Microfluidic system (MS)

Details Microfluidic system (MS) Microfluidic system (MS)

2001-03-19

2003-11-25

Wells, Nikita (Department: 2881)

Radiant energy

Ionic separation or analysis

With sample supply means

C250S281000, C250S282000, C422S070000, C422S068100, C422S105000

Reexamination Certificate

active

06653625

ABSTRACT:

TECHNICAL FIELD
The present invention relates to a microfluidic device, which can be interfaced to a mass spectrometer (MS). The device comprises a microchannel structure having a first port (inlet port) and a second port (outlet port). A sample to be analysed is applied to the first port and presented to the mass spectrometer in the second port. This second port will be called an MS-port. There may be additional inlet and outlet ports. During passage through the microchannel structure the sample is prepared to make it suitable for analysis by mass spectrometry.
The sample presented in an MS-port will be called an MS-sample. An analyte in an MS-sample is an MS-analyte. “Sample” and “analyte” without prefix will primarily refer to a sample applied to an inlet port.
One important aspect of the present invention concerns mass spectrometry in which the MS-samples are subjected to Energy Desorption/Ionisation from a surface by input of energy. Generically this kind of process will be called EDI and the surface an EDI surface in the context of the invention. Typicallly EDIs are thermal desorption/ionisation (TDI), plasma desorption/ionisation (PDI) and various kinds of irradiation desorption/ionisation (IDI) such as by fast atom bombardment (FAB), electron impact etc. In the case a laser is used the principle is called laser desorption/ionisation (LDI). Desorption may be assisted by presenting the MS analyte together with various helper substances or functional groups on the surface. Common names are matrix assisted laser desorption/ionisation (MALDI) including surface-enhanced laser desorption/ionisation (SELDI). For MALDI see the publications discussed under Background Publications below. For SELDI see WO 0067293 (Ciphergen Biosystems).
The surface from which desorption/ionisation is intended to take place is called an EDI surface
By microformat is meant that in least a part of the microchannel structures the depth and/or width is in the microformat range, i.e. <10
3
&mgr;m, preferably <10
2
&mgr;m. In the most typical microformat structures either the width and/or the depth are in principle within these ranges essentially everywhere between the sample inlet port and the MS-port.
BACKGROUND PUBLICATIONS
For some time there has been a demand for microfluidic sample handling and preparation devices with integrated MS-ports. This kind of devices would facilitate automation and parallel experiments, reduce loss of analyte, increase reproducility and speed etc.
WO 9704297 (Karger et al) describes a microfluidic device that has an outlet port that is claimed useful when conducting electrospray ionisation mass spectrometry (ESI MS), atmospheric pressure chemical ionisation mass spectrometry (APCI MS), matrix assisted laser desorption/ionisation mass spectrometry (MALDI MS) and a number of other analytical principles.
U.S. Pat. No. 6,110,343 (Ramsey et al) describes an electrospray interface between a microfluidic device and a mass spectrometer.
U.S. Pat. No. 5,969,353 (Hsieh) describes an improved interface for electrospray ionization mass spectrometry. The interface is in the form of an electrospray tip connected to a microchannel structure of a chip.
U.S. Pat. No. 5,197,185 (Yeung et al) describes a laser-induced vaporisation and ionization interface for directly coupling a microscale liquid based separation process to a mass spectrometer. A light-adsorbing component may be included in the eluting liquid in order to facilitate vaporisation.
U.S. Pat. No. 5,705,813 (Apffel et al) and U.S. Pat. No. 5,716,825 (Hancock et al) describe a microfluidic chip containing an interface between a microfluidic device and an MALDI-TOF MS apparatus. The microfluidic device comprises
(a) an open ionisation surface that may be used as the probe surface in the vaccum gate of an MALDI-TOF MS apparatus (column 6, lines 53-58 of U.S. Pat. No. 5,705,813) or
