbon quantum dots at different excitation wavelengths were recorded using a multi-functional microplate reader. All the above characterization methods were conventional.
[0041] The test results are as follows Figures 1-4 As shown:
[0042] Figure 1 TEM images of LQ-CDs and D / LQ-CDs are shown. Figure 1 It is evident that both types of CDs have a relatively uniform spherical shape and a particle size of less than 10 nm, consistent with the particle size distribution characteristics of CDs. This nanoscale particle size range also provides them with potential for antibacterial applications. Previous studies have generally held that CDs with a particle size smaller than 10 nm can penetrate into bacteria and kill them due to their small size.
[0043] Figure 2 The FT-IR spectra of LQ-CDs and D / LQ-CDs are shown. Figure 2 It can be seen that both CDs coexist at 3300cm -1 The broad peak corresponds to the stretching vibrations of OH and NH; 2927 cm⁻¹ -1 The peak at that location corresponds to CH cm -1 The stretching vibration; 1651cm -1 The peak at 1600 cm corresponds to C=C stretching vibration; -1 The peak at 1376 cm corresponds to the skeletal vibration of C=C; -1 The corresponding bending vibration of COC is 1246 cm. -1 The corresponding point is the CN stretching vibration, 1037 cm. -1 The corresponding point corresponds to CO tensile vibration.
[0044] Figure 3 XRD images of LQ-CDs and D / LQ-CDs are shown. Figure 3 It can be seen that LQ-CDs show diffraction peaks at around 22°, while D / LQ-CDs show diffraction peaks at around 21°, indicating that the two CDs have graphite-like structures.
[0045] Figure 4 The fluorescence excitation spectra of LQ-CDs and D / LQ-CDs are shown. Figure 4 The fluorescence excitation spectra show that both CDs exhibit fluorescence properties. With changing excitation wavelength, the fluorescence intensity initially increases and then decreases. Furthermore, the fluorescence peak red-shifts with increasing excitation wavelength.
[0046] II. Antibacterial Properties Study
[0047] 1. Antibacterial rate determination
[0048] Escherichia coli and Staphylococcus aureus are two major foodborne pathogens. These two bacteria were selected to test the antibacterial activity of LQ-CDs and D / LQ-CDs.
[0049] Escherichia coli and Staphylococcus aureus were cultured to a bacterial concentration of 1×10⁻⁶. 7 CFU / mL. Mix 100 μL of sterile culture medium with 100 μL of carbon quantum dot solution, and then dilute the carbon quantum dot solution using a two-fold dilution method. The final concentrations of carbon quantum dots were 10, 5, 2.5, 1.25, 0.625, and 0.3125 mg / mL. LB broth was used as a negative control instead of bacterial culture, and bacterial culture was used as a positive control instead of drug solution. The mixture was incubated at 37℃ for 12 h. The absorbance of each well was observed at 600 nm using a microplate reader. The final inhibition rate was calculated using the following formula:
[0050]
[0051] In the formula, OD 600测 This refers to the absorbance of the experimental group at 600 nm; OD 600阳对 This refers to the absorbance at 600 nm of the control group where the bacterial culture replaced the drug solution; OD 600阴对 This refers to the absorbance at 600 nm of the control group using LB broth as a substitute for bacterial culture; OD 600样 This refers to the absorbance of different carbon quantum dots at 600 nm.
[0052] The test results are as follows Figure 5 As shown:
[0053] Both LQ-CDs and D / LQ-CDs exhibit antibacterial activity, with higher inhibition rates against Staphylococcus aureus than against Escherichia coli. High concentrations of LQ-CDs (10 mg / mL) showed inhibition rates of 69% and 72% against Escherichia coli and Staphylococcus aureus, respectively. D / LQ-CDs, doped with D-glutamic acid, demonstrated even higher antibacterial activity, with maximum inhibition rates exceeding 90% and 96% against these two bacteria, respectively.
[0054] 2. Evaluation of the antibacterial effect of CDs using the coating method
[0055] To more intuitively observe the antibacterial effect of CDs, the antibacterial ability of LQ-CDs and D / LQ-CDs was evaluated using the plate coating method.
[0056] Escherichia coli and Staphylococcus aureus were activated and cultured to a concentration of 1×10⁻⁶. 7 To obtain a final concentration of CFU / mL, mix 2 mL of bacterial culture with 1 mL of carbon quantum dot solution dissolved in PBS to achieve a final carbon quantum dot concentration of 3 mg / mL. Incubate at 37°C with shaking for 4 h. Spread 50 μL of the bacterial culture evenly onto the surface of sterile LB solid medium and incubate at 37°C for 12 h.
