Abstract:
A biosensor that is capable of measuring a material contained in a sample is provided. The biosensor is configured to be inserted into a display device, and measures a material contained in the sample. The biosensor includes i) first and second substrates that are opposed to each other; ii) a sample guiding layer that has two sample injection openings and is located on the first substrate; iii) a first electrode that is located between the first substrate and the sample guiding layer; iv) a second electrode that is located between the second substrate and the sample guiding layer; v) a third electrode that is located between the sample guiding layer and the second substrate; and vi) a penetrated opening that penetrates the first substrate, the sample guiding layer, and the second substrate. The second electrode is spaced apart from the first electrode. The biosensor further includes i) a long edge, and ii) a short edge that shares a corner of the biosensor and neighbors the long edge. Each of the two sample injection openings is formed to correspond to the long edge and the short edge, respectively.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    This application claims priority to and the benefit of Korean Patent Application No. 10-2007-0022664 filed in the Korean Intellectual Property Office on Mar. 7, 2007, the entire contents of which are incorporated herein by reference. 
       BACKGROUND 
       [0002]    (a) Field of the Invention The present invention relates to a biosensor. More particularly, the present invention relates to a biosensor for detecting a target material from a blood sample. 
         [0003]    (b) Description of the Related Art 
         [0004]    In general, biosensors such as blood glucose meters use an electrochemical method. The electrochemical detecting method generally involves a structure in which an enzyme and a mediator are immobilized in a cell consisting of an anode and a cathode. When a sample is introduced to the inside of such a biosensor, the target material in the sample is oxidized by the catalytic action of an enzyme, while oxygen or an electron transfer medium is reduced. Here, the reduced oxygen or electron transfer medium is oxidized under compulsion by the voltage of the electrode to cause changes in electrons. A method of quantifying such changes in electrons and indirectly measuring the amount of the target material is referred to as an electrochemical detecting method. 
         [0005]    Since such biosensors use blood as a specimen, the biosensors are subject to interference depending on the types of blood. Furthermore, there is a need to develop a biosensor that uses smaller blood samples, and that can make measurements more rapidly, more conveniently, and more accurately. 
       SUMMARY 
       [0006]    The present invention has been made in an effort to provide a biosensor that is capable of using a smaller sample, and to provide accurate and convenient measurement while avoiding problems caused by various blood types and interference. 
         [0007]    According to an embodiment of the present invention, the biosensor is configured to be inserted into a display device and measures a material contained in the sample. The biosensor includes: i) first and second substrates that are opposed to each other; ii) a sample guiding layer that has two sample injection openings and is located on the first substrate; iii) a first electrode that is located between the first substrate and the sample guiding layer; iv) a second electrode that is located between the second substrate and the sample guiding layer; v) a third electrode that is located between the sample guiding layer and the second substrate; and vi) a penetrated opening that penetrates the first substrate, the sample guiding layer, and the second substrate. The second electrode is spaced apart from the first electrode. The biosensor further includes i) a long edge, and ii) a short edge that shares a corner of the biosensor and neighbors the long edge. The two sample injection openings are formed to correspond to the long edge and the short edge, respectively. 
         [0008]    The biosensor according to an embodiment of the present invention may further include a fourth electrode that is located on the first substrate to be exposed to the outside. The fourth electrode may be spaced apart from the first electrode along a direction that is configured for the biosensor to be inserted into the display device. The fourth electrode may be located to be closer to the display device than the first electrode when the biosensor is inserted into the display device. The display device may include i) a first connector pin, and ii) a second connector pin that has a greater length than that of the first connector pin and is spaced apart from the first connector pin to be extended parallel to the first connector pin. The display device may display an error message when the first connector pin is connected to the fourth electrode and the second connector pin is connected to the first electrode. The display device may include i) a first connector pin, and ii) a second connector pin that has a greater length than that of the first connector pin and is spaced apart from the first connector pin to be extended to be parallel to the first connector pin. The amount of the material may be displayed when the first and second connector pins are electrically connected to the third electrode. 
         [0009]    The first electrode may include i) a body portion, ii) a connecting portion that is connected to the body portion and neighbors the fourth electrode, and iii) a sample contacting portion that is connected to the connecting portion and is configured to contact the sample. The connecting portion may be configured to be electrically connected to the display device and to be extended along a direction in which the biosensor is inserted into the display device. The third electrode may include i) another body portion, and ii) another connecting portion that is connected to the other body portion. The other connecting portion may be configured to be electrically connected to the display device to be extended along a direction in which the biosensor is inserted into the display device. The connecting portion and the other connecting portion may be exposed to the outside in opposite directions to each other, and the second electrode is located between the connecting portion and the other connecting portion. The connecting portion and the other connecting portion may be located such that they are symmetrical to each other based on the second electrode along a direction that perpendicularly crosses the direction in which the biosensor is inserted into the display device. The sample guiding layer may further include two sample guiding channels that connect the two sample inlets with a hole. The second electrode may include two branched portions that meet with each of the two sample guiding channels. Each of the two branched portions may be spaced apart from the sample contacting portion, respectively. Each of the two branched portions may be located to be closer to the hole than the sample contacting portion along the two sample guiding channels, respectively. 
