APPARATUS AND METHOD FOR MEASURING CONCENTRATION OF WHOLE BLOOD SAMPLES

• US 20160077037A1
• Filed: 12/08/2014
• Published: 03/17/2016
• Est. Priority Date: 09/17/2014
• Status: Active Grant

• Current Assignee: i-SENS, Inc.
• Original Assignee: i-SENS, Inc.
• Inventors: Choi, Sung Hyuk, KANG, Youngjea, Lee, Myeongho, PARK, Ho Dong, CHO, Sung Pil, Cha, Geun Sig, Nam, Hakhyun, Lee, Seok-Won
• Granted Patent: US 10,690,619 B2
• Time in Patent Office: Days
• US Class Current: 1/1
• CPC Class Codes: A61B 2562/0295 Strip shaped analyte sensors for apparatus classified in A61B5/145 or A61B5/157 disposable multilayered or laminated electrodes G01N27/307; details of handling chemical test elements G01N33/4875
• CPC Class Codes: A61B 5/14532 for measuring glucose, e.g. by tissue impedance measurement
• CPC Class Codes: A61B 5/1468 using chemical or electrochemical methods, e.g. by polarographic means A61B5/1486 takes precedence
• CPC Class Codes: A61B 5/1495 Calibrating or testing of in-vivo probes
• CPC Class Codes: B01L 2200/16 Reagents, handling or storing thereof
• CPC Class Codes: B01L 2300/0645 Electrodes
• CPC Class Codes: B01L 2300/0825 Test strips
• CPC Class Codes: B01L 3/5023 with a sample being transported to, and subsequently stored in an absorbent for analysis
• CPC Class Codes: C12Q 1/001 Enzyme electrodes
• CPC Class Codes: C12Q 1/002 Electrode membranes
• CPC Class Codes: G01N 27/3271 Amperometric enzyme electrodes for analytes in body fluids, e.g. glucose in blood amperometry per se G01N27/49; aspects concerning the enzyme reagent C12Q1/001
• CPC Class Codes: G01N 27/3272 Test elements therefor, i.e. disposable laminated substrates with electrodes, reagent and channels optical biosensors G01N33/52
• CPC Class Codes: G01N 27/3273 Devices therefor, e.g. test element readers, circuitry details not specific to biochemical electrodes G01N33/4875
• CPC Class Codes: G01N 27/3274 Corrective measures, e.g. error detection, compensation for temperature or hematocrit, calibration coding of calibration information G01N33/48771
• CPC Class Codes: G01N 27/3277 being a redox reaction, e.g. detection by cyclic voltammetry voltammetry per se G01N27/42, G01N27/48
• CPC Class Codes: G01N 27/42 Measuring deposition or liberation of materials from an electrolyte; Coulometry, i.e. measuring coulomb-equivalent of material in an electrolyte
• CPC Class Codes: G01N 27/48 using polarography, i.e. measuring changes in current under a slowly-varying voltage
• CPC Class Codes: G01N 27/49 Systems involving the determination of the current at a single specific value, or small range of values, of applied voltage for producing selective measurement of one or more particular ionic species
• CPC Class Codes: G01N 33/26 Oils; viscous liquids; paints; inks G01N33/22 takes precedence
• CPC Class Codes: G01N 33/48707 by electrical means G01N33/49, G01N33/493 take precedence
• CPC Class Codes: G01N 33/4875 : Details of handling test elements, e.g. dispensing or storage, not specific to a particular test method test-elements per se B01L, automatic analysers G01N35/00, in-vivo analysis on the human body for medical diagnosis A61B
• CPC Class Codes: G01N 33/48771 : Coding of information, e.g. calibration data, lot number
• CPC Class Codes: G01N 33/49 : Blood chemical methods for determining blood cell populations G01N33/5094; chemical analysis of blood groups or blood types G01N33/80
• CPC Class Codes: G01N 33/52 : Use of compounds or compositions for colorimetric, spectrophotometric or fluorometric investigation, e.g. use of reagent paper and including single- and multilayer analytical elements immunological elements G01N33/54386; involving labelled immunochemicals G01N33/58; for haemoglobin or occult blood G01N33/72
• CPC Class Codes: G01N 33/5302 : Apparatus specially adapted for immunological test procedures
• CPC Class Codes: G01N 33/5438 : Electrodes

