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. 2019 Oct 27;17(1):73–82. doi: 10.1111/iwj.13234

A comparative study on the cellular viability and debridement efficiency of antimicrobial‐based wound dressings

Rui Chen 1, Anne‐Marie Salisbury 1, Steven L Percival 1,✉
PMCID: PMC7949275  PMID: 31657125

Abstract

A concentrated surfactant gel containing polyhexamethylene biguanide (CSG‐PHMB) (CSG: Plurogel) was evaluated for in vitro cell cytotoxicity using the direct contact, extraction, and cell insert assays, along with its ability to breakdown artificial wound eschar and slough, compared with other clinically available wound gels: a wound gel loaded with 0.13% benzalkonium chloride (BXG) and a highly viscous gel loaded with 0.1% polyhexamethylene biguanide (PXG). Following treatment with CSG‐PHMB, BXG, and PXG at day 1, the viability of L929 and HDFa cells sharply decreased to lower than 20% of the culture media control in the direct contact assay; however, cell viability of L929 was 128.65 ± 1.41%, 99.90 ± 2.84%*, and 64.08 ± 5.99%* respectively; HDFa was 84.58 ± 10.41%, 19.54 ± 3.06%**, and 96.28 ± 33.67%, respectively, in the extraction assay. In the cell insert model, cell viability of L929 cells were 95.25 ± 0.96%, 47.49 ± 5.37%**, and 48.63 ± 7.00%**, respectively; HDFa cell viability were 92.80 ± 1.29%, 38.86 ± 4.28%**, and 49.90 ± 2.55%** (*: P < .01; **P < .001 compared with CSG‐PHMB; cell viability of culture medium without treatment at day 1 was 100%). The cell extraction model on day 1 indicated that CSG‐PHMB had higher viability of L929 cells compared with BXG. In addition, the cellular viability results indicated that CSG‐PHMB gel exhibited lower cytotoxicity when compared with BXG and PXG in the cell insert model assay. Within the in vitro debridement model, CSG‐PHMB exhibited an ability to potentially increase the loosening of the collagen matrix. The reason for this may be because of the concentrated surfactant found within the CSG‐PHMB, which has the ability to lower the surface tension, aiding in the movements of fragments and debris in the fluorescent artificial wound eschar model (fAWE).

Keywords: biofilm, cytotoxicity, debridement, surfactant, wound dressing

1. INTRODUCTION

Chronic wound infections are a major clinical problem that imposes a significant burden to the whole health care system, including patients and the society.1 Chronic infection can be induced by a patient's underlying physiological and pathological conditions, such as diabetes, or persistent microbial colonisation and biofilms.2, 3 Biofilm‐related infections are persistent and are considered to be prevalent in all chronic wounds. This has been demonstrated in a study by Levchenko.4 Zhao et al5 and Kennedy et al6 also found that most bacteria were localised in the eschar rather than at the wound surface. These studies demonstrated that eschar serves as a reservoir for microorganisms, biofilms, necrotic tissue, and inflammatory chemokines that are important factors that form a hostile local milieu hindering fibroblast and keratinocyte proliferation and migration.7, 8, 9 Eschar is difficult to remove,8, 10, 11, 12 and its presence can lead to a delay in wound healing. One of the most important tasks in chronic wound healing is to remove eschar and also slough, which are known to support biofilms.8, 13, 14

Many gel‐based wound dressings are available to the clinician, pharmacist, and patient because of their ability to provide a moist environment at the wound surface and to solubilise wound debris through autolytic or, in the case of products delivering drugs such as enzymes, enzymatic debridement technologies.15 In addition, to effectively manage microbial growth in the product while in repeat use, or on the shelf, potent antimicrobial preservatives are used. Examples of commonly used antimicrobial preservative agents include benzalkonium chloride, silver, and polyhexamethylene biguanide (PHMB). Some of these dressings have been demonstrated to have antibiofilm ability within in vitro situations.16, 17, 18 However, dressing components, as well as antimicrobial preservative agents present in these products, when present in wound dressings may also have some harmful side effects such as cytotoxicity to the skin cells.16, 17, 19 In addition, currently, there are no standard in vitro methods to evaluate the ability of wound dressing gels to breakdown eschar (debridement) and/or slough (desloughing).