         [0010]    The sample guiding layer may further include a sample guiding channel that connects a sample inlet that corresponds to the long edge with the hole. The sample guiding channel may be bent. The sample inlet corresponding to the long edge may be located to be closer to the fourth electrode than the penetrated opening. The sample guiding layer may further include another sample guiding channel that connects a sample inlet that corresponds to the short edge with the hole. The sample guiding channel and the other sample guiding channel may be connected to the penetrated opening at both sides of the penetrated opening opposite to each other. 
         [0011]    The sample guiding layer may further include a sample guiding channel that connects the sample inlet with the penetrated opening. A mediator may be located in the sample guiding channel. The mediator may include i) an enzyme that reacts with the material, ii) an electron transfer medium that transfers electrons generated from the enzyme, and iii) a dispersion stabilizer that disperses and stabilizes the enzyme and the electron transfer medium. 
         [0012]    The enzyme may be at least one selected from the group consisting of glucose oxidase, glucose dehydrogenase, alcohol oxidase, alcohol dehydrogenase, pyrroloquinone (PQQ), and nicotinamide adenine dinucleotide/hydrogen (NAD/NADH). The electron transfer medium may be at least one selected from the group consisting of ferrocene, quinone, cobalt, nickel, ruthenium, a ferricyan compound, rhodium, palladium, osmium, iridium, platinum, hexaamineruthenium(III) chloride, derivatives including these, and transition metals. The dispersion stabilizer may be at least one selected from the group consisting of polyvinyl alcohol, polyethylene oxide, polyethylene glycol, carboxymethyl cellulose, hydroxymethyl cellulose, 2-hydroxyethyl cellulose, hydroxypropyl cellulose, microcrystalline cellulose, polyvinyl pyrrolidone, polyvinylidene fluoride, polymethyl methacrylate, and styrene butyl rubber. 
         [0013]    The mediator may further include a surfactant. The surfactant may include at least one selected from the group consisting of anionic surfactants, cationic surfactants, amphoteric surfactants, and nonionic surfactants. The anionic surfactant may include a soap or alkylbenzene sulfonate. The mediator may further include a phase transfer catalyst. The phase transfer catalyst may include at least one selected from the group consisting of phosphonium-based reagents, crown ether-based reagents, ammonium-based reagents, and polyethylene glycol (PEG)-based reagents. The mediator may further include glucose oxidase, hexaammineruthenium(III) chloride, carboxymethyl cellulose, microcrystalline cellulose, tricaprylmethyl ammonium chloride, t-octylphenoxypolyethoxyethanol, and a soap. 
         [0014]    According to another embodiment of the present invention, the biosensor includes: i) a first substrate; ii) an adhesive cover equipped with a plurality of sample inlets and located on the first substrate; iii) a second substrate overlying the adhesive cover; iv) at least one hole penetrating through the first substrate, the adhesive cover, and the second substrate, and formed to extend in the direction intersecting the sample inlet; v) a first electrode that is formed between the first substrate and the adhesive cover, along the circumference of the first substrate; vi) a second electrode that is formed between the first substrate and the adhesive cover to be enveloped by the first electrode; vii) a third electrode that is located between the adhesive cover and the second substrate; and viii) a non-conductive material layer that is located between the first electrode and second electrode and the adhesive cover, while exposing portions of the first electrode and the second electrode. The plurality of sample inlets include a first sample inlet that is formed on one side of the adhesive cover, and a second sample inlet that is formed on the other side of the adhesive cover. The first sample inlet and the second sample inlet are formed at positions that cross each other in an offset manner, and the channel is located between the first sample inlet and the second sample inlet. 
         [0015]    The at least one channel may include a plurality of channels, and the channels may be formed to extend parallel to each other. The first electrode may include a first sample measuring unit that is formed between the channels to extend in the direction parallel to the channels. The second electrode may include a second sample measuring unit that is formed apart from the first sample measuring unit by a certain distance and is parallel thereto. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0016]      FIG. 1  is a schematic perspective view of a biosensor according to a first embodiment of the present invention. 
           [0017]      FIG. 2  is a schematic exploded view of the biosensor of  FIG. 1 . 
           [0018]      FIG. 3  is a plan view of the biosensor of  FIG. 1 . 
           [0019]      FIG. 4  is a schematic view showing a state in which the biosensor of  FIG. 1  is correctly inserted into a display device. 
           [0020]      FIG. 5  is a schematic view showing a state in which the biosensor of  FIG. 1  is incorrectly inserted into a display device. 
           [0021]      FIG. 6  is a perspective view of a biosensor according to a second embodiment of the present invention. 
           [0022]      FIG. 7  is an exploded perspective view of the biosensor according to the second embodiment of the present invention. 
           [0023]      FIGS. 8 and 9  are plan views of the biosensor according to the second embodiment of the present invention. 
           [0024]      FIGS. 10 to 12  are schematic perspective views showing a method of cutting the biosensor according to the second embodiment of the present invention. 
           [0025]      FIG. 13  is an exploded perspective view of a biosensor according to a third exemplary embodiment of the present invention. 
           [0026]      FIG. 14  is an exploded perspective view of a biosensor according to a fourth embodiment of the present invention. 
           [0027]      FIG. 15  is an exploded perspective view of a biosensor according to a fifth embodiment of the present invention. 
           [0028]      FIG. 16  is an exploded perspective view of a biosensor according to a sixth embodiment of the present invention. 
           [0029]      FIG. 17  is a dynamic response curve showing the results of measurements taken in the experimental example of the present invention using a constant voltage and current method. 
           [0030]      FIG. 18  is a graph showing the principle of the measurement taken in the experimental example of the present invention using a constant voltage and current method. 
           [0031]      FIG. 19  is a graph showing the results of measurements made by varying the erythrocyte volume and the glucose concentration before compatibilizing the mediator. 
           [0032]      FIG. 20  is a graph showing the results of measurements made by varying the erythrocyte volume and the glucose concentration after compatibilizing the mediator. 
       
