CN113549448B

CN113549448B - Carbon dot with inherent antibacterial activity and photodynamic enhanced sterilization effect, and preparation method and application thereof

Info

Publication number: CN113549448B
Application number: CN202110775756.3A
Authority: CN
Inventors: 樊江莉; 刘卫俭; 杜健军; 孙文; 彭孝军
Original assignee: Dalian University of Technology; Ningbo Research Institute of Dalian University of Technology
Current assignee: Dalian University of Technology; Ningbo Research Institute of Dalian University of Technology
Priority date: 2021-07-08
Filing date: 2021-07-08
Publication date: 2022-06-07
Anticipated expiration: 2041-07-08
Also published as: CN113549448A

Abstract

The invention discloses a carbon dot with inherent antibacterial activity and photodynamic enhanced sterilization effect, and a preparation method and application thereof. The technical scheme is as follows: uniformly mixing the bactericide and the organic solvent to form a mixed reaction solution, heating the mixed reaction solution to 140-260 ℃, reacting for 30 min-24 h, cooling a reaction product, and purifying to obtain the carbon dots with red fluorescence emission. The preparation method of the carbon dots has the advantages of simple process, high efficiency, economy, safety and no toxicity, and the prepared carbon dots have inherent antibacterial performance and can realize photodynamic sterilization. In addition, the carbon dots can be used for cell and bacteria imaging, have good biocompatibility, low toxicity and broad-spectrum bactericidal performance, and can not generate the problems of bacterial drug resistance and the like. Therefore, the method has wide application prospect in the fields of future cell imaging, solving the problem of bacterial drug resistance and the like.

Description

Carbon dot with inherent antibacterial activity and photodynamic enhanced sterilization effect, and preparation method and application thereof

Technical Field

The invention belongs to the technical field of fluorescent and antibacterial carbon nano materials, and particularly relates to a carbon dot with intrinsic antibacterial activity and photodynamic-enhanced sterilization effect, and a preparation method and application thereof.

Background

Bacterial infections are acute systemic infections produced by invasion of the blood circulation by pathogenic or conditional pathogens to produce toxins and other metabolites. Many diseases occur in association with bacterial infections, such as tetanus, chimpanzee fever, typhoid fever, brucellosis, bacillary dysentery, tuberculosis and bacterial pneumonia. Over the past decades, antibiotic therapy has been one of the major methods of treating bacterial infections since the discovery of penicillin. However, the long-term and overuse of antibiotics may lead to the emergence of multi-drug resistant bacteria, which is an increasing threat to global public health. In addition, most bacterial infections are associated with biofilms, and the biofilms attached to the surfaces of bacteria can not only protect the bacteria from being interfered by external environment, but also have strong drug resistance to host immune defense and prevent penetration of antibiotics, which is 100-1000 times stronger than that of planktonic bacteria to antibiotics, so that the bacterial infections are difficult to treat and seriously disturb human health. Therefore, there is an urgent need to develop new antibacterial strategies to combat multidrug resistant bacterial infections and eliminate the biofilm that forms.

The rapid development of nanotechnology provides new opportunities for solving the problem of bacterial drug resistance. Some nanomaterials, including silver nanoparticles, semiconductor nanoparticles, antimicrobial polypeptides, graphene oxide, noble metal nanoparticles, etc., have been shown to inhibit bacterial infection or eliminate biofilms by different mechanisms. Their disadvantages, such as complex synthesis, poor permeability to biological membranes, instability, and poor biocompatibility, have still hindered their practical use. Although carbon dots can effectively kill bacteria, most of the carbon dots have strong absorption in the ultraviolet region, and fluorescence emission is also mostly located in the blue or green region, and few of the carbon dots have red fluorescence emission. Moreover, few carbon dots have been reported which have both intrinsic antibacterial activity and photodynamic properties. Therefore, it is still a challenge to find a new strategy to improve the antibacterial performance of fluorescent carbon nanomaterials.

