A polypeptide compound coupled with near-infrared photosensitizer, a preparation method and application in photodynamic antibiosis

Abstract

This invention belongs to the field of biomedical technology, and discloses a polypeptide compound coupled with a near-infrared photosensitizer, its preparation method, and its application in photodynamic antibacterial activity. The invention obtains the desired polypeptide through solid-phase synthesis and then chemically synthesizes it with a photosensitizing dye to obtain the coupled compound. This compound exhibits good reactive oxygen species production capacity after light irradiation and demonstrates excellent bactericidal activity against clinically isolated multidrug-resistant bacteria. It also exhibits no significant hemolytic activity, low toxicity, and good photodynamic therapeutic effects in animals.

Description

Technical Field

[0001] This invention belongs to the field of biomedical technology, specifically relating to a polypeptide compound coupled with a near-infrared photosensitizer, its preparation method, and its application in photodynamic antibacterial activity. Background Technology

[0002] In recent years, bacterial resistance to antibiotics has become a major global public health crisis. Since the advent of penicillin, the overuse and misuse of antibiotics have led to the emergence and spread of drug-resistant strains, far outpacing the development of new antibiotics. The emergence and prevalence of multidrug-resistant bacteria, in particular, have rendered many previously effective antibiotic treatments ineffective, resulting in prolonged illness, soaring treatment costs, and increased mortality rates. Clinically isolated multidrug-resistant bacteria, such as methicillin-resistant Staphylococcus aureus (MRSA) and drug-resistant Acinetobacter baumannii (CRBV), have become major pathogens of nosocomial infections, posing a deadly threat to immunocompromised patients, critically ill patients, and surgical patients. These strains evade antibiotics through various mechanisms, including producing drug-inactivating enzymes, altering drug targets, reducing cell membrane permeability, and activating efflux pump systems. Therefore, developing novel antibacterial strategies unaffected by traditional resistance mechanisms is urgently needed.

[0003] To address the challenge of drug-resistant bacteria, antimicrobial peptides, as natural host defense molecules, have attracted widespread attention. Unlike traditional antibiotics, antimicrobial peptides typically destroy the integrity of bacterial cell membranes through physicochemical processes, creating pores that allow cell contents to leak out and rapidly kill bacteria.

[0004] Furthermore, photodynamic therapy has become a hot topic in antibacterial technology research in recent years. Its mechanism of action is as follows: under irradiation with light of a specific wavelength, a photosensitizer is activated, converting oxygen molecules in the environment into highly cytotoxic reactive oxygen species (ROS). These ROS can indiscriminately attack various key biomolecules in bacteria, such as lipids, proteins, and nucleic acids, causing irreversible oxidative damage and leading to bacterial death. However, traditional small-molecule photosensitizers also face challenges in antibacterial applications, such as a lack of targeting and poor penetration into Gram-negative bacteria protected by both inner and outer membrane structures.

[0005] Peptide-coupled photosensitizer compounds are conjugates obtained by chemically linking peptides with specific biological functions to photosensitizer molecules. The combination of the peptide's own bacterial membrane-lytic activity and photodynamic oxidative killing effect is of great significance for the synergistic bactericidal effect against multidrug-resistant bacteria. Summary of the Invention

[0006] To overcome the shortcomings of the existing technology, the present invention provides the following technical solution: A polypeptide compound coupled with a near-infrared photosensitizer has the following structural formula: .

[0007] Furthermore, the peptide compound coupled with the near-infrared photosensitizer is prepared by reacting the peptide compound GGGENIKKILSKIKKLLK-NH2 with the photosensitizer PS. The structural formula of the photosensitizer PS is as follows: .

[0008] Among them, the polypeptide compound is obtained by a series of modifications of frog skin antimicrobial peptides, as detailed in patent application CN120737159A Fatty acid modified nano antimicrobial peptides and their preparation methods and applications.

