Superior absorption and retention properties of foam-film silver dressing versus other commercially available silver dressing
- Seung Moon Lee†1,
- Il Kyu Park†1,
- Yong Soo Kim1,
- Hyun Jung Kim1,
- Hanlim Moon2,
- Stefan Mueller2,
- Harsha Arumugam2 and
- Young-IL Jeong3Email authorView ORCID ID profile
© The Author(s). 2016
Received: 30 May 2016
Accepted: 12 July 2016
Published: 6 August 2016
The aim of this study is to investigate the physicochemical and structural properties of Medifoam®Silver and to compare with other commercially available silver-containing polyurethane (PU) foam dressing in vitro.
Surface and cross-section of four polyurethane foam dressings were assessed with field-emission scanning electron microscope. Thickness, density, tensile strength, elongation, absorption rate, absorption/retention capacity and water-vapor transmission (WVT) were measured to compare physical properties of various dressing materials.
Among four tested dressings, Medifoam®Silver has relatively uniform and smallest pore size in both surface and cross-section. In comparison of absorption properties with other dressing materials, Medifoam®Silver has rapid absorption rate, good absorption/retention capacity and good WVT value.
The data further suggests that Medifoam®Silver is a promising candidate for wound healing management.
KeywordsWound healing Silver-containing dressing Polyurethane foam dressing Porosity Absorption/retention
The aim of wound dressings is to promote tissue regeneration and ultimately to speed up wound healing, to reduce infections and minimize pain . The benefits of an optimal moist environment at the wound interface in terms of facilitating wound closure and spending up the healing process are well described . Wet wound dressings may provide optimal conditions not only for proliferation of healthy cells but also for bacterial growth . Furthermore, the absorption/retention performance of wet wound dressing material drives absorption of exudate and plays an important role in moisturized wound environment. Subsequently, the balanced moist environment at the wound interface is known to facilitate closure and fast healing process .
Wound infection commonly occurs from inappropriate cleansing, debridement, dressing techniques as well as exposure to contaminated sources, and represents a major barrier to wound healing . Due to potential bacterial resistance, topical use of antibiotics for non-infected wound is discouraged but still it is very commonly used . Topical silver creams and solutions have been extensively used for wound healing since they offer a broad spectrum of antimicrobial activity, less development of resistance, fewer adverse reactions, and a low risk of systemic toxicity [7, 8]. However, these agents normally require frequent application, care-intensive application/removal, and cause painful reaction in patients [8–10]. Since silver-compounds such as silver nitrate and silver sulfadiazine is known to have antibacterial activity, it has been widely used in wound healing treatment as a silver-containing dressings or topical creams [11, 12]. Many reports describe that silver-based dressings are helpful to overcome bacterial infections, to promote environment for granulation/re-epithelialization in wound area, reduce adverse effects and to facilitate wound healing [2, 3, 10, 11].
Modern silver dressings should maintain moisture balance by absorbing excess exudate and preventing the wound drying out, while conferring antibacterial protection in wounds at risk of infection [2, 4]. The physical property of foam dressing should be maintained when it is coated with silver. In our previous report, we showed that our wound dressing, Medifoam® N, has excellent physicochemical properties when compared with other dressing materials . Furthermore, we also showed that appropriate physicochemical properties of wound dressing material such as porous structure, thickness/density, tensile strength and moisture-vapor transmission rate contributed to improve performance of wound dressing material. Since silver-compound has been demonstrated in the protection of bacterial contamination and then facilitation of re-epithelialization in the wound area, we developed silver-containing wound dressing (Medifoam®Silver), it may contribute to improve efficacy of wound dressing material against contamination circumstances and to facilitate wound healing. Furthermore, excellent physicochemical proeprties of our wound dressing material may also contribute to improve efficiency of wound healing. For example, Yunoki et al., reported that physicochemical properties of wound dressing such as release of silver was contributed to antibacterial activity of wound dressing material . Furthermore, other researchers also investigated physicochemical properties and antimicrobial efficiency [15, 16].
This study was conducted to compare physicochemical properties including pore size, absorption and retention capacity, and in vitro antibacterial activities of Medifoam®Silver to those of other marekted silver-dressings.
