GB2393670A

GB2393670A - Burette with hollow dispensing shaft on plunger

Info

Publication number: GB2393670A
Application number: GB0222802A
Authority: GB
Inventors: Dykes Hugh Ballantine; Martin Alan Lee; Michael Edward Best; Brian Thomas Croft; Martin Phillip Roberts-Jones
Original assignee: UK Secretary of State for Defence
Current assignee: UK Secretary of State for Defence
Priority date: 2002-10-02
Filing date: 2002-10-02
Publication date: 2004-04-07
Also published as: GB0222802D0

Abstract

A burette or means suitable for dispensing a predetermined volume of a sample solution 20 comprises a plunger 4 with a hollow shaft 8 and a means suitable for limiting depression of the plunger 4. The limiting means may be provided by a collar 18, abutting against the top of a sample collection vessel 24 during dosing. The plunger 4 may comprise a piston 4 with an aperture 10 in a piston face 6. The device may be provided in kit form. An associated method of use may comprise the engagement of the shaft 8 in a push fit seal 22 of the sample collection vessel 24. The device as a whole may be pressed downwards, and thus the plunger moves upwards relatively, as indicated by the arrow in fig.2, into the burette, creating internal pressure to dispense the solution 20 though the hollow shaft 8 into the collection vessel 24. The limiting means as already described may ensure a correct desired dosing amount.

Description

7'S?U:o Sampling Device This invention relates to a device for accurately

isolating a known volume of a sample solution, preferably a sample solution comprising nucleic acid material. More particularly this invention relates to a device and associated method for use m a clinical environment in conjunction with standard equipment in conjunction with a standard chnical sample vessel for isolating a known volume of a sample solution for example a urine sample.

Identification of biological material including micro-organisms such as bacteria and viruses, and other genetic material and nucleic acids, is currently an area of important development because it allows for, among other things, the diagnosis of disease states.

Rapid and accurate diagnosis of diseases has important social and economic consequences. These include that the correct treatment can be quickly administered to a patient increasing the hkelihood of success, reducing patient anxiety, and reducing the risk of the spread of infection. Although there are many examples of disease states where it would be useful to quickly and rapidly positively identify infection, one particular example Is the identification of the bacterial sexually transmitted disease (STY) Chlamvdia trachomatis. Diagnosis ofthis STD is a current focus of health care professionals gkbally since, m the USA alone, it Is the most prevalent transmitted STn resulting In more than 4 million new cases each year and also because, if left untreated m female patients, it can lead to to costly sequelae such as pelvic inflammatory disease, ectopc pregnancy and, ultimately, to infertility.

1'' One of the best known techniques for the identification of genetic material and nucleic acids is to first replicate the material, thereby generating sufficient material for positive identification. The polymerasc chain reaction (PCR) is a commonly used method for replicating such material that has several advantages including that it is sensitive and selective. This means that is can be used to accurately identify a wide range of different nucleic acid targets from only a small initial sample. Such a method is ideal for use to positively Identify nucleic acids m a wide variety of different biological samples. However, when trying to expand the use of PCR for general day to day rapid diagnosis, there are several problems to consider. These include that prior to the PCR amphfication the sample needs to be purified and concentrated using complex techniques and sometimes hazardous reagents, which to date is conducted only in specialist laboratories. This results in a slow, resource intensive and expensive process which is also subject to possible sample cross contamination. There remains a need to develop a means whereby in a non-laboratory environment, a nucleic acid target can be isolated from a sample solution for subsequent replication by PCR in order to improve response times, to free skilled labour from repetitive tasks and to reduce costs.

The first step in purifying a nucleic acid target from a sample for subsequent replication by PCR, is to obtain an accurately dispensed predetermined known volume of a sample solution comprising the target material. When considering the development of a means for use outside of the laboratory environment, there are several problems associated even with this first apparently simple step. These include that accurate measurement of a known volume of a sample solution requires the use of additional equipment including pipettes or measuring cylinders which are non

standard outside of a laboratory and the use of which requires special traimng, transfer of the sample from one piece of equipment to another can lead to sample cross contamination and may also lead to contamination and infection of the user, and that If the sample solution volume is not measured sufficiently accurately the level of nucleic acids material obtained may be so low as to result in a false negative result.