In this study, we comparatively examined the cytotoxicity of three antimicrobial preservative loaded wound dressing gels, a concentrated surfactant gel loaded with PHMB (CSG‐PHMB), a highly viscous gel loaded with PHMB (PXG), and a benzalkonium chloride‐loaded gel (BXG), to determine whether these gels have effects on cellular viability by using an in vitro direct contact, modified extraction assay and cell insert assay on fibroblasts (L929) and human dermal fibroblasts (HDFa). In addition to this, we set up an in vitro test system that included a fluorescent artificial wound eschar (fAWE) to preliminarily evaluate the effects of the wound‐dressing gels on wound eschar and slough by measuring the breakdown of the main components of wound eschar: collagen, elastin, and fibrin.

2. MATERIALS AND METHODS

2.1. Test wound‐dressing

Three wound‐dressing gels with antimicrobial preservatives were investigated in this study: a concentrated surfactant gel loaded with 0.1% polyhexamethylene biguanide (CSG‐PHMB), a wound gel loaded with 0.13% benzalkonium chloride (BXG), and a highly viscous gel × loaded with 0.1% polyhexamethylene biguanide (PXG). A hydrogel without an antimicrobial preservative agent (ING [Intrasite Gel]) was used as a control.

2.2. In vitro cytotoxicity study

2.2.1. Cell culture

A mouse fibroblast cell line L929 and a primary adult HDFa (ATCC; LGC Standards, Teddington, UK) were maintained in Dulbecco's modified Eagle medium (DMEM) GlutaMAX (Gibco; ThermoFisher Scientific, Runcorn, UK) supplemented with 10% foetal bovine serum (FBS) (HyClone; GE Healthcare Life Sciences, Hatfield, UK) and 100 units/mL penicillin‐streptomycin (Life Technologies, Paisley, UK). Cells were cultured until approximately 90% confluence was achieved before undertaking tests.

2.2.2. Cytotoxicity and cell proliferation assay

Three cytotoxic assay methods were applied to study the cell viability of L929 and HDFa after treatment with CSG‐PHMB, BXG, and PXG.

Direct contact: L929 and HDFa were seeded into 24‐well plates at a concentration of 0.05 × 106/mL/well. After a 1‐day culture, 100 μL CSG‐PHMB, BXG, PXG, or ING were added to pre‐determined wells.

Extraction assay: L929 and HDFa were seeded into 24‐well plates at a concentration of 0.05 × 106/mL/well. At the same time, 100 μL CSG‐PHMB, BXG, PXG, or ING was added to 20 mL of culture medium and then stored in an incubator. After a 1‐day culture, all the media were changed with reagents dissolved the day before.

Cell insert model: L929 and HDFa were seeded into 24‐well plates at a concentration of 0.05 × 106/mL/well. After 1‐day culture, 0.4 μm 24‐well format cell culture inserts with 100 μL CSG‐PHMB, BXG, PXG, or ING were placed into pre‐determined wells. Another 1 mL culture medium was added to cell inserts.

All the medium was changed at day 4. Cell images were taken at days 1 and 7. At days 1 and 7, the cells were washed with phosphate‐buffered saline and stored at −80°C.

The qualitative evaluation of cytotoxicity was undertaken according to the international standard ISO 10993. All cells during the test periods were observed microscopically to evaluate general morphology, vacuolisation, detachment, cell lysis, and membrane integrity.

