Nitric oxide (NO) electrochemical sensors - Electrochemical Sensors, Biosensors and Their Biomedical Applications - page 11

5000

3000

y 3.0287x 51.743

2500

R 2 0.9981

4000

2000

1500

1000

800 nM

3000

500

0

0 500 1000

Concentration/nM

2000

400 nM

200 nM

1000

100 nM

50 nM

0

1000

20 40 60 80 100 120 140 160 180

Time/s

FIGURE 1.4 Response of WPI's ISO-NOP NO sensor to increasing concentration of chemically generated
NO, inset shows the resulting calibration curve. (Reprinted with permission from Frontiers in Bioscience [26].)

is lower than the anticipated current change upon NO addition. The linear range of an
NO sensor is important to know before performing any measurement. For example, the
concentration of NO that is being measured must be in the linear range of the sensor in
order for the measurement to be accurate. Typical commercially available NO sensors
from WPI have a wide linear range of 1 nM-10

M. Sensor lifetime and reproducibility
are important to know when using a sensor and can be determined by frequent calibra-
tion, as described above. Biocompatibility is also extremely important when making
NO measurements in vivo . Frequently, NO sensors are impaled into living tissue so
the reactivity of the tissue toward the NO-selective membrane must be minimal and
cause a minimal amount of irritation in the tissue. The NO-selective membranes used
by this lab fulfi ll the requirements of being unreactive toward biomolecules and do
not contribute to tissue infl ammation. In most applications detection limit, sensitivity,
selectivity and response time are usually the most important requirements and will be
described in further detail.

µ

1.5.1 Sensitivity and detection limit
The sensitivity of an NO sensor depends largely on the reactive surface area of the
sensor and the electrode materials used in the design and can range from 0.03 pA/nM
to 100 pA/nM NO. Generally speaking, this sensitivity is directly proportional to the
electrode size and surface status where an electrode with a small surface area will gen-
erally have a lower sensitivity compared to one with a larger surface area. Although