U.S. patent application number 10/536230 was filed with the patent office on 2006-06-22 for particles.
Invention is credited to Erling Sigurd Finne, Geir Fonnum, Grete Irene Modahl, Astrid Evenrod Molteberg, Torkel Stene, Ellen Weng.
Application Number | 20060131542 10/536230 |
Document ID | / |
Family ID | 9949513 |
Filed Date | 2006-06-22 |
United States Patent
Application |
20060131542 |
Kind Code |
A1 |
Weng; Ellen ; et
al. |
June 22, 2006 |
Particles
Abstract
A coated magnetic particle comprising an optionally porous
magnetic polymer particle of a matrix polymer, said polymer
particle having on a surface and/or in the pores thereof
superparamagnetic crystals, said coated particle having a coat
formed of a coating polymer, wherein said coated magnetic particle
is essentially non-autofluorescent.
Inventors: |
Weng; Ellen; (Oppegard,
NO) ; Fonnum; Geir; (Fjellhamar, NO) ; Modahl;
Grete Irene; (Arnes, NO) ; Molteberg; Astrid
Evenrod; (Fetsund, NO) ; Finne; Erling Sigurd;
(Avalstad, NO) ; Stene; Torkel; (Oslo,
NO) |
Correspondence
Address: |
NEEDLE & ROSENBERG, P.C.
SUITE 1000
999 PEACHTREE STREET
ATLANTA
GA
30309-3915
US
|
Family ID: |
9949513 |
Appl. No.: |
10/536230 |
Filed: |
December 11, 2003 |
PCT Filed: |
December 11, 2003 |
PCT NO: |
PCT/GB03/05390 |
371 Date: |
October 20, 2005 |
Current U.S.
Class: |
252/301.16 ;
252/62.51R; 252/62.54; 427/127; 427/212 |
Current CPC
Class: |
G01N 33/5434 20130101;
C09K 11/025 20130101; H01F 1/26 20130101; B82Y 25/00 20130101; H01F
1/0018 20130101; H01F 1/01 20130101; B82Y 40/00 20130101; Y10T
428/2998 20150115; H01F 41/00 20130101; C08F 220/18 20130101; C09K
11/06 20130101; Y10T 428/2991 20150115 |
Class at
Publication: |
252/301.16 ;
427/212; 427/127; 252/062.51R; 252/062.54 |
International
Class: |
H01F 1/00 20060101
H01F001/00; C09K 11/06 20060101 C09K011/06 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 11, 2002 |
GB |
0228914.8 |
Claims
1. A coated magnetic particle comprising an optionally porous
magnetic polymer particle of a matrix polymer, said polymer
particle having on a surface and/or in the pores thereof
superparamagnetic crystals, said coated particle having a
coefficient of variation (CV) of less than 10% and having a coat
formed of a coating polymer, wherein said coated magnetic particle
is essentially non-autofluorescent.
2. A coated magnetic particle as claimed in claim 1 having a level
of autofluorescence corresponding to a difference in the Mean Grey
Value (.DELTA.MGV) at an excitation wavelength of 450.+-.25 nm for
an exposure time of 500 ms or 600 ms of less than 600.
3. A coated magnetic particle as claimed in claim 2 having a level
of autofluorescence corresponding to a difference in the Mean Grey
Value (.DELTA.MGV) at an excitation wavelength of 450.+-.25 nm for
an exposure time of 500 ms or 600 ms of less than 300.
4. A coated magnetic particle as claimed in claim 1 being
essentially free of conjugated delocalized electron systems (except
those within benzene rings).
5. A coated magnetic particle as claimed in claim 1 wherein said
coating polymer is formed from at least one epoxide.
6. A coated magnetic particle as claimed in claim 5 wherein said
coating polymer is formed from at least two epoxides.
7. A coated magnetic particle as claimed in claim 6 wherein the
epoxides are selected from epichlorohydrin, epibromohydrin,
isopropylglycidyl ether, butyl glycidyl ether, allylglycidyl ether,
1,4-butanediol diglycidyl ether (1,4-bis (2,3-epoxypropoxy)
butane), ethylhexylglycidylether, methyl glycidylether
neopentylglycol diglycidyl ether, ethylene glycol diglycidyl ether,
glycerol diglycidyl ether, glycidol, and glycidyl methacrylate.
8. A coated magnetic particle as claimed in claim 1 wherein the
polymer particle is porous.
9. A coated magnetic particle as claimed in claim 1 wherein the
polymer particle has a diameter in the range 0.8 to 10 .mu.m.
10. A coated magnetic particle as claimed in claim 9 wherein the
particle is in the range 2 to 10 .mu.m in diameter.
11. A coated magnetic particle as claimed in claim 1 wherein said
matrix polymer is a combination of a styrenic polymer, a
styrenic/acrylic polymer and an acrylic polymer.
12. A coated magnetic particle as claimed in claim 1 wherein the
particle surface carries free amino groups.
13. A coated magnetic particle as claimed in claim 1 additionally
comprising a fluorophore or mixture of different fluorophores.
14. A coated magnetic particle as claimed in claim 13 wherein said
fluorophore is attached to the external coating polymer via an
amino linkage or is swollen into the coating polymer and entrapped
therein.
15. A coated magnetic particle as claimed in claim 13 wherein said
fluorophore is Bodipy 630/650, Bodipy 650/655, DY-647 or
AMCA-X.
16. A coated magnetic particle as claimed in claim 13 wherein said
fluorophore emits in the blue/green region of the electromagnetic
spectrum.
17. A coated magnetic particle as claimed in claim 1 additionally
comprising an affinity ligand.
18. A mixture of coated magnetic particle as claimed in claim 1
wherein the CV of the polymer particle diameters is less than
8%.
19. A mixture of coated magnetic particles as claimed in claim 1
comprising at least a first set of coated magnetic particles
carrying a first fluorophore and second set of coated magnetic
particles carrying a second fluorophore, the particles of said
first and second sets being of differing diameters.
20. A process for the preparation of coated magnetic particles as
claimed in claim 1 being free of conjugated delocalised electron
systems, said method comprising reacting porous magnetic polymer
particles essentially free from surface nitro groups and having
superparamagnetic crystals on the surface and/or in the pores
thereof with polymer-forming monomers selected from epoxides.
21. Use of a coated magnetic particle or particles as claimed in
claim 1 in an assay.
22. Use as claimed in claim 21 wherein said assay comprises the
steps of: i) adding a coated magnetic particle comprising a first
fluorophore and an affinity ligand to a sample in which a target
analyte may be present; ii) allowing said affinity ligand to bind
with said analyte if present to form a complex; iii) contacting the
complex with a reporter to allow binding of said reporter to said
analyte wherein said reporter optionally carries a second
fluorophore; iv) magnetically separating said particles from said
sample; and v) detecting said first fluorophore and if present said
second fluorophore.
23. Use as claimed in claim 22 wherein detection is carried out
using a flow cytometer or by microscopy.
24. Use as claimed in claim 22 wherein the particles form part of a
bead array, which is analysed to detect the position of each bead
type and the presence of second fluorophore.
25. Use as claimed in claim 22 wherein said reporter is biotin or a
second fluorophore which is different from said first
fluorophore.
26. Use as claimed in claim 21 wherein step (i) additionally
comprises the step of: adding at least a second coated magnetic
particle carrying a further affinity ligand (specific for other
analytes which may be present in the sample) and a further
fluorophore to said sample, said first and further affinity ligands
and said first and further fluorophores being different.
27. Use as claimed in claim 26 wherein said second coated magnetic
particle is of different diameter to said first coated magnetic
particle.
28. Use as claimed in claim 22 wherein said reporter is biotin and
said complexes are contacted with a streptavidin coated surface
prior to fluorophore detection.
29. Use as claimed in claim 21 wherein said assay comprises the
steps of: i) contacting a coated magnetic particle comprising a
first fluorophore and an affinity ligand with a sample in which a
target analyte may be present and in which an analyte carrying a
reporter capable of competing with said target analyte for the
affinity ligand is present: ii) allowing said affinity ligand to
bind to said analyte, if present, or said analyte carrying a
reporter; iii) magnetically separating said particles from said
sample; and iv) detecting the first fluorophore.
30. Use as claimed in claim 29 wherein said reporter is biotin and
said complexes are contacted with a streptavidin coated surface
prior to fluorophore detection.
31. An optionally porous magnetic polymer particle comprising a
matrix polymer, with disposed on the surface and/or in the pores
thereof superparamagnetic crystals, said matrix polymer being
essentially free of conjugated delocalized electron systems and
optionally being surface functionalised with groups selected from
sulphonic acid, carboxylic acid, amine, and epoxy groups, said
particle being essentially non-autofluorescent.
Description
[0001] This invention relates to magnetic polymer particles, to
processes for their preparation and to their uses. In particular,
the invention relates to coated magnetic polymer particles which
exhibit low autofluorescence.
[0002] Magnetic polymer particles are of general utility in various
medical and biochemical fields, for example as transport vehicles
for the delivery of pharmaceutical products, for diagnostic
purposes, for separation and for synthetic purposes. Such particles
rely upon their magnetic properties in order to perform these
functions: in diagnostic assay applications, for example,
application of a magnetic field to a sample containing an analyte
bound to magnetic polymer particles allows the isolation of the
analyte without the use of centrifugation or filtration; and in
therapeutic applications, for example, application of a magnetic
field to the patient may serve to target drug-carrying magnetic
polymer particles to a desired body site.