Quantitative evaluation of cytotoxicity was evaluated by cell viability with the CyQUANT cell proliferation assay kit (Molecular Probes; Invitrogen, Paisley, UK). The basis for the CyQUANT assay is the use of a proprietary green fluorescent dye (CyQUANT GR dye) that exhibits strong fluorescence enhancement when bound to cellular nucleic acids. Cells were lysed with a buffer containing CyQUANT GR dye. Fluorescence was measured using an FLX800 fluorimeter with excitation at 485 nm and emission at 530 nm. A reference standard curve using specific numbers of cells was created that allows converting fluorescence into cell number. All the cell numbers were converted to percentage of cell numbers of the DMEM group at 1 day, which was 100%. The results are presented as the mean ± SEM of n = 3.

2.3. Artificial wound eschar breakdown

2.3.1. Fibrin‐coumarin preparation

Fibrin‐coumarin was prepared by labelling fibrinogen with 7‐(Diethylamino)coumarin‐3‐carboxylic acid N‐succinimidyl ester (DCCA). Briefly, 2 mg DCCA was dissolved in 100 mL Tris buffer. Then, 200 mg fibrinogen was dissolved in 20 mL of coumarin solution. The mixture was incubated at room temperature with rotary shaking. After 1 hour, 1 mL of 50 U/mL thrombin solution was added to the above fibrinogen‐coumarin solution. After another hour, the clotted hydrogel was gently removed and repeatedly washed with water four times for 30 minutes each time, and 100% methanol was added to remove excess dye. Finally, the fibrin‐coumarin was subsequently dried and ground into a fine power using a mortar and pestle.

2.3.2. Artificial wound eschar preparation

Artificial wound eschar (AWE) was prepared by mixing 65% collagen‐fluorescein isothiocyanate (FITC), 10% fibrin‐coumarin, 10% elastin‐rhodamine, and 15% fibrinogen and then clotting with thrombin. Briefly, 650 mg collagen‐FITC, 100 mg fibrin‐coumarin, and 100 mg elastin‐rhodamine were mixed thoroughly in 10 mL Tris buffer for 10 minutes. The fibrinogen solution was prepared by dissolving 150 mg fibrinogen in 10 mL Tris buffer. The two prepared solutions were mixed thoroughly, and 0.25 mL thrombin at 50 U/mL was added to the solution and quickly mixed. The mixture was poured into a petri dish containing a 90 mm Nylon membrane filter. After 30 minutes of clotting, the AWE substrate was rinsed with deionized water for 15 minutes to remove the thrombin. The excess water was removed by tissue paper.

2.3.3. AWE breakdown model setup

An AWE breakdown model was developed in 6‐well cell culture inserts. Briefly, cut AWE substrates (ϕ = 30 mm) were gently put into 6‐well cell culture inserts, and 5 mL Tris‐buffer was added to each well of the 6‐well cell culture plate. A sketch image of the AWE breakdown model is shown in Figure 1.

Figure 1.

Figure 1

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The sketch image of the artificial wound eschar (AWE) breakdown system

In selected wells, 100 μL of the wound‐dressing gels (CSG‐PHMB, BXG, PXG, and ING) were added to the cell culture inserts. In addition, the wells without a wound dressing were used as the control group. All the plates were stored in a shaking incubator at 37°C and 30 rpm. Samples were collected at predefined time points by taking out 250 μL of solution from the 6‐well plates and then adding 250 μL of Tris buffer to the 6‐well plates. The collected samples (n = 4) were added into a black flat‐bottomed 96‐well plate and read immediately at:

Collagen‐FITC: 485‐20/520‐20

Fibrin‐Coumarin: 440‐12/480‐12

Elastin‐Rhodamine: 540‐20/590‐20

2.4. Statistical analysis

All data were presented as mean ± SD. The differences were tested for statistical significance using a one‐way ANOVA, followed by Tukey post hoc test for multiple comparisons.

3. RESULTS

3.1. Cytotoxicity study

3.1.1. Direct contact

The microscopy images of cell morphology for both L929 and HDFa cells with the direct‐contact cytotoxicity assay at days 1 and 7 are shown in Figure 2A‐D. For both L929 and HDFa, an increased number of floating cells, cell lysis, and cell shrinkage were observed in the CSG‐PHMB, BXG, and PXG, especially when observed directly under the treatment points. The characteristics of the cells observed 2 mm away from all treatments exhibited fewer morphology changes than those directly under the treatments.

