Patent Application
20070017868
The present invention relates to analysis of fluidic samples.
Analyzing samples consisting of complex mixtures resulting e.g. from biological materials such as cells, organisms, or organic tissues became increasingly important during the last decade. Scientists performing research in the domain of biology, biochemistry, and in further related domains were focusing on the development of technologies permitting to precisely, rapidly, and efficiently analyze a sample qualitatively and quantitatively.
Said mixtures may be protein mixtures, polysaccharides, regulatory substances, carbohydrates, nucleic acids, amino acids, nucleotides, nucleosides, fats, fatty acids, and organic acids or metabolic mixtures. The last are usually composed of peptides, sugars, fatty acids, steroids, nucleotides, carbon acids, vitamins, hydrates, nucleic acids, amino acids, nucleotides, nucleosides, fats and a plurality of other additional low molecular compounds (having a molecular weight up to 2 kDa). The qualitative and quantitative analysis of metabolites is usually referred to as metabolomics. Similarly the qualitative and quantitative analysis of proteins is usually referred to as proteomics.
Accordingly samples being subjected to metabolomics may contain the ensemble of low molecular compounds being produced in an organism due to metabolism, or at least a subfraction of it, thus being of high complexity. So, a human metabolom sample e.g. requires the performance of multiple fractioning—or separating steps due to its composition of up to 10 000 compounds. Said complex mixture needs to be pre-fractionated into its classes prior to performance of further quantitative and/or qualitative analysis.
U.S. Pat. No. 6,849,396 B2 to Schneider, Luke V. discloses methods for conducting metabolomics. Purifying of metabolites and conducting metabolic analyses generally involves determining metabolic flux values for a plurality of target analytes by monitoring the relative isotope abundance of a stable isotope in a substrate labeled with the stable isotope and/or one or more target metabolites formed through metabolism of the labeled substrate. Furthermore, the methods are based on electrophoretic methods to separate the target analytes from other components within the sample being analyzed. Further methods involve administering a substrate labeled with a stable isotope to a subject.
US 20040147040 A1 to Bluggel, M. and Schurenberg, M. describes methods and instrumentation for two or multidimensional separations of biosubstance mixtures, especially protein mixtures, for mass spectrometric analysis.
US 20030168392 A1 to Masuda, J. et al. publishes a multi-dimensional liquid chromatography separation system, based on the difference of two or more kinds of separation modes, (e.g., chemical or physical properties of analytes) which may improve separations when samples contain complex mixtures. Here, the analytes separated on the 1 st analysis system (consisting of the 1 st column and the 1st mobile phase) will be trapped onto individual trapping columns. Then the trapped analytes will be loaded onto the 2nd analysis system consisting of the 2nd column and the 2nd mobile phase. The trapping and loading mechanism consists of a combination of switching valves necessary to produce the serial separations.
Once the pre-fractionation is done and thus the desired class of metabolites or proteins and peptides can be handled separately, the appropriate technology can be chosen to carry out the succeeding analytical steps such as mass spectrometry, UV, fluorescence or immuno-histochemical detection. For peptidomics, e.g. one may follow the methods described in US 20040180449 A1 to Hamstra A. J. et al. It refers to methods for separating or purifying samples, for example separating peptides or peptide groups from a protein sample.
It is an object of the invention to provide an improved fluidic sample analysis. The object is solved by the independent claims. Preferred embodiments are shown by the dependent claims.
According to embodiments of the present invention, an analysis system to analyze fluidic samples is provided. Said analysis system generally comprises two or more trapping columns being connected in series, thereby allowing to perform separation of hydrophobic and hydrophilic compounds.
In one embodiment the further separation and characterization is obtained due to combination of the trapping columns with analytical columns: Once separated by passing the trapping columns, the hydrophobic and hydrophilic compounds become fractionated directly by use of analytical columns that are connected to the trapping columns, whereby the subsequent identification of the fractionated compounds is facilitated. Accordingly, a poly-dimensional analytical device is provided which allows carrying out an analysis without or at least reduced delay, since the sample may be analyzed completely in one apparatus.
