U.S. patent application number 14/481483 was filed with the patent office on 2015-01-15 for mass spectrometry analysis of microorganisms in samples.
The applicant listed for this patent is PURDUE RESEARCH FOUNDATION. Invention is credited to Robert Graham Cooks, Ahmed Mohamed Hamid, Alan Keith Jarmusch, Zheng Ouyang.
Application Number | 20150017712 14/481483 |
Document ID | / |
Family ID | 49715563 |
Filed Date | 2015-01-15 |
United States Patent
Application |
20150017712 |
Kind Code |
A1 |
Cooks; Robert Graham ; et
al. |
January 15, 2015 |
MASS SPECTROMETRY ANALYSIS OF MICROORGANISMS IN SAMPLES
Abstract
The invention generally relates to systems and methods for mass
spectrometry analysis of microorganisms in samples.
Inventors: |
Cooks; Robert Graham; (West
Lafayette, IN) ; Hamid; Ahmed Mohamed; (Cairo,
EG) ; Jarmusch; Alan Keith; (Lafayette, IN) ;
Ouyang; Zheng; (West Lafayette, IN) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
PURDUE RESEARCH FOUNDATION |
WEST LAFAYETTE |
IN |
US |
|
|
Family ID: |
49715563 |
Appl. No.: |
14/481483 |
Filed: |
September 9, 2014 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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14151220 |
Jan 9, 2014 |
8859986 |
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14481483 |
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13926645 |
Jun 25, 2013 |
8704167 |
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14151220 |
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13265110 |
Jan 31, 2012 |
8859956 |
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PCT/US10/32881 |
Apr 29, 2010 |
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13926645 |
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61308332 |
Feb 26, 2010 |
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61246707 |
Sep 29, 2009 |
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61174215 |
Apr 30, 2009 |
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Current U.S.
Class: |
435/287.1 |
Current CPC
Class: |
H01J 49/26 20130101;
H01J 49/0422 20130101; H01J 49/0036 20130101; H01J 49/16 20130101;
C12Q 1/04 20130101; H01J 49/0409 20130101; H01J 49/10 20130101;
G01N 2560/00 20130101; H01J 49/04 20130101 |
Class at
Publication: |
435/287.1 |
International
Class: |
C12Q 1/04 20060101
C12Q001/04; H01J 49/04 20060101 H01J049/04; H01J 49/26 20060101
H01J049/26 |
Claims
1-47. (canceled)
48. A microorganism identification system, the system comprising: a
capture module, the module configured to capture an unknown
microorganism from a sample and generate ions of the unknown
microorganism, wherein the capture module comprises a porous
substrate operably coupled to a high voltage source; a mass
analyzer operably coupled to the capture module to receive the
generated ions of the unknown microorganism; and a central
processing unit (CPU) and storage coupled to the CPU for storing
instructions that when executed by the CPU cause the CPU to: accept
as input from the mass analyzer, at least one mass spectrum of the
unknown microorganism; compare the at least one mass spectrum of
the unknown microorganism to a database comprising mass spectra of
known organisms; and output an identification of the unknown
organism based on results of the comparison.
49. The system according to claim 48, wherein the sample is a
liquid sample.
50. The system according to claim 48, wherein the sample is a gas
sample.
51. The system according to claim 48, wherein the sample is a solid
sample.
52. The system according to claim 48, wherein the porous substrate
is discrete from a flow of solvent.
53. The system according to claim 48, wherein the porous substrate
tapers to at least one distal tip.
54. The system according to claim 48, further comprising a solvent
applied to the porous substrate.
55. The system according to claim 54, wherein the solvent comprises
an internal standard.
56. The system according to claim 48, wherein the microorganism is
a non-natural microorganism.
57. The system according to claim 48, wherein the mass analyzer is
for a mass spectrometer or a handheld mass spectrometer.
58. The system according to claim 57, wherein the mass analyzer is
selected from the group consisting of: a quadrupole ion trap, a
rectalinear ion trap, a cylindrical ion trap, a ion cyclotron
resonance trap, an orbitrap, a time of flight, a Fourier Transform
ion cyclotron resonance, and sectors.
59. The system according to claim 48, wherein the database
comprises a similarity cluster.
60. The system of claim 48, wherein the database comprises a mass
spectrum from at least one member of a clade of organisms.
61. The system of claim 48, wherein the database comprises a mass
spectrum from at least one subspecies of organisms.
62. The system of claim 48, wherein the database comprises a mass
spectrum from a genus, a species, a strain, a sub-strain, or an
isolate of organisms.
63. The system of claim 48, wherein the database comprises a mass
spectrum comprising motifs common to a genus, a species, a strain,
a sub-strain, or an isolate of organisms.
64. The system according to claim 48, wherein the mass spectra in
the database are annotated to show if they were acquired in
positive or negative mode.
65. The system according to claim 48, wherein the microorganism is
a bacterium.
66. The system according to claim 48, wherein the microorganism is
a virus.
67. The system according to claim 48, wherein the microorganism is
a fungus.
Description
RELATED APPLICATIONS
[0001] The present application is a continuation of U.S.
nonprovisional application Ser. No. 14/151,220, filed Jan. 9, 2014,
which is a continuation of U.S. nonprovisional application Ser. No.
13/926,645, filed Jun. 25, 2013, which is a continuation-in-part of
U.S. nonprovisional application Ser. No. 13/265,110, filed Jan. 31,
2012, which application is a national phase application and claims
the benefit of and priority to PCT/US2010/032881, filed Apr. 29,
2010, which claims priority to and the benefit of U.S. provisional
patent application Ser. No. 61/174,215, filed Apr. 30, 2009, U.S.
provisional patent application Ser. No. 61/246,707 filed Sep. 29,
2009, and U.S. provisional patent application Ser. No. 61/308,332,
filed Feb. 26, 2010, the content of each of which is incorporated
by reference herein in its entirety.
TECHNICAL FIELD
[0002] The invention generally relates to systems and methods for
mass spectrometry analysis of microorganisms in samples.
BACKGROUND
[0003] Mass spectrometry is a very sensitive analytical method used
for important research and for applications of analytical
chemistry, particularly life science. Electrospray ionization (ESI)
is generally regarded as the best-characterized and most efficient
method for ionization of molecules in solution phase. The process
can be conveniently divided into three stages: droplet formation,
droplet evaporation and ion formation (Gaskell, S. J. Journal of
Mass Spectrometry 1997, 32, 677-688). When a strong electric field
is applied to a solution flowing through a mass spectrometer probe,
a Taylor cone is formed at the tip of the probe, resulting in a
mist of small droplets being emitted from the tip of this cone. Due
to the evaporation of the free droplets and Coulombic forces, ions
of sample analyte are produced. The ions enter a mass spectrometer
and are subsequently analyzed.
[0004] A problem with ESI is that sample preparation is still a
necessary step before ESI can be used for analysis of many types of
samples. Prior to analyzing a sample by ESI mass spectrometry, the
sample will undergo extraction and filtration protocols to purify
the sample, for example to remove salts and detergents. Such
protocols are complex, time-consuming, and expensive. Further,
reagents used during the purification process can interfere with
subsequent analysis of a target analyte in the purified sample.
Additionally, samples that are not in solution must be dissolved as
well as purified prior to ESI analysis.
[0005] More recently, the concept of ambient ionization has been
developed, and now this family of ambient ionization has more than
twenty members, such as desorption electrospray ionization (DESI)
and direct analysis in real time (DART). Ambient ionization by mass
spectrometry allows the ionization of analytes under an ambient
environment from condensed-phase samples without much or even any
sample preparation and/or pre-separation, offering a solution for
real time and in situ analysis for complex mixtures and biological
samples. These ambient ionization methods are leading are extending
the mass spectrometry revolution in life science, environment
monitoring, forensic applications and therapeutic analysis.
However, the above described ambient ionization techniques still
require pneumatic assistance, a continuous flow of solvent, and a
high voltage power supply for the analysis of samples.
[0006] There is an unmet need for systems and methods that can
combine sample preparation and pre-treatment and the ionization
process for mass analysis of samples that do not require pneumatic
assistance or a continuous flow of solvent for the analysis of the
samples.
SUMMARY
[0007] The invention generally relates to new systems and methods
of generating ions from fluids and solid samples for mass
spectrometric analysis. Porous materials, such as filter paper or
similar materials are used to hold and transfer liquids, and ions
are generated directly from the edges of the materials when a high
electric voltage is applied to the materials. The porous material
is kept discrete (i.e., separate or disconnected from) from a flow
of solvent. Instead, a sample is either spotted onto the porous
material or the porous material is wetted and used to swab a
surface containing the sample. The porous material with spotted or
swabbed sample is then wetted and connected to a high voltage
source to produce ions of the sample which are subsequently
analyzed. The sample is transported through the porous material
without the need of a separate solvent flow.
[0008] Devices and methods of the invention combine sample
preparation and pre-treatment with the ionization process needed
for mass analysis of samples. Device and methods of the invention
allow for rapid and direct analysis of chemicals in raw biological
samples of complex matrices, such as biofluids and tissues, without
sample preparation. In particular embodiments, devices and methods
of the invention allow for the analysis of a dried spots of blood
or urine.
[0009] An aspect of the invention provides a mass spectrometry
probe including a porous material connected to a high voltage
source, in which the porous material is discrete from a flow of
solvent. Exemplary porous materials include paper, e.g., filter
paper, or PVDF membrane. The porous material can be of any shape.
In certain embodiments, the porous material is provided as a
triangular piece.
[0010] In certain embodiments, the probe further includes a
discrete amount of a solvent, e.g., a droplet or droplets, applied
to the porous material. The solvent is applied as a droplet or
droplets, and in an amount sufficient to wet the porous material.
Once applied to the porous material, the solvent can assist
transport of the sample through the porous material. The solvent
can contain an internal standard. The solvent/substrate combination
can allow for differential retention of sample components with
different chemical properties. In certain embodiments, the solvent
minimizes salt and matrix effects. In other embodiments, the
solvent includes chemical reagents that allow for on-line chemical
derivatization of selected analytes.
[0011] Another aspect of the invention provides a system for
analyzing a sample material including, a probe including a porous
material connected to a high voltage source, in which the porous
material is kept separate from a flow of solvent, and a mass
analyzer. The mass analyzer can be that of a benchtop mass
spectrometer or a handheld mass spectrometer. Exemplary mass
analyzers include a quadrupole ion trap, a rectilinear ion trap, a
cylindrical ion trap, a ion cyclotron resonance trap, and an
orbitrap.