(b) a pure capture/reaction surface from which the MS-analyte can be transferred to a proper probe surface for MALDI-TOF MS (column 12, lines 13-34, of U.S. Pat. No. 5,716,825).
These publications suggest that means, such as electrical connections, pumps etc, for transporting the liquid within a microchannel structure of the device are integrated with or connected to the device. This kind of transporting means imposes an extra complexity on the design and use, which in turn may negatively influence the production costs, easiness of handling etc of these devices.
U.S. Pat. No. 5,705,813 (Apffel et al) and U.S. Pat. No. 5,716,825 (Hancock et al) are scarce about
the proper fluidics around the MALDI ionisation surface,
the proper crystallisation on the MALDI ionisation surface,
the proper geometry of the port in relation to crystallisation, evaporation, the incident laser beam etc,
the proper arrangement of conductive connections to the MALDI ionisation surface for MALDI MS analysis.
WO 04297 (Karger et al) and WO 0247913 (Gyros AB) suggest to have microchannel structures in radial or spoke arrangement.
A number of publications referring to the use of centrifugal force for moving liquids within microfluidic systems have appeared during the last years. See for instance WO 9721090 (Gamera Bioscience), WO 9807019 (Gamera Bioscience) WO 9853311 (Gamera Bioscience), WO 9955827 (Gyros AB), WO 9958245 (Gyros AB), WO 0025921 (Gyros AB), WO 0040750 (Gyros AB), WO 0056808 (Gyros AB), WO 0062042 (Gyros AB) and WO 0102737 (Gyros AB) as well as WO 0147637 (Gyros AB), WO 0154810 (Gyros AB), WO 0147638 (Gyros AB), and WO 0146465.
See also Zhang et al, “Microfabricated devices for capillary electrophoresis—electrospray mass spectrometry”, Anal. Chem. 71 (1999) 3258-3264) and references cited therein.
Kido et al., (“Disc-based immunoassay microarrays”, Anal. Chim. Acta 411 (2000) 1-11) has described microspot immunoassays on a compact disc (CD). The authors suggest that a CD could be used as a continuous sample collector for microbore HPLC and subsequent detection for instance by MALDI MS. In a preliminary experiment a piece of a CD manufactured in polycarbonate was covered with gold and spotted with a mixture of peptides and MALDI matrix.
OBJECTS OF THE INVENTION
A first object is to provide improved means and methods for transporting samples, analytes including fragments and derivatives, reagents etc in microfluidic devices that are capable of being interfaced with a mass spectrometer.
A second object is to provide improved microfluidic methods and means for sample handling before presentation of a sample analyte as an MS-analyte. Sub-objects are to provide an efficient concentration, purification and/or transformation of a sample within the microfluidic device while maintaining a reproducible yield/recovery, and/or minimal loss of precious material.
A third object is to provide improved microfluidic methods and means that will enable efficient and improved presentation of the MS-sample/MS-analyte. This object in particular applies to MS-samples that are presented on a surface, i.e. an EDI surface.
A fourth object is to enable reproducible mass values from an MS-sample that is presented on a surface, i.e. on an EDI surface.
A fifth object is to provide improved microfluidic means and methods for parallel sample treatment before presentation of the analyte to mass spectrometry. The improvements of this object refer to features such as accuracy in concentrating, in chemical transformation, in required time for individual steps and for the total treatment protocol etc. By parallel sample treatment is meant that two or more sample treatments are run in parallel, for instance more than five, such as more than 10, 50, 80, 100, 200, 300 or 400 runs. Particular important numbers of parallel samples are below or equal to the standard number of wells in microtiter plates, e.g. 96 or less, 384 or less, 1536 or less, etc
A sixth object is to provide a cheap and disposable microfluidic device unit enabling parallel sample treatments and having one or more MS-ports that are adapted to a mass spectrometer.
SUMMARY OF THE INVENTION
The present inventors have recognized that sever

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