Silver impregnated dressings such as Medifoam®Silver (Genewel Co., Ltd, South Korea), AAG (Allevyn® AG (Smith & Nephew Co. TX, USA)). MAG (Mepilex® AG (Mölnlycke Health Care Co. Sweden)) and PS (Polymem® Silver (Ferris Manufacturing Co. Illinois, USA)) were obtained or purchased from each respective company. Phosphate-buffered saline (PBS, pH 7.4, 0.01 M, with pigment (SCU656, 0.1 %, DaeBo Co. ltd, Gyeonggi-do, Korea) was purchased from Gibco (NY, USA). All organic solvents were used as HPLC grade without further purification.
Thickness and density measurements
Thickness was measured using MDH micrometer high accuracy sub-micron digimatic micrometer (CD-15CPX, Mitutoyo Co. Ltd., Kawasaki, Japan) repeatedly at least 10 times with different samples. The value of thickness was described in mm as mean ± standard deviation.
Density measurement was also repeated at least 10 times with different samples (Mean ± standard deviation).
To assess morphology of foam dressing, field-emission scanning electron microscope (FE-SEM, S-4800, Hitachi, Tokyo, Japan) was employed. Each foam dressing was cut into uniform size and then coated by platinum coater. The prepared specimens were assessed at 25 kV. In the morphology analysis, the pore size and pore size uniformity of each dressing were measured and compared. Pore size was measured directly from the photo with a ruler. At least, more than three photos were taken from different positions and used to analyze pore size measurement.
Tensile strength and elongation
D1: Initial Inter-clip Distance. D2: Inter-clip Distance at Snap.
Absorption rate was measured as follows: After dressing materials were placed onto flat surfaces, phosphate-buffered saline (PBS, pH 7.4, 0.01 M) solution was pipetted onto the wound contact layer at the height of 1.0 ± 0.5 cm. The absorption rate of PBS was measured using stopwatch, repeatedly, minimum five times. The values were expressed as mean ± standard deviation.
Absorption and retention capacity
The absorption and retention capacity was measured. Initial weight (A) and thickness (B) of dressings were measured to similar with absorption study. Once absorption rate was measured, each sample was pressed by a 5 kg weight (111209, Jongro industrial Co., Ltd., Seoul, Korea) for 20 s and then weighed again (W3). Then, the retention weight (D) was calculated with following formula: Retention capacity (g/cm2) = W3 – W1/initial specimen area (cm2). The mean absorption and retention of the samples of each product were calculated.
Water-vapor transmission (WVT) measurement
W1 : initial weight of the sample before put into the thermo-hygrostat.
W2 : weight of the sample in thermo-hygrostat after 24 h.
B : absorptive area (0.0028 m2).
All experimental data were expressed as mean ± standard deviation (S.D.). Statistical alaysis was evaluated by Student’s t test using Sigmaplot program (Sigmaplot version 11.2, Systat software, Inc., CA, USA) and p value < 0.05 was considered as statistically significant.
Physico-chemical properties of foam dressings
Pore size of foam dressings
Pore size (μm)
The morphology of foam dressings in surface and cross-section were assessed with FE-SEM as shown in Fig. 2. The morphology of surface as a wound contact layer was shown in Fig. 2A. Surface of Medifoam® Silver showed uniform and small pore size as shown in Fig. 2A(a). In the surface area, Polymem®silver had a largest pore-size, followed by Mepilex®Ag, then, by Allevyn® Ag in descending order. The pore size of the cross sections was the same in order, largest in Polymem®silver, followed by Mepilex®Ag and Allevyn® Ag. The size of pore in foam dressing is summarized in Table 1.
Absorption and retention properties of foam dressings
Antibacterial activity of silver-containing dressings
Excessive exudate in wound healing management induces delayed healing process, maceration of peri-wound skin and embarrassing leakage for the patient . The pore size and pore morphology of wound dressing material may contribute the potential of wound dressing in the wound healing process. We previously reported that small pore size. Pore structure and its uniformity of Medifoam® N is related to moisture-vapor transmission rate and fluid absorption/retention capacity, and these excellent physicochemical properties must be contributed to improve wound healing process . The smaller pore size and uniformity of the surface and cross-section preferentially affect the microenvironment of wound area with its property of capillary absorption, retention capacity, WVT for exudate. Chitrattha and Phaechamud reported that porosity and pore size significantly influenced on WVT, drug release rate and oxygen transmission rate, and these properties were deeply related to antibacterial activity .
