Enzyme Immobilization on Chitosan-Based Supports - Chitosan Based Hydrogels: Functions and Applications - page 370

8.5.3.2.2 Chitosan/Glutamate Oxidase Complexation Films
A surprisingly strong enzyme immobilization was accomplished by the precipitation of a
mixture of polyanionic enzyme l-glutamate oxidase (GmOx) with polycationic chains of
chitosan on the surface of the platinum electrode. The good adhesion of such composite
films to the surface of platinum allowed for the construction of amperometric glutamate
biosensors with an attractive analytical performance. In particular, such biosensors dis-
played high sensitivity, low detection limit, fast response time, and good operational and
long-term stability [97].
8.5.3.2.3 Chitosan-DNA Complexation Films
Chitosan has widely been investigated for the purpose of nonviral gene delivery in the form
of DNA-chitosan complexes or as nanoparticles. Tingting et al. used a DNA-chitosan poly-
ion complex membrane as a support for the immobilization of electrocatalytic species-copper
ions, which specifically bound to dsDNA and catalyzed the hydrogen peroxide reduction.
The polyion complex membrane composed of the DNA-Cu(II) complex and chitosan was
prepared on a GCE. The DNA-Cu(II)-chitosan/GC electrode showed excellent electrocata-
lytic activity for H 2 O 2 reduction. Ascorbic acid and glucose have almost no interference to the
measurement of H 2 O 2 . In addition, the sensor exhibited good reproducibility [98].
8.5.3.3 Chitosan-Polymer PECs
8.5.3.3.1 Chitosan-PTAA LBL Self-Assembly Films
Poly(thiophene-3-acetic acid) (PTAA) has many important properties such as conductivity
in the doped state, thermochromism, photoluminescence, fluorescence, and absorption in
the UV-VIS region. Leblanc shows a way of immobilizing organophosphorus hydrolase
(OPH) using several bilayers of chitosan and negatively charged PTAA for detecting the
presence of paraoxon. This polyion cushion was held together by the electrostatic attraction
between chitosan and PTAA. OPH was then adsorbed on the five-bilayer chitosan-PTAA
system. The fluorescence property of PTAA played a key role as the ultrathin film was
monitored using emission spectroscopy. LBL adsorption allows OPH to be combined with
PTAA so that in the presence of paraoxon there would be a change in the optical properties
of PTAA, and hence, the presence of paraoxon could be detected. This five-bilayer macro-
molecular structure compared with the solid substrate rendered stability to the enzyme by
giving functional integrity in addition to the ability to react with paraoxon solutions [99].
8.5.3.3.2 Polyanionic-Modified PVA-Coated Chitosan Beads
Chemically, maleic anhydride-modified PVA showed polyanionic character and was used
for chitosan beads coating. The chitosan beads cross-linked by TPP can be used as a form
maker. Dinçer and Azmi immobilized cellulase on the modified PVA-coated chitosan
beads. ECO was selected as a convenient base catalyzed cross-linking agent. As a result of
this modification, the pH optimum of enzyme shifted from pH 4.0 to 7.0 and the immobi-
lized cellulase beads showed better pH stability than free enzyme in the neutral pH range.
The activity yield of the immobilized cellulase was found to be 87%, and it was found that
there was no change in the optimum temperature after immobilization [100].
8.5.4 Chitosan-inorganic Composites
Until now, the chitosan-inorganic hybrid support presented beads, microspheres, nano-
particles, and nanofibers. Among them, nanomaterials were the most interesting. The large