Abstract:
A light detecting chip includes at least one detection region configured to accommodate a sample that is capable of emitting fluorescent light, and a light reflecting section configured to reflect at least a portion of the fluorescent light emitted from the sample in a direction toward a light detector.

Description:
CROSS REFERENCES TO RELATED APPLICATIONS 
     The present application claims priority to Japanese Patent Application JP 2009-187313 filed on Aug. 12, 2009, the entire content of which is hereby incorporated by reference. 
     BACKGROUND 
     The present disclosure relates to a light detecting chip. More particularly, the present disclosure relates to a light detecting chip and a light detecting device provided with the light detecting chip, which are used for analysis of gene expression, examination of infectious disease, gene analysis (such as SNP analysis), protein analysis, and cell analysis. 
     Comprehensive research and development on gene analysis, protein analysis, and cell analysis are going on in various fields including medical service, innovative drug development, clinical laboratory test, food industry, agriculture, engineering, legal medicine, and criminal identification. Conspicuous among them is a new technology of “lab-on-chip” which permits various reactions (for detection and analysis of nucleic acids, proteins, and cells) to take place in a channel or well of micro scale formed in a chip. It is now attracting attention because of its potential capacity for measuring biomolecules in a simple way. 
     The problem with the lab-on-chip technology is that mixing, reaction, separation, purification, and detection have to be carried out with an extremely small amount of sample in the channel or well of micro scale formed in a chip. For efficient detection and analysis, it is necessary to contrive good ways and means for chip design and their implementation. 
     For example, there is proposed in Japanese Patent Laid-open No. 2008-015770 (Patent Document 1) a chip with a micro channel formed therein. This chip is designed such that a reagent mixed with a thermally fusible binder is supported at a prescribed position in the micro channel. After introduction of a sample solution, the chip is heated so that the thermally fusible binder begins to melt at the position where it is supported. This leads to efficient dissolution and mixing and permits the subsequent reaction and analysis to take place at the same position. The result is that it is possible to reduce the number of spots for reaction in the micro channel, which leads to size reduction and cost reduction. 
     There is proposed in Japanese Patent Laid-open No. 2007-139744 (Patent Document 2) a fluorescence polarization assay which is capable of analysis with a very small amount of sample (about one-hundredth the amount used in the assay in the related art). The assay includes (1) a step of preparing fluorescent probe molecules and biomolecules, (2) a step of injecting them into the micro channel of a Lab-on-a-chip, thereby forming their complex, (3) a step of directing a beam of polarized light to the complex and measuring fluorescent polarization caused by the complex, and (4) a step of quantifying the fluorescent polarization and determining the degree of fluorescent polarization. 
     There is proposed in Japanese Patent Laid-open No. 2008-17779 (Patent Document 3) a Lab-on-chip which is composed of the following units arranged on a single substrate. A unit for preparation of nucleic acid, which is provided with a first electrode; a unit for introduction of a sample fluid into the nucleic acid preparing unit; a reaction unit communicating with the nucleic acid preparing unit through a channel, the reaction unit being provided with a second electrode; a unit for introduction of drug solution into the reaction unit; a unit for discharge of fluid from the reaction unit; a control circuit connected to the first and second electrodes; and a detecting circuit connected to the second electrode. This Lab-on-chip is capable of replication, synthesis, reaction, and detection of nucleic acids on a single substrate. 
     There is proposed in Japanese Patent Laid-open No. 2007-187582 (Patent Document 4) a biochip which is provided with detectors (such as working electrode, reference electrode, and counter electrode) and thin-film transistors. This biochip will find use as a biosensing device which is light, thin, short, small, and cheap and yet capable of high performance. It can also be detachably mounted on a biosensor provided with an ink jet head. 
     SUMMARY 
     A common way of analyzing a sample is by detection of light (particularly fluorescence) emitted from a sample introduced into a Lab-on-chip upon irradiation with light. It is still an important factor in the field of Lab-on-chip technology to efficiently detect light from an extremely small amount of sample, although many improvements and refinements have been made as mentioned above for more accurate analysis. 
