Loofah sponge as an Interface dressing material

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Loofah Sponge as an Interface Dressing
Material in Negative Pressure Wound
Therapy: Results of an In Vivo Study
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Umut Tuncel, MD; Aydin Turan, MD; Fatma Markoc, MD; Unal Erkorkmaz, PhD;
Cigdem Elmas, MD; and Naci Kostakoglu, MD
Abstract
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Since the introduction of negative pressure wound therapy (NPWT), the physiological effects of various interface dressing materials have been studied. The purpose of this experimental study was to compare the use of loofah sponge to
standard polyurethane foam or a cotton gauze sponge. Three wounds, each measuring 3 cm x 3 cm, were created by
full-thickness skin excision on the dorsal sides of 24 New Zealand adult white rabbits. The rabbits were randomly divided
into four groups of six rabbits each. In group 1 (control), conventional saline-moistened gauze dressing was provided and
changed at daily intervals. The remaining groups were provided NPWT dressings at -125 mm Hg continuous pressure.
This dressing was changed every 3 days for 9 days; group 2 was provided polyurethane foam, group 3 had conventional
saline-soaked antimicrobial gauze, and group 4 had loofah sponge. Wound area measurements and histological findings
(inflammation, granulation tissue, neovascularization, and reepithelialization) were analyzed on days 3, 6, and 9. Wound
area measurements at these intervals were significantly different between the control group and study groups (P <0.05).
Granulation and neovascularization scores were also significantly different between the control and treatment groups at
day 3 (P = 0.002). No differences in any of the healing variables studied were observed between the other three dressing materials. According to scanning electron microscopy analysis of the three interface materials, the mean pore size
diameter of foam and gauze interface materials was 415.80±217.58 μm and 912.33±116.88 μm, respectively. The pore
architecture of foam was much more regular than that of gauze. The average pore size diameter of loofah sponge was
736.83±23.01 μm; pores were hierarchically located — ie, the smaller ones were usually peripheral and larger ones were
central. For this study, the central part of loofah sponge was discarded to achieve a more homogenous structure of interface material. Loofah sponge study results were similar to those using gauze or foam, but the purchase price of loofah
sponge is lower than that of currently available interface dressings. More experimental, randomized controlled studies
are needed to confirm these results.
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Keywords: in vivo, loofah, negative pressure wound therapy, gauze, foam
Index: Ostomy Wound Management 2014;60(3):37–45
Potential Conflicts of Interest: This study was supported by a grant from the Scientific Research Projects Unit,
Gaziosmanpasa University, Tokat, Turkey. KCI, San Antonio, TX, provided technical and device support.
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ccording to prospective and retrospective clinical and
experimental studies,1,2 negative pressure wound therapy (NPWT) has been widely used to facilitate healing of acute
and chronic wounds. The method has been shown to provide
a moist wound healing environment, increase granulation
tissue formation, reduce edema, and stimulate angiogenesis
and blood flow to the wound margins.3-8 Torbrand et al’s9 ret-
rospective clinical study attributed these biological effects to
the evenly distributed transduction of negative pressure to
the wound bed by a vacuum pump.
Pressure transduction is affected by the type and pore
size of the interface material and the drainage system.10-12
Since Morykwas and Argenta5 first introduced polyurethane
sponge as a wound suction interface, the physiological effects
Drs. Tuncel, Turan, and Markoc are Assistant Professors, Department of Plastic Reconstructive and Aesthetic Surgery, Gaziosmanpasa University, Faculty of
Medicine, Tokat, Turkey. Dr. Erkormaz is an Assistant Professor, Sakarya University, Faculty of Medicine, Department of Biostatistics, Sakarya, Turkey. Dr. Elmas
is an Associate Professor, Gazi Medical School, Department of Histology and Embryology, Ankara, Turkey. Dr. Kostakoglu is a Professor and Head, Department
of Plastic Reconstructive and Aesthetic Surgery, Gaziosmanpasa University. Please address correspondence to: Dr. Umut Tuncel, Faculty of Medicine, Plastic
Reconstructive and Aesthetic Surgery, Gaziosmanpasa University, 60100, Tokat, Turkey; email: [email protected].
