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. 2024 Jan 3;15(2):553–560. doi: 10.1039/d3md00611e

Carbopol 940-based hydrogels loading synergistic combination of quercetin and luteolin from the herb Euphorbia humifusa to promote Staphylococcus aureus infected wound healing

Xiying Wu a,b,c,†, Hao-Wei Chen a,b,†, Ze-Yu Zhao a,b, Lisha Li c, Chi Song a,b, Juan Xiong b, Guo-Xun Yang b, Quangang Zhu c,✉, Jin-Feng Hu a,b,✉
PMCID: PMC10880921  PMID: 38389873

Abstract

With the increasing prevalence of Staphylococcus aureus infections, rapid emergence of drug resistance and the slow healing of infected wounds, developing an efficient antibiotic-free multifunctional wound dressing for inhibiting S. aureus and simultaneously facilitating wound healing have become a huge challenge. Due to their excellent biocompatibility and biodegradability, some carbopol hydrogels based on plant extracts or purified compounds have already been applied in wound healing treatment. In China, Euphorbia humifusa Willd. (EuH) has been traditionally used as a medicine and food homologous medicine for the treatment of furuncles and carbuncles mainly caused by S. aureus infection. In an earlier study, EuH-originated flavonoids quercetin (QU) and luteolin (LU) could serve as a potential source for anti-S. aureus drug discovery when used in synergy. However, the in vivo effects of QU and LU on S. aureus-infected wound healing are still unknown. In this study, we found a series of Carbopol 940-based hydrogels loading QU and LU in combination could disinfect S. aureus and also could promote wound healing. In the full-thickness skin defect mouse model infected with S. aureus, the wound contraction ratio, bacterial burden, skin hyperplasia and inflammation score, as well as collagen deposition and blood vessels were then investigated. The results indicate that the optimized QL2 [QU (32 μg mL−1)–LU (8 μg mL−1)] hydrogel with biocompatibility significantly promoted S. aureus-infected wound healing through anti-infection, anti-inflammation, collagen deposition, and angiogenesis, revealing it as a promising alternative for infected wound repair.

An optimized QU–LU Carbopol 940-based hydrogel significantly promoted S. aureus-infected wound healing through anti-infection, anti-inflammation, collagen deposition and angiogenesis, revealing it as a promising alternative for infected wound repair.graphic file with name d3md00611e-ga.jpg

Introduction

Bacterial infection is a major problem for wound healing, making the treatment of infected wounds become a significant burden to the global medical system.1 Among the problematic bacteria, Staphylococcus aureus is responsible for a large number of hospital-acquired infections, the presence of which in wounds can elongate the wound healing procedure.2 Although antibiotics have been widely used against S. aureus for a long time in clinics, the efficiency is usually not satisfactory owing to the rapid emergence of drug resistance.3–5 Thus, developing an antibiotic-free multifunctional wound dressing for inhibiting S. aureus and simultaneously facilitating wound healing should be at the forefront of infected wound research.

Hydrogels are generally formed from hydrophilic polymer chains embedded in a water-rich environment, and have highly desirable physicochemical properties that make them suitable for biomedical applications.6 Hydrogels are widely used for tissue regeneration, especially in wound healing applications due to their elasticity being similar to that of the native tissue, and due to their ability to provide a moist microenvironment and absorb wound exudates.7 In the past few years, plant extract-/purified compound-based hydrogels have been reported to have limited side effects compared to commercial drugs in wound healing.8–12 An ideal antibacterial hydrogel should be prepared with inherent anti-infection polymers in hydrogel fabrication or by incorporating antibacterial agents.7 To our knowledge, carbopol has been extensively used in developing hydrogels for wound healing due to its nontoxicity, good thermal stability, high compatibility with other drugs, and excellent tissue compatibilities.13 Recently, the curcumin-loaded methoxy poly(ethylene glycol)-poly(delta-valerolactone)-poly(epsilon-caprolactone) micelle-embedded Carbopol 940 hydrogel was demonstrated to be a potential candidate for the treatment of skin inflammation and full thickness wound healing.14 Moreover, a few herbal plant extracts or purified active compounds formulated into Carbopol 940 hydrogel preparations have been used for wound healing.15–17

Natural products have always been significant resources of alternatives of antibiotics against S. aureus.18,19 In particular, naturally occurring flavonoids are always abundant and widely distributed in plants, fruits and vegetables, making them known as inexpensive, green, and healthy products, which have attracted great interest from the pharmaceutical, chemical, and food industries.20–22 Notably, some flavonoids have been documented to play a significant role in wound healing cycle modulation.23,24Euphorbia humifusa Willd. (EuH) is a monoecious annual herb with medicinal and food/vegetable characteristics25,26 used to treat furuncles and carbuncles mainly caused by S. aureus infection. EuH has been documented to be rich in flavonoids.27–29 In a preceding study,30 two promising flavonoids [i.e., quercetin (QU) and luteolin (LU)] isolated from EuH could serve as a potential source for anti-S. aureus drug discovery when used in synergy, which was unveiled in our recent in vitro investigation. In fact, both QU and LU possess a number of medicinal benefits, including antioxidant and anti-inflammatory properties.31,32 Obvious evidence indicates that the wound treatment with individual flavonoids has encouraging results. For instance, QU could effectively promote cutaneous wound healing in mice by enhancing fibroblast proliferation, inhibiting inflammation and increasing the expression of growth factors.33 LU has also been reported to accelerate re-epithelialization of skin wounds and improve the impaired healing in diabetic animals.34 However, less is known about the in vivo effects of QU and LU (especially their combination) on S. aureus-infected wound healing. Hence, we prepared a series of carbopol hydrogels based on QU and LU, and assessed their in vivo effects on clearance of bacteria and promotion of S. aureus-infected wound healing, as well as the toxicity.

