Biomedical Engineering Reference
In-Depth Information
the secondary transduction of the signals detected by the primary transdu-
cers. They monitored action potentials (extracellular currents) of the primary
transducer cells (both working and reference) using the microelectrodes, and
made a differential measurement of the spontaneous beating rates between
thetwotypesofcells.
Their results showed a strong increase in the spontaneous beat rate (50-
80%) of the wild-type cells, whereas the
β
1-adrenergic receptor knockout
cells exhibited only a minor response (1-5%) when a 10
M concentration of
isoproterenol (which is expected to saturate the receptors) was added to the
medium.
The main problem for the development of this system is that the knockout
of the target receptor would result in a lethal mutation in many cases and,
as a result, it would become impossible to develop the target cell lines, as
these cells are derived from the primary culture of the tissues of the knockout
mouse.
However, this technique is expected to allow on-line measurements of the
concentration of specific biochemical agents that are active to the receptors
that are made knockout. It is also expected that this measurement can be
effectively and reversibly performed in the blood or plasma, with a very high
resolution.
The authors are also developing a similar whole cell sensor system using
genetically engineered cells derived from embryonic stem cells.
μ
Summary.
At the moment, minimal detectable concentrations of both
adrenaline and noradrenaline with respect to the sensing system are still
inadequate for practical use. Stability of the measurement in blood or in
plasma is also necessary for the implementation of this sensing system.
However, novel techniques such as “whole cell sensors” and “microdialy-
sis” will allow the development of a control system for artificial heart systems
using feedback of catecholamine concentrations in blood in the near future.
4.9.2
Control of Artificial Hearts Using Autonomic
Nervous Signals
Introduction.
The nervous system, together with the humoral system, plays
a significant role in controlling the human body. Not only does it control our
voluntary movements, but it also plays an indispensable role in governing the
autonomic nervous control, which regulates the functioning of internal organs
to optimum levels in accordance with external conditions. The development
of a man-machine interface, which can allow information sent by the human
nervous system to control external equipment, is therefore extremely impor-
tant for the development of the next generation of prosthetic devices, such as
artificial organs, hands, and legs. On the other hand, with regard to the con-
trol method of artificial heart systems, a definitive and reliable method has
