A method for preparing Fe3O4-based magnetic nanomaterials and their antibacterial applications

Abstract

This invention discloses a method for preparing Fe3O4-based magnetic nanomaterials. The nanomaterials use iron(III) oxide (Fe3O4) as a core, and phenylenediamine and copper are co-modified onto their surface via a stirring method. On one hand, the phenylenediamine surface is rich in functional groups, which is beneficial for subsequent functionalization modification; its aniline-like structure can effectively enhance the photothermal effect of the nanomaterials. On the other hand, after modification with copper, the nanomaterials have a high affinity for bacteria, achieving rapid enrichment and efficient capture of pathogenic bacteria through electrostatic and metal coordination interactions. Furthermore, the photothermal effect generated by this magnetic nanomaterial under infrared light irradiation can synergistically enhance its enzyme-like activity, achieving highly efficient sterilization. Most importantly, this material can also efficiently remove harmful products generated after bacterial lysis, including peptidoglycan and lipopolysaccharide. This invention effectively solves the technical defects of traditional antibacterial materials, such as limited functionality and inability to remove toxic lysis products, demonstrating strong practicality and broad application prospects.

Description

Technical Field

[0001] This invention belongs to the field of bio-nanomaterials technology, specifically relating to a method for preparing Fe3O4-based magnetic nanomaterials and their applications in antibacterial and photothermal conversion. Background Technology

[0002] Bacterial infections pose a significant global public health challenge, with their threat to human health continuing to escalate and creating a heavy socioeconomic burden. Current core strategies for treating bacterial infections in clinical practice focus on bactericidal and bacteriostatic methods, aiming to directly eliminate pathogens and halt infection progression. However, this approach has significant limitations. It focuses solely on killing the pathogens, neglecting the toxic lysis products such as lipopolysaccharides and peptidoglycans released after bacterial lysis. These toxic products can easily cause secondary damage to the body and exacerbate the infection.

[0003] Lipopolysaccharide (LPS), a key endotoxin, can overactivate the host's immune response, inducing systemic inflammatory damage and becoming a significant contributing factor to severe complications such as endotoxemia and multiple organ failure. Peptidoglycan fragments can act as danger signals, mediating the adhesion and aggregation of pathogens to form a three-dimensional biofilm, helping bacteria resist external pressures such as immune clearance and antibacterial drugs, leading to chronic and persistent infections. Therefore, current therapies cannot simultaneously address both bactericidal activity and the clearance of lysis products, necessitating the development of novel antibacterial strategies with dual efficacy.

[0004] Most antibacterial nanomaterials possess enzyme-like activity, generating highly toxic reactive oxygen species (ROS) that disrupt bacterial cell membranes, proteins, or nucleic acids, achieving efficient sterilization. However, these materials have limitations: the binding force between nanomaterials and bacteria is weak, and the short lifetime and limited diffusion distance of ROS result in insufficient local effective concentrations, significantly weakening the antibacterial effect and making it difficult to meet clinical treatment needs.

[0005] Ferric oxide (Fe3O4) magnetic materials possess the advantages of superparamagnetism, excellent photothermal properties, and ease of modification, making them ideal substrates for constructing multifunctional antibacterial systems. They are promising candidates for simultaneously capturing and killing bacteria and removing toxic lysis products. Modification can enhance enzyme-like activity and strengthen the material's ability to bind to bacteria, enabling in-situ generation of reactive oxygen species (ROS) on the bacterial surface. This effectively shortens the ROS diffusion distance and prolongs the duration of local action, overcoming the shortcomings of existing technologies and demonstrating broad application prospects in the treatment of bacterial infections. Summary of the Invention

