Preparation method, product and application of C / ZnO / polydopamine composite material

Abstract

The invention relates to the technical field of drug carrier preparation, in particular to a preparation method, a product and application of a C / ZnO / polydopamine composite material. The preparation method comprises the following steps: step 1, uniformly dispersing zinc salt and a carbon source in an organic solvent for solvothermal reaction to obtain C / ZnO; and step 2, dispersing the C / ZnO in water, then adding polydopamine, uniformly mixing, and reacting under an alkaline condition to obtain the C / ZnO / polydopamine composite material. According to the invention, C / ZnO is used as a matrix material, and the C / ZnO / polydopamine composite material is constructed under an alkaline condition through an oxidation auto-polymerization method. The C / ZnO / polydopamine composite material can realize efficient loading of a drug (5-fluorouracil), has a remarkable controlled release effect on the drug, and shows a good antibacterial effect.

Description

Technical Field

[0001] The present invention relates to the technical field of drug carrier preparation, and particularly to a preparation method, product and application of a C / ZnO / polydopamine composite material. Background Art

[0002] The progress of nanotechnology has greatly promoted the development of nanomedicine. Modern nanotechnology provides the possibility for targeted delivery of anticancer drugs to tumor sites, thereby minimizing toxicity and optimizing the efficacy of drugs. Over the years, many drug delivery carriers for anticancer drug delivery have been developed, such as polymer nanoparticles, solid lipids and inorganic nanoparticles. Therefore, significant progress has been made in this field, especially the polymer-based anticancer drug delivery system. Polymer micro-nano materials are biodegradable and have low toxicity, and the composition and structure of polymers can be designed to manipulate their drug delivery characteristics. However, the drug loading rate and controlled release effect of current drug carriers still need to be further improved. Summary of the Invention

[0003] Based on the above, the present invention provides a preparation method, product and application of a C / ZnO / polydopamine composite material.

[0004] To achieve the above object, the present invention provides the following solutions:

[0005] One of the technical solutions of the present invention is a preparation method of a C / ZnO / polydopamine composite material, comprising the following steps:

[0006] Step 1, uniformly dispersing a zinc salt and a carbon source in an organic solvent for a solvothermal reaction to obtain C / ZnO;

[0007] Step 2, dispersing the C / ZnO in water, then adding polydopamine (PDA) and mixing evenly, and reacting under alkaline conditions to obtain a C / ZnO / polydopamine composite material.

[0008] In a preferred embodiment of the present invention, in Step 1, the zinc source is zinc acetate; the carbon source is glucose; the ratio of the zinc source to the carbon source is (2.0 - 2.4) mmol∶(0.18 - 0.22) g.

[0009] In a preferred embodiment of the present invention, in Step 1, the organic solvent is ethylene glycol.

[0010] In a preferred embodiment of the present invention, in Step 1, the pH of the solvothermal reaction is 10.1; the temperature of the solvothermal reaction is 160 °C, and the time is 24 h.

[0011] In Step 1, after the solvothermal reaction, it further includes centrifugation, washing the centrifuged solid, and drying at 60 °C for 6 h.

[0012] In a preferred embodiment of the present invention, in step 2, the mass ratio of C / ZnO to polydopamine is (0.90 - 1.1)∶(0.27 - 0.33).

[0013] In a preferred embodiment of the present invention, in step 2, the mass - to - volume ratio of C / ZnO to water is (9.0 - 11 mg)∶(2.7 - 3.3 mL).

[0014] In the present invention, the amount of water directly affects the concentration of the reaction system, and further affects the polymerization behavior of dopamine, the morphology and properties of the composite material; therefore, the present invention preferably limits the mass - to - volume ratio of C / ZnO to water to the above ratio.

[0015] In a preferred embodiment of the present invention, the pH of the reaction is 8.5; the temperature of the reaction is room temperature; the time of the reaction is 3 h.

[0016] In some specific embodiments of the present invention, the pH of the reaction system is adjusted to be alkaline by adding sodium hydroxide solution.

[0017] In step 2, after the reaction, it further includes centrifugation, washing the centrifuged solid, and drying it at 80 °C for 12 h.

[0018] The second technical solution of the present invention is a C / ZnO / polydopamine composite material prepared by using the above - mentioned preparation method.

[0019] The third technical solution of the present invention is the application of the above - mentioned C / ZnO / polydopamine composite material in the preparation of sustained - release drugs.

[0020] The fourth technical solution of the present invention is a sustained - release drug prepared by dissolving the C / ZnO / polydopamine composite material and 5 - fluorouracil (5 - FU) in water and stirring under light - avoiding conditions.

[0021] In a preferred embodiment of the present invention, the mass ratio of the C / ZnO / polydopamine composite material to the 5 - fluorouracil is (0.25 - 2)∶1; the stirring time is 12 - 48 h.

[0022] The present invention discloses the following technical effects:

[0023] The present invention uses C / ZnO as the matrix material, and constructs a C / ZnO / polydopamine composite material by oxidative self - polymerization under alkaline conditions. The preparation method is simple. The C / ZnO / polydopamine composite material can achieve efficient loading of drugs (5 - fluorouracil), has a significant controlled - release effect on drugs, and shows good antibacterial effects. Brief Description of the Drawings

[0024] Figure 1 Infrared spectrum of C / ZnO prepared in Example 1.

[0025] Figure 2 XRD pattern of C / ZnO prepared in Example 1.

[0026] Figure 3 SEM images of C / ZnO prepared in Example 1 at different magnifications; where a) 1.6k, b) 10k, c) 20k, d) 30k.

[0027] Figure 4 EDS spectrum of C / ZnO prepared in Example 1; where a) Zn-K, b) O-K, c) C-K, d) total distribution spectrum.

[0028] Figure 5 TG-DTA curves of C / ZnO prepared in Example 1 in air atmosphere.

[0029] Figure 6 XPS spectrum of C / ZnO prepared in Example 1; where a) full XPS spectrum of C / ZnO, b) high-resolution Zn 2p spectrum of C / ZnO, c) high-resolution C1s spectrum of C / ZnO, d) high-resolution O1s spectrum of C / ZnO.

[0030] Figure 7 BET test results of C / ZnO prepared in Example 1; where a) N2 adsorption-desorption isotherm, b) pore size distribution diagram.

[0031] Figure 8 Particle size and Zeta potential results of C / ZnO prepared in Example 1; where a) particle size distribution diagram of C / ZnO, b) Zeta potential of C / ZnO, 5-FU, and C / ZnO / 5-FU (error bars represent the standard deviation of three independent measurements).

[0032] Figure 9 Drug release curve of C / ZnO prepared in Example 1.

[0033] Figure 10 MIC results of C / ZnO / 5-FU (concentrations decrease from left to right); where a1, a2 Staphylococcus aureus, b1, b2 Escherichia coli (note: the 11th well in b1, b2 is the positive control).

[0034] Figure 11MBC results of C / ZnO / 5-FU; among them, a, d) colony growth diagrams of drug treatment at 0 μg / mL, b) colony growth diagrams of drug treatment at 37.5 μg / mL, c) colony growth diagrams of drug treatment at 75 μg / mL, e) colony growth diagrams of drug treatment at 55 μg / mL, f) colony growth diagrams of drug treatment at 110 μg / mL.

[0035] Figure 12 Hemolytic activity evaluation of C / ZnO prepared in Example 1.

[0036] Figure 13 Infrared spectrum diagram of C / ZnO / polydopamine composite material (abbreviation: C / ZnO / PDA) prepared in Example 2.