[0057] Experimental results are as follows Figure 6 As shown:
[0058] CDs exhibited antibacterial effects against both types of bacteria. Both CDs showed greater inhibitory activity against Staphylococcus aureus than against Escherichia coli, and D / LQ-CDs demonstrated significantly stronger antibacterial activity than LQ-CDs. These results indicate that D / LQ-CDs possess more significant antibacterial activity.
[0059] 3. Study the antibacterial properties of CDs at the cellular level.
[0060] (1) Observation of bacterial morphology
[0061] The effects of CDs on the cell walls of Escherichia coli and Staphylococcus aureus were observed using SEM.
[0062] Add 1 mL of activated bacterial solution (1×10) 7 The bacterial culture was mixed with 1 mL of CDs solution (10 mg / mL) and incubated at 37 °C for 12 h. The cultured bacterial solution was centrifuged at 2500 rpm for 5 min and then washed and resuspended with sterile PBS. The resuspended bacterial solution was then fixed with glutaraldehyde and osmium tetroxide. The sample was washed with PBS and then dried using a gradient of 30%, 50%, 70%, 90%, and 100% ethanol. After gold sputtering, the dried sample was observed using a scanning electron microscope (SEM) to examine the bacterial surface.
[0063] The test results are as follows Figure 7 As shown:
[0064] SEM images show the changes on the surface of two types of bacteria after treatment with CDs, thus recording the effect of CDs on bacterial morphology. Figure 7 It was observed that untreated *Escherichia coli* and *Staphylococcus aureus* exhibited smooth, rod-shaped and spherical cells. Bacterial cells treated with LQ-CDs showed wrinkling and collapse on their surface, and some cells exhibited cell wall damage. Bacterial cells stimulated with D / LQ-CDs showed even greater surface damage, with some cells even breaking and fragmenting completely. These results indicate that CDs can kill bacteria by disrupting their surface, and that D / LQ-CDs have a significantly better antibacterial effect than LQ-CDs.
[0065] (2) Biofilm Influence Test
[0066] Biofilm formation was determined using crystal violet staining. Biofilm measurement reflects the amount of bacteria formed after a period of stimulation by CDs.
[0067] Add 100 μL of bacterial suspension (1 × 10⁻⁶) to a 96-well plate. 7 Cells were incubated with 100 μL of different concentrations of CDs (0 mg / mL, 1.25 mg / mL, 2.5 mg / mL, 5 mg / mL, 10 mg / mL) at 37°C for 24 h to allow bacteria to adhere to the well walls of 96-well plates. After removing unattached cells, methanol solution was added and the plates were allowed to stand, followed by multiple washes with sterile PBS. After drying, crystal violet solution was added for staining for 15 min. After washing with PBS, 30% acetic acid solution was added, and the absorbance was measured at 570 nm after 30 min.
[0068] The test results are as follows Figure 8 As shown:
[0069] Depend on Figure 8It can be seen that, compared with the CK group and the LQ-CDs treatment group, less bacterial biofilm was generated after stimulation with D / LQ-CDs. This indicates that D / LQ-CDs can effectively inhibit bacterial biofilm formation, proving that D / LQ-CDs possess some of the properties of D-glutamate.
[0070] (3) Bacterial conductivity
[0071] Add 1 mL of CDs solution of different concentrations to 2 mL of bacterial culture (1×10⁻⁶). 7 The sample was incubated at 37°C with shaking for 6 hours in CFU / mL solution. After centrifugation at 2500 rpm for 5 minutes, 300 μL of the supernatant was collected into a centrifuge tube, and 4.7 mL of distilled water was added to determine the conductivity of the solution.
[0072] The test results are as follows Figure 9 As shown:
[0073] The conductivity of bacteria stimulated with different concentrations of CDs increased to varying degrees, indicating that CDs can affect the permeability of bacterial cell walls, thereby increasing their conductivity.
[0074] (4) Reactive oxygen species determination
[0075] The reactive oxygen species were determined using the DCFH-DA probe method.
[0076] Add 1 mL of CDs solution of different concentrations to 2 mL of bacterial culture (1×10⁻⁶). 7 Incubate at 37°C for 2 hours in (CFU / mL) solution.
[0077] Centrifuge at 2500 rpm for 5 min and collect bacteria. Wash the precipitate with sterile PBS and add 2×10⁻⁶ ppm of PBS. -5 The DCFH-DA probe was incubated at mol / L for 1 hour in the dark, followed by centrifugation to remove excess DCFH-DA. The sample was washed several times with PBS solution, and the fluorescence intensity was measured using a multi-functional microplate reader.
[0078] The test results are as follows Figure 10 As shown;
[0079] Bacteria treated with CDs for a period of time can produce reactive oxygen species, and D / LQ-CDs treatment can make bacteria produce even more reactive oxygen species, thereby inhibiting bacterial growth.