Disclosure of Invention

Aiming at the problems of the existing antibacterial material, the invention provides a long-wavelength emission carbon dot, a preparation method of a fluorescent carbon dot with intrinsic antibacterial activity and application thereof. The bactericide and the synthetic bactericide intermediate are used as carbon sources, the synthesized carbon points have internal antibacterial activity, when the carbon points act on bacteria, cell walls for protecting the activity of the bacteria can be damaged, the permeability of the bacteria is changed, and meanwhile, the carbon points penetrate into cells to interfere the metabolism of the bacteria so as to kill the bacteria, in addition, under the irradiation of 590nm light, the carbon points can also generate singlet oxygen to further damage DNA of the bacteria and lipid peroxidation to damage cell membranes, so that protein in the bacteria is leaked, and the bacteria completely lose the activity; the problems are solved: 1. the drug resistance problem occurring in the process of treating bacterial infection; 2. the traditional composite nano material has the problems of complex synthesis and expensive raw material cost. 3. The biological membrane has strong permeability; 4. the stability and the biocompatibility are good; 5. has a red fluorescent emission; 6. has intrinsic antibacterial activity and photodynamic properties.

The purpose of the invention can be realized by the following technical scheme:

a method for preparing carbon dots with intrinsic antibacterial activity and photodynamic-enhanced bactericidal effect comprises the following steps:

dissolving a carbon precursor in an organic solvent, and uniformly mixing to form a mixed reaction solution; and reacting the mixed solution at the temperature of 140-260 ℃ and maintaining for a period of time to obtain a dark red solution, and performing post-treatment to obtain the carbon dots with the intrinsic antibacterial activity and the photodynamic synergistic sterilization.

Furthermore, the molar mass ratio of the bactericide to the bactericide raw materials is 1: 1-10.

Further, the mixed solution contains 0.5-20 wt% of carbon precursor raw material.

Further, the bactericide is at least one selected from the group consisting of 2, 4-dihydroxybenzoic acid, 6-bromo-2-naphthol, methyl-benzimidazole-2-carbamate, 2-allylphenol, and 2- (4-thiazolyl) -1H-benzimidazole, but is not limited thereto.

Further, the organic solution is at least one of N, N-dimethylformamide, formamide, absolute ethanol and methanol, but is not limited thereto.

Further, the preparation method also comprises the following steps: when the reaction temperature is higher or lower than the boiling point of the organic solvent, the mixed reaction liquid is put into a pressurized reaction vessel for full reaction.

Preferably, the preparation method further comprises: the reaction temperature of the mixed solution is 140-260 ℃, the reaction time is 30 min-24 h, and a primary product is obtained after cooling; preferably, the reaction is carried out for 4-16h at the temperature of 160-200 ℃.

Preferably, the post-treatment comprises removing the reaction solvent from the primary product and purifying.

Preferably, the reaction solvent is removed by at least one method selected from the group consisting of rotary evaporation, spray drying, vacuum drying and freeze drying.

Preferably, the purification comprises rapid preparative liquid chromatograph and/or column chromatographic separation; and the eluent for purification is methanol and dichloromethane in a volume ratio of 1: 10-1000.

For example, in a more specific embodiment, the method of preparation comprises the following:

dissolving a carbon precursor in an organic solvent to prepare a mixed reaction solution with a certain concentration;

heating the mixed reaction solution to a certain temperature and reacting at the temperature for a period of time to obtain a clear solution, wherein the clear solution is a dark red solution; in the comparative example, when only one of the carbon sources was used, the color was pale yellow, and therefore, the reaction end point was clearly distinguishable by color judgment.

And (4) centrifuging, filtering or separating by column chromatography to obtain the carbon dots with the antibacterial activity and the photodynamic synergistic sterilization.

In another aspect of the present invention, carbon dots having intrinsic antibacterial activity and photodynamic-enhanced bactericidal effect obtained by the above-described preparation method are disclosed.

The third aspect of the invention is the application of the antibacterial carbon dots, and particularly comprises the application of the antibacterial carbon dots in multi-drug resistant bacterial treatment products or imaging of microorganisms and cells.

Compared with the prior art, the invention has the following characteristics and beneficial effects:

(1) the long-wave long-emitting carbon dots with inherent antibacterial activity and photodynamic-enhanced sterilization effect, prepared by the method, are simple in preparation method and easy to control.

(2) The carbon dots prepared by the method have the advantages of independence of excitation wavelength, excellent optical performance, good biocompatibility and great advantages in the field of biological imaging.

(3) The carbon dots prepared by the invention have the inherent antibacterial performance, do not generate the problem of bacterial drug resistance, and can generate singlet oxygen under the excitation of long wavelength to improve the antibacterial efficiency.

(4) The carbon dots prepared by the method have broad-spectrum antibacterial performance, and not only have bactericidal effect on gram-positive bacteria, but also have good bactericidal performance on gram-negative bacteria.

