Abstract:
An analysis tool suppressing background and improving detection sensitivity. In a first plate ( 11 ) is formed a first concavity ( 13 ) having, in the path of excitation light of a surface opposite to a bonding surface ( 20 ), a first bottom surface ( 13   a ), a first opening ( 13   b ), and a slanted surface ( 13   c ) widening from the edge of the first bottom surface ( 13   a ) towards the edge of the first opening ( 13   b ). In a second plate ( 12 ), having a flow path formed on the bonding surface ( 20 ), is formed a second concavity ( 14 ) having, in the path of excitation light of the surface opposite to the bonding surface, a second bottom surface ( 14   a ), a second opening ( 14   b ), and a slanted surface ( 14   c ) widening from the edge of the second bottom surface ( 14   a ) towards the edge of the second opening ( 14   b ). The first plate ( 11 ) is bonded to the second plate ( 12 ), and the first opening ( 13   b ) and the second opening ( 14   b ) are covered with a film ( 21, 22 ).

Description:
TECHNICAL FIELD 
       [0001]    The present invention relates to an analysis tool including a resin micro flow path chip and a micro analysis system including the analysis tool. 
       BACKGROUND ART 
       [0002]    In a current scientific field or medical field such as biochemistry and analytical chemistry, a micro analysis system is employed for rapidly testing and analyzing a small amount of substances such as protein or nucleic acid (for example, DNA) with accuracy. 
         [0003]    One of the micro analysis systems involves providing a micro flow path (hereinafter, referred to as “a flow path”) having a width and a depth of approximately several tens to two hundreds μm in the interior of the analysis tool, filling electrophoretic solution (i.e., buffer solution, gel) in the flow path, infusing samples from the end of the flow path and applying a voltage to the solution, and applying an electrophoresis to the samples to analyze the samples. 
         [0004]    In such a sample analysis, there is a known method of setting an analysis tool including a micro flow path in an analysis apparatus including an optical system unit capable of irradiating and receiving analysis light, applying electrophoresis to samples, irradiating light at a predetermined position in a flow path, and observing a fluorescence wavelength irradiated from the samples in the flow path, (see, for example, Patent literature 1). 
       CITATION LIST 
     Patent Literature 
       [0005]    PLT 1 Japanese Patent Application Laid-Open No. 9-288090 
       SUMMARY OF INVENTION 
     Technical Problem 
       [0006]    However, in the technique disclosed in the above described Patent literature 1, thick resin (substrate) in the path of light incident on the samples irradiates strong autofluorescence to increase background, which causes a problem of decreasing sample detection sensitivity. 
         [0007]    When fibers, human skins, floaters in air and the like (hereinafter, referred to as “dust”) are attached to the surface of resin (substrate) in the light path, and the distance between the dust and the focus of radiation light in the flow path is short, fluorescence irradiated from the dust is likely to be detected as noise and background is increased, thereby causing a problem of decreasing sample detection sensitivity. 
         [0008]    It is an object of the present invention to provide an analysis tool and a micro analysis system which reduce background and improve sample detection sensitivity. 
       Solution to Problem 
       [0009]    An analysis tool according to the present invention is an analysis tool configured by joining a first planar plate and a second planar plate, and employs a configuration in which the second plate has a flow path on a joint surface; and a pair of sealed spaces is located, across the flow path, in a path of excitation light incident on a sample at a predetermined position in the flow path and/or detection light from the sample irradiated with the excitation light, in a state in which the first plate and the second plate are joined. 
         [0010]    The micro analysis system according to the present invention employs a configuration to include the above described analysis tool. 
       Advantageous Effects of Invention 
       [0011]    According to the present invention, it is possible to reduce background and improve sample detection sensitivity. 