Experimental

Materials

Formaldehyde, dimethyl sulfoxide (DMSO), and Carbomer 940 were purchased from Sinopharm Chemical Reagent Co., Ltd. (Shanghai, China). The commercial Tegaderm™ film was supplied by 3M Health Care (Minnesota, USA). Cell counting kit-8 (CCK-8), tryptic soy agar (TSA), brain-heart infusion (BHI) agar and normal saline (veterinary) were from Beijing Solarbio Science & Technology Co., Ltd. (Beijing, China). Deionized distilled water was prepared using a Milli-Q purification instrument (Millipore, MA, USA). HaCaT cells were obtained from the Cell Bank of Chinese Academy of Sciences (Shanghai, China) and cultured in Dulbecco's modified Eagle medium (DMEM, Gibco) with 10% foetal bovine serum (FBS, Gibco) in a 5% CO2 incubator at 37 °C. Staphylococcus aureus ATCC 25904 (Newman) was provided by Prof. Lefu Lan (Shanghai Institute of Materia Medica, Shanghai, China) and cultured overnight at 37 °C on BHI agar plates for activation. Female ICR mice (6–8 weeks old) were from Slac Laboratory Animal Co., Ltd. (Shanghai, China). All other reagents were of analytical grade and used as received.

Cytotoxicity studies

CCK-8 assay was used to evaluate the viability for the human keratinocytes (HaCaT cells).35 In brief, the cells were seeded in 96-well plates at a density of 6 × 103 cells per well and cultured for 24 h at 37 °C. After incubation with different agents for 20 h, the cells were incubated with a fresh medium containing 10% CCK-8 solution for 2 h at 37 °C. The cell viabilities were determined by measuring the absorbance at 450 nm using a microplate reader. The untreated cells seeded on the plate served as the positive control, and each group has 6 replicates.

Preparation of hydrogels

The hydrogels were prepared according to previous reports with proper modifications.36 Briefly, Carbopol 940 (4.5 g) was mixed with deionized distilled water (200 mL), and the solution was kept overnight at ambient temperature allowing Carbopol 940 to swell. After adjusting the pH to 7 with triethanolamine, the solution was eventually adjusted to 300 mL (Carbopol 940, 1.5%, w/v) by the addition of deionized distilled water, and was stirred regularly for 10 min until the transparent hydrogels were formed. QU and LU solutions, each in a concentration of 8 mg mL−1, were then prepared with DMSO. Different concentrations of QU and/or LU were afterwards mixed in the hydrogels and stirred for 5 min until homogeneous. A series of gels, QU (32 μg mL−1), LU (8 μg mL−1), QL1 (16–4 μg mL−1), QL2 (32–8 μg mL−1) and QL3 (64–16 μg mL−1), were stored at 4 °C for further use.

Antibacterial activity of hydrogels

The antibacterial activity of hydrogels was evaluated by referring to the reported contact antibacterial method with proper modifications.3 Briefly, 50 μL of a bacterial suspension of 106 CFU mL−1 was mixed evenly with 1 mL of hydrogel in a 24-well plate, while 50 μL of the bacterial suspension with 1 mL of sterile normal saline was used as a control. After 4 h of cultivation at 37 °C, 1 mL of sterile normal saline was added to each well to resuspend the surviving bacteria. Then 20 μL of the resuspended bacterial solution was spread on the surface of a TSA plate and incubated at 37 °C for 18 h to calculate the colony. The assay was repeated three times independently.

In vivo biocompatibility test of hydrogels

This study was approved by the Institutional Animal Care and Use Committee (IACUC) at Fudan University (No. 202203-WU-HJF-01) and performed according to the institutional guidelines. Female ICR mice weighing 16–20 g and aged 6–8 weeks were used and a 0.8 cm × 0.8 cm portion of dorsal hair was removed from each mouse. Subsequently, the hydrogels (100 μL) were applied daily to the skin sites with sterile syringes (without needles). After treatment for fourteen consecutive days, the mice were sacrificed and the skin tissues were collected, fixed with 10% formaldehyde, embedded in paraffin, sectioned to the slices of 4 μm thickness, and then stained with hematoxylin–eosin (H&E). The tissue sections were observed under a microscope (Olympus, Tokyo, Japan).