[0009] A method for preparing a polypeptide compound coupled with a near-infrared photosensitizer involves weighing 120-140 mg of 1-hydroxybenzotriazole (HOBT) into a centrifuge tube, adding 8-10 mL of N,N-dimethylformamide (DMF) to dissolve it, weighing 200-250 mg of the photosensitizer and dissolving it in the same solution, adding 200-250 mg of the polypeptide sequence GGGENIKKILSKIKKLLK-NH2, and adding 0.15-0.2 mL of N,N-diisopropylcarbodiimide (DIC) for overnight reaction. After the reaction is complete, the reaction solution is drained, the resin is washed several times with DMF, transferred out and dried to constant weight, and then the resin is cleaved. The cleavage reagent is added to the resin with stirring, and the reaction is carried out after the system temperature stabilizes. After the reaction is complete, the lysate is filtered out, precipitated with ice-cold diethyl ether, the precipitate is filtered out and washed several times with ice-cold diethyl ether, dried under reduced pressure at room temperature, and the crude solid product is purified by RP-HPLC.

[0010] Furthermore, the reaction temperature after adding the resin is 25~30℃, and the reaction is stirred for 2~4 hours.

[0011] Furthermore, the washing process involves 3 to 5 cycles of DMF washing and ice-cold ether washing.

[0012] Furthermore, the polypeptide sequence GGGENIKKILSKIKKLLK-NH2 was synthesized using a solid-phase synthesis method. Following the polypeptide sequence, amino acids were sequentially condensed from the carboxyl terminus to the amino terminus and linked to the 18th amino acid. The polypeptide was synthesized using SPPS solid-phase synthesis technology, and finally formed into a polypeptide resin, which was then deprotected.

[0013] The application of a polypeptide compound coupled with a near-infrared photosensitizer in photodynamic antibacterial activity, mainly against multidrug-resistant strains from the First Affiliated Hospital of Dalian Medical University, including multidrug-resistant Gram-positive and multidrug-resistant Gram-negative bacteria.

[0014] Furthermore, multidrug-resistant Gram-positive bacteria include methicillin-resistant Staphylococcus aureus (MRSA) and methicillin-resistant Staphylococcus epidermidis.

[0015] Furthermore, multidrug-resistant Gram-negative bacteria include drug-resistant Acinetobacter baumannii and drug-resistant Klebsiella pneumoniae.

[0016] Compared with the prior art, the beneficial effects of the present invention include: This invention cleverly combines the antibacterial mechanism of antimicrobial peptides with the photodynamic antibacterial effect of photosensitizers by covalently coupling antimicrobial peptides with photosensitizers, achieving highly efficient antibacterial effects against a variety of clinically isolated multidrug-resistant bacteria. It has advantages such as convenient synthesis, strong bactericidal activity, and low toxicity, and has broad application prospects.

[0017] The polypeptide-coupled photosensitizer compound provided by this invention has a high efficiency in generating reactive oxygen species (ROS), exhibits good broad-spectrum antibacterial activity against a variety of clinically isolated multidrug-resistant bacteria, and has low toxicity, showing broad application prospects in photodynamic sterilization. Attached Figure Description

