Biomedical Engineering Reference
In-Depth Information
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Figure 5.7
Impedance biosensing platform: (A) printed circuit board; (B) nanoporous
alumina membrane; and (C) silicone microfluidic chamber. (D) Changes
to the electrical double layer within each nanowell due to the binding of
the target antigens onto the nanobodies. Nanobodies are immobilized
onto the electrode sensor surface using a chemical linker. The electrode
surface is first amine functionalized using 3-aminopropyl triethoxysilane
(APTES). The alumina membrane is then soldered to the silanized (S-S)
electrode surface. Then 3,3
0
-dithiobis succinimidyl propionate (DSP) is
used to cross link the nanobodies to the electrode surface using
N-hydroxysuccnimide (NHS). The DSP (thiol linker) is to allow conju-
gation to the silanized electrode surfaces, which form the base of the
nanowells. After conjugation of the linker to the nanowell surfaces, an
aliquot of the nanobody (scFv single chain variable fragment shown) is
added, followed by addition of bovine serum albumin (BSA) to block any
unbound amine sites on the sensor surface.
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(Reprinted by kind permission of the Royal Society of Chemistry.)
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enclosed by a silicone chamber forms an inexpensive biosensing device capable
of detecting various biomolecules (Figure 5.7(c)).
The biosensor measures impedance changes to the electrical double layer at
the solid-liquid interface within the nanowells induced when target proteins
contained in the sample bind to reagents such as antibodies immobilized on the
sensor surface. Impedance measurements provide very detailed information
about the electrical changes occurring at the interfaces. When target antigens
bind immobilized antibody inside the nanowells, the double layer capacitance
changes due to the change in the surface charge concentrations. Thus, the
double layer capacitance directly correlates to the amount of binding taking
place at the solid-liquid interface and the amount of binding is directly
