AU689013B2 - Method and apparatus for treatment of human or animal cell samples - Google Patents

Description

TJlLEi METHOD AND APPARATUS FOR TREATMENT OF HUMAN OR ANIMAL CELL SAMPLES.

The present invention relates to a method and apparatus for treatment of human or animal cell samples. In particular, the invention relates to treatment of the samples to enable diagnosis of clinical conditions. A sample is fixed on a flat surface such as a microscope slide and chemically treated with liquid for the purpose of sample hydration or dehydration, or sample staining, or in chemical analysis such as detection of antigens or nucleic acid sequences, for example. The liquids used to treat such sample include: 1. Organic solvents.

2. Antibodies.

3. DNA and RNA probes.

4. Chemical solutions.

5. Washing solutions.

Conventionally the chemical treatment and the chemical analysis of the samples is done by immersing the glass slides on which the samples are fixed into beakers that contain the treatment solutions. Certain solutions are expensive and they arc dispensed onto a slide using a pipette with the slide in a horizontal orientation and a glass coverslip is placed on top of the slide to provide spread of the solution and to slow evaporation. The conventional process is labour intensive, exposes workers to reagent fumes and possibly to contact with the chemicals. Accurate timing of the processing steps can also be difficult to achieve. The amount of liquid waste generated is often large, which may be a problem, since the waste that needs to be disposed can contain aggressive solvents or biohazards such as infectious viruses. To overcome these problems a number of inventions have been proposed for automating the process.

In US patents 4,731,335 and 4,777,020 and 5,002,736 Brigati, D. et al there is described a system where two flat surfaces such as microscope slides are placed face to face with sample sides facing inward. Abutting coating portions of t slides define a capillary gap between the samples. This slide pair can be placed that the lower edge of the slide pair connects with the treating liquid which wi then migrate into the capillary gap. Liquid can then be removed from the gap placing the slide pair on top of and in contact with absorbent material which wi drain and absorb the liquid.

Shandon Scientific Limited US Patent 4,985,206 describes an apparatus f processing tissue. The core of the invention is a channel-defining element. Th element is joined together with a slide holding the sample with the sample si facing towards the element. The element forms a channel between its main wa and the slide. When the channel is substantially vertical the upper part of t element forms a liquid dispensing reservoir. An operator or a liquid handling rob can then fill the reservoir with appropriate reagent. Gravity and capillary acti will cause the reagent to migrate into the channel. Once the channel is filled wi liquid and the reservoir is empty, the liquid will stay in the gap due to surfa tension of the liquid. The liquid in the gap can be replaced by placing new reage in the reservoir.

Toya, M. et al in US patent 5,068,091 and UK patent 2,265,981 describes substantially horizontal wedge shaped capillary gap between a microscopic slide a lower plateau. Liquids can be dispensed to an exposed end of the plateau a capillary action will cause them to migrate to the wedge shaped gap. The gap c then be cleared of the reagent by using suction. Surface tension of the liquid wi keep the liquid volume together during the removal process.

The aforementioned prior art apparatus all suffer a disadvantage in that they can some instances fail to provide an even treatment of the sample with the treatin liquid. This is caused by air becoming trapped in the capillary gap. In the case the Brigati inventions, capillary forces can only lift the liquid a certain distan upwardly from the lower edge of the slide pair and this can lead to a reduc treatment area on the slide. The speed of liquid removal cannot be controlled in the Brigati inventions. The capillary gap also needs to be drained before a new liquid can be applied. These form a disadvantage, because in certain cases it is desirable that the samples are not exposed to air at all when replacing liquids. This is desirable especially when using volatile liquids such as organic solvents that evaporate easily and may let samples dry out during liquid replacement. Sample drying can lead to reduced processing quality such as high non-specific staining. In other cases a film of liquid should be left on the sample to keep it moist during liquid replacement. In the remaining cases it is desirable that the samples are dried completely before applying a new liquid to ensure maximum concentration of the applied liquid.

The apparatus of Shandon has the additional problem that no provision is made for clearing the gap (filling it with air) between different liquid treatments and therefore any air voids trapped in the gap are likely to remain through the process. Also the apparatus of Shandon cannot provide capability to expose the sample to air during processing while liquids are replaced. In the apparatus of Toya M. et al the suction to clear the capillary gap can lead to a breaking-up of the liquid into two or more sections with only one section being sucked into the waste containment system and such an incomplete clearing of the liquid can cause unacceptable treatment of the sample.

