INDIVIDUAL SEPTUM CAPPED MICROTUBE AND METHOD

Abstract: A method of preparing a sample including providing a microtube (1), closing the microtube (1) with a self-sealing septum cap (2) and injecting a liquid sample through the septum cap using a hollow needle. The method may be performed using automated or robotic laboratory equipment.

Description: INDIVIDUAL SEPTUM CAPPED MICROTUBE AND METHOD The present invention relates to the preparation and storage of compounds and particularly although not exclusively to the preparation and storage of solubilised compounds used in the pharmaceutical and agrochemical industries. Research into new pharmaceuticals, often termed "drug discovery " , involves the preparation, storage and analysis of large numbers of compounds . The compounds may also be mixed and matched in an attempt to identify pharmacologically active compounds. This so called high throughput screening is carried out as far as is practicable using robotic equipment. In an existing arrangement compounds under test are stored in microtubes which, in turn, are mounted in blocks. One current industry standard block has a footprint of 1 27.5mm by 85.5 mm and accommodates 96 microtubes on a 9mm pitch. It is desirable to make microtubes as small as possible. This increases the number of different compounds that can be tested and enables less solvent to be used per microtube which leads to a significant cost saving. Microtubes may either be stored open ended or sealed. At present microtubes are sealed using plastic mats or strips of joined plastic caps that can be pressed into the open end of microtubes. The existing method of sealing microtubes has a number of disadvantages. To allow for the individual handling of microtubes it is necessary for the mat or strip of caps to be cut, this is inconvenient. Also, when a mat is removed to allow access to the microtubes a new mat must be used when it is desired to re-seal these tubes. Again, this is inconvenient and also leads to increased costs. Further, by far the greatest disadvantage with existing methods of microtube sealing and handling is that the contents of a sealed microtube cannot be accessed without some manual intervention . The contents of a sealed microtube cannot be accessed without removal of the cap and the cap cannot be removed and replaced using automated laboratory equipment. Cap removal and replacement must therefore be carried out by laboratory staff. This method is tedious, costly in terms of labour, and increases the possibility of error. It is an object of the present invention to provide an alternative method of preparing compound samples in microtubes and an alternative sealing arrangement which addresses and overcomes or at least mitigates some or all of the abovementioned problems. According to a first aspect of the present invention there is provided a method of preparing a sample comprising the steps of:- providing a microtube having an opening therein; providing a self sealing pierceable closure for said microtube; inserting said closure member into the opening of said microtube to seal the microtube; inserting a hollow needle through said closure into said microtube; injecting a liquid into said microtube through said hollow needle; withdrawing said hollow needle from said closure member, to allow said closure member to seal said microtube. The microtube is preferably a standard microtube suitable for handling with automated laboratory equipment. The above method is particularly suited for the preparation of a liquid sample for storage under environmentally controlled conditions for example under freezing conditions or stored under an inert gas. The closure may be fitted to the microtube manually, or preferably by using automated equipment possibly including robotic equipment. The closure preferably comprises a septum cap, insertable at the open end of the microtube. The cap is preferably produced from a self-sealing material which is pierceable by a hollow needle and on withdrawal of the needle re-seals the microtube. The closure preferably provides a sufficient seal after being pierced at least 50 and more preferably at least 1 00 times. The closure may be produced from a silicone based material. The closure preferably provides sufficient integrity for the long term storage of compounds even after repeated access has been made to the contents of the microtube through the closure. The liquid sample may be a solution, the solvent of which may comprise DMSO (Dimethyl Sulfoxide). The hollow needle preferably includes two unconnected conduits for fluid, to allow a liquid to be injected into or withdrawn from the microtube and for the air or gas inside the microtube displaced by the liquid to escape through the needle or likewise to allow air or gas to flow into the microtube to fill space vacated by a liquid. The needle is preferably of coaxial construction . Alternatively the closure member may be pierced by more than one hollow needle simultaneously, to achieve a similar effect. The method of preparing a sample may include the further step of injecting an inert gas into the microtube to enable a sample to be prepared and stored under an inert gas. Typically a liquid sample would be injected into the microtube, the air in the microtube being displaced through the second conduit through the coaxial needle. When the desired amount of liquid has been injected then a quantity of inert gas is injected into the liquid sample to displace any remaining air. The needle may then be withdrawn leaving a sample stored under an inert gas. Alternatively an inert gas may be injected before the liquid sample. The microtube is preferably stored in a block. Preferably