[0003] By magnetic is meant herein that the polymer particles
contain superparamagnetic crystals. Thus the magnetic polymer
particles are magnetically displaceable but are not permanently
magnetizable.
[0004] Many processes for preparing magnetic polymer particles are
known, a large number of which involve preparing maghemite- or
magnetite containing polymer particles from pre-formed magnetic
iron oxides, e.g. magnetite. Some of processes involved are
described in U.S. Pat. No. 4,654,267 (Ugelstad) the contents of
which are incorporated herein by reference.
[0005] Thus U.S. Pat. No. 4,654,267 outlines a number of
limitations with regard to the processes which preceded it; these
include difficulty in obtaining magnetic particles of similar size
and/or of homogeneous or uniform magnetic properties, as well as a
more general problem relating to the difficulty of incorporating
magnetic material inside the cavities of porous polymer
particles.
[0006] With deposition taking place principally on the surface, or
in large open cavities, leaching of magnetic particles, which
shortens the useful lifetime of magnetic polymer particles in the
applications to which they are put, was consequently
problematic.
[0007] In order to overcome these disadvantages, to produce porous
magnetic polymer particles having magnetic material disposed within
the polymer pores, U.S. Pat. No. 4,654,267 advocated the use of
porous polymer particles having surface functional groups which
serve to draw the iron ions into the polymer particles. These
functional groups could either result from the use of
functionalized comonomers in the production of the polymer or from
post-polymerization treatment of the polymer to introduce the
functional groups, e.g. by coupling to or transformation of
existing groups on the polymer surface.
[0008] The leaching of superparamagnetic crystals from the porous
polymer particles may be further inhibited by forming a further
polymer coating over the superparamagnetic crystal loaded polymer
particles, or more particularly by at least partly filling the
pores of the particles with a polymer coating. Such coating
polymers may typically be formed from monomers reactive with
functional groups pendant from the surface of the polymer of the
underlying particles.
[0009] However, when coated magnetic polymer particles are prepared
in this way they exhibit the characteristic known as
autofluorescence, i.e. they exhibit intrinsic fluorescence. While
for many of the uses of coated magnetic polymer particles, e.g.
where they are used in syntheses or separations, autofluorescence
does not cause problems, where the particles are to be used in
assays in which light emissions are detected, autofluorescence by
the particles can produce unwanted background signals. The
autofluorsecence may also mask the signal from an emitter of
interest. This will decrease the sensitivity of the assay.
[0010] We have now surprisingly found that the autofluorescence
exhibited by a magnetic polymer particle can be minimised by the
avoidance of conjugated delocalised electron systems (other than
those found in benzene rings) in the matrix polymer, in the
particle coating and in any surface functionalities. Such
conjugated delocalised electron systems had previously been
considered essential to allow attraction of iron oxides in the
magnetisation step and polymer coating to occur successfully.
[0011] As a result, a matrix polymer with reduced or no tendency to
autofluorescence can be used in the preparation of coated magnetic
polymer particles which therefore exhibit remarkably low
autofluorescence. Such particles may have utility in a variety of
assays, in particular assays in which fluorescence is detected.
[0012] Whilst the use of fluorescent entities as labels in
non-magnetic polymer beads is known, the use of such fluorescent
labels in magnetic beads has the advantage of enabling the
combination of magnetic sample preparation and detection, i.e.
combining instrumentation for automated sample preparation and/or
concentration with detection platforms such as flow cytometers,
fluorescence microscopes, high resolution array scanners or laser
scanning cytometers. These detection devices can all be included in
microfluidic devices where the possibility of using the magnetic
properties for sample preparation and/or concentration will be
important.
[0013] Thus viewed from one aspect the invention provides an
optionally porous magnetic polymer particle comprising a matrix
polymer, with disposed on the surface and/or in the pores thereof
superparamagnetic crystals, said matrix polymer preferably being
essentially free of conjugated delocalized electron systems and
optionally being surface functionalised with groups selected from
sulphonic acid, carboxylic acid, amine, and epoxy groups, said
particle being essentially non-autofluorescent, e.g. having a level
of autofluorescence corresponding to a difference in the Mean Grey
Value (.DELTA.MGV) at an excitation wavelength of 450.+-.25 nm for
an exposure time of 500 ms or 600 ms of less than 600.
[0014] Viewed from another aspect the invention provides a coated
magnetic particle comprising an optionally porous magnetic polymer
particle of a matrix polymer, said polymer particle having on a
surface and/or in the pores thereof superparamagnetic crystals,
said coated particle having a coat formed of a coating polymer,
wherein said coated magnetic particle is essentially
non-autofluorescent, e.g. has a level of autofluorescence
corresponding to a difference in the Mean Grey Value (.DELTA.MGV)
at an excitation wavelength of 450.+-.25 nm for an exposure time of
500 ms or 600 ms of less than 600 and said coated particle is
preferably essentially free of conjugated delocalized electron
systems.
[0015] By matrix polymer (or polymers) is meant the polymer (or
polymers) and, if required, cross-linking agents employed to form
the uncoated polymer particle, as further defined in detail
below.
[0016] By essentially free of conjugated delocalized electron
systems is meant that the matrix polymer and if present said
coating polymer (i.e. the coated particle itself) do not contain
any electronic systems in which delocalisation occurs (other than
within a benzene ring).
[0017] The uncoated magnetic polymer particles produced by forming
superparamagnetic crystals in the pores of porous matrix polymers,
optionally surface functionalized e.g. with sulphonic acid,
carboxylic acid, amine, or epoxy groups (but not with nitro
groups), should be effectively non-autofluorescent. Such uncoated
particles (and hence the coated particles) preferably have
.DELTA.MGV values of less than 300, especially less than 200,
particularly less than 100. Such uncoated particles may be used as
intermediates in the preparation of the coated particles of the
invention or in end uses where leaching of the superparamagnetic
crystals is not problematic.
[0018] The .DELTA.MGV for the uncoated and coated particles is more
preferably less than 400, particularly below 350, more particularly
below 300.
[0019] The .DELTA.MGV for the particles is determined using a
fluorescence microscope by illumination of a substrate (e.g. glass)
surface carrying the particles with light from a 100 W mercury or
75 W xenon lamp filtered through a 450.+-.25 nm excitation band
pass filter, with a beam splitter at 480 nm and with the emitted
light being filtered through a 520 nm long pass filter. .DELTA.MGV
is the difference in the Mean Grey Value determined for a minimum
of 30 particles and the Mean Grey Value determined for a similar
minimum of background positions (i.e. positions on the substrate)
e.g. 25 positions.
[0020] Conveniently .DELTA.MGV can be determined using a BX-61
fluorescence microscope from Olympus equipped with a 100 W mercury
or 75 W xenon lamp and excitation and emission filters from Chroma
Technology and an Uplan-Apo 20.times. objective. Emission detection
can be effected using an F-view digital monochrome CCD camera (4096
grey levels) for an exposure time of 500 ms (Xenon lamp) or 600 ms
(mercury lamp) and image analysis to determine the MGV values may
be performed using the Analysis software of Soft Imaging
Systems.
[0021] For autofluorescence determination the particles are either
dispersed between parallel glass substrates (e.g. microscope
slides) in a liquid medium, e.g. 1:1 by volume mixture of glycerol
and 1.5 g/l sodium dodecyl sulphate in water (as in Example 12) or
buffered in pH 7.4 phosphate buffer saline (Example 18).
Autofluorescence measurement is explained in detail in examples 12
and 18.
[0022] The superparamagnetic crystals in the polymer particles used
in the particles of the invention may be of any material capable of
being deposited in superparamagnetic crystalline form on the
surface of a polymer particle or more preferably in the pores of a
porous polymer particle. Thus the superparamagnetic crystals in the
particles of the invention may be of any element, alloy or compound
capable of exhibiting superparamagnetism. Magnetic iron oxides,
e.g. magnetite or maghemite are preferred; however the crystals may
be of mixed metal oxides or other magnetic material if desired. The
total quantity of crystalline magnetic material present is
generally more than 1%, preferably more than 3%, desirably more
than or equal to 5% (by weight, e.g. up to 40% wt. The percentage
is calculated on a Fe (or equivalent metal in the case of magnetic
materials other than iron oxides) weight basis based upon the
overall dry weight of the coated particles. The superparamagnetic
crystals will be on a surface of the matrix polymer, i.e. on the
external surface of the particle or, more preferably, on a surface
of a pore in a porous matrix particle.
[0023] The optionally porous magnetic polymer particle may be
prepared by conventional means using monomers. In general any
porous non-autofluorescent polymer particles can be used. However,
the monomers used in forming the matrix polymer (and the coating
polymer) should preferably be such that the resultant polymer is
substantially free from conjugated delocalized electron systems
other than benzene rings. Thus for example the use of
divinylbenzene as a cross-linking agent should preferably be
avoided.