[0037] Figure 14 XRD spectrum diagram of C / ZnO / PDA prepared in Example 2.

[0038] Figure 15 SEM diagrams of C / ZnO / PDA prepared in Example 2 at different magnification; among them, a) 5k, b) 10k, c) 20k, d) 30k.

[0039] Figure 16 EDS energy spectrum diagram of C / ZnO / PDA prepared in Example 2; among them, a) Zn-K, b) O-K, c) C-K, d) N-K, e) total distribution spectrum diagram.

[0040] Figure 17 TGA results of C / ZnO / PDA prepared in Example 2.

[0041] Figure 18 XPS full scan spectrum of C / ZnO / PDA prepared in Example 2.

[0042] Figure 19 a) High-resolution Zn 2p spectrum, b) high-resolution C1s spectrum, c) high-resolution O1s spectrum, d) high-resolution N1s spectrum of C / ZnO / PDA prepared in Example 2.

[0043] Figure 20 BET test result diagram of C / ZnO / PDA prepared in Example 2; among them, a) N2 adsorption-desorption isotherm, b) pore size distribution diagram.

[0044] Figure 21Particle size and Zeta potential results of C / ZnO / PDA prepared in Example 2; where, a) Particle size distribution diagram of C / ZnO / PDA, b) Zeta potential of C / ZnO, C / ZnO / PDA, 5-FU and C / ZnO / PDA / 5-FU (error bars represent standard deviation of three independent measurements).

[0045] Figure 22 Drug release profiles of drugs loaded using C / ZnO and C / ZnO / PDA as carriers.

[0046] Figure 23 MIC results of C / ZnO / PDA / 5-FU (concentrations decrease from left to right); where, a1, a2 Staphylococcus aureus, b1, b2 Escherichia coli.

[0047] Figure 24 MBC experimental results of C / ZnO / PDA / 5-FU; where, a, d) Colony growth diagrams of colonies treated with 0 μg / mL drug, b) Colony growth diagrams of colonies treated with 20 μg / mL drug, c) Colony growth diagrams of colonies treated with 40 μg / mL drug, e) Colony growth diagrams of colonies treated with 40.63 μg / mL drug, f) Colony growth diagrams of colonies treated with 81.26 μg / mL drug.

[0048] Figure 25 Hemolytic activity evaluation results of C / ZnO / PDA prepared in Example 2. Detailed implementation mode

[0049] Now, various exemplary embodiments of the present invention will be described in detail. This detailed description should not be considered as a limitation of the present invention, but should be understood as a more detailed description of certain aspects, characteristics and implementation schemes of the present invention.

[0050] "Room temperature" as described in the present invention, unless otherwise specified, all represents 20 - 30 °C.

[0051] The test methods involved in the present invention are as follows:

[0052] 1. Fourier transform infrared spectroscopy (FT-IR): The instrument model used in the present invention is Spectrum 3, produced by Perkin Elmer, USA. During the test, potassium bromide (KBr) is used as the background sample, and the test sample is prepared by the KBr tablet pressing method.

[0053] 2. Scanning electron microscope (SEM): A ZEISS GeminiSEM 300 type scanning electron microscope produced by Carl Zeiss, Germany is used. In addition, in order to further analyze the elemental composition of the material, the present invention combines an energy dispersive spectrometer to perform qualitative and quantitative elemental analysis on the sample surface.

[0054] 3. X-ray diffraction (XRD): It was measured using an X-ray diffractometer of model Bruker D8 Advance produced by Bruker Corporation in Germany. The diffraction target was Cu·k α , with a wavelength (λ) of 1.54060 nm, a measurement range of 2θ from 10° to 80°, and a continuous scanning rate of 10°·min -1 .

[0055] 4. Thermogravimetric analyzer (TGA): It was measured using a thermogravimetric analyzer of model HITACHI STA200 produced by Hitachi, Ltd. in Japan. Except for the C / ZnO sample which was tested in an air atmosphere, the remaining samples were tested in a nitrogen atmosphere. During the test, a constant heating rate of 10℃·min -1 was set, and the test temperature range was from 30℃ to 800℃.

[0056] 5. X-ray photoelectron spectroscopy (XPS): The instrument model used was Thermo Scientific K-Alpha, produced by Thermo Fisher Scientific in the United States, and the Kα line of Al was used as the X-ray source.

[0057] 6. Specific surface area and pore size determination (BET): The BET test of the material was carried out using an auto IQ type specific surface area and porosity analyzer. Before the test started, the sample to be measured needed to be degassed for 12 h to remove the adsorbed gas and moisture in the sample.

[0058] 7. Particle size and Zeta potential analysis (DLS): The instrument model used was Zetasizer Lab, produced by Malvern Instruments Limited in the UK. The sample cell model for measuring the Zeta potential was Malvern DTS1070, and the sample cell model for measuring the particle size was DTS0012.

[0059] 8. Drug loading and encapsulation efficiency test

[0060] 5-FU is a good drug for cancer treatment. In this invention, 5-FU is selected to study the encapsulation and loading effects of C / ZnO and C / ZnO / polydopamine composites as carrier materials on the drug. The specific process is as follows: Dissolve 10 mg of the carrier material in 15 ml of deionized water and ultrasonically dissolve it until fully dissolved. Add 5 mg, 10 mg, 20 mg, 30 mg, and 40 mg of 5-fluorouracil drugs into the above solution respectively. After stirring in the dark at room temperature for 24 h (300 r / min), centrifuge the drug-loaded samples (the corresponding carriers are C / ZnO and C / ZnO / polydopamine composites, and the drug-loaded samples are correspondingly marked as C / ZnO / 5-FU and C / ZnO / PDA / 5-FU). Take the supernatant and use an ultraviolet tester to measure the absorbance of 5-fluorouracil at 266 nm. Calculate the drug concentration in the supernatant from the standard curve, and calculate the encapsulation efficiency (D LE %) and drug loading (D LC %) of the drug delivery nanosystem according to the following formula:

[0061]

[0062]

[0063] Among them, M O is interpreted as the drug content in the carrier, M N is the total mass of the final drug-loaded carrier, and M C represents the initial amount of drug input.

[0064] 9. Drug sustained-release performance test

[0065] In vitro drug sustained-release performance experiments use 5-fluorouracil as a model drug to systematically study the sustained-release behavior of the drug-loaded system through the dynamic dialysis method. The specific experimental process is as follows: First, pretreat the dialysis bag with a molecular weight cut-off of 14 kDa by boiling it in a 50% ethanol solution in a water bath for 30 min to remove surfactants and activate the membrane pore structure. Seal the accurately weighed drug-loaded nanocomposite in the activated dialysis bag, and then immerse it in a release system containing 80 mL of phosphate buffer solution (PBS, pH 7.4). This medium condition simulates the normal tissue fluid environment. At different time intervals, extract 3 mL of the solution from the release medium and replace it with fresh PBS buffer solution. Use an ultraviolet-visible spectrophotometer to measure the absorbance of the samples at each time point at λmax = 266 nm, calculate the cumulative release amount of 5-FU based on the standard curve equation (the formula is as follows), and draw the relationship curve between the corresponding cumulative release amount and time.