[0006] To address the shortcomings of existing technologies, this invention discloses a method for preparing Fe3O4-based magnetic nanomaterials and their antibacterial applications. The Fe3O4-based magnetic nanomaterials are modified with copper and phenylenediamine. Through electrostatic and metal coordination interactions, the affinity between the material and bacterial cell walls is effectively enhanced, achieving rapid enrichment and efficient capture of pathogenic bacteria. This magnetic nanomaterial can generate ROS in situ on the bacterial surface, significantly shortening the ROS interaction distance, reducing loss, and prolonging the duration of action. It also possesses both enzyme-like activity and photothermal effects, with a dual mechanism working synergistically to efficiently kill bacteria. In vitro antibacterial experiments have confirmed that the nanomaterial achieves 100% antibacterial efficiency against Escherichia coli, AREC, Staphylococcus aureus, and MRSA. Furthermore, the material can efficiently remove harmful products generated by bacterial lysis, achieving a 55% removal efficiency of bacterial lysates within 10 minutes, thereby reducing biosafety risks and improving the biosafety of antibacterial therapy. This invention is suitable for antibacterial treatment of drug-resistant pathogens and has good application and promotion value.

[0007] To achieve the above-mentioned objectives, the present invention adopts the following technical solution: (1) Dissolve ferrous sulfate (FeSO4) and ferric chloride (FeCl3) in 50-100 mL of deionized water to prepare a mixed solution. Stir the mixed solution magnetically at 40-70℃ for 10-40 min. Then add 5-10 mL of NH3·H2O (25%) to the mixed solution and continue stirring for 30-90 min. Collect the product with a magnet and wash it alternately with deionized water and ethanol 2-3 times. Freeze-dry the product to obtain iron(III) oxide nanoparticles. The mass ratio of FeSO4 to FeCl3 is 1:1 to 2.5; (2) Add the iron(III) oxide and phenylenediamine solid from step (1) to 80 mL of deionized water, disperse and mix by ultrasonication, and adjust the pH of the mixture to 3.0-5.0 with hydrochloric acid (1M); then add ammonium persulfate ((NH4)2S2O8) to the mixture, stir magnetically at 20-50℃ for 1-2 h, separate the product with a magnet, and wash with deionized water and ethanol alternately to obtain iron(III) oxide-phenylenediamine magnetic nanomaterials; The phenylenediamine is one or more of o-phenylenediamine, m-phenylenediamine and p-phenylenediamine, the mass ratio of iron oxide to phenylenediamine is 1:0.25-4, and the mass ratio of phenylenediamine to ammonium persulfate is 1:1-4; (3) Add 50-100 mg of the iron oxide-phenylenediamine magnetic nanomaterial from step (2) and 5-10 mL of 0.2-2 mg / mL copper salt solution to 40 mL of deionized water. Adjust the pH of the mixture to 7.0-9.0 with 1 M sodium hydroxide solution. Stir magnetically at 20-50 °C for 2-6 h. Separate the product with a magnet. Wash with deionized water and ethanol alternately to obtain the iron oxide-phenylenediamine-copper magnetic nanomaterial.

[0008] The copper salt is one or both of cuprous chloride and cupric chloride.

[0009] Another objective of this invention is to apply the Fe3O4-based magnetic nanomaterials prepared by the above method in the preparation of photothermal conversion materials and antibacterial materials; wherein the antibacterial bacteria include Escherichia coli, ampicillin-resistant Escherichia coli (AREC), Staphylococcus aureus, and methicillin-resistant Staphylococcus aureus (MRSA).

[0010] Compared with the prior art, the present invention has the following advantages: (1) This invention modifies magnetic nanomaterials with copper to improve the affinity between the material and the bacterial cell wall, thereby achieving efficient bacterial capture and solving the problems of poor targeting and easy bacterial escape of traditional antibacterial materials. This material can rapidly accumulate pathogenic bacteria, shorten the action distance, and provide a basis for efficient sterilization.

[0011] (2) The magnetic nanomaterials described in this invention can generate ROS in situ on the surface of bacteria, significantly shorten the ROS action distance, reduce losses and prolong the action time, achieve precise sterilization and improve antibacterial efficiency.

[0012] (3) The magnetic nanomaterials described in this invention possess both enzyme-like activity and photothermal effect, which work synergistically to achieve highly efficient sterilization. Photothermal acceleration of enzymatic reactions, combined with high temperature, results in dual destruction of bacterial structure, with significantly better effects than single-mode action. This material exhibits excellent antibacterial properties against Escherichia coli, AREC, Staphylococcus aureus, and MRSA, with an antibacterial efficiency of up to 100%.