[0024] Also the presence of nitro groups on the surface of the
polymer particle should be avoided since such groups inherently
contain delocalised electron systems and therefore contribute to
the autofluorescence of the polymer particle.
[0025] The matrix polymer is especially preferably vinylic, a
styrenic or, especially, an acrylic polymer. Preferred monomers for
matrix polymer preparation include methyl methacrylate, methacrylic
acid, hydroxyethyl methacrylate, glycidyl methacrylate,
butylmethacrylate, acrylic acid, ethyleneglycol dimethacrylate,
trimethylolpropane trimethacrylate, trimethylol triacrylate,
pentaerythritol tetraacrylate and other acrylic or methacrylic
monomers.
[0026] The matrix polymer is preferably not water-swellable.
[0027] In one preferred embodiment of the invention, the matrix
polymer may be produced by a seeded polymerization reaction, i.e. a
multistage polymerization in which the particulate polymer from one
stage is used as a seed for a subsequent polymerization reaction in
which a larger dimension particulate is produced. In this
embodiment, the monomers used in one stage need not be the same as
those used in the other stage(s). In this embodiment, the polymer
produced in the final stage is preferably an acrylic polymer. The
polymer produced in the initial polymerization stage is preferably
a styrenic polymer. In an especially preferred embodiment the
initial polymer (the seed) is styrenic, an intermediate polymer is
a styrenic/acrylic copolymer, and the final polymer is acrylic.
[0028] The matrix polymer containing particles may be prepared by
any technique suitable for producing particulate polymer particles,
e.g. suspension polymerization, emulsion polymerization, dispersion
polymerisation etc. However, the particles are especially
preferably produced using the well known Ugelstad process, e.g. as
described in U.S. Pat. No. 4,654,267 or WO00/61647. Preferably
however, ammonia is employed in the magnetisation process instead
of ethylene diamine. The use of ammonia has been surprisingly found
to give rise to particles having lower levels of
autofluorescence.
[0029] Thus, prior to incorporation of the magnetic particles it is
possible to introduce amino groups onto the particle surface using
ammonia.
[0030] Particles may be produced using the Ugelstad process which
are substantially monodisperse, i.e. the coefficient of variation
(CV) of the particle diameter is very small, e.g. 2 to 5%. CV is
defined as 100 times (standard deviation) divided by mean where
mean is mean particle diameter and standard deviation is standard
deviation in particle size. CV is preferably calculated on the main
mode, ie. by fitting a monomodal distribution curve to the detected
particle size distribution. Thus some particles below or above mode
size may be discounted in the calculation which may for example be
based on about 90% of total particle number (of detectable
particles that is). Such a determination of CV is performable on a
Coulter LS 130 particle size analyzer.
[0031] The coating polymer is preferably formed from at least one
epoxide compound, preferably at least two epoxide compounds.
[0032] The reaction of the porous magnetic polymer particle with
the coating monomers generates a coating polymer within the pores
of the matrix polymer particles which serves essentially to block
these pores, physically encapsulating the superparamagnetic
crystals within the polymer particles. The resulting "coated"
particles then have reduced porosity relative to the porous
starting material. Surprisingly it is believed that the
superparamagnetic crystals appear to catalyse the polymerization so
that the coating forms preferentially in their vicinity. Since the
majority of the superparamagnetic crystals are within pores in the
starting porous particles, the coating may not form to any
significant extent on the external surface of the particles.
[0033] In one preferred embodiment, the porous polymer particles
are reacted with a mixture of epoxides. Preferably, the epoxides
contain at least one ether link and optionally a hydrophobic
component, e.g. a alkylene chain. Generally the epoxides will have
a carbon atom content of from 3 to 50, preferably 3 to 25. Typical
epoxides that may be used include epichlorohydrin, epibromohydrin,
isopropylglycidyl ether, butyl glycidyl ether, allylglycidyl ether,
1,4-butanediol diglycidyl ether (1,4-bis (2,3-epoxypropoxy)butane),
neopentylglycol diglycidyl ether, ethylene glycol diglycidyl ether,
glycerol diglycidyl ether, glycidol, and glycidyl methacrylate,
ethyl hexyl glycidylether, methyl glycidylether, glycerol
propoxylate triglycidylether, poly(propylene glycol)
diclycidylether, 1,3 butanediol diglycidylether, tert-butyl
glycidylether, 1,4 cyclohexanedimethanol diglycidyl ether,
diethylene glycol diglycidyl ether, dodecyl glycidylether, O-(2,3
epoxypropyl)-O'-methylpolyethylene glycol glydidylether, glycidyl
tetrafluoroethyl ether, 1,6 hexanediol diglycidylether, octyl
glycidylether, decyl glycidylether,
poly(epichlorohydrin-co-ethylene oxide-co-allyl glycidylether),
polyethylene glycol diglycidyl ether, trimethylolethane
triglycidylether, trimethylolpropan, triglycidylether,
tert-butyldimehytlsilyl glycidylether, 1,2-epoxybutane,
1,2-epoxypentane, 1,2-epoxy-5-hexene, 1,2-epoxy-hexane,
1,2-epoxy-7-octene, 1,2-epoxyoctane, 1,2,7,8-Diepoxyoctane,
1,2-Epoxy-9-decene, 1,2-Epoxydecane, 1,2-Epoxydodecane,
1,2-Epoxytetradecane etc.
[0034] Typically, the coating reaction may be effected by
impregnating the porous magnetic polymer particle with the coating
monomers e.g. using a solution of these (for example in an organic
solvent such as methanol, toluene, xylene, diethylenglycol,
dimethyl ether or diglyme) or by mixing a dispersion of the porous
particles in an organic solvent with a liquid epoxide mixture.
Sonication may be used to improve impregnation and the reaction may
be accelerated by raising the temperature, e.g. to 50-100.degree.
C. Any solvent used may be extracted by application of sub-ambient
pressure.
[0035] Viewed from a further aspect the invention provides a
process for the preparation of coated magnetic particles as herein
before described being free of conjugated delocalised electron
systems, said method comprising reacting porous magnetic polymer
particles essentially free from surface nitro groups and having
superparamagnetic crystals on the surface and/or in the pores
thereof with polymer-forming monomers selected from epoxides.
[0036] Viewed from a further aspect the invention provides the use
of such particles in syntheses, extractions or assays.
[0037] If desired further materials may be impregnated into or
chemically attached to the particles either before the coating
polymerization reaction or after coating polymerization. Typically
such further materials will be radiation emitters or absorbers,
e.g. fluorophores, material giving luminescence, material giving
time delayed fluorescence, chromophores or radioactively labelled
materials.
[0038] Particles according to the present invention will generally
have sizes (i.e. diameters) that are generally in the micrometer
range, e.g. 0.3 to 100 .mu.m, especially 0.5 to 50 .mu.m, more
especially 0.8 to 10 .mu.m, e.g. 2 to 10 .mu.m, e.g. 5 and 8
.mu.m.
[0039] Typically the porous particles used will have a surface area
of at least 15 m.sup.2/g (measured by the BET nitrogen absorption
method), and more preferably at least 30 m.sup.2/g, e.g. up to 700
m.sup.2/g, when corrected to a mean particle diameter of 2.7 .mu.m
(i.e. multiply surface 5 area by 2.7/MD, where MD is the mean
diameter in micrometers). Similarly scaled, the particle pore
volume is preferably at least 0.1 mL/g.
[0040] Typically, the polymer particles are spherical and
substantially monodisperse before they are coated and especially
preferably remain spherical and substantially monodisperse once
they have been coated.
[0041] By substantially monodisperse it is meant that for a
plurality of particles (e.g. at least 100, more preferably at least
1000) the particles have a coefficient of variation (CV) of less
than 20%, for example less than 15%, preferably less than 12%, more
preferably less than 11%, still more preferably less than 10% and
most preferably no more than about 8, e.g. 2 to 5%.
[0042] Generally, the uses to which magnetic polymer particles are
put, e.g. their use as diagnostic tools, require an appropriate
degree of electrophilicity in order that they may participate
adequately in coupling and other reactions in aqueous systems
prevalent in biological media.
[0043] Whilst the general polarity of the coatings is desirably
electrophilic, certain coatings which contain hydrophobic moieties
may be incorporated so as to tailor the degree of electrophilicity
to that which is desired. In this way, the invention permits the
provision of useful diagnostic and other tools having a wide range
of polarities.
[0044] If desired the surfaces of the coated magnetic polymer
particles may be further functionalised, e.g. by coupling a drug
molecule, a reporter label (e.g. a chromophore, enzyme or
radiolabel), or an affinity ligand (e.g. an antibody or antibody
fragment, a member of a specific binding partner pair (e.g. biotin
or streptavidin), an oligopeptide, an oligonucleotide, or an
oligosaccharide).
[0045] Such coupling may be direct or indirect (and so may or may
not involve the use of a coupling agent to form a linkage between
the particle and the substance being coupled to it) and may be
biodegradable or non-biodegradable. Biodegradable couplings may be
desired if the magnetic polymer particles are to be used for the
targeted release of an active compound. Accordingly after coating
has been effected, the pendant groups of the coating may be
manipulated to provide appropriate functionality (for example
epoxy, hydroxy, amino, ketones, mercapto, isothiocyanate,
isocyanate, tosyl, carboxylic acid etc functionalities) for the
attachment of such substances.