Figure 2.

Figure 2

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Cell morphologies after treatment with different wound‐dressing gels by direct contact. A, L929 at day 1; B, L929 at day 7; C, human dermal fibroblasts (HDFa) at day 1; D, HDFa at day 7. “Away”: images taken at 2 mm from the treatment point; “Under”: images taken directly under the treatment point. Scale bar: 50 μm

The quantitative results (Figure 3A) showed that the cell viability of L929 sharply decreased after CSG‐PHMB (2.47 ± 1.23%), BXG (3.37 ± 0.62%), and PXG (1.10 ± 0.25%) treatments on day 1 compared with the medium control (100 ± 4.01%); after 7 days of culture, the cell viability in CSG‐PHMB (13.68 ± 3.38%), BXG (5.09 ± 0.36%), and PXG (3.41 ± 0.91%) treatments were still lower than the medium control (132.99 ± 13.83%). Figure 3B also showed a similar trend in that the cell viability of HDFa decreased significantly after the addition of CSG‐PHMB (1.10 ± 0.72%), BXG (9.16 ± 1.18%), and PXG (1.08 ± 0.03%) treatments on day 1 compared with the medium control (100 ± 4.71%). HDFa viability at day 7 in CSG‐PHMB (1.70 ± 0.14%), BXG (10.83 ± 2.58%), and PXG (1.83 ± 0.26%) treatments were still much lower than the medium control (113.74 ± 5.27%).

Figure 3.

Figure 3

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Cell viability of L929 (A) and human dermal fibroblasts (HDFa) (B), including all the “under” and “away” cells in the direct contact cytotoxicity assay after treatment with different wound‐dressing gels at days 1 and 7. All the data were obtained from three independent experiments. Error bars showed SD of the mean. Statistical analysis was carried using one‐way ANOVA comparing BXG and PXG with concentrated surfactant gel containing polyhexamethylene biguanide (CSG‐PHMB) at the same time point. The statistical significance is expressed as *: P < .01

3.1.2. Extraction assay

The microscopy images of cell morphology for both L929 and HDFa with the extraction cytotoxicity assay at days 1 and day 7 are shown in Figure 4. For both L929 and HDFa, there were no distinct morphology changes observed after CSG‐PHMB treatment. In addition, there was no distinct cell lysis and shrinkage observed, which was apparent after BXG treatment.

Figure 4.

Figure 4

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Cell morphologies after treatment with different wound‐dressing gels by extraction assay. A, L929 at day 1; B, L929 at day 7; C, human dermal fibroblasts (HDFa) at day 1; D, HDFa at day 7. Scale bar: 50 μm

Figure 5A showed that, after the CSG‐PHMB, BXG, and PXG treatments, cell viability of L929 was 128.65 ± 1.41%, 99.90 ± 2.84%*, and 64.08 ± 5.99%*, respectively, at day 1 and 172.42 ± 3.62%, 139.00 ± 4.28%*, and 173.41 ± 2.12%, respectively, at day 7. Cell viability of HDFa cell viability was 84.58 ± 10.41%, 19.54 ± 3.06%**, and 96.28 ± 33.67%, respectively, at day 1 and 135.64 ± 10.33%, 7.78 ± 0.24%**, and 127.05 ± 5.45%, respectively, at day 7. (*: P < .01; **P < .001 compared with CSG‐PHMB at the same time point; cell viability of culture medium without treatment at day 1 was 100%). The results demonstrated that CSG‐PHMB was non‐cytotoxic at 0.5% (v/v) to both L929 and HDFa; however, BXG was cytotoxic to HDFa but non‐cytotoxic to L929 in the extraction assay.

Figure 5.