In vivo infection wound treatment and wound healing promotion capabilities of hydrogels in a full-thickness skin defect infected mouse model

The in vivo wound infection treatment and wound healing promotion capabilities of the hydrogels were evaluated using a full-thickness skin defect infected model with female ICR mice. 105 mice were randomly divided into the following 7 groups: (1) Tegaderm™ film (3M Health Care, USA) as the negative group; (2) Carbopol hydrogel as the vehicle group; (3) QU (32 μg mL−1); (4) LU (8 μg mL−1); (5) QU (16 μg mL−1)–LU (4 μg mL−1) as the low dose drug-loaded group; (6) QU (32 μg mL−1)–LU (8 μg mL−1) as the medium dose drug-loaded group; and (7) QU (64 μg mL−1)–LU (16 μg mL−1) as the high dose drug-loaded group. 15 mice in each group were randomly divided into three sampling points: 3rd, 7th and 14th day (n = 5 for each sampling point). After grouping, all mice were anesthetized using a 5% chloral hydrate solution (0.3 mg per kg body weight) via intraperitoneal injection. The dorsal hair (0.8 cm × 0.8 cm) was removed and the full thickness circular skin wounds with 8 mm diameter were punched using sterilized scissors. Then the bacterial suspension (20 μL, 109 CFU mL−1) was added to each wound site, and covered with the Tegaderm™ film for 24 h. In the Tegaderm™ film group, the skin wounds were treated using 100 μL of PBS. As for the other six groups, 100 μL of the corresponding hydrogels were applied daily. After treatment for the 3rd, 7th and 14th day, the wound areas were recorded, a swab was obtained to determine the bacterial load, and the skin tissues were collected for further histological and immunohistochemical observation.

Visual evaluation of wound healing

The wounds of each group were captured using a digital camera after treatment for 3, 7 and 14 days, respectively. The area of each wound was counted using ImageJ (V 1.8.0) and the calculation formula of the wound contraction ratio was as follows:Wound contraction (%) = (A0 − An)/A0 × 100%,where n indicates the date after treatment, A0 represents the wound area of the initial day while An is the wound area at a specific day.

Bacterial load determination in the wound beds

The bacterial swabs obtained from each time point were rinsed in 2 mL of sterile normal saline to resuspend the surviving bacteria. Then the colony of 20 μL of the resuspended bacterial solution was incubated and calculated on a TSA plate as mentioned above.

Histology analysis

To evaluate the epidermal regeneration and inflammation in the wound area, the harvested skin samples on the 3rd, 7th and 14th day were subjected to the same H&E staining as the above in vivo biocompatibility test. Meanwhile, the sections were stained by Masson's trichrome staining for accessing the collagen content in the wound area. All slices were photo-captured using the microscope (Olympus, Tokyo, Japan). In addition, the major organs including heart, liver, spleen, lungs, and kidneys were used for the H&E staining to evaluate the toxicity.

Data analysis

The experimental data were expressed as mean ± standard deviation using GraphPad Prism 9 (Graph-Pad Software, San Diego, CA, USA). Statistical analysis was carried out using the one-way ANOVA test and chi-square test, and the differences were considered significant when *p < 0.05, **p < 0.01, and ***p < 0.001.

Results

Cytocompatibility of combinations based on QU and LU

The viability of HaCaT cells was used to evaluate the cytocompatibility of the combinations based on QU and LU. As shown in Fig. 1A, the cell viability remained above 95% in combinations at concentrations of less than QU (32 μg mL−1)–LU (8 μg mL−1), and did not differ from the control. After treatment with QU (64 μg mL−1)–LU (16 μg mL−1), the cell viability remained at 88%. Therefore, this concentration was selected as the highest concentration for the following experiments.

Fig. 1. In vitro cell compatibility and antibacterial test. (A) HaCaT cell viability of QU and LU combinations by using the CCK-8 method. (B) Bacterial survival ratio of S. aureus by the direct contact method. *p < 0.05, **p < 0.01, ***p < 0.001.

Fig. 1

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Antibacterial effect of the hydrogel

The hydrogels loading QU and LU both individually and in combination, as well as the pure hydrogel without any flavonoid (vehicle) were in contact with S. aureus to test their inherent antibacterial properties. After co-cultivation at 37 °C for 4 h, the hydrogels containing only one flavonoid or no flavonoids exhibited a sterilization ratio ranging from 57.2% to 65.8% without significant differences (Fig. 1B). Upon combination, the inhibition ratios of the QL2 [QU (32 μg mL−1)–LU (8 μg mL−1)] and QL3 [QU (64 μg mL−1)–LU (16 μg mL−1)] hydrogels against S. aureus were higher, reaching 77.0% and 82.3% (Fig. 1B), respectively.

In vivo wound healing performance of the hydrogels

To verify the in vivo synergistic effect of QU and LU, the skin tissue repair performance of the aforementioned hydrogels was studied using an S. aureus-infected mouse skin full-thickness defect model (Fig. 2A). As shown in Fig. 2B, the QL2 and QL3 groups had faster wound contraction than other hydrogels and the commercial Tegaderm™ film. Quantitative wound contraction rate results (Fig. 2C) demonstrated that the QL2 and QL3 groups healed significantly faster than either the Tegaderm™ film or the hydrogels with only one flavonoid (p < 0.05) throughout the treatment period. On day 14, significant wound contraction occurred in all seven groups compared to those on day 3, but the QL2 (100%) and QL3 (92.1%) groups with closed wounds were superior to other groups. Besides, there was no significant difference between the QL2 and QL3 groups. Additionally, the in vivo antibacterial activity of the hydrogels was assessed by collecting bacteria from the wound sites at each time point (Fig. 2D and E). Likewise, the number of residual S. aureus CFUs in the QL2 and QL3 groups reduced significantly (p < 0.01) compared to either the Tegaderm™ film or the hydrogels with only one flavonoid.