[0013] (4) The present invention can efficiently remove bacterial lysis products through electrostatic coordination with metal, reduce biosafety risks, and improve the biosafety of antibacterial treatment. Attached Figure Description

[0014] Figure 1 Transmission electron microscopy image of the magnetite-o-phenylenediamine-copper magnetic nanomaterial; Figure 2 This is a temperature rise diagram of nanomaterials under near-infrared light. Figure 3 The UV-Vis absorption spectrum for detecting peroxidase activity in nanomaterials; Figure 4The UV-Vis absorption spectrum for detecting the activity of nanomaterial-based oxidases; Figure 5 The UV-Vis absorption spectrum for detecting the activity of laccases in nanomaterials; Figure 6 The UV-Vis absorption spectrum for detecting the activity of superoxide dismutase in nanomaterials; Figure 7 The UV-Vis absorption spectrum for detecting catalase activity in nanomaterials; Figure 8 The graph shows the capture rate of nanomaterials against four types of bacteria. Figure 9 Scanning electron microscope image of AREC captured by the iron(II) tetroxide-o-phenylenediamine-copper magnetic nanomaterial; Figure 10 The results of cytotoxicity tests on the iron tetroxide-o-phenylenediamine-copper magnetic nanomaterials; Figure 11 Images showing the effects of different nanomaterials coated onto flat plates; Figure 12 Figure showing the antibacterial efficiency of different nanomaterials; Figure 13 The graph shows the effect of biofilm clearance as determined by the crystal violet method. Figure 14 Images of residual live (green) bacteria and biofilm extracellular matrix (red) in a biofilm; Figure 15 The efficiency of the iron oxide-o-phenylenediamine-copper magnetic nanomaterial in removing AREC(a) and MRSA(b) lysis solutions was evaluated. Figure 16 The scavenging efficiency of the iron tetroxide-o-phenylenediamine-copper magnetic nanomaterial for lipopolysaccharide (a) and peptidoglycan (b). Detailed Implementation

[0015] The present invention will be further explained below with reference to the accompanying drawings and embodiments. However, these examples do not limit the scope of protection of the present invention. Unless otherwise specified, the methods in the embodiments are conventional methods, and unless otherwise specified, the reagents used are conventional commercial reagents or reagents prepared according to conventional methods. Example 1: Preparation method and antibacterial application of Fe3O4-based magnetic nanomaterials 1. Preparation of Fe3O4@OPD-Cu magnetic nanomaterials (Fe3O4@OPD-Cu) Dissolve 3g of FeCl3 and 2g of FeSO4 in 80mL of deionized water and sonicate to obtain a mixed solution. Stir the solution magnetically at 50℃ for 15min, then add 6mL of NH3·H2O (25%) to the mixed solution and continue stirring for 60min. Collect the product with a magnet, wash it three times each with water and ethanol, and freeze-dry the product to obtain ferric oxide (Fe3O4). 100 mg Fe3O4 and 50 mg o-phenylenediamine (OPD) were added to 80 mL of deionized water and dispersed evenly by ultrasonication. The pH of the mixture was adjusted to 4.0 with 1 M HCl solution. Then, 50 mg of ammonium persulfate was added to the mixture and stirred at room temperature for 2 h. The product was separated by a magnet and washed twice each with deionized water and ethanol to obtain the iron(III) oxide-o-phenylenediamine magnetic nanomaterial (Fe3O4@OPD). 50 mg of Fe3O4@OPD was dispersed in 40 mL of CuCl2 solution (0.6 mg / mL, 10 mL). The pH of the mixture was adjusted to 8.0 with 1 M NaOH solution. After stirring at room temperature for 5 h, the product was separated by a magnet. The mixture was washed twice each with deionized water and ethanol to obtain the magnetite-phenylenediamine-copper magnetic nanomaterial (Fe3O4@OPD-Cu). The transmission electron microscopy results are shown below. Figure 1 As shown.

