Biomedical Engineering Reference
In-Depth Information
Figure 23.1.
Chemical structure of chitin and chitosan.
2-deoxy-D-glucose]), a copolymer of
N
-acetyl-glucosamine and
N
-
glucosamine units linked by
4) glycosidic bonds, in the pres-
ence of a hot alkali.
11
Figure 23.1 shows the chemical structure
of chitin and chitosan. This deacetylation reaction process changes
the molecular weight and degree of deacetylation of chitosan. The
molecular weight of chitin is 1.03
β
-(1
→
10
6
and that of
chitosan is 1
×
10
5
to 5
×
10
5
.
12
Depending on the source and pro-
cedure, the molecular weight of chitosan may range from 300 kDa
to over 1,000 kDa with a degree of deacetylation from around 30%
to 95%.
1
,
2
Chitosan is a partially deacetylated derivative of chitin,
and when the number of
N
-acetyl-glucosamine units is higher than
50%, the polymer is termed “chitin” generally. Conversely, when the
number of
N
-glucosamine units is higher than 50%, the term “chi-
tosan”isused.
13
However,becausechitinandchitosanarenotinsol-
uble or soluble exactly in a dilute aqueous acidic solution according
tothecriteriaof50%
N
-acetyl-glucosamineor
N
-glucosamineunits,
it can be defined that chitin and chitosan are insoluble and soluble
in a dilute aqueous acidic solution, respectively. Chitosan consisting
of
N
-acetyl-glucosamineand
N
-glucosamineintheratioofapproxi-
mately 1:1 when prepared under homogeneous reaction conditions
issolubleinwateraswellasinadiluteaqueousacidicsolution.How-
ever,chitosanwiththesameextentunderheterogeneousconditions
×
10
6
to 2.5
×
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