Biomedical Engineering Reference
In-Depth Information
RLS techniques using Au NPs bioconjugated with recognition
molecules are useful for the determination of proteins, mainly
because of analyte-induced increases in RLS signals of Au NPs. One
representative example is the detection of ibrinogen using Au NPs
(9.0 nm diameter) bioconjugated with goat anti-human ibrinogen
(Fig. 8.8). 44 The gold-labeled anti-human ibrinogen has two
characteristic RLS peaks at 340 nm and 560 nm (the peak at 470 nm
is due to self-producing synchronous scattering). In 0.2 M Na 2 HPO 4 -
NaH 2 PO 4 buffer (pH 6.2) containing PEG-4000, the immune reaction
between Au NPs bioconjugated with goat anti-human ibrinogen
and ibrinogen takes place, leading to the release of goat anti-human
ibrinogen from Au NP surfaces. As a result, Au NPs aggregate,
leading to great enhancements in the RLS intensity at 560 nm. The
value of I 560nm is proportional to the ibrinogen concentration over
the range from 0.027 to 1.07 μg/mL. This approach provides an LOD
of 1.14 ng/mL for ibrinogen, demonstrating great potential for the
determination of ibrinogen in human plasma.
Immunoresonance scattering using Au NPs (8-10 nm diameter)
as RLS probes is useful for the measurement of apolipoprotein AI
(ApoAI) and apolipoprotein B (ApoB). 45 In order to further improve
the intensity of RLS peaks at 560 nm, addition of PEG to the solution
is essential. The analytes induce aggregation of apolipoprotein AI
and apolipoprotein B antisera labeled Au NPs, leading to increased
RLS signals, as shown in Fig. 8.9. Because of the correlation of RLS
intensity with the size of the Au NPs, the intensity is greatly enhanced.
The intensity is proportional to the concentration in the range of
8.33-333.3 ng/L for ApoAI and 1.97-197.2 ng/L for ApoB. The LODs
are 2.04 and 0.96 μg/L for ApoAI and ApoB, respectively. This RLS
approach is practical for the determination of the two analytes in
human serum samples, with results being in good agreement with
those obtained with an immunoturbidimetric method. Similarly,
immunoresonance scattering using Au NPs (9.0 nm diameter)
bioconjugated with goat anti-human prealbumin polyclonal antibody
has proven useful for the analysis of trace prealbumin. 46 The immune
reaction between the gold-labeled antibody and prealbumin takes
place in a Na 2 HPO 4 -NaH 2 PO 4 buffer (pH 7.6) in the presence of PEG-
10000, leading to aggregation of Au NPs that have strong RLS signals
at 580 nm. The approach provides a linear relationship between the
RLS intensity and prealbumin concentration over the range from
16.67 to 666.67 ng/mL, with an LOD of 4.1 ng/mL. Homogeneous
noncompetitive immunoassays by RLS, using a commercial
 
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