Abstract

A method for measuring a concentration of an analyte in a bio-sample using an electrochemical bio-sensor according to an exemplary embodiment of the present invention is characterized by a step of obtaining predetermined features from induced currents obtained by applying a DC voltage according to chronoamperometry in which, after a whole blood sample is injected to the electrochemical bio-sensor, a concentration of an analyte is obtained from an induced current obtained by applying a DC voltage for a certain time and from all induced currents obtained by further applying several step-ladder perturbation potentials for a short time subsequent to the DC voltage for the certain time, and is also characterized by minimization of a measurement error caused by a hindering material by forming a calibration equation by combining the at least one feature in a function and optimizing various conditions of the bio-sample through Deleted Texts multivariable analysis.

With this configuration, a perturbation potential application method added to a conventional measurement method can maintain a bio-sensor and a measuring apparatus already used, a line used in the measuring apparatus, and calibration of amperometry as they are, improve accuracy in measurement by effectively minimizing a matrix interference effect of a background material in a bio-sample, particularly an inaccuracy caused by a change in hematocrit, and also remarkably improve accuracy in measurement by simply upgrading a measurement program of a conventional measuring apparatus.

Claims

1. A method for measuring a concentration of an analyte in a bio-sample, the method comprising:

a step of introducing a liquid bio-sample into a sample cell in which an oxidation/reduction enzyme capable of catalyzing an oxidation/reduction reaction of the analyte and an electron transfer mediator are fixed and a working electrode and an counter electrode are provided;

a step of obtaining a first induced current by applying a constant DC voltage to the working electrode to start the oxidation/reduction reaction of the analyte and proceed with an electron transfer reaction;

a step of obtaining a second induced current by applying a -step ladder-type perturbation potential after applying the constant DC voltage;

a step of calculating a predetermined feature from two or more characteristic points from the first induced current or the second induced current; and

a step of calculating a concentration of the analyte using a calibration equation formed of at least one feature function so as to minimize an effect of at least one hindering material in the bio-sample.

2. The method for measuring a concentration of an analyte in a bio-sample of claim 1, wherein

the -step ladder-type perturbation potential is characterized by a height (V_step) of each step, an application time (t_step) for each step, a difference (V_center) between a middle voltage and a constant voltage in the entire range of variations, a difference (V_peak) between a middle voltage and a peak voltage, and a time difference (t_cycle) between a peak voltage of the entire step ladder-type wave and a peak voltage of the adjacent next step ladder-type wave.

3. The method for measuring a concentration of an analyte in a bio-sample of claim 1, wherein

the second induced current is obtained within 0.1 to 1 second after the first induced current is obtained.

4. The method for measuring a concentration of an analyte in a bio-sample of claim 1, wherein

the constant DC voltage and the -step ladder-type perturbation potential are applied to the working electrode through the same digital-to-analog converter circuit linked with a microcontroller.

5. The method for measuring a concentration of an analyte in a bio-sample of claim 1, wherein

a characteristic point having different linearity with respect to the analyte and the hindering material is selected from the first or second induced current, a feature is formed of the characteristic point, and a calibration equation is formed of the feature.

6. The method for measuring a concentration of an analyte in a bio-sample of claim 5, wherein

the feature is formed of the characteristic point by using one of the second induced currents near peak and valley voltages of a specific step ladder type, curvature of a curved line formed of induced currents of each step of the step ladder-type perturbation potential, a difference between a current value of a peak and a current value of a valley of the step ladder-type perturbation potential, induced currents in the middle of ups and downs of the step ladder-type perturbation potential, induced currents at a starting point and an ending point of each step ladder-type perturbation potential cycle, and an average value of induced currents obtained from the step ladder-type perturbation potential, and values which can be obtained by expressing the current values obtained therefrom by the four fundamental arithmetic operations and mathematical functions such as an exponential function, a logarithmic function, and a trigonometric function are used.

7. The method for measuring a concentration of an analyte in a bio-sample of claim 1, wherein

the calibration equation is obtained by applying multivariable regression analysis to the feature function as a linear mixture of the feature, and the calibration equation varies depending on a material of the electrodes, arrangement of the electrodes, a shape of a flow path, and a characteristic of a reagent to be used.