Fig. 2. In vivo anti-infection and S. aureus-infected wound healing. (A) Schematic illustration of the in vivo wound healing experiment procedure in the full-thickness skin defect model. (B) Representative skin wound images at day 0, 3, 7, and 14. Inner diameter of the black ring: 9 mm. (C) Wound contraction evaluation. (D) Images of S. aureus colonies growing on the agar plates derived from the infected tissues after various treatments at day 3, 7, and 14. (E) Total bacterial CFU (log) on the TSA agar plates. *p < 0.05, **p < 0.01, ***p < 0.001.

Fig. 2

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Histomorphological evaluation

To evaluate the healing effect of the hydrogels from a histological perspective, H&E and Masson's trichrome staining on regenerated skins were performed. After treating for 3 days, all groups exhibited varying degrees of fibroblast migration, proliferation, and inflammatory cell infiltration (Fig. 3A). Compared to the Tegaderm™ film and vehicle groups, the QL1–QL3 groups showed regenerated skin with more complete tissue structures on day 7 (Fig. 3A). After 14 days of therapy, the epidermis has been almost formed in all the groups. Notably, the tissues in either the Tegaderm™ film group or the hydrogel groups without combined QU and LU showed severe hyperplasia, while the epidermis tended to be normal in the QL1–QL3 groups. In particular, the wounds in the QL2 group (Fig. 3B) showed lower hyperplasia and inflammatory responses, compared to the Tegaderm™ film and vehicle groups (p < 0.05). In addition, as time increased after treatment, the blue area and intensity in the wounds of each group increased (Fig. 3C and D). After 1 and 2 weeks of treatment, the collagen content of the QL2 and QL3 groups was much higher than that of the others.

Fig. 3. Histomorphological analysis of wound regeneration after treatment. (A) H&E staining images, (B) skin hyperplasia and inflammation scores, (C) Masson's trichrome staining images, and (D) collagen deposition scores in various groups at day 3, 7, and 14 (n = 3). Scale bar: 200 μm. *p < 0.05, **p < 0.01, ***p < 0.001.

Fig. 3

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Immunohistochemistry (IHC) staining analysis

Tumor necrosis factor-α (TNF-α) and CD31 were selected as the vital indicators of inflammation and angiogenesis in the infected wound healing process. Compared with the Tegaderm™ group, the QL2 and QL3 hydrogels significantly reduced the expression of TNF-α during the tissue healing process (Fig. 4A and B). It could also be seen that the number of inflammatory cells in the groups with flavonoids gradually decreased with time. In contrast, the Tegaderm™ film and vehicle groups resulted in higher TNF-α expression on day 7 than on day 3, further implying the necessity of flavonoids. It should be noted that there was still inflammatory response in all groups after 2 weeks of treatment, suggesting the groups continued to be in the chronic inflammatory phase. Furthermore, compared to the Tegaderm™ film and vehicle, the wound sites treated with the hydrogels loading combined flavonoids showed higher CD31 expression during the treatment period (Fig. 4C and D). Additionally, on the 7th and 14th days, the expression levels of CD31 in the QL2 and QL3 groups were similar and significantly higher than that of the Tegaderm™ film group (p < 0.05).

Fig. 4. Immunohistochemical analysis of the wound tissues. Immunohistochemistry staining images of (A) TNF-α expression for inflammatory responses and (C) CD31 expression (red arrows represent new blood vessels) for neovascularization on days 3, 7, and 14. Scale bar: 100 μm. Quantitative analysis of (B) TNF-α and (D) CD31 expression. Data from the Tegaderm™ dressing group at day 3 for TNF-α and CD31 were taken as 100%. *p < 0.05, **p < 0.01, ***p < 0.001.

Fig. 4

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In vivo biocompatibility of the hydrogels

After treatment for fourteen consecutive days, a histological skin examination of the QL2 hydrogel was performed, as detailed in Fig. 5. No inflammatory cells in the skin tissue were observed when compared with a normal sample, showing that the QL2 hydrogel has no evident irritation to the skin. Meanwhile, vital organs including the heart, liver, spleen, lung, and kidney were harvested and stained to further evaluate the systemic biocompatibility of the QL2 hydrogel. As shown in Fig. 5, there was no significant histological difference between the QL2 hydrogel group and normal groups.

Fig. 5. Histomorphological evaluation of mice's skin and vital organs on the 14th day of hydrogel administration. Scale bar: 100 μm.