[0066]

[0067] 10. Antibacterial activity test and blood compatibility test

[0068] In this experiment, the typical representatives of Gram-positive and Gram-negative bacteria, Staphylococcus aureus and Escherichia coli, were selected as the experimental strains. The antibacterial activities of the drugs and carriers were evaluated by the minimum inhibitory concentration (MIC) and the minimum bactericidal concentration (MBC). MIC refers to the lowest drug concentration that inhibits bacterial growth in a specific culture medium, while MBC is the lowest concentration required to kill 99.9% of the bacteria. The antibacterial and bactericidal abilities of the antibacterial materials were evaluated through in vitro drug susceptibility tests. The double dilution method was used. The MIC was determined by observing the antibacterial situation of the corresponding wells in the 96-well plate by naked eye and resazurin staining, and the MBC value was verified by the subsequent agar spreading method. The experimental procedure is as follows: (1) Antibacterial efficacy evaluation using the double dilution method: Weigh the test sample accurately and dissolve it in ultrapure water to prepare a mother liquor with gradient dilution. Inject 180 μl of Staphylococcus aureus suspension with a concentration standardized to 10 6 CFU / ml into each well of the 96-well plate, and then add 20 μl of sample solutions with different concentrations. Mix well with a pipette. Set a negative control group (TSB medium) and a positive control group (pure bacterial solution), and set three parallels for each concentration group. Place the processed microplate in an incubator at 37 °C for 24 h, and determine the antibacterial endpoint by turbidimetry - the lowest concentration that completely inhibits bacterial growth is the MIC. For the MIC detection of Escherichia coli, the rest of the operation procedures remain the same except that LB medium is used as the negative control. (2) Select the critical concentration based on the MIC results: Take 100 μl of the bacterial suspension from the completely transparent wells (sterile growth) and the first turbid wells (bacterial survival) respectively, and spread them evenly on the solid agar plate. Synchronously set a blank control without drug treatment. After culturing the plate for 24 h, count the colony forming units (CFU), and the group with the lowest drug concentration and no colony growth is determined as the MBC value. To ensure the reliability of the data, all experiments were performed with three independent replicates.

[0069] The direct contact method was used to determine the blood compatibility of the nanomaterials. Referring to ISO standard 10993-4 (1992), the hemolytic test was carried out using the anticoagulated whole blood of New Zealand white rabbits. If the average hemolysis rate of the sample was less than or equal to 5%, the material was considered non-hemolytic. Experimental steps: The collected whole blood was centrifuged at 2500 rpm for 10 min to remove the upper platelet-rich plasma and the middle layer of white blood cells, then washed with phosphate buffer solution (PBS), and centrifuged at 1500 rpm for 5 min, repeating 2-3 times until the supernatant was colorless to remove the residual plasma. The washed red blood cells were taken and diluted with PBS to a 2% (v / v) red blood cell suspension. 2.5 ml of the 2% red blood cell suspension and 2.5 ml of PBS were added to the sample and incubated at 37 °C for 1 h. 2.5 ml of the 2% red blood cell suspension was added to 2.5 ml of deionized water and PBS buffer solution respectively as positive and negative controls. After the incubation, it was centrifuged at 2000 rpm for 5 min, and the absorbance of the supernatant at a wavelength of 540 nm was measured using a multifunctional microplate reader. The hemolysis rate (HR%) was calculated according to the following formula:

[0070]

[0071] Where OD (+) and OD (-) represent the absorbance values of the positive and negative controls respectively, and OD S represents the absorbance value of the test sample.

[0072] The technical solutions described in the present invention are all conventional solutions in the art unless otherwise specified. The reagents or raw materials used are all purchased from commercial channels or have been made public unless otherwise specified.

[0073] The technical solutions provided by the present invention are described in detail below in conjunction with the embodiments, but they should not be construed as limiting the protection scope of the present invention.

[0074] Example 1

[0075] 22 mL of 0.1 M zinc acetate (Zn(Ac)2·2H2O) ethylene glycol stock solution was added to 10 mL of 0.6 M NaOH ethylene glycol stock solution to form a milky white mixture with a pH value of 10.1. After stirring for 10 min, 0.2 g of glucose was added, and the resulting mixture was transferred to a 75 mL Teflon-lined stainless steel autoclave and then heated at 160 °C for 24 h. Finally, it was centrifuged and washed with deionized water, and dried in an oven at 60 °C for 6 h to obtain C / ZnO.

[0076] The C / ZnO prepared in Example 1 was characterized and its performance was studied as follows:

[0077] 1. Characterization and analysis of C / ZnO (C / ZnO / 5-FU involved in this experiment was prepared according to the above method with m(C / ZnO):m(5-FU) = 1:3).

[0078] (1) FT-IR analysis

[0079] The infrared spectrum of C / ZnO is as Figure 1 shown. There is a strong absorption in the range of 3384 cm -1 , corresponding to the stretching vibration of the hydroxyl group; the characteristic absorption peak of the Zn-O bond can be observed at 471 cm -1 , indicating the successful synthesis of ZnO. In addition, the absorption peak at 2932 cm -1 is the characteristic peak of the saturated C-H bond, and the stretching vibration of C-C is located at 1047 cm -1 . The generation of carbon in the experiment is mainly through the hydrothermal reaction of glucose, which undergoes hydrolysis under high temperature and high pressure to form a carbon structure. Through the characterization of the infrared spectrum, it is found that there is a stretching vibration peak of the C-C bond in the prepared material, confirming that the sample prepared by the solvothermal reaction is a C / ZnO material. By comparing with the infrared spectrum of C / ZnO, it is found that only several characteristic peaks of the drug are observed in the spectrum of the composite C / ZnO / 5-FU, indicating that 5-FU is successfully loaded onto the carrier C / ZnO.

[0080] (2) XRD analysis

[0081] The chemical composition of the obtained C / ZnO was characterized by XRD, and the results are as Figure 2 shown. As can be seen from Figure 2 , this material has significant diffraction peaks at 31.8°, 34.5°, 36.3°, 56.6°, 57.0° and 68.1°. After analysis by JADE software and comparison with the standard PDF card #36-1451, it is found that the interplanar spacing corresponds one by one to the standard card, and all diffraction peaks can be indexed to the (100), (002), (101), (102), (110), (103), (112) lattice planes of hexagonal ZnO in turn. After doping with C, the XRD pattern of C / ZnO still has all the characteristic peaks of ZnO, and no new peaks appear, indicating that C as a surface modifier does not affect the structure of ZnO. In addition, the diffraction peaks between 10° and 30° become significantly rougher, mainly due to amorphous carbon, indicating that the C material is successfully incorporated into the ZnO nanospheres; in addition, there are no any impurity peaks in the pattern, indicating that there are no impurities other than ZnO and carbon in the sample, and the purity of the C / ZnO prepared by the solvothermal method is very high. The diffraction peaks of C / ZnO have strong and sharp characteristics, indicating that the prepared C / ZnO has good crystallinity.

[0082] (3) SEM analysis

[0083] The morphology of C / ZnO was studied by SEM analysis, and the results are as Figure 3 shown (in the figure, a) 1.6k, b) 10k, c) 20k, d) 30k); it can be Figure 3 seen that C / ZnO is spherical particles with uniform distribution, and the size is distributed between 1 - 2 μm. The surface morphology of the C / ZnO material is observed to be rough and is formed by the aggregation of a large number of small particles. The polymerization of the C / ZnO material is mainly due to the addition of glucose during the synthesis of ZnO. Under solvothermal conditions, glucose will undergo various chemical reactions, which leads to the generation of a complex mixture of some aromatic compounds and oligosaccharides. These organic compounds can increase the viscosity of the resulting solution and cause polymerization into spheres. In addition, the growth direction of ZnO is also affected by glucose. The high negative charge of glucose will mainly interact with the positively charged (0001) surface of the ZnO crystal. These interactions reduce the surface free energy of the positive plane and inhibit any directional growth of the ZnO atomic nucleus, resulting in an equiaxed or spherical particle morphology. The EDS surface scan element distribution of C / ZnO is as Figure 4 shown, and it can be observed Figure 4 that the Zn, O, and C elements in C / ZnO are evenly distributed, and the Zn, O, and C elements account for 30.87%, 33.87%, and 35.26% respectively. It is not difficult to find from the element ratio that some carbon has been successfully incorporated into the ZnO crystal structure. Through the EDS energy spectrum diagram, it is confirmed that this material is a C / ZnO nanomaterial.