Further aspects refer to analyzing said biological fluidic samples comprising hydrophobic and hydrophilic compounds, taking into consideration that it is most desirable to analyze even smallest molecules such as small peptides. Additional advantages result when the system is miniaturized to chip size, accordingly permitting the separation and analysis of very small sample volumes, which means that the number of analyses per time can be increased.
Other objects and many of the attendant advantages of embodiments of the present invention will be readily appreciated and become better understood by reference to the following more detailed description of embodiments in connection with the accompanied drawings.
Embodiments of the present invention generally refer to a substantially complete analysis of biological fluidic samples such as peptides or metabolites, comprising hydrophobic and hydrophilic compounds, by performance of one single procedure in a single analysis system.
In
Frequently used and well known hydrophilic trapping columns are graphite columns, which are suitable for the use as pre-columns and as trapping columns. But the embodiments of the present invention are not intended to be limited on the use of graphite columns, since other materials than graphite might be suitable, too. The person skilled in the art might select a hydrophilic column comprising a material known from Hydrophilic Interaction Chromatography (HILIC). Substantially, the HILIC stationary phase is a polar material such as silica, diol, amino compound, cyan compound or the like, or a composition thereof. Even combinations of polymeric materials with one of more of the aforesaid compounds might be considered.
Furthermore, the commonly used C-18 column, which is a well known silica column with the appropriate pore size to trap small molecules to proteins, may be substituted by another column such as C-4-type, C-8-type, or any stationary phase with alkyl-chains up to C-30. Accordingly, the term “C-18 column” as used in the following is not intended to be limiting.
The trapping columns T1, T2 may thus provide a device for a first analytical dimension. Each of the trapping columns T1, T2 may then be connected to an analytical column A1, A2; said analytical columns A1, A2 may provide a second analytical dimension due to the further fractionations of the components according to an organic gradient.
In a preferred embodiment, a C-18 pre-column is selected as the first trapping column T1, and a graphite pre-column as second trapping column T2. Downstream to the C-18 pre-column T1, an analytical C-18 column A1 is located. Downstream to the second pre-column T2, which may be a graphite pre-column, an analytical graphite column A2 is arranged, wherein graphite is used exemplarily for any suitable hydrophilic solid phase.
In
Generally, the fluidic communication between two of the trapping columns T1, T2, T3, e.g. connected in series and/or between a trapping and an analytical column A1, A2, may be provided by use of a tube or a channel C. One or more of such channels C may be equipped with a valve or a fluid flow controller in order to determine a value relating to the flow of a fluid, eluent, or sample. If one single column of the type “third column” T3 or “first column” T1 is merging into more than one downstream column, the interconnecting tube or channel C could be provided with a valve e.g. coupled to one or more bypassing systems. The bypassing system could comprise another trapping and analyzing column T1′, A1′, as shown in
The above described embodiments may be advantageously miniaturized to micro size, e.g. for use in a microfluidic device which comprises the analysis system of the above embodiments. Such microfluidic device could be designed as single- or as a multilayer microfluidic device, permitting to perform an economic analytical procedure with a high resolution. Such microfluidic device may be embodied e.g. as described in U.S. Pat. No. 5,571,410, US RE36350, U.S. Pat. No. 5,658,413, U.S. Pat. No. 5,882,571, U.S. Pat. No. 5,804,022, U.S. Pat. No. 6,093,362, or U.S. Pat. No. 5,645,702.
If desired, one may connect a plurality of first and second tapping columns T1, T2, wherein preferably the sample first passes the hydrophobic metabolites trapping columns and then the hydrophilic metabolites trapping columns.
After trapping the hydrophobic and hydrophilic metabolites onto the columns T1, T2, an elution might be performed. As known to those skilled in the art, elution is usually provided by rinsing the selected column with a fluid or eluent, respectively.