[0012] Another aspect of the invention includes a method for
analyzing a sample including, contacting a sample to a porous
material, in which the porous material is kept separate from a flow
of solvent, applying a high voltage to the porous material to
generate ions of an analyte in the sample that are expelled from
the porous material, and analyzing the expelled ions. The method
can further include applying a discrete amount, e.g., a droplet or
droplets, of a solvent to the porous material. In certain
embodiments, analyzing involves providing a mass analyzer to
generate a mass spectrum of analytes in the sample.
[0013] In certain embodiments, the sample is a liquid. In other
embodiments, the sample is a solid. In embodiments in which the
sample is a solid, the porous material can be used to swab the
sample from a surface. A solvent can be applied to the porous
material prior to or after the solid has been swabbed. Exemplary
samples include chemical species or biological species.
[0014] Another aspect of the invention provides a method of
ionizing a sample including applying a high voltage to a porous
material to generate ions of an analyte in the sample, in which the
porous material remains separate from a solvent flow. Exemplary
porous materials include paper or PVDF membrane.
BRIEF DESCRIPTION OF THE FIGURES
[0015] FIG. 1A is a drawing of a sample solution being fed to a
piece of paper for electrospray ionization. FIG. 1B is a drawing of
a sample solution pre-spotted onto the paper and a droplet of
solvent being subsequently supplied to the paper for electrospray
ionization.
[0016] FIG. 2A is a MS spectrum of heroin (concentration: 1 ppm,
volume: 10 .mu.l, solvent: MeOH/H.sub.2O/HOAc (50:49:1, v/v/v))
using probes of the invention. FIG. 2B is a MS/MS spectrum of
heroin (concentration: 1 ppb, volume: 10 .mu.l, solvent:
MeOH/H.sub.2O/HOAc (50:49:1, v/v/v)).
[0017] FIG. 3A is a MS spectrum of caffeine (concentration: 10 ppm,
volume: 10 .mu.l, solvent: MeOH/H.sub.2O/HOAc (50:49:1, v/v/v))
using probes of the invention. FIG. 3B is a MS/MS spectrum of
caffeine (concentration: 10 ppb, volume: 10 .mu.l, solvent:
MeOH/H.sub.2O/HOAc (50:49:1, v/v/v)).
[0018] FIG. 4A is a MS spectrum of benzoylecgonine (concentration:
10 ppm, volume: 10 .mu.A solvent: MeOH/H.sub.2O/HOAc (50:49:1,
v/v/v)) using probes of the invention. FIG. 4B is a MS/MS spectrum
of benzoylecgonine (concentration: 10 ppb, volume: 10 .mu.l,
solvent: MeOH/H.sub.2O/HOAc (50:49:1, v/v/v)).
[0019] FIG. 5A is a MS spectrum of serine (concentration: 1 ppm,
volume: 10 .mu.l, solvent: MeOH/H.sub.2O/HOAc (50:49:1, v/v/v))
using probes of the invention. FIG. 5B is a MS/MS spectrum of
serine (concentration: 100 ppb, volume: 10 .mu.l, solvent:
MeOH/H.sub.2O/HOAc (50:49:1, v/v/v)).
[0020] FIG. 6A is a MS spectrum of peptide bradykinin2-9
(concentration: 10 ppm, volume: 10 .mu.l, solvent:
MeOH/H.sub.2O/HOAc (50:49:1, v/v/v)) using probes of the invention.
FIG. 6B is a MS/MS spectrum of bradykinin2-9 (concentration: 1 ppm,
volume: 10 .mu.l, solvent: MeOH/H.sub.2O/HOAc (50:49:1,
v/v/v)).
[0021] FIG. 7A is a MS/MS spectrum showing that heroin can be
detected from whole blood sample by a "spot" method. FIG. 7B shows
the MS/MS spectrum of the blood spot without heroin.
[0022] FIG. 8A MS/MS spectrum shows heroin can be detected from raw
urine sample by a "spot" method. FIG. 8B shows the MS/MS spectrum
of the urine spot without heroin.
[0023] FIG. 9A is a MS spectrum showing the caffeine detected from
a cola drink without sample preparation. FIG. 9B is a MS spectrum
showing caffeine detected from coffee powder. A paper slice was
used to collect the coffee powder from a coffee bag by swabbing the
surface.
[0024] FIGS. 10A-B show MS spectra of urine analysis without sample
preparation. FIG. 10A is a MS spectrum showing that caffeine was
detected in urine from a person who consumed coffee. FIG. 10B is a
MS spectrum showing that caffeine was not detected in urine from a
person who had not consumed any coffee.
[0025] FIGS. 11A-B are MS spectra showing the difference between
peptide analysis (10 ppm of bradykinin 2-9) on (FIG. 11A) paper
triangle and (FIG. 11B) PVDF membrane using the same parameters
(.about.2 kV, Solvent: MeOH:H.sub.2O=1:1).
[0026] FIGS. 12A-D show direct MS spectra of plant tissues using
sliced tissues of four kinds of plants. (FIG. 12A) Onion, (FIG.
12B) Spring onion, and two different leaves (FIG. 12C) and (FIG.
12D).
[0027] FIGS. 13A-B show MS/MS spectra of Vitamin C. FIG. 13A direct
analysis of onion without sample preparation. FIG. 13B using
standard solution.
[0028] FIG. 14A is a picture showing dried blood spot analysis on
paper; 0.4 .mu.L of whole blood is applied directly to a triangular
section of chromatography paper (typically height 10 mm, base 5
mm). A copper clip holds the paper section in front of the inlet of
an LTQ mass spectrometer (Thermo Fisher Scientific, San Jose,
Calif.) and a DC voltage (4.5 kV) is applied to the paper wetted
with 10 .mu.L methanol/water (1:1 v/v). FIG. 14B shows the
molecular structure of imatinib (GLEEVEC) and paper spray tandem
mass spectrum of 0.4 .mu.L whole blood containing 4 .mu.g/mL
imatinib. Imatinib is identified and quantified (inset) by the
MS/MS transition m/z 494.fwdarw.m/z 394 (inset). FIG. 14C shows a
quantitative analysis of whole blood spiked with imatinib (62.5-4
.mu.g/mL) and its isotopomers imatinib-d8 (1 .mu.g/mL). Inset plot
shows low concentration range.
[0029] FIG. 15 is a paper spray mass spectrum of angiotensin I
solution. The inset shows an expanded view over the mass range
630-700.
[0030] FIG. 16 is a mass spectrum showing direct analysis of
hormones in animal tissue by probes of the invention.
[0031] FIGS. 17A-B are mass spectra showing direct analysis of
human prostate tumor tissue and normal tissue.
[0032] FIG. 18 is a mass spectrum of whole blood spiked with 10
.mu.g/mL atenolol. The data was obtained by combining systems and
methods of the invention with a handheld mass spectrometer.
[0033] FIGS. 19A-F show mass spectra of cocaine sprayed from six
different types of paper (Whatman filter paper with different pore
sizes: (FIG. 19A) 3 .mu.m, (FIG. 19B) 4-7 .mu.m, (FIG. 19C) 8
.mu.m, and (FIG. 19D) 11 .mu.m, (FIG. 19E) glass fiber paper and
(FIG. 19F) chromatography paper). The spray voltage was 4.5 kV.
[0034] FIG. 20A shows a schematic setup for characterizing the
spatial distribution of paper spray. FIG. 20B is a 2D contour plot
showing the relative intensity of m/z 304 when the probe is moved
in the x-y plane with respect to the inlet of the mass
spectrometer. FIG. 20C is a graph showing signal duration of m/z
304 when loading cocaine solution on paper with different
concentrations or volumes, or sealed by Teflon membrane.
[0035] FIGS. 21A-D are a set of MS spectra of pure chemical
solutions and their corresponding MS/MS spectra. Spectra were
obtained for (FIG. 21A) serine, (FIG. 21B) methadone, (FIG. 21C)
roxithromycin, and (FIG. 21D) bradykinin 2-9.
[0036] FIGS. 22A-G are a set of mass spectra showing analysis of
chemicals from complex mixtures and direct analysis from surfaces
without sample preparation. FIGS. 22A-B are mass spectra of
COCA-COLA (cola drink), which was directly analyzed on paper in
both of (FIG. 22A) positive and (FIG. 22B) negative mode. FIG. 22C
is a mass spectrum of caffeine. FIG. 22D is a mass spectrum of
potassium benzoate. FIG. 22E is a mass spectrum of acesulfame
potassium. FIG. 22F is a mass spectrum of caffeine detected from
urine. FIG. 22G is a mass spectrum of heroin detected directly from
a desktop surface after swabbing of the surface by probes of then
invention.
[0037] FIG. 23A shows images of a probe of the invention used for
blood analysis. In this embodiment, the porous material is paper.
The panel on the left is prior to spotting with whole blood. The
panel in the middle is after spotting with whole blood and allowing
the spot to dry. The panel on the right is after methanol was added
to the paper and allowed to travel through the paper. The panel on
the right shows that the methanol interacts with the blood spot,
causing analytes to travel to the tip of the paper for ionization
and analysis. FIG. 23B is a mass spectrum of Atenolol from whole
blood FIG. 23C is a mass spectrum of heroin from whole blood.
[0038] FIGS. 24A-C show analysis of two dyes, methylene blue (m/z
284) and methyl violet (m/z 358.5), separated by TLC. Dye mixture
solution (0.1 .mu.l of a 1 mg/mL solution) was applied onto the
chromatography paper (4 cm.times.0.5 cm) and dried before TLC and
paper spray MS analysis.
[0039] FIGS. 25A-E show different shapes, thicknesses, and angles
for probes of the invention. FIG. 25A shows sharpness. FIG. 25B
shows angle of the tip. FIG. 25C shows thickness of the paper. FIG.
25D shows a device with multiple spray tips. FIG. 25E shows a DBS
card with micro spray tips fabricated with sharp needles.
[0040] FIGS. 26A-B are a set of mass spectra of imatinib from human
serum using direct spray from a C4 zip-tip of conical shape. Human
serum samples (1.5 .mu.L each) containing imatinib were passed
through the porous C4 extraction material three times and then 3
.mu.L methanol was added onto the zip-tip with 4 kV positive DC
voltage applied to produce the spray. FIG. 26A shows a MS spectrum
for 5 .mu.g/mL. FIG. 26B shows a MS/MS spectrum for 5 ng/mL.