[0084] (4) TGA analysis

[0085] The thermal stability of C / ZnO was characterized by a synchronous thermal analyzer, as Figure 5 shown. During the stepwise heating process, the weight loss of the C / ZnO material reaches 15.1%. As the temperature continues to rise, the weight tends to be stable. When heating from room temperature of 25 °C to 235 °C, a small amount of free water adsorbed on the surface of C / ZnO evaporates, resulting in a weight loss of about 4.5%. Subsequently, during the heating process from 235 °C to 800 °C, the C material in C / ZnO undergoes thermal decomposition, resulting in a weight loss of 10.6%. The analysis results show that C has been successfully incorporated into ZnO, and the C loading is 10.6%, which is consistent with the EDS results. Incorporating an appropriate amount of C will not only affect the crystallization process of ZnO, thereby controlling the shape and size of ZnO particles, but also a moderate C loading is likely to result in a material with a higher specific surface area and a larger pore structure, which enables them to better adsorb or load other substances and improve the slow-release performance.

[0086] (5) XPS analysis

[0087] XPS technology is used to detect the chemical element composition and elemental valence state structure in samples. To further characterize the samples, the XPS full-scan spectra and high-resolution spectra of each element of C / ZnO were measured. The XPS full-scan spectrum of C / ZnO is as shown in Figure 6 below. The elemental composition of the sample is Zn, O, and C elements, which corresponds to the previously measured mapping results. The atomic percentage of Zn, O, and C elements in the composite material is 26.16%, 37.01%, and 36.83% respectively. Figure 6 b)-d) in show the high-resolution spectra of Zn 2p, C 1s, and O 1s of the C / ZnO material. Figure 6 As shown in b), the Zn 2p spectrum consists of two symmetric peaks. The position of the Zn 2p peak and its spin-orbit splitting energy basically coincide with the standard values of ZnO, which can confirm that Zn in the sample exists in the form of divalent oxidation state. Figure 6 c) in shows the C 1s XPS spectrum of the prepared spherical C / ZnO nanostructure. Two peaks centered at 284.8 and 286.4 eV can be determined, corresponding to C-C and C-O respectively. Among them, the peak at 286.4 eV is attributed to residual carbon, indicating the presence of residual carbon in C / ZnO. It can be seen that the binding energy of C shifts towards higher energy. The main reason may be that during the preparation of the sample, C substitutes and dopes Zn. Zinc atoms are usually Zn in ZnO 2+ , while carbon has a stronger electronegativity, which will cause changes in the electron density of surrounding atoms. The substitution of carbon in ZnO may lead to changes in the electron interaction between carbon atoms and oxygen atoms, thus affecting the electron cloud density of carbon, making the C 1s electrons more strongly attracted, resulting in an increase in the binding energy. In addition, carbon atoms replace zinc and form new bonds (C-O) with oxygen. This local chemical environment change may also lead to an increase in the binding energy of the C 1s peak. The high-resolution spectrum of O 1s is as shown in Figure 6 d). Through fitting, it is found that for C / ZnO, the centers of the fitting curves are located at 532.28 eV, 531.39 eV, and 530.37 eV respectively. The peak at 530.37 can be attributed to O surrounded by Zn in the ZnO lattice 2+ . And the peak at 531.39 eV should be attributed to surface oxygen species. The higher binding energy peak at 532.28 eV may have different reasons, such as oxygen vacancies, hydroxyl groups, or C-O bonds. 2-

[0088] (6) BET analysis

[0089] To further understand the porous structure and pore size distribution of the prepared C / ZnO, the specific surface area of N2 adsorption - desorption was measured by the BET method, and the pore size distribution of the adsorption and desorption branches of the N2 isotherm was measured by the Barrett - Joyner - Halenda (BJH) method. As shown in a) of 7, the N2 adsorption - desorption isotherm of spherical C / ZnO presents type IV, indicating the existence of abundant mesoporous structures in the structure. Materials composed of plate - like particle aggregates (loose aggregates) have a wide hysteresis loop in the relative pressure range of 0.3 to 1.0, forming slit - like pores. In addition, as can be seen from b) of 7, the pore size distribution is relatively narrow, with a sharp peak near 4.7 nm. The total specific surface area of C / ZnO is about 14457.679 m 2 / g, the pore volume and average pore size are 16.243 cc / g and 4.76 nm respectively. The high specific surface area and narrow mesoporous channels are both conducive to improving the adsorption capacity.

[0090] (7) DLS analysis

[0091] The particle size distribution of the nanocomposite was studied by dynamic light scattering method. As Figure 8 shown, the average size of the C / ZnO material is 1560 nm, which is consistent with the scanning electron microscope results; the polydispersity index of C / ZnO is 0.0673, indicating that the C / ZnO nanomaterials exhibit excellent water dispersibility. Zeta potential, as a core parameter in nanotechnology, provides key theoretical support for the field of drug delivery by quantifying the correlation between surface charge and stability. The Zeta potential value of the C / ZnO nanomaterials is - 14.15 mV. The negative charge on the material surface is mainly due to the ionization of oxygen - containing functional groups of the carbon component and the deprotonation of surface hydroxyl groups of ZnO, indicating that the nanomaterials have good stability. Generally, the surface Zeta potential shows the external repulsive force between the outer surfaces of nanoparticles. As this value increases, there will be more repulsive forces, which can lead to preventing adhesion and enhancing electrostatic stability. In addition, negatively charged nanocomposites in the blood have a slower metabolism than positively charged nanocomposites, which makes them stay in the circulatory system for a longer time. Due to the high affinity between negatively charged nanoparticles and positively charged cell membranes, negatively charged nanocomposites are more biocompatible than positively charged nanocomposites. The potential of the composite system is - 16.84 mV, reflecting the charge superposition effect of the drug and the carrier. The absolute value of the Zeta potential is positively correlated with the surface charge density of the particles. The larger the specific surface area, the higher the surface charge density, and the higher the absolute value of the Zeta potential. The high absolute value of the potential of the drug - loaded material is mainly due to the loading of 5 - fluorouracil molecules.

[0092] 2. Performance study of C / ZnO

[0093] (1) Study on the drug - loading and release behavior of C / ZnO

[0094] To investigate the effect of the mass ratio of C / ZnO as a carrier to the drug (5-FU) on the encapsulation efficiency and drug loading of the material, 15 mL of deionized water was used, the mass of the carrier was 10 mg, and the mass ratios m(C / ZnO):m(5-FU) were 2:1, 1:1, 1:2, 1:3, and 1:4. Stirring was carried out in the dark at room temperature, and the supernatant was taken by centrifugation to prepare C / ZnO / 5-FU. The encapsulation efficiency and drug loading were calculated.

[0095] (i) Loading of 5-fluorouracil drug

[0096] The results of the encapsulation efficiency are shown in Table 1, and the results of the drug loading are shown in Table 2.

