Biomedical Engineering Reference
In-Depth Information
Finally, the fabrication of the ITO-Pani biosensor by
Tahir et al. (2007)
involves several
steps. These include:
(a) surface treatment,
(b) Pani coating, and
(c)
antibody functionalization.
A significant amount of antigen-antibody binding was demonstrated due to the significant
drop in the current (amperometric response) before and after antigen-antibody binding. The
authors also demonstrated the feasibility of their biosensor by detecting 10
6
CCID/ml of
the BVDV in pure culture. The authors emphasize the need to further investigate the biosen-
sor parameters such as antibody concentration, Pani size, immobilization method, and incu-
bation time to enhance their biosensor performance parameters.
3.2.6 Novel Biosensor Fabrication Procedure Based on Processable Conducting
Polyaniline Nanoparticles (
Morrin et al., 2005a,b
)
Morrin et al. (2005a,b)
have recently analyzed polyaniline (Pani) nanoparticles using
dodecylbenzenesulfonic acid (DBSA) as a dopant in an enzyme biosensing application.
These authors indicate that this is a novel, highly processable, and nondiffusionable
mediating species. These authors report that these nanoparticles are readily dispersable in
aqueous media which facilitates their processability and overcomes the traditional issues
associated with Pani. The authors emphasize that their screen-printed electrodes were readily
modified by the aqueous nanoparticle dispersions. The nanoparticles, the authors claim, were
simply cast by drop-coating them onto the sensing surface. They further emphasize that no
electrochemical steps are involved, and hence their method is easily amenable to mass
production.
Morrin et al. (2005a,b)
report that polyaniline (Pani)-modified electrodes have been used in
biosensing applications (
Ramanathan et al., 1994; Shaolin and Jinqing, 1995; Killard et al.,
2001; Tatsuma et al., 2001; Halliwell et al., 2002; Raitman et al., 2002; Shi et al., 2004
). Here
Pani acts as a nondiffusional mediating species. It couples electrons directly from the enzyme
redox site to the electrode. This permits, the authors claim, a direct electrical communication
between the biomolecule and the electrode surface.
Morrin et al. (2005a,b)
claim that Pani
exhibits environmental stability, and its electrical properties may be modified by (a) the oxi-
dation of the main chain, and (b) by the degree of protonation for different applications.
Morrin et al. (2005a,b)
point out that the disadvantages in using Pani include its poor process
ability and the fact that it is a carcinogenic monomer. Also, as indicated previously, acidic
conditions are required for the formation of its highly conductive form. This, as mentioned
earlier, limits the entrapment of biological molecules, such as proteins.