One object of the present invention may be to provide a method and an apparatus for spreading a small volume of liquid on a substantially flat surface supporting a human or animal cell sample, in a controlled manner whilst avoiding or at least reducing the possibility of any air gaps forming in the liquid spread. The range of liquids suitable for the invention include a wide range of viscosities and surface tensions.

Accordingly, the invention provides a method of spreading liquid onto a flat surface supporting a human or animal cell sample on part of the surface, characterised in that, said method comprises: i) placing an element having a flat face adjacent said surface with th flat face parallel with, and in close proximity to, said surface an displaced laterally from said sample, said face being spaced at defined distance from said surface by spacer means between said fac and said surfaces; ii) dispensing said liquid onto said surface or said element, and; iii) after a required amount of liquid is dispensed, moving said eleme relative to said surface, whilst in contact with said surface via sai spacer means, until the flat face of the element covers said sampl whereby said liquid becomes trapped in a cavity between the surfac and the flat face and is spread evenly over said sample.

According to a further form of the invention, there is provided an apparatus f spreading liquid onto a flat surface containing a human or animal cell sample o part of the surface, characterised in that, said apparatus comprises an eleme having a slightly recessed flat face whereby when said element is placed on sai surface with said face parallel to said surface a thin cavity is defined between sai element and said surface, said cavity is accessible along one edge of said eleme and said cavity is of sufficient size to accommodate said sample.

In order that the invention may be more readily understood a particular embodime will now be described with reference to the accompanying drawings wherein:

Fig. 1 shows in three separate views (a), (b) and (c) a perspective a microscopic slide and associated element of the invention i different relative positions and views (b) and (c) include a end stop on the slide;

Fig. 2 is a perspective underside view of the element of Fig. 1 in on particular form; and Fig. 3 is a similar view to Fig. 2 showing an alternative embodime of the element. Referring to Figure 1, there is shown a substantially flat element 1 and a sample carrying microscopic slide 2. The microscopic slide 2 has a sample carrying or supporting surface 3 on which a sample 4 is to be placed and the flat element 1 has a bevelled edge 5 on one end, defining an opening into a recess or cavity 6 (Fig. 2) formed in a face of the element.

In use, after the sample 4 has been placed on the sample carrying surface 3 of the slide, the flat element 1 and the slide are arranged such that a planar base 10 of the recess 6 and the sample carrying surface 3 are generally parallel to each other with the recess 6 and the sample carrying surface 3 generally facing each other, and such that they are laterally offset from each other with the bevelled edge 5 of the element 1 covering an end portion of the slide 2 adjacent a transverse edge 11 (similar to the position shown in Fig. 1(a)). It is preferable, but not essential, that the planar base 10 of the recess 6 and the sample carrying surface 2 are spaced from each other by a distance of about 20 micrometres to 300 micrometres.

The first of a number of treatment liquids (not shown) is then dispensed directly onto the sample 4, or onto the sample carrying surface 3 at a location between the bevelled edge 5 of the element and the sample 4. The element 1 is then moved in a direction towards the sample so that an opening 13 into the recess 6 passes over the sample while the defined distance between the base 10 of the recess 6 and the sample carrying surface 3 is maintained whereby the sample 4 and a major portion of the treatment liquid are trapped within the recess 6.

In some instances, it may be desirable to move the element 1 back and forth on the slide 2 to provide agitation to the liquid before and/or during the incubation process. This agitation can result in a better penetration of the treatment liquid into the sample and thus provide an improved result.

The planar base 10 of the recess 6 is preferably larger than the treated area of the sample 4 carried by the flat surface 3, but smaller than the flat surface itself. It may be preferable to retain a small amount of the treatment liquid on the sampl after the sample has incubated to avoid the sample drying out before the ne treatment liquid is applied.

After the sample incubation period has ended, the excess treatment liquid i removed from the sample carrying surface 3 to enable application of the ne treatment liquid. This can be done at the same time as the element 1 is retracte along the length of the slide to again expose the sample 4.

As the volume defined between the sample carrying surface 3 and the base 1 diminishes during the reverse movement of the element, that is, as the volume o the recess or cavity 6 decreases, the surface tension of the liquid acts to keep th liquid as a single entity. To remove the excess liquid that does not fit into th diminishing volume, a vacuum nozzle 8 is arranged at the transverse edge 11 of th sample carrying surface 3 such that the nozzle 8 faces the recess 6 and is in clos proximity to it. As the element 1 is retracted and moves past the nozzle,the exces treatment liquid is removed from the element 1 by an applied vacuum and is fille into a closed container (not shown) since it could otherwise present a environmental risk. Once the excess liquid for the first treatment has bee removed, a second treatment liquid can be dispensed for subsequent incubation, an the process repeated for further treatment liquids as required.

