Biomedical Engineering Reference
In-Depth Information
Fig. 6.4 ( a ) Change of output voltage for each pH and incubation time. ( b ) Correlation between
output voltage and pH. Each output voltage for pH was averaged in the last 10 s before changing
buffer solution. All of the measurements were performed at 25 ı
Fig. 6.5 Extended-gate field
effect transistor for
biosensing
6.2.2.1
Gold (Au) Gate Electrode
It is simple to immobilize biomolecules on Au electrode, because spacer molecules
with -SH (thiol groups) are easily tethered. DNA or antibody molecules are immobi-
lized by binding with spacer molecules on Au. However, Au surface is polarized in
solutions and a constant potential based on ion charges is not determined. Therefore,
it is effective to tether self-assembled monolayer (SAM) with both of functional
groups (-COO ,- NH 3 , and so on) with charges and -SH at each end on Au surface
for electrical stabilization of Au surface potential.
Transparent electrode is available for microscopic observation of cultured cells
as if performed using the conventional culture dish. The surface of ITO is composed
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