Biomedical Engineering Reference
In-Depth Information
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COO
CO 2
OH
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O
OH
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1mg/mL HA
20 min
O
2% chitosan
20 min
1M NaOH
60°C, 16 min
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COO
OH
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CO 2
OH
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O
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O
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-
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COO
COO
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+ + +
COO
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OH
OH
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Trypsin
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CO
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Chitosan, HA ..., etc.
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COO
OH
COO
OH
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-
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COO
OH
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Trypsin
Chitosan
HA
PET
Figure 8.11
Process summary of the encapsulation of trypsin based on LBL self-assembly with oppositely charged polyelec-
trolytes on a hydrolyzed PET surface. (From Liu, Y. et al. 2006. Anal Chem 78: 801-808. With permission.)
Wang et al. reported a CKGM-chitosan immobilization system that entraps l-asparagi-
nase in semipermeable CKGM-chitosan nanocapsules. The nanocapsules were prepared
by dropping the CKGM solution with l-asparaginase into the chitosan solution through a
needle while sonicating. The matrix has semipermeability to allow the substrate and prod-
uct to pass through and to keep l-asparaginase in the matrix to prevent leaking. The immo-
bilized enzyme has better stability and activity in contrast to the native enzyme. These
studies may supply a new material for the immobilization of pH- and temperature-sensitive
enzymes [95].
8.5.3.2 Enzyme or DNA-Chitosan PECs
8.5.3.2.1 Chitosan/Horseradish Peroxidase LBL Self-Assembly Films
Adsorption of material in alternated layers is now well established for immobilizing a
variety of biomolecules in an equally varied range of applications. For example, antigens
adsorbed on films with alternating layers for biosensing had their activity preserved for
long periods of time if the layers of antigen were alternated with dendrimer layers, but not
with some polyelectrolytes. It was reported by Caseli and coworkers that HRP presents
negative net charge and can be immobilized in alternated layers with chitosan as the tem-
plate material. The four-step procedure for the production of a single pair HRP/chitosan
was repeated to yield a six-bilayer film. Although the activity in the HRP/chitosan film
was lower than in a homogeneous solution or in a Langmuir-Blodgett (LB) film investi-
gated earlier, the response was linear for a considerable length of time, which may be
advantageous for sensing hydrogen peroxide [96].
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