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Ostomy Wound Management 2014;60(3):37–45
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Key Points
• Commonly used dressing interface materials for
negative pressure wound therapy (NPWT) include
foam and gauze.
• The authors of this study prepared readily available
loofah sponge for use as an interface dressing.
• In this rabbit wound model, no differences in outcomes were observed between the three interface
dressings.
• All NPWT wounds healed more expediently than daily
gauze dressing changes.
• Additional studies are needed to ascertain whether
loofah sponge can be used instead of available marketed dressings for NPWT.
Materials and Methods
This study was approved by the ethical committee on animal experiments in Gaziosmanpasa University, Tokat, Turkey. A total of 24 New Zealand adult white rabbits weighing
an average of 3.323±0.54 (range 2.4–4) kg were used. Anesthesia was induced with intramuscular injection of 20 mg/kg
ketamine hydrochloride and 2 mg/kg xylasine hydrochloride.
In all rabbits, three wounds were created by performing a 3
cm x 3 cm full-thickness skin excision that included the panniculus carnosus on their dorsal sides. Continuous sutures
were applied to the wound edges to prevent wound contraction. The rabbits then were randomly divided into four
groups of six rabbits each. Group 1 (control) wounds were
dressed with conventional saline-moistened gauze, covered
with elastic bandage, and changed at daily intervals. In the
remaining three groups, NPWT was provided by a standard
vacuum pump (V.A.C., Kinetic Concepts, Inc, San Antonio,
TX) at a continuous negative pressure of 125 mm Hg using
three different interface materials for a total of 9 days and
assessed at three-day intervals (see Figure 1). For group 2,
the interface material was hydrophobic polyurethane foam
with a pore size 400–600 μm (V.A.C. Kinetic Concepts, Inc,
San Antonio, TX). For group 3, saline-moistened antimicrobial gauze (Kerlix-AMD; Tyco, Gosport, UK) was applied
and covered by a semi-occlusive polyurethane adhesive drape
(OpSite Flexigridt, Smith & Nephew, UK). A wound drain
(V.A.C. T.R.A.C. Pad, Kinetic Concepts Inc) was connected
to the negative pressure device. In group 4, loofah sponge
was used as the interface material. Loofah sponge was purchased from a local specialty shop in Turkey and prepared for
use by removing the skin of the fruit and immersing in 2%
NaOH solution for approximately 60 minutes. The loofah fibers then were washed with distilled water until a neutral pH
was reached and dried at 60˚ C for 24 hours.32 The inner part of
the loofah sponge, which contains larger pores, was removed,
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of the interface materials have been investigated in various
experimental and clinical studies.5-7,13-15 Polyurethane foam
was used widely in the first years; the use of a gauze-based
system has been increasing in recent years.16,17 The results of
the first use of gauze as a medium was reported in Chariker et
al’s case series18 in 1989. Campbell et al19 analyzed gauze-based
NPWT on wound healing in a retrospective clinical evaluation including 30 patients, finding the overall rate of wound
volume reduction is similar to previously published data from
polyurethane foam-based NPWT systems. Malmsjö et al’s in
vivo study17 showed that gauze and foam are equally effective
at delivering negative pressure and creating mechanical deformation of the wound tissue. In that study, similar wound edge
contraction was observed at low (-50 mm Hg) and high (-175
mm Hg) levels of negative pressure. Wilkes et al’s computational study15 showed foam produces greater strain than gauze
in the tissue model at -50 and -100 mm Hg.
