Fluorinated polypropylenimine cationic antimicrobial agent, and preparation method and application thereof

Abstract

The application discloses a fluorinated polypropylene imine (F-PPI) cationic antibacterial agent and a preparation method and application thereof. The F-PPI with adjustable molecular weight is synthesized based on 2-propyl oxazine monomers. The chemical structure is clear, the molecular weight is uniform and controllable, the fluorinated group is located at the head of the PPI, the controllability is high, the process repeatability and batch stability are high. The fluorinated group and the main chain amine group cation can improve the antibacterial efficiency of the cationic polymer of the application, and according to the characteristics of fluorine element, the better antibacterial selectivity and biocompatibility are given. The end group fluorination modification is carried out in the linear polypropylene imine polymerization process, which can combine the high hydrophobicity and biological inertia of fluorides to make it become a cationic antibacterial agent with low cytotoxicity and high antibacterial efficiency. The synthesis process of the application is simple and has high repeatability, which is helpful to build the cationic polymer with high efficiency and low toxicity.

Description

Technical Field

[0001] This invention belongs to the field of biomedical polymer materials technology, and particularly relates to a fluorinated polypropylene imine (PPI) cationic antibacterial agent, its preparation method, and its application. Background Technology

[0002] Cationic antibacterial agents are a class of materials that achieve antibacterial effects through the interaction of positively charged cationic groups with the negatively charged microbial cell membranes. Due to their high efficiency, broad spectrum, and unique mechanism of action, these antibacterial agents are widely used in medicine, food, textiles, agriculture, and environmental protection. Bacterial cell membranes are rich in negatively charged molecules, such as lipopolysaccharides in Gram-negative bacteria and teichoic acid in Gram-positive bacteria, providing targets for cationic antibacterial agents. Through electrostatic adsorption, cationic antibacterial agents can disrupt the integrity of the cell membrane, causing increased membrane permeability, leakage of contents, and membrane potential disturbances, thereby leading to cell death. Furthermore, some cationic antibacterial agents can interfere with intracellular metabolic activities or induce the generation of reactive oxygen species (ROS), further enhancing their bactericidal effect. Based on their chemical structure and functional characteristics, cationic antibacterial agents can be classified into various types, including quaternary ammonium salts (such as benzalkonium chloride), guanidine compounds (such as polyhexamethylene biguanide), cationic polymers (such as polyethyleneimine and polypropyleneimine), cationic surfactants, and nanomaterials with surface-modified cationic groups (such as gold nanoparticles and graphene oxide). The advantage of cationic antimicrobial agents lies in their mechanism of action, which is primarily physical disruption, reducing the likelihood of microbial resistance and providing rapid and efficient bactericidal activity. However, these antimicrobial agents also face several challenges, with the potential toxicity of cationic materials and their environmental impact remaining major concerns. These include potential toxicity to mammalian cells, poor environmental degradation, and insufficient antimicrobial selectivity. Therefore, recent research has focused on optimizing charge density, introducing biodegradable groups, and developing composite materials to improve biocompatibility and environmental friendliness. Future research directions include developing materials with higher selectivity and biocompatibility, and combining cationic antimicrobial agents with other antimicrobial mechanisms to address the threat of multidrug-resistant bacteria. Regarding biocompatibility, fluorine atoms reduce the toxicity of cationic polymers. Introducing fluorine atoms into PPI molecules partially replaces or shields the positive charge density of their protonated amino groups. Since high positive charge density PPIs readily engage in strong, nonspecific interactions with cell membranes (especially mammalian cell membranes), leading to membrane damage and cytotoxicity, fluorination significantly reduces these interactions. Furthermore, fluorination improves the amphiphilicity of PPI molecules, giving them higher hydrophobicity and allowing for modulation of polymer-cell membrane interactions. Compared to traditional PPIs, F-PPIs interact more gently with human cell membranes, making their disruptive effect on bacterial cell membranes more effective while causing less interference with mammalian cells, thus reducing toxicity.

