EP0227679A1 - Device and method for trapping and analyzing particles - Google Patents

Abstract

A device is used to collect particles carried by a gas or a liquid in order to facilitate their analysis. The device comprises an element (1) for filtering gas or liquid through the device and elements (2, 3, 4) for collecting and retaining the particles. A support element (4) essentially a funnel (9) narrowing in the filtering direction and containing in its first part, seen in the filtering direction, a support surface (6) supporting at least one filter (2) which collects and retains the particles, and an electrode device (5) placed before the filter (2), seen in the direction of filtering. The device is also used to identify at least one specific particle or one of its parts, for example a certain type of virus, bacteria, etc. A plurality of these specific particles are distributed or dispersed in a liquid or an analysis gas and pass through the aforementioned filter. The permeability of the filter to the analysis liquid or gas is chosen so that the particles are collected on the filter while the analysis gas or liquid passes through the filter. At least one antibody for the specific particle, preferably a monoclonal antibody, is added to the specific particles collected on the filter.

Description

Device and method for trapping and analyzing particles

The present invention relates to' a device for collection of gas-borne or liquid-borne particles to facilitate analysis of the particles, the said device comprising means for generation of percolation of the said gas or liquid through the device and means for collection and retention of the said particles. - The invention also relates to a method of identifying at least one specific particle or a portion thereof, for example a certain type of virus, or bacteria etc., a plurality of the said specific particles then being distributed or dispersed in an analysis liquid or analysis gas and fed through a device as above, the said device being provided with at least one filter, the permeability of which to the analysis liquid or analysis gas is so selected that the said specific particles are collected on the filter while the analysis liquid or analysis gas otherwise passes through the filter.

The invention finally relates to a method of testing which antibodies are neutralized to specific particles, i.e. inactiv ating.

In many fields there is a need to be able to separate particles from gases or liquid for subsequent analysis of the particles. Examples of such areas are for determination of air pollutants, wound analysis, blood analysis etc.

The approach most commonly adopted at the present time is for a number of samples to be taken which corresponds to the number of analyses which are to be subsequently performed, a circumstance which has as a result that a large number of samples have to be taken.

To perform an analysis after the sampling is today a time- consuming procedure, among other things because the sample taken often has to be treated additionally, for instance be filtered through different filters in order to obtain the specific particles it is desired to analyse, and because the samples taken are not especially arranged for the rapid analyses which are currently available but not in general use for various reasons. One example of an apparatus for rapid analysis is an electron microscope, with the aid of which an analysis of a particle sample can be performed very rapidly.

The object of the present invention is to provide an arrangement with the aid of which a very rapid analysis of particles can be performed directly and which device in itself, in a further development of the inventive concept, performs the necessary separations of different particles right at the sampling stage, so that the number of requisite samples is reduced to a minimum. The invention is characterized in the case of the type of device mentioned in the descriptive preamble of a support device which is elaborated largely as a funnel which is narrowed off in the direction of percolation at which in its first portion, viewed in the direction of percolation,, is elaborated with a supporting surface which is arranged to supportingly carry at least one filter which collects and retains the said particles, and by an electrode device which viewed in the direction of percolation is sited before the filter. The invention is characterized particularly. in that the said filter consists of several filters placed one above the other viewed in the. direction of percolation and in that the said filters are easily mutually separable. In particular, an additional further development of the inventive concept is characterized in that each filter has reduced permeability for particles than the filter immediately preceding it, viewed in the direction of percolation.

By means of the device described hereintofor the collection of different particles and analysis in a scanning electron microscope can be easily performed. In a further development of the invention according to the above it has emerged that the fundamental idea has a far wider field of application than was apparatus than scanning electron microscopes and can also be used for additional purposes. In using the device as described hereintofor the particles collected and concentrated on the filter or filters were demonstrated with the aid of a so-called sputter, which coats the particles collected in the filters with ionised gold, the said particles subsequently being detected in a scanning electron microscope.

By addition in accordance with accompanying Claim 11 of an antibody aimed at the specific particle to be identified several tangible advantages are obtained. For example, the point of time for marking can be chosen fairly freely, either applied before the percolation of the analysis liquid or. gas through the filter or filters or after this has occurred, various types of marking can also be executed and thereby different types of analysis instrument used, for example a scanning electron microscope, gamma counter, fluorescence microscope, spectrophotometer etc. The latter possibility is extremely important, among other things since scanning electron microscopes are relatively expensive and rare in comparison with gamma counters and fluorescence microscopes. The device according to the invention is described in greater detail below and with reference to the accompanying drawings, of which Fig. 1 illustrates a view across a disassembled device according to the invention. Fig. 2 shows a cross-section of a variant of the device according to Fig. 1 with certain guards applied. Fig. 3 shows a cross-section through a further variant of the invention and Fig. 4 illustrates the embodiment according to Fig.3 with an attachment.

