Abstract:
The present invention discloses a two-stage reaction and detection tube comprises a first tube, a second tube and a connector. The first tube comprises a detection space for placing a dipstick and a detection space for the test result. The second tube comprises a storing space for the PCR or RT-PCR reagents and the target gene segments. The connector comprises a first portion and a second portion which connect to the first tube and the second tube respectively. The connector further comprises a diversion unit, a liquid collection space, and a dipstick fixing space, where the liquid collection space is connected to the dipstick fixing space. The target gene amplification and detection could be directly processed in the same tube without any liquid transfer.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to the field of biology, and more particularly, to a two-stage nucleic acid reaction and detection tube which is to perform polymerase chain reaction (PCR) and/or nucleic acid detection and can be directly processed in the same tube without any liquid transfer. 
     2. Description of the Prior Art 
     Polymerase chain reaction (hereinafter referred to as “PCR”) is a technology for rapid amplification of DNA, and its principle and the main operational steps may include: (a) denature: using a relatively high temperature (90˜95° C.) for the double-stranded DNA dissociating into single stranded DNA, which is then used as a template for replication; (b) primer annealing: when the temperature is lowered to a predetermined temperature, primers will be adhered to the correct positions of the target genes; (c) primer extension: the reaction temperature will be adjusted to 72° C., in combination of using magnesium ions as enzyme cofactors, the deoxy-ribonucleotide triphosphate (hereinafter referred to as “dNTPs”) will be sequentially adhered to and after the primer by DNA polymerases, in accordance with the base sequence of nucleotides on the template, so as to form a synthetic DNA fragment. By repeating the three-step process of temperature oscillation, the number of the target gene can be doubled in each repetition of the three-step process, thus can be 109 times after 40 cycles of the three-step process. The signal of the target gene can therefore be amplified. Accordingly, the PCR detection technology is generally used for detecting molecular signals in clinical diagnosis, such as pathogen diagnosis, diagnosis of genetic disease, diagnosis of cancer tumors, or the like. The RT-PCR technique which is derived from PCR also has similar principle and application, therefore is widely used in current techniques clinical diagnosis. 
     Devices used to perform PCR or RT-PCR reactions often include heat resistant plastics as the materials of the reaction tube. The amplification of nucleic acid is achieved by using the thermostat metal to repeatedly increase and decrease the temperature for the tube so as to reach different temperatures in each three-step process. In current system, the system with thermostat metal requires a relatively lager space, the entire temperature control system may occupy a larger space and heat capacity ratio. In addition, according to current practice of operation, one test required 30-35 cycles and the time required for the reaction is about two to three hours, consequently, most of the time of the process relies on waiting for the rise of the temperature or cooling metal, making it difficult to reduce the reaction time. 
     In addition, the amplification of the target gene in PCR or RT-PCR is often conformed by gel electrophoresis, which can separate the nucleic acid by its molecular size. After the PCR or PT-PCR process, the product containing amplified target gene (hereinafter “the product”) is transferred from the tube into a previously prepared gel well and since the nucleic acid contains negatively charge in neutral or alkaline solution, it will move toward the anode wherein the moving speed is proportional to it molecular weight. By this process, it can be checked if the amplification of nucleic acid successes or not. However, even the gel electrophoresis detection exhibits high accuracy, it still takes several hours to complete the PCR/RT-PCR and gel electrophoresis. For those diagnoses which are willing to obtain results in short time, it would be not suitable to use PCR/PT-PCR to approach the diagnosis or inspection. In addition, when performing the gel electrophoresis, the product of PCR/RT-PCR needs to be transferred from the reaction vessel to the gel well, and the product is easily contaminated during transferring, which may result in false positive. 
     To shorten the reaction time, a technology that uses thermal convection for performing PCR has been developed (hereinafter “thermal convection PCR”). This technology was first designed by Krishnan et al., T and it uses a cylindrical tube of the Rayleigh-Benard cell with two different heating sources which are disposed at two corresponding sites of the tube. In general, the top level of the reagent is maintained at around a temperature of about 60° C., while the bottom temperature is about 95° C. By the temperature differences arising from the cylindrical cavity through the upper and lower end, it can drive the flow of fluid in the chamber, thus processing the PCR reaction. This embodiment may also be applied to RT-PCR. From this, other technology derived from it with similar principle has been developed for commercial use, such as the use of isolated single point of heating technology called “insulated isothermal polymerase chain reaction” (iiPCR), which performs the RCR reaction in a closed capillary in combination of three points heating sources; or by using non-contact irradiation heating source, which contains heating point of the cylindrical tube closed loop design to achieve the effect for the PCR or RT-PCR. By using the thermal convection process, PCR as well as RT-PCR will not need to use thermostat metal to be repeated temperature oscillation of three steps of the reaction temperature, so it can save a lot of repeated heating and cooling time, thus reducing the use of temperature control metal. 