     
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         [0012]      FIG. 1  is a perspective view showing the shape of an analysis tool according to Embodiment  1  of the present invention; 
           [0013]      FIG. 2A  is a bottom view including the first recessed part in the first plate shown in  FIG. 1 ; 
           [0014]      FIG. 2B  is a cross-section view taken by line A-A in  FIG. 2A ; 
           [0015]      FIG. 3A  is a plane view including the second recessed part in the second plate in  FIG. 1 ; 
           [0016]      FIG. 3B  is a cross-section view taken by line B-B in  FIG. 3A ; 
           [0017]      FIG. 4  is a cross-section view including the first recessed part, the second recessed part and a flow path in a joined first plate and second plate; 
           [0018]      FIG. 5  is a perspective view showing the shape of an analysis tool according to Embodiment  2  of the present invention; 
           [0019]      FIG. 6A  is a plane view including the first recessed part and the second recessed part in the first plate in  FIG. 5 ; 
           [0020]      FIG. 6B  is a cross-section view taken by line A-A in  FIG. 6A ; 
           [0021]      FIG. 7A  is a bottom view including the third recessed part and the fourth recessed part in the second plate in  FIG. 5 ; 
           [0022]      FIG. 7B  is a cross-section view taken by line B-B in  FIG. 7A ; and 
           [0023]      FIG. 8  is a cross-section view including the first to fourth recessed parts, and a flow path in joined first plate  11  and second plate  12 . 
       
    
    
     DESCRIPTION OF EMBODIMENTS 
       [0024]    Embodiments of the present invention will now be described in detail with reference to the drawings. 
         [0025]    (Embodiment 1) 
         [0026]      FIG. 1  is a perspective view showing the shape of analysis tool  10  according to Embodiment 1 of the present invention. As shown in  FIG. 1 , analysis tool  10  is configured by joining resin planar first plate  11  to second plate  12 . 
         [0027]    First plate  11  and second plate  12  are made of resin material having high light-permeability such as acryl, polycarbonate, and polyolefin, and are desirably made of the same materials. 
         [0028]    First plate  11  has first recessed part  13  (see  FIG. 2 ) in the path of excitation light incident on samples in later described flow path  15 . Second plate  12  has cross-shaped groove  15 ′, and when second plate  12  is joined to later described first plate  11 , joint surface  20  of first plate  11  closes an opening of groove  15 ′ to define flow path  15  for flowing samples. Second plate  12  further has ports  16  to  19  to fill each end of flow path  15  with samples and electrophoretic solution, and second recessed part  14  (see  FIG. 3 ) in the path of radiation light (excitation light) to the samples. 
         [0029]    First plate  11  is joined to second plate  12 , for example, through adhesion with an organic adhesive or thermal compression bond. 
         [0030]      FIG. 2A  is a bottom view including first recessed part  13  in first plate  11 .  FIG. 2B  is a cross-section view taken by line A-A in  FIG. 2A . First plate  11  has first recessed part  13  on a surface opposite to joint surface  20  to second plate  12 , as shown in  FIG. 2 . First recessed part  13  has a bottom surface (first bottom surface  13   a ), an opening (first opening  13   b ) and an inclined surface (first inclined surface  13   c ) (the surface of a tapered cylinder) expanding from the outer edge of first bottom surface  13   a  toward the opening edge of first opening  13   b.    
         [0031]      FIG. 3A  is a plane view including second recessed part  14  in second plate  12 .  FIG. 3B  is a cross-section view taken by line B-B in  FIG. 3A . As shown in  FIG. 3 , second plate  12  has flow path  15  on joint surface  20  to first plate  11 , and has second recessed part  14  on a surface opposite to joint surface  20  to first plate  11 . Second recessed part  14  has a bottom surface (second bottom surface  14   a ), an opening (second opening  14   b ), and an inclined surface (second inclined surface  14   c ) (the surface of a tapered cylinder) expanding from the outer edge of second bottom surface  14   a  toward the opening edge of second opening  14   b  as with first recessed part  13 . 
         [0032]    In view of the above, providing a space with a plate being present in a path of excitation light by providing recessed parts in first plate  11  and second plate  12  can reduce the volume of resin, thereby minimizing the amount of autofluorescence irradiated with excitation light in a plate. Accordingly, the background can be minimized. 
         [0033]    The cross section areas of recessed parts  13  and  14  respectively provided in first plate  11  and second plate  12  are defined so as to be larger as the cross sections of the recessed parts are close to openings  13   b  and  14   b,  which can readily shape first plate  11  and second plate  12 . 
         [0034]      FIG. 4  is a cross-section view including first recessed part  13 , second recessed part  14 , and flow path  15  in joined first plate  11  and second plate  12 . Closing groove  15 ′ by joint surface  20  of first plate  11  defines flow path  15 . 
