Biomedical Engineering Reference
In-Depth Information
membrane materials. Another advantage of glass slides is that they can be coated and
thus allow for efficient protein binding. Although used for some commercial prod-
ucts [
11
] now for many years, the slide format has several disadvantages in
molecular diagnostics approaches based on protein arrays. Two main reasons have
driven many researchers to look for alternatives to glass slides. Reason number one
is, that planar and coated high quality glass slides are still considered expensive with
prices of 10 Euro per slide being more the rule than the exception. Reason number
two is the format of slides itself and its difficult handling when it comes to auto-
mation: Slides can be easily handled manually, but automating all required handling
steps in an array experiment for 10,000 s of slides per day is still challenging and
according to the authors knowledge there is no solution available at the time of
editing.
There are several alternatives to glass slides as carriers for protein arraying that
have been published in the past couple of years. This includes a number of dif-
ferent biosensors [
12
,
13
], mostly developed for label free detection schemes.
Although these items can be mass produced, still their size is something that is
typically unknown in diagnostic laboratories and often the interface to the real
laboratory environment needs more and better ergonomic design.
GeneOhm was one of the first companies to combine (DNA) biosensing devices
with standard diagnostic formats in the form of microplates (
http://www.slas.org/
education/standards/ANSI_SBS_1-2004.pdf
). Other formats of arrays produced on
a specific surface and brought into tubes or plates commonly used in diagnostic
laboratories were developed by Affymetrix [
14
] and German Clondiag that later
became a part of Alere [
15
].
Protein arrays in microplate structures are available as products for autoimmune
diagnostics for some years now. Toronto based SQI Diagnostics was the pioneer
for these developments [
16
]. To array the capture antigens a planar glass slide with
a microplate footprint is used, to which a ''motherstructure'', providing 96
microplate chimneys, gets connected with a specific gasket. After connection, 96
individual reaction wells are available for sample incubation in a standard
microplate footprint. Albeit this format is very amenable to automation and pro-
vides very good optical quality for fluorescent detection, still the costs of goods for
precisely manufactured glass surfaces in microplate format, required gaskets and
related polymer structures are still significant and for a diagnostic product are
unproportionally high.
3 Direct Printing into Microplate Wells
Multiwell or microtiter plates cover a broad spectrum of biological, chemical and
pharmacological laboratory uses. For high throughput screening as well as diag-
nostic methods such plates are mostly produced in one piece by injection
moulding. Especially as a result of high throughput applications auxiliary auto-
matic and robotic instrumentation has been developed and the dimensions of the