Experimental studies using different biomaterials suggest
foam porosity is a critical parameter that can affect cellular
activities, morphology, and depth of ingrowth into biomaterials.20,21 Devices that induce microdeformation on wound beds
may directly stimulate dermal cell proliferation, promoting
granulation tissue formation. An in vivo study22 using porous
degradable collagen-glycosaminoglycan materials demonstrated pore size is a critical parameter for inducing wound
healing and skin regeneration. In vitro and in vivo studies have
shown that mechanical forces are able to stimulate cell proliferation and differentiation.23 In an in vivo study, Pietramaggiori
et al24 found application of tension increases vascular area and
epidermal cell proliferation, both critical for enhanced repair
of tissue defects. Mechanical forces stimulate cell proliferation
and vascular remodeling in living skin.25
Loofah sponge is a hydrophilic material with a highly porous structure of interconnecting pores, a structural and physical appearance closely resembling gauze. This natural material,
a member of the Cucurbitaceae family, consists of cellulose
and lignin.26 The struts of this natural sponge are characterized
by microcellular architecture with continuous hollow microchannels that form vascular bundles and yield a multimodal
hierarchical pore system.27 Loofah is produced abundantly in
many developing countries within the tropical and subtropical
zones and primarily used for bathing and washing.26 Recently,
loofah sponges also have been applied as cell carriers in bioreactors,28 for scaffolds in tissue engineering,29 and for the development of biofiber-reinforced composites.30,31
Owing to loofah’s fibrous vascular network that can mimic
polyurethane foam and cotton gauze sponge, it was hypothesized that the complex canal system within loofah could create a porous environment for cellular integration in wound
healing and effectively deliver negative pressure to the wound
bed. The purpose of this experimental study was to compare
vascularization, reepithelialization, and collagen deposition
rates between loofah sponge and interface materials already
in use as interface dressings for NPWT.
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NPWT using a loofah sponge dressing
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Figure 1. The appearance of three interface materials.
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Figure 2. The inner part of the loofah sponge was removed because the fiber structure had larger pores.
The remaining outer shell, composed of more homogenous smaller pores, was cut open from one longitudinal side and the cylindrical shape was converted to a
rectangle.
and the remaining outer shell containing more homogenous
smaller pores was cut open on one longitudinal side and converted from a cylindrical to a rectangular shape (see Figure
2). Finally, the sponges were sterilized in an autoclave at 120˚
C for 1 hour. Before application, the sponges were moistened
with saline (see Figure 3). A drainage tube was placed over
the sponge and connected to the negative pressure pump (see
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Figure 3. Loofah sponge was moistened with saline and
applied.
Figure 4). Sleeves and swivels were used to protect the tubing
and avoid twisting. On day 9, all rabbits were sacrificed.
The surface area of the wounds was measured at 3-day
intervals using the wound tracing method. A transparency
was placed directly over the wound, and wound margins
were traced with a pen. The surface area for the tracing
was determined by counting the squares manually on
graph paper.
Scanning electron microscopy (SEM) was performed to
analyze the pore size of loofah sponge, foam, and gauze (see
Figure 5), and the pore size measurements of interface materials were made on the SEM photographs by using TPSDIG 2.00 software (FJ Rohlf, tpsDig, Digitize Landmarks and
Outlines, Version 2.0, State University of New York-Stoney
Brook, Stoney Brook, NY).
One of each three wounds with its surrounding skin
and underlying tissue was excised en bloc at days 3, 6, and
9 for histological evaluation. The tissue samples, including
wound ulcer border and center, were fixed in 10% formaldehyde solution and processed for paraffin embedding; 5-µm
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thick sections were obtained and stained with hematoxylin
and eosin (H&E) for light microscopic analysis. Inflammation,
granulation tissue, neovascularization, and reepithelialization
were evaluated and semiquantitatively scored according to
the system suggested by Abramov et al.33 Each parameter was
scored independently, and a grade between 0 and 3 was given
(see Table 1).
Inflammation was defined as acute (including neutrophils) or chronic (including lymphocytes and plasma cells)
and scored as 0 = no inflammatory cells, 1 = scant, 2 = moderate, and 3 = severe inflammation.
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Figure 4. The drainage tube was connected over the
sponge so an airtight seal dressing was achieved, and
the system was connected to the negative pressure
pump.
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The amount of granulation tissue was scored as 0 = none,
1 = scant, 2 = moderate, and 3 = marked. This tissue also was
noted as to whether it was smooth or coarse.
Neovascularization was evaluated by counting the vessels
in four adjacent areas at high power (x400), and the average
vessel count was determined for each tissue. Neovascularization was scored as 0 = no neovascularization, 1 = less than
five vessels, 2 = six to 10 vessels, and 3 = more than 10 vessels.
Reepithelialization was scored as score 0 = no reepithelialization; 1 = partial reepithelialization of the wound surface, initiation of squamous reepithelialization with creating
epithelial buds from the wound border; 2 = complete but
immature reepithelialization of the wound surface and thin,
irregular, full reconstruction of epithelium with inadequate
quality and organization; and 3 = complete and mature reepithelialization of the wound surface and regular, complete
reconstruction of epithelium with adequate quality and organization like normal squamous epithelium.