[0041] FIG. 27A is a picture showing different tip angles for
probes of the invention. From left to right, the angles are 30, 45,
90, 112, 126 degree, respectively. FIG. 27B is a graph showing the
effect of angle on MS signal intensity. All MS signals were
normalized to the MS signal using the 90 degree tip.
[0042] FIG. 28A is a picture of a high-throughput probe device of
the invention. FIG. 28B shows spray from a single tip of the device
into an inlet of a mass spectrometer. FIG. 28C is a set of mass
spectra showing MS signal intensity in high-throughput mode.
[0043] FIG. 29A is a schematic depicting a protocol for direct
analysis of animal tissue using probes of the invention. FIGS.
29B-D are mass spectra showing different chemicals detected in the
tissue.
[0044] FIG. 30A shows a mass spectral analysis of a dried serum
spot on plain paper. FIG. 30B shows a mass spectrum analysis of a
dried serum sport on paper preloaded with betaine aldehyde (BA)
chloride. FIG. 30C shows a MS/MS analysis of reaction product
[M+BA].sup.+ (m/z 488.6).
[0045] FIGS. 31A-B show MS/MS spectra recorded with modified (FIG.
31A) and unmodified (FIG. 31B) paper substrates.
[0046] FIG. 32 is a mass spectrum showing that ions can be
generated using a negative ion source potential but positively
charged ions are mass-analyzed.
[0047] FIG. 33A is a schematic showing the design of a sample
cartridge with volume control and overflowing vials. A soluble plug
with internal standard chemical is used to block the bottom of the
volume control vial. FIG. 33B shows a step-by-step process of
applying blood samples onto the cartridge to prepare a dried blood
spot on paper from a controlled volume of blood.
[0048] FIGS. 34A-B show mass spectra of agrochemicals that are
present on a lemon peel purchased from a grocery store and swabbed
with paper.
[0049] FIG. 35 shows a design of a substrate for paper spray with
multiple corners. The angle of the corner to be used for spray is
smaller than that of other corners.
[0050] FIGS. 36A-B show a spray tip fabricated on a piece of
chromatography paper using SU-8 2010 photoresist. FIG. 36C shows a
MS spectrum of methanol/water solution containing a mixture of
asparagines.
[0051] FIG. 37 shows an exemplary method of collecting
microorganisms onto probes of the invention when the sample is a
gas/aerosol.
[0052] FIG. 38 shows an exemplary method of collecting
microorganisms onto probes of the invention when the sample is a
liquid.
[0053] FIGS. 39A-B show mass spectra of E. coli. FIG. 39A is
negative ion mode and FIG. 39B is positive ion mode.
[0054] FIG. 40 show a mass spectra of different microorganisms. The
top panel is a mass spectrum of staphylococcus capitis. The bottom
panel is a mass spectrum of staphylococcus saprophyticus
[0055] FIG. 41 shows a mass spectrum of E. coli acquired in
negative mode.
[0056] FIG. 42 shows a mass spectrum of E. coli acquired in
positive mode.
[0057] FIG. 43 is a graph showing a principal component analysis of
different microorganisms.
[0058] FIG. 44 is a similarity comparison of different
organisms.
[0059] FIGS. 45A-F show a workflow for comparing a mass spectrum of
an unknown microorganism to a database including mass spectra of
known microorganisms to identify the unknown microorganism.
DETAILED DESCRIPTION
[0060] A new method of generating ions from fluids and solids for
mass spectrometry analysis is described. Porous materials, such as
paper (e.g. filter paper or chromatographic paper) or other similar
materials are used to hold and transfer liquids and solids, and
ions are generated directly from the edges of the material when a
high electric voltage is applied to the material (FIG. 1). The
porous material is kept discrete (i.e., separate or disconnected)
from a flow of solvent, such as a continuous flow of solvent.
Instead, sample is either spotted onto the porous material or
swabbed onto it from a surface including the sample. The spotted or
swabbed sample is then connected to a high voltage source to
produce ions of the sample which are subsequently mass analyzed.
The sample is transported through the porous material without the
need of a separate solvent flow. Pneumatic assistance is not
required to transport the analyte; rather, a voltage is simply
applied to the porous material that is held in front of a mass
spectrometer.
[0061] In certain embodiments, the porous material is any
cellulose-based material. In other embodiments, the porous material
is a non-metallic porous material, such as cotton, linen wool,
synthetic textiles, or plant tissue. In still other embodiments,
the porous material is paper. Advantages of paper include: cost
(paper is inexpensive); it is fully commercialized and its physical
and chemical properties can be adjusted; it can filter particulates
(cells and dusts) from liquid samples; it is easily shaped (e.g.,
easy to cut, tear, or fold); liquids flow in it under capillary
action (e.g., without external pumping and/or a power supply); and
it is disposable.
[0062] In certain embodiments, the porous material is integrated
with a solid tip having a macroscopic angle that is optimized for
spray. In these embodiments, the porous material is used for
filtration, pre-concentration, and wicking of the solvent
containing the analytes for spray at the solid type.
[0063] In particular embodiments, the porous material is filter
paper. Exemplary filter papers include cellulose filter paper,
ashless filter paper, nitrocellulose paper, glass microfiber filter
paper, and polyethylene paper. Filter paper having any pore size
may be used. Exemplary pore sizes include Grade 1 (11 .mu.m), Grade
2 (8 .mu.m), Grade 595 (4-7 .mu.m), and Grade 6 (3 .mu.m), Pore
size will not only influence the transport of liquid inside the
spray materials, but could also affect the formation of the Taylor
cone at the tip. The optimum pore size will generate a stable
Taylor cone and reduce liquid evaporation. The pore size of the
filter paper is also an important parameter in filtration, i.e.,
the paper acts as an online pretreatment device. Commercially
available ultra filtration membranes of regenerated cellulose, with
pore sizes in the low nm range, are designed to retain particles as
small as 1000 Da. Ultra filtration membranes can be commercially
obtained with molecular weight cutoffs ranging from 1000 Da to
100,000 Da.
[0064] Probes of the invention work well for the generation of
micron scale droplets simply based on using the high electric field
generated at an edge of the porous material. In particular
embodiments, the porous material is shaped to have a
macroscopically sharp point, such as a point of a triangle, for ion
generation. Probes of the invention may have different tip widths.
In certain embodiments, the probe tip width is at least about 5
.mu.m or wider, at least about 10 .mu.m or wider, at least about 50
.mu.m or wider, at least about 150 .mu.m or wider, at least about
250 .mu.m or wider, at least about 350 .mu.m or wider, at least
about 400 .mu.m or wider, at least about 450 .mu.m or wider, etc.
In particular embodiments, the tip width is at least 350 .mu.m or
wider. In other embodiments, the probe tip width is about 400
.mu.m. In other embodiments, probes of the invention have a three
dimensional shape, such as a conical shape.
[0065] As mentioned above, no pneumatic assistance is required to
transport the droplets. Ambient ionization of analytes is realized
on the basis of these charged droplets, offering a simple and
convenient approach for mass analysis of solution-phase
samples.
[0066] Sample solution is directly applied on the porous material
held in front of an inlet of a mass spectrometer without any
pretreatment. Then the ambient ionization is performed by applying
a high potential on the wetted porous material. In certain
embodiments, the porous material is paper, which is a type of
porous material that contains numerical pores and microchannels for
liquid transport. The pores and microchannels also allow the paper
to act as a filter device, which is beneficial for analyzing
physically dirty or contaminated samples.
[0067] In other embodiments, the porous material is treated to
produce microchannels in the porous material or to enhance the
properties of the material for use as a probe of the invention. For
example, paper may undergo a patterned silanization process to
produce microchannels or structures on the paper. Such processes
involve, for example, exposing the surface of the paper to
tridecafluoro-1,1,2,2-tetrahydrooctyl-1-trichlorosilane to result
in silanization of the paper. In other embodiments, a soft
lithography process is used to produce microchannels in the porous
material or to enhance the properties of the material for use as a
probe of the invention. In other embodiments, hydrophobic trapping
regions are created in the paper to pre-concentrate less
hydrophilic compounds.
[0068] Hydrophobic regions may be patterned onto paper by using
photolithography, printing methods or plasma treatment to define
hydrophilic channels with lateral features of 200-1000 .mu.m. See
Martinez et al. (Angew. Chem. Int. Ed. 2007, 46, 1318-1320);
Martinez et al. (Proc. Natl. Acad. Sci. USA 2008, 105,
19606-19611); Abe et al. (Anal. Chem. 2008, 80, 6928-6934);
Bruzewicz et al. (Anal. Chem. 2008, 80, 3387-3392); Martinez et al.
(Lab Chip 2008, 8, 2146-2150); and Li et al. (Anal. Chem. 2008, 80,
9131-9134), the content of each of which is incorporated by
reference herein in its entirety. Liquid samples loaded onto such a
paper-based device can travel along the hydrophilic channels driven
by capillary action.
[0069] Another application of the modified surface is to separate
or concentrate compounds according to their different affinities
with the surface and with the solution. Some compounds are
preferably absorbed on the surface while other chemicals in the
matrix prefer to stay within the aqueous phase. Through washing,
sample matrix can be removed while compounds of interest remain on
the surface. The compounds of interest can be removed from the
surface at a later point in time by other high-affinity solvents.
Repeating the process helps desalt and also concentrate the
original sample.
[0070] Methods and systems of the invention use a porous material,
e.g., paper, to hold and transport analytes for mass spectral
analysis. Analytes in samples are pre-concentrated, enriched and
purified in the porous material in an integrated fashion for
generation of ions with application of a high voltage to the porous
material. In certain embodiments, a discrete amount of transport
solution (e.g., a droplet or a few droplets) is applied to assist
movement of the analytes through the porous material. In certain
embodiments, the analyte is already in a solution that is applied
to the porous material. In such embodiments, no additional solvent
need be added to the porous material. In other embodiments, the
analyte is in a powdered sample that can be easily collected by
swabbing a surface. Systems and methods of the invention allow for
analysis of plant or animal tissues, or tissues in living
organisms.
[0071] Methods and systems of the invention can be used for
analysis of a wide variety of small molecules, including
epinephrine, serine, atrazine, methadone, roxithromycin, cocaine
and angiotensin I. All display high quality mass and MS/MS product
ion spectra (see Examples below) from a variety of porous surfaces.
Methods and systems of the invention allow for use of small volumes
of solution, typically a few .mu.L, with analyte concentrations on
the order of 0.1 to 10 .mu.g/mL (total amount analyte 50 pg to 5
ng) and give signals that last from one to several minutes.
