183
9
packaging material for food or in the manufacture of antibacterial textiles. The enzymatic
degradability of chitosan can also be utilized:
Catheters or threads made of chitosan can be
used which degrade on their own and do not
have to be removed in a further surgery.
The film-forming properties of chitosan formulations are also used in cosmetics: In skin
creams, for example, the skin flexibility and
water-binding capacity are increased by the formation of chitosan films. Chitosan films also
form on hair and protect it from split ends.
This special property of chitosan is based,
among other things, on the strong interaction
with proteins such as keratin, of which hair
consists (7 Chap. 19). In general, chitosan can
interact with many substances, which is specifically exploited for numerous applications. It has
already been mentioned in the case of chitin that
the chemical structure of these two polysaccharides has a particular tendency to chelate metal
cations. The chelation is based on the fact that
chitosan can coordinate via the nitrogen atom
as well as via the hydroxyl functions. The coordination depends on the pH value and the relative concentration. This can also lead to fourfold
coordination around a metal cation, such as
Cu 2+ , by two adjacent chitosan strands coordinating twice each (. Fig. 9.8). These chitosan
complexes are very stable, so that this effect can
be used to remove heavy metals from wastewater.
The formation of chelates or inclusion compounds is not limited to metal ions. Chitosan
also has strong interactions with proteins or fats.
It also forms inclusion compounds with these.
has not yet been conclusively proven, since
glucosamine does not reach the actual site of
action through oral ingestion. Glucosamine
is produced from chitin via an acid catalytic,
hydrolytic cleavage of the polymer and simultaneous deacetylation in boiling hydrochloric
acid. Glucosamine is therefore frequently
used as hydrochloride.
9.3.2 Properties and Applications
of Chitosan
Like chitin, chitosan is also a biodegradable,
biocompatible and non-toxic polymer. These
properties and the better processability of chitosan due to its solubility in organic acids
have led to the fact that chitosan has found
many applications today. A selection of different applications of chitosan is summarized in
. Table 9.3.
The solubility of chitosan in organic acids is
based on the alkali properties of chitosan: In acidic
pH < 6, chitosan is present as a polycation, so that
it is soluble in an aqueous environment. Typical
solvents are aqueous solutions of carboxylic acids
such as formic, acetic or lactic acid. However, chitosan is not soluble in sulfuric acid and phosphoric
acid. In hydrochloric or nitric acid, hydrolysis
takes place under depolymerization.
This solution behavior can be used to purify
chitosan. Chitosan can also be processed in this
way, e.g. into films or fibers (. Fig. 9.7). These
films and fibers are used, for example, as suture
material, contact lenses, dialysis membranes,
. Table 9.3 Fields of applications of chitosan
Application
Example
Biomedical and pharmaceutical
materials
Wound and burn treatment, suture material, molded parts such as contact lenses and catheters, membrane material for dialysis
Agriculture
Seed and fruit coating for slower ripening and against pests
Cosmetics
Skin and hair care products, dental and oral care products
Analytics/biochemistry
Matrix in affinity and gel permeation chromatography, matrix for immobilization of cells and enzymes
Water engineering
Wastewater treatment to remove various substances such as heavy metals, dyes, pestizides, proteins, fats, suspended matter or oil
Food and beverages
Clarifier for beverages, use as stabilizer/emulsifier, dietetic to reduce fat
absorption
Paper and textile industry
Coating of paper, production of antibacterial fibers
9.3 · Properties and Applications of Chitin and Chitosan
9
packaging material for food or in the manufacture of antibacterial textiles. The enzymatic
degradability of chitosan can also be utilized:
Catheters or threads made of chitosan can be
used which degrade on their own and do not
have to be removed in a further surgery.
The film-forming properties of chitosan formulations are also used in cosmetics: In skin
creams, for example, the skin flexibility and
water-binding capacity are increased by the formation of chitosan films. Chitosan films also
form on hair and protect it from split ends.
This special property of chitosan is based,
among other things, on the strong interaction
with proteins such as keratin, of which hair
consists (7 Chap. 19). In general, chitosan can
interact with many substances, which is specifically exploited for numerous applications. It has
already been mentioned in the case of chitin that
the chemical structure of these two polysaccharides has a particular tendency to chelate metal
cations. The chelation is based on the fact that
chitosan can coordinate via the nitrogen atom
as well as via the hydroxyl functions. The coordination depends on the pH value and the relative concentration. This can also lead to fourfold
coordination around a metal cation, such as
Cu 2+ , by two adjacent chitosan strands coordinating twice each (. Fig. 9.8). These chitosan
complexes are very stable, so that this effect can
be used to remove heavy metals from wastewater.
The formation of chelates or inclusion compounds is not limited to metal ions. Chitosan
also has strong interactions with proteins or fats.
It also forms inclusion compounds with these.
has not yet been conclusively proven, since
glucosamine does not reach the actual site of
action through oral ingestion. Glucosamine
is produced from chitin via an acid catalytic,
hydrolytic cleavage of the polymer and simultaneous deacetylation in boiling hydrochloric
acid. Glucosamine is therefore frequently
used as hydrochloride.
9.3.2 Properties and Applications
of Chitosan
Like chitin, chitosan is also a biodegradable,
biocompatible and non-toxic polymer. These
properties and the better processability of chitosan due to its solubility in organic acids
have led to the fact that chitosan has found
many applications today. A selection of different applications of chitosan is summarized in
. Table 9.3.
The solubility of chitosan in organic acids is
based on the alkali properties of chitosan: In acidic
pH < 6, chitosan is present as a polycation, so that
it is soluble in an aqueous environment. Typical
solvents are aqueous solutions of carboxylic acids
such as formic, acetic or lactic acid. However, chitosan is not soluble in sulfuric acid and phosphoric
acid. In hydrochloric or nitric acid, hydrolysis
takes place under depolymerization.
This solution behavior can be used to purify
chitosan. Chitosan can also be processed in this
way, e.g. into films or fibers (. Fig. 9.7). These
films and fibers are used, for example, as suture
material, contact lenses, dialysis membranes,
. Table 9.3 Fields of applications of chitosan
Application
Example
Biomedical and pharmaceutical
materials
Wound and burn treatment, suture material, molded parts such as contact lenses and catheters, membrane material for dialysis
Agriculture
Seed and fruit coating for slower ripening and against pests
Cosmetics
Skin and hair care products, dental and oral care products
Analytics/biochemistry
Matrix in affinity and gel permeation chromatography, matrix for immobilization of cells and enzymes
Water engineering
Wastewater treatment to remove various substances such as heavy metals, dyes, pestizides, proteins, fats, suspended matter or oil
Food and beverages
Clarifier for beverages, use as stabilizer/emulsifier, dietetic to reduce fat
absorption
Paper and textile industry
Coating of paper, production of antibacterial fibers
9.3 · Properties and Applications of Chitin and Chitosan