[0003] Polypropyleneimine (PPI) cationic polymers are materials with excellent antibacterial properties. PPI molecules contain a large number of cations (amino groups), which can interact with the anionic portions of bacterial cell membranes. Since bacterial membrane surfaces are typically negatively charged, the cations of PPI can electrostatically attract these negatively charged portions, disrupting membrane integrity, leading to leakage of cell contents, and ultimately bacterial death. The cationic nature of PPI not only promotes adsorption to bacterial membranes but can also induce physical damage. PPI molecules can form pores or disrupt membrane structure through interactions with the cell membrane, causing an imbalance between the intracellular and extracellular environments, ultimately killing bacteria. PPI exhibits antibacterial activity against a variety of bacteria, including Gram-negative and Gram-positive bacteria, making it promising for various applications, particularly in antibacterial coatings and medical devices. Unlike some traditional antibacterial agents, PPI has relatively low toxicity, allowing its use in demanding applications such as the biomedical field.

[0004] Unmodified PPIs possess some antibacterial properties, but their hydrophilic amino group structure results in insufficient binding to bacterial cell membranes. Furthermore, their high cationic density makes them somewhat biotoxic to normal biological cells. Therefore, developing cationic polymer antibacterial agents with stronger membrane binding efficiency and lower cytotoxicity is an urgent need.

[0005] Compared to unfluorinated polypropylene imine (PPI), fluorination introduces highly hydrophobic fluorine groups (such as -CF3- or -CF2-), enhancing its interaction with the lipid bilayer of bacterial cell membranes. The hydrophobic components of the bacterial cell membrane are more easily disrupted by fluorinated molecules, thus improving the antibacterial effect. Furthermore, fluorinated polypropylene imine may exhibit better bactericidal effects against some highly resistant pathogens (such as biofilm-forming bacteria). In terms of physical properties, fluorine has extremely low reactivity and high chemical stability, making fluorinated PPI less prone to degradation in harsh chemical environments. The polyfluorinated groups also increase the material's thermal stability, allowing it to maintain structural and performance stability even at high temperatures.

[0006] Many existing cationic antibacterial agents (such as quaternary ammonium salts and cationic polymers), while highly effective at killing bacteria, may also exhibit some toxicity to mammalian cells, limiting their application in the biomedical field. Some cationic antibacterial agents are easily degraded or inactivated in the environment, leading to a decline in antibacterial performance, especially under high-salt or high-temperature conditions. Some cationic antibacterial agents are less effective against certain types of bacteria or fungi, making them difficult to cope with complex multi-species environments. Furthermore, long-term use of cationic antibacterial agents may lead to bacterial tolerance, for example, by altering the cell membrane surface charge or secreting protective substances, thus reducing their antibacterial efficacy. Summary of the Invention

[0007] Based on the problems pointed out in the background art, the present invention aims to provide a fluorinated polypropylene imine (F-PPI) cationic antibacterial agent, its preparation method and application.

[0008] To achieve the above objectives, according to one aspect of the present invention, a fluorinated polypropyleneimine (F-PPI) is provided, the structure of which is shown in formula (Ⅰ):

[0009]

[0010] Equation (I)

[0011] Wherein, 0≤n≤7, 0≤m≤3, 10≤p≤500. Preferably, 10≤p≤100.

[0012] To achieve the above objectives, according to one aspect of the present invention, a method for preparing the above-mentioned F-PPI is provided, comprising the following steps:

[0013] A. Nitrile and propanolamine were refluxed and heated under zinc acetate catalysis. The product was dissolved in a solvent (dichloromethane or ethyl acetate), and then extracted with water to ensure complete removal of propanolamine. The lower organic layer was collected, dried over anhydrous MgSO4, filtered, and the filtrate was rotary evaporated to obtain 2-propyl-2-oxazine monomer. The evaporated 2-propyl-2-oxazine monomer was dehydrated by vacuum distillation, and the pure fraction was collected. After adding anhydrous magnesium sulfate, completely dry 2-propyl-2-oxazine monomer was obtained.

