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References 123
functional wound dressings such as those made from alginate bers, it has been
shown that these products are not only cost-eective, but they are also proven to be
extremely benecial in terms of their ability to reduce pain, odor, and leakage from
the wounds.
References
1 Agboh, O.C. and Qin, Y. (1997). Chitin and chitosan bers. Polym Adv Technol 8:
355–365.
2 Blaine, G. (1946). The use of plastics in surgery. Lancet ccli (2): 525–528.
3 Blaine, G. (1947). Experimental observations on absorbable alginate products in
surgery. Ann Surg 125: 102–114.
4 Blaine, G. (1951). A comparative evaluation of absorbable haemostatics. Postgrad
Med J 27: 613–620.
5 Blair, S.D., Jarvis, P., Salmon, M. et al. (1990). Clinical trial of calcium alginate
haemostatic swabs. Br J Surg 77: 568–570.
6 Bray, C., Blaine, G., and Hudson, P. (1948). New treatment for burns, wounds
and haemorrhage. Nurs Mirror 86: 239–242.
7 East, G.C. and Qin, Y. (1993). Wet-spinning of chitosan and the acetylation of
chitosan bers. J Appl Polym Sci 50: 1773–1779.
8 Fraser, R. and Gilchrist, T. (1983). Sorbsan calcium alginate ber dressings in
footcare. Biomaterials 4: 222–224.
9 Gilchrist, T. and Martin, A.M. (1983). Wound treatment with Sorbsan-an alginate
ber dressing. Biomaterials 4: 317–320.
10 Groves, A.R. and Lawrence, J.C. (1986). Alginate dressing as a donor site haemo-
stat. Ann R Coll Surg Engl 68: 27–28.
11 Hinchley, H. and Murray, J. (1989). Calcium alginate dressings in community
nursing. Pract Nurs 2: 264–268.
12 Hinman, C.D. and Maibach, H. (1963). Eect of air exposure and occlusion on
experimental human skin wounds. Nature 200: 377.
13 Ho, J., Walsh, C., Yue, D. et al. (2017). Current advancements and strategies in
tissue engineering for wound healing: a comprehensive review. Adv Wound Care
6 (6): 191–209.
14 Knecht, E. and Hibbert, E. (1926). Wet spinning of chitin bers. J Soc Dye Colour
42: 343.
15 Kunike, G. (1926). Regenerated bers from chitin. J Soc Dye Colour 42: 318.
16 McMullen, D. (1991). Clinical experience with a calcium alginate dressing.
Dermatol Nurs 3 (4): 216–219.
17 Odugbesan, O. and Barnett, A.H. (1987). Use of a seaweed-based dressing in
management of leg ulcers in diabetics: a case report. Pract Diabet Int 4: 46–47.
18 Oliver, L.C. and Blaine, G. (1950). Haemostasis with absorbable alginates in neu-
rosurgical practice. Br J Surg 37: 307–310.
19 Passe, E.R.G. and Blaine, G. (1948). Alginates in endaural wound dressing.
Lancet 2: 651.
124 6 Applications of Alginate Fibers as Smart Woundcare Materials
20 Qin, Y. (2005). Superabsorbent cellulosic bers for wound management. Text
Mag 32 (1): 12–14.
21 Qin, Y. (2007). Functional Wound Dressings. Beijing: China Textile Press.
22 Qin, Y. (2007). Functional cellulosic bers for wound management. Chem Fibers
Int 1–2: 34–35.
23 Qin, Y. (2008). The preparation and characterization of chitosan wound dressings
with dierent degrees of acetylation. J Appl Polym Sci 107 (2): 993–999.
24 Qin, Y. (2016). Medical Textile Materials. Cambridge: Woodhead Publishing.
25 Qin, Y. (2022). Silver Containing Functional Wound Dressings. Beijing: China Tex-
tile Press.