Figure 5

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Cell viability of L929 (A) and human dermal fibroblasts (HDFa) (B) in extraction cytotoxicity assay after treatment with different wound‐dressing gels at days 1 and 7. All the data were obtained from three independent experiments. Error bars showed SD of the mean. Statistical analysis was carried out using one‐way ANOVA, comparing BXG, PXG, and ING with concentrated surfactant gel containing polyhexamethylene biguanide (CSG‐PHMB) at the same time point. The statistical significance is expressed as *: P < .01; **: P < .001

3.1.3. Cell insert model

The microscopy images of cell morphology for both L929 and HDFa with the cell insert model at days 1 and 7 are shown in Figure 6. For both L929 and HDFa cells, there were no distinct morphology changes observed after CSG‐PHMB treatment. However, distinct cell lysis and shrinkage were observed after BXG and PXG treatment.

Figure 6.

Figure 6

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Cell morphologies after treatment with different wound‐dressing gels by cell insert model. A, L929 at day 1; B, human dermal fibroblasts (HDFa) at day 1; C, L929 at day 7; D, HDFa at day 7. Scale bar: 50 μm

Figure 7 showed that, after CSG‐PHMB, BXG, and PXG treatments, cell viability of the L929 cell was 95.25 ± 0.96%, 47.49 ± 5.37%**, and 48.63 ± 7.00%**, respectively, at day 1 and 131.44 ± 4.53%, 27.86 ± 2.66%**, and 52.46 ± 9.96%**, respectively, at day 7. Cell viability of HDFa was 92.80 ± 1.29%, 38.86 ± 4.28%**, and 49.90 ± 2.55%**, respectively, at day 1 and 97.37 ± 6.11%, 16.91 ± 0.48%**, and 45.82 ± 5.28%**, respectively, at day 7 (**: P < .01 compared with CSG‐PHMB at the same time point; the cell viability of culture medium without treatment at day 1, viability was at 100%). The results demonstrated that CSG‐PHMB was non‐cytotoxic to both L929 and HDFa; however, BXG and PXG were cytotoxic to both L929 and HDFa in the cell insert model assay.

Figure 7.

Figure 7

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Cell viability of L929 (A) and human dermal fibroblasts (HDFa) (B) in cell insert assay after treatment with different wound‐dressing gels at days 1 and 7. All the data were obtained from three independent experiments. Error bars showed SD of the mean. Statistical analysis was carried using one‐way ANOVA, comparing BXG and PXG with concentrated surfactant gel containing polyhexamethylene biguanide (CSG‐PHMB) at same time point. The statistical significance is expressed as *: P < .01

3.2. Artificial wound eschar breakdown

The results of AWE breakdown by measuring cumulative fluorescence of collagen, elastin, and fibrin are shown in Figure 8. As collagen, elastin, and fibrin were tagged with different fluorescent dyes, the breakdown of each protein in the AWE was measured by the cumulative fluorescence of each protein debris moved out from the cell culture insert into the well. Figure 8 showed that the fluorescence intensity of collagen, elastin, and fibrin in the wells increased over time from 1 to 28 hours. Figure 8A showed that more collagen degradation occurred with the CSG‐PHMB than that of the control, BXG, PXG, and ING from 4 to 28 hours. The results indicated that CSG‐PHMB increased the exudation of small molecules from the cell culture inserts into the wells of culture plates. The reason for this is being investigated further.

Figure 8.

Figure 8

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Cumulative fluorescence changed at 1, 4, 8, 24, and 28 hours in the 6‐well plates. A, collagen; B, elastin; C, fibrin. All the data were obtained from three independent experiments. Error bars showed SD of the mean. Statistical analysis was carried out using one‐way ANOVA, comparing Control, BXG, PXG, and ING with concentrated surfactant gel containing polyhexamethylene biguanide (CSG‐PHMB) at same time point. The statistical significance is expressed as £: P < .05; *: P < .01; &: P < .0001

The results of elastin and fibrin breakdown (Figure 8B, C) showed higher variations. Figure 8B showed that CSG‐PHMB increased elastin breakdown compared with PXG and ING. There were no significant differences in fibrin breakdown among all the groups at the same time points (Figure 8C).