Drawings

FIG. 1 is a high resolution TEM image of carbon dots of example 1 of the present invention, in which FIG. 1a shows that the carbon dots have a spheroidal shape and a distinct lattice stripe structure with a lattice spacing of 0.21nm, and FIG. 1b shows a histogram of particle size distribution with a particle size of about 3.92 nm.

FIG. 2 is a carbon point XRD spectrum of example 1 of the present invention at 21.24^°It shows a broad diffraction peak (2 θ), which is consistent with the (001) lattice spacing of the graphitic carbon-based material, indicating that the carbon source is partially carbonized into carbon dots.

FIG. 3 is a graph of the UV-Vis spectrum of the carbon spot of example 1 of the present invention, which shows that the carbon spot has a broad absorption at 350-700 nm.

FIG. 4 is a fluorescence spectrum of the carbon dot of example 1 of the present invention at different excitation wavelengths, showing that the carbon dot has the characteristic of independent excitation wavelengths.

FIG. 5 is a graph showing fluorescence spectra of carbon dots of comparative examples 1 and 2 of the present invention at different excitation wavelengths, showing that the carbon dots have excitation wavelength dependence, i.e., the emission peak positions change with the change in the excitation wavelength.

FIG. 6 is a graph showing the fluorescence spectra of the carbon dot of comparative example 3 of the present invention at different excitation wavelengths, showing that the carbon dot has excitation wavelength dependence, i.e., the emission peak position changes with the change in the excitation wavelength.

FIG. 7 is the image of the carbon dot and COS-7 cell of example 1, which is obtained by confocal laser microscopy, and it can be seen from FIG. 7a that the cell exhibits red fluorescence at 561nm, indicating that the carbon dot can be used for imaging. FIG. 7b shows the dark toxicity and phototoxicity of carbon dots to cells by MTT assay, measurement of absorbance at 570nm and 630nm, calculation of cell viability, and characterization of the magnitude of carbon dot cytotoxicity in terms of cell viability.

FIG. 8 is a graph a and a graph b showing the number of colonies after coculture of carbon dots of different concentrations with Acinetobacter baumannii and Staphylococcus aureus in example 1 of the present invention and 590nm illumination, and shows that the number of surviving bacteria decreases with the increase of the carbon dot concentration, indicating that the antibacterial effect is better.

FIG. 9 is a scanning electron microscope image of carbon dots of example 1 of the present invention after co-culture with Acinetobacter baumannii and Staphylococcus aureus and illumination at 590nm, from which it can be seen that, compared with the blank control, the carbon dots have intrinsic antibacterial activity and are destructive to the surface of bacteria, and in addition, after illumination, the destruction of cavities on the surface of bacteria is significantly increased, which indicates that singlet oxygen generated by illumination has a certain synergistic effect on sterilization.

Fig. 10 is a treatment diagram of the carbon dots to the mouse wound drug-resistant acinetobacter baumannii infection in example 1 of the present invention, fig. 10a and c show that the effect of the carbon dots and the carbon dot plus light treatment group is significantly higher than that of the blank control group, fig. 10b shows that the number of colonies remained at the wound after 9 days of treatment indicates that the carbon dots can effectively kill the bacteria at the wound to achieve the purpose of treatment, fig. 10d shows that the body weight of the mouse changes during the treatment period, and it can be seen that the body weight range is not large, further showing that the carbon dots have good biocompatibility.

Detailed Description

The following examples are included to further illustrate specific embodiments of the present invention and to provide a better understanding of the invention. The examples are given solely for the purpose of illustration and are not intended to limit the scope of the invention. The above description is only for the preferred embodiment of the present invention, but the scope of the present invention is not limited thereto, and those skilled in the art can easily conceive of the changes or substitutions within the technical scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the protection scope of the claims. The materials and reagents used in the following examples are commercially available unless otherwise specified.

Example 1

Step 1, dissolving 2, 4-dihydroxy benzoic acid and 6-bromo-2-naphthol in methanol to prepare a solution with the mass fraction of 0.5%.

And 2, putting 10mL of the solution into a 50mL high-temperature high-pressure reaction kettle, putting the reaction kettle into an oven, reacting at 180 ℃ for 30min, 4h, 8h, 12h and 24h respectively, cooling the reaction kettle to room temperature, and taking out.

