Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01L—CHEMICAL OR PHYSICAL LABORATORY APPARATUS FOR GENERAL USE
  • B01L3/00—Containers or dishes for laboratory use, e.g. laboratory glassware; Droppers
  • B01L3/50—Containers for the purpose of retaining a material to be analysed, e.g. test tubes
  • B01L3/508—Containers for the purpose of retaining a material to be analysed, e.g. test tubes rigid containers not provided for above
  • B01L3/5085—Containers for the purpose of retaining a material to be analysed, e.g. test tubes rigid containers not provided for above for multiple samples, e.g. microtitration plates
  • B01L3/50851—Containers for the purpose of retaining a material to be analysed, e.g. test tubes rigid containers not provided for above for multiple samples, e.g. microtitration plates specially adapted for heating or cooling samples
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01L—CHEMICAL OR PHYSICAL LABORATORY APPARATUS FOR GENERAL USE
  • B01L7/00—Heating or cooling apparatus; Heat insulating devices
  • B01L7/52—Heating or cooling apparatus; Heat insulating devices with provision for submitting samples to a predetermined sequence of different temperatures, e.g. for treating nucleic acid samples

Definitions

• the invention relates to plastic plates for conventional heat block thermocycling
• thermocycler for rapid temperature cycling of small samples is a glass capillary tube and a hot-air thermocycler
• the glass capillary tube can hold reaction volumes ranging from 10 to 20 ⁇ l.
• the hot-air thermocycler can hold 32 capillaries and perform 30 - 40 PCR cycles in 20-30 minutes.
• these rapid DNA amplification technology is connected with various disadvantages, for example:
• the samples as small as 20 ⁇ l are placed into the tubes, the tubes are closed by deformable, gas-tight caps and positioned into similarly shaped conical wells machined in the body of the heat block.
• the heated cover compresses each cap and forces each tube down firmly into its own well.
• the heated platen i.e. heated lid
• PCR tubes can be put in a two-piece holder (US patent 5,710,381) of an 8x12, 96-well microplate format, which can be used to support the high sample throughput needs with any number between 1 and 96 individual reaction tubes.
• the inventors describe a plate with cylindrically shaped walls of the wells and spherically shaped bottoms thereof.
• the individual wells of the plate were formed by melting a polycarbonate sheet in the range of 0.27-0.5 mm by a stream of hot air. This technology leads to relatively thin walls in the range of 0.08-0.2mm.
• the biological samples were placed into the wells, covered with polycarbonate film (0.1 mm) and the individual wells were thermosealed by a special press. Upon sealing the plate was placed on the thermoblock and fixed by screws. Though theoretically the heat transfer to the samples is improved, however, the way of positioning the plate on the block and the cylindrical and spherical geometry of the well prevent a close thermal contact with the heating block.
• thermocycler with an increased ramping rate, i.e. 4° C/second).
• the thermocycler can hold 96 PCR tubes (each of a volume of 0.2 ml) or 96-well PCR plates. Theoretically, the thermocycler can perform 30 PCR cycles in 20-30 minutes, provided that only a few seconds are spent to reach the temperature equilibrium between the heat block and the samples.
• the present invention concerns plastic multiwell plates for performing heat block thermocycling of multiple samples. More specifically, it concerns ultrathin-walled multiwell plates with an improved heat transfer to small samples. Ultrathin-walled multiwell plates are suited for rapid, oil- free, heat block temperature cycling of small- volume samples (i.e. approximately 1-20 ⁇ l), whereas the lower limit is given by the reliability of the conventional pipetting systems.
• Figure 1 illustrates an example of a multiwell plate according to the invention.
• Figure 2 illustrates the positioning of the plate in the block of the thermal cycler.
• thermoplastic films are, for example, polyolefin films, such as metallocene-catalyzed polyolefin films and/or copolymer films.
• the multiwell plate is vacuumformed out of cast, unoriented polypropylene film, polypropylene-polyethylene copolymer films or metallocene- catalyzed polypropylene films.
• the film is formed into a negative ("female") mould comprising a plurality of spaced-apart, conically shaped wells which are machined in the body of a mould in the shape of rectangular- or square-array.
• vacuumforming wells with a draw ratio of two and an average thickness of the walls of 30 microns results in a film thickness of 60 microns.
• the average optimum wall thickness was found to be 20-40 microns.
• the thickness of the well is reduced 7.5-15 fold when compared to the wall thickness of the formerly improved PCR tube desribed in U.S. Patent No 5,475,610.
• heat transfer through one square millimeter of the surface of the well of the plate is increased 7.5-15 fold and the time of temperature transfer through the wall is decreased 56-225 fold when compared to the said PCR tube.
• the thickness of the walls of the formed wells is gradually reduced to the bottoms of the wells due to vacuumforming of the wells into a negative mould. This geometry of the walls of the wells provides several advantages:
• the type of positioning provides several advantages:
• the pressure caused by the screw (12) to the lid (10) (heating element (11)) can be increased in order to obtain efficient sealing of the samples (9) sealed, for example, by a silicon mat (13).
• the pressure is actually directed to those parts of the multiwell plate (1) which are supported by the top surface of the heat block (4) (or by parts of the top surface surrounding individual wells depending on the geometry of the heat block) and not to the thin walls of the wells of the plate as it is the case for the PCR tubes or conventional PCR plates.
