A 96-Channel Microdevice for High Throughput
Electrospray Ionization Mass Spectrometry (ESI/MS)
Liu H.,
, Foret, F., Felten, C., Zhang, B., Jedrzejewski,
P., Karger, B.
The Barnett Institute
Northeastern University
Boston, MA 02115
(e-mail: hanghui@iname.com)
Abstract
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A microdevice developed for high throughput ESI/MS.
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Fabricated by casting from a solvent resistant epoxy resin.
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The sample wells arranged in the standard 96 well plate format
with each well connected by a microchannel to an independent ESI tip.
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A computer controlled linear translation stage for positioning
of individual electrospray tips in front of the sample orifice of the mass
spectrometer.
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Without injection or washing steps involved, a throughput
of 720 samples/hr has been achieved.
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Application in HIV-1 enzyme assay.
Goals
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96 well plate format
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Independent flow conduit and ESI tip for each sample (no
time waste on washing conduit)
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Fast switching from one sample to the next without cross
contamination or carryover.
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10 x higher throughput than conventional FIA techniques
Design
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Each sample well on the plate is connected to its independent
ESI tip through a micro channel.
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Both the pressurized gas and the high voltage are connected
only to one specified sample well and its channel at a time.
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Sample wells are arranged in 96 well format and ESI tips
in an linear array.
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As the computer controlled stage moves, samples are mobilized
and electrosprayed sequentially.
Fabrication
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From master plates, a rubber mold was made.
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From the rubber mold, a polymeric plate with well openings
on one side and recessed channels on the other side was made by casting.
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The above plate was bonded with a flat plate with embedded
electrodes to form closed channels.
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Fused silica capillaries were glued into the channels
to form ESI tips.
HIV-1 Protease Inhibition Assay
Substrate:
Ser-Ile-Asn-Tyr -/- Pro-Ile-Val (MW:819)
Products:
Ser-Ile-Asn-Tyr, Pro-Ile-Val (MW: 327)
Internal Standard: Glu-Ile-Val (MW: 359)
Assay Buffer:
100 mM MES, 300 mM KCl, 5 mM EDTA, 4.5% DMSO (pH=5.5 adjusted with NaOH)
Incubation:
10-90 min at 37 oC
Quench:
10% TFA
Conclusions
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Results comparable with those obtained by conventional
ESI.
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High throughput (720 samples / hr) and lack of cross contamination
due to fast gas/HV switching between independent channels.
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Compatibility with 96 well plate technologies.
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Potentially inexpensive and thus disposable.
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Application potential for drug screening and quality control.
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Small sample requirement: all the sample deposited in
a sample well can be used to generate signal.
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