the method involves the simultaneous preparation of a plurality of samples. The method preferably includes the further step of marking the microtube to identify the sample. The marking is preferably machine readable and is usefully in the form of a two-dimensional dot code, applied to the microtube using an ink type jet print head. The method may also include the step of using a hollow needle to remove a liquid sample from a microtube. Where a sample is stored under an inert gas and a quantity of the sample is removed from the microtube, it is preferable that additional inert gas is injected into the microtube to fill the space vacated by the liquid sample. The method of the present invention is particularly suitable for use with automated stores, and for the preparation of samples for storage in automated stores, possibly under refrigerated conditions. In one embodiment the method includes additional steps for the preparation of a liquid for injection into the microtube, including any or all of the following steps:- i) placing a dry compound into a vial; ii) placing a solvent into said vial; iii) closing said vial using a pierceable closure; iv) agitating said vial to aid dissolution of the dry compound; v) passing a hollow needle through said closure into the vial and extracting the liquid therein through said needle. The solvent preferably comprises DMSO (Dimethyl Sulfoxide) . The vial is preferably of greater internal volume than a microtube. The liquid prepared in the vial may then be injected into microtubes. The pierceable closure member preferably comprises a septum cap. Providing a sample in a microtube with a septum cap, by the above method coveys numerous advantages. Particularly, the operation of filling the microtube with a sample and subsequently removing the sample may be carried out using automated laboratory equipment, precluding the need for the tedious manual removal and replacement of caps and associated waste produced when gaining access to the contents of existing microtube arrangements. Also, as the septum caps are separate, each microtube remains individually removable from the block. Large numbers of microtubes may be conveniently prefilled with suitable reagents for subsequent experimentation and analysis. The tubes may be prepared using automated equipment, reducing the cost of labour associated with existing methods. The filling of microtubes using hollow needles enables smaller microtubes to be employed, again reducing costs. According to a second aspect of the present invention there is provided a microtube assembly comprising a microtube and a self-sealing pierceable closure for use in the above described method of providing a sample. The microtube is preferably a conventional microtube and may, for example, be constructed from glass or a plastics material. The closure is preferably inserted into the open end of the microtube. The assembly enables a microtube to be filled with a desired liquid compound using automated laboratory equipment, preferably by the use of a coaxial hollow needle. Subsequently various analysis and mixing of the samples may also be performed by automated laboratory equipment, gaining access to the contents of the microtubes through the closure. In order that the invention may be more clearly understood there are now described embodiments thereof, by way of example and with reference to the accompanying drawings in which:- Figure 1 shows an exploded view of one embodiment of a microtube and closure; Figure 2 shows a side elevation of the microtube and closure illustrated in Figure 1 in exploded form; Figure 3 shows a side elevation of the microtube of Figure 2 with the closure inserted; Figure 4 shows an exploded perspective view of a second embodiment of a microtube and closure; Figure 5 shows a side elevation of the microtube and closure of Figure 4; Figure 6 shows an elevational view of the microtube and closure of Figure 5 with the closure partially inserted into the microtube; Figure 7 shows the microtube and closure of Figure 6 with the closure fully inserted into the microtube and the skirt rolled over the top of the microtube; Figure 8 shows a perspective view of a partially filled block of microtubes; and Figure 9 shows a cross-sectional view of a partially filled microtube of the embodiment illustrated in Figures 1 to 7. Referring to Figures 1 to 3 there is shown a standard microtube 1 . The microtube 1 is formed from a plastics material, resistant to the compounds to be stored therein, for example the solvent DMSO (Dimethyl Sulfoxide) . A septum bung or cap 2 having a substantially cylindrical portion 3 and radially projecting shoulder 5 is also provided. The bung 2 is produced from a silicone based material arranged to re-seal itself following being pierced with a needle. The material is resilient and the bung 2 is of appropriate dimensions to effect an interference fit with the microtube 1 , when inserted as shown in Figure 3. A two dimensional machine readable dot code 4 is printed onto the side of the microtube 1 . Referring to Figures 4 to 7 there is shown an alternative microtube 6 and bung 7. The microtube 6 is formed from a plastics material and includes a shoulder 8. The open end of the tube is of reduced external diameter compared to the rest of tube. The bung 7 is produced from a silicone based material arranged to re-seal itself following being pierced with a needle. The bung 7 includes a cylindrical portion 9 and an integrally formed flexible skirt portion 10. In use, the bung 7 is inserted into the microtube 6 and the skirt 10 rolled over the top of the microtube 6, to provide an enhanced seal. When the skirt 10 is rolled down