Biomedical Engineering Reference
In-Depth Information
Fig. 4.50.
The concept of the “whole cell sensor” [201]
control system for artificial hearts using blood catecholamine concentrations.
However, in order to use this system for actual clinical use, it is necessary to
both improve the sensitivity of the sensor system (for the detection of cate-
cholamines) to at least 10
−
9
mol/l and decrease the time delay to no more
than 10 s or so.
On-Line Measurement of Humoral Factors by Whole-Cell Sensors.
The other method that can achieve stability for the measurement of the
chemical factors in the blood and high sensitivity for specific biochemically
active substances is to use a living cell with high sensitivity for biochemical
substances as the detector (cell-based biosensor - whole-cell sensor [177]).
In the case of the measurements of plasma catecholamine concentrations,
myocardial cells, which have adrenergic receptors, can be used as a primary
transducer.
DeBusschere et al. (Stanford University) have reported that they have
succeeded in measuring catecholamine concentrations in a Hepes-buffered
culture medium using a cell-based biosensor [178].
They used spontaneously beating mouse myocardial cells as the primary
transducers. In order to measure a specific bioactive chemical agent, they used
wild-type cells and genetically engineered cells that lack a specific receptor for
the chemical agent (by developing a knockout mouse of the receptor) as the
primary transducer and made differential measurements between the results
of these two cells (Fig. 4.50).
Specifically, they used wild-type myocardial cells as the working primary
transducer for measuring
β
-adrenergic agents, and they developed genetically
engineered knockout cell lines (null mutants) of either the
β
1-adrenergic re-
ceptororthe
β
2-adrenergic receptor as the reference primary transducer.
The former cells respond to
β
-adrenergic agents (e.g., isoproterenol) and
alter their beating rate; in contrast, the latter are not affected by the
β
-
adrenergic agents. It is therefore possible to evaluate the concentration of the
β
-adrenergic agents by comparing the difference in the beating rate between
these two kinds of cells.
These authors used a 6
6 array of circular platinized iridium, gold,
or platinum microelectrodes fabricated on either glass or silicon wafers for
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