[0046] The low autofluorescence particles of the invention are of
particular use in applications where the fluorescence of the
particle is to be detected, e.g. in an assay where a reporter
carries a fluorophore. By fluorophore is meant a compound which
exhibits intrinsic fluorescence. In some assays it may be
preferable to employ coloured particles or beads. In this regard,
coloured particles/beads for use in such assays require the
presence of a fluorophore to "colour code" the particle. Many
different fluorophores are known allowing the preparation of a
variety of colour coded beads, (i.e. each bead class emitting light
at distinct wavelengths, different intensity etc when excited by
light of a lower wavelength. The excitation source can be laser(s)
or filtered light of one or several wavelengths). Such coding may
be constructed by, for example, providing beads of differing
fluorescence intensity, with differing fluorescence spectra,
differing intensity-ratio between two or more fluorophores, or by
using beads of differing diameters with various fluorophores. Other
possible coding methods may be use of magnetic tags, refractive
index, adsorption spectrums, adsorption ratios etc.
[0047] Fluorophores can be attached to the low autofluorescence
particles of the invention by, for example, contacting a particle
having surface functional groups, e.g. amino groups, with a
fluorophore comprising a reactive group forming covalent attachment
of the fluorophore to the particles. Such functional groups may be
succinimidyl esters, isothiocyanates, carboxylic acids, maleimides,
sulphonyl chlorides etc.
[0048] Other potential methods for incorporation of fluorophores
onto (or into) the beads may involve hydrophobic or electrostatic
interactions, swelling of the fluorophores into the coating and
entrapment (or capture) of the fluorophores in the coating
(entrapment may be induced by change of polarity of the solvents
used), deposition of fluorophores in pores, swelling fluorophores
into polymer matrix etc.
[0049] The attachment of the fluorophore to the particle can be
achieved at any suitable stage of the particle synthesis. Thus, a
fluorophore may be attached to the particle after the magnetisation
process but before a coat is subsequently applied. Alternatively, a
thin coat may be applied to the particle prior to the fluorophore
being added and a subsequent further coat applied. Most
conveniently however, the fluorophore is attached to the particle
after the final coat has been applied.
[0050] The latter process is most favoured since the application of
a coat over the fluorophore may significantly reduce its
fluorescent intensity although for the coumarin dye AMCA (from
Molecular Probes Inc.) intensity reduction is not observed if a
coating is placed over it.
[0051] The reaction between the particle and the fluorophore should
conveniently take place in an organic solvent such as
dimethylformamide, acetonitrile, acetone, 1,4-dioxane, chloroform,
methanol, ethanol, toluene, butylacetate, ethylacetate etc alone or
mixtures thereof; what is primarily required is a solvent system
which allows a homogenous distribution of dye to all the particles
and allows incorporation of dye in high yield. This will be readily
carried out by the person skilled in the art.
[0052] The fluorophore functionalised coated magnetic particle
should also carry an affinity ligand, the nature of which will be
selected based on its affinity for a particular analyte whose
presence or absence in a sample is to be ascertained. The affinity
ligand may therefore comprise any molecule capable of being linked
to a magnetic probe which is also capable of specific recognition
of a particular analyte. Affinity ligands therefore include
monoclonal antibodies, polyclonal antibodies, antibody fragments,
nucleic acids, oligonucleotides, proteins, oligopeptides,
polysaccharides, sugars, peptides, peptide encoding nucleic acid
molecules, antigens, drugs and other ligands. Most commonly the
affinity ligand is an antibody which binds to an antigen in a
sample. Examples of suitable affinity ligands are available in the
published literature and are well known. The use of further binding
partners, secondary affinity ligands and linking groups is routine
in the art and it will be appreciated that the use of such species
with the particles of the invention is possible if desired.
[0053] More specifically, nucleic acid detection generally involves
probing a sample thought to contain target nucleic acids using a
nucleic acid probe that contains a nucleic acid sequence that
specifically recognises, e.g. hybridises with, the sequence of the
target nucleic acids, such that the nucleic acid affinity ligand
and the target nucleic acids in combination create a hybridisation
layer. Correspondingly, immunoassay type detection of hormones,
antibodies, cytokines etc generally involves binding of an antibody
or an antigen to the beads. It may also be of interest to bind
ligands that have specific affinity for "tags" which have been
introduced on the target of interest. Such ligands can be a metal
chelate, small organic molecule, nucleic acid derivative or
protein. For applications in cellular biology and microbiology it
will be of interest to bind antibodies with affinity for special
cell types, bacteria or viruses.
[0054] The target material is optionally a biological molecule or
molecule of synthetic origin, or conjugation of the two types, e.g.
it may be a molecule or a group of molecules, cells or a single
cell organism or a virus including for example antibodies, amino
acids, proteins, peptides, polypeptides, enzymes, enzyme
substrates, hormones, lymphokines, metabolites, antigens, haptens,
cytokines, lectins, avidin, streptavidin, toxins, poisons,
environmental pollutants, carbohydrates, oligosaccharides,
polysaccharides, glycoproteins, glycolipids, nucleotides,
oligonucleotides, nucleic acids and derivatised nucleic acids, DNA,
RNA, natural or synthetic drugs, receptors, virus particles,
bacterial particles virus components, cells, cellular components,
natural or synthetic lipid vesicles, polymer membranes, polymer
services and particles and glass and plastic surfaces.
[0055] As well as being coupled to such target-binding ligands, the
particles produced according to the invention may also be
subsequently labelled with a reporter moiety, e.g. biotin, a
chromophore, fluorophore, radioisotope or enzyme.
[0056] Of particular further interest is the possibility of
including a fluorophore as a reporter moiety especially in
conjunction with a colour coded particle as described above. The
incorporation of a fluorophore into a reporter molecule is known in
the art.
[0057] For example, in nucleic acid detection, an oligonucleotide
probe complementary to the target, labelled with one or several
fluorophores can be employed. Labelling may be achieved by e.g.
using modified phosphoramidites during probe synthesis.
[0058] Alternatively, enzymatic incorporation of labelled
nucleotdies or probes can be employed when the target is
present.
[0059] For protein/immunoassays, an antibody or antigen can be
labelled using standard cross-linking reagents; e.g.
N-hydroxysuccinimide activated fluorophores which react with amino
groups on the protein or antigen.
[0060] When such a reporter is combined with a low autofluorescence
particle of the invention already attached to a "colour coding"
fluorophore the presence of two excitable fluorophores exists. This
allows the beads to be utilised in a variety of assays as described
in more detail below and allows multiplexing.
[0061] The fluorophores utilised should be chosen such that their
excitation and emission signals do not interfere. Whilst the person
skilled in the art can tailor the fluorophores they use to minimise
overlap, because many fluorophores have a absorption spectrum which
exhibit a tail at wavelengths shorter than the absorption maximum
and further to avoid excitation of the code with the excitation
light intended for the reporter, preferably the code (i.e. particle
fluorophore) should be set at shorter wavelengths than the
reporter. Moreover, the shorter wavelength region (blue and green
emission) is also the region of the spectrum where inherent
autofluorescence is most significant.
[0062] In a particularly preferred embodiment of the invention
therefore, the fluorophore attached to the particle will emit in
the blue region of the spectrum (i.e. at shorter wavelengths that
the reporter) whereas the fluorophore attached to the reporter
moiety will emit in the red region of the spectrum (i.e. at longer
wavelengths than the particle fluorophore).
[0063] Alternatively viewed, the colour fluorophore (code) attached
to the particle will emit at shorter wavelengths than the reporter
whereas the fluorophore attached to the reporter moiety will emit
at longer wavelengths than the code.
[0064] Suitable fluorophores of use are listed below:
7-Hydroxy-4-methylcoumarin (AMCA/AMCA-X), Alexa fluor 350, Alexa
fluor 405, Alexa Fluor 430, Alexa Fluor 488, Alexa Fluor 532, Alexa
Fluor 546, Alexa Fluor 568, Alexa Fluor 594, Alexa Fluor 633, Alexa
Fluor 647, BODIPY 493/503, BODIPY 530/550, BODIPY 558/568, BODIPY
564/570, BODIPY 576/589, BODIPY 581/591, BODIPY 630/650-X, BODIPY
650/665-X, BODIPY FL, BODIPY TMR, BODIPY TR, Cascade Blue, Cy2,
Cy3, Cy3.5, Cy5, Cy5.5, Cy7, DY-505, DY-555, DY-647, Oregon Green
488, Oregon Green 500, Oregon Green 514, Pacific Blue, Pyrene,
Tetramethylrhodamine, Fluorescein, with or without suitable
functional groups and with or without a linker between the
fluorophore and the functional group. The fluorophores may have
appropriate functional groups e.g. amino, succinimidylester,
isothiocyanates, maleimide, sulphonyl chloride, carboxylic acid
etc.
[0065] Such fluorescently labelled particles can be used in various
assays e.g. multiplexed immunoassays. For example, a mixture of
particles with different colour codings and corresponding affinity
ligands may be added to a sample to be analysed. The analyte of
interest well bind by affinity to its corresponding ligand on the
coloured magnetic particles.