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS 
       [0033]    With reference to the accompanying drawings, embodiments of the present invention will be described in order for those skilled in the art to be able to implement it. As those skilled in the art would realize, the described embodiments may be modified in various different ways, all without departing from the spirit or scope of the present invention. Wherever possible, the same reference numbers will be used throughout the drawings to refer to the same or like parts. 
         [0034]    It will be understood that, although the terms first, second, third, etc., may be used herein to describe various elements, components, regions, layers, and/or sections, these elements, components, regions, layers, and/or sections should not be limited by these terms. These terms are only used to distinguish one element, component, region, layer, or section from another element, component, region, layer, or section. Thus, a first element, component, region, layer, or section discussed below could be termed a second element, component, region, layer, or section without departing from the teachings of the present invention. 
         [0035]    The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. As used herein, the singular forms “a”, “an”, and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms “comprises” and/or “comprising,” or “includes” and/or “including”, when used in this specification, specify the presence of stated features, regions, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, regions, integers, steps, operations, elements, components, and/or groups thereof. 
         [0036]    Spatially relative terms, such as “beneath”, “below”, “lower”, “above”, “upper”, “over”, and the like may be used herein for ease of description to describe one element or feature&#39;s relationship to another element(s) or feature(s) as illustrated in the figures. It will be understood that the spatially relative terms are intended to encompass different orientations of the device in use or operation in addition to the orientation depicted in the figures. For example, if the device in the figures is turned over, elements described as “below” or “beneath” other elements or features would then be oriented “above” the other elements or features. Thus, the exemplary term “below” can encompass both an orientation of above and below. The device may be otherwise oriented (rotated 90 degrees or at other orientations) and the spatially relative descriptors used herein are interpreted accordingly. 
         [0037]    Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. It will be further understood that terms, such as those defined in commonly used dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the context of the relevant art and the present disclosure, and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein. 
         [0038]      FIG. 1  is a schematic perspective view of the biosensor  600  according to a first embodiment of the present invention. 
         [0039]    As shown in  FIG. 1 , the  600  includes first and second substrates  610  and  630 , an adhesive cover  620 , a hole  640 , a sample guiding layer  660 , and first to fourth electrodes  650 ,  652 ,  654 , and  656 . In addition, the biosensor  600  may further include other elements as necessary. 
         [0040]    As shown in  FIG. 1 , the biosensor has a structure that is longitudinally extended along the y-axis direction. Therefore, the left portion of the biosensor  600  can be easily inserted into a display device  700  (shown in  FIG. 4 , the same hereinafter) along the −y-axis direction. The display device  700  electrically contacts the biosensor  600  to display an amount of materials contained in a sample. Accordingly, a user can easily know the amount of materials contained in the sample. For example, if the sample injected into the biosensor  600  is blood, the display device  700  can display an amount of blood sugar contained in the blood. 
         [0041]    As shown in  FIG. 1 , the first and second substrates  610  and  630  oppose each other. The first and second substrates  610  and  630  may be made of a hard material in order to maintain durability of the biosensor  600 . For example, the first and second substrates  610  and  630  may be made of plastic, polyester, polypropylene, or polycarbonate, or of ceramic, glass, and the like, and a polyethylene terephthalate (PET) film based on polyester can be preferably used. The biosensor  600  includes a long edge  6001  and a short edge  6003 . The long edge  6001  and the short edge  6003  share a corner of the biosensor  600  and neighbor each other. 
         [0042]    The first to fourth electrodes  650 ,  652 ,  654 , and  656  may be formed in the form of a paste or a plate, using various electrode materials including gold, platinum, silver, carbon, tungsten, nickel, copper, and the like, and a carbon paste is preferably used. The first to fourth electrodes  650 ,  652 ,  654 , and  656  can be patterned on the first or second substrates  610  and  630  using a method such as screen printing, photolithography, adhesion, vapor deposition, and the like, and are formed such that only the measuring site is distinguishable by means of an insulator film or an adhesive. Here, the first, second, and fourth electrodes  650 ,  652 , and  656  may be formed on the first substrate  610 , while the third electrode  654  may be formed on the second substrate  630 . 
         [0043]    If the sample enters into the biosensor  600 , the first to third electrodes  650 ,  652 , and  654  react with the sample and transfer flows of electrons. In this case, the first to third electrodes  650 ,  652 , and  654  function as an operating electrode, a counter electrode, or a recognition electrode. That is, the first electrode  650  functions as the operating electrode, the second electrode  652  functions as the recognition electrode, and the third electrode  654  functions as the counter electrode. 
         [0044]    The adhesive cover  620  is located between the first and third electrodes  650  and  654  to electrically insulate them from each other. The adhesive cover  620  may attach the first electrode  650  to the third electrode  654 . Adhesive applied on tape that forms the adhesive cover  620  may employ acrylics, urethanes, epoxies, rubber preparations, polyvinyl ether, or silicones, and the film base material may be a PET film. 
         [0045]    As shown in  FIG. 1 , the first, second, and fourth electrodes  650 ,  652 , and  656  are exposed outside toward a +z-axis direction. Here, the fourth electrode  656  is completely exposed to the outside while the first and second electrodes  650  and  652  are partially exposed to the outside. In addition, although not shown in  FIG. 1 , the third electrode  654  is partially exposed to the outside toward the −z-axis direction. Therefore, the first to fourth electrodes  650 ,  652 ,  654 , and  656  can be electrically connected to the display device  700  into which the biosensor  600  is inserted. 
         [0046]    As shown in  FIG. 1 , the sample guiding layer  660  has two sample inlets  622   a  and  622   b . The two sample inlets  622   a  and  622   b  include first and second sample inlets  622   a  and  622   b . The first sample inlet  622   a  is formed to correspond to the short edge  6103  of the first substrate  610  while the second sample inlet  622   b  is formed to correspond to the long edge  6101  of the first substrate  610 . Since the biosensor  600  has the two sample inlets  622   a  and  622   b , the biosensor  600  can be used two times by using each of the sample inlets  622   a  and  622   b.    
         [0047]    As shown in  FIG. 1 , since the biosensor  600  includes a hole  640 , air in the biosensor  600  can be ventilated to the outside through the hole  640 . Therefore, the samples injected into the biosensor  600  through the sample inlets  622   a  and  622   b  ventilate the air in the biosensor  600  through the hole  640  while they easily enter therein. Therefore, the material contained in the sample can be measured by using the first to third electrodes  650 ,  652 , and  654  contacting the sample. 
         [0048]      FIG. 2  schematically shows an exploded state of the biosensor  600  of  FIG. 1 . 