the lower edge of the skirt is arranged to lie substantially adjacent the shoulder 8, as shown in Figure 7. In both the embodiments illustrated in Figures 1 to 7 the bung serves to protect the contents of the microtube, particularly from atmospheric contamination, whilst allowing access to the contents of the microtube by way of a hollow needle and preferably a coaxial hollow needle to enable the passage of air or some other gas in or out of the microtube in response to the addition or extraction of liquid. Microtubes with pierceable septum bungs are particularly suited to use with automated laboratory equipment. Referring to Figure 8 microtubes 1 1 with septum bungs 1 2 may be stored in blocks 1 3 for ease of handling in bulk. For example, for use in high throughput screening. The microtubes are stored with the bung 1 2 uppermost to facilitate the use of automated laboratory equipment. The provision of a microtube with a pierceable bung enables the convenient preparation of a large number of samples using automated equipment. First, the bung 1 2 is inserted into the microtube 1 1 , this may be done manually or by machine. Then, the microtube 10 with bung 1 2 is placed into a block 13 along with other microtubes. The microtubes may then be filled with a desired compound by the use of a hollow needle, preferably a coaxial needle. The use of a coaxial needle allows air or an inert gas to flow in and out of the microtube in response to the injection or withdrawal of a liquid. This enables a sample to be prepared under an inert gas. A coaxial needle comprises an inner and outer hollow needle. The inner needle extends further than the outer needle so that the inner needle may be extended into a liquid sample whilst the end of the outer needle remains above the liquid level to enable air or gas to flow into the region between the inner and outer needles. Referring to Figure 9 there is shown a cross-section of a microtube 1 4 with a bung 1 5 inserted therein. A hollow coaxial needle 1 6 is shown inserted through the bung 1 5. A liquid 1 7 has been injected into the microtube through the needle 1 6. After injection the needle 1 6 may be withdrawn from the bung 1 5 which will then seal the microtube 1 4, protecting its contents 1 7 from, inter alia, atmospheric contamination. Subsequent extraction or addition of further liquids or reagents may be effected by the insertion of further needles through the bung 1 5. The bung is able to withstand at least 100 piercings before losing its sealing integrity. Liquid for injection into a microtube may be prepared in a vial, of larger volume than a microtube, also having a septum bung. The required solid product is placed in the vial along with a solvent and the bung inserted. Alternatively, the solvent may be injected through the bung. The vial is then agitated to assist dissolution of the solid. The prepared solution is then withdrawn from the vial by way of a hollow needle and may then be injected into one or more microtubes. Microtubes fitted with septum bungs allow liquid products to be conveniently injected and extracted using hollow needles, possibly by automated equipment. This leads to savings in labour costs and great sample containing integrity than with prior art microtubes sealed with conventional caps or mats. The above embodiments are described by way of example only, variations are possible without departing from the invention.

Claims: CLAIMS 1 . A method of preparing a sample comprising the steps of:- providing a microtube having an opening therein; providing a self sealing pierceable closure for said microtube; inserting said closure member into the opening of said microtube to seal the microtube; inserting a hollow needle through said closure into said microtube; injecting a liquid into said microtube through said hollow needle; withdrawing said hollow needle from said closure member, to allow said closure member to seal said microtube. 2. A method as claimed in claim 1 , wherein said closure comprises a septum cap. 3. A method as claimed in either claim 1 or 2, wherein said closure member comprises a silicone based material. 4. A method as claimed in any preceding claim, wherein said hollow needle is a coaxial needle. 5. A method as claimed in any preceding claim further including the step of marking the microtube to identify the sample. 6. A method as claimed in claim 5, wherein the microtube is marked with a two dimensional dot code. 7. A method as claimed in any preceding claim, wherein the step of inserting the hollow needle through the closure; injecting a liquid into the microtube and withdrawing the hollow needle are carried out using automated laboratory equipment. 8. A method as claimed in any preceding claim, wherein the step of inserting said closure member into the opening of said microtube is carried out using automated equipment. 9. A method as claimed in any preceding claim including the step of using a hollow needle to withdraw a sample from the microtube. 10. A method as claimed in any preceding claim including the step of injecting an inert gas into said microtube through said hollow needle. 1 1 . A microtube assembly comprising a microtube and a self-sealing pierceable closure for use in the method of providing a sample as claimed in claim 1 . 1 2. A microtube assembly as claimed in claim 1 1 , wherein said closure member comprises a septum cap. 13. A microtube assembly as claimed in either claim 10 or 1 1 , wherein said septum cap comprises a silicone based material.

Inventors: CLOUGH GRAHAM, CLOUGH, GRAHAM
Applicants: CLOUGH GRAHAM, THURNALL PLC, CLOUGH, GRAHAM
Application year: 1998
Main classification: G01N1
IPC codes: B01L3, G01N1, G01N35