There is a need to develop a device whereby an operator with little or no laboratory training, for example a health care practitioner, can easily and accurately measure a pre-determined known volume of a sample solution without risk of self-infection.

Such a device should have sufficient consistency In delivery of the predetermined volume of material to prevent the failure of any later PCR assay. In addition it should be able to be produced In a cost-effective manner and to be disposable such that different samples can be measured rapidly without the possibility of cross contamination or the need to sterilise large amounts of equipment. Furthermore it is preferred that such a measuring device can be used m conjunction with standard clinical equipment m order to mimmise additional costs.

A device has now been developed which addresses the above problems. The device comprises a plunger, a conduit passing through the plunger, and a means for limiting the depression of the plunger. The device is used m conjunction with a standard sample vessel into which is placed the sample solution, for example a urine solution comprising a nucleic acid target. The device is then integrated with the sample vessel.

I'he plunger is then depressed and as it passes through the sample vessel, the sample solution is displaced through the conduit. As the plunger Is displaced further, additional sample solution is displaced through the conduit. 'I'he displaced sample

solution is collected in a collection vessel. Ely using a means to limit the depression of the plunger, it is possible to pre-determine and accurately control the volume of sample solution that Is displaced and dispensed. The device can be further Improved m several ways, for example by utilising a plunger with a hollow shaft which is abic to act as the conduit, by adapting the conduit such that it is able to integrate with a collection vessel to prevent spillage and risk of infection of the user, and by providing an attachment means, adapted to integrate with the sample vessel in question. The operation of the device is still further improved by, prior to depression of the plunger, inverting the sample vessel. This means that if the sample vessel is not completely filled with the sample solution, then any air remaining in the sample vessel moves away from the plunger and on depression the plunger passes directly through the sample solution. As such the volume of solution passing through the conduit remams consistent regardless of the volume of sample solution in the sample vessel itself.

This device has several advantages. These include that it can be used with standard vessels In a non-laboratory environment to obtain an accurately dspcnscd pre-

determmed volume of a sample solution. Furthermore the device has sufficecnt accuracy so that the volume of sample solution obtained Is highly consistent. This results in a reduced margin of error in any subsequent sample manipulation, for example PCR, thus improving the success of the overall diagnostic techmque. Other advantages include that since the device is adapted for use m conjunction with standard sample vessels readily available in a clinical environment there is a reduced need to purchase additional cqupmcnt, the device Is simple and cheap to manufacture, it Is disposable' end it can be readily used by personnel with little or no practical laboratory training.

It is an object of the present invention to design a device to enable the accurate solathn of a pre-determined volume of a sample solution, optionally comprising a genetic or nucleic acid target material. It is further object of this invention that such a device is easy to use in a non-laboratory environment, such as a chnic, by a user with tattle or no scientific training whilst simultaneously reducing any chance of user enforced error and cross contamination of samples. It is another object of this invention to design such a device such that it can be used with standard laboratory vessels to reduce the need for additional equipment and also to reduce the cost.

These, and other objects of this invention, will become apparent in light of the following disclosure.

Summary of the Invention

According to a first aspect this mventon relates to a device for the accurate isolation of a predetermined volume of a sample solution comprising a plunger, a conduit passing through the plunger, and a means for limiting the depression of the plunger.

According to a second aspect this invention relates to a kit comprising: (i) a device according to the present invention; and (ii) a sample vessel.

According to a third aspect this invention relates to a method of isolating a known volume of sample solution comprising: (I) collecting the sample solution in a sample vessel;

(ii) integrating a device according to Claim I with the sample vessel; I

(iii) depressing the plunger to displace the sample solution; and (iv) collecting the displaced volume of sample solution in a collection vessel. Detailed Descrintion of the Invention All pubhcations cited herein are hereby incorporated by reference m their entirety, unless otherwise indicated.

The elements of the device are described In more detail below.