[0072] Methods and systems of the invention can be used also for
analysis of a wide variety of biomolecules, including proteins and
peptides. Methods of the invention can also be used to analyze
oligonucleotides from gels. After electrophoretic separation of
oligonucleotides in the gel, the band or bands of interest are
blotted with porous material using methods known in the art. The
blotting results in transfer of at least some of the
oligonucleotides in the band in the gel to the porous material. The
porous material is then connected to a high voltage source and the
oligonucleotides are ionized and sprayed into a mass spectrometer
for mass spectral analysis.
[0073] Methods and systems of the invention can be used for
analysis of complex mixtures, such as whole blood or urine. The
typical procedure for the analysis of pharmaceuticals or other
compounds in blood is a multistep process designed to remove as
many interferences as possible prior to analysis. First, the blood
cells are separated from the liquid portion of blood via
centrifugation at approximately 1000.times.g for 15 minutes
(Mustard, J. F.; Kinlough-Rathbone, R. L.; Packham, M. A. Methods
in Enzymology; Academic Press, 1989). Next, the internal standard
is spiked into the resulting plasma and a liquid-liquid or
solid-phase extraction is performed with the purpose of removing as
many matrix chemicals as possible while recovering nearly all of
the analyte (Buhrman, D. L.; Price, P. I.; Rudewicz, P. J. Journal
of the American Society for Mass Spectrometry 1996, 7, 1099-1105).
The extracted phase is typically dried by evaporating the solvent
and then resuspended in the a solvent used as the high performance
liquid chromatography (HPLC) mobile phase (Matuszewski, B. K.;
Constanzer, M. L.; Chavez-Eng, C. M., Ithaca, N.Y., Jul. 23-25
1997; 882-889). Finally, the sample is separated in the course of
an HPLC run for approximately 5-10 minutes, and the eluent is
analyzed by electrospray ionization-tandem mass spectrometry
(Hopfgartner, G.; Bourgogne, E. Mass Spectrometry Reviews 2003, 22,
195-214).
[0074] Methods and systems of the invention avoid the above sample
work-up steps. Methods and systems of the invention analyze a dried
blood spots in a similar fashion, with a slight modification to the
extraction procedure. First, a specialized device is used to punch
out identically sized discs from each dried blood spot. The
material on these discs is then extracted in an organic solvent
containing the internal standard (Chace, D. H.; Kalas, T. A.;
Naylor, E. W. Clinical Chemistry 2003, 49, 1797-1817). The
extracted sample is dried on the paper substrate, and the analysis
proceeds as described herein.
[0075] Examples below show that methods and systems of the
invention can directly detect individual components of complex
mixtures, such as caffeine in urine, 50 pg of cocaine on a human
finger, 100 pg of heroin on a desktop surface, and hormones and
phospholipids in intact adrenal tissue, without the need for sample
preparation prior to analysis (See Examples below). Methods and
systems of the invention allow for simple imaging experiments to be
performed by examining, in rapid succession, needle biopsy tissue
sections transferred directly to paper.
[0076] Analytes from a solution are applied to the porous material
for examination and the solvent component of the solution can serve
as the electrospray solvent. In certain embodiments, analytes
(e.g., solid or solution) are pre-spotted onto the porous material,
e.g., paper, and a solvent is applied to the material to dissolve
and transport the analyte into a spray for mass spectral
analysis.
[0077] In certain embodiments, a solvent is applied to the porous
material to assist in separation/extraction and ionization. Any
solvents may be used that are compatible with mass spectrometry
analysis. In particular embodiments, favorable solvents will be
those that are also used for electrospray ionization. Exemplary
solvents include combinations of water, methanol, acetonitrile, and
THF. The organic content (proportion of methanol, acetonitrile,
etc. to water), the pH, and volatile salt (e.g. ammonium acetate)
may be varied depending on the sample to be analyzed. For example,
basic molecules like the drug imatinib are extracted and ionized
more efficiently at a lower pH. Molecules without an ionizable
group but with a number of carbonyl groups, like sirolimus, ionize
better with an ammonium salt in the solvent due to adduct
formation.
[0078] In certain embodiments, a multi-dimensional approach is
undertaken. For example, the sample is separated along one
dimension, followed by ionization in another dimension. In these
embodiments, separation and ionization can be individually
optimized, and different solvents can be used for each phase.
[0079] In other embodiments, transporting the analytes on the paper
is accomplished by a solvent in combination with an electric field.
When a high electric potential is applied, the direction of the
movement of the analytes on paper is found to be related to the
polarity of their charged forms in solution. Pre-concentration of
the analyte before the spray can also be achieved on paper by
placing an electrode at a point on the wetted paper. By placing a
ground electrode near the paper tip, a strong electric field is
produced through the wetted porous material when a DC voltage is
applied, and charged analytes are driven forward under this
electric field. Particular analytes may also be concentrated at
certain parts of the paper before the spray is initiated.
[0080] In certain embodiments, chemicals are applied to the porous
material to modify the chemical properties of the porous material.
For example, chemicals can be applied that allow differential
retention of sample components with different chemical properties.
Additionally, chemicals can be applied that minimize salt and
matrix effects. In other embodiments, acidic or basic compounds are
added to the porous material to adjust the pH of the sample upon
spotting. Adjusting the pH may be particularly useful for improved
analysis of biological fluids, such as blood. Additionally,
chemicals can be applied that allow for on-line chemical
derivatization of selected analytes, for example to convert a
non-polar compound to a salt for efficient electrospray
ionization.
[0081] In certain embodiments, the chemical applied to modify the
porous material is an internal standard. The internal standard can
be incorporated into the material and released at known rates
during solvent flow in order to provide an internal standard for
quantitative analysis. In other embodiments, the porous material is
modified with a chemical that allows for pre-separation and
pre-concentration of analytes of interest prior to mass spectrum
analysis.
[0082] The spray droplets can be visualized under strong
illumination in the positive ion mode and are comparable in size to
the droplets emitted from a nano-electrospray ion sources (nESI).
In the negative ion mode, electrons are emitted and can be captured
using vapor phase electron capture agents like benzoquinone.
Without being limited by any particular theory or mechanism of
action, it is believed that the high electric field at a tip of the
porous material, not the fields in the individual fluid channels,
is responsible for ionization.
[0083] The methodology described here has desirable features for
clinical applications, including neotal screening, therapeutic drug
monitoring and tissue biopsy analysis. The procedures are simple
and rapid. The porous material serves a secondary role as a filter,
e.g., retaining blood cells during analysis of whole blood.
Significantly, samples can be stored on the porous material and
then analyzed directly from the stored porous material at a later
date without the need transfer from the porous material before
analysis. Systems of the invention allow for laboratory experiments
to be performed in an open laboratory environment.
INCORPORATION BY REFERENCE
[0084] References and citations to other documents, such as
patents, patent applications, patent publications, journals, books,
papers, web contents, have been made throughout this disclosure.
All such documents are hereby incorporated herein by reference in
their entirety for all purposes.
EQUIVALENTS
[0085] Various modifications of the invention and many further
embodiments thereof, in addition to those shown and described
herein, will become apparent to those skilled in the art from the
full contents of this document, including references to the
scientific and patent literature cited herein. The subject matter
herein contains important information, exemplification and guidance
that can be adapted to the practice of this invention in its
various embodiments and equivalents thereof.
EXAMPLES
[0086] The following examples are intended to further illustrate
certain embodiments of the invention, and are not to be construed
to limit the scope of the invention. Examples herein show that mass
spectrometry probes of the invention can ionize chemical and
biological samples, allowing for subsequent mass analysis and
detection. An exemplary probe was constructed as a paper triangle,
which was used to generate micron scale droplets by applying a high
potential on the paper. The analytes were ionized from these
electrically charged droplets and transported into a conventional
mass spectrometer.
[0087] Examples below show that a wide range of samples could be
directly analyzed in the ambient environment by probes of the
invention in both of pure state and complex mixtures. The results
showed that paper-based spray has the following benefits: it
operated without sheath gas, i.e., few accessories were required
for in situ analysis; biological samples (dried blood, urine) could
be stored on the precut filter papers for months before analysis;
filter paper minimized matrix effects seen with electrospray or
nano electrospray in many samples (blood cells, salt and proteins)
and enhanced the MS signal of chemicals in complex samples;
powdered samples were easily collected by swabbing surfaces using
paper pieces and then directly analyzed; the paper could be
pretreated to contain internal standards that were released at
known rates during solvent flow in quantitative analysis; and the
paper could be pretreated to contain matrix suppression or
absorption sites or to perform ion exchange or to allow on-line
chemical derivatization of selected analytes.
[0088] Detection of most analytes was achieved as low as ppb levels
(when examined as solutions) or in the low ng to pg range (when
solids were examined) and the detection time was less than one
minute. Certain Examples below provide a protocol for analyzing a
dried blood spot, which can also be used for in situ analysis of
whole blood samples. The dried blood spot method is also
demonstrated to be compatible with the storage and transport of
blood sample for blood screening and other clinical tests.
[0089] Devices of the invention integrated the capabilities of
sampling, pre-separation, pre-concentration and ionization. Methods
and systems of the invention simplify the problem of sample
introduction in mass analyzers.
Example 1
Construction of an MS Probe
[0090] Filter paper was cut into triangular pieces with dimensions
of 10 mm long and 5 mm wide and used as a sprayer (FIGS. 1A-B). A
copper clip was attached to the paper, and the paper was oriented
to face an inlet of a mass spectrometer (FIGS. 1A-B). The copper
clip was mounted on a 3D moving stage to accurately adjust its
position. A high voltage was applied to the copper clip and
controlled by a mass spectrometer to generate analyte ions for mass
detection.
[0091] Samples were directly applied to the paper surface that
served as a sample purification and pre-concentration device.
Filter paper allowed liquid samples to move through the hydrophilic
network driven by capillary action and electric effects and to
transport them to the tip of the paper. Separation could take place
during this transport process. Sample solution was sprayed from the
tip and resulted in ionization and MS detection when a high voltage
(.about.4.5 kV) was applied to the paper surface.
[0092] All experiments were carried out with a Finnigan LTQ mass
spectrometer (Thermo Electron, San Jose, Calif.). The typical
temperature of the capillary inlet was set at 150.degree. C. while
30.degree. C. for heroin detection. The lens voltage was set at 65
V for sample analysis and 240 V for survival yield experiment.
Tandem mass spectra were collected using collision-induced
dissociation (CID) to identify analytes in tested samples,
especially for complex mixtures and blood samples.
