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Journal of Nanobiotechnology logoLink to Journal of Nanobiotechnology
. 2024 Nov 15;22:713. doi: 10.1186/s12951-024-02985-5

Metal-phenolic nanoparticles enhance low temperature photothermal therapy for bacterial biofilm in superficial infections

Yang Ye 2,#, Qinqin Zheng 1,#, Ziqi Wang 1, Shanshan Wang 1, Zhouyu Lu 2, Qiang Chu 2, Yong Liu 3, Ke Yao 2, Bing Wei 3,✉, Haijie Han 2,✉, Hongping Chen 1, Xiangchun Zhang 1,✉
PMCID: PMC11566565  PMID: 39543628

Abstract

Bacterial infections, especially induced by multidrug-resistant pathogens, have become a significant global health concern. In the infected tissues, biofilms not only serve as a source of nutrients but also act as protective barriers that impede antibiotic penetration. Herein, we developed tea polyphenols epigallocatechin gallate (EGCG) Au nanoparticles (E-Au NPs) through direct one-step self-assembly methods by EGCG chelating with Au ions to eradicate antibiotic-resistant bacteria methicillin-resistant Staphylococcus aureus (MRSA) and prevent the formation of biofilm under near-infrared (NIR) irradiation. The outstanding antibacterial effect involved in mild photothermal therapy, reactive oxygen species production, pathogenicity-related genes regulation, and quinoprotein formation that were specific to the polyphenol-based NPs. The excellent antibacterial and anti-inflammatory therapeutic efficacy of E-Au NPs was validated and topically applied in murine MRSA-infected skin wounds and keratitis model in vivo to kill bacteria, reduce the inflammation response and promote wound healing. Furthermore, the ophthalmic and systemic biosafety profiles were thoroughly evaluated while no significant side effects were revealed achieving a balance between high-efficiency antibacterial properties and biocompatibility. This study provides an effective therapeutic agent of metal-phenolic materials for superficial tissue infection with favorable prognosis and potential in clinical translation.

Graphical abstract

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Supplementary Information

The online version contains supplementary material available at 10.1186/s12951-024-02985-5.

Keywords: Polyphenols, Biofilm infections, Metal-phenolic nanoparticles, Mild photothermal therapy, Quinoprotein

Introduction

Bacterial infections have become a significant global health concern, leading to substantial morbidity and mortality [1]. The rise of multidrug-resistant pathogens (e.g., methicillin-resistant Staphylococcus aureus (MRSA)) has become a widespread issue, undermining the effectiveness of treatments due to the overuse and misuse of antimicrobials [2, 3]. The tolerance and resistance to antimicrobials are further aggravated by the formation of bacterial biofilm, which is the three-dimensional structure of extracellular matrix and microorganisms [4]. As protective barriers, biofilms could impede antibiotic penetration, resist external environment changes and provide nutrients, making it challenging to eradicate bacterial infection during clinical treatment, especially in ulcer wounds [5, 6]. Hence, there is an urgent need to explore alternative antibacterial strategies especially for drug-resistant pathogens and its related biofilms in the management of clinical infections, such as skin wounds, keratitis, and pneumonia.

Organic small molecule antibiotics, such as Daptomycin and Delamanid, have made great contributions to the treatment of bacterial infections, but they are not effective against biofilms [7, 8]. Nanomaterials, whether acting as inherent therapeutics or drug nanocarriers, offer potent antimicrobial capabilities through novel mechanisms that do not rely on bacterial natural defenses [9–13]. These nanomaterials are considered promising antimicrobial biofilms and have wide applications in various fields due to their unique physical, chemical, and biological properties, such as size, shape, and surface chemistry [14–18]. For instance, metal nanoparticles (NPs) exhibit the potent ability to eradicate bacterial biofilms through damaging cell integrity, generating reactive oxygen species (ROS), preventing DNA replication. Despite concerns about the safety of metal NPs, researchers are exploring methods like additional external stimuli (e.g., phototherapy, near-infrared radiation) to enhance antibacterial effects, reduce metal NPs concentration, and improve their biological safety [19–21]. Phototherapy, including photothermal therapy (PTT), photodynamic therapy (PDT), and photocatalytic therapy (PCT), shows the promise in combating antimicrobial and anti-biofilm infections, especially in superficial tissues [22, 23]. Photothermal agents can effectively kill bacteria by denaturing proteins and rupturing membranes by transforming light energy into heat [24, 25]. However, hyperthermia therapy may necessitate a high-intensity near-infrared (NIR) laser and nonspecifically damage normal surrounding tissues through heat diffusion [26, 27]. Mild-temperature PTT, on the other hand, can modulate specific protein activities without causing irreversible damage, making it more suitable for ophthalmic applications [28, 29]. Moreover, PDT is a minimally invasive clinical treatment that employs photosensitizers to generate ROS and effectively damage bacterial cells and their biofilm, reducing the risk of resistance development [30–32]. Additionally, the selection of a suitable functional ligand to repair normal tissue damage caused by phototherapy is an ideal strategy to address the side effects.

Polyphenols, such as epigallocatechin gallate (EGCG), are the natural plant secondary metabolites and known for their potent antioxidant properties and play an important role in medical applications due to their anti-inflammatory, anti-tumor and antibacterial abilities [33]. With the development and application of synthetic method, EGCG-based nanoparticles were widely used in medical fields, especially in antibacterial application. As a major polyphenol in tea, the highly reactive phenolic hydroxyl group could readily bind to metal ions, amino acid and other antibacterial components to exhibit antibacterial activity or act as drug delivery system [34–36]. This property has been utilized in the development of various biological nanomaterials for biological effects studies, such as anti-biofilm infection. Moreover, polyphenols have demonstrated antioxidant capacity, which can help mitigate tissue damage induced by phototherapy. Therefore, we propose that utilizing polyphenols as ligands to create novel metal-phenolic NPs could synergistic against biofilm infections and safeguard normal tissues during mild-temperature stimuli [37].

Herein, epigallocatechin gallate (EGCG), a major polyphenol in tea, was selected as the ligand to chelate with Au ions forming EGCG-Au NPs (E-Au NPs) through direct one-step self-assembly methods in aqueous solutions without templating or seeding agents. These E-Au NPs exhibited in vitro antibacterial properties to eradicate antibiotic-resistant bacteria MRSA and antibiofilm effects to prevent biofilm formation under NIR irradiation. The outstanding antibacterial and anti-inflammatory therapeutic efficacy of E-Au NPs was validated in murine MRSA-infected skin wounds and keratitis model in vivo. Systematic studies revealed that the antibacterial mechanisms of E-Au NPs involved mild PTT, ROS production, pathogenicity-related genes regulation, and quinoprotein formation, which is an antibacterial pathway specific to the polyphenol-based NPs. Furthermore, the ophthalmic and systemic biosafety profiles were thoroughly evaluated, revealing no significant side effects. The antibacterial PTT strategy utilizing high biocompatibility metal-phenolic NPs demonstrated effective therapeutic outcomes in superficial tissue infection models, highlighting the potential clinical applications of metal-phenolic materials (Scheme 1).