26 Qin, Y., Hu, H., and Luo, A. (2006). The conversion of calcium alginate bers
into alginic acid bers and sodium alginate bers. J Appl Polym Sci 101 (6):
4216–4221.
27 Thomas, S. (1985). Use of a calcium alginate dressing. Pharm J 235: 188–190.
28 Thomas, S. (1994). Wound care update. A structured approach to the selection of
dressings. Nurs RSA 9 (4): 14–16.
29 Thomas, S. (1997). A guide to dressing selection. J Wound Care 6 (10): 479–482.
30 Turner, T.D. (1989). Development of wound dressings. Wounds 1 (3): 155–171.
31 Williams, C. (1994). Sorbsan. Br J Nurs 3: 677–680.
32 Winter, G.D. (1962). Formation of scab and the rate of epithelialization of super-
cial wounds in the skin of the young domestic pig. Nature 193: 293–294.
Further Reading
Bennett, G. and Moody, M. (1995). Wound Care for Health Professionals.London:
Chapman and Hall.
Dealey, C. (1994). The Care of Wounds. Oxford: Blackwell Science Ltd.
Leaper, D.J. and Harding, K.G. (1998). Wounds: Biology and Management. Oxford:
Oxford University Press.
Morison, M., Moatt, C., Bridel-Nixon, J. et al. (1997). Nursing Management of Chronic
Wounds.London:Mosby.
Thomas, S. (1990). Wound Management and Dressings. London: The Pharmaceutical
Press.
Wardrope, J. and Smith, J.A.R. (1992). The Management of Wounds and Burns. Oxford:
Oxford University Press.
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125
7
Absorption and Interactive Properties of Alginate Wound
Dressings
7.1 Introduction
Since Sorbsan
TM
calcium alginate wound dressing was rst commercialized in 1981,
there have been a large number of alginate wound dressings launched in the health-
care market, mainly for the treatment of medium to highly exuding wounds. There
are now more than 10typesof alginate wound dressingsavailable on theBritishDrug
Tarialone [1, 6, 18, 22]. These products dier in manyrespects. With the raw mate-
rials used for the production of bers and wound dressings, alginate is chemically
a polymeric acid composed of α-
L-guluronic acid (G) and β-D-mannuronic acid (M).
Alginate extracted from dierent types of seaweed can dier signicantly in their
G and M contents and also in the GG and MM contents. It is known that alginate
high in G and GG contents can form more rigid gels than those high in M and MM
contents, hence the dierences in G and M content can have an important eect on
the absorption and interactive properties of alginate bers and wound dressings.
Alginate bers were rst made by extruding an aqueous solution of sodium
alginate into an aqueous calcium chloride bath [17]. During the production process,
the processing conditionscan be alteredto produce bers with dierent calcium and
sodium contents. It is known that bers containing a small proportion of sodium
ions are more absorbent than pure calcium alginate bers [14, 15]. The production
process can be engineered to make alginate bers with required proportions of
calcium and sodium ions.
Alginate bers can be converted into wound dressings by using a number of tex-
tile processes. Due to its simplicity and also the high absorbency of the product,
nonwoven is the main form of alginate wound dressings. A number of nonwoven
structures such as needling, pressure rolling, and hydroentanglement have been
used for making alginate wound dressings, resulting in products with signicantly
dierent absorption capacities.
In view ofthe diversied techniques thathavebeen used for the production of algi-
nate bers and wound dressings, the absorption characteristics dier for alginate
wound dressings made from dierent raw materials in dierent processing condi-
tions, with polymer, ber, and textile structures having a signicant eect on the
performances of various types of alginate wound dressings.
Alginate Fibers and Wound Dressings: Seaweed Derived Natural Therapy, First Edition. Yimin Qin.
© 2024 WILEY-VCH GmbH. Published 2024 by WILEY-VCH GmbH.
126 7 Absorption and Interactive Properties of Alginate Wound Dressings
This chapter summarizesthe absorption and also interactive propertiesof alginate
wound dressings.
