Nitric oxide (NO) electrochemical sensors - Electrochemical Sensors, Biosensors and Their Biomedical Applications - page 16

(a) (b) (c)

E E

NA
0.5

Ach
10

NA
0.5

SNAP
10

NA
0.5

Ach
10

SNAP
10

µ M µ M µ M µ M µ M µ M µ M

W

W

10 mN

W

20 nM

5 min

FIGURE 1.7 Simultaneous measurements of force (upper traces) and NO concentration (lower traces) in
an endothelium intact (+E) segment of rat superior mesenteric artery contracted with 0.5

µ M noradrenaline

(NA) and relaxed with either 10 M SNAP (b). Panel C shows a similar

measurement in the rat superior mesenteric artery after mechanical endothelial cell removal. As can be seen in
C, ACh addition does not cause NO production from the artery but shows an NO increase upon SNAP addi-
tion causing artery relaxation. W

µ M acetylcholine (ACh) (a), or 10 µ

washout. (Reprinted with permission from Blackwell Publishing [120].)

group has also experimented with measuring NO concentration in the artery of a
hypertensive rat [122] and in isolated human small arteries [123]. Schuhmann's group
has recently published some very interesting results describing the measurement of NO
release from human umbilical vein endothelial cells (HUVEC) using a unique array of
microelectrodes [124]. Figure 1.8 (top) shows an SEM image of the microelectrode
array. Following microelectrode array construction the surfaces of the electrodes were
modifi ed with nickel tetrasulfonate phthalocyanine tetrasodium salt using electrochem-
ically induced deposition. Following this deposition the HUVEC cells were allowed to
grow in the interstitial spaces between the electrodes (Fig. 1.8, bottom) and NO release
from the cells was monitored as a function of growth and stimulation from bradykinin.
This work is unique because the cells are actually being grown on the Si 3 N 4 insulating
layer so the cells are not being affected by the microelectrode working potential, which
typically causes cell death, allowing for NO concentration to be monitored.
A recent publication by Millar has shown that NO concentrations can be meas-
ured in bovine eyes' trabecular meshwork in situ using an ISONOP200 electrode
from WPI [79]. For this study, the tip of the 200 µ m diameter electrode was inserted