Scheme 1.

Scheme 1

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The schematic illustration of antibacterial and antibiofilm treatment of E-Au NPs. E-Au NPs were developed through direct one-step self-assembly methods. The antibacterial and anti-inflammatory therapeutic efficacy was verified in MRSA-infected skin wounds and keratitis. The outstanding antibacterial effect involved in mild photothermal therapy, reactive oxygen species production, pathogenicity-related genes regulation, and quinoprotein formation. 

Methods

Synthesis of E-Au NPs 

Briefly, a volume of 0.2 mL EGCG aqueous solution (20 mM) was added into a 5 mL vial containing 1616 uL of water at 25°C under vigorous stirring (1000 rpm). Then, 24 µL NaOH aqueous solution was added to adjust the pH of the EGCG solution. After that, 160 µL HAuCl4 (25 mM) volume was slowly dripped into the mixed solution. Subsequently, the reactants were vigorously stirred for 5 min at room temperature. Finally, the obtained sample was transferred into the Ultracel-10 K centrifugal filter to be centrifuged at 8000 rpm for 15 min using buffer solution (NaOH solution, pH = 9) several times, and the inner tube sample was collected and stored.

Quantification of E-Au NPs

ICP-MS analysis systems (Thermo XSERIES 2, USA) were utilized to analyze the purified E-Au NPs concentration. Initially, 5 µL of E-Au NPs was digested overnight with 3 mL of aqua regia. The resulting reagent mixture was evaporated to approximately 0.1 mL using the BHW-09 C Heating Block system at 140 °C. Subsequently, the sample was diluted to the desired concentration with a mixed acid solution containing 2% HNO3 and 1% HCl. Various concentrations of Au standard solutions (0.5, 1, 5, 10, and 50 ng/mL) were quantified to establish a standard curve. The ICP-MS test revealed a yield of 58.14% for E-Au NPs. The standard curve, with a linear regression coefficient of 0.99997, is depicted in Fig. S1.

Characterization of E-Au NPs

The UV-visible absorption spectra of E-Au NPs were recorded with a UV-1800 spectrophotometer (Shimadzu, Japan). The transmission electron microscope (TEM, JEM-2100 F, JEOL, Japan) was employed to observe the morphological characterization of E-Au NPs. The infrared spectrogram of E-Au NPs was characterized with an infrared spectrometer (Nicolet IS10, Thermo, USA). Elemental analysis was obtained with an X-ray photoelectron spectrometer (ESCALAB 250Xi, Thermo, USA). The size distributions and zeta potential were measured with the NanoPlus DLS nanoparticle size and zeta potential analyzer (90Plus Zeta, NanoBrook, USA). The XRD pattern were obtained by X-ray diffractometry (D8 ADVANCE X, Bruker, Germany).

Photothermal effect of E-Au NPs

To determine the photothermal conversion properties of E-Au NPs, three experiments were performed in this study. First, E-Au NPs (40 µL) in a 0.2 mL eppendorf tube with same concentrations (100 µg/mL) were irradiated at different power density (0.25, 0.5, 0.75, 1, and 1.5 W/cm2) with 808 nm Laser Light Source (VLSM-808-B, Connet Laser Technology Co., LTD, China) for 5 min, respectively. Second, a volume of 40 µL E-Au NPs with different concentrations (0, 25, 50, 100,150, and 200 µg/mL) were introduced in a tube and irradiated with an 808 nm NIR laser at a power density of 1 W/cm2 for 5 min, and infrared thermal images were simultaneously taken using an IR camera. Third, Heating − cooling cycles experiments were determined by using 200 µg/mL E-Au NPs under 808 nm irradiation (1 W/cm2).

In vitro antibacterial activity analysis

S. aureus, E. coli, and MRSA were selected to verify the in vitro antibacterial effects. Bacterial suspension was cultured at 37 °C for 24 h in the lysogeny broth (LB) medium and diluted to 2 × 106 CFU/mL. Subsequently, 200 µL of bacteria suspension were added into a 0.6 mL Eppendorf tube containing 200 µL of E-Au NPs with final concentration of 200 µg/mL. The mixed suspension was incubated at 37 °C for 30 min and was divided into a 0.6 mL tube at 50 µL per tube. The packaged samples were irradiated with NIR laser (1 W/cm2) for different times (0, 1, 2, 3, 4, and 5 min), respectively. Then bacterial suspension was diluted with liquid LB medium (1:104). Thereafter, 100 µL of the dilution was spread into agar plate. After incubation at 37 °C for different times (24 h for E. coli on LB plates, 48 h for MRSA, S. aureus on Mannitol Salt plates), the number of bacterial growth was recorded for calculating bacterial survival rate according to the formula:

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When irradiation time was 2.5 min, the number of bacterial growth was tested similarly at a series concentrations of E-Au NPs (0, 25, 50, 100, 150, and 200 µg/mL).

Antibiofilm activity

For the ability to prevent biofilm formation, 1 mL of MRSA suspension (1 × 107 CFU/mL) was added to the 24-well plate and incubated at 37 °C for 6 h. Then the medium was carefully removed and treated by LB (Control), Laser alone (808 nm, 1.0 W/cm2, 2.5 min), E-Au NPs (200 µg/mL), E-Au NPs plus laser (808 nm, 0.25 W/cm2, 2.5 min, 200 µg/mL). After 48 h, the planktonic MRSA was removed and carefully washed three times with PBS. The biofilm was stained for 15 min with crystal violet (10 mg/mL, 200 µL per well) and washed three times with PBS. In a separate experiment, MRSA was incubated in the confocal 6-well plate at 37 °C for 48 h with the same treatment. Then the biofilms were carefully washed three times with PBS and stained with SYTO 9 for 30 min. The confocal images were then taken using the SP8 LIGHTNING Confocal Microscope (Leica, Germany). As for antibiofilm activity for matured biofilm, the MRSA were cultured in LB for 48 h in advance to form biofilms and then treated by E-Au NPs plus laser (808 nm, 0.25 W/cm2, 2.5 min, 200 µg/mL) for 24 h. The ability was then assessed as above.

