Biomedical Engineering Reference
In-Depth Information
disease [79-81]. h e immunosensor was prepared by entrapping horse-
radish peroxidase (HRP)-labeled IL-6 antibody into AuNP modii ed
composite membrane at a screen-printed graphite electrode. h e formed
antigen-antibody complex partly inhibited the active center of HRP, and
decreased the amount of immobilized HRP that participated in the H
2
O
2
reduction. At er the optimization of experimental parameters, the linear
range was investigated as 5-100 ng L
−1
with a detection limit of 1.0 ng L
−1
for IL-6 [82].
In another immunosensor study, an immunosensing assay was
developed for the detection of α-fetoprotein (AFP) in human serum.
An oncofetal glycoprotein with a molecular weight of approximately
70,000 Da, AFP is an important tumor marker. h e average concentra-
tion of AFP is approximately 25 ng ml
-1
in healthy human serum but
rises greatly in patients with liver cancer [83-86]. h us, the detection
of serum AFP level plays an important role in the diagnosis and man-
agement of original liver carcinoma. h e immunosensor was prepared
by immobilizing AFP antigen onto GCE modii ed by AuNP and carbon
nanotubes (CNT)-doped chitosan (AuNP/CNT/Ch) i lm. h e AuNP/
CNT hybrids were produced by one-step synthesis based on the direct
redox reaction. During the examination of the i lm, it was found that
AuNP/CNT nanohybrid acted as an electron promoter and acceler-
ated the electron transfer. Sample AFP, immobilized AFP, and alka-
line phosphatase (ALP)-labeled antibody were incubated together for
the determination based on a competitive immunoassay format. h e
amperometric response of 1-naphthyl phosphate was followed via the
bound ALP label on the modii ed GCE, at er the immunoassay reaction.
Under the optimal experimental conditions, linear range of developed
immunosensor was found in the range of 1 to 55 ng ml
-1
with a detection
limit of 0.6 ng ml
-1
[87].
Another AFP biosensor was composed of functionalized AuNPs
(SV-AuNP) which were synthesized by covalently capping the surface of
AuNP with 1,1 -bis-(2-mercapto)-4,4 - bipyridinium dibromide, a kind of
sulh yrdryl viologen (SV). First SV-AuNP was coated onto a GCE surface,
then anti-AFP was adsorbed by this prepared electrode and AFP detection
was conducted. As a result a linear range between 1.25 and 200 ng/mL with
a correlation coei cient of 0.9983 was obtained. Moreover, the detection
limit at a signal-to-noise ratio of 3 was calculated as 0.23 ng/mL under
optimal conditions [88].
h e other AFP immunosensor was prepared by attaching AuNP-
enclosed titania nanoparticle (AuTi)-labeled secondary antibody onto
