Biomedical Engineering Reference
In-Depth Information
8.5.4.3.2 LBL Self-Assembly Technology
Yuan reported a sensitive amperometric immunosensor for the preparation of carcinoem-
bryonic antigen (CEA) by several steps. First, a porous nanostructure gold (NG) film was
formed on GCE by electrochemical reduction of HAuCl 4 solution; then the nano-Au/chito-
san composite was immobilized onto the electrode because of its excellent membrane-
forming ability and finally the anti-CEA was adsorbed on the surface of the bilayer GNPs
to construct an anti-CEA/nano-Au/chitosan/NG/GCE immunosensor [124]. They
extended this methodology by using the important material nano-Pt-CHIT as the immo-
bilization matrix and selecting Hb as a model simulation enzyme in the way of the self-
assembly technology LBL to get high-sensitivity biosensor for the detection of H 2 O 2 [125].
The sensor exhibited high sensitivity, selectivity, and stability.
Piezoelectric quartz crystal impedance (PQCI) analysis is a kind of piezoelectric sensing
technique. A method for monitoring, in real time, the self-assembly of chitosan/GA/
cysteamine (CGC) on the gold surface and the immobilization of Au colloid on a CGC
membrane with PQCI was proposed by Liu et al. After the self-assembly immobilization,
the electrode surface was rich in sulfur atoms, which can form covalent bonds with gold
nanoparticles. The immobilization of human serum albumin (HAS) on Au colloid and the
association of HAS with hesperidin were investigated by PQCI. It was shown that
Au-colloid immobilization is a first-order reaction, while HSA immobilization is the sum
of two exponential functions, for example, adsorption and rearrangement [126].
8.5.4.3.3 Covalent Cross-Linking Method
In recent years, electrochemical nucleic acid biosensors have received much attention due
to their rapid response, high sensitivity, and inherent selectivity. A 20-mer single-stranded
oligodeoxyribonucleotide (ssODN) was covalently probed onto the nanocomposite elec-
trode, made up of an ITO glass surface coated with chitosan, which is bonded with car-
boxyl functionalized thiol capped GNPs (gold-mercaptopropionic acid, Au-MPA NPs).
Au-MPA NPs were covalently attached onto the chitosan backbone using EDC and NHS
as the condensing agents at room temperature. The resulting chitosan/Au-MPA suspen-
sion solution was uniformly spread on the ITO substrate by the spin coating technique and
dried at room temperature.
The ssODN probed bioactive electrode was prepared by covalent immobilization of the
ssODNs over the chitosan/Au-MPA/ITO electrode using EDC and NHS as cross-linking
agents. The obtained ssODN/chitosan/Au-MPA/ITO bioelectrode was applied in the detec-
tion of the single-stranded target complementary oligodeoxyribonucleotide (cODNs) and
exhibited an excellent sensitivity and reproducibility. The amperometric response of the
ssODN/chitosan/Au-MPA/ITO bioelectrode to the cODNs was barely affected by the mis-
matched ssODNs. It was demonstrated that chitosan-based material can be used for the
efficient and precise detection of cODNs associated with polygenic disease, namely cancer
[127].
8.5.4.4 Chitosan-Silica Hybrid Composite Material
In 1990, Braun et al. reported on the first attempt at protein encapsulation within silica
glasses. Typically, this class of silica sol-gel-based materials possesses physical rigidity,
chemical inertness, high photochemical biodegradational and thermal stability, and negli-
gible swelling in aqueous and organic solutions. Due to the inherent low-temperature pro-
cess, it provides a promising means of immobilization of bioactive molecules. However,
the brittleness of the silica sol-gel matrix is a major obstacle as an immobilization matrix
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