     However, there are many instances which involve difficulties in efficient detection of light from an extremely small amount of sample because light (such as fluorescence) from a sample diverges in all directions (360°). Moreover, this situation is aggravated more by excitation light and self-emitting fluorescence from any substance contained in the sample, so that efficient detection of desired fluorescence alone is difficult. In fact, an ordinary optical detector can detect about 5% of fluorescence emitted from a sample. 
     It is a desired to provide a new technology capable of efficient detection of light emitted from a very small amount of sample. The present embodiments enable efficient detection of light from a very small amount of sample by modifying the structure of the chip used for light detection. 
     In an embodiment, a light detecting chip includes at least one detection region configured to accommodate a sample that is capable of emitting fluorescent light, and a light reflecting section configured to reflect at least a portion of the fluorescent light emitted from the sample in a direction toward a light detector. 
     In another embodiment, a light detecting device includes a light source configured to emit excitation light, at least one detection region configured to accommodate a sample capable of emitting fluorescent light, a light reflecting section configured to reflect at least a portion of the fluorescent light emitted from the sample in a direction toward a light detector, and a light detection section configured to receive at least a portion of the fluorescent light that is reflected by the light reflecting section. 
     The light reflecting section of the light detecting chips of the embodiments are not specifically restricted in shape. The light reflecting section may have, for example, a concave shape, a convex shape, or a planar shape. 
     The light detecting chip according to an embodiment may additionally have light transmission controlling section which blocks light being directed to the sample and transmits fluorescence emitted from the sample. 
     Owing to the structure of the embodiments, the light detecting chips are capable of reflecting that portion of fluorescence emitted from a sample which is scattered in the direction opposite to the direction in which fluorescence is detected. Therefore, it is capable of efficiently detecting light emitted from a very small amount of sample, and it contributes to improvement in the accuracy of analysis. 
     Additional features and advantages are described herein, and will be apparent from the following Detailed Description and the figures. 
    
    
     
       BRIEF DESCRIPTION OF THE FIGURES 
         FIG. 1  is a schematic sectional view showing the light detecting chip according to the first embodiment; 
         FIG. 2  is a schematic sectional view showing the light detecting chip according to the second embodiment; 
         FIG. 3  is a schematic sectional view showing the light detecting chip according to the third embodiment; 
         FIG. 4  is a schematic sectional view showing the light detecting chip according to the fourth embodiment; 
         FIG. 5  is a schematic sectional view showing the light detecting chip according to the fifth embodiment; 
         FIG. 6  is a schematic sectional view showing the light detecting chip according to the sixth embodiment; 
         FIG. 7  is a schematic sectional view showing the light detecting chip according to the seventh embodiment; 
         FIG. 8  is a schematic sectional view showing the light detecting chip according to the eighth embodiment; 
         FIG. 9  is a schematic conceptual drawing showing the light detecting device according to the first embodiment; 
         FIG. 10  is a schematic conceptual drawing showing the light detecting device according to the second embodiment; and 
         FIG. 11  is a schematic conceptual drawing showing the light detecting device according to the third embodiment. 
     
    
    
     DETAILED DESCRIPTION 
     Embodiments will be described below with reference to the accompanying drawings. The description below is divided into sections as follows.
         1. Light detecting chip  1 
           (1) Detection region  11     (2) Light reflecting section  12     (3) Light transmission controlling section  13     
           2. Light detecting device  10 
           (1) Light irradiating section  101     (2) Light detecting section  102     (3) Condenser lenses  103   a  and  103   b      (4) Optical filters  104   a  and  104   b      (5) Apertures  105   a ,  105   b , barrier   
               

     1. Light Detecting Chip  1   
       FIG. 1  is a schematic sectional view showing the light detecting chip  1  according to the first embodiment. The light detecting chip  1  has at least (1) detection region  11  and (2) light reflecting section  12 . It may optionally have (3) light transmission controlling section  13  according to need. 
     The light detecting chip  1  according to an embodiment will be formed from any material which is not specifically restricted. An adequate material is one which is commonly used for bioassay chips capable of light detection. Desirable materials include glass and transparent plastics such as polycarbonate, polyolefin, cycloolefin, acrylic, and silicon resins such as polydimethylsiloxane (PDMS), which are suitable for light detection. 
     The light detecting chip  1  has several sections as described below into detail. 