The device according to Fig. 1 comprises an electrode device 5, which is required in order to be able to carry out a rapid analysis in an electron microscope. The electrode device 5 is : made of a suitable conductive material, for instance brass, or is coated with a conducting surface layer. The electrode device 5 comprises a thin, annular upper edge 10 and an inwardly bevelled edge 9, which delimit, an aperture 8 through the electrode device 5. The edge 10 and the bevelled edge 9 are made as small as possible, viewed in the horizontal direction in Fig. 1 so as to permit scanning by means of the electron microscope of as large a portion of the aperture 8 as possible with due allowance to the fact that the surface of the edge 10 and the lower surface of the bevelled edge 9, as seen in Fig. 1, shall comprise retaining surfaces for the filter 2, which is designed with a permeability adapted to the size of the particles to be analysed so that the desired particle sizes remain in the filter 2.

As a rule, the said filter 2 must be carried or supported by a coarse mesh gauze 3 relative to the filter 2 or a similar means with high permiability to the particle size concerned, which gauze 3 in turn along the outer edge thereof is tightly carried or supported by a supporting surface 6, which is formed to advantage in the upper outer edge by a cylinder or a funnel 7 and which together with the funnel 7 forms a supporting device 4 for the filter 2.

The supporting surface is made to advantage as small as possible and corresponds in size largely to the aggregate area of the edge 10 and the bevel edge 9 which faces towards the filter 2. The .upper portion of the funnel 7 has essentially the same size as the aperture 8.

By means of a suitable means 1, for instance a suction device, a vacuum is generated in the lower portion of the device, viewed in Fig. 1, while the aperture 8 of the electrode device 5 faces towards the area from which it is desired to take samples.^' This area may consist for instance of an open, bacteria-coated wound, urine, blood or other particles containing liquid or gas, the particles of which are to be analysed, and the said particles remain on the filter 21 while in contrast the remaining portion of the liquid or gas flows on through the gauze 3, through the funnel 7 and out into the suction device 1.

The device can then be removed from the suction device 1 and direct used as an electrode in an electron microscope, whereupon the particles collected by the filter 2 can be directly observed and analysed in the electron microscope without any intermediate actions, treatments etc.

The electrode device 5 is elaborated to advantage so that it can pass with a press fit over the support device 4, whereby the filter 2 and the gauze 3 are retained. This is achieved appropriately in that (see especially Fig. 2) the upper outer edge of the support device 4 is inclined slightly inwards and the inner upper edge of the electrode device 5 has been given a similar corresponding inward inclination. To prevent unintended particles from sticking in the filter 2 during transport and handling the device can be provided (see Fig. 2) with pushed-on protective caps, 11, 12 over the apertures, the said hats 11, 12 obviously being removed before sampling and refitted after sampling.

In a further developed variant of the inventive concept the filter 2, the gauze 3 and the electrode device 5 are composed of several units insertable one on top of the other, preferably with a press fit, which have been indicated in Fig. 3 with a) a first electrode 5, first filter 21 and a first gauze 31, b) a second electrode 51, a second filter 22 and a second gauze 32, c) a third electrode 52, a third filter 33 and a third gauze 33 and d) a fourth electrode 53, a fourth electrode 53, a fourth filter 24 and a fourth gauze 34. The said filters 21, 22, 23 and 24 are elaborated to advantage with decreasing particle permeability viewed in the direction of percolation of the device. By this means it is ensured that bacteria, viruses etc. of different particle sizes are collected in different filters. Each unit can therefore be analysed separately in different analysis apparatus in view of the knowledge already existing o the size on known bacteria, viruses etc. In other words the analysis work can be done very rapidly on the basis of a singl sampling.

An example of pollen which can be collected and analysed in the filter with the aid of the device according to the invention is birch pollen with a size of around 30 my and : spruce pollen with a particle size of around 70 4. Examples of viruses are Picorana with a size of around 25 nm and Herpes with a size of 200 nm and examples of bacteria are Stafylokockker Aureus of around 5 a and Mucoplasmas Chlamydiae of around 0.4 a.