[0080] (5) Determination of total protein content
[0081] The purpose of determining the total protein leakage was to demonstrate whether CDs stimulating bacteria would cause cell wall damage. The total protein content was determined according to the method described in the Nanjing Jiancheng Total Protein Quantitative Assay Kit.
[0082] The test results are as follows Figure 11 As shown:
[0083] D / LQ-CDs can significantly disrupt bacterial cell walls, allowing more protein contents to flow out.
[0084] In summary, from a cellular perspective, CDs can disrupt bacterial cell walls, increase cell wall permeability, and even completely break down the cell wall, causing contents to leak out. Simultaneously, CDs that enter the bacterial interior can induce the production of reactive oxygen species, accelerating bacterial apoptosis.
[0085] 4. Study the antibacterial properties of CDs at the molecular level.
[0086] (1) Nucleic acid leakage measurement
[0087] The level of nucleic acid in cells can be represented by absorbance at a wavelength of 260 nm. The method for determining nucleic acid leakage is as follows: Centrifuge the activated bacterial culture to remove the supernatant, wash the resulting precipitate with sterile PBS solution, and resuspend it at a concentration of 1×10⁻⁶. 7 CFU / mL, different concentrations of CDs were added to the resuspended solution, and the solution was incubated at 37℃ with shaking for 4 h. The sample was centrifuged at 2500 r / min for 5 min, and the absorbance of the supernatant was measured at 260 nm.
[0088] The test results are as follows Figure 12 As shown:
[0089] Escherichia coli and Staphylococcus aureus treated with CDs exhibited varying degrees of nucleic acid leakage. This indicates that after CD stimulation, the DNA and RNA in the bacteria leaked out of the cells, and the higher the CD concentration, the greater the amount of nucleic acid leakage.
[0090] (2) ATPase activity assay
[0091] ATPase activity was determined according to the method of Nanjing Jiancheng Ultra-Micro Total ATPase Test Kit.
[0092] The test results are as follows Figure 13 As shown:
[0093] The ATPase activity of the two bacteria treated with CDs was significantly lower than that of the control group. This indicates that CDs can effectively reduce the ATPase activity of Escherichia coli and Staphylococcus aureus, thereby affecting the energy supply within the bacteria.
[0094] The present invention also provides other feasible implementation schemes, as follows:
[0095] Example 3
[0096] Preparation of D-glutamic acid-doped Forsythia carbon quantum dots:
[0097] Forsythia suspensa was ground into powder. 1.3 g of Forsythia suspensa powder, 0.2 g of D-glutamic acid, and 60 mL of ultrapure water were mixed thoroughly. The mixture was transferred to a hydrothermal reactor lined with 100 mL of polytetrafluoroethylene. The mixture was heated at 180 °C for 6 h. The resulting product was centrifuged at 10000 g for 30 min. After centrifugation, the supernatant was filtered through a 0.22 μm aqueous PES filter. The filtrate was collected and centrifuged at 3000 g for 20 min through a 10 kDa ultrafiltration centrifuge tube. The resulting filtrate was then freeze-dried under vacuum to obtain D-glutamic acid-doped Forsythia suspensa carbon quantum dot powder, i.e., D / LQ-CDs.
[0098] Example 4
[0099] Preparation of D-glutamic acid-doped Forsythia carbon quantum dots:
[0100] Forsythia suspensa was ground into powder. 1.5 g of Forsythia suspensa powder, 0.5 g of D-glutamic acid, and 60 mL of ultrapure water were mixed thoroughly. The mixture was transferred to a hydrothermal reactor lined with 100 mL of polytetrafluoroethylene. The mixture was heated at 200 °C for 8 h. The resulting product was centrifuged at 10000 g for 30 min. After centrifugation, the supernatant was filtered through a 0.22 μm aqueous PES filter. The filtrate was collected and centrifuged at 3500 g for 30 min through a 10 kDa ultrafiltration centrifuge tube. The resulting filtrate was then freeze-dried under vacuum to obtain D-glutamic acid-doped Forsythia suspensa carbon quantum dot powder, i.e., D / LQ-CDs.
[0101] Example 5
[0102] Preparation of D-glutamic acid-doped Forsythia carbon quantum dots:
[0103] Forsythia suspensa was ground into powder. 1.4 g of Forsythia suspensa powder, 0.4 g of D-glutamic acid, and 65 mL of ultrapure water were mixed thoroughly. The mixture was transferred to a hydrothermal reactor lined with 100 mL of polytetrafluoroethylene. The mixture was heated at 190 °C for 7 h. The resulting product was centrifuged at 11000 g for 40 min. After centrifugation, the supernatant was filtered through a 0.22 μm aqueous PES filter. The filtrate was collected and centrifuged at 3400 g for 25 min through a 10 kDa ultrafiltration centrifuge tube. The resulting filtrate was then freeze-dried under vacuum to obtain D-glutamic acid-doped Forsythia suspensa carbon quantum dot powder, i.e., D / LQ-CDs.