Fig. 5

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Discussion

Wounds infected by S. aureus represent a significant public health problem,37 and the resulting inflammatory response obviously impairs the quality of wound healing.38 For the management of infected wounds, strategies aimed at anti-infection and promoting healing should be employed, thus striking a balance between inflammation and tissue remodeling.39 Numerous studies have demonstrated that the flavonoids and Carbopol 940 hydrogel possess wound-healing properties due to their well-acclaimed anti-inflammatory, antioxidant, re-epithelialization, and angiogenesis effects.14,40–43 In our previous report, QU in combination with LU enhanced the antibacterial and antibiofilm efficacy synergistically, decreasing the membrane permeability and down-regulating the expression of multiple biofilm-related genes.30 Besides, QU and LU are known for their powerful anti-inflammatory and antioxidant potency due to the resonance stability of the phenoxyl radical,31,32 which support their potential use in wound healing. Therefore, a series of Carbopol 940 hydrogels based on QU and LU for S. aureus-infected wound healing were developed.

With an increase of QU and LU concentrations, the cytotoxicity of the combinations showed a concentration-dependent change, which is similar to the cytotoxicity of individual components.44,45 As QU (64 μg mL−1)–LU (16 μg mL−1) showed cell viability at 88%, it was selected as the high dose drug-loaded group, making the combinations used in this study have cytocompatibility. Additionally, the antibacterial properties of hydrogels are vital for wound dressing against infection.46 The hydrogels containing only one flavonoid or no flavonoids exhibited a moderate sterilization effect without significant differences, mainly due to the absence of nutrients in the hydrogels and the inherent antibacterial properties of carbopol. When QU and LU were used in combination, the antibacterial properties of the hydrogels were enhanced highly to reach 82.3% (Fig. 1), indicating that QU and LU in the hydrogels played a synergistic antibacterial effect against S. aureus.

The above results showed that the prepared hydrogels loading QU (≤64 μg mL−1) and LU (≤16 μg mL−1) had excellent biocompatibility and anti-S. aureus activity, which were beneficial for the repair of the infected skin wound. Consequently, an S. aureus-infected mouse skin full-thickness defect model was used to determine the in vivo effect.47 Compared to either the Tegaderm™ film group or the hydrogel groups with only one flavonoid, the QL2 and QL3 groups healed faster and reduced more S. aureus CFUs (Fig. 2), which exactly confirmed the synergistic effect of QU and LU in vivo. Besides, no significant differences were observed between the QL2 and QL3 groups, implying that the QL2 hydrogel should be an optimal candidate for infected wound healing dressing drugs. From a histological perspective, the wounds in the QL2 group (Fig. 3) showed very low hyperplasia and inflammatory responses. Since the metabolism of collagen changes continuously during the wound healing process, the collagen deposition is commonly used as an important indicator to reflect the wound condition.48 With time increased after treatment, the blue area and intensity in the wounds of the QL2 and QL3 groups increased dramatically (Fig. 3), indicating more collagen deposition and that these hydrogels can effectively promote wound healing.

Acute inflammatory responses may cause oxidative stress, further delaying the infected wound healing, while the intrinsic anti-oxidant activity of flavonoids is prone to impart a considerable anti-inflammatory ability to the agents.49 Therefore, TNF-α, the representative pro-inflammatory factor, was detected to estimate the efficacy of the hydrogels in extenuating inflammation.50 Meanwhile, CD31 plays a vital role in vascular regeneration for wound healing, and was hence chosen as an indicator of angiogenesis in the wound healing process.51 As shown in the results (Fig. 4), the QL2 and QL3 hydrogels significantly reduced the expression of TNF-α during the tissue healing process, but there was still inflammatory response after 2 weeks of treatment. Thus, flavonoids seem to be deficient to exert a remarkable anti-inflammatory effect in a short time and should be better used in combination with other anti-inflammatory drugs. Likewise, the wound sites treated with the hydrogels loading combined flavonoids showed higher CD31 expression. In short, by reducing the expression of TNF-α and simultaneously promoting the expression of CD31, the optimal QL2 hydrogel can significantly relieve the inflammatory reaction and promote wound healing. After treatment for fourteen consecutive days, the histological organ examination of the QL2 hydrogel was performed, showing that the QL2 hydrogel has good biocompatibility (Fig. 5).

Although the QL2 group significantly promoted in vivo infectious wound healing, inflammatory cells still existed in the tissues at the end of the treatment. The combination of flavonoids and anti-inflammatory drugs is thus recommended. In addition, our experiments were performed only with a single susceptible strain of S. aureus. Hence, these findings deserve to be extrapolated and confirmed with more isolates.

Conclusions

In summary, a series of carbopol hydrogels based on QU and LU for wound healing of S. aureus infections were developed. Antibacterial assays confirmed that the optimized QL2 [QU (32 μg mL−1)–LU (8 μg mL−1)] hydrogel presented remarkable antibacterial activity against S. aureus via the synergistic effect of QU and LU. In the S. aureus-infected full-thickness skin defect model, the QL2 group significantly promoted infectious wound healing through anti-infection, anti-inflammation, collagen deposition, and angiogenesis. In the future, plant-originated flavonoids should be better used in combination with other anti-inflammatory drugs to achieve prominent effects quickly. The synergistic design principle of antibiotic-free flavonoid-based hydrogels can be universally expanded to other combinations, inspiring a new methodology for the development of next-generation antibacterial agents.