     (1) Detection Region  11   
     The detection region  11  is where there exists a sample to be analyzed and the sample is irradiated with excitation light E and fluorescence F emitted from the sample is detected. The detection region  11  is not specifically restricted in its structure so long as it permits detection of fluorescence F which is emitted from the sample by irradiation with excitation light E. It may be placed in the well W as shown in  FIG. 1  for the first embodiment. The detection region  11  may also be placed in the channel C as shown in  FIG. 2  for the second embodiment. Incidentally, the second embodiment shown in  FIG. 2  is designed such that there are a plurality of detection regions  11  in the channel C. However, it may be modified such that there exists one detection region  11  in one channel C. 
     Another possibility is that a plurality of detection regions  11  (not shown) are placed in the channel C and the wells W which are formed together in the substrate T as shown in  FIG. 3  for the third embodiment. 
     In the case where the detection region  11  is placed in the channel C, the channel C is not specifically restricted in its width, depth, and cross section. For example, a microchannel having a width smaller than 1 mm can be used for the light detecting chip  1  according to an embodiment. 
     The detection region  11  may function not only as a site for fluorescence detection but also as a site for amplification of nucleic acid, hybridization, and reaction among nucleic acids, proteins, and cells. In the case where the detection region  11  is placed in the channel C as shown in  FIG. 2  for the second embodiment, the process may proceed in such a way that the sample moves through the channel C while undergoing various reactions and the sample which has reached a prescribed position is examined for fluorescence. Moreover, in the case where the channel C and the wells W are formed together in the substrate T as shown in  FIG. 3  for the third embodiment, the process may proceed in such a way that the sample moves through the channel C while undergoing various reactions and the sample which has reached a prescribed well W is examined for fluorescence. Alternatively, the process may proceed in such a way that the sample undergoes reactions in each well W and the sample moving through the channel C is examined for fluorescence. 
     Incidentally, introduction of a sample into each detection region  11  may be accomplished in any known way without specific restrictions. For example, in the third embodiment shown in  FIG. 3 , the wells W and the channel C connected to them are formed on the substrate T so that the sample is introduced to each detection region  11  (not shown) through the channel C. 
     (2) Light Reflecting Section  12   
     The light reflecting section  12  is intended for reflection of fluorescence F emitted from the sample. It is placed at a position where the fluorescence is reflected back to the detection region  11  (in the direction D for fluorescence detection). 
     Since the sample emits fluorescence F in all directions (360°), fluorescence emitted in the direction opposite to the direction D for fluorescence detection is scattered without being detected. For this reason, the chip in the related art for light detection was hardly able to efficiently detect light from a very small amount of sample. By contrast, the chip for light detection according to an embodiment has the reflecting section  12  at a position which is opposite to the direction D for fluorescence detection. Therefore, it causes fluorescence emitted in the direction opposite to the direction D for fluorescence detection to be reflected back to the direction D for fluorescence detection. As the result, it detects more fluorescence F than the chip in the related art and hence it is able to efficiently detect fluorescence F emitted from a very small amount of sample, thereby improving the accuracy of analysis. 
     As mentioned above, the chip  1  for light detection according to an embodiment has the light reflecting section  12 , which is not specifically restricted in its structure so long as it is capable of reflecting fluorescence F emitted from the sample. For example, in the first and second embodiments shown in  FIGS. 1 and 2 , more than one light reflecting section  12  are arranged for more than one detection region  11 , and in the fourth embodiment shown in  FIG. 4 , one light reflecting section  12  is arranged for one detection region  11 . 
     As mentioned above, the chip  1  for light detection according to an embodiment has the light reflecting section  12 , which is not specifically restricted in its shape so long as it is capable of reflecting fluorescence F emitted from the sample. It may be a spherical concave mirror which is used in the first and second embodiments shown in  FIGS. 1 and 2 , or an aspherical concave mirror which is used in the fourth embodiment shown in  FIG. 4 , or a plane mirror which is used in the fifth embodiment shown in  FIG. 5 . 
     The light detecting chip  1  according to an embodiment may have the light reflecting section  12  which transmits excitation light E directed to the sample but reflects the fluorescence F emitted from the sample. This light reflecting section  12  permits the direction of light irradiation and light detection to be reversed as in the sixth embodiment shown in  FIG. 6 . The light irradiation and light detection in the reverse direction through the detection region  11  makes it possible to freely arrange the light irradiating section  101  for irradiation and the light detecting section  102  to detect fluorescence (not shown). 