[0018] Figure 1 The normalized UV-Vis and fluorescence spectra of the compounds are shown. Figure 2 The superoxide anion (O2) of the compound –• (a) The fluorescence spectrum of DHR123 after treatment with the coupling compound at different illumination times, (b) The fluorescence spectrum of DHR123 after treatment with the photosensitizer at different illumination times, and (c) The ratio of the fluorescence intensity of DHR123 after treatment with different illumination times to that of the unilluminated group. Figure 3 The singlet oxygen of the compound ( 1 O2 generation capacity, (a) is the absorption spectrum of ABDA after treatment with coupling compound under different light exposure time, (b) is the absorption spectrum of ABDA after treatment with photosensitizer under different light exposure time, (c) is the ratio of the absorbance value of ABDA after treatment with different light exposure time at 378 nm to that of the unexposed group. Figure 4 To demonstrate the antibacterial activity of the compounds against drug-resistant Acinetobacter baumannii, (a) shows bacterial solid plates of MRAB after different treatment groups, (b) shows the bacterial survival rate after treatment with different concentrations of peptides, (c) shows the bacterial survival rate after treatment with different concentrations of photosensitizers, (d) shows the bacterial survival rate after treatment with different concentrations of photosensitizers plus light, (e) shows the bacterial survival rate after treatment with different concentrations of conjugated compounds, and (f) shows the bacterial survival rate after treatment with different concentrations of conjugated compounds plus light. Figure 5To demonstrate the antibacterial activity of the compounds against drug-resistant Klebsiella pneumoniae, (a) shows bacterial solid plate images of MRKP after different treatment groups, (b) shows the bacterial survival rate after treatment with different concentrations of peptides, (c) shows the bacterial survival rate after treatment with different concentrations of photosensitizers, (d) shows the bacterial survival rate after treatment with different concentrations of photosensitizers plus light, (e) shows the bacterial survival rate after treatment with different concentrations of conjugate compounds, and (f) shows the bacterial survival rate after treatment with different concentrations of conjugate compounds plus light. Figure 6 To demonstrate the antibacterial activity of the compounds against methicillin-resistant Staphylococcus aureus (MRSA), (a) shows bacterial solid plate images of MRSA after different treatment groups, (b) shows the bacterial survival rate after treatment with different concentrations of peptides, (c) shows the bacterial survival rate after treatment with different concentrations of photosensitizers, (d) shows the bacterial survival rate after treatment with different concentrations of photosensitizers plus light, (e) shows the bacterial survival rate after treatment with different concentrations of conjugate compounds, and (f) shows the bacterial survival rate after treatment with different concentrations of conjugate compounds plus light. Figure 7 To demonstrate the antibacterial activity of the compounds against drug-resistant Staphylococcus epidermidis, (a) shows bacterial solid plate images on MRSE after different treatment groups; (b) shows the bacterial survival rate after treatment with different concentrations of peptides; (c) shows the bacterial survival rate after treatment with different concentrations of photosensitizers; (d) shows the bacterial survival rate after treatment with different concentrations of photosensitizers plus light; (e) shows the bacterial survival rate after treatment with different concentrations of conjugated compounds; and (f) shows the bacterial survival rate after treatment with different concentrations of conjugated compounds plus light. Figure 8 The compound exhibits in vitro hemolytic activity; Figure 9 The cytotoxicity of the compounds is shown in (a) for the phototoxicity and dark toxicity of different concentrations of the conjugated compounds on RAW264.7 cells, and (b) for the phototoxicity and dark toxicity of different concentrations of the conjugated compounds on HEK293T cells. Figure 10 The values ​​are: (a) the effect of photosensitizers and conjugates plus light on the ROS levels in MRAB and MRKP bacteria, and (b) the effect of photosensitizers and conjugates plus light on the ROS levels in MRSA and MRSE bacteria. Figure 11 The effect of compounds on bacterial morphology under SEM; Figure 12 The photodynamic therapy of the conjugated compound on MRAB-infected wax moth larvae is shown in (a) for the effect of the conjugated compound on the survival rate of wax moth larvae at different time points after MRAB infection, and (b) for the melanization status of larvae after different treatment groups. Figure 13Photodynamic therapy of conjugated compounds on acute pneumonia in MRAB-infected mice: (a) is a schematic diagram of the mouse model; (b) shows the bacterial load in the lungs of mice in different treatment groups; and (c) shows bacterial plates after homogenization of lung tissue in different treatment groups. Detailed Implementation

[0019] The following embodiments will enable those skilled in the art to better understand the present invention. The descriptions in the embodiments are for illustrative purposes only and are not intended to limit the invention in any way.

