KR20060029672A - Electrochemical biosensor test strip - Google Patents

Abstract

A test strip for an electrochemical biosensor that can effectively compensate for volumetric interference of red blood cells is disclosed. The present invention provides a method of compensating a signal reduction amount by using an electrical signal obtained from a material inside the red blood cells, rather than blocking the red blood cells, which has been the main method up to now. The present invention provides a test strip for an electrochemical biosensor for measuring the concentration of an analyte other than hemoglobin in a physiological sample containing blood cells, comprising: a first insulator substrate, a plurality of electrodes formed on the first insulator substrate, 1 a reagent that is fixed across the plurality of electrodes on an insulator substrate, reacts with the analyte in the physiological sample to generate a charge corresponding to the concentration of the analyte, and releases hemoglobin from the blood cells, and the concentration of the outflowed hemoglobin And a blood cell interference corrector for generating a charge corresponding thereto.

Electrochemical biosensor, test strip, erythrocyte volume fraction, hemolytic agent

Description

Test strip for electrochemical biosensor {ELECTROCHEMICAL BIOSENSOR TEST STRIP}

1 is an exploded perspective view showing a conventional thin film type electrochemical enzyme electrode.

Figure 2 is an exploded perspective view of a test strip for an electrochemical biosensor to which the present invention is applied.

3 is a conceptual diagram of a glucose sensor using an enzyme-electron transporter reaction according to the present invention.

4 is a conceptual diagram of a hemoglobin sensor using a hemoglobin-electron transporter reaction according to the present invention.

5 is a diagram illustrating red blood cell volume ratio compensation according to the present invention.

6 is a graph showing the change of the measured value with respect to the red blood cell volume ratio.

Figure 7 is a graph showing the interference effect of the red blood cell volume ratio in the conventional case that does not contain a red blood cell hemolytic agent.

8 is a graph showing the interference effect on the red blood cell volume ratio when the red blood cell hemolytic agent is included in the reagent according to the present invention.

The present invention relates to a test strip for an electrochemical biosensor, and more particularly to a test strip for an electrochemical biosensor for measuring the concentration of an analyte in a physiological sample containing blood cells.

Blood is composed of about 55% of body fluid plasma and about 45% of tangible blood cells. Plasma is 92% water, 6.5-7% plasma protein, and the remaining 1-1.5% are inorganic salts, enzymes, hormones, vitamins, lipids and sugars. The tangible component of blood cells consists of erythrocyte (RBC), leukocyte (WBC) and platelets, most of which are occupied by red blood cells.

The most problematic problem in the electrochemical biosensor using the blood thus constructed is the interference of tangible components, ie, red blood cells. The percentage of red blood cells in the blood can be expressed as a% value, which is called hematocrit (Hct). The normal range of erythropoiesis varies according to adults, pregnant women, and newborns. Although there are differences among individuals, the normal range is 35-50% for normal adults, but lower for pregnant women and higher for newborns. Such a wide range of erythrocyte volume fractions can lead to errors in measurements in electrochemical biosensor systems. For example, blood glucose measurement has important clinical significance for adults, pregnant women, and newborns. In general, blood with high red blood cell volume shows lower values than actual values for blood glucose measurement, while blood with low red blood cell volume shows higher values.

As a cause of distorting the measured values, 1) unstable diffusion between the plasma and the reagent layer due to the increase of red blood cells in the blood and reduction of plasma, 2) reduction of the electrode area due to red blood cell and protein adsorption on the electrode surface, 3) viscosity Change, 4) microcoagulation, 5) hemolysis, etc., but in electrochemical systems, the main cause is irregularly adsorbed blood cells and protein components on the electrode surface. These measurement distortion factors make it difficult to calculate accurate measurements for the analyte.