In a first elution process E2, elution of the components trapped on the second column T2, which is the hydrophilic pre-column T2, may be provided. Said components are directed onto an analytical graphite column A2, or onto any other suitable hydrophilic analytical column, become fractionated according to an organic gradient. Then, identification I and quantification of the separated components can be done, e.g. using mass spectroscopy (MS) and/or MS/MS— spectroscopy.
In a second elution process E1, elution of the components trapped on the first column—the C-18 pre-column—T1 may be provided. Components are flushed by using an eluent onto an analytical column A1 (e.g. a C-18 column) and become separated according to an organic gradient. As in E2, identification and quantification of the separated components may be done e.g. by mass spectrometry (MS) and/or MS/MS— spectroscopy. Such MS-systems may be TOF (time of flight spectroscopy), Q-TOF (Quadrupole-Time-Of-Flight spectroscopy) or FT-MS (Fourier transformed mass spectroscopy), or ion-trap mass spectrometry.
The analytical performance is known to those skilled in the art.
The afore-described embodiments may allow performing a time-saving analysis of highly complex samples, combining fractionation or separation, respectively, and identification efficiently.
First, a complex fluidic sample FS2 is acidified by adding of acids such as acetic acid or formic acid or another suitable weak acid, charging peptide—and amine—compounds positively. Then, the fluidic sample FS2 is injected into the analytical system, being directed immediately onto a third column T3, which is an SCX column (strong cation exchange column) herein.
Positively charged compounds are retained in said third column T3, whereas neutral or negatively charged compounds of the fluidic sample FS2 pass said column and flow through the C-18 pre-column T1. The C-18 pre-column T1 retains hydrophobic metabolites and the uncharged peptides.
The second column T2—which is the last one in the series and which is a graphite or other hydrophilic pre-column—, retains the hydrophilic metabolite compounds and the hydrophilic and small, non-charged peptide compounds.
In the following, the compounds retained in said hydrophilic pre-column T2 are eluted when the elution E1 is performed and flushed from said pre-column T2 onto the analytical graphite column A2. Herein, further fractionation is performed according to an organic gradient. Then, the identification I is done e.g. by use of mass spectroscopy and/or MS/MS analyses as described above.
Afterwards, the compounds which have been retained on the C-18 pre-column T1 become eluted in the second elution process E2 and are directed onto the analytical C-18 column A1, become fractionated according to an organic gradient, and subjected to the identification I, too.
After the first and the second trapping—and analytical columns T1, T2, A1, A2 are unloaded, the components retained on the SCX column become eluted, too, by performing a third elution process. This may be done according to a salt step gradient elution. Therefore, the components can be flushed with saline solution from the third column T3; the gradient is obtained by increasing the salt concentration step-wise (e.g. 20 mM, 40 mM, 60 mM, 80 mM, 100 mM, 250 mM, 500 mM ammonium acetate).
Another option is to flush by use of the back flush method on the analytical C-18 column T2 in order to perform fractionation according to an organic gradient. Subsequently the identification I is performed.
Embodiments may be performed by use of conventional trapping columns, e.g. having lab-size, or a microfluidic arrangement. One can design micro sized C-18 columns as well as micro sized graphite columns. A chip may be designed on which chip the micro pre-columns (SCX or affinity column, C-18 column and graphite-column or other hydrophilic column) T1, T1′, T2, T3 and the analytical columns (analytical C-18 column and analytical graphite-column or other hydrophilic column) A1, A1′, A2 are arranged.
In one embodiment components of samples of this complex composition, comprised of proteomic and metabolomic compounds, can be retained by direct combination of strong cationic exchange column, C-18 pre column, and graphite pre-column, providing a complete retaining of that components, performing elution until the corresponding analytical column, and performing analyses afterwards.
| Number | Date | Country | Kind |
|---|---|---|---|
| PCT/EP05/53608 | Jul 2005 | WO | international |
This application claims priority from PCT Application PCT/EP2005/053608, filed under the Patent Cooperation Treaty on 25 Jul. 2005, in the European Patent Office in Munich, Germany, hereby incorporated by reference.