[0020] Example 1: Preparation of a peptide-photosensitizer conjugate A solid-phase synthesis method was employed, sequentially condensing amino acids from the carboxyl terminus to the amino terminus of the peptide sequence up to the 18th amino acid (GGGENIKKILSKIKKLLK-NH2). The peptide was synthesized using SPPS solid-phase synthesis technology, ultimately forming a peptide resin, which was then deprotected and placed in a reaction flask. 136 mg of 1-hydroxybenzotriazole (HOBT) was weighed into a centrifuge tube and dissolved in 8 mL of N,N-dimethylformamide (DMF). 250 mg of photosensitizer was also weighed and dissolved in the same solution. This mixture was added to the reaction flask along with 0.2 mL of N,N-diisopropylcarbodiimide (DIC) and reacted overnight. After the reaction was completed, the reaction solution was drained, and the resin was washed three times with 20 mL of DMF. The resin was then transferred out and dried to a constant weight. The resin was then pyrolyzed. The pyrolysis reagent was added to the resin with stirring. After the system temperature stabilized, the temperature was controlled at 25~30℃ and the reaction was stirred for 2.5 hours. The pyrolysis solution was filtered out and precipitated with 5 times the liquid volume of ice-cold diethyl ether. The precipitate was filtered out and washed three times with 3 times the liquid volume of ice-cold diethyl ether. The precipitate was then dried under reduced pressure at room temperature to obtain a solid crude product, which was then purified by RP-HPLC.

[0021] During purification, the peak value of the target product was detected by reverse high-performance liquid chromatography (RP-HPLC) to ensure that the purity of the target product was higher than 95%. The qualified main peak was collected and then freeze-dried under reduced pressure to obtain a product with a purity higher than 95%. Finally, the molecular weight and purity were identified using ESI-MS, and the relative molecular mass of the conjugate was determined to be 2383.05 by ESI-MS.

[0022] Example 2: Absorption and fluorescence emission spectra of compound PPC The compound was dissolved in deionized water to prepare a mother liquor (1 mM). The mother liquor was diluted with deionized water to a concentration of 10 μM, and its absorption spectrum was obtained by scanning under a UV-Vis absorption spectrometer. The maximum absorption wavelength was measured, and its fluorescence spectrum at the excitation wavelength of the maximum absorption wavelength was measured under a fluorescence spectrometer. Figure 1As shown, the compound's maximum absorption wavelength is around 660 nm, and its maximum fluorescence emission wavelength is around 710 nm. Therefore, a 660 nm light source was used for subsequent photodynamic antibacterial experiments.

[0023] Example 3: Compound superoxide anion (O2) –• Measurement of production capacity Using DHR 123 as O2 –• An indicator of production efficiency was used. A mixture of 10 μM DHR 123 and the compound was irradiated (660 nm) for different times (0, 1, 2, 3, 5, 10, and 20 min), and the fluorescence spectra of each sample were measured (excitation wavelength: 500 nm, emission band: 510 ~ 650 nm). The degree of fluorescence enhancement was used to assess O2 production efficiency. –• The generation efficiency. For example... Figure 2 As shown, the fluorescence intensity of the compound-treated group increased with increasing illumination time, and the fluorescence intensity of the indicator was higher than that of the photosensitizer under 20 min illumination conditions. This indicates that the superoxide anion generation efficiency is improved after the photosensitizer is coupled with the peptide compared to the photosensitizer itself.

[0024] Example 4 Compound Singlet Oxygen ( 1 Measurement of O2 production capacity Using ABDA as 1 An indicator of O2 production efficiency was used. A mixed solution of ABDA and a compound (containing 50 μM ABDA and 10 μM of the compound) was irradiated at 660 nm for different times (0, 1, 2, 3, 5, and 10 min), and the UV absorption spectra (300–500 nm) of each sample were measured. The degree of absorbance reduction at 378 nm was compared to assess the efficiency. 1 The efficiency of O2 generation. For example... Figure 3 As shown, in the mixed solution of ABDA and the compound, the absorbance of ABDA at 378 nm gradually decreased with increasing illumination time, indicating that its efficiency was superior to that of the photosensitizer. This suggests that the singlet oxygen generation efficiency of the photosensitizer is improved after coupling with the peptide compared to the photosensitizer itself.