And 3, centrifuging the reaction solution, filtering to obtain a clear dark red solution, and finally obtaining dark red solid powder, namely the target product, which is placed in a vacuum drying oven for drying and then is sealed for storage.

And 4, characterizing the carbon dots in the embodiment, wherein a high-resolution transmission electron microscope image of the carbon dots prepared in the embodiment is shown as 1, and the image shows that the average particle size of the carbon dots is 3.32nm +/-0.96 nm. The absolute fluorescence quantum yields were determined to be 0.5%, 3.1%, 23.5%, 17.3% and 10.2%, respectively.

The XRD pattern of the carbon dots prepared in this example is shown in fig. 2, which shows a broad diffraction peak (2 θ) at 21.24 °, which is consistent with the (001) lattice spacing of the graphitic carbon-based material, indicating that the precursor is partially carbonized into carbon dots. The UV-Vis spectrum of the carbon dots prepared in this example is shown in FIG. 3, which shows that the carbon dots have wide absorption at 350-700 nm. The fluorescence spectra of the carbon dots prepared in this example at different excitation wavelengths are shown in fig. 4, which shows that the carbon dots have the characteristic of independent excitation wavelengths.

Example 2

Step 1, dissolving 2, 4-dihydroxy benzoic acid and 6-bromo-2-naphthol in methanol to prepare a solution with the mass fraction of 2%.

And 2, putting 10mL of the solution into a 50mL high-temperature high-pressure reaction kettle, putting the reaction kettle into an oven, reacting for 4h, 8h, 12h and 24h at 160 ℃, cooling the reaction kettle to room temperature, and taking out.

And 3, centrifuging, filtering to obtain a clear solution, judging by the color of the solution, wherein the color of the solution is light yellow in 4h and 8h, the maximum fluorescence emission peak is 540nm, the color of the solution is yellow in 12h and 24h, the maximum emission peak is 600nm, and the fluorescence quantum yield is measured to be 1.2% and 2.2% respectively.

Example 3

Step 1, dissolving 2, 4-dihydroxy benzoic acid and 6-bromo-2-naphthol in methanol to prepare a solution with the mass fraction of 5%.

And 2, putting 10mL of the solution into a 50mL high-temperature high-pressure reaction kettle, putting the reaction kettle into an oven, reacting for 4 hours and 8 hours at 220 ℃, respectively, cooling the reaction kettle to room temperature after 10 hours, and taking out.

And 3, centrifuging and filtering to obtain a clear dark red solution, and finally obtaining dark red solid powder, namely the target product, which is placed in a vacuum drying oven for drying and then is sealed for storage.

And 4, respectively measuring the absolute fluorescence quantum yield of the fluorescent material to be 1.7%, 2.4% and 1.3%.

Example 4

The carbon dots prepared in example 1 were used to label COS-7 cells, as shown in FIG. 7a, and the carbon dots were allowed to enter the cells for cell imaging.

The specific implementation process comprises the following steps: the carbon dot powder of example 1 was taken to prepare a carbon dot solution having a concentration of 10mg/mL, the carbon dot concentration was diluted with a DMEM medium to 150. mu.g/mL, and the solution was sterilized in a clean bench for 30 min. And (3) taking COS-7 cells with good growth state, discarding the original cell culture solution, slightly washing twice with PBS, finally adding a carbon dot solution diluted with DMEM, and culturing in a carbon dioxide incubator at 37 ℃ for 0-45 min. Then, the carbon spot culture solution was discarded, washed with PBS buffer solution 3 times, and then 2mL of DMEM solution was added, and the state of cell fluorescence was observed under excitation at 561nm using a laser confocal microscope, and photographed and recorded.

The image of the carbon dot labeled COS-7 cells of this example is shown in FIG. 7a, which shows that the cells exhibit red fluorescence at an excitation wavelength of 561 nm. This indicates that the carbon dots have good biocompatibility and thus can be used for fluorescence imaging.

Example 5

Cytotoxicity of the carbon dots prepared in example 1 was confirmed by using MTT method.

The method comprises the following operation steps: COS-7 cells were digested and prepared to a concentration of 5X 10³The cell suspension was added to a 96-well plate at 37 ℃ in an amount of 100. mu.L/well, and 5% CO₂After culturing to 80% density under the environment, 100 μ L of carbon dot DMEM solution with different gradient concentrations is added, and then corresponding dose of illumination is given according to the experiment requirements. And (3) continuing culturing at 37 ℃ for 12h, adding 20 mu L of MTT solution (5mg/mL PBS aqueous solution) into each hole, incubating for 4h, discarding the culture solution, adding 200 mu L of DMSO into each hole, putting the hole into an enzyme-linked immunosorbent assay, shaking for 5min, detecting the absorbance values at 590nm and 630nm, and further calculating the cell survival rate.