Therefore, the following techniques are reviewed in order to reduce the effect of adsorption of red blood cells and proteins, and to obtain accurate measurement values. 1 is a view showing a thin-film electrochemical enzyme electrode, YSI 2300 STAT PLUS (Yellow Spring Instrument, Inc.) already commercialized as a product. This measuring apparatus is composed of three thin films, namely, an enzyme thin film 101, an outer thin film 103, an inner thin film 105, and a platinum electrode 107, as shown in FIG. This system is characterized by the production of enzymes that react with analytes in thin films, functional polymer thin films such as cellulose acetate and polycarbonate inside and outside the thin films, respectively. The adsorption to the electrode surface is effectively blocked. However, such an enzyme electrode system is an expensive device, and is used in a hospital or a specific research center as a reference device rather than a disposable purpose, and is not suitable for field inspection. In addition, a large amount of blood consumption and relatively late response time are pointed out as disadvantages.

U.S. Patent Nos. 5,708,247 and 5,951,836 (name of the invention: Disposable Glucose Test Strips, And Methods And Compositions For Making Same) and U.S. Patent No. 6,241,862 (name of the invention: Disposable Test Strips With Integrated Reagent / Blood Separation Layer) Describes a method for manufacturing a carbon paste electrode system using screen printing techniques and a reagent / blood separation layer immobilized on an electrode system surface. As described above, in order to reduce the interference effect on the red blood cell volume ratio, a silica filler, which is a non-conductive material, is combined with hydroxyethyl cellulose to introduce a carbon electrode system. Silica, which is a non-conductive substance, has been described as being able to suppress adsorption of red blood cells, proteins, and the like by forming a two-dimensional network structure after being dried together with a reagent by a balance between hydrophilicity and hydrophobicity. However, the carbon paste electrode by the screen printing method is relatively unstable compared to the metal electrode due to the uneven electrode surface and the decomposition and leakage of the electrode material over time. In addition, when the hydrophilicity and hydrophobicity ratio of silica, which is a non-conductive substance, is skewed to one side, the network structure becomes unstable, and the measured value may be distorted due to the diffusion rate between the sample and the electrode.

As described above, in order to reduce the interference effect on the red blood cell volume ratio, conventionally, a separate thin film is introduced into and out of the thin film type enzyme electrode or a non-conductive material such as silica is formed on the carbon paste electrode to form a two-dimensional network structure. It was. However, although the thin film type enzyme electrode called membrane technology can innovatively remove the hematocrit interference effect, it is difficult to introduce three thin films, namely, the enzyme thin film 101, the outer thin film 103, and the inner thin film 105, into the electrode system. Due to the high cost and process, it is a problem for mass production and price competitiveness as a disposable self-diagnostic sensor. In addition, the blood consumption is high, and the reaction time is long because the sample is transmitted through the three thin film and react with the electrode. Therefore, the membrane technology is excellent in the effect of erythrocyte volume fraction interference, but there are a lot of problems to steal it as a component of the actual disposable self-diagnosis sensor.

As another method, silica and various kinds of polymer components, as well as silica, may be introduced on the surface of the electrode to prevent erythrocyte volume fraction interference effect, that is, adsorption of red blood cells or proteins in a sample. However, since the polymers generally used are hydrophilic, when the sample comes in, it dissolves with the sample, and thus the net structure cannot play an effective blocking role. In the case of the non-hydrophilic polymer, it has a physically stable structure due to the interfacial repulsion with the hydrophilic reagent layer. There is a serious problem that it is difficult to build.

The present invention has been proposed to solve the conventional problems as described above, and an object of the present invention is to provide a disposable self-diagnostic sensor capable of effectively compensating volumetric interference of red blood cells.

It is another object of the present invention to provide an electrochemical biosensor that can effectively compensate for volumetric interference of erythrocytes and can be manufactured at low cost.

Another object of the present invention is to provide an electrochemical biosensor capable of efficiently compensating volumetric interference of erythrocytes and capable of mass production in a simple process.