[0025] Example 5 Evaluation of the in vitro antibacterial activity of the compound Experiments were performed using clinically isolated multidrug-resistant bacteria, including Gram-positive bacteria (including methicillin-resistant Staphylococcus aureus and methicillin-resistant Staphylococcus epidermidis) and Gram-negative bacteria (including methicillin-resistant Acinetobacter baumannii and methicillin-resistant Klebsiella pneumoniae). Bacteria cultured overnight at 37°C to the logarithmic growth phase were diluted to OD0.05. 600 =10 -3Reserved. Then, prepare samples with equal volumes of the compound for antibacterial activity testing. Non-light-treated group: samples were incubated at 37℃ in the dark for 2 h; Light-treated group: samples were incubated at 37℃ in the dark for 30 min, then irradiated with 660 nm light for 10 min, and then incubated at 37℃ in the dark for 80 min. After completion, centrifuge at 3000 rpm / min for 5 min, discard the supernatant, wash three times with PBS and resuspend, take 100 μL and drop onto a solid plate and spread evenly. Incubate each solid plate at 37℃ for 18-24 h, and calculate the number of viable colony-forming units (CFU) in each group using the viable cell count method. Figure 4-7 This study presents the in vitro antibacterial activity of compounds PPC (light-exposed and non-light-exposed groups), photosensitizer PS (light-exposed and non-light-exposed groups), and antimicrobial peptides against different drug-resistant bacteria. The results showed that the conjugated compounds exhibited stronger photodynamic antibacterial activity compared to the other groups. The peptides showed no significant antibacterial activity against drug-resistant Klebsiella pneumoniae and methicillin-resistant Staphylococcus aureus, while the conjugated compounds exhibited broad-spectrum antibacterial activity, achieving bactericidal rates exceeding 95% against drug-resistant Acinetobacter baumannii, drug-resistant Klebsiella pneumoniae, methicillin-resistant Staphylococcus aureus, and drug-resistant Staphylococcus epidermidis at concentrations of 0.625, 1.25, 2.5, and 0.625 μM, respectively.

[0026] Example 6 In vitro hemolytic activity Fresh human blood was collected in an anticoagulant tube and diluted with 0.9% saline to a 2% red blood cell suspension for later use; the compound was prepared to a concentration of 0.625 to 80. To determine the final concentration of M, mix 500 μL of the compound solution with an equal volume of 500 μL of human red blood cells. Incubate the sample at 37°C for 1 h. After incubation, centrifuge at 1500 rpm for 10 min, collect the supernatant serum, and add it to a 96-well plate. Measure the absorbance at 414 nm in each well using a microplate reader. Use 0.9% physiological saline as a negative control and 0.1% Triton X-100 as a positive control. Calculate the hemolysis rate using the following formula: Hemolysis rate (%) = (Experimental group – Negative control) / (Positive control – Negative control) × 100%. Figure 8 As shown, the hemolysis test results indicate that the compound is safe for in vivo treatment at concentrations below 40%. The hemolysis rate is very low (less than 5%) at M concentrations of 80%. The hemolysis rate was still low at time M (5.66%).

[0027] Example 7 In vitro cytotoxicity test of the compound The cytotoxicity of the compounds against RAW 264.7 and HEK293T cells was evaluated using a CCK-8 assay kit. Cells were cultured at 5 × 10⁶ cells per well. 3Cells were seeded at a density of [number] cells and cultured overnight at 37°C with 5% CO2. Cells were then exposed to different concentrations (0.625 to 20 [units of concentration]). After 24 h of incubation with the compound (M), CCK-8 solution was added to each well. After incubation at 37°C for 2 h, absorbance was measured at 450 nm using a microplate reader, and cell viability was calculated. For the phototoxicity group, cells were treated with 660 nm LED light for 10 min after 2 h of incubation with the compound. Figure 9 As shown, after 24 h of treatment, the concentration of the compound was 10. When the molecular weight (M) is below a certain level, the viability of both cell types is above 80%.

[0028] Example 8: Determination of total ROS levels in bacterial cells Intracellular ROS production was detected using DCFH-DA. Bacterial suspensions were mixed with water to a final concentration of 5... Mix MPS or PPC for 30 min, then incubate with 10 μM DCFH-DA for 1 h. Irradiate the mixture at 660 nm for 10 min. Intracellular ROS are detected by measuring the fluorescence intensity of DCFH at 525 nm. Figure 10 As shown, the level of ROS in bacterial cells increased significantly after treatment with the compound.

[0029] Example 9 Morphology of bacteria treated with the compound under SEM Bacterial suspensions were incubated in the dark at 37°C for 30 min with PBS, antimicrobial peptides, photosensitizers, or conjugated compounds (final concentration 2.5 μM). The light-treated group was incubated for 10 min followed by 80 min of further incubation. Subsequently, the bacterial cells were washed three times with PBS and fixed overnight at 4°C with 2.5% glutaraldehyde. The bacterial pellet was then dehydrated sequentially with 30%, 50%, 70%, 80%, 90%, and 100% ethanol, 5 min at a time. Afterward, the bacteria were plated on silica gel and air-dried for SEM observation. Figure 11 As shown, after light treatment, the coupled compound caused severe morphological deformation in Gram-positive bacteria (including methicillin-resistant Staphylococcus aureus and methicillin-resistant Staphylococcus epidermidis) and Gram-negative bacteria (including methicillin-resistant Acinetobacter baumannii and methicillin-resistant Klebsiella pneumoniae), accompanied by significant rupture of the bacterial membrane. Under light, the morphology of Gram-positive bacteria treated with the photosensitizer was deformed, while the morphology of Gram-negative bacteria remained intact. This indicates that due to the robust outer membrane structure of Gram-negative bacteria, the reactive oxygen species generated by the photosensitizer are unlikely to disrupt their structure.

[0030] Example 10: Photodynamic therapy of drug-resistant Acinetobacter baumannii-infected wax borer larvae by conjugated compounds The therapeutic effect of conjugates following infection with drug-resistant Acinetobacter baumannii was tested using wax moth larvae. Ten healthy larvae were randomly selected from each group for the experiment. (The last part, "10," appears to be an unrelated fragment and is left untranslated.) L-resistant Acinetobacter baumannii suspension (1×10) 5 Inject CFU / mL into the left hind leg of the larvae and maintain in darkness at 37°C. After 2 hours, treat with the conjugate, photosensitizer, and peptide (10 CFU / mL). L, 1.25 M) and subjected to light treatment. Survival phenotypic characteristics, including activity, degree of melanization, and survival status, were monitored every 24 hours for 72 hours. The control group consisted of larvae injected with water. Figure 12 As shown in (a), all larvae in the infected group died within 24 hours, while the conjugate showed a good therapeutic effect on wax moths after light exposure, with a survival rate of 80% within 72 hours of bacterial infection, while the survival rates of wax moths in the peptide treatment group and the photosensitizer light exposure group were 40% and 30%, respectively. Figure 12 (b) shows that the larvae in the bacterial infection group showed significant melanization, while the conjugated compound treatment group achieved good treatment results and showed no significant melanization.

[0031] Example 11 Photodynamic therapy of conjugated compounds on acute pneumonia in mice infected with drug-resistant Acinetobacter baumannii Male Balb / c mice (6 weeks old, weighing approximately 20 g, n=6) were anesthetized and inoculated intratracheally with MRAB (210). 9 CFU / mL, 50 μL). Then, for three consecutive days, different drugs (100 CFU / mL, 50 μL) were administered via tail vein. M, 100 L). In the light irradiation group, the chest region of the mice was shaved and irradiated with a 660 nm laser for 10 min. Lung tissue was collected and analyzed on day 4. Results are as follows. Figure 13 As shown, the bacterial load in the lungs of mice in the conjugate-illuminated group was significantly lower than that in the infected group, and the number of bacteria was lower than that in the peptide and conjugate-non-illuminated groups, and comparable to that in the gentamicin positive control, demonstrating a good therapeutic effect.

[0032] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. A polypeptide compound conjugated to a near infrared photosensitizer, characterized in that, The structure is as follows: 。 2. The polypeptide compound conjugated near-infrared photosensitizer according to claim 1, characterized in that, The peptide compound coupled with the near-infrared photosensitizer is prepared by reacting the peptide compound GGGENIKKILSKIKKLLK-NH2 with the photosensitizer PS. The structural formula of the photosensitizer PS is as follows: 。 3. A method for preparing a polypeptide compound conjugated with a near infrared photosensitizer, characterized by, Weigh 120-140 mg of 1-hydroxybenzotriazole (HOBT) into a centrifuge tube, add 8-10 mL of N,N-dimethylformamide (DMF) to dissolve it, add 200-250 mg of the photosensitizer as described in claim 2 to dissolve it, then add 200-250 mg of the polypeptide sequence GGGENIKKILSKIKKLLK-NH2, and add 0.15-0.2 mL of N,N-diisopropylcarbodiimide (DIC) to react overnight. After the reaction is complete, drain the reaction solution, wash the resin several times with DMF, transfer it out and dry it to constant weight, then lyse the resin. Add the lysis reagent to the resin with stirring, and wait for the system temperature to stabilize before reacting. After the reaction is complete, filter out the lysate, precipitate it with ice-cold ether, filter out the precipitate and wash it several times with ice-cold ether, dry it under reduced pressure at room temperature to obtain a solid crude product, which is then purified by RP-HPLC.

4. The method of claim 3, wherein the method is characterized by, The reaction temperature after adding the resin is 25~30℃, and the reaction is stirred for 2~4 hours.

5. The method for preparing the polypeptide compound coupled with a near-infrared photosensitizer according to claim 3, characterized in that, The washing process involves 3 to 5 cycles of DMF washing and ice-cold ether washing.

6. The method for preparing the polypeptide compound coupled with a near-infrared photosensitizer according to claim 3, characterized in that, The polypeptide sequence GGGENIKKILSKIKKLLK-NH2 was synthesized using a solid-phase synthesis method. Following the polypeptide sequence, amino acids were sequentially condensed from the carboxyl terminus to the amino terminus and linked to the 18th amino acid. The polypeptide was synthesized using SPPS solid-phase synthesis technology, and finally formed into a polypeptide resin, which was then deprotected.

7. The application of a polypeptide compound coupled with a near-infrared photosensitizer as described in any one of claims 1-2 in photodynamic antibacterial activity, characterized in that, The bacteria are multidrug-resistant strains, including multidrug-resistant Gram-positive bacteria and multidrug-resistant Gram-negative bacteria.

8. The application of the polypeptide compound coupled with a near-infrared photosensitizer as described in claim 7 in photodynamic antibacterial activity, characterized in that, Multidrug-resistant Gram-positive bacteria include methicillin-resistant Staphylococcus aureus (MRSA) and methicillin-resistant Staphylococcus epidermidis (MRSA).

9. The application of the polypeptide compound coupled with a near-infrared photosensitizer as described in claim 7 in photodynamic antibacterial activity, characterized in that, Multidrug-resistant Gram-negative bacteria include drug-resistant Acinetobacter baumannii and drug-resistant Klebsiella pneumoniae.

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