The relative movement of the element 1 and slide 2 can be automated an controlled by a computer (not shown). Since the mechanism does not form part o the present invention it is not considered necessary to describe it herein other tha to say that in one form a belt driven linear axis driven by a microstepping ste motor is used. Further, this relative movement may be conducted in multipl stages. For example, in the first stage the element may be moved to only partiall cover the surface, then halted for a period of time to allow the treatment liquid t fill the space between the bevelled edge 5 of the element 1 and the transverse edg 11 of the slide to minimize the likelihood of air becoming trapped within the reces 6 on completion of the relative movement. In the second stage, the relative movement may be continued again ensuring that any air originally within the recess has been wholly replaced by the sample 4 and the treatment liquid.

Referring now to Fig. 2 which shows one form of the element 1, the recess comprises a substantially flat surface 10 on the element 1 having three outwardly extending protrusions, or rails 7. The rails 7 are arranged in a general "U-shape" which, with the flat base surface 10 on the element 1, defines a recess which is open at one short edge only. This means that in use the recess virtually fully encloses the sample 4. The reason for the recess substantially enclosing the sample 4 is to reduce the evaporation rate of the liquid when trapped in the recess. This is advantageous during prolonged high temperature incubations requiring several treatment processes.

The rail 7 at the other short end of the recess 6 may have a small opening 12 formed in it to allow air to escape from the recess during the relative movement of the element 1 and the slide 2. Alternatively, the rail at the closed end of the recess

6 may be removed altogether as is shown in the alternative embodiment of Fig. 3.

In a further alternative, other means may be provided on the element 1 or on the slide 2 to maintain the desired spacing therebetween. Such means could, for example, comprise small bosses or protrusions extending outwardly from the face of the element 1 or from the sample carrying flat surface 3 of the slide 2.

In order to further reduce evaporation of the treatment liquid during incubation, an end stop 9 can be clamped, for example, onto the slide 2 to restrict or close the opening to the recess at the bevelled edge 5 of the element 1. The end stop 9 should be positioned such that it engages the end of the element at the bevel when the element has moved to its final incubation position and for this purpose the end stop 9 has a bevelled edge complimentary to the bevelled edge 5 of the element 1. In some instances, it is especially beneficial to the process to add the second further treatment liquids to the recess 6 without exposing the sample to the air. T reason for this is that exposing the sample to the air may lead to drying of t sample which can reduce the quality of the treatment. This is especially so wi some staining procedures.

If air is to be excluded, the current treatment liquid can be replaced by a furth treatment liquid by moving the element 1 slightly so that the recess 6 is just ope to the vacuum nozzle, then applying vacuum while concurrently dispensing t further treatment liquid onto the sample carrying surface 3. In other words only small part of the recess or cavity 6 is exposed. It is preferable, in this case, that t further liquid be dispensed at the opposite end of the element to the vacuum nozzl In practice, the excess of the further treatment liquid tends to migrate to the rece due to the cohesive forces of the liquid while the liquid is under vacuum and wi be captured by the vacuum nozzle. The migration of the liquid substantially sto once the excess treatment liquid at the dispensing end is used up.

This process can be facilitated by orienting the whole arrangement at an angl preferably about 5°, with the vacuum nozzle being at the lower end of the surfa and the dispensing of further liquid being at the upper end of the surface.

It is preferable that the element 1 has a thickness which is sufficient to preve treatment liquids dispensed onto the sample 4 flowing over the top of the eleme during the relative movement. Typically, this thickness will be more than 2m In addition, the bevelled edge 5 can be angled at various different angles relati to the plane of the surface 3 to allow the element to rise above any obstacles on t slide, for example wax granules on a paraffin fixed sample.

It is preferable that the element 1 be formed of a chemically inert material, so th it does not affect the treatment reactions, and that it be manufactured of a materi that withstands organic solvents to allow, for example, dewaxing and dehydratio procedures to be conducted on the sample. It is also desirable that the element be manufactured of a transparent or translucent material to enable a user to observe the reaction taking place in the sample. To satisfy all of these requirement the element is preferably formed of glass, and the rails or protrusions are printed or painted onto the element using an inert and durable material such as a Fluoro Ethylene Polymer. Alternatively, the rails may also be formed of glass using various manufacturing processes such as grinding or etching.

If the sample carrying surface is a microscope slide the vacuum nozzle can be placed at the end of the slide that is closest to the sample area. This end is typically opposite to a frosted end 14 of the slide. In a preferred form, the opening of vacuum nozzle can be in the form of slit which may be substantially the same width as that of the microscope slide and it can be aligned such that the slit length is parallel to the face of the microscope slide.