[0016] 2. Photothermal performance testing of nanomaterials Using near-infrared laser (808nm, 1.0 W / cm) 2 The solutions were irradiated with Fe3O4, Fe3O4@OPD, and Fe3O4@OPD-Cu solutions of the same concentration (160 µg / mL), respectively, with the same volume of deionized water as a blank control. The solution temperature was measured every 30 seconds using a digital thermometer with a thermocouple probe, and the results were recorded continuously for 10 minutes. Figure 2 As shown, the temperature difference of Fe3O4@OPD-Cu (44.8℃) is higher than that of Fe3O4@OPD (43℃) and Fe3O4 (39℃), while the temperature change of deionized water is negligible. This demonstrates that Fe3O4@OPD-Cu exhibits excellent photothermal properties.

[0017] 3. Assay of peroxidase-like activity in nanomaterials 30 µL of Fe3O4, Fe3O4@OPD, and Fe3O4@OPD-Cu solutions were mixed with 50 µL of TMB solution (5 mM) and 50 µL of H2O2 solution (50 mM), respectively. Then, 100 µL of NaAc-HAc (pH 4.0) buffer solution was added, and finally, the volume was adjusted to 1 mL with deionized water. Near-infrared spectroscopy was performed at 808 nm and 1.0 W / cm². 2Irradiate with a near-infrared (NIR) laser for 5 min. Incubate the mixture at room temperature for 10 min, and measure the absorbance of the supernatant using a UV-Vis spectrophotometer; from Figure 3 The results show that the activity of peroxidases in nanomaterials is as follows: Fe3O4@OPD-Cu + NIR > Fe3O4@OPD-Cu > Fe3O4@OPD > Fe3O4.

[0018] Using TMB and H2O2 as substrates, the maximum reaction rate of the above nanomaterials was further analyzed using the Michaelis-Menten equation. V max and Mi constant K m The results are shown in Table 1. When TMB is used as the substrate, Fe3O4@OPD-Cu... V max The efficiency was 6.1 times that of Fe3O4, indicating that the catalytic activity of Fe3O4 was significantly enhanced after surface modification. Under near-infrared (NIR) laser irradiation, Fe3O4@OPD-Cu showed significantly improved catalytic activity regardless of whether the substrate was TMB or H2O2. V max It increased by about 3 times compared to the un-irradiated group, while K m The decrease in the value indicates that it has a stronger binding ability with the substrate, proving that near-infrared irradiation promotes the enzymatic reaction; Table 1 Enzyme reaction kinetics data of nanomaterials ; 4. Determination of other types of enzyme activity in nanomaterials ① Using only TMB as the substrate, the remaining measurement steps are the same as in step 3, and the results are as follows: Figure 4 As shown, Fe3O4@OPD-Cu can also significantly catalyze the oxidation of TMB to blue ox-TMB, indicating that Fe3O4@OPD-Cu has oxidase-like activity; ② Using 4-AP and 2,4-DP as substrates, the laccase activity of the nanomaterials was measured. The substrates bound to the enzyme to form a red product with a characteristic absorption peak at 510 nm. The results are as follows: Figure 5 As shown, Fe3O4@OPD-Cu exhibits laccase-like activity, producing a red product, and has the highest absorption peak, indicating the strongest activity. Fe3O4 and Fe3O4@OPD do not possess laccase-like activity and do not produce a red product. ③ The activity of superoxide dismutase-like enzymes was determined by inhibiting the oxidation of nitrotetrazole blue (NBT) to a blue product. NBT (750 μM), methionine (13 μM), riboflavin (20 μM), and Na2EDTA (100 μM) were added to 0.1 M phosphate-buffered saline (PBS, pH 7.8). The mixture was then thoroughly mixed with 30 μL of Fe3O4, Fe3O4@OPD, and Fe3O4@OPD-Cu solutions, respectively. After reacting under sunlight for 10 min, the absorbance was measured at 560 nm. The results are as follows: Figure 6 As shown, compared with the blank control, all three nanomaterials exhibited superoxide dismutase-like activity; ④ Through H2O2 and Ti 4+ The reaction produces the complex H2O2-Ti 4+ The complex exhibits a characteristic absorption peak at 376 nm; the addition of nanomaterials with catalase-like activity reduces this characteristic absorption peak. The results are as follows: Figure 7 As shown, only Fe3O4@OPD-Cu exhibited catalase-like activity.

