Biomedical Engineering Reference
In-Depth Information
Fig. 10
Dual colour colorimetric detection
4.1 Detection Devices for Colorimetric Array Readout
For the detection of colorimetric assays typically quite inexpensive detectors might
be used, especially when compared to fluorescent detectors. Whereas in fluores-
cent detectors specific excitation light sources are required, colorimetric detection
of a well requires just an even lighting from a white lamp, e.g. a halogen lamp,
being much less expensive when compared to laser based excitation systems.
Dependent on whether transparent or non transparent surfaces are used translucent
or reflective lighting is required. For detection conventional CCD cameras can be
used. If for some reason long exposure times are required to detect meaningful
signals, these CCD cameras should be cooled. If a single colour has to be detected,
monochrome CCDs are sufficient, whereas in the multi-colour detection scheme
shown above a colour CCD detection is required. Most array analysis programs
require at least 10 9 10 pixels for an accurate spot analysis. Consequently a
protein array with spot sizes of 300 micron needs a resolution of at least
30 micron, whereas larger spots tolerate even less resolution while smaller spots,
e.g. a 100 micron spot, require at least 10 micron resolution. Although office flat
bed scanners might be suitable for the colorimetric detection of arrays on slides or
membranes, their usability for detection of arrays in microplates is somewhat
limited due to the uneven lighting resulting from the chimneys of the microplates.
5 Sophisticated Software Tools are Needed for Array
Production and Analysis
Protein microarrays offer enormous potential for a wide range of applications but a
major bottle neck remains the automated analysis of the biochips. The analysis
of protein microarrays is still in their infancy in comparison to nucleotide
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