[0097] Table 1 Results of encapsulation efficiency

[0098]

[0099] Table 2 Results of drug loading

[0100]

[0101] From the data in Table 1, it can be seen that the encapsulation efficiency of the drug decreases with the increase of the drug content. The optimal condition for C / ZnO to load 5-FU is that the mass ratio of the carrier to the drug is 2:1, and the encapsulation efficiency of the drug is 62.8% at this time. From the data in Table 2, it can be seen that the drug loading increases with the increase of the drug content. When the mass ratio of the carrier to the drug is 1:4, the drug loading begins to decline, indicating that the drug loading reaches saturation. In summary, the optimal condition for C / ZnO to load 5-FU is that the mass ratio of the carrier to the drug is 1:3, and the drug loading reaches the maximum at this time, which is 32.8%. C / ZnO / 5-FU prepared with m(C / ZnO):m(5-FU) = 1:3 was used for subsequent experiments.

[0102] (ii) Drug release test of C / ZnO

[0103] To study the release behavior of 5-FU under in vitro triggering, a neutral (pH 7.4) release system was selected to simulate body fluids. Figure 9 For the cumulative release behavior of 5-FU from C / ZnO / 5-FU in a phosphate buffer solution at pH 7.4. At room temperature, the release amount of the drug reached 33.0% within 8 h, which conforms to the "burst release effect". The main reason may be the mesopores (average pore diameter 4.76 nm) and high specific surface area (BET 14457.679 m 2(g)Enable the surface-loaded active substance (drug) to preferentially contact the medium and rapidly dissociate through physical adsorption / weak chemical bonds. The drug release rate significantly decreases within 10 - 25 h, and the cumulative release rate reaches 40.0%. This may be due to the formation of hydrogen bonds or coordination bonds between the hydroxyl groups on the ZnO surface and the amino / N-H groups of the active substance (such as 5-fluorouracil), which requires a higher activation energy for dissociation. The above results of slow drug release indicate that C / ZnO has great potential for drug delivery.

[0104] (2)Study on the antibacterial activity and blood compatibility of C / ZnO

[0105] (i)Study on the antibacterial activity of C / ZnO

[0106] ①Determination of the minimum inhibitory concentration (MIC), and the results are as Figure 10 shown in Table 3.

[0107] Table 3 Results of the minimum inhibitory concentration of the release solutions in each group

[0108]

[0109] Figure 10 In a1 and a2 in, they are the MIC result graphs of C / ZnO / 5-FU against Staphylococcus aureus under the action of different concentration samples. The results show that C / ZnO / 5-FU has a certain antibacterial effect on Staphylococcus aureus, and as the addition amount increases, the turbidity of its solution gradually decreases. The concentrations of C / ZnO / 5-FU from left to right are 300 μg / ml, 150 μg / ml, etc. After resazurin staining, the color of the fifth column of wells changes from blue to red (the fourth column of wells is completely clear), so 37.5 μg / ml is determined as the minimum inhibitory concentration of C / ZnO / 5-FU against S. aureus. In b1 and b2 in 10, they are the MIC result graphs of C / ZnO / 5-FU against Escherichia coli under the action of different concentration samples. The concentrations of C / ZnO / 5-FU from left to right are 220 μg / ml, 110 μg / ml, etc. By visually observing the color change in the well plate, 55.0 μg / ml is determined as the minimum inhibitory concentration of C / ZnO / 5-FU against Escherichia coli.

[0110] ②Determination of the minimum bactericidal concentration (MBC), and the results are as Figure 11 shown.

[0111] The MBC observation results of C / ZnO / 5-FU against Staphylococcus aureus and Escherichia coli are as Figure 11 shown. The change in the number of Staphylococcus aureus colonies during the culture is shown in Figure 11 a)-c) in. The control group Figure 11In a), the initial cell count of Staphylococcus aureus was approximately 110 CFU / g. As the drug concentration increased (from left to right), the number of S. aureus colonies in the figure decreased significantly. In the 2MIC group, the total number of bacteria was 0 CFU / g. Therefore, the MBC of C / ZnO / 5-FU against S. aureus was 75.0 μg / ml. The changes in the number of Escherichia coli colonies during the culture process are shown in Figure 11 d)-f) in this text. The change in the number of E. coli colonies was similar to that of S. aureus. In the 2MIC group, the total number of bacteria was 0 CFU / g. Therefore, the MBC of C / ZnO / 5-FU against E. coli was 110 μg / ml.

[0112] The antibacterial experiment results showed that the drug-loaded C / ZnO exhibited significant inhibitory effects on both tested strains. Specifically, its MIC and MBC against S. aureus and E. coli were 37.5 μg / mL and 75.0 μg / mL (for S. aureus), 50.0 μg / mL and 100 μg / mL (for E. coli), respectively. It is worth noting that compared with the antibacterial efficacy of pure 5-FU (MIC = 46.9 μg / mL, MBC = 93.8 μg / mL for S. aureus; MIC = 55.0 μg / mL, MBC = 110 μg / mL for E. coli), the drug-loaded C / ZnO system showed better antibacterial activity, with its MIC and MBC values decreasing by approximately 20.0% and 20.0% (for S. aureus) and 9.10% and 9.10% (for E. coli), respectively. The reason for the enhanced antibacterial performance of the drug-loaded C / ZnO may be due to the ROS oxidation of ZnO, Zn 2+ dissolution, and physical destruction mechanisms. The introduction of the carbon matrix may achieve synergistic effects by enhancing the photocatalytic efficiency, regulating ion release, and optimizing the adsorption performance. Moreover, the antibacterial effect of the C / ZnO system on S. aureus was better than that on E. coli, mainly because the cell wall of Gram-positive bacteria has more negative charges, and the electrostatic adsorption of ZnO is more significant, resulting in a stronger antibacterial effect.

[0113] (ii) Blood compatibility study of C / ZnO

[0114] In the hemolysis test, Figure 12 (Positive in the figure represents the positive control, and Negative represents the negative control) showed that the blood sample incubated with deionized water was a red transparent solution, indicating that red blood cells ruptured and lysed, and hemolysis occurred. However, no visible hemolysis phenomenon was observed for C / ZnO, and this material could meet the requirements of general biological experiments. Figure 12 The relative hemolysis rates of each group were less than 5%, indicating that the C / ZnO material had good blood compatibility.

[0115] Example 2

[0116] Under ultrasonic treatment, 300 mg of C / ZnO prepared in Example 1 was dispersed in 90 mL of deionized water for 0.5 h. Then, 90 mg of PDA was added to the C / ZnO dispersion, and the mixture was mechanically stirred for 0.5 h to obtain a uniform ZnO / PDA aqueous solution. 3 mL of NaOH solution (0.1 mol / L) was gradually added dropwise to the above mixture to adjust the pH to 8.5. After reacting for 3 h, the product was collected by centrifugation at 8000 rpm and washed three times with deionized water. Finally, the PDA-coated C / ZnO material was dried in a vacuum oven at 80 °C for 12 h to obtain the C / ZnO / polydopamine composite material, denoted as C / ZnO / PDA.

