Environmental Engineering Reference
In-Depth Information
gmL
1
detection in bovine milk samples. The linear dynamic range of 0.08-250
μ
gmL
1
were achieved, respectively [
38
].
In a sandwich-based assay, bio-barcode assay employs two different antibodies
being polyclonal capturing antibodies immobilized on the surface of magnetic bead
while monoclonal antibodies are conjugated on the surface of AuNPs. In the
presence of the target protein, immunosandwich is formed between the particles
and as AuNPs carry hundreds of thiolated ssDNA that can hybridize with comple-
mentary DNA, these ssDNA will be released via melting and analysed by PCR
[
39
]. Other than acting as the platform for antibody immobilization, AuNPs are also
conjugated to antibody for signal production, as in the case of lateral flow test.
and limit of detection of 0.03
μ
11.3.2.1 Lateral Flow Test
Lateral flow test or immunochromatography test (ICT) is designed to detect a
particular target in a complex mixture [
40
-
42
]. ICT consists of a consecutive series
of pads (sample pad, conjugate pad, capillary pad and absorption pad) that are able
to transport the fluid from one pad to another. Sample pad that consists of a sponge
can absorb the sample for flow initiation. The fluid is transported from one pad to
then next until it reaches the capillary pad that contains the test line. For the
detection of the specific target, the corresponding antibody against the target will
be immobilized on the surface of the test lines. In the presence of the target,
complex will form between the target, primary antibody and the secondary antibody
conjugated to Au nanoparticles (e.g. anti-rabbit or anti-mouse). AuNPs adopts a
role as the visible signal producer, as the aggregation of the AuNPs will result in the
appearance of the coloured lines (Fig.
11.5
).
Fig. 11.5 Schematics for an immunochromatography test (ICT). AuNP-antibody conjugates play
an important role. ICT consists of a consecutive sample, conjugate, capillary and absorption pads
that are able to transport the fluid from one pad to another. For the detection of the specific target,
the corresponding antibody against the target will be immobilized on the surface of the test lines.
In the presence of the target, complex will form between the target and antibody conjugated to Au