[0014] The molar ratio of butyronitrile to propanolamine is 1:1 to 1.2; the reflux heating reaction conditions are a slow reaction at 110℃-150℃ for 2 to 4 days, preferably a slow reaction at 120℃-130℃ for 2 to 3 days.

[0015] The rotary evaporation process involves first distilling off DCM at room temperature, then heating to 35-55°C to distill off most of the butyronitrile, yielding the crude 2-propyl-2-oxazine monomer product.

[0016] The vacuum distillation process for removing water involves distilling the crude monomer product under reduced pressure until no more liquid drips out, heating to 80°C, observing for 20 minutes to ensure no nitrile distillate is released, heating to 100°C, discarding the first 2 mL of liquid, changing the bottle, heating to 120°C, and collecting the pure fraction.

[0017] B. Dissolve the dried 2-propyl-2-oxazine and the fluorinated polyalkyl initiator in a solvent (acetonitrile, chlorobenzene or dichlorobenzene) and react them in a closed container. After the reaction is complete, dissolve the fluorinated poly(2-propyl-2-oxazine) in a mild solvent (dichloromethane, ethyl acetate, or ethanol, etc.) and transfer it to a reaction flask. Remove the residual solvent by rotary evaporation at a temperature of 30℃~70℃ to obtain the fluorinated poly(2-propyl-2-oxazine) with the following structural formula (II):

[0018]

[0019] Formula (II)

[0020] C. Add hydrochloric acid to react. After the reaction is complete, precipitate in a precipitation solvent, wash, and dry to obtain F-PPI.

[0021] The concentration of hydrochloric acid is 6-12 mol / L; the reaction temperature is 60-100℃; the reaction time is 48-96 h; the precipitation solvent includes one or more of methanol, ethanol, diethyl ether, and acetone, which are pre-cooled in an ice-water bath for at least 15 min before use; the drying is performed in a vacuum oven until the product is a white powder.

[0022] To achieve the objective of this invention, another aspect of this invention provides the application of fluorinated polypropyleneimine (F-PPI) of formula (I) in antibacterial applications. For example, F-PPI of formula (I) can be used as an antibacterial active ingredient to prepare antibacterial coatings, biomedical materials, or drug delivery carriers.

[0023] In one or more embodiments of the present invention, 1H,1H,2H,2H-perfluoro-1-decanol, 1,1,2,2-tetrahydroperfluorohexyliodide, and 3,3,4,4,4-pentafluoro-1-iodobutane were used as different polyfluoroalkyl initiators to analyze the antibacterial results of F-PPIs with different fluorinated end groups, demonstrating that lower fluorination degrees have better antibacterial effects. In one or more embodiments of the present invention, three F-PPIs with the same degree of fluorination (10, 20, and 50) were synthesized, and the antibacterial results of F-PPIs with different degrees of polymerization were analyzed to demonstrate that higher polymerization degrees have better antibacterial effects.

[0024] This invention uses 2-propyloxazine monomer as a base to synthesize F-PPIs with adjustable molecular weight. The chemical structure is well-defined, and the molecular weight is uniform and controllable. The fluorinated group is located at the beginning of the PPI, resulting in high controllability and high process repeatability and batch stability. Both the fluorinated group and the main chain amine cation can improve the antibacterial efficiency of the cationic polymer of this invention, and the properties of fluorine endow it with better antibacterial selectivity and biocompatibility.