     (3) Light Transmission Controlling Section  13   
     The light transmission controlling section  13  blocks light (excitation light E) directed to the sample but transmits fluorescence F emitted from the sample. It is not essential for the light detecting chip  1  according to an embodiment; however, it will improve the S/N ratio. 
     The light transmission controlling section  13  may be placed between the detection region  11  and the light reflecting section  12 , as in the seventh embodiment shown in  FIG. 7 , in which the light for irradiation and the light for detection are in the same direction. Also, it should preferably be placed at a position to which fluorescence is directed from the detection region  11 , as in the eighth embodiment shown in  FIG. 8 , in which the light for irradiation and the light for detection are in the opposite direction through the detection region  11 . 
     Thus, the light transmission controlling section  13  arranged described above prevents the excitation light E from scattering in the direction of fluorescence detection. The result is a decrease in noise due to the excitation light E and an improved S/N ratio. 
     2. Light Detecting Device  10   
       FIG. 9  is a schematic conceptual drawing showing the light detecting device  10  according to the first embodiment. The light detecting device  10  is composed at least of (1) the light irradiating section  101 , the detection region  11 , and (2) the light detecting section  102 , the light reflecting section. It may optionally have (3) the condenser lens  103 , (4) the optical filter  104 , (5) aperture  105 , and the barrier, according to need. These components will be described below in more detail. Incidentally, the detection region  11  and the light detecting section  12  function in the same way as mentioned above for the light detecting chip  1 . Therefore, their description is omitted hereunder. 
     (1) The Light Irradiating Section  101   
     The light irradiating section  101  is intended for irradiation to the sample with the excitation light E. 
     The light detecting device  10  according to an embodiment has the light irradiating section  101  which is placed anywhere without specific restrictions so long as it is capable of irradiating light to the sample. For example, in the first embodiment shown in  FIG. 9 , more than one light irradiating section  101  are arranged for individual detection regions  11 . This arrangement permits the individual detection regions  11  to be irradiated with the excitation light E varying in wavelength so that various detections can be accomplished at the same time. 
     Another possible arrangement (not shown) is such that a plurality of detection regions  11  are scanned with one light irradiating section  101  or irradiated with the excitation light E. 
     In the light detecting device  10  according to an embodiment, the light irradiating section  101  can employ any known light irradiating method without specific restrictions. For example, light irradiation will be accomplished by using any of LED (light emitting diode), semiconductor laser, and EL illumination, alone or in combination. 
     If a plurality of light irradiating section  101  are arranged for the individual light detection regions  11 , there are two ways of light irradiation. The first one is by simultaneous irradiation and simultaneous detection. This way saves time for data acquisition. The second one is by sequential irradiation and sequential detection. This way reduces noise from the juxtaposed light irradiating section  101 . 
     (2) Light Detecting Section  102   
     The light detecting section  102  is intended for detection of fluorescence F emitted from the sample. 
     The light detecting device  10  according to an embodiment has the light detecting section  102 , which is arranged in any way without specific restrictions so long as it is capable of detection of fluorescence F from the sample. For example, a plurality of light detecting section  102  may be arranged for individual detection regions  11  as in the first embodiment shown in  FIG. 9 . This arrangement permits simultaneous detection of fluorescence F emitted from the sample placed in each detection region  11 . 
     Another possible arrangement (not shown) is such that a plurality of detection regions  11  are scanned with one light detecting section  102  or irradiated sequentially with the excitation light E. This arrangement permits detection of fluorescence F emitted from the sample placed in each detection region  11 . 
     The light detecting device  10  according to an embodiment should preferably be constructed such that the light detecting section  102  is positioned opposite to the light irradiating section  101 , with the detection region  11  interposed between them. This construction permits free arrangement of the light irradiating section  101  and the light detecting section  102 . 
     The light detecting device  10  according to an embodiment may employ any known light detecting method without specific restrictions. These methods may use such areal imaging elements as PD (photodiode), CCD (charge coupled device), and CMOS (complementary metal oxide semiconductor), or a multichannel light detector which is composed of a plurality of light detectors arranged in an array. 