• This advantage makes it possibe to increase the sealing pressure of the heated lid (10) several fold when compared to the conventionally used pressure of 30-50 g per well without cracking the conically shaped walls of the wells (2).
• the extremely thin walls of the wells are highly flexible as the multiwell plates are thermo formed out of highly elastic films (or sheets depending on the draw ratio).
• the walls of the wells are highly resistant against stress cracking, due to their flexibility and elasticity.
• the air pressure in the wells will increase at elevated temperatures. The increased air pressure causes a deformation of the walls of wells and brings them in tight thermal contact with the surface of the walls of the individual sample wells machined in the body of the heat block.
• Standard PCR plates (having relatively thick and rigid walls of the wells) require that the conically shaped walls of the wells have to match perfectly with the shape of the wells machined in the body of the heat block to guarantee a close thermal contact (see for example U.S. Patent No 5,475,610).
• This requirement is not as critical for the ultrathin walled multiwell plates of the invention, due to flexibility and elasticity of the walls of the wells.
• special shapes of both, the walls of the wells of the plate and the wells of the heat block can be differently designed. These differently designed wells can promote an even closer thermal contact after positioning the plate into the heat block.
• Another aspect of the invention concerns the frame of the multiwell plates.
• the plates can be formed of very thin films (depending on the draw ratio of the well; supra) the flexibility of, for example, standard-format plates, i.e. 96-well PCR (8,5 x 12,5 cm) plates, is such that handling is not easily possible anymore. Therefore, depending on the geometry of the plate, a supporting frame might be needed, for example for industry standard formats, i.e. 96-, 192-, 384-well PCR plates. This frame can support, for example in case of small plates, the edges of the plate, or individual wells of the plate, or groups of wells.
• the frame can be injection molded in the form of the standard skirted microplates containing the array of holes in the top surface of the frame matching the array of wells of the ultrathin multiwell plate.
• the plate can be attached to the frame by for example heat bonding.
• small format plates including the frame can be formed as a single piece by using specially designed moulds.
• the polypropylene-based plastics are PCR-compatible and therefore widely used for injection molding of PCR tubes and/or multiwell plates. In addition, they are resistant to stress cracking and have a reduced water vapor sorption when compared to other plastics (e.g. polycarbonate).
• Such plates can be thermoformed in both, standard industry formats, i.e. 96-, 192- and 384-well PCR plates for large scale applications, supported by robots and small foot-print formats to match small foot-print thermocyclers, i.e. "personal thermocyclers”.
• Fig.l illustrates a 36-well ultrathin walled multiwell plate according to the invention.
• the plate was designed for rapid temperature cycling of samples ranging from 0.5-4 ⁇ l using a small foot-print peltier-driven heat block thermocycler supplied with a "wine-press" type heated lid (Fig. 2).
• the volume of the wells is 16 ⁇ l and the distance between the wells is 4.5 mm, i.e. industry standard for high sample density 384-well PCR plates.
• the diameter of the openings of the wells is 3.8 mm and the height of the wells is 3 mm.
• the average thickness of the walls of the wells is 30 ⁇ m.
• the frame (3) was cut out of a polypropylene sheet of a thickness of 0.5 mm and heat bonded to the plate (1).
• the area of the plate (1) is 30 x 30 mm.
• the handling of the plate (1) containing the multiple wells (2) is facilitated, by a rigid 0.5-1 mm thick plastic frame (3) which is heat bonded to the plate.
• the ultrathin walled multiwell plate according to the invention (Fig. l) was experimentally tested for the amplification of a 455-base pairs long fragment of human papilloma virus DNA.
• the sample volume was 3 ⁇ l.
• the average ramping rate of the thermo cycler was varied from 4° C to 8° C per second.
• the samples i.e. standard PCR-mixtures without any carrier molecules
• the plate was covered by standard sealing film (Microseal A; MJ-Research, USA), transferred into the heatblock of the thermocycler and tightly sealed by the heated lid as shown in Fig. 2.
• PCR cycler Upon sealing, a number of 30 PCR cycles was performed in 15-25 minutes depending on the ramping rate of the thermo cycler.
• the PCR product was analyzed by conventional agarose electrophoresis.
• the 455-base pairs long DNA fragment was amplified with a high specificity at the indicated ramping rates (supra).
• Plates according to the invention with well volumes of 35 ⁇ l were successfully tested for temperature cycling of samples of a volume of 20 ⁇ l. Thereby, 30 PCR cycles were performed in 20-30 minutes at a ramping rate of 6° C per second.
• the average thickness of the walls was 20 microns and the volume of the wells was 35 ⁇ l, samples of a volume of as few as 0.5 ⁇ l can be easily amplified without reducing the PCR efficiency.
• the ultrathin walled multiwell plates allow a simple and rapid loading of multiple samples by conventional pipettes, rapid sealing of all samples by using conventional sealing films and rapid DNA amplification (15-30 minutes for 30 cycles) with an improved specificity typical for rapid cycling (Wittwer et al., Analytical Biochem., 186, 328-331 [1990]) using appropriate heat block thermocyclers (i.e. ramping rate in the range of 4° C to 8° C per second).