This invention relates to a device for the accurate isolation of a predetermined volume of a sample solution comprising a plunger, a conduit passing through the plunger, and a means tor limiting the depression of the plunger. During operation the device is used in conjunction with a sample vessel in which the unknown quantity of sample solution Is placed.

The device of the present invention comprises a plunger with a conduit passmg through the plunger. It Is preferred that the plunger comprise a piston with an apcrturc, preferably centred m the piston, and a hollow shaft which Is not sealed. The conduit passmg through the pEmgcr communicates the underside of the piston with the upper side of the piston via the aperture thus providing a path whereby fluid in a sample vessel can be transferred to the outside of the vessel. There are several means of providing such a conduit but it Is Important that the conduit Is firmly integrated with the pEmgcr such that sample solution is able to pass through the plunger without

any leaks. One potential conduit is to provide a tube that is attached to an aperture that passes through the piston. However, in order to keep the apparatus as simple as possible, it is preferred that the conduit passing through the plunger is provided by the communication of the hollow shaft with the aperture in the piston. This allows the plunger and the conduit to be manufacture readily as a single integrated unit with reduced costs. Thus, when m use, and on depression of the plunger, the sample solution Prom the sample vessel, can pass through the hollow shat't and out into a collection vessel.

Depending on the design of the device, which in turn depends on the design of the sample vessel with which it is intended to use the device, the plunger can have many different shapes and sizes. It is preferred that the piston comprises a disc that is shaped to fit the inner dimensions of the sample vessel. It is preferred that the hollow shaft Is also cylindrical, with a uniform diameter that is sufficiently large to enable the ready transfer of sampic solution from the sample vessel to the collection vessel. The hollow shaft may have a variety of different lengths, although its length must necessarily be sufficient to allow the plunger to be depressed to displace the full volume of sample desired. In the envisaged use of the present invention t dispense I (hell of sample solution, it is intended that the hollow tube has an internal diameter of from about (). Imm to about Smm, preferably from about ().Smm to about 2mm and has a length of from about Smm to about 100mm, preferably from about 20mm to about 40mm.

A second role of the conduit is not only to transfer the sample solution through the plunger but also to Ideally then transfer the sample solution directly to a collection

vessel. It is therefore preferred If the conduit, and therefore preferably the hollow shaft of the plunger, Is adapted to Integrate with a collection vessel. This allows the sample solution to pass into the collection vessel with minimal leaks, and preferably without any leaks. This has several advantages reducing the likelihood of sample contamination and also reduchig the sample handling and hkelillood of user contamination and infection. 'lathe device could integrate to the collection vessel in several ways Including by a quick tat seal, a screw seal, a simple push fit seal into a unit designed to receive the conduit or other means. If the device of the present invention is moulded from plastic then such integration means can be integrated easily into the device design, particularly into the design of the end of the hollow shat't. This integration will further simplify the use of the device in the chnic for staff with tattle ... Or no scientific training.

It Is preferred that the plunger of the present invention also comprises a means for achieving a seal. This means allows the plunger to form a seal with the internal walls of the sample vessel with the result that when force Is applied to the plunger, sample solution in the sample vessel does not leak around the edges of the plunger but instead is displaced through the aperture in the plunger into the hollow tube. An example of a suitable means for providing a seal could be one or more simple ''O" rings that are made either of rubber, elastic plastic, silicone or a mixture of more than one of these materials attached to the plunger. Another example okra suitable means for providing a seal could be a downwardly extending skirt. Alternatively it Is possible that the plunger is designed to be self sealing with the inner walls of the container.

The device of the present invention also optionally comprises an attachment means for attaching the device to a standard sample vessel. Many such attachment means can be envisaged depending on the use of the apparatus and the standard sample vessel that the device Is to be used with. It is preferred that the attachment means is designed such that it can be easily attached, removed, replaced, loosened or tightened.