To detect fibrosis, specimens were stained with Masson’s
trichrome (MTC). Fibrosis was scored as 0 = no fibrosis; 1 =
minimal, loose fibrous tissue; 2 = moderate; and 3 = severe
and dense fibrosis.
Statistical collection and analysis. Wound areas were
presented as mean ± standard deviation. Pearson’s chisquare test was used to compare the categorical data
among groups. Kruskal-Wallis analysis of variance was
used to compare the wound areas among groups. For
post-hoc comparisons between the pair-wise groups, the
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Figure 5. Cross-sectional scanning electron microscopy micrographs of the cotton gauze (G), the polyurethane
foam (F), and loofah sponge (L).
Table 1. Wound assessment variables scores
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Score
Acute
Granulation
Neovascularization
inflammation tissue formation
Reepithelialization
Collagen
deposition
0
None
None
None
None
None
1
Mild
Mild
<5 vessel/HPF
Mild
Minimal, loose
2
Moderate
Moderate
6-10/HPF
Complete but immature or thin
Moderate
3
Severe
Severe
>10/HPF
Complete and mature
Severe and dense
HPF=high-powered field
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NPWT using a loofah sponge dressing
Table 2. Study outcomes
Pre-Test
9
Day 3
8.35±0.49
Day 6
7.14±1.01c
Day 9
5.79±1.15
0.70±0.27
0.87±0.24
<0.001
<0.001
a,c,d,e
a,c,d,e
6 (100.0)
6 (100.0)
Day 9
4 (66.7)
2 (33.3) d,e
0.135
0.018
Day 3
2 (33.3)
6 (100.0)
6 (100.0)
6 (100.0)
Day 9
6 (100.0) d
6 (100.0)
0.018
-
Day 3
2 (33.3)
6 (100.0)
Day 6
6 (100.0)
Day 9
6 (100.0) d
d
0.018
a
0.049
5 (83.3)
6 (100.0) a
6 (100.0)
U
0.002
0.002
6 (100.0)
-
6 (100.0)
6 (100.0)
-
-
-
4 (66.0)
a
a
6 (100.0) a
0.002
-
6 (100.0)
D
6 (100.0)
T
Pg
0.049
-
0.018
Day 9
0.721
-
0.018
d
3 (50.0) d,e
-
6 (100.0) d
6 (100.0)
3 (50.0) d,e
-
6 (100.0) d
Day 6
-
-
6 (100.0)
6 (100.0)
d
6 (100.0)
6 (100.0)
6 (100.0)
2 (33.3)
0
0.002
6 (100,0)
Day 9
Day 3
0.75±0.28
6 (100.0)
Day 6
P
0.001
a,c,d,e
6 (100.0)
2 (33.3)
g
0.002
6 (100.0)
Day 3
d
4.57±0.62
3.04±0.65a,c,d
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Day 6
d
a,c
A
6 (100.0)
6 (100.0)
a
Pf
<0.001
6 (100.0)
Pg
Collagen deposition
4.07±0.88a,c,d
6 (100.0)
Pg
Epithelialization
9
a,c
Day 3
P
Neovascularization
9
5.17±0.71
a,c
Day 6
g
Granulation tissue
c,d,e
5.02±0.36
L (n=6)
3.29±0.57a,c,d
0.001
P
g
Acute inflammation
9
c
G (n=6)
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Average (SD) wound
area (cm2)
F (n=6)
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C (n=6)
d
0
6 (100.0)
6 (100.0)
6 (100.0)
d
1 (16.7)
-
6 (100.0) d
6 (100.0) d
-
0.018
0.007
0
6 (100.0)
d
6 (100.0)
d
0.002
6 (100.0)
0.895
d
d
0
d
0.002
2 (33.3)
-
6 (100.0)
d
-
6 (100.0)
d
-
0.002
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Data represent presence/absence of the factor and are shown as mean±standard deviation and n (%).