To increase the swiftness of analysis to an even greater extent a certain one or more of the said filters 21, 22, 23, 24, the quantity of which can similarly be varied, may also be provided with adapted reagents, which thus directly in conjunction with the sampling are made to be activated and to react with the particles concerned.

To facilitate analysis with an electron microscope the device according to the invention can further be furnished according to Fig. 4 with a plug-in container 13 with an input 14 adapted to a syringe 15, whereby the taken sample to be analysed can be flushed with a suitable liquid, whereby unwanted particles, lumps etc. can be flushed away or cloven, wanted particles can be spread put etc.

For many virus particles science is not currently aware of which antibody is neutralizing, i.e. inactivating. In one embodiment of the method according to the present invention the method can - according to Claim 19, also be utilized to determine whether or not different antibodies aggregate given virus particles to lumps-.

To exemplify the method according to the invention some embodiment examples are described hereinafter. Embodiment example I. Staffylokock protein A is coated on a filter and thereafter a monoclonal antibody, i.e. an antibody which reacts to a single binding point which thus binds to a single antigen and/or a polycronal antibody is added. If this antigen (the specific particle) is present in an analysis liquid or in an analysis gas which is filtered through the filter adapted in size to the specific particle the antigen will be bonded to the antibody which is coated on the filter. Such bonded particles (antigens) can subsequently be demonstrated with the aid of a second directed antibody, appropriately monoclonal, which is radioactively marked with for example I135, whereafter the filter is washed and analysed _: in a gammacounter. Obviously filters with different permeabilities to different particles sizes can be used in the filter unit as above and in particular different monoclonal and/or polyclonal antibodies can be used on the different filters with different permeabilities to different particles to only or essentially react only with the particles which adhere and accumulate on the associated filter.

Embodiment example II. Particles which have been collected and concentrated on one or a plurality of filters after filtration of the analysis liquid or analysis gas with the said particles distributed therein can be further identified with the aid of gold particles coated with protein A, for instance 5-100 nanometer large, to which a monoclonal antibody aimed at a single antigen (particle) has been added. The particles can then be identified when they bind the antibody-protein-A marked gold particle and the tied particles are subsequently visualized in a scanning electron microscope.

Embodiment example III. Instead of gold particles according to embodiment example I, use is made of fluorescein-marked antibodies (FITC) which are added to the .filtered particles. After the filter has been washed it can be read in the fluorescence microscope and antibody-tied particles detected as fluorescent points.

Consequently, in accordance with the method according to the present invention, a specific antibody is added to each filter and secured thereto by suitable means, for instance with the aid of protein A, before the analysis liquid or analysis gas with the particles distributed therein is filtered, or else the analysis liquid or analysis gas is first filtered and thereafter an antibody aimed towards the reagent wanted is added. Detection of this antigen antibody complex can subsequently take place with the aid of, for instance, gold particles, radioactive marking, fluorescence, spectrophotometry etc. '

Embodiment example IV. A collection of, for example, virus particles on a filter or filters is subsequently used to determine which antibodies are neutralizing. For many virus types, for example, science does not currently know which antibody is neutralising, i.e. inactivating. By adding a number of different antibodies to the collected virus particles on th filter or filters it can be seen which antibodies aggregate th virus particles into lumps (i.e. are neutralizing).

Claims

Claims

.1. A device to collect particles carried by gas or liquid in order to facilitate analysis of, the particles, the said device comprising means (1) for generation of percolation of the said gas or liquid through the device and means (2, 3, 4) to collect and retain the said particles, c h a r a c t e r i z e d by a support device (4) which is elaborated essentially as a funnel (7) which is narrowed off viewed in the direction of percolation and which in its first portion, viewed in the direction of percolation, is elaborated with a supporting surface (6) which is arranged to supportingly carry at least one filter (2) collecting and retaining the said particles and by an electrode device (5) which viewed in the direction of percolation is sited before the filter (2).

2. A device according to Claim 1, c h a r a c t e r i z e d i n t h t the supporting surface (6) is shaped essentially circular with a minimum area viewed across the direction of percolation and in that the electrode device (5) has an aperture (8) with a maximum size viewed across the direction of percolation.

3. A device according to Claim 2, c h a r a c t e r i z e d i n t h a t the said aperture (8) has an inclined edge (9) which in the direction of percolation has the same extent as the said funnel (7).