[0066] In a sandwich type immunoassay, a label (e.g. a fluorophore)
bound to a second antibody (affinity ligand) specific to the
analyte is then bound to the captured analyte. The label may be
selected from the group of well-known labels such as
radioimmunoassay, fluorescent or chemiluminescence immunoassay, or
immunoPCR technology. Extensive discussion of the known immunoassay
techniques is not required here since these are known to those of
skilled in the art." Jackowski, George; et al., US Patent
application 20020160425, Oct. 31, 2002).
[0067] The magnetic properties of the particle are used to
facilitate simple (automated) washing of the bound complex in order
to remove any unbound label and other reagents that will interfere
during the detection step. The degree of interference in the
absence of a washing step will depend on the nature of the system
used but in most cases it is essential to remove any unbound label.
In all cases, the result of washing is lowered background and
increased signal to noise ratio compared to an analysis without
washing.
[0068] The particle-analyte-label complex is then subjected to
analysis in one or two detection systems where a) the colour of the
beads is detected and b) the label bound is detected. This can be
done simultaneously in the same detector, in two parallel detectors
or successively by using the same detector twice or by moving the
bead complex from one detection system to another. In the latter
case it must be possible to track particles so that there is a
direct link between the particle colour and label detection.
[0069] Multiplexing is achieved by the colour coding of the
particles. By identifying which particle type has a signal from an
associated label, the analyte can be identified. Using two or more
different labels for detection of analytes can increase the level
of multiplexing.
[0070] The detection system must be able to analyse single
particles. This can be done in a flow based system such as a
microfluidic flow cytometer or in an immobilised bead array format.
In the later case, the beads are deposited passively or actively by
affinity or magnetic force to a solid surface such as a microscope
slide, bottom of microtitre well or structure in a microfluidic
system. The colour coding of the beads can be read using a high
resolution scanner while detection of labels on the surface of the
beads will need more sophisticated equipment such as a microscope
based image analysis system.
[0071] The detection limit of the system is determined by the
detector's ability to identify labels on the surface of the beads.
The sensitivity can thus be increased if more labels are introduced
per analyte or the label introduced is very large (in the sense
easy to detect).
[0072] In competitive assays, an added labelled (e.g. with a
fluorophore) analyte competing with the analyte of interest is
employed. An affinity ligand (antibody) with equal affinity for the
natural analyte and the labelled analyte is immobilized on the
colour coded beads, so that each set of colour coded beads has
specific affinity for one set of analytes.
[0073] The assays contemplated can utilise bead array technology.
In a bead array format, particles can be (passively) spotted or
positioned in confined areas on a surface using magnetism. The
results of the bead array are read in a two-step method in which
the beads are decoded. The position of each bead and its colour
coding is recorded by a suitable software and the signal from
positive beads is recorded and correlated with the nature of its
coding.
[0074] Alternatively, a labelled reporter need not be used and
instead the analyte may be further reacted in such a way that it is
bound by biotin or a/biotinylated molecule is bound to the
bead/analyte complex. This can then be bound to a streptavidin
coated slide and analysed by microscopy or laser scanning.
[0075] In a microfluidic competitive multiplexed immunoassay the
bead may act as both reporter and label. Beads may be coated with
an antibody against the target antigen. Multiplexing is achieved by
using one colour coding for each antibody-antigen pair of interest.
A standard competitive assay may then be carried out in the
presence of a biotinylated antigen. This can be achieved in any
suitable vessel, e.g. a tube, well, or a microfluidic device.
[0076] After incubation, magnetic separation is used to wash the
bead-antigen complex free of unincorporated antigens. The samples
are then passed over a streptavidin coated surface. Using optimised
flow or washing conditions, only the bead complexes with
competitive, biotinylated antigens are bound. Thus, samples
containing high concentration of a target antigen will have low or
no beads with the corresponding colour coding bound, while there
will be a high number of beads bound of a colour coding
corresponding to a low concentration target.
[0077] The microfluidic device can be a simple as a defined area on
a microscope slide, and can be made by microarray spotting of
streptavidin. Alternatively, more complex solutions can be made
incorporating mixing, magnetic separation and detection in the
microfluidic device.
[0078] Thus, viewed from another aspect the invention provides use
of the particles of the invention in an assay which comprises the
steps of: [0079] i) adding a coated magnetic particle comprising a
first fluorophore and an affinity ligand to a sample in which a
target analyte may be present; [0080] ii) allowing said affinity
ligand to bind with said analyte if present to form a complex;
[0081] iii) contacting the complex with a reporter to allow binding
of said reporter to said analyte wherein said reporter optionally
carries a second fluorophore; [0082] iv) magnetically separating
said particles from said sample; and [0083] v) detecting said first
fluorophore and if present said second fluorophore. or an assay
which comprises the steps of: [0084] i) contacting a coated
magnetic particle comprising a first fluorophore and an affinity
ligand with a sample in which a target analyte may be present and
in which an analyte carrying a reporter capable of competing with
said target analyte for the affinity ligand is present: [0085] ii)
allowing said affinity ligand to bind to said analyte, if present,
or said analyte carrying a reporter; [0086] iii) magnetically
separating said particles from said sample; and [0087] iv)
detecting the first fluorophore.
[0088] Whilst assays have been described here with reference to
fluorophores, it would of course be possible to use other labels in
conjunction with fluorophores. For example, differently sized beads
could be employed or beads labelled with radio labels.
[0089] The invention will now be described further by reference to
the following Examples. These are not intended to be limitative but
merely exemplary of the invention.
[0090] In the Examples percentages are by weight unless specified
otherwise.
EXAMPLE 1
Seed Latex
[0091] 18.0 g of a polystyrene latex with 0.5 micrometer monosized
particles made by emulsion polymerisation was stirred at room
temperature together with an emulsion of 10.8 g dioctanoyl peroxide
and 10.8 g acetone in 108.6 g 0.6% sodium dodecyl sulphate (SDS) in
water. After 20 hours, the reaction mixture was added to an
emulsion of 93.3 g methyl methacrylate and 93.3 g styrene in 859.1
g of 0.25% SDS-solution. After stirring for 2 hours at 25 W, 803.4
g of a solution of 0.05% KI in water was charged into the reactor
and the temperature was raised to 700 C for 10 hours. After
polymerisation, a seed latex containing 8.6% dry substance of 1.9
micrometer monosized particles was obtained.
EXAMPLE 2
Porous Epoxy Particles
[0092] 34.5 g of the particles of Example 1 was mixed with an
emulsion of 5.9 g dioctanoyl peroxide and 5.9 g acetone in 59.1 g
0.5% SDS in water. After stirring for 24 hours at room temperature,
the reaction mixture was added to an emulsion of 51.8 g glycidyl
methacrylate, 51.8 g ethylene glycol dimethacrylate and 103.6 g
butyl acetate in 1013 g of a 0.1% solution of hydroxypropyl
methylcellulose in water. The suspension was stirred for 2 hours at
room temperature and 474.5 g of a 0.44% solution of hydroxypropyl
methylcellulose in water was added. The temperature was raised
slowly to 70.degree. C. and the particles were polymerised for 5
hours. After purification with methanol, monosized particles with
diameters of 7.5 micrometers were obtained. By nitrogen adsorption,
the specific surface area was determined to be 19.2 m.sup.2/g dry
substance. Auto-fluorescent of these particles could not be
observed by fluorescence microscopy or flow cytometry.
EXAMPLE 3
Superparamagnetic Particles from Epoxy Particles
[0093] 3.3 g FeCl.sub.2.times.4H.sub.2O and 7.9 g
FeCl.sub.3.times.6H.sub.2O were dissolved in 53 g water and added
to a dispersion of 5 g dry substance of the porous epoxy particles
of Example 2 in 61 g water. The suspension was cooled to 50 C and
stirred for a few minutes before 62 ml of 25% NH.sub.3 in water was
added. The temperature was raised to 80.degree. C. for 2 hours. The
suspension was cooled and the particles were purified with water by
several cycles of centrifugation. After purification, the particles
were transferred to methanol and analysed by fluorescence
microscopy. No autofluorescence could be observed under the same
conditions as would show considerable autofluorescence for
conventional magnetic polymer particles. The iron content was
determined to be 67 mg Fe/g Dry substance (DS). The particles
showed superparamagnetic behaviour and were attracted to a
magnet.
EXAMPLE 4
Coating of Superparamagnetic Particles
[0094] 3 g dry substance of the magnetic particles of Example 3
were transferred to 15 g diglyme by centrifugation and
resuspension. The suspension was stirred and 10 g butanediol
diglycidyl ether and 5 g glycidol were added. The temperature was
raised to 90.degree. C. for 20 hours. The particles were purified
with methanol. FT-IR absorption of 1080 cm.sup.-1 confirmed
appearance of ether coating from the epoxides. The particles were
analysed by fluorescence microscopy. No green or red
autofluorescence was observed.
[0095] The particles of Examples 6, 8 and 11 can be coated
analogously.
EXAMPLE 5
Porous Particles with Sulphonic Groups
[0096] 10 g dry substance of the porous epoxy particles of Example
2, suspended in 100 ml water were mixed with 12.6 g sodium sulphite
and 13.55 g sodium tetrabutyl ammonium hydrogen sulphate. The
mixture was stirred for 20 hours at 80.degree. C. After
purification with water, FT-IR absorption of 1035 cm.sup.-1
confirmed introduction of sulphonic groups.