a
statistically significant difference from the control group; bstatistically significant difference from the foam group; cstatistically significant difference
from pretreatment measurement; dstatistically significant difference from day 3; estatistically significant difference from day 6; fcomparisons among
groups; gcomparisons among periods
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Bonferroni-adjusted Mann-Whitney U test was used. The
Friedman test was used to compare the four periods for
each groups. For post-hoc comparisons between the pairs of
follow-up periods, the Bonferroni-adjusted, Wilcoxon rank
sum test was used. Cochran’s Q test was used to compare the
three control periods for each group. For post-hoc comparisons between the pairs of follow-up periods, the McNemar
Test was used. Categorical variables were presented as count
and percentages. P <0.05 was considered significant. Analyses
were performed using commercial software (IBM SPSS Statistics 19, SPSS Inc, an IBM Company, Somers, NY).
Results
The application of NPWT was well-tolerated by the rabbits, and no complications with NPWT or wound fillers were
encountered during the study.
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Surface area. Wound surface area was significantly reduced in all groups when compared with the initial wound
(9 cm2). Wound area differences were statistically different at
each time point for the control versus each of the other three
groups (P = 0.002, P = 0.001, and P = 0.002 for days 3, 6, and
9, respectively), but no statistical significance was noted between the three study groups. At day 3, average surface area was
8.35±0.49 cm2 in the control group, 5.02±0.36 cm2 in group
2 (polyurethane foam), 5.17±0.71 cm2 in group 3 (antibacterial gauze), and 4.57±0.62 cm2 in group 4 (loofah sponge). At
day 6, average surface area of the wounds was 7.14±1.01 cm2
in group 1, 3.29±0.57 cm2 in group 2, 4.07±0.88 cm2 in group
3, and 3.04±0.65 cm2 in group 4. At day 9, the average surface
area of the wounds was 5.79±1.15 cm2 in the control group,
0.70±0.27 cm2 for group 2, 0.87±0.24 cm2 for group 3, and
0.75±0.28 cm2 for group 4 (see Table 2, Figures 6, 7).
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Figure 7. The appearance of the wounds at day 9.
The red arrows show nearly healed wounds. F=foam,
C=control, G=gauze, L= loofah
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Figure 6. The appearance of the wounds at day 3.
C=control, F=foam, G= gauze, L= loofah
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Granulation. The amount of granulation tissue increased
significantly in all study groups at day 3 compared to the
control group (P = 0.002). After day 3, the amount of
granulation tissue was similar, with no significant difference among the groups. Reepithelialization increased after
wounding in all groups and was complete by day 9 (see
Figure 8). In the control group, reepithelialization was immature and incomplete; in the study groups, it was mature
and complete.
Neovascularization. Neovascularization scores increased after wounding in all study groups (see Figure 9). The number of
blood vessels in the control group was <3; in the study groups,
it was 6 to 10. The difference between the control and study
groups was statistically significant at day 3 (P = 0.002). No significant difference among the groups was found at days 6 and 9.
Collagen. Collagen deposition increased after wounding
in all groups at days 6 and 9, but no significant difference was
noted among the groups (see Figure 10). However, the collagen bundles were dense and oriented in the study groups and
loose and sparse in the control group.
SEM. SEM observations confirmed similarities and differences among the interface materials. According to SEM
analysis, the mean pore size diameter of foam and gauze interface materials was 415.80±217.58 μm and 912.33±116.88
μm, respectively. However, the pore architecture of foam was
much more regular than that of gauze. Loofah sponges had
medium-sized pores (736.83±23.01 μm) among the interface
materials used in the study.
Discussion
The primary role of the interface material in wound healing is to provide optimal wound healing conditions. In general practice, polyurethane foam or moistened gauze is used
as wound filler material.34-38 Many experimental and clinical
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Figure 8. G: In the gauze group, figure shows completed
epithelium is covering the surface of the granulation tissue (H-E, x200); F: In the foam group, complete and mature epithelium is covering the surface of the granulation
tissue (H-E, x200); C: In the control group, incomplete
and thin reepithelialization at the edges of the granulation tissue in the control group and scant, thin collagen fibers (Massons trichrome, x200); L: In the loofah
group, complete thin epithelium is covering the surface
of the granulation tissue and a few inflammatory cells
with edema (H-E, x200).
studies have sought to determine which interface material
is more effective in difficult-to-heal wounds and whether
interface materials affect changes in wound characteristics
such as depth, size, and exudate.16,17,20,21,38 Different indications provide some guidance on using negative pressure with
foam or gauze and depend on types of wounds, patients,
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NPWT using a loofah sponge dressing
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Figure 9. View of 6 to 10 vessels in high power field (HE, x400) (loofah group).