Author contributions

Xiying Wu and Hao-Wei Chen have contributed equally to this work. Xiying Wu conducted the experiments, analyzed the data, wrote the manuscript, and provided the financial support. Hao-Wei Chen conducted the experiments and analyzed the data. Ze-Yu Zhao, Chi Song, and Lisha Li participated in the animal experiments. Juan Xiong and Guo-Xun Yang analyzed the data. Quangang Zhu revised the manuscript. Jin-Feng Hu developed the concept, provided the financial support, and revised the manuscript. All authors approved the final manuscript for submission.

Conflicts of interest

The authors declare no competing financial interest.

Supplementary Material

Acknowledgments

We thank Prof. Lefu Lan (Shanghai Institute of Materia Medica, Chinese Academy of Science, Shanghai 201203, PR China) for providing the S. aureus strain. This work was financially supported by the National Natural Science Foundation of China (No. 21937002, 81773599, 82003659).

Notes and references

  1. Zhou L. Zheng H. Liu Z. X. Wang S. Q. Liu Z. Chen F. Zhang H. P. Kong J. Zhou F. T. Zhang Q. Y. ACS Nano. 2021;15:2468–2480. doi: 10.1021/acsnano.0c06287. [DOI] [PubMed] [Google Scholar]
  2. He J.-M. Sun S.-C. Sun Z.-L. Chen J.-T. Mu Q. Int. J. Antimicrob. Agents. 2019;53:70–73. doi: 10.1016/j.ijantimicag.2018.08.021. [DOI] [PubMed] [Google Scholar]
  3. Yang Y. T. Liang Y. P. Chen J. Y. Duan X. L. Guo B. L. Bioact. Mater. 2022;8:341–354. doi: 10.1016/j.bioactmat.2021.06.014. [DOI] [PMC free article] [PubMed] [Google Scholar]
  4. Zhang J. K. Ge J. L. Xu Y. R. Chen J. M. Zhou A. W. Sun L. Gao L. Zhang Y. Gu T. T. Ning X. H. Int. J. Biol. Macromol. 2020;164:4466–4474. doi: 10.1016/j.ijbiomac.2020.08.247. [DOI] [PubMed] [Google Scholar]
  5. Zhao X. Liang Y. P. Huang Y. He J. H. Han Y. Guo B. L. Adv. Funct. Mater. 2020;30:1910748. doi: 10.1002/adfm.201910748. [DOI] [Google Scholar]
  6. Zhang Y. S. Khademhosseini A. Science. 2017;356:eaaf3627. doi: 10.1126/science.aaf3627. [DOI] [PMC free article] [PubMed] [Google Scholar]
  7. Asadi N. Pazoki-Toroudi H. Del Bakhshayesh A. R. Akbarzadeh A. Davaran S. Annabi N. Int. J. Biol. Macromol. 2021;170:728–750. doi: 10.1016/j.ijbiomac.2020.12.202. [DOI] [PubMed] [Google Scholar]
  8. Sharma A. Mittal P. Yadav A. Mishra A. K. Hazari P. P. Sharma R. K. ACS Appl. Bio Mater. 2022;5:598–609. doi: 10.1021/acsabm.1c01078. [DOI] [PubMed] [Google Scholar]
  9. Chummun Phul I. Huet M. A. L. Bekah D. Bhaw-Luximon A. RSC Med. Chem. 2023;14:534–548. doi: 10.1039/D2MD00402J. [DOI] [PMC free article] [PubMed] [Google Scholar]
  10. Jafari H. Ghaffari-Bohlouli P. Niknezhad S. V. Abedi A. Izadifar Z. Mohammadinejad R. Varma R. S. Shavandi A. J. Mater. Chem. B. 2022;10:5873–5912. doi: 10.1039/D2TB01056A. [DOI] [PubMed] [Google Scholar]
  11. Vasconcelos M. S. Souza T. F. G. Figueiredo I. S. Sousa E. T. Sousa F. D. Moreira R. A. Alencar N. M. N. Lima-Filho J. V. Ramos M. V. A. Phytother. Res. 2018;32:688–697. doi: 10.1002/ptr.6018. [DOI] [PubMed] [Google Scholar]
  12. Das U. Behera S. S. Singh S. Rizvi S. I. Singh A. K. Phytother. Res. 2016;30:1895–1904. doi: 10.1002/ptr.5700. [DOI] [PubMed] [Google Scholar]
  13. Hayati F. Ghamsari S. M. Dehghan M. M. Oryan A. J. Dermatol. Treat. 2018;29:593–599. doi: 10.1080/09546634.2018.1426823. [DOI] [PubMed] [Google Scholar]
  14. Song Z. M. Wen Y. Teng F. F. Wang M. Liu N. Feng R. L. New J. Chem. 2022;46:3674–3686. doi: 10.1039/D1NJ04719A. [DOI] [Google Scholar]