The present invention for achieving the above object is not a method of blocking the red blood cells, which has been the main method to date, but the conventional technology in that it provides a method for compensating the signal reduction by using the electrical signal obtained from the material inside the red blood cells. It is different from.

The present invention provides a test strip for an electrochemical biosensor for measuring the concentration of an analyte other than hemoglobin in a physiological sample containing blood cells, comprising: a first insulator substrate, a plurality of electrodes formed on the first insulator substrate, 1 a reagent that is fixed across the plurality of electrodes on an insulator substrate, reacts with the analyte in the physiological sample to generate a charge corresponding to the concentration of the analyte, and releases hemoglobin from the blood cells, and the concentration of the outflowed hemoglobin It characterized in that it comprises a blood cell interference correction agent for generating a charge corresponding to the. And a second insulator substrate disposed on the first insulator substrate and forming a path for introducing the physiological sample into the reagent.

The advantage of the present invention is that no membrane technology is used, and it effectively blocks the electrode surface adsorption of erythrocytes present in a sample without introducing hydrophilic and non-hydrophilic polymers to form a specific network structure, and at the same time, the effect of erythrocyte volume fraction interference. You can make it insensitive. In addition, the present invention has the advantage of providing a disposable electrochemical biosensor test strip that can be mass-produced at a low cost and simple process.

Hereinafter, with reference to the accompanying drawings will be described an embodiment of the present invention; This embodiment is particularly applicable to glucose detection, but this is merely for convenience of explanation and can naturally be used to detect the concentration of any analyte contained in a physiological sample.

2 is an exploded perspective view of a test strip for an electrochemical biosensor to which the present invention is applied. As shown in FIG. 2, the test strip 200 for an electrochemical biosensor includes an insulator substrate 201, electrodes 203 and 205 formed on the insulator substrate 201, and an electrode 203 in the insulator substrate 201. And 205, which is fixed over the 205 and reacts with the analyte in the physiological sample to generate a charge corresponding to the concentration of the analyte. Reagent 207 also includes a blood cell interference corrector that reacts with the blood cells in the physiological sample to generate a charge corresponding to the concentration of the blood cells.

In FIG. 2, an insulator substrate 201 having a reference electrode 203 and a working electrode 205 formed thereon is attached to another insulator substrate 211 with a spacer 209 interposed therebetween. The cutout 210 formed in the spacer 209 forms a path for sample introduction. 2 illustrates a two-electrode system, but the present invention may naturally be applied to a three-electrode system.

Reagent 207 is fixed across the reference electrode 203 and the working electrode 205 as shown in Figure 2, the cut portion 210 by a method such as automated dispenser, screen printing, roll coating, spin coating, etc. It may be coated on the electrode region on the insulator substrate 201 corresponding to the. The reagent 207 reacts with the sample to generate a charge when a physiological sample (or sample) is provided, and corresponds to the analyte concentration in the sample at the electrodes 203 and 205 when a suitable voltage is applied to the two electrodes 203 and 205. Allow current to flow.

The reagent 207 may be a biochemical having an intermolecular recognition ability to react with an analyte (e.g., an enzyme, an antibody, a protein, etc.), an electron carrier which can effectively transfer charges generated by a biochemical reaction to the electrode surface, and an electrode surface. It may comprise a hydrophilic polymer compound used as a support between biochemicals, a surfactant used as a dispersant. The enzyme used varies depending on the substance to be detected. For example, glucose oxidase can be used when glucose is to be detected. Hydrophilic polymer compounds are required to easily fix the reagent on the electrode, for example, cellulose, hydroxyethyl cellulose and the like. Surfactant is to facilitate the introduction of the sample to be analyzed in the sample introduction path formed by the cut portion 210, for example, Triton X-100. See US Pat. No. 5,762,770 for specific preparation methods of reagents, examples of reagents that can be used, and electron transporters. US Patent No. 5,762,770 is hereby incorporated by reference herein.