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literature review39 and an in vivo study40 that the open-pore
wound filler plays a crucial role in suction device-induced
wound healing. Foam porosity is a critical parameter that
can affect cellular activities such as binding, migration, proliferation, morphology, and ingrowth into biomaterials.20
O’Brien et al21 suggested pore sizes between 20 and 120 µm
were optimal and that pores should be large enough to allow cell migration but small enough to allow cell adhesion.
Heit et al’s41 similar experimental study utilized polyurethane
foam in large (300 µm), medium (130 µm), and small (70
µm) pore size diameters to treat full-thickness wounds in
diabetic mice. In that study, the thickest granulation tissue
was obtained after large pore size treatment compared with
medium and small pore size treatments. Angiogenesis was
induced only in small and medium pore size groups. Small
and medium pore size-treated wounds showed a greater
number of proliferating cells compared with large pore sizetreated wounds. In addition, tissue ingrowth into small pore
size polyurethane foam was much lower than that of medium
and large pore size. According to Klinge et al’s in vivo study,42
the pore size of an interface material appears to be an important parameter in tissue integration. In that study, the authors concluded that small diameters theoretically will lead
to increased flow resistance and to impaired passive exchange
of the soluble components, particularly if the surface tension
of the tissue liquids is considered. Thus, it can be speculated
that tiny pores may markedly inhibit fluid transport through
the interface material. Per experimental studies,43-45 cellular
ingrowth within a sponge depends on the porosity and the
presence of fibrous structure. In an experimental study,46
larger pores were shown to increase wound surface strain,
tissue ingrowth, and transformation of contractile cells. The
medium and small pore size can be superior to large pore size
to enable the reorganization and clustering of the cells in a
granulating wound. In the current study, loofah sponge (736
µm) stimulated granulation tissue formation and neovascularization by days 6 and 9 as well as gauze (912 µm) and foam
(415 µm), with no difference among study groups.
Granulation tissue formation was observed to be more
coarse in the control and smooth in the study groups. Wound
biopsies showed similar surface undulations and small tissue
blebs, which is the result of pulling effect of NPWT into the
pores of the wound filler in all study groups. These mechanical effects (microdeformations) are thought to result in shearing forces of the wound dressing materials with NPWT, which
affects the cytoskeleton and stimulation of angiogenesis and
leads to promotion of granulation tissue formation and accelerated wound healing.47 Thus, loofah sponge exacted the same
end result as available wound fillers on the market today.
In humans, NPWT helps decrease wound volume through
active contraction and generation of granulation tissue; in
rabbits, where the skin is loose, the primary mode for wound
closure is contraction and epithelialization, even though
some granulation tissue formation occurs, usually after
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Figure 10. Moderate amount of collagen fibers are seen
under the granulation tissue in loofah group (Massons
trichrome, x200).
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and anatomical location.38 Malmsjö et al’s experimental
studies16,17 showed that gauze and foam are equally effective at delivering negative pressure and creating mechanical
deformation of the wound. According to a large review of the
literature,16-20 no differences in the degree of blood flow or
wound contraction in small wounds was observed with either foam or gauze, although polyurethane foam was found
to result in more contraction than gauze in large wounds. In
the current study, wound diameter was 9 cm2. Thus, wounds
were small and created on rabbits, where it is known wounds
heal faster than in larger animals or humans.
Current study results regarding the control, gauze, and
foam correlate with the literature on wound contraction,
granulation, and neovascularization. The use of loofah
sponge, a natural product similar in form to foam or gauze,
was found to have the same results. It has been shown in a
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chargeable equipment) did not significantly differ. The total
cost of interface materials in the present study was $1,580 for
polyurethane foam, $1,000 for cotton gauze, and $20 for loofah sponge. Because it was the same for all three interface materials, the cost of the canister (collection unit) was not taken
into consideration. The price advantage of using loofah is derived from its more basic route of supply — ie, a local store.