Example 2
Spray Generation
[0093] Spray was produced by applying a high potential on the
wetted paper triangle. One paper triangle was placed in front of
the inlet of LTQ with its sharp tip facing to the inlet, separated
by 3 mm or more. Typically, 10 uL sample solution was applied to
wet the paper triangle. The solution can wet or saturate the paper
or form a thin layer of liquid film on the surface of the paper. A
high potential (3-5 kV) was applied between the paper triangle and
mass inlet to generate an electric field, which induced a charge
accumulation on the liquid at the tip of paper triangle. The
increasing coulombic force breaks the liquid to form charged
droplets and then the solvent evaporated during the flight of
droplets from the paper tip to the mass analyzer. Paper spray
required no sheath gas, heating or any other assistance to remove
the solvent.
[0094] When liquid accumulated on the paper triangle, a Taylor cone
was observed at the tip when examined with a microscope. The
droplets formed were clearly visible under strong illumination. The
Taylor cone and visible spray disappeared after a short time of
evaporation and spray. However, the mass signal lasted for a much
longer period (several minutes). This revealed that the paper
triangle could work in two modes for mass analysis. In a first
mode, the liquid was transported inside the paper at a rate faster
than the liquid could be consumed as spray at the paper tip,
resulting in a large cone being formed at the paper tip and
droplets being generated. In a second mode, the liquid transport
inside the paper was not able to move at a rate fast enough to keep
up with the spray consumption, and droplets were not visible.
However, it was observed that ionization of analytes did take
place. The first mode provided ESI like mass spectra and the second
mode provided spectra with some of the features APCI spectra. In
the latter case, the paper triangle played a role analogous to a
conductive needle to generate a high electric field to ionize the
molecules in the atmosphere. It was observed that the mass signal
in the first mode was stronger than the mass signal in the second
mode by approximately two orders of magnitude under the conditions
and for the samples tested.
Example 3
Probe Considerations
[0095] Probe Materials
[0096] A number of porous materials were tested to generate charged
droplets for mass spectrometry. The materials were shaped into
triangles having sharp tips and sample solution was then applied to
the constructed probes. Data herein show that any hydrophilic and
porous substrate could be used successfully, including cotton swab,
textile, plant tissues as well as different papers. The porous
network or microchannels of these materials offered enough space to
hold liquid and the hydrophilic environment made it possible for
liquid transport by capillary action. Hydrophobic and porous
substrates could also be used successfully with properly selected
hydrophobic solvents.
[0097] For further investigation, six kinds of commercialized
papers were selected and qualitatively tested to evaluate their
capabilities in analyte detection. Filter papers and chromatography
paper were made from cellulose, while glass microfiber filter paper
was made from glass microfiber. FIGS. 19A-F shows the mass spectra
of cocaine detection on those papers. The spectrum of glass fiber
paper (FIG. 19E) was unique because the intensity of background was
two orders of magnitude lower than other papers and the cocaine
peak (m/z, 304) could not be identified.
[0098] It was hypothesized that the glass fiber paper was working
on mode II and prohibiting efficient droplet generation, due to the
relative large thickness (.about.2 mm). This hypothesis was proved
by using a thin layer peeled from glass fiber paper for cocaine
detection. In that case, the intensity of the background increased
and a cocaine peak was observed. All filter papers worked well for
cocaine detection, (FIGS. 19A-D). Chromatography paper showed the
cleanest spectrum and relative high intensity of cocaine (FIG.
19F).
[0099] Probe Shape and Tip Angle
[0100] Many different probe shapes were investigated with respect
to generating droplets. A preferred shape of the porous material
included at least one tip. It was observed that the tip allowed
ready formation of a Taylor cone. A probe shape of a triangle was
used most often. As shown in FIGS. 25A-C, the sharpness of the tip,
the angle of the tip (FIGS. 27A-B), and the thickness of the paper
substrate could effect the spray characteristics. The device of a
tube shape with multiple tips (FIG. 25D) is expected to act as a
multiple-tip sprayer, which should have improved spray efficiency.
An array of micro sprayers can also be fabricated on a DBS card
using sharp needles to puncture the surface (FIG. 25E).
Example 4
Configuration of Probe with Inlet of a Mass Spectrometer
[0101] A paper triangle was mounted on a 2D moving stage to
determine how the mass signal was affected by the relative
positions of the paper triangle and the mass spectrometer inlet.
The paper triangle was moved 8 cm in the y-direction in a
continuous manner and 3 cm in the x-direction with a 2 mm increment
for each step (FIG. 20A). Cocaine solution (1 ug/mL,
methanol/water, 1:1 v/v) was continuously fed onto the paper
surface. The mass spectrum was continuously recorded during the
entire scan. A contour plot of the peak intensity of protonated
cocaine (m/z, 304) was created from the normalized data extracted
from the mass spectrum (FIG. 20B). The contour plot shows that it
was not necessary for the paper triangle to be placed directly
in-line with the inlet of the mass spectrometer to generate
droplets.
[0102] Spray duration was also tested (FIG. 20C). Paper triangles
(size 10 mm, 5 mm) were prepared. First, 10 uL solutions were
applied on the paper triangles with different concentration of 0.1,
1 and 10 ug/mL. The spray time for each paper was just slightly
varied by the difference of concentration. After that, 1 ug/mL
cocaine solutions were applied on the paper triangles with
different volumes of 5 uL, 10 uL and 15 uL. The spray times showed
a linear response followed by the increasing sample volumes.
[0103] In another test, the paper was sealed with a PTFE membrane
to prevent evaporation of solution, which prolonged the spray time
by about three times. These results indicate that paper spray
offers long enough time of spray for data acquisition even using 5
uL solution, and the intensity of signal is stable during the
entire spray period.
Example 5
Separation and Detection
[0104] Probes of the invention include a porous material, such as
paper, that can function to both separate chemicals in biological
fluids before in situ ionization by mass spectrometry. In this
Example, the porous material for the probe was chromatography
paper. As shown in FIG. 24A-C, a mixture of two dyes was applied to
the paper as a single spot. The dyes were first separated on the
paper by TLC (thin layer chromatograph) and the separated dyes were
examined using MS analysis by methods of the invention with the
paper pieces cut from the paper media (FIGS. 24A-C). Data show the
separate dyes were detected by MS analysis (FIGS. 24A-C).
[0105] The chromatography paper thus allowed for sample collection,
analyte separation and analyte ionization. This represents a
significant simplification of coupling chromatography with MS
analysis. Chromatography paper is a good material for probes of the
invention because such material has the advantage that solvent
movement is driven by capillary action and there is no need for a
syringe pump. Another advantage is that clogging, a serious problem
for conventional nanoelectrospray sources, is unlikely due to its
multi-porous characteristics. Therefore, chromatography paper, a
multi-porous material, can be used as a microporous electrospray
ionization source.
Example 6
Pure Compounds: Organic Drugs, Amino Acids, and Peptides
[0106] As already described, probes and methods of the invention
offer a simple and convenient ionization method for mass
spectrometry. Paper triangles were spotted with different compounds
and connected to a high voltage source to produce ions. All
experiments were carried out with a Finnigan LTQ mass spectrometer
(Thermo Electron, San Jose, Calif.). Data herein show that a
variety of chemicals could be ionized in solution phase, including
amino acid, therapeutic drugs, illegal drugs and peptides.
[0107] FIG. 2A shows an MS spectrum of heroin (concentration: 1
ppm, volume: 10 .mu.l, solvent: MeOH/H.sub.2O/HOAc (50:49:1,
v/v/v)) using probes of the invention. FIG. 2B shows MS/MS spectrum
of heroin (concentration: 1 ppb, volume: 10 .mu.l, solvent:
MeOH/H.sub.2O/HOAc (50:49:1, v/v/v)).
[0108] FIG. 3A shows MS spectrum of caffeine (concentration: 10
ppm, volume: 10 .mu.l, solvent: MeOH/H.sub.2O/HOAc (50:49:1,
v/v/v)) using probes of the invention. FIG. 3B shows MS/MS spectrum
of caffeine (concentration: 10 ppb, volume: 10 .mu.l, solvent:
MeOH/H.sub.2O/HOAc (50:49:1, v/v/v)). Peak 167 also exists in the
blank spectrum with solvent and without caffeine.
[0109] FIG. 4A shows MS spectrum of benzoylecgonine (concentration:
10 ppm, volume: 10 .mu.l, solvent: MeOH/H.sub.2O/HOAc (50:49:1,
v/v/v)) using probes of the invention. FIG. 4B shows MS/MS spectrum
of benzoylecgonine (concentration: 10 ppb, volume: 10 .mu.l,
solvent: MeOH/H.sub.2O/HOAc (50:49:1, v/v/v)).
[0110] FIG. 5A shows MS spectrum of serine (concentration: 1 ppm,
volume: 10 .mu.l, solvent: MeOH/H.sub.2O/HOAc (50:49:1, v/v/v))
using probes of the invention. FIG. 5B shows MS/MS spectrum of
serine (concentration: 100 ppb, volume: 10 .mu.l, solvent:
MeOH/H.sub.2O/HOAc (50:49:1, v/v/v)). Peak 74 and 83 also exist in
the blank spectrum with solvent and without serine. FIG. 21A shows
MS spectrum of serine (m/z, 106) using probes of the invention.
FIG. 21A also shows MS/MS spectrum of serine (m/z, 106).
[0111] FIG. 21B shows MS spectrum of methadone (m/z, 310) using
probes of the invention. FIG. 21B also shows MS/MS spectrum of
methadone (m/z, 310). FIG. 21C shows MS spectrum of roxithromycin
(m/z, 837) using probes of the invention. FIG. 21B also shows MS/MS
spectrum of roxithromycin (m/z, 837).
[0112] FIG. 6A shows MS spectrum of peptide bradykinin2-9
(concentration: 10 ppm, volume: 10 .mu.l, solvent:
MeOH/H.sub.2O/HOAc (50:49:1, v/v/v)) using probes of the invention.
FIG. 6B shows MS/MS spectrum of bradykinin2-9 (concentration: 1
ppm, volume: 10 .mu.l, solvent: MeOH/H.sub.2O/HOAc (50:49:1,
v/v/v)). The hump in the spectrum is assumed to be caused by
polymers, such as polyethylene glycol (PEG), which are frequently
added to materials in industry. FIG. 21D shows MS spectrum of
bradykinin 2-9 (m/z, 453) using probes of the invention. FIG. 21D
also shows MS/MS spectrum of bradykinin 2-9 (m/z, 453). FIG. 21D
further shows adduct ions [M+H] (m/z, 904), [M+2H].sup.2+ (m/z,
453), [M+H+Na].sup.2+ (m/z, 464) and [M+2Na].sup.2+ (m/z, 475). The
m/z 453 peak was double charged adduct ion confirmed by the MS/MS
spectrum.