It addition it is preferred that the attachment means is sealed such that during use the sample solution does not leak from the apparatus. It is also preferred that the attachment means is adapted to integrate with the sample vessel. In order to dispense the sample solution to a collection vessel, it may also be necessary, depending on the design of the device, for the conduit to pass through the attachment means. One of ordinary skill in the art would be able to determine this when designing the apparatus.

As such it is preferred that the hollow shaft of the plunger is able to pass through the attachment means but m manner whereby the hollow shaft is itself able to slide up and down within the attachment means such that the plunger can be depressed. It is preferred that the attachment means comprises a simple means to hold the plunger in place prior to use of the device tor example a cone. This prevents the plunger moving during storage, makes it eascr to attach the device to the sample vessel and prevents the sample solution leaking out of the sample vessel If the sample vessel is inverted Such a means should have sufficient strength to hold the plunger firm pre-use however, it should be readily released such that it does not prevent the plunger being depressed during use.

I'he preferred attachment means for the device of the present invention Is a screw cap.

It Is funkier preferred that the attachment means is manufactured from a moulded resiliently deformable plastics material. 'I'his is because such material can be easily

and cheaply manufactured and is disposable. Preferably the apparatus is formed of a thermoplastic material such as polyethylene or polypropylene or butadiene-styrene copolymer or mixtures thereof. Furthermore it is preferred that the apparatus is manut'actured usmg injection moulding techniques. Similarly it is preferred if the plunger is manut'actured from similar materials.

The device of the present invention also comprises a means for limiting the depression of the plunger. The means for limiting the depression of the plunger is Important since this determines the volume of sample solution that is dispensed through the conduit when the device is used. If the plunger is depressed too far then an excess of sample solution will be dispensed and conversely if the plunger is not depressed far enough then insufficient sample solution will be dispensed. The volume of sample solution to be dispensed will be known in advance. During manut'acture the limiting means will be designed and positioned in order to achieve this volume.

The position of the Smiting means will be dependent on the length of the hollow shaft, the internal diameter of the hollow shaft, and diameter of the piston and the diameter of the aperture in the piston. The exact positioning of this means can be readily determined by one of ordinary skill in the art. Again, depending on the design and use of' the apparatus many different limiting means can be envisaged. These hiclule the use of a collar on the shaft of the plunger that limits the depression of the plunger for example by preventing further depression of the plunger through the opening in the sample vessel, or by preventing further depression through any optional attachment means. If the device comprises an attachment means, it is preferred that the means for limiting the depression of the plunger is a collar extending t'rom the means for attaching the device to a standard sample vessel. This . At)

Is able to limit the depression of the plunger, either by coming mto contact with a collection vessel or coming into contact with an extended head on the shaft of the plunger. To simplify manufacture and costs the attachment means and associated collar should be manufactured as a single integrated unit. For the present intended use to dispense approximately lOml of sample solution from a sample vessel with approximate volume of 30ml, it is preferred that the collar has a height of from about 5mm to about 2()mm, preferably of from about I Omm to about 1 5mm.

It is also important that the device be designed such that it operates with consistent level of accuracy. It is preferred that the device has an operational error of less than about 10%. preferably less than about 5 /0 and more preferably less than about 1% of the isolation volume.

The device may optionally comprise a filter membrane to remove any unwanted particular matter from the sample prior to further processing. Such a means could either be located on the surface of the plunger or within the hollow tube. For use in a cinncal environment with urine samples it is useful to use a filter with a mesh size of m the region of about 500pm, however in different environments many other filter mesh sizes may be appropriate.

The collection vessel itself may have t'urther functionality. An example is that the collection vessel may be a purification apparatus. In the case of isolation of a known volume of sample for subsequent PCR reaction the sample should be sequentially washed and concentrated with a concentration device such as silica or glass fibre filters ready for replication using PCR. In this instance it Is particularly important that 1 1

the purification device is able to integrate effectively with the hollow tube such that none of the sample solution is lost as it Is transferred from sample vessel to the purification apparatus.

Each element of the device of the present invention can optionally be colour coded to enable easier instruction and use by a person with little or no scientific training.

The present invention also relates to a kit comprising: (i) a device according to the present invention; and (ii) a sample vessel.