Manufactured products cost more, and loofah sponge can be
prepared locally for use as an interface material. It should be
noted that raw material costs of gauze or foam dressings are
probably relatively a small fraction of their commercial price
after manufacturing. Even though the business costs account
for a significant portion of the final price, it can be concluded
that loofah sponge can be an inexpensive interface material
option as compared to foam and gauze. In addition, because it
dissolves easily, it has organic (“green”) implications.
Limitations
An acute wound model was used in this study; it does not
resemble a chronic, exudating wound with bacterial contamination, which could be the case in a clinical setting. Also, performing daily dressing changes with moist gauze is known to
delay wound healing in rabbits, which also was observed in this
study. A group where no wound dressing is used or a moisture
retentive dressing could have been added to yield more clinically relevant information. In this study, a continuous 125 mm
Hg negative pressure was used in all experimental groups, a
pressure proposed by the negative pressure device company.
Additional studies with application of intermittent pressure at
different values may be useful, as would a comparison between
NPWT and more modern (moisture retentive) dressings.
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about 4 to 6 days.48 In animal studies with NPWT, the time
to complete closure is between 8 to 12 days depending on
the size of the wound.49 In the present study, the optimum
follow-up period was 9 days. At that time, the surface area of
the wounds in the study groups was significantly smaller than
that of control group, and no differences between the study
groups were seen.
Several techniques have been developed to process synthetic and natural scaffold materials into porous structures.50
These conventional fabrication techniques are defined herein
as processes that create scaffolds having a continuous, uninterrupted pore structure that lacks any long-range channeling microarchitecture. The fibrous network of loofah sponge
is mainly comprised of cellulose (60%), hemicelluloses
(30%), and lignin (10%).26,27 The tensile strength of the fibers
is due to cellulose and its compression strength to lignin.51
The netting-like, fibrovascular loofah sponge has approximately 800 µm macropores, created by rough and indented
fibers with continuous hollow microchannels.52 Cellulose, as
a bioaffinity carrier, exhibits good chemical stability, recoverability, reproducibility, and mechanical strength.53 In plant
cell walls, lignins are closely related with hydrophilic polysaccharides; they are amorphous, hydrophobic heteropolymers.
Because of their hydrophobic character, lignins make plant
cells impermeable to water.53 The presence of lignin in the
cell walls or between the fibers is known to hinder the chemical reactions of cellulose and hemicelluloses as it prevents
the permeation of water across the cell walls. Thus, loofah
sponge may be a suitable biostructure for cell immobilization and bioprocess activities. The sponge structure follows
the “tensegrity” principle — ie, an architectonical system in
which structures stabilize themselves owing to equilibrium
between opposite forces of traction and compression.54 The
surface of the fibers is rough, due to the presence of small
longitudinal and transverse stripes. In longitudinal section,
the sponge appears like a network of fibers of different diameters, more or less close together.55
The fibrous and porous network of loofah sponge is similar
to gauze and foam. It is similar to gauze in hydrophilic character, and its absorption capacity has been found to be 13.6 g/g.56
NPWT has been used for many difficult-to-heal wounds
during the last decade; however, it is still an expensive treatment modality. Wounds present a substantial cost to patients
as well as the healthcare system. The most important determinant of cost appears to be wound complications that require
hospitalization or delay hospital discharge. Reducing costs
requires a systematic focus on effective and timely diagnosis,
on planning an appropriate wound treatment, and on taking measures to prevent complications and wound-related
hospitalization.57 According to Albert et al’s prospective comparison,58 gauze- and foam-based NPWT systems both can
provide comparable wound healing; nurse perceptions of ease
of dressing changes when working with these devices and direct costs associated with the use of the devices (dressings and
44
ostomy wound management® March 2014
Conclusion
Loofah sponge was observed to have characteristics similar
to current NPWT interface materials when used in rabbits. Because of its widespread cultivation around the world and low
supply price when compared with currently marketed interface materials, loofah sponge appears to provide an accessible,
less expensive alternative as an NPWT interface dressing. Before conducting clinical studies, more experimental research
is needed on larger animal models with different negative
pressure values in order to provide more evidence that loofah
sponge can replace the conventional interface materials. n
Acknowledgement
The authors thank the KCI for technical and device support.
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