ABSORBENT DIPPER FOR SOLVENT EXTRACTION

Abstract: A device for removing a solution from the receptacle comprising holding means and a substantially stiff absorbent portion adapted to allow insertion into the receptacle, the end of which is shaped to substantially prevent contact with a pellet formed in said receptacle is disclosed. Also disclosed is a method of removing the solution from a receptacle employing the aforementioned device.

Description: ABSORBENT DIPPER FOR SOLVENT EXTRACTION The present invention relates to a device for, and a method of, removing solution from a receptacle, such as a microcentrifuge tube or micro-titre plate. Many life science experiments require the extraction and purification of DNA, RNA or proteins and the methods used in the extractions often include precipitation and centrifugation steps in order to pellet the DNA, RNA or proteins. Conventional means of removing the solution after pelleting involves pouring the solution out of the centrifugation tube. However, there is typically a residual solution left in the centrifugation tube following centrifugation (typically approximately 50 - 100 microlitres in a 1.5ml microcentrifuge tube) and this usually has to be removed prior to the next procedure. Standard techniques for removing the solution include lyophilisation to remove the remaining solution or a paper tissue may be used to wipe the inside of the tube. However, lyophilisation is generally time consuming, labour intensive and moreover requires specialist equipment, while removal of solution with a paper tissue can lead to damage or even removal of the pelleted sample by the paper tissue. Moreover, contamination of the sample by the paper tissue can also occur as a result of fibres from the tissue falling onto the sample or where different corners of the same paper tissue is used to remove the excess solution. In addition, paper tissues are not usually sterile, or have not been otherwise treated in order to ensure that DNases and the like which, may be present on the tissue, have been inactivated. It is an object of the present invention to obviate and/or mitigate at least one of the aforementioned disadvantages. For example it is an object of the present invention is to provide a device for, and a method of removing solution from a receptacle, which is simple and economical. According to a first aspect of the present invention there is provided a device for removing a solution from a receptacle, the device comprising: a first portion comprising holding means; and a second substantially stiff absorbent portion adapted to allow insertion into the receptacle, a first end of which is connected to the first portion, and a second end of which is shaped to substantially prevent contact with a pellet formed in said receptacle when in use. The holding means may be elongate for gripping by a user's fingers. Alternatively the holding means may be adapted to fit to a further device such as a typical pipettor (eg. Gilson pipette) known in the art. In this manner the device may have a cylindrical holding means into which the end of a pipettor is inserted. Preferably the second end of the absorbent portion is shaped to substantially prevent contact with a pellet which may be formed near the bottom of the receptacle. For example, if a pellet is formed on a side of the receptacle near the bottom, the second end may be angled and/or channelled to allow the device to absorb any solution present at the bottom of the receptacle while substantially preventing contact with said pellet. For example the second end may be in the form of a cone or truncated cone. When the receptacle is cylindrical in shape the cone or truncated cone may be similarly circular. Alternatively, if a pellet is formed at the base of the receptacle, the tip of the device may be generally blunt (eg. a frusto- conical) or concave to prevent contact with said pellet. It is to be understood that the term "stiff" is intended to mean that the material of the absorbent portion is substantially resistant to compression or bending but is not necessarily rigid. Preferably, at least part of the absorbent portion may be shaped to form a substantially close fit with the internal walls of the receptacle. In particular, the absorbent portion may be generally cylindrical or conical- shaped and may be hollow or solid. The absorbent portion is typically elongate in order to reach the bottom of for example microcentrifuge tubes. It is to be understood that the term "solution" may encompass organic solvents, such as ethanol and the like, inorganic solvents, such as acids, and aqueous solutions, such as water which may or may not contain a salt. The absorbent portion may be designed to absorb organic, inorganic and/or aqueous solvents separately, or may be designed to absorb any/all of the abovementioned solutions. That is, the aforementioned properties need not be mutually exclusive and, in fact, the same absorbent portion may absorb more than one of the above classes of solutions. It is also to be understood that the term "receptacle" may encompass different sized tubes, microcentrifuge tubes, (for example 2ml, 1.5ml or 0.5ml microtubes) , multi-well microtitre plates and the like. The abovementioned pellet may be, for example, a pellet formed from nucleic acids, for example DNA or RNA, or a pellet formed from polypeptides, for example proteins. The absorbent portion may be composed of a material which is neutral or a material which is intended to repel the formed pellet, and therefore substantially prevent removal of the pellet should the absorbent portion contact the pellet. For example, when the pellets are formed from negatively charged compounds, such as DNA or RNA, the absorbent portion may be composed of a negatively charged material. Alternatively, when the pellets are formed from positively charged compounds, the absorbent portion may be composed