J O U R N A L O F M AT E R I A L S S C I E N C E : M AT E R I A L S I N M E D I C I N E 1 1 ( 2 0 0 0 ) 8 1 7 – 8 2 3
b-Chitin-based wound dressing containing silver
sulfurdiazine
YOUNG MOO LEE*, SEONG SOO KIM
School of Chemical Engineering, College of Engineering, Hanyang University, Seoul 133-791,
Korea
MOON HYANG PARK, KANG WON SONG
Department of Pathology, College of Medicine, Hanyang University, Seoul 133-791, Korea
YONG KIEL SUNG
Department of Chemistry, College of Natural Sciences, Dongguk University, Seoul 100-715,
Korea
IN KYU KANG
Department of Polymer Science, College of Engineering, Kyungpook National University,
Taegu 702-701, Korea
E-mail: ymlee@email.hanyang.ac.kr
Physical and biological properties of some wound dressing materials based on b-chitin were
studied. Water vapor transmission rates (WVTR), oxygen permeabilities and biodegradation
kinetics were examined for film-type samples. WVTR of samples was in the range 2400–
2800 g/m
2
/day. However, oxygen permeabilities of the samples were relatively low. To
improve oxygen permeabilities, porous sponge-type wound dressing materials were
prepared. In addition, these sponge-type samples contained antimicrobial agents, silver
sulfadiazine (AgSD), in order to prevent bacteria infection on a wound surface. Anti-
microbacterial tests on agar plate were carried out to confirm the bactericidal capacity of
present materials. These materials impregnating AgSD had the complete bactericidal
capacity against pseudomonas aeruginosa up to 7 days. Finally, a wound healing effect of
b–chitin-based semi-interpenetrating polymer networks was evaluated from the animal test
using the wistar rat in vivo. Histological studies confirm the proliferation of fibroblasts in the
wound bed and a distinct reduction in infectious cells.
# 2000 Kluwer Academic Publishers
1. Introduction
In the treatment of burn wounds or extensive skin loss,
there has been a need to search for a novel method during
the past decades. Various natural and synthetic polymers
with good biocompatibility have been used in order to
develop wound dressing materials. Many types of
materials, including traditional absorbent or impregnated
dressings, synthetic dressings such as semipermeable
films, foam dressings, hydrogels, hydrocolloids and
xerogels and biological dressings created wholly or in
part from human or animal tissue, are currently applied to
lesions characterized by skin loss [1]. The objective of
the wound dressing material employed is to accelerate
wound healing by preventing fluid loss and bacteria
infection.
Generally, if severe burns or extensive skin loss have
taken place, a large amount of fluid loss and bacteria
infection leads to serious results. Therefore, among the
general properties required for a successful burn wound
covering, control of evaporative water loss and preven-
tion of bacteria infection are the most important factors.
As the wound suface contains relatively more water, it is
necessary to evaporate water through the wound
covering in order for the covering to adhere to the
wound surface. In addition, exudates between the wound
and covering result in infection. Acute inflammatory
cells keep the wound from healing. Therefore, anti-
microbial agent-impregnated materials are required and
wound dressing materials developed in recent years meet
these requirements [2, 3].
Recently, a wound dressing materials using poly-
(amino acid) was successfully developed. Kuroyanagi et
al. prepared poly(L-leucine) sponge (XEMEX Epicuel
R
)
impregnating antimicrobial agent [4]. This material
effectively controlled evaporative water loss or body
fluid and supressed bacteria infection. Biobrane
R
by Hall
Woodroof, Inc. is a composite of ultra thin silicone
rubber and ultramicro nylon knit containing collagen [5].
It had flexibilty, elasticity and adherence. The permea-
tion capacity of an antimicrobial agent through lesion is
one of the critical features. It was reported that wound
dressing materials using chitin facilitated wound healing
*Author to whom all correspondence should be addressed.
0957–4530 # 2000 Kluwer Academic Publishers 817