7.2 Characterization Methods
Many types of alginate wound dressings are commercially available, oering a
variety of dierent constructions and properties that are useful for the study of
the absorption and interactive properties so as to correlate the chemical/physical
structures of the alginate bers and the performance of each dressing. Seven com-
mercially available alginate dressings were used to characterize their absorption
properties. Among them, Sorbsan (Maersk Medical) is a calcium alginate dressing
made from alginate with a high mannuronate content. Tegagel
TM
(3 M) is made from
the same type of bers as Sorbsan but the bers in Tegagel are hydro-entangled to
form a nonwoven dressing, while Sorbsan is made in a loose form by pressurizing
the carded web with pressure rollers. Curasorb
TM
(Kendall Healthcare) is a type of
calcium alginate wound dressing with a high guluronate content, made by needle
punching a nonwoven felt. Kaltostat
TM
(ConvaTec) is made with a similar type of
alginate as Curasorb and is also a needled nonwoven felt, but in the Kaltostat bers,
the alginic acid is in a mixed form of calcium and sodium alginate, the sodium ions
being introduced into the bers during the production process in order to improve
the absorbency and gel-forming ability of the dressing. In addition, Algosteril
TM
from Laboratory Brothier, Urgosorb
TM
from Urgo, and Tegagen HG
TM
from 3M were
also used.
Several non-alginate wound dressings were also evaluated, which include a knit-
ted gauze made of viscose rayon continuous lament yarn (Smith & Nephew), a
woven cotton gauze (ConvaTec), a nonwoven gauze made of cotton/polyester blend
(Johnson & Johnson), and a polyester nonwoven felt (SSL International).
7.2.1 Test on Absorbency
Samples were cut to 5 cm × 5 cm sizes and conditioned at 25
∘
C and 65% relative
humidity overnight. The dressings were then weighed (W) before being placed
in plastic Petri dishes (90 mm in diameter) and wetted with 40 times their own
weight of solution A, which is an aqueous solution containing 142 mmol of sodium
chloride and 2.5 mmol of calcium chloride (British Pharmacopeia Monograph for
Alginate Dressings and Packings, 1994). The dish was then placed in a 37
∘
Coven
for 30minutes. After that, the dressing was lifted out of the solution by holding with
a forcep at one corner. The solution was left to drip for 30 s and the wet dressing
was weighed (W
1
). The sample was then placed in a centrifuge tube half lled
with knitted gauze to contain the spin-o liquid. After centrifuging at 1200 rpm
for 15 minutes, the dressing was taken out and weighed again (W
2
). Finally, the
dressing was dried to constant weight at 105
∘
C for four hours and the weight was
weighed (W
3
).
The absorption capacity of the dressing equals to (W
1
− W )/W g/g. The uid that
is held within the dressing is divided into two parts, i.e. those held in the textile
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7.2 Characterization Methods 127
structure between the bersand those heldinside the individual bers.In this exper-
iment, W
1
− W
2
is the weight of uid held between the bers while W
2
− W
3
is the
weight of uid heldwithin the bers. Theratio of (W
1
− W
2
)/W
3
and (W
2
− W
3
)/W
3
are calculated to convert the uid absorption into gram uid absorbed per gram of
dry ber, which can be used to compare dierent types of dressings.
7.2.2 Fiber Calcium and Sodium Contents
The ber calcium and sodium contents were analyzed by using atomic absorption
spectroscopy. Fibers were rst digested in concentrated sulfuric acid before tests
were carried out. The calcium and sodium contents are expressed as the percentage
of carboxylic acid groups being in calcium salt or sodium salt. This assumes
that all the carboxylic acid groups on the alginate molecular chain exist either
in calcium salt or in sodium salt. Assuming the wt/wt calcium content of the
ber is C
1
and the sodium content is C
2
, the ber calcium content equals to
[C
1
/20]/[C
1
/20 + C
2
/23] × 100%, while the ber sodium content is [C
2
/23]/[C
1
/
20 + C
2
/23] × 100% (note: one calcium ion binds with two carboxylic acid group).
