Organic compounds -- part of the class 532-570 series – Organic compounds – Carbohydrates or derivatives
Reexamination Certificate
2000-01-03
2001-07-03
Wilson, James O. (Department: 1623)
Organic compounds -- part of the class 532-570 series
Organic compounds
Carbohydrates or derivatives
C536S025410, C536S025420, C435S306100
Reexamination Certificate
active
06255478
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to an apparatus for extracting nucleic acids from various nucleic acid-containing samples, particularly biological samples. More particularly, the invention relates to a nucleic acid extraction apparatus well suited for a technology for extracting nucleic acids using a nucleic acid-binding magnetic carrier.
DESCRIPTION OF RELATED ART
The extraction of nucleic acids from biological or other samples is being practiced of late in many fields. For example, genetic engineering and construction of DNA probes in particular involve a procedure of extracting DNA or RNA coding for an objective protein from cells producing the protein. Moreover, the clinical examination for detecting a virus DNA or RNA using a DNA probe includes a procedure of extracting the target DNA or RNA from a biological sample.
The procedure of extracting nucleic acids is, thus, of great importance in various fields. The hitherto-known technology for extracting nucleic acids includes a method which comprises treating a sample with a caustic reagent, extracting the nucleic acid with phenol or phenol-chloroform, and recovering DNA by ethanol precipitation and a method which comprises treating a sample with a proteolytic enzyme such as proteinase K in the presence of a surfactant and then extracting the nucleic acid (Idenshi Kogaku [Genetic Engineering], Vol. 1, No. 1, p. 112-119, 1997), among others.
The vessel used conventionally in those extraction methods includes a group of plastic microtubes each provided with a cover as described in Unexamined Japanese Patent Publication No. 18362/1985 (Examined Japanese Patent Publication No. 31945/1992). This vessel is generally used with said cover kept open during the extraction procedure.
A variety of nucleic acid extraction apparatuses have been proposed according to the above nucleic acid extraction technology.
For example, Unexamined Japanese Patent Publication No. 125972/1991 describes a nucleic acid extraction apparatus designed to prevent viral infection and improve the efficiency of extraction which comprises a multiarticulated industrial robot and peripheral units necessary for DNA extraction and purification.
Unexamined Japanese Patent Publication No. 131076/1992 discloses an extraction apparatus designed to improve the efficiency of extraction of nucleic acids from a small amount of blood or other biological material through a compact arrangement of means for transfer of the nucleic acid extraction vessel to a centrifuge.
Unexamined Japanese Patent Publication No. 187077/1992 discloses an automatic pretreatment system for DNA sequencing which comprises a filter unit attached to an aspiration-discharge system, a thermostat and a means for carrying out the necessary mixing and concentration. Unexamined Japanese Patent Publication No. 47278/1997 discloses an extraction apparatus employing a filter system equipped with a vacuum pump in lieu of a centrifuge.
The nucleic acid extraction procedure generally comprises a series of steps, namely hemolysis, leukocyte concentration, cell membrane lysis, and nucleic acid purification. The operations performed in the above-mentioned extraction methods in common are illustrated in the block diagram of FIG.
1
. Thus, the nucleic acid extraction procedure generally comprises an operation for charging the vessels with samples and other solutions, a mixing operation necessary for carrying out the reaction, a solid-liquid separating operation, and an operation for removal of unwanted components or recovery of the nucleic acid.
Meanwhile, the conventional nucleic acid extraction apparatus described above is such that the solid-liquid separation in the above series of operations is performed either by means of a centrifuge or by filtration. Therefore, in order that a fully automatic extraction apparatus may be implemented, a centrifuge or a vacuum pump and the associated hardware must be built into the apparatus, with the result that the whole apparatus is inevitably bulky, complicated in construction, and increased in fabrication cost.
As the result of recent advances in the nucleic acid amplification technology, it has become possible to analyze and detect the desired domain of a nucleic acid using a very small amount of sample. Therefore, the technology for extracting nucleic acids from small biological samples with high reliability is more important than the technology for extracting nucleic acids on a large scale.
In clinical examination or diagnosis, a large number of samples must be dealt with at one time. Therefore, it is common practice to perform a nucleic acid extraction using a multiplicity of vessels arranged for respective samples within the limited space of an automated apparatus.
In this case, however, when the above-mentioned so-called open-system microtubes are used as the vessels and the distribution or discharging of the samples, extraction reagents, etc. is carried out, the contamination problem which is most abhorred in clinical diagnosis is liable to take place because of carryovers from one microtube to another.
SUMMARY OF THE INVENTION
The present invention has for its primary object to provide an automatic extraction apparatus by which the extraction of nucleic acid involving a complicated series of operations can be automatically performed.
It is a further object of the invention to overcome the drawbacks of the conventional nucleic acid extraction apparatuses, namely the increased equipment size, complexity and high cost due to the use of a centrifuge or a vacuum pump and the above-mentioned contamination problem and thereby provide a nucleic acid extraction apparatus free from such disadvantages and suited for use in clinical diagnosis.
It is a still further object of the invention to provide an extraction vessel suited for use in the nucleic acid extraction method utilizing a nucleic acid-binding magnetic carrier as described in Unexamined Japanese Patent Publication No. 19292/1997, for instance, and a nucleic acid extraction apparatus tailored to the structural features of said extraction vessel.
The present invention, thus, is directed to the following nucleic acid extraction apparatuses
1
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6
.
1. A nucleic acid extraction apparatus comprising
(1) a group of extraction vessels each comprising a reactor tube in which a sample, a reagent solution and a magnetic carrier are admixed and reacted, a drain cup for pooling an unwanted component solution and a nucleic acid recovery tube, all as secured to a supporting plate,
(2) a distribution means for dispensing a sample or other solution into each of said extraction vessels,
(3) a stirring means for stirring the sample solution and magnetic carrier within the extraction vessel,
(4) a holding means for holding said magnetic carrier stationary in a position within the extraction vessel,
(5) a discharging means for discharging the sample solution from the extraction vessel while said magnetic carrier is held stationary,
(6) a heating means for heating the sample solution containing the magnetic carrier in said extraction vessel, and
(7) a transfer means for transferring said extraction vessel to the required positions where said distribution means, stirring means, holding means, discharging means, and heating means are respectively disposed.
2. A nucleic acid extraction apparatus comprising
(1) a vessel stand adapted to support a group of extraction vessels each comprising a reactor tube to be filled with a magnetic carrier, a sample and a reagent solution, a drain cup and a nucleic acid recovery tube, all as secured to a supporting plate;
(2) a distribution means for dispensing a sample or other solution into the reactor tube of said extraction vessel installed on said vessel stand;
(3) a stirring means for stirring the magnetic carrier, sample, and reagent solution within the reactor tube;
(4) a holding means for holding the magnetic carrier stationary within the reactor tube;
(5) a discharging means for discharging the solution in the reactor tube into the drain cup or nucleic acid recovery t
Daimon Katsuya
Komai Shigeru
Takarada Yutaka
Kenyon & Kenyon
Toyo Boseki Kabushiki Kaisha
Wilson James O.
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