[0025] This invention adds a carbon atom to linear polyethyleneimine (LPEI) to transform it into linear polypropyleneimine (LPPI), and then modifies it with fluorination to synthesize a cationic antibacterial agent with superior antibacterial properties, low cytotoxicity, and high biocompatibility. Linear polypropyleneimine (LPPI) can disrupt bacterial cell membranes through electrostatic interactions. LPPI contains a large number of protonated amino groups, which carry a positive charge under physiological conditions. These positive charges can strongly adsorb negatively charged components on the bacterial surface, such as lipopolysaccharides of Gram-negative bacteria and teichoic acid of Gram-positive bacteria. Simultaneously, electrostatic adsorption leads to disordered charge distribution on the bacterial cell membrane surface, disrupting membrane integrity, increasing permeability, and thus causing leakage of cell contents. When the adsorption force is strong enough, LPPI can directly disrupt the structural integrity of the cell membrane, causing irreversible membrane damage. Building upon this, fluorination of the end groups of LPPI generates fluorinated polypropyleneimine (F-PPI). Due to the high lipophilicity of fluorine atoms, F-PPI enhances the hydrophobic interaction with the cell membrane, allowing it to form a tight bond with the fatty acid tails of the cell membrane through hydrophobic interactions, thereby strengthening its adsorption capacity. The strong covalent nature and low polarizability of the fluorine-carbon bond also contribute to more stable insertion and binding into the cell membrane, further enhancing its adhesion ability. Inside the cell, the cationic nature of F-PPI makes it easy for it to bind to DNA or RNA after entering the cell, interfering with nucleic acid function and inhibiting gene transcription and protein synthesis. F-PPI may also interact with bacterial proteins, especially key enzymes, thereby affecting normal bacterial metabolism and physiological functions.

[0026] This invention utilizes polyfluoroalkyl groups to fluorinate PPI, thereby preparing an F-PPI cationic polymer antibacterial agent. The introduced fluorine atoms reduce the toxicity of the cationic polymer, improve the hydrophobicity and balanced hydrophilicity of the compound, reduce non-specific interactions with human cells, and simultaneously enhance highly efficient antibacterial activity against bacterial cells. This molecular design significantly improves the biocompatibility of F-PPI, making it more promising for applications in antibacterial coatings, biomedical materials, and drug delivery. Attached Figure Description

[0027] Figure 1 The data are the 1H NMR spectra of the 2-propyloxazine monomer prepared in Example 1.

[0028] Figure 2 The data provided are GPC data for characterizing the molecular weight of the PPI and F-PPI cationic polymers prepared in this invention.

[0029] Figure 3 The 1H NMR data are for poly(2-propyl)oxazine with intermediate polymer 10.

[0030] Figure 4 The 1H NMR data are for poly(2-propyl)oxazine with intermediate polymer 20.

[0031] Figure 5 The 1H NMR data are for poly(2-propyl)oxazine with intermediate polymer 50.

[0032] Figure 6 The 1H NMR data for pentafluoropoly(2-propyl)oxazine with intermediate polymer 50.

[0033] Figure 7 The NMR fluorine spectrum data of pentafluoropoly(2-propyl)oxazine with intermediate polymer 50.

[0034] Figure 8 The 1H NMR data for nonafluoropoly(2-propyl)oxazine with intermediate polymer 50.

[0035] Figure 9 The NMR fluorine spectrum data of nonafluoropoly(2-propyl)oxazine with intermediate polymer 50.

[0036] Figure 10 The 1H NMR data of heptadecanofluoropoly(2-propyl)oxazine with intermediate polymer 50.

[0037] Figure 11 The NMR fluorine spectrum data of heptadecanofluoropoly(2-propyl)oxazine with intermediate polymer 50.

[0038] Figure 12 The 1H NMR spectrum is for 5F-PPI50.

[0039] Figure 13 The 1H NMR spectrum is for 9F-PPI50.

[0040] Figure 14 The 1H NMR spectrum is 17F-PPI50.

[0041] Figure 15 The diagram shows the antibacterial effect of the F-PPI cationic polymer antibacterial agent prepared in this invention and the PPI control group against Staphylococcus aureus.

[0042] Figure 16The image shows the antibacterial effect of the F-PPI cationic polymer antibacterial agent prepared in this invention and the PPI control group against Escherichia coli (E. coli).