     (3) Condenser Lenses  103   a  and  103   b    
     The first embodiment shown in  FIG. 9  employs a plurality of condenser lenses  103   a  for excitation light, each of which is placed between the light irradiating section  101  and the light detection region  11 , to condense light from the light irradiating section  101 . The light detecting device  10  according to an embodiment does not essentially need the condenser lens  103   a  for excitation light. However, as in this embodiment, by providing the condenser lenses  103   a , it directs light accurately to the sample placed in the detection region  11 . 
     Moreover, this embodiment also employs a plurality of condenser lenses  103   b , each of which is placed between the light detection region  11  and the light detecting section  102 , to condense fluorescence F from the sample placed in the detection region  11  onto the light detecting section  102 . The light detecting device  10  according to an embodiment does not essentially need the condenser lens  103   b . However, as in this embodiment, by providing the condenser lenses  103   b , it intensifies signals such as fluorescence F, thereby improving the S/N ratio. 
     (4) Optical Filters  104   a  and  104   b    
       FIG. 10  is a schematic conceptual drawing showing the light detecting device  10  according to the second embodiment. This embodiment employs the optical filters  104   a  for excitation light, each of which is placed between the light irradiating section  101  and the detection region  11 . The light detecting device  10  according to an embodiment does not essentially need the optical filter  104   a  for excitation light. However, as in this embodiment, by providing the optical filters  104   a , it permits each detection region  11  to be irradiated selectively with excitation light having a desired wavelength. 
     Moreover, this embodiment also employs the optical filter  104   b  for light reception which is placed between each detection region  11  and each light detecting section  102 . The light detecting device  10  according to an embodiment does not essentially need the optical filter  104   b  for light reception. However, as in this embodiment, by providing the optical filters  104   b , desired wavelength can be received selectively out of fluorescence F emitted from the sample placed in each detection region  11 . 
     (5) Apertures  105   a ,  105   b , Barrier 
       FIG. 11  is a schematic conceptual drawing showing the light detecting device  10  according to the third embodiment. This embodiment employs the aperture  105   a  between each light irradiating section  101  and each detection region  11 . The light detecting device  10  according to an embodiment does not essentially need the aperture  105   a . However, as in this embodiment, it prevents light from each light irradiating mean  101  from irradiating other detection regions  11  (say, adjacent ones) than the corresponding one. This improves the S/N ratio. 
     Moreover, this embodiment also employs the aperture  105   b  between each detection region  11  and each light detecting section  102 . The light detecting device  10  according to an embodiment does not essentially need the aperture  105   b . However, as in this embodiment, it reduces crosstalk from other detection regions  11  (say, adjacent ones) than the corresponding one. This improves the S/N ratio. 
     The light detecting device  10  according to an embodiment may also employ, in addition to the apertures  105   a  and  105   b , the barrier (not shown) between the lenses so as to produce the same effect as mentioned above. 
     The light detecting chip  1  and the light detecting device  10  provided with it according to an embodiment is capable of not only examining the physical properties of the substance contained in the sample placed in the detection region  11  but also quantitatively analyzing the substance contained in the sample by electrophoresis, with the detection region  11  placed in the channel C. 
     Such analysis may be accomplished by forming a liquid sample into a flow cell (composed of a sample and a sheath flow holding it therein) and acquiring, by means of the light detecting section  102 , the intensity or image of fluorescence emitted from the substance flowing in the flow cell. The flow cell may be constructed in the same way as in the flow cytometry which is in actual use or under research and development. Detection of light from the sample flowing through the micro channel C makes it possible to sort fine particles, such as cells and nucleic acid, in the sample in the downstream of the channel according to the thus obtained information. 
     The present embodiments make it possible to efficiently detect light from a very small amount of light and is expected to improve the accuracy of analysis. 
     The technology mentioned above will contribute to improvement in analysis in various fields of medicine (pathology, tumor immunology, transplantation, genetics, regenerative medicine, and chemotherapy), innovative drug development, clinical laboratory test, food industry, agriculture, engineering, legal medicine, and criminal identification. 
     It should be understood that various changes and modifications to the presently preferred embodiments described herein will be apparent to those skilled in the art. Such changes and modifications can be made without departing from the spirit and scope of the present subject matter and without diminishing its intended advantages. It is therefore intended that such changes and modifications be covered by the appended claims.