[0019] 5. Test of the bacterial capture performance of nanomaterials With Escherichia coli ( E. coli ATCC 25922), ampicillin-resistant Escherichia coli (AREC), Staphylococcus aureus ( S. aureus ATCC 25923 and methicillin-resistant Staphylococcus aureus (MRSA) were used as test strains. The cultured bacterial cells were washed with sterile PBS to remove the culture medium, and then diluted with PBS to OD0.05. 600 Bacterial suspensions were prepared with a concentration of 1.0–1.1. 400 μL of the bacterial suspension was mixed with 100 μL of sterile PBS (control group), Fe3O4, Fe3O4@OPD, and Fe3O4@OPD-Cu solutions, respectively. Each mixture was placed in a 1.5 mL centrifuge tube and incubated at 180 rpm for 10 min on a shaker. The nanomaterials were then separated using a magnet, and the OD of the supernatant was measured. 600 Values ​​were calculated and bacterial capture efficiency was determined; results are as follows: Figure 8 As shown, Fe3O4@OPD-Cu achieved a capture efficiency of over 85% for all four bacteria, significantly higher than Fe3O4 and Fe3O4@OPD. Figure 9 Scanning electron microscopy images of ARECs captured by the iron(III) oxide-o-phenylenediamine-copper magnetic nanomaterial. These experiments demonstrate that the nanomaterial possesses highly efficient and broad-spectrum bacterial capture capabilities.

[0020] 6. Nanomaterial cytotoxicity test The biocompatibility of Fe3O4@OPD-Cu with HCT 116 cells (cancer cells) was tested using the CCK-8 assay. Cells were placed in sterile 96-well plates and incubated with different concentrations of Fe3O4@OPD-Cu at 37°C for 24 h. After adding 50 µL of CCK-8 solution to each well for 2 h, the absorbance at 450 nm was measured in each well to assess cell viability. The results are shown below. Figure 10 As shown, Fe3O4@OPD-Cu exhibits good cell compatibility.

[0021] 7. Study on the in vitro antibacterial properties of nanomaterials Escherichia coli, AREA, Staphylococcus aureus, and MRSA were used as test strains. For each strain, 3-5 single colonies were inoculated into fresh tryptone soybean broth (TSB) and incubated at 37°C for 16-18 hours until the stationary phase. 40 μL of the bacterial culture was then diluted 100-fold with fresh TSB and incubated at 37°C until the OD reached the stationary phase. 600 = 0.5~0.7. After centrifugation to remove the culture medium, wash three times with sterile PBS, and adjust to 1.5×10 with sterile PBS. 6 CFU / mL, 60 μL of bacterial suspension was mixed with 5 mL of physiological saline, and then different nanomaterials and H2O2 (concentration 50 mM) were added. A control group without nanomaterials and H2O2 was also included. The mixture was thoroughly mixed and incubated for 30 min. The NIR group was irradiated with near-infrared light for 15 min, while other parameters remained unchanged. Finally, 100 μL of the mixture was spread onto a solid agar plate and incubated overnight at 37°C until visible colonies formed. The antibacterial efficiency was calculated based on the number of colonies. Flat plate coating effect Figure 11 As shown, the number of bacterial colonies visibly decreased after the addition of Fe3O4@OPD-Cu; the antibacterial efficiency was as follows. Figure 12 As shown, Fe3O4@OPD-Cu exhibits an antibacterial efficiency exceeding 60% against Gram-negative bacteria (Escherichia coli and AREC) and over 80% against Gram-positive bacteria (Staphylococcus aureus and MRSA), while other groups show only slight bactericidal activity. Furthermore, after NIR irradiation, its antibacterial efficiency against Escherichia coli, AREC, Staphylococcus aureus, and MRSA all reached 100%. This demonstrates that Fe3O4@OPD-Cu exhibits excellent antibacterial properties.