[0043] Figure 17 The diagram shows the antibacterial effect of the F-PPI cationic polymer antibacterial agent prepared in this invention and the PPI control group against methicillin-resistant Staphylococcus aureus (MRSA).

[0044] Figure 18 The image shows the hemolysis test results of mouse blood on the F-PPI cationic polymer antibacterial agent prepared in this invention and the PPI control group.

[0045] Figure 19 The graph shows the cytotoxicity test results of the 50-degree-of-polymer F-PPI cationic polymer antibacterial agent prepared in this invention and the corresponding PPI control group.

[0046] Figure 20 The curve showing the effect of the 5F-PPI50 cationic polymer antibacterial agent prepared in this invention on Escherichia coli over time.

[0047] Figure 21 SEM images showing the morphological changes of bacteria before and after co-culturing with the 5F-PPI50 cationic polymer antibacterial agent prepared in this invention. Detailed Implementation

[0048] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0049] The following embodiments of the present invention provide a method for synthesizing fluorinated polypropyleneimine (F-PPI), and the synthetic route is as follows:

[0050] Example 1

[0051] Preparation of 2-propyl-2-oxazine monomer: 2 mol of butyronitrile and 2 mol of propanolamine were added to a three-necked flask and refluxed under zinc acetate catalysis at 110℃-150℃ for 2-4 days. The product was dissolved in CH2Cl2 and extracted six times with 150 mL of water to ensure complete removal of propanolamine. The lower organic layer was removed, dried with anhydrous MgSO4, filtered, and the filtrate was rotary evaporated. The rotary evaporation temperature was controlled; first, DCM was distilled off at room temperature, then the temperature was raised to 35-55℃ to distill off most of the butyronitrile, yielding crude 2-propyl-2-oxazine monomer. The crude monomer was then distilled under reduced pressure until no more droplets were expelled. The temperature was raised to 80℃ and observed for 20 minutes to ensure no more butyronitrile was distilled off. The temperature was raised to 100℃, the first 2 mL of liquid was discarded, the mixture was transferred to a new flask, and the temperature was raised to 120℃. The pure fraction was collected to obtain the dehydrated 2-propyl-2-oxazine monomer, with a yield of 96%. The 1H NMR spectrum of the prepared 2-propyloxazine monomer is shown in the figure. Figure 1 . Example 2

[0052] In this embodiment, 2-propyl-2-oxazine monomer was used as the substrate and methyl p-toluenesulfonate as the initiator. Polypropyleneimides with different degrees of polymerization were prepared by controlling the molar ratio of initiator to monomer (1:5~50), labeled as PPIm (m=5, 10, 20, 50). The specific preparation method is as follows:

[0053] (1) Take 0.0764 mol of 2-propyl-2-oxazine in a synthesis flask, take methyl p-toluenesulfonate as an initiator, take 10 ml of acetonitrile as a solvent, and stir at 85℃ for 24~48 h to obtain poly(2-propyl)oxazine with different degrees of polymerization.

[0054] (2) The obtained poly(2-propyl)oxazine was rotary evaporated at 70°C to remove the solvent acetonitrile. The purified poly(2-propyl)oxazine was then hydrolyzed with 6 mol / L hydrochloric acid at 100°C for 72 h to obtain polypropyleneimine.

[0055] (3) The product after precipitation and hydrolysis with acetone was filtered, evaporated to dryness, and then dried under vacuum to obtain polypropylene imines with different degrees of polymerization, which were white solid powders. The yields of polypropylene imines of different polymers are shown in Table 1. Figure 3-5 The 1H NMR spectrum data for the intermediate product poly(2-propyl)oxazine.

[0056] Table 1. Yields of polypropylene imine at different degrees of polymerization

[0057] . Example 3

[0058] In this embodiment, 2-propyl-2-oxazine monomer was reacted with a fluorinated polyalkyl initiator. By controlling the molar ratio of initiator to monomer (1:10~50), terminally fluorinated polypropyleneimides with different degrees of polymerization were prepared and labeled as xF-PPIm (x represents the number of fluorine atoms in the molecule, and m represents the degree of polymerization). The preparation method is the same as in Example 2.