of a positively charged material. Furthermore, for pellets formed of ionic or polar material in general, the absorbent portion of the device may be composed of non- ionic or non-polar materials, such as hydrophobic materials. The device may also be colour-coded so that a user may easily identify whether the device is for example positively charged (eg. red) or negatively charged (eg. blue) . Preferably, the device, or more particularly the absorbent portion may be sterilisable by, for example, heat, gamma irradiation or the like. The portions of the device may be formed of the same material or separate materials. Preferably, the device may be formed in one integral piece. Alternatively, the portions may be made independent of one another and/or from different materials, which are eventually brought together to form the device. The device may also be "double-ended". That is, with absorbent portions at either end and with one central portion acting as the holding means in use. Conveniently, the device may be formed from, for example, chromatography paper since this possesses good absorbing capabilities. However, other absorbent materials may also be suitable such as hydrogel like materials, cotton, absorbent celluloses such as carboxy methyl cellulose, activated charcoal, nylon, other textiles or composite materials and the like. However, it is understood that the absorbent material should not shed any fibres and the like which may contaminate the pellet. According to a second aspect of the present invention there is provided a method of removing solution from a receptacle employing a device according to the present invention, said method comprising the steps of: SUBSTTΠΠΈ SHEET(RULE 26) holding said device by the holding means, inserting the substantially stiff absorbing portion into said receptacle in an orientation so as to substantially avoid contact between said absorbent portion and a pellet formed in said receptacle, leaving said absorbent portion in the said receptacle for a time sufficient to substantially remove said solution, and removing said absorbent portion from said receptacle while substantially avoiding contact between said absorbent portion and said pellet. Optionally, the device may thereafter be allowed to touch the pellet, when the absorbent material and the pellet are similar charged, as the absorbent material and the pellet will repel each other. These and other aspects of the present invention will become apparent from the following description when read in conjunction with the accompanying drawings, in which: Figure 1 is a side perspective elevation of a device in accordance with an embodiment of the present invention; Figure 2 is a front view of a device as illustrated in Figure 1 placed in a microcentrifuge tube; Figure 3 is a front view of an alternative embodiment of the present invention placed in a microcentrifuge tube; and Figure 4 is a front view of a further embodiment of the present invention placed inside a microcentrifuge tube. Referring firstly to Figure 1 of the drawings, the device 10 embodying the invention comprises a generally three dimensional cylindrical-shaped body 12, an SUBSTTTUTE SHEET (RULE 26) asymmetrical conical shaped tip 14 and holding means 16. The device 10 is formed from a flat, two-dimensional template which is subsequently rolled into a tube with flat holding means 16 at the top. The point of the device is constructed to form an asymmetric tip 14. As illustrated in Figure 2, the device 10 is placed within a microcentrifuge tube 18 and the asymmetrical conical shaped tip 14 is orientated in order to avoid contact with pellet 20. Pellets may form on walls of centrifuge tubes depending on the angle of the tube during centrifugation. For example, the pellet 20 of Figure 2 is commonly formed by fixed angle centrifugation where the angle of the tube orientation is approximately 45 degrees from the vertical. Removal of the solution from the microcentrifuge tube 18 occurs when the absorbent portion comes into contact with the solution which is absorbed by the absorbent portion as a result of capillary action. The device 10 is then removed from the microcentrifuge. The device 10 may be manufactured in a single article from materials such as Whatman cellulose/cotton blotting and chromatography paper (3MM) catalogue no. 3030917 (Whatman International, 20/20 Maidstone, Kent, ME16 0LS, United Kingdom) . As a result of the close fitting between the sides of the absorbent portion 12 of the device 10 and the internal walls of microcentrifuge tube 18, the device 10 can be inserted with reasonable force without the risk of contacting pellet 20. SUBSTTTUTE SHEET (RULE 26) A second embodiment 10b of the present invention is illustrated in Figure 3. Device 10b has a tip 14b shaped to form a blunt or concave end in order to avoid contact with pellet 20b which has formed at the base of the microcentrifuge tube. Pellets are commonly formed at the base of centrifuge tubes when swing-arm rotors are used. These allow the tube to assume a substantially horizontal position during centrifugation. A further embodiment of the invention is illustrated in Figure 4. Device 10c has a symmetrically rounded or convex tip 14c. However, the sides of absorbent portion of device 10c are not intended to form a close fit with microcentrifuge tube 18. Instead, the device 10c is inserted down the centre of the tube 18 to contact the base of the tube 18 and thereby avoid pellet 20c formed on the wall at the base of tube 18. It is to be appreciated that the device substantially reduces the risk of contaminating the sample with for example fibre deposits which may arise from using paper tissue. When the absorbent portion of a device having an asymmetrically formed tip, as illustrated in Figure 1, is formed from a material having a similar ionic charge as a sample, the angled tip may be turned around to touch the sample