  15. Jales S. T. L. de M. Barbosa R. de Albuquerque A. C. Duarte L. H. V. da Silva G. R. Meirelles L. M. A. da Silva T. M. S. Alves A. F. Viseras C. Raffin F. N. de. L Moura T. F. A. J. Compos. Sci. 2022;6:231. doi: 10.3390/jcs6080231. [DOI] [Google Scholar]
  16. Pandey S. Shamim A. Shaif M. Kushwaha P. Naunyn-Schmiedeberg's Arch. Pharmacol. 2023;396:1811–1825. doi: 10.1007/s00210-023-02441-5. [DOI] [PubMed] [Google Scholar]
  17. Yuniarsih N. Hidayah H. Gunarti N. S. Kusumawati A. H. Farhamzah F. Sadino A. Alkandahri M. Y. Adv. Pharmacol. Pharm. Sci. 2023;2023:7680518. doi: 10.1155/2023/7680518. [DOI] [PMC free article] [PubMed] [Google Scholar] [Retracted]
  18. Sun H. Ansari M. F. Fang B. Zhou C.-H. J. Agric. Food Chem. 2021;69:7831–7840. doi: 10.1021/acs.jafc.1c02545. [DOI] [PubMed] [Google Scholar]
  19. Wang L. Kiffe-Delf A.-L. Ostermann P. N. Simons V. E. He D. Gao Y. van Geelen L. Dai H.-F. Zhao Y.-X. Schaal H. Mándi A. Király S. B. Kurtán T. Liu Z. Kalscheuer R. J. Agric. Food Chem. 2023;71:11056–11068. doi: 10.1021/acs.jafc.3c00447. [DOI] [PubMed] [Google Scholar]
  20. Deng M. Zhang S. Dong L. H. Huang F. Jia X. C. Su D. X. Chi J. W. Muhammad Z. Ma Q. Zhao D. Zhang M. W. Zhang R. F. J. Agric. Food Chem. 2022;70:14654–14664. doi: 10.1021/acs.jafc.2c03797. [DOI] [PubMed] [Google Scholar]
  21. Li D. Chen G. Ma B. Zhong C. Z. He N. J. J. Agric. Food Chem. 2020;68:1494–1504. doi: 10.1021/acs.jafc.9b06931. [DOI] [PubMed] [Google Scholar]
  22. Soto-Vaca A. Gutierrez A. Losso J. N. Xu Z. M. Finley J. W. J. Agric. Food Chem. 2012;60:6658–6677. doi: 10.1021/jf300861c. [DOI] [PubMed] [Google Scholar]
  23. Kapare H. S. Giram P. S. Raut S. S. Gaikwad H. K. Paiva-Santos A. C. Gels. 2023;9:375. doi: 10.3390/gels9050375. [DOI] [PMC free article] [PubMed] [Google Scholar]
  24. Soares R. D. F. Campos M. G. N. Ribeiro G. P. Salles B. C. C. Cardoso N. S. Ribeiro J. R. Souza R. M. Leme K. C. Soares C. B. de Oliveira C. M. Elston L. B. da Fonseca C. C. P. Ferreira E. B. Rodrigues M. R. Duarte S. M. S. Paula F. B. A. J. Biomed. Mater. Res., Part A. 2020;108:654–662. doi: 10.1002/jbm.a.36845. [DOI] [PubMed] [Google Scholar]
  25. Xiang N. Zhao J. B. Chang S. Q. Li S. S. Liu S. W. Wang C. Foods. 2023;12:751. doi: 10.3390/foods12040751. [DOI] [PMC free article] [PubMed] [Google Scholar]
  26. Kim C. G. Lim Y. Lee Y. H. Shin S. Y. Genes Genomics. 2016;38:999–1004. doi: 10.1007/s13258-016-0444-0. [DOI] [Google Scholar]
  27. Wang T. T. Zhou Z. Q. Wang S. Ji X. W. Wu B. Sun L. Y. Wen J. F. Kang D. G. Lee H. S. Cho K. W. Jin S. N. J. Physiol. Pharmacol. 2017;68:619–628. [PubMed] [Google Scholar]
  28. Tian Y. Sun L.-M. Liu X.-Q. Li B. Wang Q. Dong J.-X. Fitoterapia. 2010;81:799–802. doi: 10.1016/j.fitote.2010.04.012. [DOI] [PubMed] [Google Scholar]
  29. Gao S. Y. Sun D. J. Wang G. Zhang J. Jiang Y. N. Li G. Y. Zhang K. Wang L. Huang J. Chen L. X. Bioorg. Chem. 2016;69:121–128. doi: 10.1016/j.bioorg.2016.10.005. [DOI] [PubMed] [Google Scholar]
  30. Wu X. Y. Ma G.-L. Chen H.-W. Zhao Z.-Y. Zhu Z.-P. Xiong J. Yang G. X. Hu J.-F. J. Ethnopharmacol. 2023;306:116177. doi: 10.1016/j.jep.2023.116177. [DOI] [PubMed] [Google Scholar]
  31. Ahmadi S. M. Farhoosh R. Sharif A. Rezaie M. J. Food Sci. 2020;85:298–305. doi: 10.1111/1750-3841.14994. [DOI] [PubMed] [Google Scholar]
  32. Qi W. D. Qi W. X. Xiong D. W. Long M. Molecules. 2022;27:6545. doi: 10.3390/molecules27196545. [DOI] [PMC free article] [PubMed] [Google Scholar]