     In order to avoid the product of the PCR/RT-PCR from being contamination, which would result in false positive, there are more and more detection technologies used to replace original gel electrophoresis, such as using a specific binding fluorescence chemical compound to combine the target gene. When a laser beam with appropriate wavelength is applied, the chemical compound will emit fluorescence, and it will be detected by the equipment. The intensity of the fluorescence is proportional to the amount of the product of PCR/RT-PCR, so the method can reach in-situ qualitative or even quantitative inspection, thus reducing the reaction temperature. 
     In another aspect, there is one common inspection technology that uses a specific binding dipstick for the target gene to detect the product of PCR/RT-PCR. The method includes using two different antigens that can specifically bind antibody, for example, the first type of antigen is DIG or TexasR, and the second type of antigen is Avidin or FITC. After the reaction, the product would contain these two types of antigens. In addition, one side of the dipstick is attached to an Ag gel, emulsion beads or other coloring compounds, which can specifically bind the antibodies of the above-mentioned antigens, such as Biotin-anti-FITC or other specific binding protein; the other side of the dipstick is attached to a cotton pad; and some portions of the dipstick is coated to the antibody of the first type of antigens such as anti-DIG, anti-TaxasR or other specific binding antibody. After the reaction, the product of PCR or RT-PCR is transferred to the end of the lipstick that contains the coloring compound, and the first type of antigen will specifically bind the first type of antibody to forma first type antigen-antibody-coloring complex. The complex will then move toward the terminal end with cotton pad. When it moves at the part containing the second type of antibody, the second type of antigen will specifically bind the second type of antibody and thus exhibit colors. The user can therefore obtain the result according to the colors. Since there are only several minutes that are used to complete the dipstick detection, it can save more time in comparison to convention electrophoresis method. In other situation, the antibody can be replaced by the nucleic acid probe depending on different requirement. 
     As described above, since the thermal convection PCR and the dipstick detection method can save a lot of time comparing to convention PCR/RT-PCR and gel electrophoresis method, it is widely used in the industry in this field. However, there is still not found a detection tube that can operate both thermal convection PCR and the dipstick detection method in single tube. Conventional method is to complete the thermal convection PCR in one tube and then to transfer the reagent onto the dipstick so as to carry out the entire detection method. However, since the product is difficult to take out from the tube, it is not such convenient to operate the system, and it also raises the risk of contamination. 
     Accordantly, there is still a need to have a two-stage detection tube that can both perform polymerase chain reaction (PCR) and/or nucleic acid dipstick detection and can be directly processed in the same tube without any liquid transfer. 
     SUMMARY OF THE INVENTION 
     To solve the abovementioned problem, the present invention is directed to a two-stage nucleic acid tube. By using said tube, no additional steps of transferring chemical reagents are required. After performing the convection PCR or PT-PCR, the first tube can directly connect the second tube with dipstick and the connector, the nucleic acid reaction can be performed in one single device and the result can be checked by the dipstick. 
     To achieve the above-mentioned object, according to one preferred embodiment of the present invention, the device includes a first tube including a first connection portion and a detection space. The detection space is used for placing a dipstick with one cotton end; a second tube including a second connection portion and a storing space, wherein the storing space is used to accumulate the sample of the target gene and corresponding reagents. The connector includes a first portion and a second portion, which respectively connects the first connection portion and the second connection portion, wherein the first portion of the connector comprises a diversion unit and a liquid collection space, the diversion unit can lead the liquid in the storing space to the liquid collection space, and the second portion comprises a dipstick fixing space for placing the dipstick, and the dipstick fixing space is connected to the liquid collection space. 
     After performing the thermal convection PCR and/or the RT-PCR, the dipstick can be placed in the first tube and the connector in advance, and the first tube, the second tube and the connector are assembled to forma closed detection tube. After assembling the three components, the assembled device can be rotated from bottom to top with about 180 degrees to make the reagents flow into the liquid collection space through the diversion unit of the connector and thus contact the dipstick in the dipstick fixing space. By using the capillary action by the dipstick with one end attaching cotton, the PCR product is delivered from one end with the dipstick coated with coloring material toward the other end of the cotton dipstick. In this manner, the antigen carried by the products can specifically combine the antibody which is coated on the test paper, so the detection result can be observed through the detection space. By the techniques set forth in the present invention, the object can be achieved by performing the convection PCR and/or RT-PCR to detect the products in one single device. 
