Biomedical Engineering Reference
In-Depth Information
OH
HO
OH
(EtO) 3 Si(CH 2 ) 3 NH 2
2-Bromopropionyl bromide
HO
OH
Toluene, triethylamine
OH
HO
OH
Br
-
-
Br
Br
-
- -
-
Sodium styrene sulfonate
Chitosan
Layer by layer
-
-
-
Br
- -
-
-
-
Br
-
-
ATRP
-
-
- -
Br
Br
-
Br
-
Sodium styrene sulfonate
Chitosan
Figure 8.13
Schematic representation of the preparation of the silica-coated chitosan particle. (From Lei, Z. L., Bi, S. X., and
Yang, H. 2007. Food Chem 104: 577-584. With permission.)
sulfonic acid sodium salt and then redispersed in acetate buffer of pH 3.5. A chitosan
acetic acid solution was added under stirring. After 8 h, the excess polymer was removed
and the particles were washed. The SiO 2 -coated chitosan particles were cross-linked by
treating with GA. The cross-linked particles were brown in color. The pectinase immobi-
lized on the silica-coated chitosan support exhibits an improved resistance against ther-
mal and pH denaturation. The colloidal stability is not impeded by the adsorbed proteins
despite the fact that up to 247.8 mg of enzyme is adsorbed per gram of the carrier particles.
The Michaelis constant K m differs only slightly from the K m value of the native enzyme
when the amount of adsorbed enzyme is raised [136].
The authors also reported the observation of a very strong charge-controlled “spherical
polyelectrolyte brush” of the core-shell structure, which was prepared by grafting poly-
PSS, a negatively charged polyelectrolyte, from monodisperse SiO 2 nanoparticles via the
surface-initiated atom transfer radical polymerization strategy. Chitosan was adsorbed on
the “spherical polyelectrolyte brush” by the LBL assembly approach to fabricate a dual-
layer polyelectrolyte nanoparticle support for enzyme immobilization (Figure 8.13). The
silica-coated chitosan supports were treated with GA for stability in both alkaline and
acidic media. The colloidal stability was not impeded by the adsorbed proteins despite the
fact that up to 316.8 mg of enzyme was adsorbed per gram of the carrier particles. The
activity half-lives for native and bound states of enzyme were found to be 13.5 and 30 days,
respectively. Enzyme activity was found to be approximately 49.7% for immobilized
enzyme after storage for 1 month [137].
8.5.4.5 Chitosan-CNT Composite Material
CNTs exhibit promising potential within the realm of bioelectrochemistry as the matrix
to incorporate enzyme and construct biosensors. However, the poor solubility and
chemical inertness of CNTs in aqueous solution usually limit their wide applications.
Recently, chitosan has been reported to solubilize CNTs in aqueous solution for the prep-
aration of enzyme-based nanotube sensors. The CNTs-chitosan composite provides a
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