  33. Mi Y. H. Zhong L. Lu S. J. Hu P. Pan Y. Ma X. L. Yan B. H. Wei Z. H. Yang G. M. J. Ethnopharmacol. 2022;290:115066. doi: 10.1016/j.jep.2022.115066. [DOI] [PubMed] [Google Scholar]
  34. Chen L.-Y. Cheng H.-L. Kuan Y.-H. Liang T.-J. Chao Y.-Y. Lin H.-C. Biomedicines. 2021;9:761. doi: 10.3390/biomedicines9070761. [DOI] [PMC free article] [PubMed] [Google Scholar]
  35. Xu Y. Lin Z. He L. Qu Y. Z. Ouyang L. Han Y. Xu C. Duan D. Y. Oxid. Med. Cell. Longevity. 2021;2021:9674809. doi: 10.1155/2021/9674809. [DOI] [PMC free article] [PubMed] [Google Scholar] [Retracted]
  36. Xu H. M. Wen Y. Chen S. Y. Zhu L. Feng R. L. Song Z. M. Int. J. Pharm. 2020;587:119626. doi: 10.1016/j.ijpharm.2020.119626. [DOI] [PubMed] [Google Scholar]
  37. Hatlen T. J. Miller L. G. Infect. Dis. Clin. North Am. 2021;35:81–105. doi: 10.1016/j.idc.2020.10.003. [DOI] [PubMed] [Google Scholar]
  38. Mori R. Tanaka K. Shimokawa I. Dev., Growth Differ. 2018;60:306–315. doi: 10.1111/dgd.12542. [DOI] [PubMed] [Google Scholar]
  39. Morguette A. E. B. Bartolomeu-Goncalves G. Andriani G. M. Bertoncini G. E. S. Castro I. M. Spoladori L. F. A. Bertao A. M. S. Tavares E. R. Yamauchi L. M. Yamada-Ogatta S. F. Plants. 2023;12:2147. doi: 10.3390/plants12112147. [DOI] [PMC free article] [PubMed] [Google Scholar]
  40. Zulkefli N. Che Zahari C. N. M. Sayuti N. H. Kamarudin A. A. Saad N. Hamezah H. S. Bunawan H. Baharum S. N. Mediani A. Ahmed Q. U. Ismail A. F. H. Sarian M. N. Int. J. Mol. Sci. 2023;24:4607. doi: 10.3390/ijms24054607. [DOI] [PMC free article] [PubMed] [Google Scholar]
  41. Hou Y. Z. Xin M. Li Q. Q. Wu X. G. Exp. Eye Res. 2021;204:108454. doi: 10.1016/j.exer.2021.108454. [DOI] [PubMed] [Google Scholar]
  42. Jangde R. Srivastava S. Singh M. R. Singh D. Int. J. Biol. Macromol. 2018;115:1211–1217. doi: 10.1016/j.ijbiomac.2018.05.010. [DOI] [PubMed] [Google Scholar]
  43. Sychrová A. Škovranová G. Čulenová M. Fialová S. B. Molecules. 2022;27:4491. doi: 10.3390/molecules27144491. [DOI] [PMC free article] [PubMed] [Google Scholar]
  44. Nan W. H. Ding L. Chen H. J. Khan F. U. Yu L. Sui X. B. Shi X. J. Front. Pharmacol. 2018;9:826. doi: 10.3389/fphar.2018.00826. [DOI] [PMC free article] [PubMed] [Google Scholar]
  45. Syahputra R. A. Harahap U. Dalimunthe A. Nasution M. P. Satria D. Molecules. 2022;27:1320. doi: 10.3390/molecules27041320. [DOI] [PMC free article] [PubMed] [Google Scholar]
  46. Liang Y. P. He J. H. Guo B. L. ACS Nano. 2021;15:12687–12722. doi: 10.1021/acsnano.1c04206. [DOI] [PubMed] [Google Scholar]
  47. Li M. Liang Y. P. Liang Y. Q. Pan G. Y. Guo B. L. Chem. Eng. J. 2022;427:132039. doi: 10.1016/j.cej.2021.132039. [DOI] [Google Scholar]
  48. Huang Y. Bai L. Yang Y. T. Yin Z. H. Guo B. L. J. Colloid Interface Sci. 2022;608:2278–2289. doi: 10.1016/j.jcis.2021.10.131. [DOI] [PubMed] [Google Scholar]
  49. Wu K. K. Fu M. M. Zhao Y. T. Gerhard E. Li Y. Yang J. Guo J. S. Bioact. Mater. 2023;20:93–110. doi: 10.1016/j.bioactmat.2022.05.017. [DOI] [PMC free article] [PubMed] [Google Scholar]
  50. Tao B. L. Lin C. C. Yuan Z. He Y. Chen M. W. Li K. Hu J. W. Yang Y. L. Xia Z. Z. Cai K. Y. Chem. Eng. J. 2021;403:126182. doi: 10.1016/j.cej.2020.126182. [DOI] [Google Scholar]
  51. Liang Y. P. Zhao X. Hu T. L. Chen B. J. Yin Z. H. Ma P. X. Guo B. L. Small. 2019;15:e1900046. doi: 10.1002/smll.201900046. [DOI] [PubMed] [Google Scholar]

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