Civil Engineering Reference
In-Depth Information
Records. Lancet, 1879, II, 281). Soon at er this the use of absorbent cotton wool con-
taining antiseptics for wound dressing became very popular. In 1890, Martindale and
Westcott [27] described the preparation of absorbent wool, and stated that bleached
cotton should be alternately treated with dilute hydrochloric acid and soda solution,
and then well washed. In 1922 a supplement to the British Pharmaceutical Codex set
the i rst standards for wound dressings, and among them it described the preparation
of absorbent cotton wool. Impurities were directed to be removed from the i bers, and
then they were freed from fatty matter by being boiled for half an hour in 5 % sodium
or potassium hydroxide solution, thoroughly washed with water, bleached in 5 % chlo-
rinated lime, again washed, and then transferred to an acid bath. At er rewashing and
treating in an alkaline bath, they were i nally washed and dried. h e i bers were then
loosened mechanically and separated to make the normal carded "l eece" and a stan-
dard was set for an average staple length for the i bers of 0.7 in. However this method
of wound dressing was insui cient to prevent germs reaching the site of the wound by
means of chemical antiseptics. Also, due to the risk of air infection and volatile nature
of the antiseptics, the dressing could not be stored for a long time and sometimes it was
irritating to the tissues. h us medical researchers began to think of a perfect method
for wound dressing. In early 1879, Savory of St. Bartholomew's Hospital in London [28]
came very near to pointing the way to modern aseptic methods, even before antiseptic
surgery was fully recognized. He said that surgeons should not forget the antisepsis
of cleanliness. Later Koch and Woli hugel [29] and Vinay [30] began to try to sterilize
dressings, and Lockwood [31] expressed doubts about sterilizing towels by steam. He
described his ef orts to sterilize cotton wool by means of dry heat, and reported that the
process was not always successful. It was well known that dry heat penetrated fabrics
so slowly that they were injured before a sui ciently high temperature was attained
throughout. h e cotton wool prepared in a Lautenschlager's steam sterilizer results
an aseptic product. By using a steam disinfector which had an outside jacket through
which live steam could be passed, dressings in the inner chamber could be dried of
at er the sterilization process had been completed. A vacuum attachment to the inner
chamber was a valuable adjunct in assisting the drying. With this method of prepa-
ration, surgeons gradually became aware that aseptic cotton wool was preferable to
the older antiseptic wools as a wound dressing. Generally, dif erent standard chemical
pretreatments such as alkaline washing, bleaching, and slack-mercerization are used to
improve the sorption capacity of cellulosic-based wound dressing materials.
Modern dressings include gauzes which may be impregnated with an agent to
help sterility or accelerate healing, i lms, gels, foams, hydrocolloids, alginates, hydro-
gels and polysaccharide pastes, granules and beads. Textiles include i bers, i lments,
yarns, woven/knitted/nonwoven fabrics and articles made from natural and manmade
materials. h e most important natural materials are cotton, silk and linen. Various
polymeric materials have recently been investigated for wound dressing application,
yielding many successful outcomes, but the search for an ideal skin grat substitute with
properties and functionality similar to human skin is still continuing.
Microbial cellulose (MC), also known as bacterial cellulose synthesized by
Acetobacter xylinum bacteria, is a promising natural polymer which is chemically the
same as plant cellulose, which has become a perfect matrix for wound healing sys-
tem. Because of its unique physical and mechanical properties as well as its purity and