The MTT test results of carbon dot to cytotoxicity of this example are shown in fig. 7b, which shows that the cell survival rate is above 85% in the absence of light when different concentrations of carbon dot solutions are added compared with the blank group, and still exceeds 75% after light irradiation, indicating that the prepared carbon dots have excellent biocompatibility.

Example 6

The carbon dots prepared in example 1 were used to kill multidrug-resistant acinetobacter baumannii and staphylococcus aureus, and the survival rate of the bacteria was recorded by standard plate counting.

Single colonies (multidrug-resistant A. baumannii or S.aureus) were transferred to Erlenmeyer flasks (250mL) containing 20mL of liquid medium and then placed on a 37 ℃ constant temperature shaker and shaken well overnight at 150 rpm. Freshly grown bacteria were centrifuged at 5000rpm for 5min, washed twice with sterile phosphate buffer (PBS, pH7.4, 0.01mmol), and then diluted to 10 with PBS⁶CFU mL^-1. Then with carbon dots (0, 10, 20, 30, 40, 50 or 100. mu.gmL)^-1) Culturing in dark for 0-45 min, or irradiating with light (590nm, 30 mWcm)^-215 minutes) for further processing. Finally, the bacteria were plated on solid agar plates using standard plate plating, incubated in a constant temperature incubator (37 ℃) for 24 hours, and then the number of colonies was counted. Controls were treated with PBS/Light and cultured under the same conditions. Five replicates were made for each concentration.

The effect of the carbon dots on killing the multidrug-resistant acinetobacter baumannii and staphylococcus aureus is shown in fig. 8, along with the increase of the concentration of the carbon dots, compared with a blank control group, the total number of colonies in an experimental group is obviously reduced, which indicates that the prepared carbon dots have internal antibacterial performance, and under the condition of illumination, the total number of surviving bacteria is obviously reduced, which indicates that the illumination generates singlet oxygen, so that the bacteria are further killed in a synergistic manner.

Example 7

The carbon point influence on the bacterial morphology prepared in example 1 is specifically implemented as follows, after the bacteria are subjected to different treatments, the bacterial suspension is centrifuged, the culture medium is washed away, then the bacterial morphology is changed by 2.5% glutaraldehyde solid, the bacteria are placed in a refrigerator at 4 ℃ for fixing for 4h, and then the bacteria are dehydrated for 15min once by 20, 40, 60, 80, 90 and 100% ethanol. Finally, the bacterial suspension is dropped on a copper net, after air drying, the sample is finally sprayed with platinum and observed by a scanning electron microscope.

The influence of the carbon dots on the morphology of the bacteria is shown in fig. 9, and compared with the blank control group (PBS, Light), the bacteria surface of the experimental group has many holes (arrows), and after Light irradiation, the bacteria surface is obviously collapsed, which indicates that the prepared carbon dots not only have the inherent antibacterial property, but also have the photodynamic synergistic bactericidal effect.

Example 8

The carbon dots prepared in example 1 are used for treating mouse bacterial infection wounds, and the specific implementation process is as follows: 30 female Balb/c mice, 6-8 weeks old, were randomly assigned to 5 groups: PBS group, Light group, carbon dot + Light group, Polymyxin B group. After injecting Acinetobacter baumannii suspension to the left side of the back of the mouse, a white infected area can be seen after 24 hours, and the success of infection is proved. The drug is respectively applied to the infected part. After 12h, 590nm light, 30mW/cm was used²The infected part is irradiated for 15 min. The body weight and wound area of the mice were then measured every 3 days and photographed to record the healing of the infected area.

Treatment of mice with carbon-point resistant A.baumannii infection in mice wounds is shown in FIG. 10a, where scab began on day 3 in groups (III) and (IV) and scab began on day 7 in groups (I, II, V), indicating that the wound healing rates in groups (III) and (IV) were faster than those in negative control group (I, II) and positive control group (V). In addition, wound healing was not optimistic for the negative and positive controls.