[0113] FIGS. 11A-B are MS spectra showing the difference between
peptide analysis (10 ppm of bradykinin 2-9) on (FIG. 11A) paper
slice and (FIG. 11B) PVDF membrane using the same parameters
(.about.2 kV, Solvent: MeOH:H.sub.2O=1:1).
[0114] Data herein show that probes of the invention work well over
the mass/charge range from 50 to over 1000 for detection of pure
compounds. Data further shows that detection was achieved down to
as low as 1 ng/mL for most chemicals, including illegal drugs, such
as heroin, cocaine and methadone.
Example 7
Complex Mixtures
[0115] Complex mixtures such as urine, blood, and cola drink were
examined using methods, devices, and systems of the invention. All
experiments were carried out with a Finnigan LTQ mass spectrometer
(Thermo Electron, San Jose, Calif.).
[0116] FIG. 7A shows an MS/MS spectrum that shows that heroin was
detected from whole blood sample by a "spot" method. 0.4 .mu.l of
whole blood sample containing 200 ppb heroin was applied on the
center of the triangle paper to form a 1 mm.sup.2 blood spot. After
the spot was dry, 10 .mu.l of solvent (MeOH/H.sub.2O/HOAc (50:49:1,
v/v/v)) was applied to the rear end of the triangle paper. Due to
the capillary effect, the solvent moved forward and dissolved the
chemicals in the blood spot. Finally, electrospray occurred when
the solvent reached the tip of the paper. To demonstrate the
effectiveness of the "blood spot" method mentioned above, the whole
blood was added on the paper for electrospray directly. MS/MS
spectrum showed that heroin was not detected from 10 .mu.l of whole
blood sample, even when the concentration was as high as 20 ppm
(FIG. 7B).
[0117] FIG. 8A shows an MS/MS spectrum that shows that heroin can
be detected from raw urine sample by a "spot" method. 0.4 .mu.l of
raw urine sample containing 100 ppb heroin was applied on the
center of the triangle paper to form a 1 mm.sup.2 urine spot. After
the spot was dry, 10 .mu.l of solvent (MeOH/H.sub.2O/HOAc (50:49:1,
v/v/v)) was applied to the rear end of the triangle paper. Due to
the capillary effect, the solvent moved forward and dissolved the
chemicals in the blood spot. Finally, electrospray occurred when
the solvent reached the tip of the paper. To demonstrate the
effectiveness of the "spot" method mentioned above, the raw urine
was added on the paper for electrospray directly. MS/MS spectrum
showed heroin was not detected from 10 .mu.l of raw urine sample
when concentration was 100 ppb (FIG. 8B).
[0118] FIG. 9A is an MS spectrum showing that caffeine was detected
from a cola drink without sample preparation. FIG. 9B is an MS
spectrum showing that caffeine was detected from coffee powder. A
paper triangle was used to collect the coffee powder from a coffee
bag by swabbing the surface.
[0119] FIGS. 22A-B show the spectra of COCA-COLA (cola drink),
analyzed in positive mode and negative mode, respectively. The peak
of protonated caffeine, m/z 195, identified in MS/MS spectrum, was
dominated in the mass spectrum in positive mode due to the high
concentration of caffeine (100 ug/mL) in this drink (FIG. 22C). Two
high concentrated compounds, potassium benzoate and acesulfame
potassium were identified in the MS/MS spectrum in negative mode
(FIGS. 22D-E).
[0120] FIG. 22F shows spectra of caffeine in urine from a person
who had drunk COCA-COLA (cola drink) two hours before the urine
collection. Urine typically contains urea in very high
concentration, which is also easily ionized. Therefore, protonated
urea [m/z, 61] and urea dimmer [m/z, 121] dominated the MS
spectrum. However, the protonated caffeine was identified in the
MS/MS spectrum, which showed good signal to noise ratio in the
urine sample.
[0121] FIGS. 10A-B show MS spectra of urine taken for analysis
without sample preparation. FIG. 10A is a mass spectra of caffeine
that was detected in urine from a person who had consumed coffee.
FIG. 10B is a mass spectra showing that caffeine was not detected
in urine from a person who had not consumed any coffee.
[0122] FIG. 22G shows the MS spectrum of heroin (m/z, 370)
collected as a swabbed sample. A 5 uL solution containing 50 ng
heroin was spotted on a 1 cm.sup.2 area of a desktop. The paper
triangle was wetted and used to swab the surface of the desktop.
The paper triangle was then connected to the high voltage source
for mass detection. This data shows that probes of the invention
can have dual roles of ionization source as well as a sampling
device for mass detection. Trace sample on solid surface could be
simply collected by swabbing the surface using probes of the
invention. Dust and other interferences were also collected on the
paper triangle, but the heroin could be directly detected from this
complex matrix.
Example 8
Plant Tissue Direct Analysis by ESI without Extraction
[0123] FIGS. 12A-D shows direct MS spectra of plant tissues using
sliced tissues of four kinds of plants. (FIG. 12A) Onion, (FIG.
12B) Spring onion, and two different leaves (FIG. 12C) and (FIG.
12D).
[0124] FIGS. 13A-B shows an MS/MS spectra of Vitamin C analysis
(FIG. 13A) direct analysis of onion without sample preparation,
(FIG. 13B) using standard solution.
Example 9
Whole Blood and Other Biofluids
[0125] Body fluids, such as plasma, lymph, tears, saliva, and
urine, are complex mixtures containing molecules with a wide range
of molecular weights, polarities, chemical properties, and
concentrations. Monitoring particular chemical components of body
fluids is important in a number of different areas, including
clinical diagnosis, drug development, forensic toxicology, drugs of
abuse detection, and therapeutic drug monitoring. Tests of blood,
including the derived fluids plasma and serum, as well as on urine
are particularly important in clinical monitoring.
[0126] A wide variety of chemicals from blood are routinely
monitored in a clinical setting. Common examples include a basic
metabolic panel measuring electrolytes like sodium and potassium
along with urea, glucose, and creatine and a lipid panel for
identifying individuals at risk for cardiovascular disease that
includes measurements of total cholesterol, high density
lipoprotein (HDL), low density lipoprotein (LDL), and
triglycerides. Most laboratory tests for chemicals in blood are
actually carried out on serum, which is the liquid component of
blood separated from blood cells using centrifugation. This step is
necessary because many medical diagnostic tests rely on
colorimetric assays and therefore require optically clear fluids.
After centrifugation, detection of the molecule of interest is
carried in a number of ways, most commonly by an immunoassay, such
as an enzyme-linked immunosorbent assay (ELISA) or radioimmunoas
say (RIA), or an enzyme assay in which the oxidation of the
molecule of interest by a selective enzyme is coupled to a reaction
with a color change, such as the tests for cholesterol (oxidation
by cholesterol oxidase) or glucose (oxidation by glucose
oxidase).
[0127] There is considerable interest in the pharmaceutical
sciences in the storage and transportation of samples of whole
blood as dried blood spots on paper (N. Spooner et al. Anal Chem.,
2009, 81, 1557). Most tests for chemicals found in blood are
carried out on a liquid sample, typically serum or plasma isolated
from the liquid whole blood. The required storage, transportation,
and handling of liquid blood or blood components present some
challenges. While blood in liquid form is essential for some tests,
others can be performed on blood or other body fluids that have
been spotted onto a surface (typically paper) and allowed to
dry.
[0128] Probes and methods of the invention can analyze whole blood
without the need for any sample preparation. The sample was
prepared as follows. 0.4 uL blood was directly applied on the
center of paper triangle and left to dry for about 1 min. to form a
dried blood spot (FIG. 23A). 10 uL methanol/water (1:1, v/v) was
applied near the rear end of the paper triangle. Driven by
capillary action, the solution traveled across the paper wetting it
throughout its depth. As the solution interacted with the dried
blood spot, the analytes from the blood entered the solution and
were transported to the tip of the probe for ionization (FIG. 23A).
The process of blood sample analysis was accomplished in about 2
min.
[0129] Different drugs were spiked into whole blood and the blood
was applied to probes of the invention as described above.
Detection of different drugs is described below.
[0130] Imatinib (GLEEVEC), a 2-phenylaminopyrimidine derivative,
approved by the FDA for treatment of chronic myelogenous leukemia,
is efficacious over a rather narrow range of concentrations. Whole
human blood, spiked with imatinib at concentrations including the
therapeutic range, was deposited on a small paper triangle for
analysis (FIG. 14A). The tandem mass spectrum (MS/MS, FIG. 14B) of
protonated imatinib, m/z 494, showed a single characteristic
fragment ion. Quantitation of imatinib in whole blood was achieved
using this signal and that for a known concentration of imatinib-d8
added as internal standard. The relative response was linear across
a wide range of concentrations, including the entire therapeutic
range (FIG. 14C).
[0131] Atenolol, a .beta.-blocker drug used in cardiovascular
diseases, was tested using the dried blood spot method to evaluate
paper spray for whole blood analysis. Atenolol was directly spiked
into whole blood at desired concentrations and the blood sample was
used as described above for paper spray. The protonated atenolol of
400 pg (1 ug/mL atenolol in 0.4 uL whole blood) in dried blood spot
was shown in mass spectra, and the MS/MS spectra indicated that
even 20 pg of atenolol (50 ug/mL atenolol in 0.4 uL whole blood)
could be identified in the dried blood spot (FIG. 23B).
[0132] FIG. 23C is a mass spectra of heroin in whole blood. Data
herein show that 200 pg heroin in dried blood spot could be
detected using tandem mass.
[0133] It was also observed that the paper medium served a
secondary role as a filter, retaining blood cells. Significantly,
samples were analyzed directly on the storage medium rather than
requiring transfer from the paper before analysis. All experiments
were done in the open lab environment. Two additional features
indicated that the methodology had the potential to contribute to
increasing the use of mass spectrometry in primary care facilities:
blood samples for analysis were drawn by means of a pinprick rather
than a canula; and the experiment was readily performed using a
handheld mass spectrometer (FIG. 18 and Example 10 below).