4. A device according to any of the preceding Claims, c h a r a c t e r i z e d i n t h a t between the the

: filter (2) and the supporting surface (6) a gauze (3) or similar means supporting the filter (2) is placed which permits ^• percolation of the said gas or liquid particles.

5. A device according to any of the preceding Claims, c h a r a c t e r i z e d i n t h a t the said filter comprises several filters (21, 22, 23, 24) placed one on top of the other viewed in the direction of percolation and in that the said filters (21, 22, 23, 24) are easily separable from each other.

6. A device according to Claim 5, c h a r a c t e r i z e d i n t h a t each filter (21, 22, 23 and 24 respectively) is supported by an associated gauze (31, 32, 33 and 34 respectively) or similar means.

7. A device according to Claim 6, c h a r a c t e r i z e d i n t h a t each filter (21, 22, 23 and 24 respectively) with its associated gauze (31, 32, 33 and 34 respectively) is elaborated as a push-on easily detachable unit.

8. A device according to any of the preceding Claims 2-7, c h a r a c t e r i z e d i n t h a t the first portion of the aperture (8) and funnel (7) have essentially the same shape and size, in that the filter (2) also has the same shape but is somewhat larger than these and in that, in appropriate cases, the gauze (3) or similar means has essentially the same shape and size as the filter (2).

9. A device according to Claim 7 or Claim 8, c h a r a c t¬ e r i z e d i n t h a t the said electrode device (5) and said units are mutually so adapted that they fit into each other with a press fit and are mutually retained.

10. A device according to any of Claims 5-9, c h a r a c t¬ e r i z e d i n t h a t each filter (for example 22) has a decreased permeability to particles than the immediately preceding filter (for example 2) viewed in the direction of percolation.

11. A method of identifying at least one specific particle or a portion thereof, for example a certain type of virus, of

^• bacteria etc., a plurality of the said specific particles then being distributed or dispersed in an analysis liquid or an analysis gas and being fed through at least a device according to any of the preceding Claims, the said device being provided with a filter, the permeability of which to the analysis liquid or gas is so chosen that the said specific particles are collected on the filter while the analysis liquid or analysis gas otherwise passes through the filter, c h a r a c t e r¬ i z e d i n t h a t at least one antibody aimed at the specific particle, preferably a monoclonal antibody, is added to the said specific particles collected on the filter.

12. A method according to Claim 11, c h a r a c t e r¬ i z e d i n t h a t the said antibody or specific particles bound by means thereof is marked in an appropriate manner and in that the marking is scanned.

13. A method according to Claim 11 or Claim 12, c h a r a c t e r i z e d i n t h a t the antibody is added to the filter prior to percolation through the filter of the analysis liquid or analysis gas.

14. A method according to Claim 11 or Claim 12, c h a r a c t e r i z e d i n t h a t the antibody is added to the filter after percolation through the filter of the analysis liquid or analysis gas.

15. A method according to Claim 11, 12 or 13, c h a r a c t e r i z e d i n t h a t the antibody is bonded to the filter with the aid of staffylokoccos protein A, in that a second antibody, radioactively marked, is bonded to the bound specific particle and in that the radioactive marking is analyzed in a gammacounter.

16. A method according to any of Claims 11-15, with several filters with mutually differing permeabilities to different specific particles placed after one another viewed in the direction of percolation for the analysis liquid or analysis gas through the filters, c h a r a c t e r i z e d i n t h a t added to each filter is at least one associated antibody adapted to the lack of permeability of the filter concerned for a specific particle and appropriately marked, whereby each specific particle is essentially bound in only one of the said filters.

17. A method according to any of the preceding Claims 11-14 or 16, c h a r a c t e r i z e d i n t h a t the antibody is or the antibodies are added to metal particles, for example ^• gold particles, which are coated with protein A, and in that the said metal particles after bonding with the said specific particles are visualized in a scanning electron microscope.

18. A method according to any of the preceding Claims 11-16, c h a r a c t e r i z e d i n t h a t fluorescine-marked antibodies are used and visualized in a fluorescence microscope.

19. A method according to Claim 11 to determine which antibodies are neutralizing for specific particles, i.e. inactivating, c h a r a c t e r i z e d i n t h a t different antibodies are supplied to specific particles accumulated on one or several filters and in that the observation is made whether or not aggregation into lumps takes place.