         [0049]    As shown in  FIG. 2 , the first electrode  650  includes a body portion  6501 , a connecting portion  6503 , and a sample contacting portion  6505 . The body portion  6501  is connected to the connecting portion  6503  and the sample contacting portion  6505 . The connecting portion  6503  neighbors the fourth electrode  656  and is extended along the −y-axis direction, that is, a direction along which the biosensor  600  is inserted into the display device  700 . The connecting portion  6503  is electrically connected to the display device  700 . The sample contacting portion  6505  contacts the sample and then generates an electric signal. 
         [0050]    As shown in  FIG. 2 , the second electrode  652  includes two branched portions  6522  and  6524 . The two branched portions  6522  and  6524  include first and second branched portions  6522  and  6524 . The first branched portion  6522  is extended along the x-axis direction while the second branched portion  6524  is extended along the y-axis direction. The first and second branched portions  522  and  6524  are spaced apart from the sample contacting portion  6505 . 
         [0051]    The samples having entered through the sample inlets  622   a  and  622   b  consequently contact the sample contacting portion  6505  and the branched portions  6522  and  6524 . Therefore, the first to third electrodes  650 ,  652 , and  654  are electrically connected to each other by an electrolyte in the sample. In this case, the second electrode  652  functions as a ground electrode. The material included in the sample is measured by a voltage difference between the first and third electrodes  650  and  654 . 
         [0052]    As shown in  FIG. 2 , the sample guiding layer  660  further includes sample guiding channels  624   a  and  624   b . The sample guiding channels  624   a  and  624   b  include first and second sample guiding channels  624   a  and  624   b . The first sample guiding channel  624   a  connects the first sample inlet  622   a  to the hole  640  while the second sample guiding channel  624   b  connects the second sample inlet  622   b  to the hole  640 . 
         [0053]    Although not shown in  FIG. 2 , a mediator is located in the first and second sample guiding channels  624   a  and  624   b  to react with the sample. The mediator includes an enzyme, an electron transfer medium, and a dispersion stabilizer. In addition, the mediator may further include a surfactant or a phase transfer catalyst. 
         [0054]    Here, the enzyme reacts with the material contained in the sample. One or more enzymes can be used depending on the target material to be measured, namely glucose, lactate, alcohol, cholesterol, creatinine, protein, amino acids, environmental materials, or industrial materials. For example, the enzyme may be a glucose oxidase or a glucose dehydrogenase for the purpose of measuring glucose, or an alcohol oxidase or an alcohol dehydrogenase for the purpose of measuring alcohol, PQQ, or NAD/NADH. 
         [0055]    The electron transfer medium transfers electrons generated from the enzyme. When the electron transfer medium is used, the formal potential is reduced as compared with the case of using oxygen, and thereby the effect of obstructing species is attenuated and more accurate results can be obtained. As for the electron transfer medium, organic or inorganic compounds including ferrocene, quinone, cobalt, nickel, ruthenium, a ferricyan compound, rhodium, palladium, osmium, iridium, platinum, derivatives containing these, and transition metals can be used. Preferably, hexaammineruthenium(III) chloride is used. 
         [0056]    The dispersion stabilizer disperses and stabilizes the enzyme and the electron transfer medium. As for the dispersion stabilizer, polyvinyl alcohol, polyethylene oxide, polyethylene glycol, carboxymethyl cellulose, hydroxymethyl cellulose, 2-hydroxyethyl cellulose, hydroxypropyl cellulose, microcrystalline cellulose, polyvinylpyrrolidone, polyvinylidene fluoride, polymethylmethacrylate, styrene butyl rubber, and the like can be used. Preferably, carboxymethyl cellulose and microcrystalline cellulose are used. 
         [0057]    The surfactant is used to confer an improved ability for homogeneous dispersion and solubility to the mediator and to improve the reaction rate. The surfactant simultaneously carries a non-polar terminal group (hydrophobic or lipophilic) and a polar terminal group (hydrophilic or water-soluble) within the same molecule. Also, with regard to the surfactant, a terminal group having affinity for organic substances envelops an organic substance that has no affinity for water, and a polar terminal group oriented outward imparts solubility to the molecule. 
         [0058]    The surfactants have properties such as detergency, emulsifiability, dispersibility, and the like. Thus, they can be widely used detergents, emulsifying agents, lubricants, disinfectants, dispersants, and the like, according to their properties. For the purpose of functional improvement, chemical agents and auxiliary agents can be used together with the surfactants. 
         [0059]    The surfactant may include at least one of anionic surfactants, cationic surfactants, amphoteric surfactants, and nonionic surfactants. The anionic surfactant ionizes in an aqueous solution to have an anion as the main body of the active agent. The anionic surfactant may be exemplified by a soap, an alkylbenzene sulfonate, or the like. The cationic surfactant ionizes to become a cation. The cationic surfactant may be exemplified by a higher amine halide, a quaternary ammonium salt, an alkylpyridinium salt, and the like. The amphoteric surfactant can ionize to become either a cation or an anion. The amphoteric surfactant may be exemplified by an amino acid and the like. The nonionic surfactant does not ionize. The nonionic surfactant may be exemplified by polyethylene glycols and the like. 
         [0060]    The phase transfer catalyst enhances the reaction rate of the mediator and allows low-temperature applications, while it is still effective in reactions involving organic compounds. The phase transfer catalyst is used in the syntheses of inorganic substances that are not soluble in organic solvents, and of organic compounds, and can be usefully used since the phase transfer reaction between water and a solvent occurs homogeneously at normal temperature and normal pressure in an open system. The catalyst can also be used effectively in a liquid-liquid heterogeneous system. In addition, since the fluidity improved by phase transfer is less affected by the changes of the blood type, electromigration can be improved and preserved. For such a phase transfer catalyst, reagents based on phosphonium, crown ether, ammonium, polyethylene glycol, and the like may be used. 
         [0061]    Furthermore, the mediator may further include glucose oxidase, hexaammineruthenium(III) chloride, carboxymethyl cellulose, microcrystalline cellulose, tricaprylmethyl ammonium chloride, t-octylphenoxypolyethoxyethanol, or a soap as an auxiliary agent. An amount of the auxiliary agent is in a range from 0.01 wt % to 20 wt %. For example, 0.01 to 20% of a detergent that is a soap, a cationic detergent, and a free fatty acid (C 6-20 ) can be added to the mediator. A soap molecule refers to a product having amphotericity (polar and non-polar moieties), which is obtained by subjecting nonionic surfactants such as aliphatic alcohols, acids, amidephenols, alkylphenols, and oxides thereof to an interspecies reaction or a homogeneous reaction. A cationic detergent may be an ammonium compound such as an alkylmethylammonium halide. A free fatty acid (C 6-20 ) functions as a protein adsorption preventing agent and as a solubility enhancer. 
         [0062]    As shown in  FIG. 2 , the first and second sample guiding channels  624   a  and  624   b  are connected to both sides of the hole  640  opposite to each other. That is, the first and second sample guiding channels  624   a  and  624   b  are connected to both sides of the hole  640  opposite to each other along the y-axis direction. Therefore, the biosensor  600  can be used two times by cutting the hole  640 . 
         [0063]    As shown in  FIG. 2 , the first branched portion  6522  is located to be closer to the hole  640  than the sample contacting portion  6505  along the first sample guiding channel  624   a . In addition, the second branched portion  6524  is located to be closer to the hole  640  than the sample contacting portion  6505  along the second sample guiding channel  624   b . Therefore, the samples entering into each of the sample guiding channels  624   a  and  624   b  through the sample inlets  622   a  and  622   b  can consequently contact the sample contacting portion  6505  and the branched portions  6522  and  6524  while ventilating air existing in the sample guiding channels  624   a  and  624   b  toward the hole  640 . 