The sample vessel may have a variety of different shapes and sizes and will depend on the specific desired use. However, when used to collect and isolate a predetermined volume of sample solution comprising a nucleic acid target material it is preferred that the sample vessel has a volume of from about Hell to about 5()()ml, preferably of from about lOml to about lOOml and more preferably of from about 2()ml to about 70ml. When the device comprises a means for attaching the device to the sample vessel and this means is adapted to integrate with the given sample vessel.

It Is preferred that the sample vessel has a screw cap attachment and the means for attachhg the device to the sample vessel is a screw cap which allows for easy attachment and removal of the device of the present invention to the sample vessel. It is preferred that the sample vessel is manufactured from plastic such that it its cheap and disposable after use. It can be transparent or translucent and can optionally be marked with graduations to indicate when the correct level of sample has been collected. It Is preferred if the sample vessel has a screw attachment such that the

device of the present invention can be attached using a screw means. An example of a suitable sample vessel is the 3()ml polystyrene universal sample vessel and cap supphed by Libby Sterlin_. It Is useful if the sample vessel has its own sealing means such that after the sample solution has been dispensed, the device can be removed and the sample vessel sealed to prevent spillage and contamination. If necessary the sample could then be stored for future use.

According to another aspect this invention relates to a method of Isolating a known volume of sample solution comprising: (i) collecting the sample solution in a sample vessel; (ii) integrating a device according to the present invention with the sample vessel; (iii) depressing the plunger to displace the sample solution; and (iv) collecting the displaced volume of sample solution m a collection vessel. This method allows the user to collect an unknown volume of a sample solution comprising a target material into a sample vessel and to accurately Isolate a pre-

determined volume of the sample mto a collection vessel by depression of the plunger and the subsequent displacement of the sample solution. This method can be used to collect any one of a wide variety of liquid samplemcluding solutions. In the instance where the sample comprises a nucleic acid target material, examples of such liquid samples may Include a patient urine sample, or a sample of water taken from the environment. Ideally the sample is collected directly mto the sample vessel which obviates the need for the use of any further equipment. If taking a patient urine

( sample, it may be necessary to attach a urine cone to the sample vessel to make it easier to collect the sample. Such cones can be designed to fit securely mto the sample vessel so that no sample is lost due to leakage. Alternatively if the sample is not a liquid or a solution, or if't Is very viscous, for example a swab sample or a blood sample, the sample can be placed into the sample vessel, a solvent can be added to dissolve the sample, and then an accurate volume of the dissolved sample can be Isolated using the device and method of the present invention.

It Is preferred that the method has an added step that, after the device according to the present invention has been integrated with the sample vessel, the sampic vessel is inverted prior to depression of the plunger. The inversion of the sample vessel means that any air present in the sample vessel moves away from the plunger. As such, when the plunger Is depressed, it passes directly through the sample solution thus ensnaring that the correct volume of sample solution is displaced without first displacing air. If the sample vessel Is not full of sample solution then failure to invert the sample vessel prior to depression of the plunger would result in the plunger first passmg through the air m the sample vessel and result in an incorrect and inconsistent volume of sample solution would be displaced. This preferred use of the device highlights the importance of a secure seal on the plunger, or a secure attachment means on the device such that on inversion no sample solut'<-,n is able to leak from the sample vessel. If such a method is used it is also preferred that the conduit Is attached to a sealed collection vessel prior to inversion of the device and sample vessel. This has the result of forming a sealed system comprising the sample vessel, the device of the present invention and the collection vessel and as a result no sample is able to leak prom the sample vessel into the collection vessel prior to depression of the plunger. If

( such a system is used it is preferred that the sample vessel and the collection vessel are moved slowly towards each other, thus depressing the plunger and dispensing the sample solution. For example, when the collection vessel comes into contact with the collar of the attachment means, no further depression of the plunger will be possible.

Figures Phis invention will now be described by reference to the following drawings m which: Figure I shows a cross sectional view of a device of the present invention attached to a sample vessel which is partially filled with sample solution; and Figure 2 shows a cross sectional view of a device of the present invention when In operation attached to an inverted sample vessel and a collection vessel.