8. The method for measuring a concentration of an analyte in a bio-sample of claim 7, wherein

the analyte is one of glucose, β

-hydroxybutyric acid, cholesterol, triglyceride, lactate, pyruvate, alcohol, bilirubin, uric acid, phenylketonuria, creatine, creatinine, glucose-6-phosphate dehydrogenase, NAD(P)H, and a ketone body.

9. The method for measuring a concentration of an analyte in a bio-sample of claim 7, wherein

the oxidation/reduction reaction enzyme is one of a glucose oxidase (GOx), a glucose dehydrogenase (GDH), a glutamate oxidase, a glutamate dehydrogenase, a cholesterol oxidase, a cholesterol esterase, a lactate oxidase, an ascorbic acid oxidase, an alcohol oxidase, an alcohol dehydrogenase, a bilirubin oxidase, and a ketone body dehydrogenase.

10. The method for measuring a concentration of an analyte in a bio-sample of claim 1, wherein

the electron transfer mediator which can be used together with the above-described enzymes is one of ferrocene, ruthenium hexamine(III) chloride, potassium ferricyanide, 1,10-phenanthroline-5,6-dione, and bipyridine, or an osmium complex including phenanthroline as a ligand, 2,6-dimethyl-1,4-benzoquinone, 2,5-dichloro-1,4-benzoquinone, 3,7-diamino-5-phenothiaziniumthionine, 1-methoxy-5-methylphenazinium methylsulfate, methylene blue, and toluidine blue.

11. The method for measuring a concentration of an analyte in a bio-sample of claim 1, wherein

the constant DC voltage having a voltage range of 0 to 800 mV is consecutively or intermittently applied for 1 second or more to less than 1 minute, and the first induced current is measured one time or several times while the constant DC voltage is applied.

12. The method for measuring a concentration of an analyte in a bio-sample of claim 2, wherein

a height (V_step) of a step of the step ladder-type potential is 0.5 to 20 mV, a duration time (t_step) of the step is 0.001 to 0.1 second, a difference (V_center) between a middle voltage and a constant voltage of the step ladder-type potential is −

150 to 150 mV, a difference (V_peak) between the middle voltage and a peak or valley voltage of the step ladder-type potential is 5 to 150 mV, and a cycle of the step ladder-type potential or a time difference (t_cycle) between a peak and the adjacent next peak is in the range of 0.01 to 1 second.

13. The method for measuring a concentration of an analyte in a bio-sample of claim 1, wherein:

the feature function includes a function using an induced current value obtained from the constant DC current, a function using an induced current value obtained from the step ladder-type potential, a function using a temperature value measured by the measuring apparatus, and a function which can be obtained by expressing measured current values by the four fundamental arithmetic operations and mathematical functions including an exponential function, a logarithmic function, and a trigonometric function.

14. The method for measuring a concentration of an analyte in a bio-sample of claim 1, wherein

the calibration equation is one of

glucose=Σ

_jc_jf_j(i),

glucose=Σ

_jc_jf_j(i,T), and

ketone body=Σ

_jc_jf_j(i),

wherein i denotes one or more current values which can be obtained from the first induced current and the second induced current, and T denotes temperature values that are independently measured.

15. An apparatus for measuring a concentration of an analyte in a bio-sample, the apparatus comprising:

a connector to which a sample cell in which an oxidation/reduction enzyme capable of catalyzing an oxidation/reduction reaction of the analyte and an electron transfer mediator are fixed and a working electrode and an counter electrode are provided is inserted;

a digital-to-analog converter circuit configured to apply a constant DC voltage to start the oxidation/reduction reaction of the analyte, proceed with an electron transfer reaction, and apply a -step ladder-type perturbation potential for fluctuating a potential of the sample cell after applying the constant DC voltage; and

a microcontroller configured to control the digital-to-analog converter circuit and directly obtain a concentration value of the analyte from a calibration equation using the -step ladder-type perturbation potential.

16. The apparatus for measuring a concentration of an analyte in a bio-sample of claim 15, wherein

the microcontroller stores a predetermined constant value which can generate the -step ladder-type perturbation potential, records a predetermined constant at a register of the digital-to-analog converter circuit when a constant voltage is applied, and increases/decreases the constant at a predetermined time interval and records the constant at the register of the digital-to-analog converter circuit when the perturbation potential is applied, and the digital-to-analog converter circuit applies the constant voltage or the perturbation potential between the two electrodes depending on the constant value recorded at the digital-to-analog circuit register.