Example 10
Handheld Mass Spectrometer
[0134] Systems and methods of the invention were compatible with a
handheld mass spectrometer. Paper spray was performed using a
handheld mass spectrometer (Mini 10, custom made at Purdue
University). Analysis of whole blood spiked with 10 .mu.g/mL
atenolol. Methanol/water (1:1; 10 .mu.L) was applied to the paper
after the blood (0.4 uL) had dried (.about.1 min) to generate spray
for mass detection (FIG. 18). The inset shows that atenolol could
readily be identified in whole blood using tandem mass spectrum
even when the atenolol amount is as low as 4 ng.
Example 11
Angiotensin I
[0135] FIG. 15 is a paper spray mass spectrum of angiotensin I
solution (Asp-Arg-Val-Tyr-Ile-His-Pro-Phe-His-Leu (SEQ ID NO: 1),
10 .mu.L, 8 .mu.g/mL in methanol/water, 1:1, v/v) on chromatography
paper (spray voltage, 4.5 kV). The inset shows an expanded view
over the mass range 630-700. The protonated ([M+2H].sup.2+) and
sodium-adduct ions ([M+H+Na].sup.2+, [M+2Na].sup.2+) are the major
ionic species.
Example 12
Agrochemicals on Fruit
[0136] Sample collection by paper wiping followed by analysis using
probes of the invention was used for fast analysis of agrochemicals
on fruit. Chromatography paper (3.times.3 cm) wetted with methanol
was used to wipe a 10 cm.sup.2 area on the peel of a lemon
purchased from a grocery store. After the methanol had dried, a
triangle was cut from the center of the paper and used for paper
spray by applying 10 .mu.L methanol/water solution. The spectra
recorded (FIGS. 34A-B) show that a fungicide originally on the
lemon peel, thiabendazole (m/z 202 for protonated molecular ion and
m/z 224 for sodium adduct ion), had been collected onto the paper
and could be identified easily with MS and confirmed using MS/MS
analysis. Another fungicide imazalil (m/z 297) was also observed to
be present.
Example 13
Tumor Sample
[0137] Systems and methods of the invention were used to analyze
human prostate tumor tissue and normal tissue. Tumor and adjacent
normal tissue sections were 15 .mu.m thick and fixed onto a glass
slide for an imaging study using desorption electrospray ionization
(DESI). A metal needle was used to remove a 1 mm.sup.2.times.15
.mu.m volume of tissue from the glass slide from the tumor region
and then from the normal region and place them onto the surface of
the paper triangle for paper spray analysis.
[0138] A droplet of methanol/water (1:1 v:v; 10 .mu.l) was added to
the paper as solvent and then 4.5 kV positive DC voltage applied to
produce the spray. Phospholipids such as phosphatidylcholine (PC)
and sphingomyelin (SM) were identified in the spectrum (FIGS.
17A-B). The peak of [PC(34:1)+K].sup.+ at m/z 798 was significantly
higher in tumor tissue and peaks [SM(34:1)+Na].sup.+ at m/z 725,
[SM(36:0)+Na].sup.+ at m/z 756, and [SM(36:4)+Na].sup.+ at m/z 804
were significantly lower compared with normal tissue.
Example 14
Therapeutic Drug Monitoring
[0139] The administration of a drug depends on managing the
appropriate dosing guidelines for achievement of a safe and
effective outcome. This guideline is established during clinical
trials where the pharmacokinetics (PK) and pharmacodynamics (PD) of
the drug are studied. Clinical trials use PK-PD studies to
establish a standard dose, which may be fixed or adjusted according
formulas using variables like body mass, body surface area, etc.
However, the drug exposure, i.e. the amount of drug circulating
over time, is influenced by a number of factors that vary from
patient to patient. For example, an individuals' metabolic rate,
the type and level of plasma proteins, and pre-existing conditions
such as renal and/or hepatic impairment all play a role in
affecting the exposure of the drug in vivo. Further, administration
of a drug in combination with other medications may also affect
exposure. As a result, it is often difficult to predict and
prescribe an optimum regimen of drug administration.
[0140] Over- or underexposure to a drug can lead to toxic effects
or decreased efficacy, respectively. To address these concerns,
therapeutic drug monitoring (TDM) can be employed. TDM is the
measurement of active drug levels in the body followed by
adjustment of drug dosing or schedules to increase efficacy and/or
decrease toxicity. TDM is indicated when the variability in the
pharmacokinetics of a drug is large relative to the therapeutic
window, and there is an established relationship between drug
exposure and efficacy and/or toxicity. Another requirement for TDM
is that a sufficiently precise and accurate assay for the active
ingredient must be available. Immunoassays and liquid
chromatography mass spectrometry (LC-MS) are commonly used methods
for TDM. In comparison with immunoassay, LC-MS has advantages which
include wide applicability, high sensitivity, good quantitation,
high specificity and high throughput. Probes of the invention may
be coupled with standard mass spectrometers for providing
point-of-care therapeutic drug monitoring.
[0141] The drug Imatinib (GLEEVEC in USA and GLIVEC in
Europe/Australia, for the treatment of chronic myelogenous
leu-kemia) in a dried blood spot was analyzed using paper spray and
a lab-scale LTQ mass spectrometer. Quantitation of Imatinib in
whole blood was achieved using the MS/MS spectra with a known
concentration of Imatinib-d8 being used as the internal standard
(FIG. 14C). The relative response was linear across a wide range of
concentrations, including the entire therapeutic range (FIG.
14C).
Example 15
High-Throughout Detection
[0142] Multiple-tip devices were fabricated and applied for high
throughput analysis (FIG. 28A). The multiple-tip device was a set
of paper triangles all connected to a single copper strip (FIG.
28A). An electrode was connected to the copper strip. Multiple
samples were put on a single paper substrate and analyzed in series
using the multiple-tip probe (FIGS. 28B-C). Each tip was pre-loaded
with 0.2 uL methanol/water containing 100 ppm sample (cocaine or
caffeine) and dried. Then the whole multiple-tip device was moved
on a moving stage from left to right with constant velocity and 7
uL methanol/water was applied from the back part for each tip
during movement.
[0143] To prevent the contaminant during spray, blanks were
inserted between two sample tips. FIG. 28C shows the signal
intensity for the whole scanning. From total intensity, six tips
gave six individual high signal peaks. For cocaine, peaks only
appeared when tip 2 and tip 6 were scanned. For caffeine, the
highest peak came from tip 4, which was consistent with the sample
loading sequence.
Example 16
Tissue Analysis
[0144] Direct analysis of chemicals in animal tissue using probes
of the invention was performed as shown in FIG. 29A. A small
sections of tissue were removed and placed on a paper triangle.
Methanol/water (1:1 v:v; 10 .mu.l) was added to the paper as
solvent and then 4.5 kV positive DC voltage was applied to produce
the spray for MS analysis. Protonated hormone ions were observed
for porcine adrenal gland tissue (1 mm.sup.3, FIG. 29B). FIG. 16 is
a mass spectrum showing direct analysis of hormones in animal
tissue by paper spray. A small piece of pig adrenal gland tissue (1
mm.times.1 mm.times.1 mm) was placed onto the paper surface,
MeOH/water (1:1 v:v; 10 .mu.l) was added and a voltage applied to
the paper to produce a spray. The hormones epinephrine and
norepinephrine were identified in the spectrum; at high mass the
spectrum was dominated by phospholipid signals.
[0145] Lipid profiles were obtained for human prostate tissues (1
mm.sup.2.times.15 .mu.m, FIGS. 29C-D) removed from the tumor and
adjacent normal regions. Phospholipids such as phosphatidylcholine
(PC) and sphingomyelin (SM) were identified in the spectra. The
peak of [PC(34:1)+K].sup.+ at m/z 798 was significantly more
intense in tumor tissue (FIG. 29C) and peaks [SM(34:1)+Na].sup.+ at
m/z 725, [SM(36:0)+Na].sup.+ at m/z 756, and [SM(36:4)+Na].sup.+ at
m/z 804 were significantly lower compared with normal tissue (FIG.
29D).
Example 17
On-Line Derivatization
[0146] For analysis of target analytes which have relatively low
ionization efficiencies and relatively low concentrations in
mixtures, derivatization is often necessary to provide adequate
sensitivity. On-line derivatization can be implemented by adding
reagents into the spray solution, such as methanol/water solutions
containing reagents appropriate for targeted analytes. If the
reagents to be used are stable on paper, they can also be added
onto the porous materal when the probes are fabricated.
[0147] As a demonstration, 5 .mu.L methanol containing 500 ng
betaine aldehyde chloride was added onto a paper triangle and
allowed to dry to fabricate a sample substrate preloaded with a
derivatization reagent for the analysis of cholesterol in serum.
On-line charge labeling with betaine aldehyde (BA) through its
reaction with hydroxyl groups has been demonstrated previously to
be very effective for the identification of cholesterol in tissue
(Wu et al., Anal Chem. 2009, 81:7618-7624). When the paper triangle
was used for analysis, 2 .mu.L human serum was spotted onto the
paper to form a dried spot and then analyzed by using paper spray
ionization. A 10 .mu.L ACN/CHCl.sub.3 (1:1 v:v) solution, instead
of methanol/water, was used for paper spray to avoid reaction
between the betaine aldehyde and methanol.
[0148] The comparison between analysis using a blank and a
reagent-preloaded paper triangle is shown in FIGS. 30A-B. Without
the derivatization reagent, cholesterol-related peaks, such as
protonated ion [Chol+H].sup.+ (m/z 387), water loss
[Chol+H-H.sub.2O].sup.+ (m/z 369), and sodium adduction
[Chol+Na].sup.+ (m/z 409), were not observed (FIG. 30A). With the
derivatization reagent, the ion [Chol+BA].sup.+ was observed at m/z
488.6 (FIG. 30B). MS/MS analysis was performed for this ion and a
characteristic fragment ion m/z 369 was observed (FIG. 30C).
Example 18
Peptide Pre-Concentration Using Modified Paper Spray Substrate
[0149] Pre-concentration of chemicals on the paper surface using
photoresist treatment. Chromatography paper was rendered
hydrophobic by treatment with SU-8 photoresist as described
previously (Martinez et al., Angew Chem. Int. Ed., 2007,
46:1318-1320). Then 5 .mu.l bradykinin 2-9 solution (100 ppm in
pure H.sub.2O) was applied on the paper surface. When the solution
was dry, the paper was put into water and washed for 10 s. After
washing, the paper triangle was held in front of the MS inlet, 10
.mu.l pure MeOH was applied as solvent and the voltage was set at
4.5 kV for paper spray. The same experiment was done with untreated
paper substrate for comparison.
