Environmental Sample Processor (ESP)
Printing probe arrays
The “ink” of the probe array is made up of a single-stranded DNA probe, complementary to a unique rRNA sequence in the organisms of interest. These probes are chemically linked to biotin and mixed with the protein streptavidin, which binds the whole to the surface of the filter support. Electrostatic charges force the probes to stand upright, ready to attach to any complimentary sequence of nucleic acid. The support is a 25-millimeter circle of filter material that fits in the puck, where the analysis takes place.
To print probe arrays, an XYZ translation gantry positions four piezoelectric-actuated nozzles over the spotting area and delivers 6nL of probe solution per spot. Each of those probes targets a specific species or group of species. The probes can be printed on the substrate in any shape or pattern, as long as you keep track of the “map”. Below are two typical maps generated with various printers we have used over the years. Note a target might have 5-8 dedicated spots to provide a pseudo-replicated response of the sample to this array print.