[0022] 8. Research on the anti-biofilm effect of nanomaterials ① Take 100µL of each of the following bacteria: Escherichia coli, AREC, Staphylococcus aureus, and MRSA (1×0.5µL). 8The Fe3O4@OPD-Cu suspension (CFU / mL) was added to 24-well plates, along with Fe3O4@OPD-Cu, H2O2 (50 mM), and liquid culture medium to a final volume of 2 mL. A control group without nanomaterials and H2O2 was also included. The NIR group was irradiated with near-infrared light for 30 min, while other parameters remained unchanged. After incubation at 37°C for 48 h, the culture medium was slowly aspirated from each well, and the plates were washed 2-3 times with PBS to obtain biofilms. The biofilms were then fixed with 200 µL of 4% paraformaldehyde for 2 h. The inhibitory effect of Fe3O4@OPD-Cu on biofilms was assessed using crystal violet staining: 200 µL of 0.1% crystal violet solution was added to each well and incubated for 30 min to remove excess solution. 100 µL of 33% acetic acid solution was added to each well to dissolve the crystal violet, and the absorbance was measured at 595 nm using a microplate reader.

[0023] The results are as follows Figure 13 As shown, under the synergistic effect of NIR, Fe3O4@OPD-Cu effectively inhibited biofilm formation of Escherichia coli, AREC, Staphylococcus aureus and MRSA, with biofilm formation inhibition rates of 74.62%, 72.47%, 78.46% and 79.21%, respectively.

[0024] ② Add sterile cell smears to a 24-well plate, then take 100µL each of Escherichia coli, AREC, Staphylococcus aureus, and MRSA (1×10⁻⁶). 8 A suspension of Fe3O4@OPD-Cu and H2O2 (50 mM) (CFU / mL) was added to 24-well plates, and liquid culture medium was added to bring the volume to 2 mL. A control group without nanomaterials and H2O2 was also included. The NIR group was irradiated under near-infrared light for 30 min, while other conditions remained unchanged. After incubation at 37 °C for 48 h, the culture medium was slowly aspirated from each well, and the plates were washed 2-3 times with PBS to obtain biofilms. The biofilms were stained with green fluorescent dye SYTO-9 and red fluorescent dye Alexa Fluor 647 in the dark for 30 min. Subsequently, the slides containing the biofilms were gently rinsed with PBS buffer (pH 7.4) to remove residual fluorescent dyes. Fluorescence imaging was performed using a fluorescence microscope: the excitation wavelength for green fluorescence was 485 nm, and the excitation wavelength for red fluorescence was 650 nm.

[0025] The results are as follows Figure 14As shown, the biofilms formed by *Escherichia coli*, *AREC*, *Staphylococcus aureus*, and the MRSA control group all exhibited significant red and green fluorescence signals, indicating high bacterial cell density and abundant extracellular matrix content on the surface. However, after treatment with Fe3O4@OPD-Cu, the red and green fluorescence intensities decreased significantly, meaning a substantial reduction in the number of surface bacteria and the content of extracellular matrix in the biofilm; this inhibitory effect was even more pronounced when synergistic with NIR.

[0026] The above two experimental results show that Fe3O4@OPD-Cu can effectively inhibit the formation of biofilms by Escherichia coli, AREC, Staphylococcus aureus, and MRSA.

[0027] 9. Study on the removal performance of Fe3O4@OPD-Cu magnetic nanomaterials on bacterial lysate Bacterial lysates were prepared using Gram-negative bacteria AREC and Gram-positive bacteria MRSA, respectively. The specific steps are as follows: the strains were cultured in medium until OD... 600 = 0.4, washed repeatedly with an equal volume of PBS to remove residual culture medium; then the cell suspension was sonicated to induce bacterial lysis. The lysis rate was determined by plate counting (the bacterial suspensions before and after lysis were diluted and plated on agar plates, incubated for 24 h, and then colonies were counted; this lysis protocol achieved a lysis efficiency of 99% for both strains). After lysis, the bacterial lysate was centrifuged for 10 min, then filtered through a 0.22 μm sterile filter to remove intact bacterial cells and cell debris. The resulting clear bacterial lysate was aliquoted and stored at −80℃ for subsequent experiments.

[0028] AREC cell lysis buffer was mixed with different concentrations of Fe3O4@OPD-Cu, and the mixtures were incubated on a shaker at 180 rpm for 10 min. The solid material was then collected using a magnet, and the fluorescence intensity of the supernatant was measured. The scavenging ability of Fe3O4@OPD-Cu on MRSA lysis buffer was determined using the same method.

