Biology Reference
In-Depth Information
Table 7.1 Definitions of important factors to be considered when evaluating
biosensor performance
Characterization term
Definition
Limit of detection
Lowest quantity of pathogen that can be detected
by a given method or technique.
Sensitivity
Most commonly, this is defined as the ability to
detect very few organisms in a sample (rather
than the degree of discrimination between
various concentration levels). This is influenced
by both the affinity of the recognition element
for the target analyte as well as the
transduction process.
Specificity/Selectivity
The ability of the sensors to discern one closely
related species or strains from another or even
viable organisms from dead ones.
Detection range
The concentration range which the sensor
operates. The lower limit is determined by the
sensitivity. The upper limit. Ideally, the sensor
response will be linear between the limits,
allowing easy quantification.
Reproducibility
Processing/Sample volume
Total volume necessary for one analysis.
Processing/Assay time
Total time necessary to prepare the sample,
analyze it and read out the results.
Background/Sample matrix
Type of water and water content or other
solution in which detection takes place.
cheap, robust, fully automated, capable of long-term operation with mini-
mal maintenance, and able to deliver fast results. In this case, high sensitivity
and specificity will be less important and most likely sacrificed to achieve
the above characteristics. Highly sensitive and specific measurements could
be performed back at an analytical lab using larger, more expensive equip-
ment, which may require operation by skilled technicians. The typical size
of the biosensor surface is on the order of mm 2 . The sample volume should
be as low as possible given the size of the biosensor while still providing a
meaningful measurement of the number of pathogens present.
Because biosensor systems are inherently complex, it is challenging to
fully understand the interplay of convection, diffusion, and reaction involved
in the capture of the target analyte on the surface. The reader is referred to
an excellent article by Todd Squires in which the physics of analyte trans-
port and reaction dynamics is discussed in relation to sensor size and sample
delivery, which is very helpful in the design and optimization of biosensors. 7
Search WWH ::




Custom Search