         [0064]    The sample guiding layer  660  has a suitable thickness. Therefore, an amount of the samples entering into the biosensor  600  through the sample inlets  622   a  and  622   b  can be suitably controlled. Since a voltage difference between the first and third electrodes  650  and  654  is changed to be dependent on an amount of the sample, the amount of the sample is suitably controlled by controlling the thickness of the sample guiding layer  660 . 
         [0065]    As shown in  FIG. 2 , the adhesive cover  620  attaches the first and second substrates  610  and  630  to each other. The first, second, and fourth electrodes  650 ,  652 , and  656  are formed on the first substrate  610 , while the third electrode  654  is formed on the second substrate  630 . Therefore, a short circuit of the electrodes can be prevented by using an insulating material for manufacturing the adhesive cover  620 . 
         [0066]    The third electrode  654  includes a connecting portion  6541  extended along the y-axis direction. Since the connecting portion  6541  is exposed to the outside toward a direction opposite to a direction of the connecting portion  6503  of the first electrode  650 , that is, the −z-axis direction, it can be electrically connected to the display device  700  into which the biosensor  600  is inserted. 
         [0067]      FIG. 3  is a plan view of the biosensor  600  of  FIG. 1 .  FIG. 3  schematically shows a state in which the biosensor  600  of  FIG. 1  is cut to be used. 
         [0068]    As shown in  FIG. 3 , the biosensor  600  can be used two times by cutting the biosensor  600  along a line III-III extended in the x-axis direction, which passes through the hole  640 . A method for using the biosensor  600  is explained as follows. 
         [0069]    First, a sample is injected into the first sample inlet  622   a  formed at a short edge  6003  of the biosensor  600 . For example, after blood is drawn from a finger by piercing it, the finger is contacted with the first sample inlet  622   a . When the biosensor  600  is used, it is more convenient to contact the finger with the short edge  6003  of the biosensor  600  than the long edge  6001  thereof. In this case, the blood enters into the biosensor  600  through the first sample inlet  622   a  and flows through the first sample guiding layer  624   a  denoted by a dotted line. The air existing in the first sample guiding layer  624   a  is pressed by the blood and is then ventilated toward the hole  640 . 
         [0070]    As described above, since the first sample guiding layer  624   a  meets with the first electrode  650  (shown in  FIG. 2 , the same hereinafter), the second electrode  652 , and the third electrode  654  (shown in  FIG. 2 , the same hereinafter), the first to third electrodes  650 ,  652 , and  654  are electrically connected to each other, and thereby the material contained in the sample can be measured. 
         [0071]    Next, the biosensor  600  is cut along the line III-III. The biosensor  600  can be cut by using a cutter, scissors, or a knife. A cut lower portion of the biosensor  600  is discarded. When the biosensor  600  is reused, the finger is contacted with the second sample inlet  622   b  after blood is drawn from the finger. In this case, the blood enters into the biosensor  600  through the second sample inlet  622   b  and flows through the second sample guiding layer  624   b  denoted by a dotted line. The air existing in the second sample guiding layer  624   b  is pressed by the blood and is then ventilated toward the hole  640 . 
         [0072]    As described above, since the second sample guiding layer  624   b  meets with the first electrode  650 , the second electrode  652 , and the third electrode  654 , the first to third electrodes  650 ,  652 , and  654  are electrically connected to each other, and thereby the material contained in the sample can be measured. 
         [0073]    As shown in  FIG. 3 , the second sample guiding layer  624   b  is bent. That is, the second sample inlet  622   b  formed at a long edge  6001  of the biosensor  600  is connected to the hole  640  and the second sample guiding layer  624   b  to ventilate the air existing in the biosensor  600  during injection of the sample. Since a structure of the electrode should be simple to meet the second sample guiding layer  624   b  with the first to third electrodes  650 ,  652 , and  654 , the second sample guiding layer  624   b  can be formed to be bent. Particularly, since the biosensor  600  is cut to be reused, the second sample inlet  622   b  should be located to be higher than the line III-III. Therefore, the second sample inlet  622   b  is located to be closer to the fourth electrode  656  than the hole  640 . 
         [0074]    As shown in  FIG. 3 , the connecting portion  6503  of the first electrode  650 , the second electrode  652 , and the connecting portion  6541  of the third electrode  654  are located side by side along the x-axis direction. Here, the second electrode  652  is located between the connecting portion  6503  of the first electrode  650  and the connecting portion  6541  of the third electrode  654 . The connecting portion  6503  of the first electrode  650  and the connecting portion  6541  of the third electrode  654  are located in symmetrical positions based on the second electrode  652  along a direction perpendicularly crossing an inserting direction of the biosensor  600  into the display device  700 , that is, the x-axis direction. Therefore, it is easily determined whether the biosensor  600  is correctly inserted into the display device  700 . This will be explained in detail with reference to  FIGS. 4 and 5  below. 
         [0075]      FIG. 4  shows a state in which the biosensor  600  is correctly inserted into the display device  700 . An enlarged circle of  FIG. 4  shows a magnified end portion of the biosensor  600  inserted into the display device  700 . 
         [0076]    As shown in  FIG. 4 , the display device  700  includes a display window  7001 . Therefore, when the biosensor  600  is correctly inserted into the display device  700  along the −y-axis direction, the measurement amount of the material is displayed on the display window  7001 . Meanwhile, the display device can make a signal sound in addition to a method of showing a message on the display window  7001 . 
         [0077]    As shown in the enlarged circle of  FIG. 4 , the display device  700  includes first to fourth connector pins  7003 ,  7005 ,  7007 , and  7009 . Parts of the first and second connector pins  7003  and  7005  located below the second substrate  630  are denoted by dotted lines for convenience. In addition, the third electrode  654  located below the second substrate  630  is also denoted by a dotted line for convenience. 
         [0078]    As shown in the enlarged circle of  FIG. 4 , the second connector pin  7005  is extended to be spaced apart from the first connector pin  7003 . The second connector pin  7005  has a greater length than that of the first connector pin  7003 . Both of the first and second connector pins  7003  and  7005  electrically contact the third electrode  654 . 
         [0079]    A circuit of the display device  700  is structured to operate only when both of the first and second connector pins  7003  and  7005  connect to the third electrode  654 . Since a circuit structure of the display device  700  can be easily understood by the skilled art, a detailed description thereof is omitted. 
         [0080]    Meanwhile, the third connector pin  7007  is connected to the first electrode  650  and thereby transfers an electric signal. Since an end portion of the third connector pin  7007  is conductive, the third connector pin  7007  passing above the fourth electrode  656  is not electrically connected to the fourth electrode  656 . An amount of the material is displayed on the display window  7001  of the display device  700  depending on the voltage difference between the second and third connector pins  7705  and  7707 . Meanwhile, the fourth connector pin  7009  is electrically connected to the second electrode  652  to transfer a timing signal. 