[0117] The C / ZnO / PDA prepared in Example 2 was characterized and analyzed for its performance as follows:

[0118] 1. Characterization and analysis of C / ZnO / PDA (In this experiment, C / ZnO / PDA / 5-FU involved was prepared according to the method described above with m(C / ZnO / PDA):m(5-FU) = 1:3)

[0119] (1) FT-IR analysis

[0120] The functional groups of C / ZnO / PDA were analyzed using a Fourier transform infrared spectrometer, and the obtained spectrum is as Figure 13 shown. The main absorption peaks in the infrared spectrum of C / ZnO / PDA are basically consistent with those in the infrared spectrum of PDA-coated C / ZnO in previous research results, proving the successful attachment of PDA on the surface of C / ZnO NPs. The spectral analysis is as follows: The band around 472 cm -1 is the Zn-O stretching vibration peak. The absorption peak around 1594 cm -1 is due to the shear vibration of the N-H bond. The absorption peaks around 1490 cm -1 and 1283 cm -1 are related to the stretching and bending vibrations of the C-O group on the benzene ring, respectively. These characteristic peaks (1594, 1490, and 1283 cm -1 ) confirm the polymerization of PDA. It is worth noting that after complexing with dopamine, a blue shift occurs at the wavenumber of 3300 cm -1 , and the absorption at this point is mainly due to -NH in the polymer molecular structure of PDA. The -OH or -NH2 of dopamine may bond with Zn on the surface of ZnO 2+Coordination occurs to form Zn-O or Zn-N bonds. The formation of such chemical bonds changes the electron cloud distribution of O-H or N-H bonds, increasing their vibration frequencies, thereby resulting in a blue shift. In addition, under alkaline conditions, dopamine is prone to oxidative self-polymerization to form polydopamine. During the polymerization process, hydrogen bonds and π-π stacking interactions between dopamine molecules change the vibration environment of O-H or N-H, leading to an increase in vibration frequency and thus causing a blue shift. The infrared spectrum of C / ZnO / PDA / 5-FU shows that 1640 and 1245 cm -1 correspond to the C=O stretching vibration and C-F stretching vibration of the 5-FU molecule respectively, indicating that the drug molecule has been successfully loaded onto the carrier C / ZnO / PDA.

[0121] (2) XRD analysis

[0122] Figure 14 This is the XRD spectrum of the C / ZnO / PDA material. It can be seen from it that all samples have obvious diffraction peaks at 31.8°, 34.5°, 36.3°, 47.5°, 56.6°, 62.8°, and 68°, corresponding one by one to the crystal planes of wurtzite ZnO. The positions of the characteristic peaks are consistent with the standard card JCPDS card No. 36-1451. The XRD spectrum of C / ZnO / PDA shows all the characteristic peaks of C / ZnO, and the peak intensity ratios are roughly the same, proving that the carbon-doped zinc oxide grown after PDA modification is still in the hexagonal wurtzite structure. These diffraction peaks are high and sharp, indicating that the C / ZnO / PDA sample has good crystallinity after dopamine compounding. In addition, a new broad peak appears between 2θ = 15° and 20° for C / ZnO / PDA, which is due to the lack of long-range order in the arrangement of PDA molecular chains and exists in an amorphous or weakly crystalline state, indicating that PDA has been successfully compounded with C / ZnO.

[0123] (3) SEM analysis

[0124] Figure 15 Shows the scanning electron microscope images of the C / ZnO / PDA material at different magnifications. It can be seen from Figure 15 that the C / ZnO / PDA material retains the C / ZnO nanosphere structure, and the size of this nanosphere is between 900 nm and 2 μm. As a multifunctional polymer, polydopamine forms a protective film on the surface of ZnO, and there are some fine attachments or deposits on the particle surface. After observing the sample, it is found that a layer of PDA polymer layer is evenly deposited on the surface of C / ZnO nanoparticles, as shown in Figure 15 c) and d) in it. This result shows that under alkaline conditions, the dopamine precursor can spontaneously polymerize to form a PDA polymer and tightly adhere to the surface of C / ZnO. The composition and element distribution of the sample are further determined by performing an elemental surface distribution scan on the C / ZnO / PDA sample, as shown in Figure 16As shown, the Zn element accounts for 14.3%, the O element accounts for 25.28%, the C element accounts for 59.15%, and the N element accounts for 1.28%. Among them, the content of the N element is relatively low, mainly because the source of N is only PDA, and there is only one secondary amino group in the molecular framework structure of PDA. Therefore, the content of its N element is small, and the test results are consistent with this.

[0125] (4) TGA analysis

[0126] The thermal stability of the C / ZnO / PDA material was characterized by a synchronous thermal analyzer, as Figure 17 shown. The TGA curve of C / ZnO / PDA usually shows three typical thermal decomposition stages: when the temperature is raised from room temperature of 25 °C to 150 °C, a small amount of free water or residual solvent adsorbed on the surface of the C / ZnO / PDA nanospheres volatilizes, resulting in a weight loss of about 3%. Subsequently, during the heating process from 150 °C to 500 °C, PDA undergoes decarboxylation and deamination reactions in nitrogen, releasing small molecule gases such as CO2, NH3, and H2O, and accompanied by the breaking of molecular chains to form an amorphous carbon structure. At the same time, the carbon component in C / ZnO may be further oxidized or pyrolyzed, leading to an increased mass loss. Research shows that the interaction between the catechol structure of polydopamine and ZnO may delay its decomposition rate, forming some stable intermediate products, resulting in a weight loss of up to 8%. Finally, the residue between 500 °C and 800 °C is mainly the inorganic component ZnO and the thermally stable carbon skeleton. The analysis results show that C / ZnO and PDA are successfully compounded. This staged thermal stability indicates that the material has high structural stability within the physiological temperature range (such as 37 °C), and can avoid the problem of sudden drug release caused by temperature fluctuations.

[0127] (5) XPS analysis

[0128] X-ray photoelectron spectroscopy analysis reveals the elemental composition and chemical valence states of C / ZnO / PDA. As Figure 18 shown, C / ZnO / PDA is mainly composed of C, O, Zn, and N, which indicates that the preparation of C / ZnO / PDA is successful. Compared with the C / ZnO sample, the contents of C and N elements in the C / ZnO / PDA sample increase, mainly due to the carbon skeleton and -NH groups in the PDA framework structure attached to the ZnO surface.

[0129] The high-resolution XPS spectrum of the Zn element in C / ZnO / PDA is similar to that of C / ZnO, both showing the signal peaks of Zn 2p 3 / 2 and Zn 2p 1 / 2 . It is worth noting that in the high-resolution XPS spectrum of the Zn element in the C / ZnO / PDA sample, the position of this peak shifts towards the high binding energy direction compared to the C / ZnO material, as Figure 19As shown in a). This may be because the electrons of ZnO are partially extracted by PDA (such as forming an interfacial dipole), then the oxidation state of Zn may be more "positive", resulting in an increase in its binding energy; Zn 2+ The strong coordination effect with PDA leads to a decrease in the local electron density, which will also cause an increase in the binding energy. The high-resolution C 1s spectrum has three signal peaks. Among them, the peaks at 288.37 eV and 286.41 eV belong to -C=O and C-N / C-O respectively, and the peak at 284.8 eV belongs to C-C / C-H. In addition, from Figure 19 c) and d), it can be seen that the oxygen element of the -C-O group and the nitrogen element in the -NH group can be detected in the sample, which indicates that under mild buffer solution conditions, dopamine can be easily polycondensed into PDA and firmly attached to the surface of ZnO. It can be clearly seen that the C / ZnO / PDA has the most oxygen vacancies, and at the same time, the binding energy of each component is the lowest. The increase in oxygen vacancies will lead to changes in the surface electronic structure, thereby improving the surface activity of the material. The improvement of surface activity helps the interaction between the drug and the material, and then enhances the drug attachment or encapsulation ability, which may help to control the drug release rate. The high-resolution XPS spectra of C 1s, N 1s and O 1s further confirm the successful loading of PDA on C / ZnO.

