Henk van Damme
Pamgene / Organon Teknika B.V., Akzo Nobel, Boseind 15, 5281 RM Boxtel, The Netherlands. (Tel: +31 411 654 560, Fax: +31 411 654 311, E-mail: h.damme@teknika.btl.akzonobel.nl)
A microarray is a test principle, which is dedicated to perform various tests in
parallel. It finds many applications in all kinds of tests related to genetic material.
Such an array for genetic material is called a DNA-chip and usually consist of a flat
solid surface with capture probes at specific positions (spots) directed towards the
various targets, which are possibly present in the sample. The rate limiting step of the
hybridization of the sample molecules (the target) with the capture probes (the spot) is
the diffusion towards a specific spot. Because the diffusion is very slow in this set-up
incubation of the sample with an array usually takes place overnight.
The microarray of Pamgene, developed at Organon Teknika eliminates the diffusion
limitation by using a special porous material as a solid support for the arrays. The
target molecules are forced through the (porous) array by flow, resulting in diffusion
distances in the flow through array in the order of 100 nm. Now the hybridization process
becomes fully reaction rate limited and results can be obtained within a few minutes.
Oligo microarrays were made by piezo-inkjet spotting of sub-nanoliter volumes of the oligo
solutions onto the porous support. Attachment of these capture oligos can be performed
either via an adsorptive or a covalent route.
The incubation with a sample containing a fluorescein labeled target molecule was
performed by pumping the sample several times through the porous support at the position
of the array. The dynamics of the hybridization reaction of the target molecules with all
spots on the array was measured simultaneously by using a CCD camera.
Also the effect of changing the temperature on the hybridization of the target to all
different probes (including point mutations) could be measured simultaneously. By changing
the temperature, a point mutation could be easily distinguished from a perfect match.