Comparative example 1

By adopting the preparation method of the embodiment 1, the carbon source precursor in the step 1 is adjusted to be 2, 4-dihydroxybenzoic acid and 2-allylphenol, the ratio of the two is 1:1, and the solution with the mass fraction of 0.5% is prepared.

Step 2 is the same as in example 1.

And 3, centrifuging and filtering to obtain a clear solution, wherein the color of the clear solution is light yellow, the maximum emission peak position of the clear solution is 450nm +/-10 nm, and the fluorescence quantum yield of the clear solution is 0.5%, 1.5%, 2.6%, 3.1% and 1.4% respectively. Its absorption lies in the ultraviolet region and its emission lies in the blue region.

Comparative example 2

By adopting the preparation method of the embodiment 1, the carbon source precursor in the step 1 is adjusted to be 6-bromo-2-naphthol, and a solution with the mass fraction of 0.5% is prepared.

Step 2 is the same as in example 1.

And 3, centrifuging and filtering to obtain a clear solution, wherein the color of the clear solution is light yellow, the maximum emission peak position of the clear solution is 450nm +/-10 nm, and the fluorescence quantum yield of the clear solution is 0.7%, 2.5%, 3.5%, 4.6% and 1.8% respectively. Its absorption lies in the ultraviolet region and its emission lies in the blue region. The luminescence spectrum is shown in FIG. 5. It is shown that the carbon dots have excitation wavelength dependence, i.e., as the excitation wavelength is changed, the emission peak position is changed.

Comparative example 3

By adopting the preparation method of the embodiment 1, the carbon source precursor in the step 1 is adjusted to be 2, 4-dihydroxybenzoic acid, and a solution with the mass fraction of 0.5% is prepared.

Step 2 is the same as in example 1.

And 3, centrifuging and filtering to obtain a clear solution, wherein the color of the clear solution is light yellow, the maximum emission peak position of the clear solution is within +/-10 nm of 380nm, and the fluorescence quantum yield of the clear solution is respectively 0.5%, 1.5%, 2.6%, 3.1% and 1.4%. Its absorption lies in the ultraviolet region and its emission lies in the blue region. The luminescence spectrum is shown in FIG. 6. It is shown that the carbon dots have excitation wavelength dependence, i.e., as the excitation wavelength is changed, the emission peak position is changed.

The above-mentioned embodiments are merely preferred embodiments for fully illustrating the present invention, and the scope of the present invention is not limited thereto. The equivalent substitution or the change made by the technical personnel in the technical field on the basis of the invention are all within the protection scope of the invention. The protection scope of the invention is subject to the claims.

Claims

1. A preparation method of carbon dots with inherent antibacterial activity and photodynamic reinforced bactericidal action is characterized in that: uniformly mixing 2, 4-dihydroxybenzoic acid and 6-bromo-2-naphthol serving as carbon precursor raw materials in a molar ratio of 1: 1-10 in an organic solvent to form a mixed solution, wherein the mixed solution contains 0.5-20 wt% of the carbon precursor raw materials; and heating the mixed solution to 140-260 ℃, maintaining for a period of time to obtain a dark red solution, and performing post-treatment to obtain carbon dots with intrinsic antibacterial activity and photodynamic synergetic sterilization.

2. The method of claim 1, wherein: the organic solvent is at least one selected from N, N-dimethylformamide, formamide, absolute ethyl alcohol and methanol.

3. The method of claim 1, wherein: and pressurizing and heating the mixed solution, wherein the reaction temperature is 140-260 ℃, the reaction time is 30 min-24 hours, and cooling to obtain a primary product.

4. The production method according to claim 3, characterized in that: the reaction temperature is 160-200 ℃, and the reaction time is 4-16 hours.

5. The method of claim 1, wherein: the post-treatment comprises removing the reaction solvent from the primary product and purifying.

6. The method of claim 5, wherein: the method for removing the reaction solvent is at least one selected from rotary evaporation, vacuum drying and freeze drying.

7. The method of claim 5, wherein: the purification comprises rapid preparative liquid chromatograph and/or column chromatography separation; the eluent for purification is methanol and dichloromethane according to the volume ratio of 1: 10-1000.

8. The carbon dots obtained by the preparation method of claim 1, which have intrinsic antibacterial activity and photodynamic co-sterilization.

9. The use of an antimicrobial carbon dot according to any one of claims 1 to 8, wherein: the use of the antibacterial carbon dots in multi-drug resistant bacterial therapy products or in imaging of microorganisms and cells.