Enzyme Immobilization on Chitosan-Based Supports - Chitosan Based Hydrogels: Functions and Applications - page 393

film, by which the leaching of the mediators from the composite is avoided. At the same
time, negatively charged Fe(CN) 6 3−/4− can also be tightly adsorbed within CSHMs contain-
ing robust positively charged amino groups by electrostatic interactions. CSHMs exhibit
higher sensibility, wider linear range, lower detection limit, and better reproducibility
and stability. In addition, this biosensor has strong antiinterference to some potential
interfering substances [154].
8 . 6 o u t l o o k
Chitosan/chitin, an abundant raw material, has been proved to be an excellent support for
enzyme immobilization because of its hydrophilicity, biocompatibility, and biodegradabil-
ity. Most of the enzymes immobilized on chitosan/chitin-based supports, reported in the
literature in the last decade, are presented in Table 8.2. New methods of enzyme immobi-
lization such as enzyme affinity by ChBD, MPA by epoxy activation of chitosan or binary
immobilization, and electrochemically conjugating protein with chitosan have been used,
which improved enzyme activity, stability, and selectivity. Predominantly, chitosan, pure
or forming hybrids with other polymers or inorganic materials, contains a high density of
primary amine and hydroxyl groups that can be cross-linked, chemically modified, or
grafted. The new preparation methods of chitosan-based supports, such as freezing-thaw-
ing treatment, electrodeposition, electrospinning, LBL self-assembly and cross-linking by
silylating agents, offer many opportunities for the application of immobilization enzymes,
especially biosensors via chitosan-inorganic composites.
However, some supports are still difficult to fabricate in batches, and the cost is relatively
high, which limits their application. In addition, few works have investigated the effect of
the molecular size of chitosan and the degree of deacetylation on the new process of
enzyme immobilization. These two properties influence chitosan's solubility, functional-
ity, and reactivity and hence the properties of the immobilization enzyme. As these
approaches are successfully applied to a wider range of enzymes, and production methods
are developed for larger quantities, I anticipate that the resulting biocatalytic materials
will enable new and expanded use of enzymes in practical applications such as biosensors
and bioconversions.
Acknowledgment
The author would like to thank Professor K. D. Yao who offered the opportunity to
write this chapter. The author's knowledge has certain boundaries. Therefore, there must
be many mistakes in this chapter. It is hoped that the readers will kindly point out errors.
References
1. Iyer, P. V., and Ananthanarayan, L. 2008. Enzyme stability and stabilization—Aqueous and
non-aqueous environment. Process Biochem 43: 1019-1032.