4. DISCUSSION

Surfactant‐based wound gels have been demonstrated in vitro to reduce biofilms by a potential dispersive effect coupled with the sequestration of microorganisms.3, 20, 21 To effectively manage growth of microorganisms during storage while in repeat use, and to also extend shelf life, adding topical antimicrobial preservative agents into wound dressings to allow safe use of non‐contaminated products in which microbes do not grow is approved practice.17, 18 Polyhexamethylene biguanide (PHMB), which has a similar structure to antimicrobial peptides (AMP), can infiltrate bacterial cell membranes and kill bacteria in a fast‐acting way, similar to AMP.22 However, PHMB and other topical antimicrobial preservative agents may also be toxic to the skin cells, which may stop skin cells growing and dividing, and as a result of cell lysis, necrosis could increase and, as a result, may delay wound healing. It is incumbent on the product formulators to ensure that the cytotoxicity to living cells is minimised, although it is clear that it probably cannot be entirely eliminated at least as determined by in vitro assays using a cell monolayer in a closed static system, which does tend to exaggerate risks to the living cells compared with cells that exist in a more complex real‐life wound milieu.23, 24 One of the objectives of this study was to evaluate a concentrated surfactant gel containing 0.1% polyhexamethylene biguanide (PHMB) (CSG‐PHMB) for in vitro cell cytotoxicity compared with some clinically available wound gels: a wound gel loaded with 0.13% benzalkonium chloride (BXG), a highly viscous gel loaded with 0.1% polyhexamethylene biguanide (PXG), and a hydrogel without an antimicrobial agent (ING).

In our previous study, we showed that concentrated surfactant gels preserved with antimicrobials (CSG) were non‐cytotoxic in all three test models.25 With the addition of 0.1% PHMB to the CSG as a preservative, as opposed to other agents in our previous experiments, this has resulted in the wound gel exhibiting some cytotoxic effects under some conditions. The cell viabilities of L929 and HDFa after treatment with CSG‐PHMB decreased in the direct contact assay, which was similar to both BXG and PXG containing topical antibacterial agents. However, it is well documented that concentrated surfactants have the ability to cause the detachment of cells from glass, and as such, this may not necessarily indicate that the dressing has killed the cells. Consequently, we are investigating the cellular viability of detached cells in further studies following treatment with the concentrated surfactant‐based gels loaded with PHMB. Interestingly, the cell viabilities were higher than 70% for L929 in the assay and L929 and HDFa in the cell insert model at day 1 after CSG‐PHMB treatment, which was found to be significantly higher than the BXG and PXG treatments. By combining all the cytotoxic results, it was found that the CSG‐PHMB dressing was lower in cytotoxicity when compared with the BXG in both the extraction assay and the cell insert model assay and PXG dressing in the cell insert model assay for both L929 and HDFa at days 1 and 7; the CSG‐PHMB dressing was also lower in cytotoxicity compared with the PXG for L929 in the extraction assay at day 1. This may be because of lower PHMB release from extraction and the cell insert to the wells where cells were growing in the culture plate. While all the cytotoxic assays are in vitro models that are often routinely used to test the cytotoxicity of the wound dressings on L929 and HDFa, the use of in vitro tests have inherent limitations and may not be truly representative of tissue repair and wound healing in wound tissue. Consequently, a combination of both in vitro and in vivo studies are needed to determine the effect of antimicrobial‐based wound dressing such as CSG‐PHMB, BXG, and PXG, on cell tissue repair and wound healing, not only on their cytotoxicity but also their effects on wound closure, inflammation, pain, and compliance on patients.25