[0029] The results are as follows Figure 15 As shown, the removal efficiency of Fe3O4@OPD-Cu for bacterial lysates is concentration-dependent. The removal efficiency gradually increases with the increase of nanomaterial concentration. When the nanomaterial concentration is 300 µg / mL, the removal efficiency for both bacterial lysates exceeds 55% within 10 min, demonstrating that Fe3O4@OPD-Cu has a highly efficient removal capability for bacterial lysates.

[0030] 10. Study on the scavenging performance of Fe3O4@OPD-Cu magnetic nanomaterials on lipopolysaccharides and peptidoglycans Take 300 μL of 0.5 mg / mL lipopolysaccharide solution, add 200 μL of Fe3O4@OPD-Cu dispersions of different concentrations, place in 1.5 mL centrifuge tubes, mix and incubate at 180 rpm for 10 min on a shaker, then collect the solid material with a magnet, and finally measure the fluorescence intensity of the supernatant. The scavenging ability of Fe3O4@OPD-Cu on peptidoglycan was determined using the same method.

[0031] The results are as follows Figure 16 As shown, the scavenging efficiency of Fe3O4@OPD-Cu for lipopolysaccharides and peptidoglycans is concentration-dependent. With increasing concentration, the amount of lipopolysaccharides or peptidoglycans remaining in the solution decreases, demonstrating that Fe3O4@OPD-Cu has the ability to scavenge lipopolysaccharides and peptidoglycans.

Claims

1. A method for preparing Fe3O4-based magnetic nanomaterials, characterized in that, Includes the following steps: (1) Dissolve FeSO4 and FeCl3 in 50-100 mL of deionized water, stir magnetically at 40-70 °C for 10-40 min, add 5-10 mL of NH3·H2O to the mixed solution, continue stirring for 30-90 min, collect the product with a magnet, wash with deionized water and ethanol alternately, freeze dry the product to obtain iron oxide nanoparticles; (2) Step (1) Add iron(III) oxide and phenylenediamine to 80 mL of deionized water, disperse and mix by ultrasonication, adjust the pH of the mixture to 3.0-5.0 with 1 M hydrochloric acid solution, add ammonium persulfate to the mixture, stir magnetically at 20-50 °C for 1-2 h, separate the product with a magnet, and wash with deionized water and ethanol alternately to obtain iron(III) oxide-phenylenediamine magnetic nanomaterials; (3) Add 50-100 mg of the iron oxide-phenylenediamine magnetic nanomaterial from step (2) and 5-10 mL of 0.2-2 mg / mL copper salt solution to 40 mL of deionized water. Adjust the pH of the mixture to 7.0-9.0 with 1M sodium hydroxide solution. Stir magnetically at 20-50℃ for 2-6 h. Separate the product with a magnet. Wash with deionized water and ethanol alternately to obtain the iron oxide-phenylenediamine-copper magnetic nanomaterial.

2. The method for preparing Fe3O4-based magnetic nanomaterials according to claim 1, characterized in that: The mass ratio of FeSO4 to FeCl3 is 1:1 to 2.

5.

3. The method for preparing Fe3O4-based magnetic nanomaterials according to claim 1, characterized in that: Phenylenediamine is one or more of o-phenylenediamine, m-phenylenediamine, and p-phenylenediamine.

4. The method for preparing Fe3O4-based magnetic nanomaterials according to claim 3, characterized in that: The mass ratio of ferric oxide to phenylenediamine is 1:0.25–4, and the mass ratio of phenylenediamine to ammonium persulfate is 1:1–4.

5. The method for preparing Fe3O4-based magnetic nanomaterials according to claim 1, characterized in that: The copper salt is one or both of cuprous chloride and cupric chloride.

6. The application of the Fe3O4-phenylenediamine-copper magnetic nanomaterial prepared by the method of any one of claims 1-5 in the preparation of photothermal conversion materials and antibacterial materials.

7. The application according to claim 6, characterized in that: Near-infrared light irradiation is used.

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