1. Technical Field
The present invention relates to thermal cyclers and thermal cycling methods.
2. Related Art
Recent studies revealed genes involved in a wide range of diseases, and there is growing interest in remedies that use genes, such as in gene diagnosis and gene therapy. Manly techniques that use genes for variety discrimination and breeding also have been developed in the field of agriculture and livestock. One widely used technique that makes use of genes is the nucleic acid amplification technique. A commonly known example of the nucleic acid amplification technique is PCR (Polymerase Chain Reaction). PCR is a technique used to amplify the target nucleic acid in the thermal cycling of a solution (reaction mixture) that includes a nucleic acid to be amplified (target nucleic acid) and reagents. The thermal cycling is the process by which the reaction mixture is periodically subjected to two or more stages of temperature. Thermal cycling that involves two or three stages is commonly used in PCR. PCR has become a technique indispensable for understanding the information of biological substances.
PCR generally uses a biochemical reaction chamber called a tube or a biotip (biological sample reaction tip). However, the techniques of related art are problematic, because the reaction uses large amounts of reagents and other materials, and is time consuming. The reagents used for PCR are generally expensive, and should desirably be used in as small an amount as possible. Further, a reactor capable of performing PCR in a short time period is needed for, for example, the diagnosis of infections. As a solution to these problems, JP-A-2009-136250 discloses a biological sample reactor with which thermal cycling is performed by moving a reaction mixture while a biotip charged with the reaction mixture and a liquid immiscible with the reaction mixture and having a smaller specific gravity than the reaction mixture (such as mineral oil; hereinafter, such liquids will be referred to simply as “liquid”) is rotated about a horizontal rotational axis.
In the biological sample reactor disclosed in JP-A-2009-136250, the biotip is continuously rotated to perform a thermal cycle for the reaction mixture. Because the reaction mixture moves within the channel of the biotip as the biotip rotates, the biotip needs to be devised by, for example, making a complicated channel structure, in order to maintain the reaction mixture at a desired temperature for a desired time period.