7.2.3 Gel Swelling
The gel swelling abilities of the alginate bers were measured by placing 0.2 g ber
in 100 ml of either distilled water or 0.9% wt/wt aqueous sodium chloride solution
(normal saline). After onehour, the bers were separated with the contacting solu-
tion and placed in a centrifuge tube with the bottom half lled with knitted viscose
rayon fabric to contain the spin-o solution. The centrifuge was carried out at 1200
rev/minute for 15 minutes. After that, the ber (W
1
) was dried at 105
∘
Ctoconstant
weight (W
2
). The gel-swelling ratio is expressed as the ratio between the weight of
the wet sample and that of the dry sample, i.e. W
1
/W
2
.
7.2.4 Wet Integrity
The wet integrity test was carried out by placing a piece of 5 cm× 5 cm dressing in
a wide necked 250 ml conical ask. After adding 50 ml of solution A, the ask was
swirled gently for 60 s.The dressing was considered wet dispersible if the bers were
separated to leave no evidence of the original structure. It was considered wet inte-
gral if there was clear evidence of the original structure.
7.2.5 Wicking Behavior
The wicking behavior was tested on a gel blocking test kit, which was made of a
semi-spheric plastic cup with a diameter of 50 mm and a depth of 5 mm. In total,
5 ml of 1.5% aqueous sodium citrate solution was rst placed in the cup. A piece of
10 cm × 10cm dressing was then placed on topof the solution. After one minute, the
dressing was lifted up and the largest diameter on the wet circle of the dressing was
measured. Wicking is expressed as the ratio between this diameter and the diameter
of the original cup.
128 7 Absorption and Interactive Properties of Alginate Wound Dressings
7.2.6 Dry and Wet Strength
The dry and wet strength of the alginate wound dressings were tested by cutting a
strip of felt 2 cm in width from each direction of the felt. For the two directions, the
strength for the weak direction was quoted. Forthe wet strength test, thefelt was cut
and then wetted with solution A similar to the absorbency test. After 30 minutes in
a37
∘
C oven, the felt was lifted out of the solution and tested for breaking strength.
The gauge length was 50 mm and the cross-head speed was 50mm/minute.
7.3 Absorption of Wound Fluid by Alginate-Based
Wound Dressings
7.3.1 Absorption Mechanism of Alginate Wound Dressings
Alginate wound dressings have a unique absorption mechanism for wound uid.
During the production process for alginate bers, aqueous solutions of sodium
alginate are extruded via ne holes into coagulation baths usually containing
calcium chloride. Upon contact with calcium ions, sodium alginate exchanges ions
with calcium ions, and since calcium ion is a divalent metal ion capable of forming
water-insoluble calcium alginate, alginate precipitates out in the form of a swollen
gel. Upon further stretching, washing, and drying, calcium alginate bers can be
made. When in contact with wound exudate, a reverse process happens. As the
calcium alginate bers are in contact with uid containing sodium ions, part of the
calcium ions in the ber exchange with the sodium ions in the contacting uid.
Since sodium alginate is water soluble, water is drawn into the ber and the ber
swells to form a gel. This unique ion-exchange process is shown in Figure 7.1.
When alginate bers are processed into nonwoven wound dressings, absorption
of uid by the dressing takes place in two forms, i.e. the uid can either be absorbed
into the ber structure or absorbed between bers in the textile structure. By cen-
trifuging the wet dressings, it is possible to separate those liquid held between the
bers (W
1
− W
2
) from the wet bers (W
2
) and by bone drying the wet bers, it is
possible to further separate the uid held inside the ber (W
2
− W
3
) from the ber
material itself (W
3
).