         [0081]    It is necessary to prevent the biosensor  600  from being misused by a regulation of the food and drug administration (FDA). Therefore, in an embodiment of the present invention, the display device  700  displays an error message when the biosensor  600  is incorrectly inserted into the display device  700 . This will be explained in detail below with reference to  FIG. 5 . 
         [0082]      FIG. 5  schematically shows a state in which the biosensor  600  is incorrectly inserted into the display device  700 . An enlarged circle of  FIG. 5  shows a magnified end portion of the biosensor  600  inserted into the display device  700 . Since the biosensor  600  and the display device  700  of  FIG. 5  are the same as those of  FIG. 4  except that the biosensor  600  is overturned, like elements are referred to by like reference numerals and detailed descriptions thereof are omitted. 
         [0083]    As illustrated in  FIG. 5 , when the overturned biosensor  600  is inserted into the display device  700 , the fourth electrode  656  is located to be closer to the display device  700  than the first electrode  650 . Since the length of the first connector pin  7003  is different from that of the second connector pin  7005 , the first connector pin  7003  is electrically connected to the fourth electrode  656  while the second connector pin  7005  is electrically connected to the first electrode  650 . Since an end portion of the second connector pin  7005  is conductive, the second connector pin  7005  passing above the fourth electrode  650  is electrically insulated from the fourth electrode  650 . 
         [0084]    Here, since the fourth electrode  656  is not electrically connected to the first electrode  650 , the first connector pin  7003  cannot transfer an electric signal to the display device  700 . Meanwhile, the second connector pin  7005  is electrically connected to the fourth electrode  650  and thereby transfers an electric signal to the display device  700 . Here, the display device  700  has a circuit structure to operate only when electric signals enter from the first and second connector pins  7003  and  7005 , and thereby the display device  700  does not operate and an error message is displayed on the display window  7001 . On the contrary, the display device  700  can emit an error message by making a warning sound. 
         [0085]      FIG. 6  is a perspective view of a biosensor  100  according to a second embodiment of the present invention. Since the structure of the biosensor  100  according to the second embodiment of the present invention is similar to that of the biosensor  600  of  FIG. 1 , detailed descriptions of the same parts are omitted. 
         [0086]    As shown in  FIG. 6 , the biosensor  100  includes a first substrate  10 , a first electrode  50  and a second electrode  52  formed on the first substrate  10 , an adhesive cover  20  equipped with a sample inlet  22  and located on the first substrate  10 , and a second substrate  30  overlying the adhesive cover  20 . Furthermore, the biosensor  100  includes a hole  40  that is formed to penetrate through the first substrate  10 , the adhesive cover  20 , and the second substrate  30 . The sample inlet  22  includes a first sample inlet  22   a  that is provided on one side of the biosensor  100  and a second sample inlet  22   b  that is provided on the other side, and the hole  40  is formed in the direction intersecting the first sample inlet  22   a  and the second sample inlet  22   b . The hole  40  is located between the first sample inlet  22   a  and the second sample inlet  22   b.    
         [0087]      FIG. 7  is an exploded perspective view of a biosensor  100  according to the second embodiment of the present invention. Hereinafter, each of the constituent elements of the biosensor  100  will be described in more detail with reference to  FIG. 7 . 
         [0088]    As shown in  FIG. 7 , the biosensor  100  includes a mediator  62  that is introduced on an electrode defined to have a specific site among the electrodes. The mediator  62  includes first and second mediators  62   a  and  62   b . In the second embodiment of the present invention, the mediator  62  is immobilized on a specific portion of the first electrode  50 . The mediator  62  contains an enzyme that reacts with a material contained in the sample to be introduced through the sample inlet  22 , an electron transfer medium that transfers electrons generated from the enzyme, and a dispersion stabilizer that disperses and stabilizes the enzyme and the electron transfer medium. The components of the mediator  62  are the same as those of the mediator explained in the first embodiment of the present invention. 
         [0089]    Hole portions  40   a  to  40   e , which are parts of the hole  40 , are formed in the first substrate  10  and the second substrate  30 . The first substrate  10  and the second substrate  30  may be formed of a material that is the same as that of the first and second substrates  610  and  630  of the biosensor  600  of  FIG. 2 . 
         [0090]    The adhesive cover  20 , which is located between the first substrate  10  and the second substrate  30 , forms the sample inlet  22  while adhering the first substrate  10  and the second substrate  30  to each other. Here, a hole portion  40   c  that is a part of the hole  40  is also formed in the adhesive cover  20 . The adhesive cover  20  may be formed from a film-based tape that has an adhesive applied on either side or both sides thereof. The adhesive applied on the tape that forms the adhesive cover  20  may employ acrylics, urethanes, epoxies, rubber preparations, polyvinyl ether, or silicones, and the film base material may be a PET film. 
         [0091]    The biosensor  100  further includes a third electrode  54  that is located between the adhesive cover  20  and the second substrate  30 . In addition, the first electrode  50  is formed on the first substrate  10  along the circumference of the first substrate  10 , and the second electrode  52  is located to be enveloped by the first electrode  50  and is formed to envelop the holes formed in the first substrate  10 . These electrodes transfer the flow of electrons generated by a reaction occurring after the introduction of a sample. Here, each of the electrodes acts as an operating electrode, a counter electrode, or a recognition electrode, and if necessary, three or more electrodes may be formed. According to the second embodiment of the present invention, as an example, the first electrode  50  serves as an operating electrode, the second electrode  52  serves as a recognition electrode, and the third electrode  54  serves as a counter electrode. Meanwhile, a hole portion  40   d  that is a part of the hole  40  is also formed in the third electrode  54 . 
         [0092]    The first electrode  50 , the second electrode  52 , and the third electrode  54  may be formed in the form of a paste or a plate, using various electrode materials including gold, platinum, silver, carbon, tungsten, nickel, copper, and the like, and a carbon paste is preferably used. The electrodes  50 ,  52 , and  54  can be patterned on a substrate using a method such as screen printing, photolithography, adhesion, vapor deposition, and the like, and are formed such that only the measuring site is distinguishable by means of an insulator film or an adhesive. 
         [0093]    The biosensor  100  further includes a non-conductive material layer  60  between the first electrode  50  and second electrode  52  and the adhesive cover  20 , so that only parts of the first electrode  50  and the second electrode  52  are used as the measuring site. A hole portion  40   b  that is a part of the hole  40  is also formed in the non-conductive material layer  60 . 
         [0094]    As described above, the hole  40  is formed such that the hole portions  40   a  to  40   e , which are respectively formed at the same positions on the first substrate  10 , the non-conductive material layer  60 , the adhesive cover  20 , the third electrode  54 , and the second substrate  30 , together penetrate through the biosensor  100  as a whole. Such a hole  40  is formed in the direction intersecting the sample inlet  22 . For example, the hole  40  is formed to extend in the direction perpendicular to the first sample inlet  22   a  and the second sample inlet  22   b , which are formed parallel to each other. 