     These and other objectives of the present invention will no doubt become obvious to those of ordinary skill in the art after reading the following detailed description of the preferred embodiment that is illustrated in the various figures and drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  shows an exploded drawing and assembly drawing of the detection tube according to one preferred embodiment of the present invention. 
         FIG. 2A  is an outward appearance of the first tube from one side. 
         FIG. 2B  is a cross-sectional view taken along line BB′ in  FIG. 2A . 
         FIG. 3A  is an outward appearance of the first tube from another side. 
         FIG. 3B  is a cross-sectional view taken along line AA′ in  FIG. 3A . 
         FIG. 4  is a bottom view of the first tube. 
         FIG. 5A  is an outward appearance of the second tube. 
         FIG. 5B  is a cross-sectional view taken along line CC′ in FIG.  5 A. 
         FIG. 6A  is an outward appearance of the connector. 
         FIG. 6B  is a cross-sectional view taken along line DD′ in  FIG. 6A . 
     
    
    
     DETAILED DESCRIPTION 
     The following context and drawings illustrate the principles of the present disclosure according to one preferred embodiment of the present invention. As used herein, directional terms as may be used such as “horizontal,” “vertical,” “proximal,” “distal,” “front”, “rear”, “left,” “right,” “inner,” “outer,” “interior” and “exterior” relate to an orientation of the disclosed mixing device from the perspective of a typical user, and do not specify permanent, intrinsic features or characteristics of the device. 
     Please refer to  FIG. 1 . The reaction tube  1  in one preferred embodiment of the present invention includes a first tube  10 , a second tube  30 , and a connector  20  connecting the first tube  10  and the second tube  30 . 
     Please refer to  FIG. 1 ,  FIG. 2A ,  FIG. 2B ,  FIG. 3A ,  FIG. 3B  and  FIG. 4 . The first tube  10  in the previous embodiment is a transparency tube made of poly-carbonate, which comprises a first connection portion  101 , a holding portion  103 , an observation window  102  disposed between the first connection portion  101  and the holding portion  103 , and an detection space  104 . In the present embodiment, the outward appearance of the observation window  102  of the first tube  10  is a smooth and arced plane. The holding portion  103  is located at one end of the first tube  10 , which has two corresponding surfaces to be clipped by the user&#39;s finger for observing the reaction result. At the other end corresponding to the holding portion  103 , a first snap structure  105  is disposed in the inner side of the first tube  10 . In the present application, the first snap structure  105  includes at least an annular projection unit  1051  for connecting the connector  20 . The inner space of the first tube  10  is the detection space  104  which is used to accommodate a dipstick containing one cotton end. The detection space  104  has an oblong shape in its cross-section, so the detection space  104  contains a pair of parallel surfaces and a pair of curved surfaces. Thus, the outer surface of the first tube  10  and the inner surface walls of the first tube  10  together forms a flat convex lens. When the dipstick is placed in the detection space  104 , the features shown on the dipstick can be enlarged and are easy to watch. Besides, when placing the dipstick, the end containing the cotton is positioned at the other side far from the first snap structure  105 . 
     Please refer to  FIG. 1 ,  FIG. 5A  and  FIG. 5B . The second tube  30  is a hollow transparent tube having a portion with a greater inside diameter for connection the connector  20  and a capillary portion with a smaller inside diameter. The second tube  30  has a second connection portion  301  which has similar structure with that of the first connection portion  101  of the first tube  10 . A second snap structure  304  is formed inside the second tube  30  and contains at least an annular projection unit  3041  for connecting the connector  20 . The storing space  303  inside second tube  20  can accumulate the reagents required in the reaction. 
     As shown in  FIG. 1 ,  FIG. 6A  and  FIG. 6B , the connector  20  of the present embodiment is an elastomer preferably made of silica gel so the connector  20  has a hardness lower than the hardness of the first tube  10  and the second tube  30 . The connector  20  has a first portion  201  and a second portion  202  to respectively connect the first connection portion  101  of the first tube  10  and the second connection portion  301  of the second tube  30 . In detail, both the first portion  201  and the second portion  202  have a third snap structure  203  and in one preferred embodiment, the third snap structure  203  contains a plurality of annular projection units  2031 . When assembling the first tube  10 , the second tube  30  and the connector  20 , the annular projection unit  1051  of the first tube  10  and the annular projection unit  3041  of the second tube  30  can make the connector  20  slightly deformed, forming a compact assembling between the annular projection units of the first portion  201  and the second portion  202 , and the corresponding annular projection units  1051 ,  3041  of the first tube  10  and the second tube  30  so as to establish a tightly integrated sealing structure. 