Figure I shows a cross sectional view of a device of the present invention 2 comprishig a plunger 4, which in turn comprises a piston 6, a shaft 8, an aperture in the piston 10, and a plunger sealing means 12. The device is attached to a sample vessel 14 by way of an attachment means 16. The attachment means 16 also comprises a collar 18 that extends away from the attachment means 16. The sample vessel 14 is partially filled with sample solution 20.

Figure 2 shows a cross sectional view of a device of the present invention 2, attached via an attachment means 16, to an inverted sample vessel 14 and attached via the plunger shaft 8 and a push fit seal 22 to a collection vessel 24. The sample vessel is partially filled with sample solution 2(). The presence of the plunger seal 12 and the attachment means 16 prevent sample solution 2() leaking from the sample vessel. In

( order to operate the device the plunger 4 Is depressed in the direction shown. The sample solution 20 m communication with the piston 6 is displaced through the aperture 1() and into the hollow shaft 8. It then passes into the collection vessel 24 where a known aliquot of sample solution Is collected 26. Since the collection vessel 24 is attached to the plunger 4 via the push connection 22, as the plunger 4 Is depressed in the direction shown the collection vessel 24 and the sample vessel 14 move towards each other. When the collection vessel 24 meets the collar IX, the plunger 4 can be depressed no further. As such no further sample solution 20 is displaced from the sample vessel. The collection vessel 24, containing the accurately measured sample aliquot 26, Is disconnected from the plunger 4 and sealed. The remainder of the sample solution can then either be stored or disposed.

Claims

( CLAIMS

1. A device for the accurate isolation of a predetermined volume of a sample solution comprising a plunger, a conduit passing through the plunger, and a means for hmitmg the depression of the plunger.

2. A device according to Claim I wherem the plunger comprises a piston and a shaft and wherein the piston comprises an aperture.

3. A device according to Claim 2 wherem the aperture is centrcd m the piston.

4. A device according to any of Claims 2 to 3 wherein the shaft is hollow and is in communication with the aperture in the piston.

5. A device according to ('lahn 4 wherein the conduit passing through the plunger Is provided by the communication of the hollow shaft with the apcrturc.

6. A device according to Claim 5 wherem the hollow shaft of the plunger is adapted to mtegratc with a collection vessel.

7. A device according to any of Claims I to wherem the plunger comprises a means for achieving a seal with the sample vessel.

8. A device according to Claim 7 wherein the means for achievhg a seal with the sample vessel is a simple '60" ring manufactured from rubber, elastic plastic, shcone or a mixture of more than one of these materials.

( 9. A device according to any of Claims I to wherein the device additionally comprises an attachment means for attaching the device to a standard sample vessel. I (). A device according to Claim 9 wherein the means for attaching the device to a standard sample vessel is a screw cap.

I 1. A device according to any of Claims 9 to 10 wherein the conduit passing through the plunger also passes through the attachment means.

12. A device according to any of Claims 9 to I I wherein the means for limiting the depression of the plunger is a collar extending from the means for attaching the device to a standard sample vessel.

I.3 A device according to any ot Claims I to 12 wherein the plunger comprises a filter membrane.

14. A kit comprising: (i) a device according to Claim 1; and (ii) a sample vessel.

15. A kit according to Claim 14 wherein the device comprises a means for attaching the device to the sample vessel and this means is adapted to integrate with the given sample vessel.

l 16. A kit according to Claim 15 wherein the sample vessel has a screw cap attachment and the means for attaching the device to the sample vessel Is a screw cap.

17. A method of Isolating a known volume of sample solution comprising: (i) collecting the sample solution in a sample vessel; (i') mtegratmg a device according to Claim I with the sample vessel; (iris depressing the plunger to displace the sample solution; and (iv) collecting the displaced volume of sample solution in a collection vessel. 18. A method according to Claim 17 wherein after the device according to Claim I has been integrated with the sample vessel, the sample vessel is inverted prior to depression of the plunger.