         [0095]    As the hole  40  is provided as such, the samples injected through the first sample inlet  22   a  and the second sample inlet  22   b  are prevented from flowing into the other sample inlet  22 . Thus, by using the different sample inlets  22  separately, the amount of sample can be reduced to half, as compared to the case where the hole  40  is not included. Therefore, the biosensor  100  having a structure as described above can be readily applied to electrochemical biosensors that require small amounts of samples. 
         [0096]    According to the second embodiment of the present invention, the first sample inlet  22   a  and the second sample inlet  22   b  are located to cross each other in an offset manner. Thus, a measurement is performed when a sample is injected through the second sample inlet  22   b , then the portion where the second sample inlet  22   b  is formed is cut, and another measurement can be performed using the first sample inlet  22   a . On the other hand, the shapes of the sample inlets  22  and the hole  40  depicted in  FIGS. 6 and 7  are intended only to illustrate the present invention, and the shape, slope, dimensions, and width may be varied in accordance with different conditions. 
         [0097]      FIGS. 8 and 9  are plan views of the biosensor according to the second embodiment of the present invention, and depict a biosensor  100  before cutting and a biosensor  100   a  after cutting, respectively. As depicted therein, the biosensor  100  is cut along the line indicated by the line A-A′ so that the portion where the second sample inlet  22   b  is placed is cut off, and the remaining portion where the first sample inlet  22   a  is placed is reused. 
         [0098]      FIGS. 10 to 12  are schematic diagrams sequentially illustrating the process of cutting a biosensor having the above-described structure. As depicted therein, a portion of the biosensor is inserted into a cutting device  70 , and a cutter  70   a  included in the cutting device  70  is used to cut the biosensor  100 . Here, the cutting device  70  may be located inside or outside a measurement display device  72 , or may be provided separately from the measurement display device  72 .  FIGS. 10 to 12  illustrate an example in which the cutting device is located inside the measurement display device  72 . 
         [0099]      FIG. 13  is an exploded perspective view of a biosensor  200  according to a third embodiment of the present invention. As shown in  FIG. 13 , the biosensor  200  has electrodes formed only between a first substrate  210  and an adhesive cover  220 . That is, according to the third embodiment of the present invention, only a first electrode  250  and a second electrode  252  are formed on the first substrate  210  to act as an operating electrode and a counter electrode, respectively. Since the remaining constitution of the third embodiment of the present invention is identical to that of the first embodiment of the present invention, a description thereof will be omitted herein. 
         [0100]      FIG. 14  is an exploded perspective view of a biosensor  300  according to a fourth embodiment of the present invention. As depicted in  FIG. 14 , in the biosensor  300  according to the fourth embodiment of the present invention, an electrode  350  covering approximately the entire surface of a first substrate  310 , excluding a hole  340 , is formed on the first substrate  310 , and another electrode  354  covering approximately the entire surface of an adhesive cover  320 , except the hole  340 , is formed between the adhesive cover  320  and a second substrate  330 . Here, either one of the two electrodes serves as an operating electrode while the other serves as a counter electrode, thus constituting opposing electrodes. 
         [0101]    In this case, even if the width of the electrodes  350  and  354  as a whole is set to 0.5 cm or greater, the width of the channel can be laterally adjusted to allow a sample to be introduced in an amount of only half the conventional amount or less. 
         [0102]    Furthermore, different mediators intended for different purposes can be introduced through sample inlets  322  placed on both sides of the biosensor  300 , so that two or more different target materials can be detected. The measuring unit sensor manufactured in an arbitrary form according to the fourth embodiment can be directly modified with an enzyme, an antibody, or a molecule-recognition material on the electrode, or can be modified first and then be introduced onto the electrode, or alternatively, membranes containing various mediators can also be introduced. Since the remaining constitution of the fourth embodiment of the present invention is identical to that of the first embodiment of the present invention, a description thereof will be omitted herein. 
         [0103]      FIG. 15  is an exploded perspective view of a biosensor  400  according to a fifth embodiment of the present invention. As depicted in  FIG. 15 , the biosensor  400  according to the fifth embodiment of the present invention includes a plurality of holes  440 , and the plurality of holes  440  are formed to extend parallel to each other. Thus, a first electrode  450  having a shape with many branches extending out from one stem is located between a first substrate  410  and an adhesive cover  420 , and a second electrode  454  having a corresponding shape is located between the adhesive cover  420  and a second substrate  430 . Here, the first electrode  450  and the second electrode  454  may serve as an operating electrode and a counter electrode, respectively. 
         [0104]    According to the fifth embodiment of the present invention, electrode cells  450   a  and  454   a  formed from the first electrode  450  and the second electrode  454  into many branches can be respectively used as measuring cells for samples. In this case, more electrode cells  450   a  and  454   a  can be formed in parallel, and the position, path, or shape of sample inlets  422  can be altered, or alternatively the limited portions of the electrode cells  450   a  and  454   a  can be adjusted vertically to form gaps therebetween. 
         [0105]    In addition,  FIG. 16  is an exploded perspective view of a biosensor  500  according to a sixth embodiment of the present invention. In the biosensor  500  according to the sixth embodiment of the present invention, two electrodes are formed on a first substrate  510 . That is, the biosensor  500  of the sixth embodiment of the present invention includes a first electrode  550  that is formed on the first substrate  510 , an insulating layer (not shown in the drawing) that is formed on the first electrode  550 , and a second electrode  552  that is formed on the insulating layer. Furthermore, the first electrode  550  includes a first sample measuring unit  550   a  that is formed between holes  540  so as to extend in a direction parallel to the holes  540 , and the second electrode  552  includes a second sample measuring unit  552   a  that is placed apart from the first sample measuring unit  550   a  by a certain distance and formed in parallel. Thus, the first electrode  550  and the second electrode  552  can serve as an operating electrode and a counter electrode, respectively. 
         [0106]    Hereinafter, the present invention will be described in detail with reference to an experimental example. The following experimental example is intended only to illustrate the present invention, and the present invention is not limited thereto. 
       Experimental Example 
       [0107]    A biosensor identical to that of the second exemplary embodiment of the present invention was produced. An operating electrode and a recognition electrode formed of a conducting carbon paste were formed on the first substrate, and a counter electrode was formed simultaneously with electrode connections on the second substrate by a screen printing method. Next, the assembly was dried in a dry oven at 100° C. for 20 minutes. Then, while a specific portion to be used as an electrode cell was left intact, the remaining portion was applied with an insulating paste. 
         [0108]    Also, a channel having a size of 0.8×1 mm was formed in the mid-portion of the electrode and the adhesive cover by pressing in a mold that was processed in advance. Subsequently, a mediator was immobilized on the electrode cell, and then, while leaving the contacting portion, the remaining portion was attached to the adhesive cover to form a sample inlet. Next, a co-solution A and a solution B having composition ratios as indicated in Table 1 were prepared. 
         [0000]    
       