EXAMPLE 6
Superparamagnetic Particles from Particles with Sulphonic
Groups
[0097] 3.3 g FeCl.sub.2.times.4H.sub.2O and 7.9 g
FeCl.sub.3.times.6H.sub.2O were dissolved in 53 g water and added
to a dispersion of 5 g dry substance of the particles of Example 5
in 96 g water. The suspension was cooled at 5.degree. C. and
stirred for a few minutes before 62 ml of 25% NH.sub.3 in water was
added. The temperature was raised to 80.degree. C. for 2 hours. The
suspension was cooled and the particles were purified with water by
several cycles of centrifugation. After purification, the particles
were transferred to methanol and analysed by fluorescence
microscopy. No autofluorescence could be observed under the same
conditions as would show considerable autofluorescence for
conventional magnetic polymer particles. The beads were attracted
to a magnet and showed superparamagnetic behaviour. The content of
iron was determined to be 75.5 mg/g DS and the content of sulphur
was determined to be 0.28 mmol/g DS.
EXAMPLE 7
Porous Particles with Carboxylic Groups
[0098] 28.8 g of the seed latex of Example 1 was mixed with an
emulsion of 6.4 g dioctanoyl peroxide and 10.6 g acetone in 106.5 g
0.5% SDS in water. After stirring for 24 hours at room temperature,
the reaction mixture was added to an emulsion made from 20.7 g
methacrylic acid, 83.0 g ethylene glycol dimethacrylate, 103.7 g
butyl acetate, 0.23 g SDS and 975 g of a 0.8% solution of polyvinyl
pyrrolidone in water. The suspension was stirred for 2 hours at
room temperature and 470 g water was added. The temperature was
raised slowly to 70.degree. C. and the particles were polymerised
for 5 hours. After purification with methanol, monosized particles
with diameters of 8.3 micrometers were obtained. By nitrogen
adsorption, the specific surface area was measured to be 210
m.sup.2/g DS.
EXAMPLE 8
Superparamagnetic Particles from Carboxylic Particles
[0099] 2.2 g FeCl.sub.2.times.4H.sub.2O and 3.0 g
FeCl.sub.3.times.6H.sub.2O were dissolved in 106 g water and added
to a dispersion of 5 g dry substance of the particles of Example 7
in 44 g water. The suspension was stirred for some minutes before
51 ml of 25% NH.sub.3 in water was added. The temperature was
raised to 80.degree. C. for 1 hour. The suspension was cooled and
the particles were purified with water by several cycles of
centrifugation. After purification, the particles were transferred
to methanol and analysed by fluorescence microscopy. No
autofluorescence could be observed under the same conditions as
would show considerable autofluorescence for conventional magnetic
polymer particles. The particles were attracted to a magnet and the
content of iron was determined to 42 mg/g DS.
EXAMPLE 9
Porous Epoxy Particles
[0100] 32.0 g of the particles of Example 1 was mixed with an
emulsion of 6.8 g dioctanoyl peroxide and 11.3 g acetone in 114.1 g
0.5% SDS in water. After stirring for 24 hours at room temperature,
the reaction mixture was added to an emulsion of 57.6 g glycidyl
methacrylate, 57.6 g trimethylolpropane trimethacrylate, 115.2 g
butyl acetate, 0.26 g SDS and 1085 g of a 1.1% solution of
polyvinyl pyrrolidone in water. The suspension was stirred for 2
hours at room temperature and 521 g water was added. The
temperature was raised slowly to 70.degree. C. and the particles
were polymerised for 5 hours. After purification with methanol,
monosized particles with diameters of 7.5 micrometers were
obtained. By nitrogen adsorption, the specific surface area was
measured to 64 m2/g DS. Auto-fluorescence of these particles could
not be observed by fluorescence microscopy.
EXAMPLE 10
Porous Amino Particles
[0101] 78 g dry substance of the particles of Example 9, were
transferred to methanol and mixed with 1550 ml of 25% NH.sub.3 in
water. The suspension was stirred at 60.degree. C. overnight,
before the particles were purified with water. The content of
primary amino groups was determined to be 0.8 mmol/g DS by a
ninhydrin reaction method.
EXAMPLE 11
Superparamagnetic Particles from Amino Particles
[0102] 3.9 g FeCl.sub.2.times.4H.sub.2O and 7.9 g
FeCl.sub.3.times.6H.sub.2O were dissolved in 100 g water and added
to a dispersion of 10 g dry substance of the particles of Example
10 in 60 g water. The suspension was stirred for some minutes
before 81 ml of 25% NH3 in water was added. The temperature was
raised to 80.degree. C. for 2 hours. The suspension was cooled and
the particles were purified with water by several cycles of
centrifugation. After purification, the particles were transferred
to methanol and analysed by fluorescence microscopy. No
autofluorescence could be observed under the same conditions as
would show considerable autofluorescence for conventional magnetic
polymer particles. The particles were attracted to a magnet and
showed superparamagnetic behaviour. The content of iron was
determined to be 73 mg/g DS.
EXAMPLE 12
Measurement of Autofluorescence by Fluorescence Microscopy
Instrumentation and Software
[0103] The autofluorescence of superparamagnetic particles was
measured with a BX-61 fluorescence microscope from Olympus. The
microscope was equipped with a 100 W mercury lamp and filter cubes
from Chroma Technology. The autofluorescence was measured through a
filter cube with an excitation band pass-filter at 450 nm +/-25 nm.
a beam splitter at 480 nm, and emission band pass filter at 520 nm.
The objective used was an Uplan-Apo 40.times.. The signal was
detected with a F-view digital monochrome CCD camera (4096 grey
levels). The exposure times were 600 ms in all the analyses.
[0104] The imaging analyses were performed with a software package,
Analysis, from Soft Imaging Systems. The mean grey value of a
particle population (MGV) is calculated as the mean of the mean
intensity for each particle, resulting in an intensity value, that
adjust for the differences in particle area. The results are given
as Mean Grey Value for the particles. To obtain comparable values
for the auto-fluorescence of the different types of particles, the
greyness values for the background have to be subtracted. The
particle autofluorescence values are therefore calculated as the
difference in Mean Grey Values between the particles and the
background.
Sample Preparation
[0105] The particle samples were diluted with a 1:1 mixture by
volume of 1.5 g g/L SDS in water and glycerol.
[0106] Two strips of a two-sided tape (3M Scotch 136 D) were
attached to a microscope slide, with a distance between the strips
of approximately 3 mm. A microscope cover glass was attached on the
top of the strips to give a capillary channel between the slide and
the cover glass. The diluted particle samples were mounted into the
cannels by capillary forces, and the particles were allowed to
settle before measurements were performed.
Results
[0107] Two different types of uncoated magnetic polymer particles
having a styrene/divinylbenzene matrix polymer and the uncoated
particles of Examples 3, 6, 8 and 11 were investigated. The results
are given in Table 1.
[0108] In Table 2 the results are given for coated magnetic polymer
particles. Three different types of coated magnetic polymer
particles having a styrene/divinylbenzene matrix polymer and the
coated particles of Example 4 were investigated.
[0109] The autofluorescence of the particles is given as the
difference (.DELTA. MGV) between the Mean Grey Value of the
particles and the Mean Grey Value of the background. TABLE-US-00001
TABLE 1 Particle Raw data from Autofluorescence measurement given
as MGV MGV Sample Description .DELTA. MGV Particles Background A
S/DVB 411 1016 605 B S/DVB 411 1053 642 C Ex 3 83 678 595 D Ex 6 79
686 607 E Ex 8 51 796 745 F Ex 11 62 595 533
[0110] TABLE-US-00002 TABLE 2 Particle Raw data from
Autofluorescence measurement given as MGV MGV Sample Description
.DELTA. MGV Particles Background G S/DVB 769 1409 640 H S/DVB 1423
2087 664 I S/DVB 1277 1905 628 J Example 4 287 971 684
EXAMPLE 13
Coating of Superparamagnetic Particles
[0111] 0.5 gram of particles with diameter 5.1 .mu.m, obtained by
the method described in example 11, were transferred to 9.5 gram
diglyme. 4.6 gram glycidol was added. The suspension was shaken for
20 hours at 75.degree. C. The particles were purified with diglyme
and methanol. FT-IR adsorption of 1080 cm.sup.-1 confirmed
appearance of ether coating from the epoxide. The particles were
analysed by fluorescence microscopy.
EXAMPLE 14
Coating of Superparamagnetic Particles
[0112] 0.5 gram of particles with diameter 5.1 .mu.m, obtained by
the method described in example 11, were transferred to 9.5 gram
toluene. 3.6 gram butandiol diglycidylether and 8.3 ethyl hexyl
glycidylether were added. The suspension was shaken for 20 hours at
75.degree. C. The particles were purified with toluene and
methanol. FT-IR adsorption of 1080 cm.sup.-1 confirmed appearance
of ether coating from the epoxides. The particles were analysed by
fluorescence microscopy.