In vivo establishment and treatment of MRSA-infected skin wounds model

All the experiments on animals were accredited by the Institutional Ethics Committee and followed the requirements for the care and use of laboratory animals at Zhejiang University. Female C57BL/6 mice (6 weeks old) were chosen to evaluate in vivo skin wound antibacterial activity. A full-thickness circular skin wound with about 8 mm diameter was prepared on the back of the mouse using the scalpel under anesthesia and a total of 25 µL of MRSA suspension (1 × 107 CFU/mL) was inoculated into the wound area. The negative control group (Un-inf) was not inoculated with MRSA. After 24 h, the MRSA-infected mice were randomly divided into six groups (n = 5) and topically treated with 50 µL of PBS (Un-inf and PBS group), EGCG (200 µg/mL), EGCG plus laser (808 nm, 0.25 W/cm2, 5 min, 200 µg/mL), E-Au (200 µg/mL), E-Au NPs plus laser (808 nm, 0.25 W/cm2, 2.5 min, 200 µg/mL) on days 1 and 3. Then the healing process with different administrations was monitored for 8 days and wound size was measured through vernier calipers. After the experiment, tissues were collected for further LB-agar plate CFU counting, pathological histology, and immunohistochemistry analysis.

In vivo establishment and treatment of MRSA-infected keratitis model

Female C57BL/6 mice (6 weeks old) were chosen to evaluate in vivo keratitis antibacterial activity. The corneal epithelium of the mouse was removed and 25 µL of MRSA suspension (1 × 107 CFU/mL) was injected to the cornea. After 48 h incubation, the MRSA-infected keratitis models were established and randomly divided into four groups (n = 5) and topically treated with 25 µL PBS, Cefazolin sodium (200 µg/mL), E-Au (200 µg/mL), E-Au NPs plus laser (808 nm, 0.25 W/cm2, 2.5 min, 200 µg/mL) on days 2 and 4. Then the healing process and anterior segment images with different administrations were recorded with the slit lamp image system (6 6 VISION TECH Co., Ltd., YZ5T, China). The clinical grading scale was evaluated by three independent, masked observers as described in the previous study [20]. IOP was measured with Icare Tonometer (TonoLab, Finland) every four days as the average of three measurements for each eye. After the experiment, tissues were collected for further pathological histology and immunohistochemistry analysis.

Results and discussion

Synthesis and characterization of E-Au NPs

For synthesis of E-Au NPs, EGCG first self-assembled under alkaline conditions, followed by rapid EGCG-Au coordination with HAuCl4, completing the synthesis process almost instantaneously (Fig. 1A). Transmission electron microscopy (TEM) images revealed that the E-Au NPs were uniform and spherical, with an average size of 5.38 ± 0.86 nm (Fig. 1B and Fig. S2). Dynamic light scattering (DLS) analysis showed consistent size distribution of E-Au NPs in DI water, phosphate buffer solution (PBS), and Luria-Bertani (LB), indicating E-Au NPs had its good dispersibility. The particle sizes of E-Au NPs in various solutions were around 40 nm, more significant than the size observed via TEM, possibly due to the strong adhesion of NPs to the hydration surface (Fig. S3). Fourier transform infrared spectroscopy (FT-IR) revealed a blue-shift of the -OH absorption peak from 3432 cm-1 to 3420 cm-1 and a red-shift of the carbonyl (C = O) absorption peak from 1625 cm-1 to 1628 cm-1 in E-Au NPs comparison with EGCG (Fig. 1C). These changes suggest that carboxyl and hydroxyl groups likely played a role in the synthesis and stabilization of E-Au NPs. X-ray photoelectron spectroscopy (XPS) showed E-Au NPs contained characteristic peaks of O 1s, C 1s and Au 4f (Fig. S4). Precisely, in the Au 4f spectrum, peaks at 83.4 eV and 87.1 eV corresponded to the two states 4f7/2 and 4f5/2 of Au, indicating that the Au element in E-Au NPs contained both Au3+ and Au0 (Fig. 1D). This observation confirmed the formation of an Au-O bond between Au3+ and EGCG, which served as a critical aspect in the synthesis of E-Au NPs. The UV-vis spectra of E-Au NPs displayed a characteristic MPN ligand-to-metal charge-transfer band at approximately 530 nm, indicating a prevalent bis-state metal-phenolic coordination (Fig. 1E). The successful synthesis of E-Au NPs was further verified through X-ray Diffraction (XRD), revealing four additional broad peaks at 38.3°, 44.4°, 64.7°, and 77.6°, corresponding to the (111), (200), (220), and (311) planes of the Au lattice (JCPDS Card NO. 04–0784) (Fig. 1F).

Fig. 1.

Fig. 1

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Synthesis and characterization of E-Au nanoparticles. (A) Schematic illustration of synthetic process of E-Au NPs. (B) TEM image of E-Au NPs, scale bar = 2 nm. (C) FT-IR spectra of EGCG and E-Au NPs. (D) High-resolution XPS spectra of E-Au NPs. (E) UV–vis absorption spectra of EGCG and E-Au NPs. (F) XRD patterns of E-Au NPs. Thermal images (G) and corresponding temperature variation (H) of E-Au NPs with various concentrations (0–200 µg/mL) under 808 nm laser irradiation (1.0 W/cm2) for 5 min. (I) Five cycles of heating/cooling photothermal curves of the E-Au NPs.

The photothermal properties of E-Au NPs was then investigated by continually monitoring temperature fluctuations exposed to 808 nm NIR laser irradiation. As shown in Fig. 1G, the temperature change of E-Au NPs under 808 nm infrared laser irradiation for 5 min was recorded using an infrared camera. It was noted that E-Au NPs exhibited a concentration-dependent temperature increase when subjected to NIR irradiation at 1.0 W/cm2. The temperature difference (ΔT) of E-Au NPs was precisely quantified as 36.0 °C, whereas it only slightly increased 3.3 °C for water (Fig. 1H). Additionally, the temperature change presented a power-density-dependent photothermal performance (Fig. S5). A comparison was also made between the temperature increase of E-Au NPs and EGCG-Ag NPs irradiated for 5 min at 1.0 W/cm2 laser. The ΔT of EGCG-Ag NPs was measured at only 5.0 °C, whereas E-Au NPs exhibited a temperature increase of 25.1 °C. Furthermore, E-Au NPs displayed stable and repeatable heating capacity over five cycles of NIR irradiation on/off, indicating their potential for long-term photothermal applications (Fig. 1I).

In vitro antibacterial and antibiofilm activity of E-Au NPs

S. aureus, E. coli, and MRSA were selected to assess the antibacterial activity of E-Au NPs. First, the bacterial growth curves were monitored using the optical density at 600 nm (OD600) at various concentrations of E-Au NPs. All these three bacterial strains, including both Gram-positive and Gram-negative bacteria, were inhibited in a dose-dependent manner while E-Au NPs administration could not completely inhibit bacterial reproduction (Fig. 2A-C, Fig. S6). The antibacterial activity of E-Au NPs under NIR irradiation was evaluated by colony-forming units (CFUs) on LB-agar plates. The antibacterial effects for S. aureus and E. coli were significantly enhanced under NIR irradiation with the increase of E-Au NPs concentration or laser irradiation time (Figs. S7-S10). After treatment with 200 µg/mL E-Au NPs plus laser irradiation (808 nm, 1.0 W/cm2, 2.5 min), both Gram-positive and Gram-negative bacteria were almost eliminated and the survival rates were only 0.06% for S. aureus, 3.38% for MRSA, and 0.02% for E. coli, respectively (Fig. 2D-G, Fig. S8-S10). Notably, the E-Au NPs under NIR irradiation antibacterial strategy exhibited excellent antibacterial ability to MRSA, which was multidrug-resistant and highly pathogenic. These results suggested that E-Au NPs provided antibacterial efficacy to both Gram-positive and Gram-negative bacteria which could be further synergetic strengthened by laser irradiation. Besides, EGCG and Au3+ also exhibited certain antibacterial activity which could not completely eradicate the MRSA (Fig. S11).

Fig. 2.

Fig. 2

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In vitro antibacterial and antibiofilm activities of E-Au NPs. Growth curves of S. aureus (A), E. coli (B) and MRSA (C) upon incubation with E-Au NPs at different concentrations. The photographs (D) and survival rate (E) of MRSA treated with E-Au NPs plus laser at varied time (1.0 W/cm2, 200 µg/mL). The photographs (F) and survival rates (G) of MRSA treated with E-Au NPs (at varied concentrations of 0, 25, 50, 100, 150 and 200 µg/mL, 1.0 W/cm2, 2.5 min). 3D confocal images (H) and thickness (I) of MRSA biofilms stained by SYTO 9 after different treatments, scale bar = 50 μm. (J) Images of MRSA biofilms stained by crystal violet after different treatments. (Data are presented as the mean ± s. d., *p < 0.05, *** p < 0.001)

Biofilm plays a crucial role by providing a protective shield for bacteria during infections, so the anti-biofilm effect is essential to the practical application of antibacterial agents [38]. The effectiveness of E-Au NPs against MRSA biofilm was first verified using morphological confocal images. In Fig. 2H and I, the control and NIR laser alone groups exhibited intact and dense biofilms with strong green fluorescence signals, while E-Au NPs partially hindered biofilm formation, resulting in a fragmented structure. In E-Au NPs plus laser group, the antibiofilm effect was further enhanced, and the bacteria could barely form a steady biofilm with only sporadic microcolonies existed. Besides, the thickness of MRSA biofilm was 3.539 ± 1.415 μm with E-Au NPs treatment and the thickness significantly decreased after treatment with E-Au NPs plus laser (1.068 ± 0.771 μm) compared with the control group (8.325 ± 0.928 μm) and laser alone group (8.128 ± 1.364 μm). Considering that biofilm biomass is an important factor in biofilm formation, its reduction was evident in the E-Au NPs plus laser group, as confirmed by crystal violet staining, aligning with the findings from the morphological confocal images (Fig. 2J, Fig. S12). Moreover, the efficacy against matured biofilm, which was more important to treat the infection, was further investigated (Fig. S13). As shown in micro and macro images, E-Au NPs plus laser treatment exhibited notable destructive effect to mature biofilms with the sparsest biofilms and the destruction rate was more than 90%, indicating the excellent antibiofilm ability of E-Au NPs at both biofilm formation stages.

Potential antibacterial mechanism of E-Au NPs

Based on its excellent antibacterial properties, the possible mechanisms of the E-Au NPs were investigated. The phenolic groups EGCG in E-Au NPs were prone to undergo oxidation to form electron-deficient semiquinones in the presence of Au3+. These highly reactive semiquinones could then bind with sulfhydryl residues of proteins, resulting in the formation of quinoproteins (quinone–protein conjugates) (Fig. 3A). Although these quinoproteins have been reported to participate in several physiological processes, such as apoptosis, their potential antibacterial effects had not been further investigated. To verify and quantify the amount of quinoproteins, a redox–cycling staining assay was employed. This assay involved that quinoproteins convert colorless nitroblue tetrazolium into insoluble purple formazan in the presence of glycine. Glyceraldehyde-3-phosphate dehydrogenase (GAPDH) was used as a marked protein to chosen to detect the production of quinoprotein. Following incubation of E-Au NPs with GAPDH, the purple bands on the sodium dodecyl-sulfate polyacrylamide in agarose gel electrophoresis revealed concentration-dependent formation of quinoproteins (Fig. 3B). Subsequently, the production of quinoproteins in bacteria was further evaluated by MRSA with E-Au NPs at varying concentrations and recording the optical density at 530 nm. The results showed an increase in quinoprotein levels with higher concentrations and longer incubation time, with minimal quinoprotein production in the control and Au3+ alone group. This highlighted the crucial role of phenolic ligands in the formation of quinoproteins (Fig. 3C, D).

Fig. 3.

Fig. 3

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Elucidation of the antibacterial modes of E-Au NPs in vitro. (A) Schematic illustration of the formation of quinoproteins owing to the polyphenols in E-Au NPs. (B) Qualitative analysis of quinoprotein formation after treatment with E-Au NPs at different concentrations. (C) Quantitative analysis of quinoprotein formation in MRSA during treatment with E-Au NPs. (D) Maximum rate of quinone protein production at different concentrations. (E) Bright-field and DCFH-DA staining images of ROS after different treatments, scale bar = 200 μm. (F) SEM and TEM images of MRSA with different treatments, scale bar = 400 nm. Leakage of protein (G), nucleic acids (H) and K+ (I) from MRSA with different treatments. (Data are presented as the mean ± s. d., ** < 0.01, ***p < 0.001)

In addition, the NIR laser-induced phototherapy, including both photodynamic and photothermal effects, efficiently boosted the antibacterial efficacy. As depicted in Fig. 3E and Fig. S14, there was no ROS fluorescence signal in the control group and only a few signals in the E-Au group. However, the ROS fluorescence signal was significantly enhanced with the NIR laser due to the photodynamic effect. Increased ROS levels in cells can disrupt cellular physiological processes, attack key macromolecules, and damage the cellular structure of bacterial cells. Morphological examination of MRSA treated with E-Au NPs and laser irradiation was further conducted by scanning electron microscopy (SEM) and TEM. As shown in Fig. 3F, SEM displayed intact bacteria with smooth surfaces in the control group, whereas MRSA appeared shrunken and irregular after E-Au NPs treatment, and cells were fragmented with disrupted cell structures after treatment with E-Au NPs plus laser irradiation. Similarly, TEM images revealed slightly nonuniform MRSA cytoplasm after E-Au NPs treatment, with further disruption and leakage of cytoplasm upon treatment with E-Au NPs plus laser irradiation. The incomplete cell wall indicated intracellular component leakage, such as proteins, DNA, and K+, which was corroborated through various techniques (e.g., bicinchoninic acid protein assay; Fig. 3G-I).

Next, the antibacterial mechanisms were further explored through RNA sequencing. A number of 1433 differentially expressed genes (DEGs) including 763 upregulated genes and 642 down-regulated genes compared with the control were analyzed by the volcano plot analyses (Fig. 4A). As shown in Fig. 4B, partially significantly changed genes of DEGs were listed in the heatmap. Accessory gene regulator (Agr) plays an important role in intercellular signaling quorum sensing which was decreased after E-Au NPs plus laser irradiation treatment. The down-regulation of virulence factor (Spa, Hla) and antibacterial resistance-related gene (ermC) indicated the attenuation of pathogenicity and invasiveness. Besides, the expression of genes related to maintenance (icaA, icaD) and adhesion (Clfa, Clfb) hinted at interference with biofilm formation. In contrast to control group, oxidative stress-related genes were upregulated, leading to ROS production. Further analysis of RNA sequencing through gene ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways analysis, revealed enrichment in cellular processes, catalytic activities, and membrane-related pathways (Fig. 4C-F). As for KEGG analysis, DEGs were enriched in pathways of metabolic pathway, membrane transport, and cell growth and death pathways, focusing on biosynthesis metabolites enrichment analysis.

Fig. 4.

Fig. 4

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Gene transcriptome assay. (A) Volcano plot analyses of DEGs treated with E-Au NPs plus laser. Down-regulated genes are in blue. Up-regulated genes are in red. Gray dots represent genes are less than 2-fold differential expression. (B) Heatmap of several differentially expressed genes associated with quorum sensing, virulence, antibacterial resistance, biofilm, adhesion and oxidative stress. GO analysis (C), GO enrichment (D), KEGG pathways analysis (E) and KEGG enrichment (F) of DEGs between the control group and E-Au group

To sum up, the results revealed that the potential antibacterial mechanism of E-Au NPs involved quinoproteins production, ROS generation from photothermal therapy, cellular structure disruption, and regulation of genes associated with biofilm formation, pathogenicity, invasiveness, and quorum sensing.

In vivo treatment effect of MRSA-infected skin wounds

The photothermal effect and in vivo therapeutic performance of E-Au NPs based treatment were initially evaluated using the MRSA biofilm infected skin wounds murine model (Fig. 5A). After the establishment of the MRSA biofilm infected skin wounds model, mice were administered with E-Au NPs or control agents on Day 1 and 3, with PBS serving as the control group for wound healing. With NIR irradiation, infrared thermographic images showed that the temperature of infected skin wounds was improved both in EGCG and E-Au groups while the improvement was more significant in E-Au group indicating the potential ability of PTT therapy (Fig. 5B). As shown in Fig. 5C, D, wounds without MRSA infection, defined as the Un-inf group, healed naturally, and its wound area recovered to 22.91% compared to 37.92% for the PBS group on day 8. Wounds treated with EGCG showed slight improvement at 30.77% but this effect was not enhanced by NIR laser irradiation. Conversely, the wound area recovered to 28.98% following E-Au NPs treatment and achieved the best therapeutic effect at 17.21% after laser irradiation, surpassing even the healing rate of the Un-inf group.

Fig. 5.

Fig. 5

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In vivo therapeutic effect of E-Au NPs for MRSA-infected skin wounds model. (A) Schematic illustration of the treatment of E-Au NPs with laser in MRSA-infected skin wounds model. (B) Infrared thermographic images disposed of with NIR laser on mice dorsal cutaneous wounds. (C) Photographs of wound in MRSA-infected mice after different treatment for 7 days. The Un-inf group represents uninfected skin wounds. (D) Quantification analysis of infected wound area. Evaluation of bacterial colonies inside infected skin after different treatments (E) and relative bacteria counts (F). (G) Evaluation of infected skin wound tissue by hematoxylin and eosin (H&E) staining. Red circles indicate the formation of blood vessels, scale bar = 1 mm/250 µm. (H) Immunohistochemical staining analysis of IL-6 in the skin. (Data are presented as the mean ± s. d., *p < 0.05, **p < 0.01, ***p < 0.001)

On day 8, infected wound tissues were collected for LB-agar plate CFU counting to quantify MRSA levels. The EGCG and EGCG plus laser groups showed numerous MRSA colonies compared to E-Au NPs group. On the contrary, mice treated with E-Au NPs had significantly lower MRSA, especially with NIR laser irradiation, confirming the in vivo antibacterial potential of E-Au NPs (Fig. 5E, F). Histopathological analysis was performed to evaluate the epithelial gap and anti-inflammatory treatment effect of E-Au NPs on the MRSA-infected skin wound tissues. H&E staining images revealed that the epithelial gap was shortened and wound healing was promoted after treatment with E-Au NPs and NIR laser irradiation (Fig. 5G, Fig. S15 and Fig. S16). Besides, immunohistochemistry (IHC) was performed to assess the amount of proinflammatory, such as cytokines interleukin-6 (IL-6). As shown in Fig. 5H and Fig. S17, IL-6 was highly expressed in PBS, EGCG, and EGCG plus NIR groups while notably decreased after the treatment of E-Au NPs, indicating the significant inhibition of the inflammatory reaction of infection.

In vivo treatment effect of MRSA-infected keratitis

The in vivo treatment effect performance of E-Au NPs was further evaluated in the MRSA-infected keratitis model (Fig. 6A). After 48 h incubation of MRSA suspension on the eyes, the typical symptoms of bacterial keratitis, such as cornea edema, conjunctival congestion, opacification, and periocular purulent exudation appeared, indicating the successful establishment of the MRSA-infected keratitis model. Mice were treated with E-Au NPs twice on day 2 and day 4, with PBS and cefazolin sodium (CS) used as controls for keratitis healing. During the 16 day-long experiments, the murine cornea of the control and CS group gradually deteriorated and showed severe MRSA biofilm infection and inflammation symptoms as well as abundant corneal neovascularization, with the clinical grading scale 14.33 ± 1.16 for the control group and 13.67 ± 0.58 for the CS group on day 16 (Fig. 6B, C). When mice treated with E-Au NPs, the cornea inflammatory symptoms deteriorated with edema and neovascularization in the first 8 days while were gradually relieved in the later 8 days (clinical grading scale: 7.67 ± 1.00). Upon laser irradiation, the symptoms of keratitis further decreased and achieved the best therapeutic effect. The cornea became transparent with no neovascularization, and infection of the cornea and surrounding tissue was effectively controlled (clinical grading scale: 2.67 ± 0.58). Besides, the corneal epithelium defect was evaluated through sodium fluorescein staining. In control and CS groups, the epithelium defect of the cornea was stained for a large area while the area was smaller after E-Au treatment. There was no fluorescein staining in the E-Au plus laser group, indicating superior corneal recovery and surface regularity. Keratitis can also reduce tear secretion, which was assessed using the phenol red thread assay. Indeed, tear secretion in the control group was impaired, with a wetting length of the phenol red of less than 2 mm. After treatment with E-Au NPs plus laser, tear secretion almost fully recovered to norma, with a wetting length of approximate 5.53 mm (Fig. 6D).

Fig. 6.

Fig. 6

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In vivo therapeutic effect of E-Au NPs for MRSA-infected keratitis. (A) Schematic illustration of the treatment of E-Au NPs with laser in MRSA-infected keratitis model. (B) Slit lamp images of different treatments on day 0, 4, 8, 12, 16 and sodium fluorescein staining of corneas. (C) The clinical grading scale of different treatments. (D) Quantification analysis of phenol red thread test. H&E staining of the cornea (E) and quantification analysis of the corneal thickness (F). The parts framed with the black dotted line were enlarged, scale bar = 100 μm/20 µm. Immunohistochemical staining analysis of IL-6 in the cornea (G) and quantification analysis (H), scale bar = 100 μm. (I) H&E staining of the retina, scale bar = 100 μm. (J) Measurement of IOP. (K) Cytotoxicity of HCEC incubated with E-Au NPs for 24 h with or without laser irradiation. (Data are presented as the mean ± s. d., *p < 0.05, ***p < 0.001)

Histopathological analysis was conducted to assess the impact of E-Au NPs treatment on MRSA-infected cornea tissues in terms of antibacterial and anti-inflammatory effects. As shown in Fig. 6E, F, severe inflammation with inflammatory cell infiltration and corneal edema with irregular epithelium and stromal matrix were observed in control and CS groups through H&E staining. However, following treatment with E-Au NPs plus laser, a significant decrease in inflammatory cells and disappearance of edema were noted, along with restoration of normal corneal structure. Additionally, the expression of proinflammatory cytokines IL-6 was notably higher in the control and CS groups compared to the treatment group, indicating effective inhibition of the inflammatory response during the late stage of infection (Fig. 6G, H).

On the basis of the excellent therapeutic effect of MRSA biofilm-infected skin wounds and keratitis, the local and systemic biosafety of E-Au NPs was evaluated for the potential clinical translation. Sodium fluorescein staining revealed no significant corneal epithelial defect after E-Au NPs administration compared to the control group (Fig. S18). As depicted in Fig. 6I, pathological analysis of retinal biosafety showed no apparent structural changes post-treatment. Intraocular pressure (IOP) returned to normal levels after treatment, indicating no disruption to aqueous humor circulation (Fig. 6J). On the other hand, cell viability of HCEC was 81.57% and 87.58% after E-Au NPs treatment even at the concentration of 400 µg/mL with or without laser irradiation (Fig. 6K). No significant systemic or metabolic side effects were observed after E-Au NPs treatment, as indicated by routine blood examinations and blood biochemical levels remaining within normal ranges (Fig. S19). Furthermore, H&E staining of major organs confirmed no histological abnormalities or signs of toxicity (Fig. S20). These findings collectively suggest that E-Au NPs treatment is effective for MRSA biofilm-infected keratitis with high biocompatibility, marking it promising for potential clinical applications.

Conclusion

This study presents a straightforward method for directly assembling an antibacterial E-Au NPs photothermal therapy nanosystem at room temperature without the need for seeding agents or templates. The PTT E-Au NPs exhibited excellent antibacterial activity against various bacteria, including the multidrug-resistant MRSA strain and therapeutic efficacy against MRSA biofilm-infected skin wounds and keratitis. Multiple synergistic antibacterial mechanisms of the PTT E-Au NPs have been identified, including mild temperature photothermal therapy, ROS burst, structural damage and quinoprotein production. Furthermore, these antibacterial mechanisms were confirmed through RNA sequencing. Importantly, the PTT of E-Au NPs achieved a balance between high-efficiency antibacterial properties and good biocompatibility without toxic side effects or dysfunction at both local and systemic levels. Considering the antibacterial efficacy, biosafety, and simple synthesis methods, the E-Au NPs presents great potential for clinical applications, particularly in antibiotic-resistant bacterial infections.

Supplementary information

Supplementary data to this article can be found online. Including the materials and methods; size distribution of E-Au NPs; hydrodynamic size analysis of different solution; FT-IR spectra of E-Au NPs; standard curve of Au by ICP-MS; temperature variation of E-Au NPs and EGCG-Ag; survival rate of MRSA treated with E-Au NPs; the photographs and survival rate of E. coli treated with E-Au NPs plus laser at varied time and concentrations; the photographs and survival rate of S. aureus treated with E-Au NPs plus laser at varied time and concentrations; quantification analysis of wound area; vessel density of wound healing tissue sites after different treatments; immunohistochemical staining positive area of IL-6; sodium fluorescein staining of cornea; routine blood examinations and blood biochemical examinations; preliminary toxicity study of main organs.

Electronic supplementary material

Below is the link to the electronic supplementary material.

Supplementary Material 1 (5.7MB, docx)

Acknowledgements

This study was supported by the Key Research and Development Project of Zhejiang Province (2023C02040, 2024C03073), the National Natural Science Foundation of China (32372757, 82271064, and 52003053), the Natural Science Foundation of Zhejiang Province (Grant number LR23H120001), the innovative Program of Chinese Academy of Agricultural Sciences (CAAS-ASTIP-2021-TRI), and the Biological and Medical Sciences of Applied Summit Nurturing Disciplines in Anhui Province (Anhui Education Secretary Department [2023]13).

Author contributions

Y. Ye, Q. Zheng, Z. Wang, S. Wang, Z. Lu, Q. Chu and Y. Liu conceived and designed the experiments. Y. Ye, Q. Zheng performed the most of the experiments, analyzed data and wrote the original manuscript. K. Yao and H. Chen revised and edited the manuscript. B. Wei, H. Han and X. Zhang designed the research as well as revised and edited the manuscript. All authors read and approved the final manuscript.

Data availability

No datasets were generated or analysed during the current study.

Declarations

Ethics approval and consent to participate

The experimental protocol concerning animals used in this work was approved by the Animal Ethics Committee, the Second Affiliated Hospital, School of Medicine, Zhejiang University (Approval No. 2022 − 164).

Consent for publication

All authors involved in this study have provided their consent for the publication of the research findings.

Competing interests

The authors declare no competing interests.

Footnotes

Publisher’s note

Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.

Yang Ye and Qinqin Zheng have contributed equally to this work.

Contributor Information

Bing Wei, Email: weibing90@fynu.edu.cn.

Haijie Han, Email: hanhj90@zju.edu.cn.

Xiangchun Zhang, Email: zhangxc@tricaas.com.

References

  • 1.Baker RE, Mahmud AS, Miller IF, Rajeev M, Rasambainarivo F, Rice BL, Takahashi S, Tatem AJ, Wagner CE, Wang LF, et al. Infectious disease in an era of global change. Nat Rev Microbiol. 2022;20(4):193–205. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 2.Fisher RA, Gollan B, Helaine S. Persistent bacterial infections and persister cells. Nat Rev Microbiol. 2017;15(8):453–64. [DOI] [PubMed] [Google Scholar]
  • 3.Uyttebroek S, Chen B, Onsea J, Ruythooren F, Debaveye Y, Devolder D, Spriet I, Depypere M, Wagemans J, Lavigne R, et al. Safety and efficacy of phage therapy in difficult-to-treat infections: a systematic review. Lancet Infect Dis. 2022;22(8):E208–20. [DOI] [PubMed] [Google Scholar]
  • 4.Ciofu O, Moser C, Jensen PO, Hoiby N. Tolerance and resistance of microbial biofilms. Nat Rev Microbiol. 2022;20(10):621–35. [DOI] [PubMed] [Google Scholar]
  • 5.Flemming HC, Wingender J, Szewzyk U, Steinberg P, Rice SA, Kjelleberg S. Biofilms: an emergent form of bacterial life. Nat Rev Microbiol. 2016;14(9):563–75. [DOI] [PubMed] [Google Scholar]
  • 6.Koo H, Allan RN, Howlin RP, Stoodley P, Hall-Stoodley L. Targeting microbial biofilms: current and prospective therapeutic strategies. Nat Rev Microbiol. 2017;15(12):740–55. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 7.Negi A, Perveen S, Gupta R, Singh PP, Sharma R. Unraveling dilemmas and Lacunae in the Escalating Drug Resistance of to Bedaquiline, Delamanid, and Pretomanid. J Med Chem. 2024;67(4):2264–86. [DOI] [PubMed] [Google Scholar]
  • 8.Vonasek BJ, Samuel AM, Henderson SL, Strayer JR, Bogenschutz MC. Safety and Treatment outcomes of infants and children treated with daptomycin: six-year experience from a Pediatric Academic Medical Center. Clin Pediatr. 2024;30:99228241242186. [DOI] [PubMed] [Google Scholar]
  • 9.Makabenta JMV, Nabawy A, Li CH, Schmidt-Malan S, Patel R, Rotello VM. Nanomaterial-based therapeutics for antibiotic-resistant bacterial infections. Nat Rev Microbiol. 2021;19(1):23–36. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 10.Makvandi P, Wang CY, Zare EN, Borzacchiello A, Niu LN, Tay FR. Metal-based nanomaterials in Biomedical Applications: antimicrobial activity and cytotoxicity aspects. Adv Funct Mater. 2020;30(22):1910021. [Google Scholar]
  • 11.Wang Y, Yang YN, Shi YR, Song H, Yu CZ. Antibiotic-free antibacterial strategies enabled by nanomaterials: Progress and perspectives. Adv Mater. 2020;32(18):1904106. [DOI] [PubMed] [Google Scholar]
  • 12.Geng Z, Cao Z, Liu J. Recent advances in targeted antibacterial therapy basing on nanomaterials. Exploration. 2023;3(1):20210117. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 13.Han HJ, Li S, Xu MY, Zhong YY, Fan WJ, Xu JW, Zhou TL, Ji J, Ye J, Yao K. Polymer- and lipid-based nanocarriers for ocular drug delivery: current status and future perspectives. Adv Drug Deliver Rev. 2023;196:114770. [DOI] [PubMed] [Google Scholar]
  • 14.He J, Ye Y, Zhang DX, Yao K, Zhou M. Visualized Gallium/Lyticase-Integrated Antifungal Strategy for Fungal Keratitis Treatment. Adv Mater. 2022;34(49):202206437. [DOI] [PubMed] [Google Scholar]
  • 15.Pelgrift RY, Friedman AJ. Nanotechnology as a therapeutic tool to combat microbial resistance. Adv Drug Deliver Rev. 2013;65(13–14):1803–15. [DOI] [PubMed] [Google Scholar]
  • 16.Du Y, Huo Y, Yang Q, Han Z, Hou L, Cui B, Fan K, Qiu Y, Chen Z, Huang W, et al. Ultrasmall iron-gallic acid coordination polymer nanodots with antioxidative neuroprotection for PET/MR imaging-guided ischemia stroke therapy. Exploration. 2023;3(1):20220041. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 17.Hu Z, Shan J, Jin X, Sun W, Cheng L, Chen XL, Wang X. Nanoarchitectonics of in situ antibiotic-releasing Acicular Nanozymes for Targeting and Inducing cuproptosis-like death to Eliminate Drug-resistant Bacteria. ACS Nano. 2024;18(35):24327–49. [DOI] [PubMed] [Google Scholar]
  • 18.Wang W, Cui Y, Wei X, Zang Y, Chen X, Cheng L, Wang X. CuCo2O4 nanoflowers with multiple enzyme activities for treating bacterium-infected wounds via cuproptosis-like death. ACS Nano. 2024;18(24):15845–63. [DOI] [PubMed] [Google Scholar]
  • 19.Tang SH, Zheng J. Antibacterial activity of silver nanoparticles: Structural effects. Adv Healthc Mater. 2018;7(13):201701503. [DOI] [PubMed] [Google Scholar]
  • 20.Ye Y, He J, Wang HL, Li WB, Wang QY, Luo CQ, Tang XJ, Chen XY, Jin XM, Yao K, et al. Cell Wall Destruction and Internal Cascade Synergistic Antifungal Strategy for Fungal Keratitis. ACS Nano. 2022;16(11):18729–45. [DOI] [PubMed] [Google Scholar]
  • 21.Zhao X, Chen Z, Zhang S, Hu Z, Shan J, Wang M, Chen XL, Wang X. Application of metal-organic frameworks in infectious wound healing. J Nanobiotechnol. 2024;22(1):387. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 22.Zheng QY, Liu XM, Zheng YF, Yeung KWK, Cui ZD, Liang YQ, Li ZY, Zhu SL, Wang XB, Wu SL. The recent progress on metal-organic frameworks for phototherapy. Chem Soc Rev. 2021;50(8):5086–125. [DOI] [PubMed] [Google Scholar]
  • 23.Shan J, Jin X, Zhang C, Huang M, Xing J, Li Q, Cui Y, Niu Q, Chen XL, Wang X. Metal natural product complex Ru-procyanidins with quadruple enzymatic activity combat infections from drug-resistant bacteria. Acta Pharm Sin B. 2024;14(5):2298–316. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 24.Chen Y, Gao YJ, Chen Y, Liu L, Mo AC, Peng Q. Nanomaterials-based photothermal therapy and its potentials in antibacterial treatment. J Control Release. 2020;328:251–62. [DOI] [PubMed] [Google Scholar]
  • 25.Li ZJ, Lei H, Kan AK, Xie HQ, Yu W. Photothermal applications based on graphene and its derivatives: a state-of-the-art review. Energy. 2021;216:2020119262. [Google Scholar]
  • 26.Chang MY, Hou ZY, Wang M, Yang CZ, Wang RF, Li F, Liu DL, Peng TL, Li CX, Lin J. Single-atom pd nanozyme for ferroptosis-boosted mild-temperature Photothermal Therapy. Angew Chem Int Edit. 2021;60(23):12971–79. [DOI] [PubMed] [Google Scholar]
  • 27.Gao G, Sun XB, Liang GL. Nanoagent-promoted mild-temperature Photothermal Therapy for Cancer Treatment. Adv Funct Mater. 2021;31(25):202100738. [Google Scholar]
  • 28.Xu JW, Yao K, Xu ZK. Nanomaterials with a photothermal effect for antibacterial activities: an overview. Nanoscale. 2019;11(18):8680–91. [DOI] [PubMed] [Google Scholar]
  • 29.Ye Y, He J, Qiao Y, Qi YC, Zhang HB, Santos HA, Zhong DN, Li WL, Hua SY, Wang W, et al. Mild temperature photothermal assisted anti-bacterial and anti-inflammatory nanosystem for synergistic treatment of post-cataract surgery endophthalmitis. Theranostics. 2020;10(19):8541–57. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 30.Jia QY, Song Q, Li P, Huang W. Rejuvenated photodynamic therapy for bacterial infections. Adv Healthc Mater. 2019;8(14):201900608. [DOI] [PubMed] [Google Scholar]
  • 31.Wu YF, Li JA, Zhu LW, Wang DL, Song JY, Yu XY, Li Y, Tang BZ. Photosensitive AIEgens sensitize bacteria to oxidative damage and modulate the inflammatory responses of macrophages to salvage the photodynamic therapy against MRSA. Biomaterials. 2024;309:122583. [DOI] [PubMed] [Google Scholar]
  • 32.He J, Zhang W, Cui Y, Cheng L, Chen XL, Wang X. Multifunctional Cu2Se/F127 hydrogel with SOD-Like enzyme activity for efficient Wound Healing. Adv Healthc Mater. 2024;13(16):e2303599. [DOI] [PubMed] [Google Scholar]
  • 33.Efenberger-Szmechtyk M, Nowak A, Czyzowska A. Plant extracts rich in polyphenols: antibacterial agents and natural preservatives for meat and meat products. Crit Rev Food Sci. 2021;61(1):149–78. [DOI] [PubMed] [Google Scholar]
  • 34.Zheng T, Cui M, Chen H, Wang J, Ye H, Zhang Q, Sun S, Feng Y, Zhang Y, Liu W, Chen R, Li Y, Dong Z. Co-assembled nanocomplexes comprising epigallocatechin gallate and berberine for enhanced antibacterial activity against multidrug resistant Staphylococcus aureus. Biomed Pharmacother. 2023;163:114856. [DOI] [PubMed] [Google Scholar]
  • 35.Li W, Li W, Wan Y, Wang L, Zhou T. Preparation, characterization and releasing property of antibacterial nano-capsules composed of ε-PL-EGCG and sodium alginate-chitosan. Int J Biol Macromol. 2022;204:652–60. [DOI] [PubMed] [Google Scholar]
  • 36.Yu R, Chen H, He J, Zhang Z, Zhou J, Zheng Q, Fu Z, Lu C, Lin Z, Caruso F, Zhang X. Engineering Antimicrobial Metal-Phenolic Network Nanoparticles with High Biocompatibility for Wound Healing. Adv Mater., Bakun P, Mlynarczyk DT, Koczorowski T, Cerbin-Koczorowska M, Piwowarczyk L, Kolasinski E, Stawny M, Kuzminska J, Jelinska A, Goslinski T. Tea-break with epigallocatechin gallate derivatives - Powerful polyphenols of great potential for medicine. Eur J Med Chem. 2023; 261: 2023115820. [DOI] [PubMed]
  • 37.Zhang SL, Mao BY, Shumao C, Zhang QX, Zhao JX, Tang X, Chen W. Absorption, metabolism, bioactivity, and biotransformation of epigallocatechin gallate. Crit Rev Food Sci. 2023;2:1–21. [DOI] [PubMed] [Google Scholar]
  • 38.Han HJ, Gao YF, Chai MY, Zhang XB, Liu SR, Huang Y, Jin Q, Grzybowski A, Ji J, Yao K. Biofilm microenvironment activated supramolecular nanoparticles for enhanced photodynamic therapy of bacterial keratitis. J Control Release. 2020;327:676–87. [DOI] [PubMed] [Google Scholar]

Associated Data

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Supplementary Materials

Supplementary Material 1 (5.7MB, docx)

Data Availability Statement

No datasets were generated or analysed during the current study.

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