         
               
               
               
             
               
               
               
             
           
               
                 TABLE 1 
               
               
                   
               
               
                   
                 SOLUTION A 
                 SOLUTION B 
               
               
                 COMPONENT 
                 (wt %) 
                 (wt %) 
               
               
                   
               
             
             
               
                   
               
             
          
           
               
                 glucose oxidase 
                 35 
                 38.5 
               
               
                 ruthenium (III) hexaamine 
                 25 
                 20.5 
               
               
                 carbonylmethyl cellulose 
                 0.3 
                 0.3 
               
               
                 microcrystalline cellulose 
                 — 
                 0.2 
               
               
                 Tricaprylmethyl ammonium chloride 
                 — 
                 0.08 
               
               
                 t-Octylphenoxypolyethoxyethanol 
                 1.5 
                 2 
               
               
                 Soap 
                 — 
                 0.5 
               
               
                   
               
             
          
         
       
     
         [0109]    A 100 mM phosphate buffer saline (PBS) at pH 6.5 was prepared. Then, an enzyme (glucose oxidase), an electron transfer medium [ruthenium(III) hexaamine], and carboxymethyl cellulose and 10 mg of t-octylphenoxypolyethoxyethanol as dispersion stabilizers were sequentially added to 1 ml of PBS. 
         [0110]    In the solution B, microcrystalline cellulose, tricaprylmethyl ammonium chloride, and a soap were further added. 
         [0111]    The prepared composition solutions, solution A and solution B, were applied on the electrode of the first substrate in an amount of 1.5 mg, respectively, and then were dried at 50° C. for 20 minutes to be immobilized thereon. Subsequently, the molded adhesive cover was attached thereon and the second substrate was laid thereupon, and the assembly was pressed. 
         [0112]    First, the sensitivity of the biosensor with respect to the constant voltage vs. current method (chronoamperometry) was measured using a glucose standard solution.  FIG. 17  is a dynamic response curve obtained when the solution B was immobilized on the electrode and then the electrochemical measuring method according to a constant voltage vs. current method was applied to the biosensor prepared as described above. Here, the measurement range was 0, 100, 200, 300, and 400 mg/dL of the standard glucose solution. After the sample was filled in the sample inlet, the amount of change in the current over time was measured by maintaining the constant voltage at an applied potential of 300 mV. Here, the slope was 0.06 [μA/(mg/dL)], and the linearity was 0.99, thus excellent linear sensitivity was exhibited at each concentration. 
         [0113]    Next, the sensitivity of the biosensor for a blood sample under optimization of the mediator was measured. Using the biosensor prepared as described above, measurements were taken according to the method of  FIG. 18 , by varying the glucose concentration and the hematocrit (Hct). 
         [0114]    When the blood sample is brought into contact with the sample inlet, the blood sample instantaneously fills the whole channel, and a catalytic reaction involving the following Reaction Scheme 1 takes place. 
         [0000]      Glucose+GO x −FAD→Gluconic acid+GO x −FADH 2    
         [0000]      GO x −FADH 2 +mediator(ox)→GO x −FAD+mediator(red)  [Chemical Formula 1] 
         [0115]    In Chemical Formula I, GO x −FADH 2  and GO x −FAD respectively represent the reduced state and the oxidized state of flavin adenine dinucleotide (FAD), which is the active site of glucose oxidase (GO x ). 
         [0116]    When the sample is in contact with the recognition electrode, the voltage between the electrodes is cut off, and an incubation time of 6 seconds occurs. After 6 seconds, a constant voltage of 300 mV was applied through the operating electrode and the counter electrode. Then, the amount of change in the current flow flowing through the electrodes was measured to calculate the glucose concentration. 
         [0117]      FIG. 19  is a graph showing the measurement results obtained at different glucose concentrations, by applying the solution A onto the biosensor and then varying the hematocrit (Hct) of the blood to 37, 43, and 61%, while  FIG. 20  is a graph showing the measurement results obtained at different glucose concentrations, by applying the solution B onto the biosensor and then varying the hematocrit of the blood to 32, 43, and 57%. 
         [0118]    Here, the average amount introduced to 100 biosensors was 0.6, and a graph showing little impact of the blood type due to the interaction of the mediator was obtained. In  FIG. 19 , the average coefficient of variation (CV) at each concentration had a value of 5% or greater, while in  FIG. 20 , the coefficient of variation had a value of 3% or less. As such, it can be seen that when microcrystalline cellulose, tricaprylmethyl ammonium chloride, and a soap were further added, the accuracy of measurement was improved. 
         [0119]    As described above, the biosensor has effects of significantly reducing the amount of a sample, allowing two or more measurements, and being applicable to the measurement of two or more target materials. Furthermore, accurate measurement is made possible by using a compatibilized mediator. 
         [0120]    While this invention has been described in connection with what is presently considered to be practical exemplary embodiments, it is to be understood that the invention is not limited to the disclosed embodiments, but, on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims.