Biology Reference
In-Depth Information
after the death of a cell. The lack of RNA detection, however, may still
occur in viable but not culturable cells and initiate incorrect risk assessment
decisions.
On the positive side, most waterborne pathogens can be removed from
drinking water with standard drinking water treatment measures. Most
if not all outbreaks are tracked back to untreated or inadequately treated
waters.
The future of pathogen detection follows the culture-independent,
library-independent trend for microbial target detection. An ideal method
would allow for a real-time flow-through system to monitor water sys-
tems on a continuous basis that could be miniaturized and automated to
allow for ease of use and economy of costs. Recently, it has been shown
that the technical problems with PCR can be overcome by the develop-
ment and use of isothermal techniques for the nucleic acid amplification,
such as LAMP. This technology, when coupled to a photomultiplier tube
for fluorescent detection and a microfluidic control module, was able to
simultaneously detect four different pathogens from FISH within 65 min
with a detection limit of 20 copies.
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Cell-based sensors are also an emerging frontier in the area of nanodiag-
nostics.
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The use of cells as sensors is a very attractive way to devise sensi-
tive biochemical detectors. The main advantages of whole cells as biosensors
are that cells have built-in natural selectivity to biologically active chemicals
and they can react to analytes in a physiologically relevant way. The trans-
ductions of the cell sensor signals may be achieved by the measurement
of transmembrane and cellular potentials, impedance changes, metabolic
activity, analyte inducible emission of genetically engineered reporter sig-
nals, and optically by means of fluorescence or luminescence.
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Significant
challenges exist for long-term operation because the cells need to be kept
alive and healthy under various harsh operating conditions. Much work
has been done toward this front, as this technology has been extended to
demonstrate automated portable cell-based biosensors platform that have
been field tested.
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Furthermore, direct measurement of current through
ion channels in the cells has also been used to develop on-chip patch clamp
devices, which can potentially be very sensitive to changes in the ambient
conditions of the cells. Lastly, many of the new innovative approaches are
using the unique properties of nanomaterials in order to achieve detection
of infectious agents. So far, however, most of the research has concentrated
on diagnosis of infectious diseases and not on detection of pathogens from
water sources.
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