     Please refer to  FIG. 6B , the first portion  201  of the connector  20  includes a diversion unit  204  and a liquid collection space  205 , and the second portion  202  includes a dipstick fixing space  206 , which is a long channel with an uniform caliber. The dipstick fixing space  206  has an outlet  207  used as an entrance for putting the dipstick there through. The liquid collection space  205  has an inlet adjacent to the diversion unit  204  and an outlet adjacent to the dipstick fixing space  206 , wherein the opening area of the outlet is greater than that of the inlet. By doing this, it can prevent inappropriate contact between the reagents and the dipstick and avoid the capillarity movement of the reagent toward the other side of the dipstick, which may result in unwanted reaction to the antibody coated on the dipstick. Further, it can also prevent the reagent flowing into the detection space  104  in the first tube  10 , which causes wrong interpretation of the result. 
     In the present embodiment, the diversion unit  204  is a diversion slope  2041  inclining toward the liquid collection space  205 . When the user converts the detection tube  1  with 180 degrees, for example, turns the detection tube in  FIG. 1  upside down, the diversion slope  2041  can guide the liquid in the second tube  202  to the liquid collection space  205 . Since the liquid collection space  205  is a hollow chamber for accumulating liquid and connected to the dipstick fixing space  206 , when the liquid flows into the liquid collection space  205 , the liquid would contact the dipstick and soon processes the PCR/RT-PCR detection reaction. Besides, as the inlet of the liquid collection space  205  (referred to the interface between the liquid collection space  205  and the diversion unit  204 ) is narrower than the outlet of the liquid collection space (referred to the interface between the liquid collection space  205  and the dipstick fixing space  206 ), the liquid can be guided along the predetermined direction. In increasing the reaction speed, the contact region of the liquid and dipstick is increased by forming the outlet of the liquid collection space  205  at the longer border of the dipstick fixing space  206 . By doing this, when the liquid flows out from the liquid collection space  206 , it can contact the dipstick with a bigger area, so the reaction speed can be increased. 
     When using the detection tube, the to-be-analyzed target gene, the specific binding antibody or other necessary are added into the second tube  30  and a thermal convection PCR/RT-PCR. Thereafter, the product of PCR/RT-PCR now contains the antigens called DIG or Avidin. Then, the dipstick that is coated by coloring material, specific binding antibody and absorbent cotton in its terminal ends is placed into the dipstick fixing space  206  of the connector  20 , following by assembly the connector  20  and the second portion  301  of the second tube  30  together to make the dipstick fix in the storing space  303  of the second tube  30 . In the present embodiment, the coloring material is gold (Au) gel, the specific binding antigen is DIG in which the corresponding antibody is Anti-DIG, the other specific binding antigen is Avidin in which its corresponding antibody is Biotin, and Biotin can bind Ag gel to form an Ag gel-Biotin complex. 
     After the thermal convection PCR/RT-PCR, there is no need to remove the reagent in the second tube  30 , instead, the connector  20 , the first tube  10  and the second tube  30  are assembled according to the structure in  FIG. 1  thereby forming a completely compact detection tube  1 . Thereafter, the detection tube  1  is turned 180 degrees, that is, making the structure if  FIG. 1  upside down, so the reagents of the thermal convection PCR/RT-PCR originally in the second tube would flow into liquid collection space  205  and the dipstick fixing space  206  via the guide slope  204  as to contact the dipstick in the dipstick fixing space  206 . Since there is a cotton pad at one terminal end of the dipstick, the reagents of the PCR/RT-PCR will gradually move to the terminal containing the cotton because of the capillary action. When the movement of the reagent is processing, Avidin will specifically combine Biotin to form Avidin-Biotin-Ag gel complex, which will further move to the place with Anti-DIG coating. Thus, it will combine with DIG and give color signals for detection. Consequently, the coloring can show the result of detection. 
     Those skilled in the art will readily observe that numerous modifications and alterations of the device and method may be made while retaining the teachings of the invention. Accordingly, the above disclosure should be construed as limited only by the metes and bounds of the appended claims.