As described above, the reagent 207 further includes a blood cell interference corrector (not shown). The blood cell interference corrector may include a hemolytic agent that destroys erythrocytes in a physiological sample and releases hemoglobin in the erythrocytes to the outside, and an electron transporter that delivers charges generated in response to the leaked hemoglobin to the electrode 205. have. If the electron reagent is already included in the existing reagent, the blood cell interference compensator may not include the electron carrier. Hemolytic agents include at least one of saponin, sodium, deoxycholate, ethylene diamine tetra acetate (EDTA), lysis buffer, and detergent In combination.

3 is a conceptual diagram of a glucose sensor using an enzyme-electron transporter reaction according to the present invention. As shown in FIG. 3, glucose (Glucose) first reacts with Glucose Oxidase (GOD) 301 to become Gluconic Acid. The reduced glucose oxidase (GOD _red ) delivers electrons (e-) to the electron carrier, returns to the original glucose oxidase (GOD _ox ), and the electron carrier 303 transfers the electrons (e-) to a predetermined voltage. It transfers to this hanging electrode 305 again. Through this mechanism, the enzyme-electron transporter shown in FIG. 3 allows current to flow through the electrode corresponding to the concentration of glucose contained in the physiological sample in the absence of blood cells such as red blood cells in the physiological sample. However, when blood cells such as red blood cells are included in the physiological sample, the current flowing through the electrode is inversely proportional to the amount of red blood cells due to the interference effect of red blood cells as described above. This relationship is shown in Fig. 5A. In FIG. 5, the horizontal axis indicates the red blood cell volume ratio (hematocrit), and the vertical axis indicates the amount of current flowing through the electrode of the test strip.

4 is a conceptual diagram of a hemoglobin sensor using a hemoglobin-electron transporter reaction according to the present invention. First, when red blood cells (RBCs) are hemolyzed by a lysing agent, hemoglobin in red blood cells is leaked to the outside. The hemoglobin reacts with the electron transporter 401 to transmit electrons (e-), and the electrons (e-) thus transferred are delivered to the electrode 305 again. Through this mechanism, the hemoglobin-electron transporter causes a current to flow in the electrode proportional to the amount of red blood cells in the physiological sample. This relationship is shown in Fig. 5B.

The reagent for an electrochemical biosensor according to the present invention includes a conventional hemolytic agent as well as an electron transporter. Therefore, the current flowing through the electrode, that is, the output current is the current flowing through the electrode by the glucose sensor using the enzyme-electron transporter reaction (A in FIG. 5) and the current flowing by the hemoglobin sensor using the hemoglobin-electron transporter reaction (see FIG. 5). B) combined. As a result, the current flowing through the electrode of the test strip is constant regardless of the erythrocyte volume fraction (hematocrit), as shown in FIG. That is, the current (A) of the enzyme-electron transporter reduced by the increase in the volume ratio of the red blood cells is compensated by the current (B) of the hemoglobin-electron transporter.

The reagents used in this example were prepared as follows. First, 0.75 g of polyvinyl alcohol and 1 g of Triton X-100 are dissolved in 100 ml of Potassium phosphate buffer (100 mM, pH 7.4). After mixing the solution for 1 hour at room temperature, 6.59 g of potassium ferricianide and 3 g of glucose oxidase, a redox enzyme, are added and mixed for 1 hour. To this mixed enzyme solution, erythrocyte hemolytic agents as shown in Table 1 were added and mixed at 8 ° C. for 40 hours.

Using this enzyme solution to prepare a glucose sensor (glucose sensor). In FIG. 2, a sputtering process is applied to the substrate 201 to form gold (Au, 99.9%) electrodes 203 and 205 of 100 nm or less, and then the PET film 209 is bonded by using a laminator. The enzyme solution is coated on the electrodes 203 and 205 thus manufactured, and then dried for 1 hour. Finally, after adhering the PET film 211, it is cut into a size of 30mm in length, 7.5mm in width to form a glucose strip.