One of the most important prerequisites in chronic wound healing is to remove eschar and slough, which helps to clean the wound bed.5, 16, 26 To encourage wound healing in chronic wounds, advanced wound dressings should have the ability to aid in the breakdown and removal of eschar (debridement) and slough (desloughing) to enhance antimicrobial and antibiofilm ability and help to clean the wound bed between dressing changes.8, 27, 28 Currently, there is no standard in vitro evaluation for eschar and slough breakdown and wound debridement. Shi et al26 placed an AWE on Franz Diffusion Cells and measured the debridement progress with Papain at concentrations of 200, 400, 800, and 1600 U/mg. The results indicated that the AWE‐Franz Diffusion Cells system can be used to predict debridement efficacy in vitro. In this study, we modified Shi's model with a new cost‐effective 6‐well plate system, which includes the lab‐made fAWE and 6‐well plate with cell culture inserts. fAWE is composed of 65% FITC‐collagen, 10% rhodamine‐elastin, 10% DCCA‐fibrin, and 15% fibrin that was freshly made by clotting fibrinogen with thrombin. The decomposition fluorescent fragments leaching out from the fAWE substrate was measured by each fluorescent dye in the well. The results of this initial study implied that the fAWE system can be used to measure the breakdown‐degradation‐decomposition of collagen, elastin, and fibrin, which are the main components of wound eschar and slough. The results of the model we used in our experiments showed that, compared with other test wound gels, surfactant‐based gels (CSG‐PHMB) increased the exudation of small fragments from cell culture inserts to culture plates. The results implied that the surfactant‐based gel helps to break down wound eschar and slough in a surfactant‐driven autolytic matter by loosening the collagen matrix. Surfactant molecules in CSG‐PHMB increased collagen movement in the AWE by reducing the adherence and entanglement of proteins by lowering the surface tension among each other. Concentrated surfactant molecules in CSG‐PHMB also formed micelles to solubilise and leach out the breakdown fragments (debris) from fAWE. Clinically, the surfactant‐driven autolytic effect helps to solubilise wound exudate and debris and aids in the wound‐cleaning process. The fAWE model used in the study greatly simplified the actual wound eschar and slough that is found in chronic wounds but does represent a very reproducible in vitro model that could be used as a standard to make comparisons between wound dressings used in wound “cleaning” and biofilm removal. Clinically, wound eschar and slough have a much more complicated structure and composition than could be simulated within an in vitro model.26, 29 The fAWE model provides a good means to standardise and compare wound dressings for debridement and slough breakdown and removal efficacy in vitro, without the unnecessary use of animals. Furthermore, as biofilms are found in slough and necrotic tissue, the model has further reaching potential as an in vitro slough‐eschar biofilm model, which is currently in development.

Within this study, the results indicated that the surfactant‐driven autolytic effect helps to solubilise wound exudate and debris, and therefore biofilm removal, and helps in cleaning the wound of barriers to wound healing. However, more in vivo studies are still required to demonstrate their efficiency clinically.

5. CONCLUSION

In this study, we first examined the effects of three antimicrobial preservative loaded wound gels on cellular viability using the direct contact, extraction assay, and cell insert model. By combining all the cytotoxic results, it was found that the CSG‐PHMB dressing was lower in cytotoxicity when compared with the BXG in both the extraction assay and cell insert model assays and PXG dressing in the cell insert model assay for both L929 and HDFa at days 1 and 7; the CSG‐PHMB dressing was also lower in cytotoxicity compared with the PXG for L929 cells in the extraction assay at day 1. In addition, a novel fAWE was set up to investigate the wound debridement efficiency of three antimicrobial preservative‐loaded wound gels. The CSG‐PHMB potentially increased the loosening of the collagen matrix, more so than BXG and PXG. The reason for this may be because of the concentrated surfactant, found within the CSG‐PHMB, with the ability to lower surface tension and aid the movements of breakdown fragments and debris in the fAWE model.

CONFLICT OF INTEREST

The authors have no conflicts of interest to report.

ACKNOWLEDGEMENTS

We thank Medline Industries for their support in this study. This study was part of a larger study funded by Medline Industries, Inc. The funder had no contribution to the design of this study, data collection, analyses, interpretation of the data, or the development and submission of the manuscript.

Chen R, Salisbury A‐M, Percival SL. A comparative study on the cellular viability and debridement efficiency of antimicrobial‐based wound dressings. Int Wound J. 2020;17:73–82. 10.1111/iwj.13234

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