Biomedical Engineering Reference
In-Depth Information
The concept is demonstrated for a simultaneous immunoassay of
2-microglobulin,
IgG, bovine serum albumin, and C-reactive protein in connection with ZnS, CdS, PbS,
and CuS colloidal crystals, respectively (Fig. 14.6). These nanocrystal labels exhibit
similar sensitivity. Such electrochemical coding could be readily multiplexed and scaled
up in multiwell microtiter plates to allow simultaneous parallel detection of numerous
proteins or samples and is expected to open new opportunities for protein diagnostics
and biosecurity.
To enhance the sensitivity of the nanoparticle label-based electrochemical immunosen-
sors and immunoassays, we recently developed a novel electrochemical immunosensor
based on poly(guanine)-functionalized silica nanoparticle labels and mediator-generated
catalytic reaction [62]. Figure 14.7 (see Plate 16 for color version) schematically illus-
trates the principle of electrochemical immunosensing based on poly[G]-covered silica
NPs. Biotinylated primary antibodies are fi rst immobilized on an avidin-modifi ed elec-
trode and mouse IgG then bound onto the antibody, followed by interaction with mouse
IgG specifi c antibody-silica NPs covered with poly[G], which introduces a large amount
of guanine residues on the electrode surface. Guanines on silica NPs catalyze the oxida-
tion of Ru(bpy)
3
2
. The amplitude of the oxidation current depends on the amount of
guanine, which is related to the concentrations of sample solutions. The amplifi cation of
the catalytic signals is attributed to the attachment of a large number of guanine markers
β
(f)
(e)
(d)
(c)
3
µ
A(B-F)
6
µ
A(A)
(b)
(a)
1.2
0.3
Potential (V)
FIGURE 14.6
Typical stripping voltammograms for (a) nanocrystal-labeled antibodies and (b-f) mag-
netic bead-Ab-Ag-Ab-nanocrystal complexes. (b) Response for a solution containing dissolved ZnS anti-
β
2-microglobulin, PbS-anti-BSA, and CdS-anti-IgG conjugates (reproduced from [29] with permission).
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