[0059] Table 2. Yields of fluorinated polypropylene imine at different degrees of polymerization

[0060] . Example 4

[0061] Antibacterial tests (for Escherichia coli, Staphylococcus aureus, and drug-resistant bacteria) were conducted on synthesized PPIs with different degrees of polymerization and fluorinated PPIs.

[0062] 1. Streak glycerol strains (Staphylococcus aureus, Escherichia coli, methicillin-resistant Staphylococcus aureus (MRSA)) onto MHA agar plates and incubate at 37°C for 18-24 hours until colonies are fully grown.

[0063] 2. Preparation of bacterial suspension: Take a single colony, inoculate it into 5 mL of MHB medium, and incubate at 37°C with shaking for 4-6 hours until the logarithmic growth phase (OD600 ≈ 0.5, equivalent to 1.5 × 10⁻⁶). 8 CFU / mL). Dilute with physiological saline (0.9% NaCl) to 5 × 10⁻⁶ CFU / mL. 5 CFU / mL (MIC experimental standard concentration). Next, add 100 μL MHB to each well of a sterile 96-well plate. Add 100 μL F-PPI (32 μg / mL) to the first column, then perform 2-fold serial dilutions to column 7 (16 μg / mL, 8 μg / mL, 4 μg / mL, 2 μg / mL, 1 μg / mL, 0.5 μg / mL), with column 8 serving as a blank control (no antibiotic). Each concentration has three replicates. Add 100 μL of bacterial suspension (5 × 10⁻⁶) to each well. 5 (CFU / mL), final volume 200 μL. (Positive control group: containing only bacteria, no antibiotics added. Take 100 μL of culture medium from each well (i.e., different concentrations of F-PPI treatment group) and spread it onto MHA agar plates using a sterile spreader (3 parallel samples for each concentration). Incubate the plates at 37°C for 18–24 hours until bacterial colonies form. Observe the colony growth of each group and calculate the total number of colonies (CFU, Colony-Forming Unit) on each agar plate. Count the colony count and calculate the survival rate relative to the positive control (antibiotic-free group).)

[0064] Test results are as follows Figure 15 Analysis of the antibacterial test results for Staphylococcus aureus (pp. 16, 17) showed that, in the absence of fluorine, PPIs with high polymerization degree had better antibacterial performance than those with low polymerization degree, and fluorinated PPIs had better antibacterial performance than unfluorinated PPIs. Furthermore, fluorinated PPIs with high polymerization degree had better antibacterial performance than those with low polymerization degree, and low fluorination degree had better antibacterial performance than high fluorination degree. The same conclusions were reached in experiments on Escherichia coli and drug-resistant bacteria. Example 5

[0065] Hemolysis tests were performed on synthesized PPIs with different degrees of polymerization and fluorinated PPIs:

[0066] 1. Red blood cell separation: Take 3 mL of anticoagulated mouse blood, centrifuge at 400 g for 5 min, and discard the supernatant. Wash 3 times with PBS and resuspend in a 10% red blood cell suspension.

[0067] 2. Hemolysis Assay: 100 μL of erythrocyte suspension was transferred to a 96-well plate. 100 μL of 320–10 μL / ml F-PPI (different concentrations) was added to each well in sequence according to the concentration gradient. A saline group (0% hemolysis) and a deionized water group (100% hemolysis) were set as controls. The plates were incubated at 37°C for 1 h, then centrifuged at 1000g for 3 min, and the supernatant was collected. The absorbance (OD value) was measured at 540 nm using a spectrophotometer.