         [0035]    Opening  13   b  of first recessed part  13  provided in first plate  11  and opening  14   b  of second recessed part  14  provided in second plate  12  are respectively covered with films  21  and  22 . Films having minimized thicknesses are selected for films  21  and  22  not so as to increase the amount of autofluorescence in the path of excitation light. This allows each of recessed parts  13  and  14  to be sealed space and blocks ingress of dust into each of recessed parts  13  and  14 . Consequently, dust attached to the surface of analysis tool  10  is as away from a focus position as possible and an effect of fluorescence from dust irradiated with excitation light on detection sensitivity is reduced, thereby minimizing background. 
         [0036]    According to the present embodiment, the excitation light is entered such that the direction of an optical axis (OA) is vertical to the plane surfaces of plates  11  and  12  (for example, joint surface  20 ) as shown in  FIG. 4 . Samples labeled with a fluorescence reagent or the like in flow path  15  receive the excitation light and irradiate detection light such as fluorescence, the detection light being detected in a light receiving section (not shown). When the excitation light and the detection light have the same optical axis, the detection light is directed to the light receiving section through first recessed part  13  or second recessed part  14 . 
         [0037]    According to Embodiment 1, the first plate having the first recessed part in the path of excitation light is joined to the second plate having the flow path for flowing samples and the second recessed part at a position irradiated with the excitation light. This can reduce the volume of resin being present in the path of the excitation light, thereby minimizing the amount of autofluorescence from the resin irradiated with the excitation light. 
         [0038]    Covering each of openings in the first recessed part and the second recessed part with a film can block ingress of dust into each of recessed parts. Additionally, a surface on which dust is apt to be attached can be away from the focus of excitation light in the flow path. This can reduce an effect of fluorescence from dust irradiated with excitation light, on detection sensitivity. 
         [0039]    As a result, it is possible to minimize background and improve sample detection sensitivity. 
         [0040]    (Embodiment 2) 
         [0041]    A case has been described where the excitation light is entered vertically to the surface of the plate in Embodiment 1. A case will be described where the excitation light is entered horizontally to the surface of the plate, in other words, entered from the side of the plate in Embodiment 2 of the present invention. 
         [0042]      FIG. 5  is a perspective view showing the shape of analysis tool  30  according to Embodiment  2  of the present invention. As shown in  FIG. 5 , analysis tool  30  has sealed spaces  36  and  37  defined by joining first plate  11  to second plate  12 . 
         [0043]      FIG. 6A  is a plane view including first recessed part  31  and second recessed part  32  in first plate  11  in  FIG. 5 , and  FIG. 6B  is a cross-section view taken by line A-A in  FIG. 6A . As shown in  FIG. 6 , first plate  11  has first recessed part  31  having first opening  31   b  and second recessed part  32  having second opening  32   b,  on joint surface  20  to second plate  12  in the path of excitation light. First recessed part  31  and second recessed part  32  are shallow prismatic concaves having hexagonal bottom surfaces (first bottom surface  31   a  and second bottom surface  32   a ). 
         [0044]      FIG. 7A  is a bottom view including third recessed part  33  and fourth recessed part  34  in second plate  12 , and  FIG. 7B  is a cross-section view taken by line B-B in  FIG. 7A . As shown in  FIG. 7 , second plate  12  has third recessed part  33  and fourth recessed part  34  on joint surface  20  to first plate  11  across groove  15 ′. Third recessed part  33  and fourth recessed part  34  are shallow prismatic concaves having openings (third opening  33   b  and fourth opening  34   b ) on joint surface  20  and hexagonal bottom surfaces (third bottom surface  33   a  and fourth bottom surface  34   a ), as with first recessed part  31  and second recessed part  32 . 
         [0045]      FIG. 8  is a cross-section view including first to fourth recessed parts  31  to  34  and flow path  15  in joined first plate  11  and second plate  12 . Joining first plate  11  to second plate  12  allows the opening of first recessed part  31  and the opening of second recessed part  32  of first plate  11  to respectively face the opening of third recessed part  33  and the opening of fourth recessed part  34  of second plate  12 , thereby defining sealed spaces  36  and  37 . The opening of groove  15 ′ is closed by joint surface  20  of first plate  11  to define flow path  15 . 