In the case of a wound dressing, the fact that uid can be absorbed into the ber
structure is important in several respects. First, when uid is absorbed into the
bers, they swell as a result. As the bers expand upon swelling, the free spaces
between the bers are closed, and any bacteria that are in the textile structure or
in the wound exudate are then immobilized. This action limits wound infection
and cross-infection in a hospital ward. Second, if the uid is held between the
bers by capillary forces, it can easily migrate along the textile structure. Clinically,
this would mean the spreading of wound exudate from the wounded area to
the surrounding healthy skins also covered by the dressing, hence causing skin
maceration. Therefore, it is ideal that the dressing be capable of absorbing a large
amount of exudate, and at the same time containing the uid within the ber
structure.
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7.3 Absorption of Wound Fluid by Alginate-Based Wound Dressings 129
+
Ca
2+
During the wet-spinning process
+ Na
+
Upon in contact with wound exudate
Figure 7.1 An illustration of the ion-exchange process of alginate during fiber formation
and application.
7.3.2 Absorbency of the Various Types of Alginate Wound Dressings
In the absorption test described before, (W
1
− W )/W reects the amount of uid
retained by the wound dressings on a gram per gram basis. This test is the standard
absorbency test for alginate wound dressings. As shown in Table 7.1, the various
types of alginate wound dressings have considerably dierent absorption capabil-
ities. In the case of alginate wound dressings, the needle-punched nonwoven felt
made of calcium/sodium alginate (Kaltostat) had the highest absorbency of about
16.3 g/g, while the hydroentangled dressing made from high M calcium alginate
ber (Tegagel) has the lowest absorption capacity of about 4.8 g/g. The other two
types of dressings, i.e. the needle-punched high G felt (Curasorb) and the pressure
rolled un-needled high M felt (Sorbsan), have similar absorption capacities at about
12 g/g [14].
Tabl e 7.1 Absorption properties of commercial alginate nonwoven dressings.
Product (W
1
− W)/W (W
1
− W
2
)/W
3
(W
2
− W
3
)/W
3
(W
1
− W
2
)/(W
2
− W
3
)
Sorbsan 11.98 ± 0.55 73.7 ± 2.11 15.2 ± 0.65 4.83 ± 0.25
Kaltostat 16.30 ± 0.63 47.1 ± 1.89 14.8 ± 0.71 3.18 ± 0.12
Curasorb 12.80 ± 0.53 32.0 ± 1.22 3.70 ± 0.13 8.62 ± 0.37
Tegagel 4.80 ± 0.16 18.6 ± 0.81 10.6 ± 0.39 1.75 ± 0.11
130 7 Absorption and Interactive Properties of Alginate Wound Dressings
Tabl e 7.2 Absorption properties of non-alginate products.
Product (W
1
− W)/W (W
1
− W
2
)/W
3
(W
2
− W
3
)/W
3
(W
1
− W
2
)/(W
2
− W
3
)
Knitted gauze of
viscose rayon
lament yarn
1.88 ± 0.081 4.64 ± 0.23 2.72 ± 0.13 1.71 ± 0.10
Woven gauze 4.83 ± 0.21 11.5 ± 0.48 6.45 ± 0.29 1.78 ± 0.11
Nonwoven gauze 8.90 ± 0.34 24.0 ± 1.11 2.15 ± 0.11 11.04 ± 0.42
Nonwoven
polyester fabric
18.35 ± 0.81 67.6 ± 2.15 3.97 ± 0.16 17.01 ± 0.77
Alginate bers can be made from dierent types of alginate having dierent
guluronate and mannuronate contents, and the bers can also be made into either
calcium alginate or amixedsalt ber containing dierent proportionsofcalcium and
sodium ions. The nonwoven structure of the dressings can also be varied by adopt-
ing dierent nonwoven technologies, such as needle punching, pressure rolls, and
hydroentanglement. The needle-punched felt has the highest level of porosity while
in the hydroentangled felt, the individual bers are heavily entangled and the pore
structure is reduced. In general, the absorption capacities increase with the increase
in the porosity of the dressings and the increase in the sodium content of the bers.