EXAMPLE 15
Coating of Superparamagnetic Particles
[0113] 0.5 gram of particles with diameter 5.1 .mu.m, obtained by
the method described in example 11, were transferred to 9.5 gram
diglyme. 2.3 gram butyl glycidylether and 3.3 gram glycidol were
added. The suspension was shaken for 20 hours at 75.degree. C. The
particles were purified with diglyme and methanol. FT-IR adsorption
of 1080 cm.sup.-1 confirmed appearance of ether coating from the
epoxides. The particles were analysed by fluorescence
microscopy.
EXAMPLE 16
Coating of Superparamagnetic Particles
[0114] 0.5 gram of particles with diameter 5.1 .mu.m, obtained by
the method described in example 11, were transferred to 9.5 gram
toluene. 3.3 g glycidol and 3.6 g butandiol diglycidylether were
added. The suspension was shaken for 20 hours at 75.degree. C. The
particles were purified with toluene and methanol. FT-IR adsorption
of 1080 cm.sup.-1 confirmed appearance of ether coating from the
epoxides. The particles were analysed by fluorescence
microscopy.
EXAMPLE 17
Amino Particles
[0115] 15 gram particles, obtained by the methods described in
example 16, was added to a mixture of 135 gram diglyme and 135 gram
ethylenedioxy diethylamine. The dispersion was heated to 60.degree.
C. After 4 hours the particles were purified with methanol and
anhydrous dimethylformamide. Primary amino groups in the particles
were verified by a ninhydrin reaction method. The particles were
analysed by fluorescence microscopy and flowcytometry.
EXAMPLE 18
[0116] Measurement of Autofluorescence by Fluorescence
Microscopy:
Instrumentation and Software
[0117] The autofluorescence of superparamagnetic particles from
Examples 13-17 was measured with a BX-61 fluorescence microscope
from Olympus. The microscope was equipped with a 75 W xenon lamp
and filter cubes from Chroma Technology. The autofluorescence was
measured through three different filter cubes using the exposure
times as shown in table 3. The objective used was an Uplan-Apo 20
x. The signal was detected with an F-view digital monochrome CCD
camera (4096 grey levels). The imaging analyses were performed with
a software package, Analysis, from Soft Imaging Systems. The mean
grey value of a particle population (MGV) is calculated as the mean
of the mean intensity for each particle resulting in an intensity
value, which adjusts for the differences in particle area. The
results are given as Mean Grey Value for the particles. To obtain
comparable values for the autofluorescence of the different types
of particles, the greyness values for the background have to be
subtracted. The particle autofluorescence values are therefore
calculated as the difference in Mean Grey Values between the
particles and the background. TABLE-US-00003 TABLE 3 Filter
Settings Exposure Filter Beam Time Cube Excitation Splitter
Emission 500 ms 1 450(50) nm 480 nm 520 nm long pass 5000 ms 2
550(30) nm 580 nm 620(60) nm 50000 ms 3 630(30) nm 650 nm 665 nm
long pass
Sample Preparation
[0118] All the particles were diluted with phosphate buffer saline
(pH 7.4) before transferring to a capillary channel of the
microscope slide, as described in example 12.
Results
[0119] Two different types of coated magnetic polymer particles
having a styrene/divinylbenzene matrix polymer and the coated
particles of Examples 13, 14, 15, 16 and 17 were investigated. The
results given in Table 4 are also compared to commercial available
calibration particles, Certified blanks.
[0120] The Certified blank particles are included in MESF
calibration set obtained from Bangs Laboratories, Inc. The
particles are 7,4 micrometer compact non-magnetic polymer
particles, which may be used as non-fluorescent references for
flowcytometry applications as described by i.e. Schwartz in U.S.
Pat. No. 5,089,416. TABLE-US-00004 TABLE 4 .DELTA. MGV Filter
.DELTA. MGV Filter .DELTA. MGV Filter Sample Description Cube 1
Cube 2 Cube 3 A Blank -1 -1 -67 B PS/DVB 1087 1851 1269 C PS/DVB
833 829 426 D EX 13 333 31 -72 E EX 14 77 18 7 F EX 15 11 14 -51 G
EX 16 1 67 -64 H EX 17 53 35 -45
EXAMPLE 19
[0121] Measurement of Autofluorescence by Flowcytometry
Instrumentation and Software
[0122] The autofluorescence of superparamagnetic particles from
Example 17 was measured with BD LSR II flowcytometer from BD
biosciences. The excitation source was a 488 nm solid-state laser
and a 633 nm helium neon laser. The excitation and filter
specifications for the different fluorescence detectors are
summarized in table 5. The voltage of the PMT detectors was all set
to 600 V. The statistics were carried out by setting a gate in the
plot of forward scatter (FSC) against side scatter (SSC), which
included the single particles only. The flowcytometer was set to
count 10 000 particles with an approximate rate of 100 events per
second for each sample. The area-mean was determined for each
sample. For area detection the signal will decrease with a decrease
in size for the same kind of particle. (Because the intensity from
the flow measurement is an integral of the detected intensity
profile generated when the particle is passing the objective.)
TABLE-US-00005 TABLE 5 Filter Settings of BD LSR II flow cytometer
Excitation Emission Source Beam Splitter Filter Detector 488 nm 505
nm long pass 530(30) nm 1 laser 550 nm long pass 575(26) nm 2 685
nm long pass 695(40) nm 3 735 nm long pass 780(60) nm 4 633 nm
blank 660(20) nm 5 laser 735 nm long pass 780(60) nm 6
Sample Preparation
[0123] All samples were diluted with phosphate buffer saline (PBS
pH 7,4) prior to the analysis. The particle concentration was
adjusted to give an approximate count of 100 events per second by
the flowcytometer.
Results
[0124] Two different types of coated magnetic polymer particles
having styrene/divinylbenzene and the coated particles of example
17 were investigated. The results given in Table 6 are also
compared to commercial available calibration particles, Certified
blanks.
[0125] The Certified blank particles are included in MESF
calibration set obtained from Bangs Laboratories, Inc. The
particles are 7,4 micrometer compact non-magnetic polymer
particles, which may be used as non-fluorescent references for
flowcytometry applications as described by i.e. Schwartz in U.S.
Pat. No. 5,089,416. TABLE-US-00006 TABLE 6 Intensity: mean channel
number of singlets Flow Measured by detector Cytometry #1 #2 #3 #4
#5 #6 Blank 246 32 14 2 100 3 PS/DVB 3040 784 1088 416 212 50
PS/DVB 2166 492 471 149 87 10 Ex 17 579 84 26 4 31 0
[0126] By use of MESF calibration kits for fluorescein
isothiocyanate (FITC), phycoerythrin (PE) and PE-Cy5, received from
Bangs Laboratories Inc, the measured autofluorescence can be
assigned to values of Molecules of Equivalent Soluble Fluorophore
(MESF). The MESF definition may be found at
http://nyl.nist.gov/pub/nistpubs/jres/107/1/j71schw.pdf
[0127] In Table 7 the estimated MESF values when comparing the
autofluorescence to the respective calibration curves are given.
TABLE-US-00007 TABLE 7 Excitation Source 488 nm Laser Emission
filter 530(30) 575(26) 695(40) MESF MESF MESF FITC PE PE-Cy5 Ex 17
1342 362 66 PS/DVB 7225 3625 2635 PS/DVB 5122 2242 1151 Blank 563
134 36
EXAMPLE 20
Incorporation of Bodipy 630/650 Giving Superparamagnetic Particles
with Three Levels of Fluorescence Intensity
[0128] A 10% (w/w) dispersion in dimethyl formamide of 8 .mu.m
particles, obtained by the method described in example 17, was
transferred to three vials A, B and C. 5.6 mg Bodipy 630/650
succinimidyl ester (from Molecular Probes Inc.) was mixed with 11.9
mL dimethylformamide and added to the particle dispersions in the
vials. In vial A, 50 g particle dispersion was mixed with 10.6 mL
colour solution, in vial B 30 g particle dispersion was mixed with
0.6 mL colour solution and in vial C 30 g particles dispersion was
mixed with 0.06 mL colour solution. The mixtures were shaken for 24
hours at ambient temperature and then placed on a magnet. The
particles were purified with methanol, 5% triethylamine in methanol
and water and diluted in phosphate buffer saline (PBS, pH 7,4). The
particles were analyzed by fluorescence microscopy and
flowcytometry.
Measurement by Fluorescence Microscopy
[0129] The microscopy measurements were performed with a BX-61
fluorescence microscope from Olympus, equipped with a 75 W Xenon
lamp and filter cubes from Chroma Technology. The fluorescence was
measured through a filter cube with excitation bandpass filter at
630(30) nm, beamsplitter at 650 nm, and emission longpass filter at
665 nm. The objective used was Uplan-Apo 20.times.. The camera
exposure time settings were adjusted to the corresponding amount of
dye attached to the particles.
[0130] All the particles were diluted with phosphate buffer saline
(pH 7.4) and transferred to a capillary channel of the microscope
slide, as described in example 12.