[0068] Test results are as follows Figure 18 Analysis of the hemolysis test results shows that, compared to the unfluorinated PPI50, the hemolysis rate remained within 5% at the effective antibacterial concentration. Example 6

[0069] Cytotoxicity tests were conducted on synthesized PPIs with different degrees of polymerization and fluorinated PPIs:

[0070] B16F10 cells were seeded into 96-well plates at a ratio of 1 × 10⁶ cells / well. 4 Cells were seeded at a density of 10 cells / well. Cells were cultured in DMEM medium containing 10% fetal bovine serum (FBS) and 1% penicillin-streptomycin at 37°C and 5% CO2 for 24 hours until the cells reached the logarithmic growth phase.

[0071] 1. Treatment group: F-PPI solution was added to 96-well plates at different concentrations (decreasing sequentially from 320 μg / mL) to achieve a final concentration of 10 μL solution / 100 μL culture medium.

[0072] 2. Control group: Add the same volume of solvent (e.g., PBS or deionized water) as a control group. After incubation for 24 hours, add 10 μL MTT (5 mg / mL) to each well and continue incubation at 37°C for 4 hours. Aspirate the culture medium and add 150 μL LDMSO (to dissolve formazan crystals). Gently shake for 10 min to completely dissolve the purple product. Measure the absorbance (OD value) at 570 nm using an ELISA reader.

[0073] Test results are as follows Figure 19 Analysis of cytotoxicity results showed that high fluorination levels were more cytotoxic than low fluorination levels, and at effective antibacterial concentrations, fluorinated PPIs did not exhibit significant cytotoxicity. Example 7

[0074] The antibacterial effect of the synthesized fluorinated PPI was tested over time:

[0075] 1. Preparation of bacterial suspension: Extract *E. coli* from the glycerol strain and streak it onto MHA agar plates. Incubate at 37°C for 18-24 hours until colonies are fully grown. Take a single colony and inoculate it into 5 mL of MHB medium. Incubate at 37°C with shaking for 4-6 hours until the logarithmic growth phase (OD600 ≈ 0.5, equivalent to 1.5 × 10⁻⁶). 8 (CFU / mL).

[0076] Dilute with physiological saline (0.9% NaCl) to a concentration of 5 × 10⁻⁶. 5 CFU / mL.

[0077] 2. Experimental setup: Incubate 20 ml of a solution with a concentration of 5 × 10⁻⁶ in a 50 ml centrifuge tube. 5 A certain concentration of bacterial solution was added to the CFU / mL bacterial solution, and then 1 ml of bacterial solution was taken every 30 minutes for UV OD600 absorbance test. The bacterial colony concentration was calculated based on the corresponding absorbance.

[0078] Test results are as follows Figure 20 It can be seen that bacterial growth was significantly inhibited at around 30 minutes, and no significant growth of colonies was observed after 60 minutes, indicating that fluorinated PPIs can take effect immediately against bacteria and have excellent antibacterial effects. Example 8

[0079] The micromorphological changes of *S. aureus* and *E. coli* before and after F-PPI treatment were observed using scanning electron microscopy (SEM). *S. aureus* and *E. coli* were collected in EP tubes, centrifuged to enrich, and then incubated with a certain concentration of F-PPI at 37°C for 30 min. The precipitate was collected by centrifugation, washed several times with PBS, centrifuged again, and the supernatant was discarded. 200 μL of 4% glutaraldehyde solution was added to the precipitate, and the mixture was allowed to stand in the dark for 2 h. The mixture was then centrifuged at 5000 rpm and 4°C for 5 min, the supernatant was discarded, and 1 mL of 50% ethanol solution was added. The mixture was stirred evenly and dehydrated for 10 min. The mixture was centrifuged again, and then dehydrated successively with 70%, 90%, and 100% ethanol solutions. After washing with PBS, 10 drops were added to a clean silicon wafer, placed in a 6-well plate, and air-dried overnight. The precipitate was then observed using a scanning electron microscope.

[0080] Test results are as follows Figure 21 It can be observed that after F-PPI treatment, the surface membrane of bacteria is severely damaged compared to normal bacteria, indicating that the drug mainly acts on the bacterial surface and kills bacteria by destroying the bacterial membrane structure.