Table 7.2 shows the absorption capacities of a number of non-alginate dressings.
Knitted gauze made of viscose rayon lament yarn had the lowest absorption at
about 1.88 g/g, while the nonwoven polyester fabric absorbs 18.3 g uid per gram
felt, the highest among all the dressings tested. For all the cellulosic type dress-
ings, i.e. knitted viscose rayon gauze, woven cotton gauze,and nonwoven gauze,the
absorption capacity increases with the increase in the porosity of the textile struc-
ture, in the order of knitted, woven, and nonwoven. Although alginate is a much
more hydrophilic material thanpolyester,all the nonwoven alginate dressings tested
have lower absorbencythan the polyester nonwoven fabric. Thehydrophobic nature
of the polyester bers made the nonwoven structure rigid when wet,which supports
the porous structure of the dressing to hold a large amount of uid.
7.3.3 Fluid Retention Between Fibers and Inside Fibers
By applying centrifuge to the wet dressing, the uid that is retained between the
bers in the textile structure is separated from the original dressing structure. Fur-
thermore, the uid that is retained inside the bers can be measured by drying it
o the bers. These techniques can be used to reveal the exact distribution of uid
retained by the textile structure and by the ber itself.
As shown in Table 7.1 for the absorption properties of several types of alginate
wound dressings, it is clear that for all the dressings, by far the majority of the
uid is held in the textile structure rather than in the bers. However, the ratio of
(W
1
− W
2
)/(W
2
− W
3
) diers greatly for the dierent types of dressings, indicating
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7.3 Absorption of Wound Fluid by Alginate-Based Wound Dressings 131
that the distribution of uid in the dressingvaries for thedierent types ofdressings.
(W
2
− W
3
)/W
3
reects the amount of uid held in the ber per gram of dry ber.
The highest gure comes from the high M calcium alginate ber, since it exchanges
ions readily and gels rapidly on contact with sodium-containing liquid. However,
although Sorbsan and Tegagel were made with similar high M bers, the Sorbsan
ber had a higher gel-swelling ratio thanthe Tegagelber, indicating the eectof the
nonwovenstructureon the swelling ofthebers. It is also interestingtosee the dier-
ence between Curasorb and Kaltostat. Although they are both made of high G-type
alginate, the Kaltostat ber contains about 80% calcium alginate and 20% sodium
alginate, while the Curasorb is mostly calcium alginate. Kaltostat takes about 14.8 g
solution A inside the ber per gram of dry ber, while Curasorb absorbs only 3.7 g.
In terms of the distribution of uid, Sorbsan has a (W
1
− W
2
)/(W
2
− W
3
)ratioof
4.83, while Tegagel is 1.75. The loose textile structure made Sorbsan more easy to
retain uid within the textile structure, hence its absorbency between bers is 73.7g
per gram of dry ber, while the corresponding number for Tegagel is only 18.6g/g.
Curasorb also has amuch higher (W
1
− W
2
)/(W
2
− W
3
) ratio than Kaltostat.Its rigid
structure of high Gcalcium alginate made itlessable to swell andless absorbing than
the Kaltostat dressing.
7.3.4 A Comparison of Absorption Properties Between Alginate Felt
and Rope
Compared to the felt dressings, alginate ropes are loosely assembled bers with little
ber/ber interaction. The main dierence between the felt and rope is the accessi-
bility of the individual bers tothe uid, mainly because the ropes take a cylindrical
form with the inner part of the rope further away from the uid than in the felt prod-
ucts. Table 7.3 showsthe absorption propertiesof Sorbsan ribbonand Kaltostat rope.
In general, compared to the nonwoven dressings made of the same type of bers, the
dierences in the various parameters are small.