[0131] The resulting fluorescence intensities given as .DELTA.MGV
were calculated as. In example 12. The resulting coefficient of
variation (% CV) is defined as the standard deviation of mean grey
value (MGV) of particles divided by the mean grey value (MGV) of
particles multiplied by a factor of 100. The coloured particles
were compared with similar particles without dye incorporated
(blank references). TABLE-US-00008 TABLE 8 Exposure MGV MGV
Microscopy time (ms) Particle Background .DELTA.MGV CV % Ex 20, A
50 2349 76 2273 10 Ex 20, B 50 425 64 361 10 Ex 20, C 100 153 64 89
8 Blank 1000 85 96 -11 --
Measurements by Flowcytometry
[0132] The flowcytometry measurements were performed with a BD LSR
II flowcytometer from Becton-Dickinson. The instrument was equipped
with a 633 nm laser as excitation source. For detection an emission
bandpass filter with specification 660(20) nm, corresponding to the
APC (Allophycoerithrin) filter-settings for the BD LSR II
flowcytometer, was used. The voltage of the PMT detector was set to
250 V. The statistics were carried out by setting a gate in the
plot of forward scatter (FSC) against side scatter (SSC), including
single particles only. The flowcytometer was set to count 10 000
particles with an approximate rate of 100 events per second for
each sample. The single particle population contained typically 90%
of the total number of events. The area mean and coefficient of
variation was determined for each sample. The coefficient of
variation (% CV) is defined as the standard deviation of singlets
divided by the mean intensity of singlets, at that specific
voltage, multiplied by a factor of 100.
[0133] The coloured particles were compared with similar particles
without dye incorporated, named blank references. All samples were
diluted with phosphate buffer saline (PBS pH 7,4) prior to the
analysis. The particle concentration was adjusted to give an
approximate count of 100 events per second by the flowcytometer.
The results are given in Table 9. TABLE-US-00009 TABLE 9 Flow
Intensity: Mean channel no. Intensity Cytometry singlets PMT
Voltage = 250 v Distribution CV % Ex 20, A 8848 16 Ex 20, B 1536 16
Ex 20, C 153 42 Blank 0 --
EXAMPLE 21
Incorporation of Bodipy 650/665 Giving Superparamagnetic Particles
with Three Levels of Fluorescence Intensity
[0134] 5 .mu.m particles obtained with the method described in
example 17 were transferred into dimethylformamide giving 10% w/w
dispersion. 1.5 mL of the dispersion was transferred to three vials
each, A, B and C. 1,1 mg Bodipy 650/665 succinimidyl ester (from
Molecular Probes Inc.) was mixed with 1,25 mL dimethylformamide.
The Bodipy solution was mixed with the particles dispersions giving
the following amount of dye per mg dry substance (DS) of particles;
in A) 1,0 mg/g DS, in B) 0,1 mg/g DS and in C) 0,014 mg/g DS. The
dispersions were shaken at ambient temperature over night. The
particles were purified with a solution of 5% triethylamine in
methanol and phosphate buffer saline (PBS, pH 7,4).
[0135] The particles were analyzed by fluorescence microscopy and
flowcytometry as described in Example 20. The results given in
Table 10 and Table 11 demonstrate that particle populations can be
coloured with a large difference in intensity also for this type of
dye. TABLE-US-00010 TABLE 10 Exposure MGV MGV Microscopy time (ms)
Particle Background .DELTA.MGV CV % Ex 21, A 10 511 64 447 8 Ex 21,
B 100 758 76 682 10 Ex 21, C 1000 826 96 730 9 Blank 50 000 1113
1148 -35 --
[0136] TABLE-US-00011 TABLE 11 Flow Intensity: Mean channel no.
Intensity Cytometry singlets PMT Voltage = 250 v Distribution CV %
Ex 21, A 1133 15 Ex 21, B 192 15 Ex 21, C 20 73 Blank 0 --
EXAMPLE 22
Incorporation of DY-647 Giving Superparamagnetic Particles with
Three Levels of Fluorescence Intensity
[0137] 5 .mu.m particles obtained with the method described in
example 17 was transferred into dimethylformamide giving 10% w/w
dispersion. 1.5 mL of the dispersion was transferred to three vials
each, A, B and C. 1,1 mg DY-647 succinimidyl ester (from Dyomics
GmbH) was mixed with 1,25 mL dimethylformamide. The dye solution
was mixed with the particles dispersions giving the following
amount of dye per mg dry substance (DS) of particles; in A) 1,0
mg/g DS, in B) 0,1 mg/g DS and in C) 0,01 mg/g DS. The dispersions
were shaken at ambient temperature over night. The particles were
purified with a solution of 5% triethylamine in methanol, water and
diluted in phosphate buffer saline (PBS, pH 7,4).
[0138] The particles were analyzed by fluorescence microscopy and
flowcytometry as described in Example 20. The results, given in
Table 12 and Table 13, demonstrate that particle populations can be
coloured with a large differences in intensity also for this type
of dye (DY-647). TABLE-US-00012 TABLE 12 Exposure MGV MGV
Microscopy time (ms) Particle Background .DELTA.MGV CV % Ex 22, A
10 1135 65 1070 15 Ex 22, B 100 1180 81 1099 8 Ex 22, C 1000 1298
98 1200 10 Blank 50 000 1113 1148 -35 --
[0139] TABLE-US-00013 TABLE 13 Flow Intensity: Mean channel no.
Intensity Cytometry singlets PMT Voltage = 250 v Distribution CV %
Ex 22, A 2955 14 Ex 22, B 356 9 Ex 22, C 38 227 Blank 0 --
EXAMPLE 23
[0140] Fluorescent particles with narrow intensity distribution 5
.mu.m particles obtained by the method described in example 17 were
transferred to dimethylformamide. 15 gram of 10% (w/w) particle
dispersion was mixed with 1,2 mg of DY-647 succinimidylester
dissolved in 2 mL dimethylformamide. After 2 hours a small sample
of the coloured particles was purified with methanol and phosphate
buffer saline (PBS, pH 7,4). The sample were analysed on the
flowcytometer as described in examples 20, 21 and 22 with one
exception, use of slower sheath fluid flow (low setting). The
result, given in Table 14, shows that the superparamagnetic beads
can be coloured to give particle populations with very narrow
intensity distribution. TABLE-US-00014 TABLE 14 Flow Intensity:
Mean channel no. Intensity Cytometry singlets PMT Voltage = 250 v
Distribution CV % A 2336 6
EXAMPLE 24
Colouring Prior to Coating
Colouring Procedure
[0141] Particles obtained by the method described in Example 11
were transferred to anhydrous dimethylformamide. In four different
bottles, 38 gram of 5% particle dispersion was mixed with 4 mL of
dimethyl formamide containing 2 mg dye. The four fluorescent dyes
used, AMCA-X, Bodipy TMR, Bodipy FL (from Molecular Probes Inc) and
DY?555 (from Dyomics GmbH) had succinimidyl ester functionality.
After stirring for 20 hours at ambient temperature, the particles
were purified several times with 5% triethylamine in methanol and
finally with methanol. Prior to microscopy analyses, small samples
of particles were diluted in phosphate buffer saline (pH 7,4).
[0142] Table 15 shows the fluorescence intensities of dyed
particles as the DMGV value, analyzed in appropriate filter for the
specific fluorophore attached to the particles.
Coating Procedure
[0143] 0,3 gram of the coloured particles above, were transferred
to diethylene glycol dimethyl ether. The content of particles in
the dispersions were justified to 10% dry substance (DS). 2,1 gram
1,4-Butandiol diglycidylether and 2,2 gram glycidol were added to
the particle suspensions. The mixtures were shaken on vortex and
placed in a shaker (LabMate) at 75.degree. C. for 20 hours. The
particles were purified twice with methanol and with phosphate
buffer saline (pH 7,4). Prior to microscopy analyses small samples
of particles were diluted with phosphate buffer saline (pH
7,4).
[0144] Table 15 shows the fluorescence intensities of dyed and
coated particles as the DMGV value, analyzed in appropriate filter
for the specific fluorophore attached to the particles. The results
indicate that the coumarin-dye, AMCA-X (from Molecular Probes Inc)
may be a better alternative than a series of other dyes when the
coating step is done after the colouring. TABLE-US-00015 TABLE 15
.DELTA.MGV .DELTA.MGV (Dyed and (Dyed coated Excitation Emission
Exposure Dye particle) particle) filter nm filter nm time AMCA-X
470 614 360(40) 420 LP 10 Bodipy 1137 66 550(30) 620(60) 10 TMR
Bodipy 1710 174 450(50) 520 LP 10 FL DY-555 2492 40 550(30) 620(60)
20
[0145] By microscopy, particles coloured with AMCA-X and coated
were compared to equivalent particles without dye, blank
references, detected through different filters. As can be seen in
Table 16, the AMCA-dye does not disturb the detection in filters
suitable for a reporter signals TABLE-US-00016 TABLE 16 Excitation
filter (nm) 360 (40) 450 (50) 550 (30) 630 (30) Emission 420 LP 520
LP 620 (60) 665 LP filter (nm) Exposure time 10 ms 500 ms 5000 ms
50000 ms Particle type .DELTA.MGV .DELTA.MGV .DELTA.MGV .DELTA.MGV
Blank reference 0 90 51 -186 Dyed with AMCA 584 108 17 -110 and
coated
* * * * *
References