in order to dry the sample as well as the tube. Since the dipper has a similar charge as the sample, they will repel one another and so the sample will not stick to the dipper. This may also apply to the device depicted in Figure 4. The charge of the material used for the device SUBSTTTUTE SHEET (RULE 26) would be dependant upon the usage. It will be appreciated that various modifications may be made to the embodiment hereinbefore described without departing from the scope of the invention. For example, the device may be manufactured from two separate materials, each corresponding to the holding means and the absorbing means, which are then brought together to form the complete device. It will be appreciated that the principal advantage of the present invention is that the device substantially reduces the time, labour and expense required for removal of residual solution in a receptacle. Furthermore, the devices can be sterilised and can therefore reduce or even eliminate contamination of the sample. Moreover, since the device is intended to be used once, this further reduces any possibility of contamination. As a result of their simple design, devices may be manufactured economically and in quantity. SUBSTTTUTE SHEET (RULE 26)

Claims: C IMS 1. A device for removing a solution for a receptacle comprising: a first portion comprising holding means; and a second substantially stiff absorbent portion adapted to allow insertion into the receptacle, a first end of which is connected to the first portion, and a second end of which is shaped to substantially prevent contact with a pellet formed in said receptacle when in use. 2. A device according to claim 1 wherein the second end of said second substantially stiff absorbent portion is shaped to substantially prevent contact with the pellet formed near the bottom of the receptacle. 3. A device according to claim 2 wherein the tip of the second end of the absorbent portion is angled and/or channelled to allow the device to absorb solution present at the bottom of the receptacle while substantially preventing contact with said pellet. 4. A device according to claim 2 wherein the second end of said absorbent portion is blunt or concave to allow the device to absorb any solution present in the receptacle while substantially preventing contact with a pellet formed at the base of the receptacle. 5. A device according to any preceding claim wherein at least part of the absorbent portion is shaped to form a substantially close fit with the internal walls of the receptacle. 6. A device according to claim 5 wherein the absorbent portion is generally cylindrical or conical- shaped. 7. A device according to claim 5 wherein the absorbent portion is hollow or solid. 8. A device according to any preceding claim wherein the absorbent portion is designed to absorb at least one selected from the group consisting of organic solvents, inorganic solvents and aqueous solvents. 9. A device according to any preceding claim wherein said receptacle is selected from the group consisting of 2ml microcentrifuge tubes, 1.5ml microcentrifuge tubes, 0.5ml microcentrifuge tubes and multi-well microtitre plates. 10. A device according to any preceding claim wherein said absorbent portion is composed of a material which is neutral or a material which is intended to repel the pellet formed. SUBSTTTUTE SHEET (RULE 26) 11. A device according to claim 10 wherein said absorbent portion is composed of a negatively charged material when it is intended to be used with negatively charged compounds. 12. A device according to claim 10 wherein said absorbent portion is composed of a positively charged material when it is intended to be used with positively charged compounds. 13. A device according to claim 10 wherein said absorbent portion is composed of non-ionic or non-polar materials when it is intended to be used with ionic or polar charged pellets, respectively. 14. A device according to any preceding claim wherein said absorbent portion is sterilised. 15. A device according to claim 14 wherein said absorbent portion is sterilised by gamma irradiation. 16. A device according to any preceding claim wherein said first portion and said second portion are formed of the same material. 17. A device according to claim 16 wherein said device is formed in one integral piece. SUBSTTTUTE SHEET (RULE 26) 18. A device according to any of claims 1 to 15 wherein said first portion and said second portion are formed of separate materials. 19. A device according to claim 18 wherein said separate portions are eventually brought together to form the device. 20. A device according to any preceding claim wherein said device comprises absorbent portions at either end with a central portion acting as the holding means in use. 21. A device according to any preceding claim wherein said device is formed from a material selected from the group consisting of chromatography paper, hydrogel-like materials, cotton, absorbent celluloses, activated charcoal and nylon. 22. A method of removing solution from a receptacle employing a device according to claims 1 - 21 wherein said method comprises the steps of: holding said device by the holding means, inserting the substantially stiff absorbing portion into said receptacle in an orientation so as to substantially avoid contact between said absorbent portion and a pellet formed in said receptacle, leaving said absorbent portion in said receptacle for a time sufficient to substantially remove said solution, and removing said absorbent portion from SUBSTTTUTE SHEET (RULE 26) said receptacle when substantially avoiding contact between said absorbent portion and said pellet.

Inventors: GOW JOHN WILLIAM, GOW, JOHN, WILLIAM
Applicants: GOW JOHN WILLIAM, UNIV GLASGOW, GOW, JOHN, WILLIAM, THE UNIVERSITY COURT OF THE UNIVERSITY OF GLASGOW
Application year: 2000
Main classification: G01N1
IPC codes: B01L3, G01N1, G01N35