in clinical cases [6]. Beschitin W
R
commercialized by
Unitika in Japan is a non-woven fabric type of a-chitin.
For an ideal wound dressing, consequently, materials
should have flexibility, durability, adherence, a capability
of absorbing wound debris and to protect the lesion from
dehydration. From the biological standpoint, wound
dressing materials should have the absence of anti-
genicity, local and systemic toxicity. In the engineering
respect, they should also be easy to handle and to apply,
comfortable when in place and cost-effective.
In this study, the physicochemical properties of some
b-chitin-based semi-interpenetrating polymer networks
(semi-IPNs) hydrogels synthesized in our previous
studies were investigated for wound dressing [7, 8].
The objective of the present investigation is to prepare a
novel sponge-type wound dressing material impreg-
nating antimicrobial agent. The ultimate goal of this
study is to evaluate the bactericidal capacity and wound
healing effect of these materials.
2. Experimental
2.1. Materials
Silver sulfadiazine (AgSD) was supplied by Dong Wha
Pharmaceutical Co., Ltd (Seoul, Korea). Ethyl alcohol
and acetone were purchased from Duksan
Pharmaceutical Co., Ltd. Lysozyme was a commercial
product of Sigma Co. and used without further
purification. Fine materials were selected among many
samples to investigate the physicochemical and biolo-
gical properties for wound dressing. They were PC 1–1,
PC 1–2, PC 1–3, L–6–3, C–6–3. Table I lists the
composition of the samples. See references [7] and [8]
for detailed preparation of samples.
2.2. Preparation of sponge-type wound
dressing materials impregnating AgSD
Blend solutions containing b-chitin and poly(ethylene
glycol) macromer were cast onto a glass mold and
irradiated using a 450 watt UV lamp (Ace Glass Co.), and
placed above the mold at a height of 20 cm for 1 h until
gelation occurred. At this stage, since AgSD is sensitive
to UV irradiation, care must be taken to wait for about 2 h
to prevent the degradation of AgSD. After irradiation,
AgSD was added and partially gelled solutions were
precipitated into an acetone bath for coagulation. Gels
obtained were washed in an ethanol-water (50/50 w/w)
bath. These gels were sufficiently swollen to reach an
equilibrium and to remove uncrosslinked PEG segments
in a deionized water bath. Finally, they were freeze-dried
for 2 days after freezing at ÿ 70

C.
2.3. Water vapor transmission rate (WVTR)
measurement
The film was placed between two plastic chambers and
the surface of the film was kept in contact with water.
After weighing, a cell was put in a thermostatic oven at
37

C and 51% relative humidity. During the initial test
period, weight loss was measured every hour. As the
changes in weight loss became constant, a test was
carried out every 3 h up to 24 h. Effective membrane area
was 7:065610
ÿ4
m
2
and the thickness of the membranes
between 45 to 80 mm.
2.4. In vitro biodegradation
Samples with a thickness of 45–80 mm were cut into
small pieces …1 cm6 1 cm† and immersed in 1 mg/ml of
phosphate buffer saline (PBS) lysozyme solution ( pH
7.4) in vial. The vial was stored in a constant temperature
bath maintaining 37

C. After incubation, the film was
repeatedly washed with ethanol and dried at 40

C under
reduced pressure (10
ÿ 2
mm Hg). Weight loss of the film
was measured and plotted against time.
2.5. Antibacterial test
A bactericidal capacity of sponge-type wound dressing
materials impregnating 0.4 mg AgSD cm
ÿ 2
was inves-
tigated on an agar plate. Pseudomonas aeruginosa (Ps.
a.) was seeded for inoculation followed by incubation.
An initial seeding density of Ps. a. calculated from the
McFarland nephelometer method [9] was determined to
be 1610
7
Ps. a./cm
2
. A piece …2 cm62 cm† of wound
dressing material was placed on a bacteria-seeded agar
plate and kept in an incubator at 37

C for 1–7 days. After
a given incubation time, the sample was removed and
1 cm
2
of agar beneath the sample was cut out followed by
homogenization in a sterile saline solution of 10 ml. The
resulting solution was repeatedly diluted to a 1/10
concentration. 1 ml of the dilute solution was inoculated
on a new blood agar plate. Finally, bacterial colony
formed beneath the wound dressing material was
counted. A bacterial capacity of the present study was
compared with that of the commercial products.
2.6. Animal test
A full thickness skin wound of 1 cm in diameter was
prepared by excizing the dorsum of the wistar rat. The
excized wound was covered with various wound dressing
materials with or without AgSD. Then, a sterilized elastic
band was employed to fix the materials. As a control,
vaseline gauze was applied on a skin wound. At the fifth
and twelfth postoperative day, the wistar rats were
T A B L E I Sample designation and preparation
Sample* Lactone in PEG macromer PEG macromer …wt %† b–chitin …wt %†
PC 1–1 – 50 50
PC 1–2 – 33 67
PC 1–3 – 25 75
L–6–3 D,L-lactide 25 75
L–6–3 e–caprolactone 25 75
*Molecular weight of PEG ˆ 6000.
818