[0104] Example 6
[0105] Preparation of D-glutamic acid-doped Forsythia carbon quantum dots:
[0106] Forsythia suspensa was ground into powder. 1.35 g of Forsythia suspensa powder, 0.3 g of D-glutamic acid, and 60 mL of ultrapure water were mixed thoroughly. The mixture was transferred to a hydrothermal reactor lined with 100 mL of polytetrafluoroethylene. The mixture was heated at 180 °C for 6 h. The resulting product was centrifuged at 10000 g for 30 min. After centrifugation, the supernatant was filtered through a 0.22 μm aqueous PES filter. The filtrate was collected and centrifuged at 3200 g for 25 min through a 10 kDa ultrafiltration centrifuge tube. The resulting filtrate was then freeze-dried under vacuum to obtain D-glutamic acid-doped Forsythia suspensa carbon quantum dot powder, i.e., D / LQ-CDs.
[0107] Example 7
[0108] Preparation of D-glutamic acid-doped Forsythia carbon quantum dots:
[0109] Forsythia suspensa was ground into powder. 1.3 g of Forsythia suspensa powder, 0.5 g of D-glutamic acid, and 65 mL of ultrapure water were mixed thoroughly. The mixture was transferred to a hydrothermal reactor lined with 100 mL of polytetrafluoroethylene. The mixture was heated at 190 °C for 7 h. The resulting product was centrifuged at 11000 g for 40 min. After centrifugation, the supernatant was filtered through a 0.22 μm aqueous PES filter. The filtrate was collected and centrifuged at 3400 g for 25 min through a 10 kDa ultrafiltration centrifuge tube. The resulting filtrate was then freeze-dried under vacuum to obtain D-glutamic acid-doped Forsythia suspensa carbon quantum dot powder, i.e., D / LQ-CDs.
[0110] Example 8
[0111] Preparation of D-glutamic acid-doped Forsythia carbon quantum dots:
[0112] Forsythia suspensa was ground into powder. 1.25 g of Forsythia suspensa powder, 0.5 g of D-glutamic acid, and 60 mL of ultrapure water were mixed thoroughly. The mixture was transferred to a hydrothermal reactor lined with 100 mL of polytetrafluoroethylene. The mixture was heated at 200 °C for 8 h. The resulting product was centrifuged at 12000 g for 50 min. After centrifugation, the supernatant was filtered through a 0.22 μm aqueous PES filter. The filtrate was collected and centrifuged at 3500 g for 30 min through a 10 kDa ultrafiltration centrifuge tube. The resulting filtrate was then freeze-dried under vacuum to obtain D-glutamic acid-doped Forsythia suspensa carbon quantum dot powder, i.e., D / LQ-CDs.
[0113] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention in any other way. Any person skilled in the art may make changes or modifications to the above-disclosed technical content to create equivalent embodiments. However, any simple modifications, equivalent changes, and modifications made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the protection scope of the present invention.
Claims
1. A method for preparing D-glutamic acid-doped Forsythia carbon quantum dots, characterized in that, The steps are as follows: Forsythia powder and D-glutamic acid were added to water to carry out a hydrothermal reaction; the reaction solution was centrifuged, the supernatant was collected and filtered; the filtrate was dried to obtain D-glutamic acid-doped Forsythia carbon quantum dots. The mass fractions of each component are as follows: Forsythia powder 1.25~1.5 parts, D-glutamic acid 0.2~0.5 parts, water 60~66 parts; The conditions for the hydrothermal reaction are selected from: heating the reaction at 180~200℃ for 6~8 hours.
2. The preparation method according to claim 1, characterized in that, The mass fractions of each component are as follows: 1.25 parts of Forsythia powder, 0.2 parts of D-glutamic acid, and 60 parts of water.
3. Forsythia carbon quantum dots doped with D-glutamic acid prepared by the method of any one of claims 1 to 2.
4. The use of the D-glutamic acid-doped Forsythia carbon quantum dots of claim 3 in the preparation of agents or drugs that inhibit pathogenic bacteria.
5. The application according to claim 4, characterized in that, The pathogenic bacteria are Escherichia coli and / or Staphylococcus aureus.
6. An inhibitor of *Escherichia coli* and / or *Staphylococcus aureus*, characterized in that, The inhibitor contains forsythia carbon quantum dots doped with D-glutamic acid as described in claim 3.