[0150] FIG. 31A shows the tandem MS spectrum of bradykinin 2-9 from
paper with photoresist treatment. The intensity of the most intense
fragment ion 404 is 5.66E3. FIG. 31B shows the tandem MS spectrum
of bradykinin 2-9 from normal chromatography paper without
photoresist treatment. The intensity of the most intense fragment
ion 404 is only 1.41E1. These data show that the binding affinity
between photoresist-treated chromatography paper and peptide is
much higher than that between normal chromatography paper and
peptide, thus more peptide can be kept on the paper surface after
washing by water. When pure methanol is applied, these retained
peptides will be desorbed and detected by MS. This method can be
used to pre-concentrate hydrophobic chemicals on the paper surface,
and other hydrophilic materials (e.g. salts) can also be removed
from the paper surface.
Example 19
Inverted Polarities
[0151] The polarity of the voltage applied to the probe need not
match that used in the mass analyzer. In particular, it is possible
to operate the probes of the invention with a negative potential
but to record the mass spectrum of the resulting positively changed
ions. In negative ion mode, a large current of electrons (or
solvated electrons) is produced in paper spray. These electrons, if
of suitable energy, can be captured by molecules with appropriate
electron affinities to generate radical anions.
[0152] Alternatively, these electrons might be responsible for
electron ionization of the analyte to generate the radical cation
or alternatively ESI might involve a solvent molecule which might
then undergo charge exchange with the analyte to again generate the
radical cation. If this process occurs with sufficient energy,
characteristic fragment ions might be produced provided the radical
cation is not collisionally deactivated before fragmentation can
occur.
[0153] An experiment was done on a benchtop LTP using toluene
vapor, with a probe of the invention conducted at -4.5 kV with
methanol:water as solvent applied to the paper. The spectrum shown
in FIG. 32 was recorded. One notes that ion/molecule reactions to
give the protonated molecule, m/z 93 occur as expected at
atmospheric pressure. One also notes however, the presence of the
radical cation, m/z 92 and its characteristic fragments at m/z 91
and 65.
[0154] An interesting note is that the "EI" fragment ions were most
easily produced when the source of toluene vapor was placed close
to the MS inlet; i.e., in the cathodic region of the discharge
between the paper tip and MS inlet. This suggests that direct
electron ionization by energetic electrons in the "fall" region
might be at least partly responsible for this behavior.
Example 20
Cartridge for Blood Analysis
[0155] FIG. 33A shows an exemplary case for spotting blood onto
porous material that will be used for mass spectral analysis. The
cartridge can have a vial with a volume at the center and vials for
overflows. A plug, such as a soluble membrane containing a set
amount of internal standard chemical, is used to block the bottom
of the vial for volume control. A drop of blood is placed in the
vial (FIG. 33B). The volume of the blood in the vial is controlled
by flowing the extra blood into the overflow vials (FIG. 33B). The
blood in the vial is subsequently dissolved in the membrane at the
bottom, mixing the internal standard chemical into the blood (FIG.
33B). Upon dissolution of the plug, blood flows to the paper
substrate, and eventually forms a dried blood spot having a
controlled amount of sample and internal standard (FIG. 33B).
Example 21
Microorganism Analysis and Identification
[0156] In certain aspects, probes of the invention can be used to
analyze one or more microorganisms (e.g., bacteria, viruses,
protozoans (also spelled protozoon), or fungi) in a sample. An
exemplary method involves contacting a sample including a
microorganism to a porous material, in which the porous material is
kept separate from a flow of solvent. The method further involves
applying high voltage to the porous material to generate ions of
the microorganism that are expelled from the porous material, and
analyzing the expelled ions, thereby analyzing the microorganism.
Methods of the invention may also involve applying a solvent to the
porous material. Any mass spectrometer known in the art may be
used, and in certain embodiments, the mass spectrometer is a
miniature mass spectrometer, such as that described for example in
Gao et al. (Anal. Chem., 80:7198-7205, 2008) and Hou et al. (Anal.
Chem., 83:1857-1861, 2011), the content of each of which is
incorporated herein by reference herein in its entirety.
[0157] The sample may be any type of sample and may be in any form,
for example, a solid, a liquid, or a gas. In certain embodiments,
the sample is a human tissue or body fluid. The sample may be an in
vivo sample or an extracted sample. In certain embodiments, the
methods of the invention are sensitive enough to analyze and
identify microorganisms without first culturing the microorganism.
In some embodiments, the microorganism is cultured prior to
analysis, however, methods of the invention allow for decreased
culture time over that used in standard procedures.
[0158] FIG. 37 shows an exemplary method of collecting
microorganisms onto probes of the invention when the sample is a
gas/aerosol. The figure shows a probe of the invention housed
within a cartridge. Such cartridges are described for example in
PCT/US12/40513, the content of which is incorporated by reference
herein in its entirety. Air is flowed through the cartridge, which
causes, under appropriate fluid flow conditions, any microorganisms
in the air to flow onto the substrate housed in the cartridge. Once
collected, voltage and a discrete amount of solvent is applied to
the probe, and ions of the microorganism are generated and expelled
into a mass spectrometer for analysis.
[0159] FIG. 38 shows an exemplary method of collecting
microorganisms onto probes of the invention when the sample is a
liquid. As shown in the figure, a porous substrate is loaded into
the funnel. A liquid sample containing bacteria poured into the
funnel and vacuum is used to pull the sample through the porous
substrate and into a collection vessel. As the sample passes
through the porous substrate, the microorganism is retained on the
porous substrate. Once collected, voltage and a discrete amount of
solvent is applied to the probe, and ions of the microorganism are
generated and expelled into a mass spectrometer for analysis. FIGS.
39A-B show mass spectra of E. coli generated using the set-up as
described in FIG. 38. FIG. 39A is negative ion mode and FIG. 39B is
positive ion mode.
[0160] If the sample is a solid, as in the case of a microorganism
grown on agar in a petri dish for example, the porous substrate can
be contacted to the solid and swapped or moved across the surface
such that microorganisms in the sample are retained by the porous
substrate. There are other methods for collecting microorganisms
from solid samples. For example, for colonies on petri dishes, a
sterile inoculation loop is used to transfer one or more colonies
to the porous substrate. Once collected, voltage and a discrete
amount of solvent is applied to the probe, and ions of the
microorganism are generated and expelled into a mass spectrometer
for analysis.
[0161] Regardless of the collection method, voltage, and optionally
a discrete amount of solvent, is applied to the probe, and ions of
the microorganism are generated and expelled into a mass
spectrometer for analysis. FIGS. 40-42 shows mass spectra of
microorganisms analyzed using probes and methods of the
invention.
[0162] Aspects of the invention also provide methods of identifying
an organism, e.g., a microorganism. The methods include obtaining a
mass spectrum of an organism using porous substrate probes of the
invention and correlating/comparing the mass spectra with a
database that includes mass spectra of known organisms (FIGS.
43-45A-F). With use of methods of the invention, the organism can
be identified and classified not just at a genus and species level,
but also at a sub-species (strain), a sub-strain, and/or an isolate
level. The featured methods offer fast, accurate, and detailed
information for identifying organisms. The methods can be used in a
clinical setting, e.g., a human or veterinary setting; or in an
environmental, industrial or forensic/public safety setting (e.g.,
clinical or industrial microbiology, food safety testing, ground
water testing, air testing, contamination testing, and the like).
In essence, the invention is useful in any setting in which the
detection and/or identification of a microorganism is necessary or
desirable.
[0163] A database for use in the invention can include a similarity
cluster. The database can be used to establish, through linear
discriminant analysis and related methods, a quantitative measure
of the similarity of any two spectra, a similarity index. The
database can include a mass spectrum from at least one member of
the Clade of the organism. The database can include a mass spectrum
from at least one subspecies of the organism. The database can
include a mass spectrum from a genus, a species, a strain, a
sub-strain, or an isolate of the organism. The database can include
a mass spectrum with motifs common to a genus, a species, a strain,
a sub-strain, or an isolate of the organism.
[0164] The database(s) used with the methods described herein
includes mass spectra associated with known organisms (FIGS.
45A-F). The mass spectra are typically annotated to show if they
were acquired in positive or negative mode. The database(s) can
contain information for a large number of isolates, e.g., about
200, about 300, about 400, about 500, about 600, about 700, about
800, about 900, about 1,000, about 1,500, about 2,000, about 3,000,
about 5,000, about 10,000 or more isolates. In addition, the mass
spectra of the database contain annotated information (a similarity
index or cluster, see FIGS. 43-44) regarding motifs common to
genus, species, sub-species (strain), sub-strain, and/or isolates
for various organisms. The large number of the isolates and the
information regarding specific motifs allows for accurate and rapid
identification of an organism. The data in FIG. 43 show that there
is separation of fungi and bacteria, a separation between gram
negative and gram positive bacteria, and a separation of gram
negative species.
[0165] To generate similarity clusters, each mass spectrum is
aligned against every other mass spectrum. From these alignments, a
pair-wise alignment analysis is performed to determine "percent
dissimilarity" between the members of the pair (FIG. 44). Briefly,
this clustering method works by initially placing each entry in its
own cluster, then iteratively joining the two nearest clusters,
where the distance between two clusters is the smallest
dissimilarity between a point in one cluster and a point in the
other cluster.
[0166] Various organisms, e.g., viruses, and various
microorganisms, e.g., bacteria, protists, and fungi, can be
identified with the methods featured herein. The sample containing
the organism to be identified can be a human sample, e.g., a tissue
sample, e.g., epithelial (e.g., skin), connective (e.g., blood and
bone), muscle, and nervous tissue, or a secretion sample, e.g.,
saliva, urine, tears, and feces sample. The sample can also be a
non-human sample, e.g., a horse, camel, llama, cow, sheep, goat,
pig, dog, cat, weasel, rodent, bird, reptile, and insect sample.
The sample can also be from a plant, water source, food, air, soil,
plants, or other environmental or industrial sources.
[0167] The methods described herein include correlating the mass
spectrum from the unknown organism with a database that includes
mass spectra of known organisms. The methods involve comparing each
of the mass spectra from the unknown organism from a sample against
each of the entries in the database, and then combining match
probabilities across different spectra to create an overall match
probability (FIGS. 45A-F).
Sequence CWU 1
1
1110PRTHomo sapiens 1Asp Arg Val Tyr Ile His Pro Phe His Leu 1 5
10
* * * * *