The blood glucose value is measured according to the change in hematocrit using the sensor manufactured as described above. First, whole blood is separated into plasma and blood cells using a centrifuge. Separated plasma and blood cells are recombined in an appropriate ratio to produce blood having various red blood cell volume ratios. The hematocrit at this time is produced in 20%, 30%, 40%, 50%, 60%. In all cases, blood glucose levels should be constant at 180 mg / dl as measured by the YSI instrument. The result is shown in FIG. 6A is a graph showing the relationship between hematocrit and blood glucose values. In FIG. 6A, the horizontal axis represents hematocrit in% and the vertical axis represents output current in uA. In FIG. 6A, "control" denotes a case of a conventional reagent that does not include a hemolytic agent, and "agenti" denotes a case where a hemolytic agent is included in an existing reagent according to the present invention. "agent1", "agent2", and "agent3" indicate the case where different types and concentrations of hemolytic agents are used. Each blood glucose value was converted to a percentage of blood glucose values based on hematocrit (44%) of blood. The result is as shown in Figure 6b.

As shown in FIGS. 6A and 6B, the reliance on hematocrit decreases when the erythrocyte hemolytic agent is contained (agenti), compared to the case where the hemolytic agent is not included (control). This reduced electrical dependence of hemoglobin from hemolytic red blood cells on hematocrit, which had been observed in conventional sensors. In addition, red blood cells are hemolysed to reduce the adsorption to the electrode surface, and the increase in viscosity of the solution due to hematocrit is also partially reduced.

Fifty diabetic patients with a wide range of blood glucose and hematocrit were tested using venous blood. The measured blood glucose value was compared with the YSI blood glucose analyzer to determine the correlation with the YSI, and the error range with the YSI measurement value is shown according to the measured hematocrit range. The results are shown in FIG. 7 and FIG. 8. Figure 7 is a case of using a conventional reagent, Figure 8 is a case of using the reagent of the present invention including a hemolytic agent. The correlation in FIG. 8 is significantly increased compared to FIG. 7, and the error rate is greatly reduced in the range of hematocrit 30-50%.

The above embodiments are merely examples to enable those skilled in the art to easily understand and implement the present invention, and are not intended to limit the scope of the present invention. Therefore, those skilled in the art should note that various modifications or changes are possible within the scope of the present invention. The scope of the invention is defined in principle by the claims that follow.

In the electrochemical biosensor test strip of the present invention as described above, an enzyme, an electron transfer medium, a hydrophilic polymer, a surfactant, an erythrocyte hemolytic agent, etc. are mixed to form a reagent layer, and thus an accurate measurement value insensitive to the erythrocyte volume fraction interference effect. Can be provided. Therefore, the biosensor test strip according to the present invention can be easily applied to patients such as adults, newborns, and pregnant women having different erythrocyte volume ratio values. In addition, the present invention has the advantage that can be produced at a low price while effectively compensating for the volume ratio interference of red blood cells. In addition, the present invention can effectively compensate for the volumetric interference of red blood cells, there is an advantage that can provide an electrochemical biosensor capable of mass production in a simple process.

Claims (2)

In a test strip for an electrochemical biosensor for measuring the concentration of an analyte other than hemoglobin in a physiological sample containing blood cells, A first insulator substrate, A plurality of electrodes formed on the first insulator substrate, A reagent fixed in the first insulator substrate across the plurality of electrodes and reacting with the analyte in the physiological sample to generate a charge corresponding to the concentration of the analyte; A test strip for an electrochemical biosensor, comprising: a hemoglobin flowing out of the blood cells, a blood cell interference correcting agent generating a charge corresponding to the concentration of the hemoglobin released. The method of claim 1, And a second insulator substrate disposed on the first insulator substrate and forming a path for introducing the physiological sample into the reagent.

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