[0081] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A fluorinated polypropylene imine with antibacterial activity, the structure of which is shown in formula (Ⅰ): , Equation (Ⅰ) in, 0≤n≤7, 0≤m≤3, 10≤p≤100; The preparation method of the fluorinated polypropyleneimine includes the following steps: A. The butyronitrile and propanolamine were reacted under reflux and heating in the presence of zinc acetate as a catalyst. The product was extracted and dried to obtain a completely dry 2-propyl-2-oxazine monomer. B. The dried 2-propyl-2-oxazine and the fluorinated polyalkyl initiator were dissolved in a solvent and reacted in a closed container. After the reaction was completed, the residue was removed by rotary evaporation after dissolving in a good solvent to obtain the fluorinated poly(2-propyl-2-oxazine). C. Add hydrochloric acid to react. After the reaction is complete, precipitate in a precipitation solvent, wash, and dry to obtain fluorinated polypropyleneimine.

2. The method for preparing fluorinated polypropyleneimine according to claim 1, characterized in that, Includes the following steps: A. Butyronitrile and propanolamine were reacted under reflux and heating in the presence of zinc acetate as a catalyst. The product was extracted and dried to obtain a completely dry 2-propyl-2-oxazine monomer. B. The dried 2-propyl-2-oxazine and the fluorinated polyalkyl initiator were dissolved in a solvent and reacted in a closed container. After the reaction was completed, the residue was removed by rotary evaporation after dissolving in a good solvent to obtain the fluorinated poly(2-propyl-2-oxazine). C. Add hydrochloric acid to react. After the reaction is complete, precipitate in a precipitation solvent, wash, and dry to obtain fluorinated polypropyleneimine.

3. The method for preparing fluorinated polypropyleneimine according to claim 2, characterized in that, In step A, the molar ratio of butyronitrile to propanolamine is 1:1 to 1.2; the reflux heating reaction conditions are 110℃ to 150℃ for 2 to 4 days.

4. The method for preparing fluorinated polypropyleneimine according to claim 2, characterized in that, The extraction and drying process described in step A includes: dissolving the product in a solvent, extracting it with water to ensure complete removal of propanolamine; removing the lower organic layer, drying it with anhydrous MgSO4, filtering it, and rotary evaporating the filtrate to obtain crude 2-propyl-2-oxazine monomer; removing water from the rotary-dried 2-propyl-2-oxazine monomer by vacuum distillation, collecting the pure fraction, adding anhydrous magnesium sulfate, and obtaining completely dried 2-propyl-2-oxazine monomer.

5. The method for preparing fluorinated polypropyleneimine according to claim 4, characterized in that, The rotary evaporation process involves first removing the solvent at room temperature, then heating to 35-55°C to distill off most of the butyronitrile, yielding the crude 2-propyl-2-oxazine monomer product.

6. The method for preparing fluorinated polypropyleneimine according to claim 4, characterized in that, The vacuum distillation process for removing water involves distilling the crude monomer product under reduced pressure until no more liquid drips out, heating to 80°C, observing for 20 minutes to ensure no nitrile distillate is released, heating to 100°C, discarding the first 2 mL of liquid, changing the bottle, heating to 120°C, and collecting the pure fraction.

7. The method for preparing fluorinated polypropyleneimine according to claim 2, characterized in that, The solvent mentioned in step B includes acetonitrile, chlorobenzene, or dichlorobenzene; the benign solvent includes dichloromethane, ethyl acetate, or ethanol; and the rotary evaporation temperature is 30°C to 70°C.

8. The method for preparing fluorinated polypropyleneimine according to claim 2, characterized in that, In step C, the hydrochloric acid concentration is 6-12 mol / L; the reaction temperature is 60-100℃; the reaction time is 48-96 h; and the precipitation solvent includes one or more of methanol, ethanol, diethyl ether, and acetone.

9. The use of the fluorinated polypropyleneimine according to claim 1 in the preparation of antibacterial agents.

Images