         [0046]    The excitation light is entered such that the direction of an optical axis (OA) is horizontal to the plane surfaces of plates  11  and  12  (for example, joint surface  20 ) as shown in  FIG. 8 . Samples labeled with a fluorescence reagent or the like in flow path  15  receive the excitation light and irradiate detection light such as fluorescence, the detection light being detected in a light receiving section (not shown). When the excitation light and the detection light have the same optical axis, the detection light is directed to the light receiving section through sealed space  36  or  37 . 
         [0047]    According to Embodiment 2, the first plate having the first recessed part and the second recessed part at a position irradiated with excitation light is joined to the second plate having the flow path for flowing samples and the third recessed part and the fourth recessed part at a position irradiated with excitation light, across the flow path. The opening of the first recessed part and the opening of the second recessed part of the first plate respectively face the opening of the third recessed part and the opening of the fourth recessed part of the second plate, thereby defining sealed spaces. This can reduce the volume of resin being present in the path of excitation light, thereby minimizing the amount of autofluorescence from the resin irradiated with the excitation light, and can block ingress of dust into each recessed part, thereby reducing an effect of fluorescence from dust irradiated with excitation light, on detection sensitivity. Accordingly, it is possible to minimize background and improve sample detection sensitivity. 
         [0048]    Analysis tool  30  according to Embodiment  2  may have all of the first to fourth recessed parts  31  to  34  and groove  15 ′ on joint surface  20 , and the depth of the concaves from joint surface  20  can be reduced (shallowed) in comparison with Embodiment 1. This can simplify a mold structure and allow assembling to be easy. 
         [0049]    In the analysis tool, an effect of improving detection sensitivity according to the present invention can be obtained if a pair of sealed spaces across a flow path is located in the light path of at least one of an optical system for radiation of excitation light or the like and an optical system for detection of fluorescence or the like. A larger effect can however be obtained in a case where the pair of sealed spaces is defined in the light path of the optical system for radiation of excitation light. As with analysis tools  10  and  30  according to Embodiments 1 and 2, in a case where the optical system for radiation and the optical system for detection have the same optical axis, the present invention is further effective. When the optical system for radiation and the optical system for detection do not have the same axis (for example, a case where the axes of two optical systems are orthogonal to each other), a pair of sealed spaces across the flow path is desirably located in the light path of each optical system. 
         [0050]    Embodiments 1 and 2 have described a flow path defined by closing a groove on the second plate with the first plate, but the present invention is not limited thereto, and the flow path may be defined by joining the openings of grooves in both the first plate and the second plate. 
         [0051]    The shape of the pair of sealed spaces across the flow path is not limited to one shown in Embodiments 1 and 2. The pair of sealed spaces is desirably shaped such that the widths of the sealed spaces orthogonal to optical axes of the optical system for radiation and the optical system for detection are wide enough not to intercept light fluxes of each optical system, and a loss of light directed to a position irradiated with light (the focus of irradiated light) in a flow path and to a light receiving section for detection light can be minimized. 
         [0052]    The pair of sealed spaces according to the present invention need only minimize the amount of autofluorescence and block ingress of dust, and need not have airtightness. 
         [0053]    The disclosure of Japanese Patent Application No. 2010-165010 filed on Jul. 22, 2010, including the specification, drawings and abstract, is incorporated herein by reference in its entirety. 
       Industrial Applicability 
       [0054]    An analysis tool and a micro analysis system according to the present invention can be employed for an apparatus which tests and analyzes a small amount of substances in a scientific field or medical field such as biochemistry and analytical chemistry with accuracy. 
       Reference Signs List 
       [0055]      10 ,  30  Analysis tool 
         [0056]      11  First plate 
         [0057]      12  Second plate 
         [0058]      13 ,  31  First recessed part 
         [0059]      14 ,  32  Second recessed part 
         [0060]      15  Flow path 
         [0061]      16 - 19  Port 
         [0062]      20  Joint surface 
         [0063]      21 ,  22  Film 
         [0064]      33  Third recessed part 
         [0065]      34  Fourth recessed part 
         [0066]      36 ,  37  Sealed space