In addition, the pore size considered to play an essential role in minimizing fibroblast/keratin ingrowth into the device and reducing secondary damage upon dressing change . Moreover, dressing material having wet and incubator-like microenvironment can provide clear advantages such as prevention of dehydration, control of bacterial penetration, and bullae formation . Medifoam®Silver features an absorptive SSD-containing polyurethane foam layer between a semi-permeable absorptive polyurethane film wound contact layer and an outer layer of breathable film. These physical properties in thickness, density as well as pore strucuture and size were designed to optimize absorption and retention properties in clinical wound healing practice. Furthermore, the absorption and retention rates for silver dressings have been limitedly reported. One study investigated the water absorption rates of four dressings (carbon fiber, hydrogel, silver nanoparticle, and Vaseline gauze) used in patients with partial-thickness burns . The absorption rates were highest with the carbon fiber dressing, with the rates of the silver nanoparticle dressing being next highest. Compared with wounds without a dressing, evaporation from dressed wounds decreases . In another study comparing various wound dressings, a nanoparticle silver dressing showed good absorptive properties, absorbing up to 30 % of its weight after 72 h in a high-humidity environment .
The current study showed the good absorption and retention capacity of Medifoam®Silver. Advanced wound dressing material having ideal physical/structural properties can effectively absorb excess exudate from wound interface, prevent dryness of wound by maintaining balanced moisture condition, and provide barrier function against bacterial infections [2, 4]. Therefore, Medifoam®Silver would have optimal performance in absorption and retention of biological solutions and secretion from actual wounds. Furthermore, Medifoam®Silver has certain tensile strength and elongation properties as shown in Fig. 3. Those were considered to be an important factor for maintaining physicochemical properties, controlling drug release/WVT/MVTR and antibacterial activity [22, 23]. The absorption and retention capacity of Medifoam®Silver was good in comparison to those of several commercially available silver dressings. Given the detrimental effects of excessive moisture loss and potential for infection in wounds, highly absorptive and moisture retentive dressings such as BETAplast, are a welcomed addition to wound management armamentarium.
When physicochemical and structural properties of Medifoam®Silver were examined, it demonstrated suitable thickness, density, tensile strength and elongation. The morphologic study of Medifoam®Silver has shown the smallest pore size and the best uniformity of pore among tested dressings in both contact layer and cross-section. It also exhibited fast absorption rate, good absorption/retention capacity and good WVT value. In addition, antibacterial activity of Medifoam®Silver was equivalent to other commercially available silver foam dressings. With its optimal physicochemical and antibacterial activity, Medifoam®Silver is expected to contribute to improved wound healing process.
Our in vitro studies give a better understanding of the results achieved with Medifoam®Silver in an uncontrolled clinical study in burn wounds . Randomized clinical trials of silver wound dressings are difficult to conduct because of the multitude of potential comparators, practices and the many types of wound to treat. Nevertheless, clinical case studies or even selected clinical trials may confirm insight from this study.
AAG, Allevyn® AG; ATCC, American Type Culture Collection; BS EN, British Standard European Norm; CFU, numbers of colonies; PBS, phosphate-buffered saline; PS, Polymem® Silver; PU, polyurethane; WVT, water-vapor transmission
This study was supported by Genewel Co. Ltd. Gyeonggi-do, Korea.
This study was funded by Genewel Co. Ltd. Gyeonggi-do, Korea.
Availability of data and materials
All data generated or analysed during this study are included in this published article
SML and IKP planned and approved protocols for experimental procedure, and prepared the report. HJK validated the experimental results. YSK participated in the in vitro antibacterial study and prepared its report. HM, SM and HA validated physicochemical study and antibacterial study. Y-ILJ controlled this study at all progression and provided medical writing support of this manuscript. All authors read and approved the final manuscript.
The authors declare that they have no competing interests.
Consent for publication
Ethics approval and consent to participate
Seung Moon Lee, II Kyu Park, Yong Soo Kim and Hyun Jung Kim are employees of Genewel Co. Ltd. Gyeonggi-do, Korea. Hanlim Moon, Stefan Mueller and Harsha Arumugam are employees of Mundipharma Pte Ltd.. Young-IL Jeong is a Consultant for Pusan National University Hospital, Busan, Republic of Korea.
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