[0130] (6) BET analysis

[0131] Figure 20 are the adsorption - desorption isotherm curve and pore size distribution diagram of C / ZnO / PDA. From Figure 20 it can be seen that the nitrogen adsorption - desorption curve type of C / ZnO / PDA is a type Ⅳ isotherm, and the adsorption isotherm of this material has no hysteresis loop. The pore size is concentrated at about 1.7 nm, indicating that micropores dominate in the C / ZnO / CS material. The total specific surface area of C / ZnO / PDA is about 136.67 m 2 / g, and the pore volume and average pore size are 0.185 cc / g and 5.77 nm respectively. The decrease in the pore volume of the C / ZnO / PDA material indicates that PDA has completely wrapped the C / ZnO nanospheres, and the drug is adsorbed onto the carrier mainly due to the viscosity of PDA. The reason for the non - closure of the BET adsorption - desorption curve may be that polydopamine, as a surface - modifying material, has a high surface energy and rich functional groups (such as phenolic hydroxyl groups, amino groups, etc.). These functional groups can form strong interactions with gas molecules, thus affecting the adsorption behavior of gas molecules on the material surface and resulting in kinetic differences in the adsorption and desorption processes.

[0132] (7) DLS analysis

[0133] C / ZnO / PDA has good water - dispersibility. As Figure 21As shown, the particle size of C / ZnO / PDA was determined to be 1674 nm by the DLS method, which was slightly larger than that of C / ZnO, probably due to the continuous polymerization of PDA. In addition, the composite also had a good PDI, with a value of 0.241. After being modified with PDA, the absolute value of the Zeta potential was slightly larger than that of C / ZnO, being -18.9 mV ( Figure 21 in b) of - ). After being modified with PDA, the increase in electronegativity was mainly due to the formation of a polydopamine (PDA) coating on the surface of C / ZnO by the self-polymerization reaction of dopamine molecules. The catechol and amino functional groups in its molecular chain regulated the interfacial charge distribution: the catechol group in PDA was partially deprotonated to generate O -1 in a near-neutral or weakly alkaline solution (pH ≈ 7.4), significantly increasing the surface negative charge density. This process could be observed by FT-IR characterization through the blue shift and intensity decrease of the phenolic hydroxyl peak (about 3200 cm

[0134] 2. Drug loading and release behavior of C / ZnO / PDA

[0135] (1) Loading of 5-fluorouracil drug

[0136] The effects of the mass ratio of C / ZnO / PDA (carrier) to drug and the drug loading time on the drug loading capacity of the carrier were investigated. The deionized water was 15 mL, the mass of the carrier was 10 mg, and the mass ratios m(C / ZnO / PDA):m(5-FU) were 2:1, 1:1, 1:2, 1:3, 1:4. Stirring was carried out at room temperature in the dark, with stirring times of 12 h, 24 h, 48 h (300 r / min). The supernatant was taken by centrifugation, and the drug loading capacity and encapsulation efficiency were calculated. The results are shown in Tables 4 and 5.

[0137] Table 4 Effects of the mass ratio of carrier to drug and stirring time on the encapsulation efficiency

[0138]

[0139] Table 5 Effects of the mass ratio of carrier to drug and stirring time on the drug loading capacity

[0140]

[0141] The effects of the mass ratio of carrier to drug and stirring time on the encapsulation efficiency and drug loading are shown in Tables 4 and 5. From the data in the tables, it can be found that as the content of 5-FU in the drug-loading solution increases, the drug loading shows a positive correlation. When the mass ratio of carrier to drug is 1:3, the drug loading is the largest. Whether it is the drug loading or the encapsulation efficiency, the stirring time of 24 h is overall better than 12 h and 48 h. The encapsulation efficiency can reach 21.0% and the drug loading can reach 38.7% after stirring for 24 h. As the stirring time is extended and the mass ratio of carrier to drug further increases, the change in drug loading is small, indicating that the drug-loading ability of the carrier reaches saturation. Therefore, the optimal conditions for C / ZnO / PDA to load 5-FU are that the mass ratio of carrier to drug is 1:3 and the drug-loading time is 24 h. C / ZnO / PDA / 5-FU prepared with m(C / ZnO / PDA):m(5-FU) = 1:3 and a stirring time of 24 h was used for subsequent experiments.

[0142] (2) Drug sustained-release test of C / ZnO / PDA

[0143] As a drug delivery system, the sustained and stable release of drugs is of great significance for the subsequent exertion of biological functions. As Figure 22 shown, the release curve of the C / ZnO / PDA sample loaded with 5-fluorouracil was recorded. In the first 8 h, the C / ZnO material released rapidly, and the cumulative release amount was as high as about 33.0%. Subsequently, it released slowly and tended to be stable. The sustained-release time was 24 h, and the cumulative release rate was 40.0%. However, C / ZnO / PDA had a "fast release" stage within 3 h, and then the release curve gradually stabilized, and a total of 64.3% of the drug amount was released continuously until the 33rd h. The polydopamine coating made the drug sustained-release time 10 h longer than that of the C / ZnO material. The possible reason is that in the aqueous environment, the C / ZnO material and dopamine form a stable composite interface structure through the chelation coordination of Zn 2+ with catechol groups and the π-π conjugation effect. Secondly, the amino and hydroxyl functional groups in dopamine molecules can form multiple hydrogen bonds and electrostatic interactions with the pyrimidine ring and fluorine atoms of 5-FU, and at the same time, coordinate binding is generated through the oxygen vacancies on the ZnO surface and the N-H group of 5-FU. This synergistic effect significantly enhances the drug affinity of the composite material, increases the encapsulation efficiency to 21.0%, and the drug loading reaches 38.7%. In addition, the self-assembled layer of DA on the ZnO surface can adjust the surface Zeta potential of the material to -18.9 mV, inhibit drug leakage through the electrostatic repulsion effect, and at the same time enhance the charge complementary adsorption with 5-FU at physiological pH. XPS characterization further confirmed that the Zn 2p binding energy of C / ZnO after PDA modification shifted, indicating that the interfacial chemical bonding formed by electron transfer may be the key mechanism to improve the drug loading stability.

[0144] (3) Antibacterial activity study of C / ZnO / polydopamine composite materials

[0145] (i) Determination of minimum inhibitory concentration (MIC)

[0146] Figure 23 In a1 and a2, they are the MIC result graphs of C / ZnO / PDA / 5-FU against Staphylococcus aureus under the action of different concentrations of samples. The results show that C / ZnO / PDA / 5-FU has a certain antibacterial effect on S. aureus, and with the increase of its addition amount, the turbidity of its solution gradually decreases. From left to right, the concentrations of C / ZnO / PDA / 5-FU are 160 μg / ml, 80.0 μg / ml, etc. After resazurin staining, the color of the fifth column of wells changes from blue to red (the fourth column of wells is completely clear), so 20.0 μg / ml is determined to be the minimum inhibitory concentration of C / ZnO / PDA / 5-FU against S. aureus. Figure 23 In b1 and b2, they are the MIC result graphs of C / ZnO / PDA / 5-FU against Escherichia coli under the action of different concentrations of samples. From left to right, the concentrations of C / ZnO / PDA / 5-FU are 650 μg / ml, 325 μg / ml, etc. By visually observing the color change in the well plate, 40.6 μg / ml is determined to be the minimum inhibitory concentration of C / ZnO / PDA / 5-FU against E. coli. The antibacterial effect of C / ZnO / PDA mainly stems from the adhesion of the PDA coating, which can inhibit bacterial adhesion through physical action, and the PDA coating can serve as a carrier for metal ions (Zn 2+ ), and enhance antibacterial activity through ion release.