7.3.5 Effect of Sterilization on the Absorption Properties of Alginate
Dressings
Table 7.4 shows the absorption properties of sterilized and un-sterilized algi-
nate nonwoven dressings and ropes. The sterilization is done by r-irradiation at
25 kGy. Post-sterilization, there is a signicant reduction in the (W
2
− W
3
)/W
3
parameter, indicating that the sterilization process has either made the alginate
Tabl e 7.3 Absorption behavior of alginate ropes.
Product (W
1
− W)/W (W
1
− W
2
)/W
3
(W
2
− W
3
)W
3
(W
1
− W
2
)/(W
2
− W
3
)
Sorbsan ribbon 10.85 ± 0.51 52.5 ± 2.12 13.2 ± 0.61 3.97 ± 0.21
Kaltostat rope 11.46 ± 0.48 48.6 ± 1.65 15.6 ± 0.66 3.10 ± 0.14
132 7 Absorption and Interactive Properties of Alginate Wound Dressings
Tabl e 7.4 A comparison of the absorption properties of sterile and unsterile alginate
dressings and ropes.
Product (W
1
− W)/W (W
1
− W
2
)/W
3
(W
2
− W
3
)/W
3
(W
1
− W
2
)
(W
2
− W
3
)
Un-sterilized alginate
nonwoven dressing
20.85 ± 0.85 82.4 ± 2.98 24.3 ± 0.92 3.38 ± 0.14
Sterilized alginate
nonwoven dressing
18.72 ± 0.82 82.6 ± 3.12 21.0 ± 0.87 3.93 ± 0.14
Un-sterilized alginate
rope
19.52 ± 0.95 76.3 ± 2.41 23.7 ± 1.11 3.22 ± 0.14
Sterilized alginate rope 16.57 ± 0.58 75.3 ± 2.65 17.4 ± 0.67 4.32 ± 0.21
Note: the alginate bers used in the above experiment are a mixed calcium/sodium alginate
containing about 70% calcium alginate and 30% sodium alginate.
more crystallized or cross-linked in some form, which makes it less absorbent.
Interestingly, in both the nonwoven dressing and rope, the absorption between
bers (W
1
− W
2
)/W
3
remains largely unchanged before and after sterilization,
which means that the sterilization process has little eect on the textile structure.
Since the bers absorb less after sterilization, the overall absorption capacities of
the dressings were reduced post-sterilization.
7.3.6 Effect of Guluronate and Mannuronate Contents
Table 7.5 shows the analysis results for Algosteril, Curasorb
,
and Sorbsan dressings.
All three dressingsare made of calcium alginate bers. Both Algosteril and Curasorb
are made of high G alginate, while Sorbsan is made of high M alginate. The high
G and high M type bers dier signicantly in the gel-swelling ratio in saline. As
can be seen in Table 7.5, Sorbsan had a signicantly higher saline swelling ratio
than both Algosteril and Curasorb, while the water-swelling ratios were similar for
the three types of alginate bers. This is understandable since the calcium ions are
bound more strongly with high G alginate, hence ion exchange with sodium ions in
the solution is more dicult for high G alginate ber. For high M bers, the calcium
Tabl e 7.5 Performance characteristics of three calcium alginate dressings.
Test criteria Algosteril Curasorb Sorbsan
Weight per unit area (g/m
2
) 125.55 ± 8.15 127.50 ± 5.80 125.20 ± 6.50
Absorbency (g/g) 14.27 ± 0.41 14.77 ± 0.36 16.75± 0.27
Wet integrity Integral Integral Dispersible
Gel swelling ratio in water (g/g) 1.85 ± 0.13 2.12 ± 0.12 2.14 ± 0.14
Gel swelling ratio in saline (g/g) 5.23± 0.42 4.42 ± 0.13 13.91 ± 0.77
Fiber diameter (μm) 25.25± 1.22 15.27 ± 1.68 17.4 ± 1.87
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