Claims (17)

C_LAJL S:

1. A method of spreading liquid onto a flat surface supporting a human animal cell sample on part of the surface characterised in that said metho comprises: i) placing an element having a flat face adjacent said surface with t flat face parallel with, and in close proximity to, said surface, an displaced laterally from said sample, said face being spaced at defined distance from said surface by space means between said fa and said surface; ii) dispensing said liquid onto said surface or said element, and; iii) after a required amount of liquid is dispensed, moving said eleme relative to said surface, whilst in contact with said surface via sai spacer means, until the flat face of the element covers said sampl whereby said liquid becomes trapped in a cavity between the surfa and the flat face, and is spread evenly over said sample.

2. A method according to claim 1 including the further step of removing exce liquid after suitable incubation of the sample, characterised in that, said metho further includes moving said element, relative to said surface, in a direction awa from said sample whilst maintaining said contact with said surface and, as sai cavity moves over an edge of said surface, applying a vacuum at said edge t remove said excess liquid which is held in said cavity by surface tension of t liquid.

3. A method according to claim 2, wherein a further treatment liquid is applie to said sample to replace the first liquid without exposing said sample to ai characterised in that, said step of moving said element in a direction away fro said sample involves moving said element only sufficiently to expose a small pa of said cavity to said vacuum, and said method further includes applying sai further treatment liquid concurrently with the application of said vacuum, sai further liquid being applied adjacent the opposite end of said element to the end at which said vacuum is applied.

4. A method according to claim 3, characterised in that, said surface and element are inclined at a slight angle to the horizontal and said vacuum is applied to the lower end of said surface.

5. A method according to any one of the preceding claims, characterised in that, said element is moved back and forth on said surface to provide agitation to the liquid before and/or during an incubation process.

6. A method according to any one of the preceding claims, characterised in that, said step of dispensing liquid onto said surface or said element comprises dispensing said liquid onto said surface adjacent an opening to said cavity.

7. Apparatus for spreading liquid onto a flat surface supporting a human or animal cell sample on part of the surface, characterised in that, said apparatus comprises an element having a slightly recessed flat face whereby when said element is placed on said surface with said face parallel to said surface a thin cavity is defined between said element and said surface, said cavity is accessible along one edge of said element and said cavity is of sufficient size to accommodate said sample.

8. Apparatus according to claim 7, characterised in that, said cavity is defined by said flat surface, said flat face parallel to said surface, and raised rails on said flat surface, said raised rails extending generally along two parallel edges of said element, one of the remaining edges not having a rail and being said one edge which provides access to said cavity.

9. Apparatus according to claim 8, wherein said flat surface is on a microscopic slide, characterised in that, said apparatus further includes a vacuum nozzle arranged below and adjacent an edge of said slide.

10. Apparatus according to claim 9, characterised in that, said one edge is bevelled edge which forms an acute angle with said surface when said element i placed on said surface.

11. Apparatus according to claim 10, characterised in that it further includes a end stop for clamping onto said slide, said end stop engaging said one edge of sai element when said element is in a final incubation position on said slide, said en stop having a bevelled edge complimentary to said bevelled edge on said elemen for closing access along said one edge in said final position of said element.

12. Apparatus according to any one of claims 9 to 11 inclusive, characterised i that, relative movement of said element and slide is automated and controlled b a computer.

13. Apparatus according to claim 12, characterised in that, said relativ movement is conducted in stages whereby in a first stage the element is move from a position wherein the bevelled edge of the element is adjacent an end portio of the slide, to a position wherein the element partially covers said surface, an remains in position for a period of time sufficient to allow treatment liquid, place on said surface prior to said first stage, to fill the space between the bevelled edg of the element and said end portion of the slide, and in a second stage the elemen is moved further over the slide such that the sample is contained within said cavit and any air originally contained within said cavity is wholly replaced by sai sample and said treatment liquid.

14. Apparatus according to claim 13, characterised in that, said slide and elemen are inclined at a slight angle to the horizontal and said vacuum nozzle is at th lower edge of said slide.

15. Apparatus according to claim 14, characterised in that, said automated and controlled relative movement between said slide and element is adapted to move the element back and forth on the slide to provide agitation to the liquid before and/or during the incubation process.

16. An apparatus according to claim 15, characterised in that, said element including said rails is formed of glass and the height of said rails above said flat face is between 20 and 150 micrometres.

17. An apparatus according to claim 15, characterised in that, said element is formed of glass with the exception of said rails which are printed or painted thereon using an inert and durable material and the height of said rails above said flat face is between 20 and 300 micrometres.