[0147] Table 6 Minimum inhibitory concentration results of the release solutions of each group

[0148]

[0149] (ii) Determination of minimum bactericidal concentration (MBC)

[0150] The MBC observation results of C / ZnO / PDA / 5-FU against Staphylococcus aureus and Escherichia coli are as Figure 24 shown. The change in the number of Staphylococcus aureus colonies during the culture process is shown in Figure 24 a)-c). In the control group Figure 24 a), the initial cell count of Staphylococcus aureus is approximately 95 CFU / g. With the increase of the drug concentration (from left to right), the number of S. aureus colonies in the figure decreases significantly. In the 2MIC group, the total number of bacteria is 0 CFU / g, so the MBC of C / ZnO / PDA / 5-FU against S. aureus is 40.0 μg / ml. The change in the number of Escherichia coli colonies during the culture process is shown in Figure 24 d)-f). The change in the number of E. coli colonies in the figure is similar to that of Staphylococcus aureus, so the MBC of C / ZnO / PDA / 5-FU against E. coli is 81.3 μg / ml.

[0151] The antibacterial experiment results show that the drug-loaded C / ZnO / PDA exhibits significant inhibitory effects on both tested strains. Specifically, its MIC and MBC against Staphylococcus aureus are 20.0 μg / mL and 40.0 μg / mL, respectively; its MIC and MBC against Escherichia coli are 40.6 μg / mL and 81.3 μg / mL, respectively. It is worth noting that the antibacterial activity of the drug-loaded C / ZnO / PDA (i.e., C / ZnO / PDA / 5-FU) is better than that of the drug-loaded C / ZnO (i.e., C / ZnO / 5-FU), which is due to the result of the PDA coating. The results show that the C / ZnO / PDA nanocomposite has the potential for antibacterial applications.

[0152] (4) Blood compatibility study of C / ZnO / polydopamine composite

[0153] In this invention, the blood compatibility of the C / ZnO / PDA composite was evaluated through in vitro hemolysis experiments (as Figure 25 shown, Positive in the figure represents the positive control, and Negative represents the negative control). Three groups were set up in the experiment: the positive control group, the negative control group, and the C / ZnO / PDA experimental group. The hemolysis rate detection results show that the absorbance of the supernatant in the negative control group is close to the baseline level, the test tube liquid in the negative control group is uniformly dark red, and the hemolysis rate reaches 100%. While the hemolysis rate of the C / ZnO / PDA experimental group is less than 3%. The physiological saline in the negative control group has no membrane-damaging activity, and the red blood cells maintain their complete morphology and settle naturally. The reason for using the hemolysis rate of the positive control group as a reference value is that deionized water, as a typical hypotonic solution, forms a significant osmotic gradient with the intracellular fluid of red blood cells. Through osmotic pressure drive, the cell membrane expands and ruptures (i.e., osmotic hemolysis). The main reason for the low hemolysis rate of the C / ZnO / PDA experimental group is that the catechol groups of dopamine can scavenge reactive oxygen species, inhibit the Zn 2+ -mediated Fenton-like reaction, and reduce the level of lipid peroxidation. In addition, studies have shown that PDA immobilizes ZnO nanoparticles (NPs) through chelation, delaying the Zn 2+ release rate and reducing ion toxicity. The above data show that C / ZnO / PDA has no obvious destructive effect on the stability of the red blood cell membrane, meeting the safety threshold of the hemolysis rate of biomedical materials (<5%).

[0154] The present invention uses C / ZnO / PDA as a drug carrier and the small molecule drug 5-fluorouracil as a drug model to prepare a drug sustained-release system. The single-factor fixed-variable method is adopted to explore the optimal conditions for the drug encapsulation efficiency and drug loading, and the drug sustained-release performance of C / ZnO / PDA is tested. The results show that when the mass ratio of the carrier to the drug is 1:3 and the stirring time is 24 h, the encapsulation efficiency and drug loading of the carrier reach the best, the encapsulation efficiency is 21.0%, and the drug loading is 38.7%. The in vitro release study of the drug shows that C / ZnO / PDA has significant controlled-release performance for 5-FU. Specifically, compared with the C / ZnO system without composite polydopamine (the sustained-release time is 24 h and the cumulative release rate is 40.0%), the sustained-release time of the C / ZnO / PDA system is extended to 33 h and the cumulative release rate is increased to 64.3%. When dopamine is added to the system, due to the increase in the viscosity of the system, the burst release of the drug is alleviated and the effect of the sustained-release action is enhanced. The in vitro hemolysis experiment based on quantitative analysis by spectrophotometry shows that the hemolysis rate of C / ZnO / PDA is significantly lower than the 5% safety threshold, confirming its excellent blood compatibility. The antibacterial performance test is carried out systematically by the micro broth dilution method, and the composite material shows good antibacterial effects against Staphylococcus aureus and Escherichia coli, and its antibacterial activity is better than that of C / ZnO.

[0155] The embodiments described above are only used to describe the preferred mode of the present invention, and do not limit the scope of the present invention. Without departing from the design spirit of the present invention, various deformations and improvements made by those of ordinary skill in the art to the technical solution of the present invention shall fall within the protection scope determined by the claims of the present invention.

Claims

1. A preparation method of a C / ZnO / polydopamine composite material, characterized in that It includes the following steps: Step 1: Uniformly disperse a zinc salt and a carbon source in an organic solvent and carry out a solvothermal reaction to obtain C / ZnO; Step 2: Disperse the C / ZnO in water, then add polydopamine and mix well, and carry out a reaction under alkaline conditions to obtain a C / ZnO / polydopamine composite material.

2. The preparation method according to claim 1, wherein In Step 1, the zinc source is zinc acetate; the carbon source is glucose; the ratio of the zinc source to the carbon source is (2.0 - 2.4) mmol∶(0.18 - 0.22) g.

3. The preparation method according to claim 1, wherein In Step 1, the organic solvent is ethylene glycol.

4. The preparation method according to claim 1, characterized in that, In Step 1, the pH of the solvothermal reaction is 10.1; the temperature of the solvothermal reaction is 160 °C, and the time is 24 h.

5. The preparation method according to claim 1, characterized in that, In Step 2, the mass ratio of the C / ZnO to the polydopamine is (0.90 - 1.1)∶(0.27 - 0.33); the mass-volume ratio of the C / ZnO to water is (9.0 - 11) mg∶(2.7 - 3.3) mL.

6. The preparation method according to claim 1, wherein The pH of the reaction is 8.5; the temperature of the reaction is room temperature; the time of the reaction is 3 h. The C / ZnO / polydopamine composite material prepared by the preparation method according to any one of claims 1 - 6.

9. The application of the C / ZnO / polydopamine composite material according to claim 7 in the preparation of sustained-release and controlled-release drugs.

9. A sustained and controlled release drug, characterized in that, It is prepared by dissolving the C / ZnO / polydopamine composite material and 5-fluorouracil in water and stirring under light-shielded conditions.

10. The sustained-release or controlled-release drug according to claim 9, characterized in that, The mass ratio of the C / ZnO / polydopamine composite material to the 5-fluorouracil is (0.25 - 2)∶1; the stirring time is 12 - 48 h.

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