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• Chemical & Material Sciences (AREA)
• Health & Medical Sciences (AREA)
• Clinical Laboratory Science (AREA)
• Chemical Kinetics & Catalysis (AREA)
• General Health & Medical Sciences (AREA)
• Biochemistry (AREA)
• Molecular Biology (AREA)
• Life Sciences & Earth Sciences (AREA)
• Analytical Chemistry (AREA)
• Hematology (AREA)
• Apparatus Associated With Microorganisms And Enzymes (AREA)
• Automatic Analysis And Handling Materials Therefor (AREA)
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• Resistance Heating (AREA)

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• 1998
  • 1998-10-29 EP EP98120187A patent/EP1000661A1/fr not_active Withdrawn
• 1999
  • 1999-10-28 DE DE69914220T patent/DE69914220T2/de not_active Expired - Lifetime
  • 1999-10-28 AT AT99952630T patent/ATE257743T1/de active
  • 1999-10-28 EP EP99952630A patent/EP1133359B1/fr not_active Expired - Lifetime
  • 1999-10-28 WO PCT/EP1999/008178 patent/WO2000025920A1/fr active Search and Examination
  • 1999-10-28 JP JP2000579350A patent/JP4538152B2/ja not_active Expired - Fee Related
  • 1999-10-28 CA CA002348564A patent/CA2348564A1/fr not_active Abandoned

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