WO2010043985A1 - Non-enzymatic electrochemical method for simultaneous determination of total hemoglobin and glycated hemoglobin - Google Patents
Non-enzymatic electrochemical method for simultaneous determination of total hemoglobin and glycated hemoglobin Download PDFInfo
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- WO2010043985A1 WO2010043985A1 PCT/IB2009/050399 IB2009050399W WO2010043985A1 WO 2010043985 A1 WO2010043985 A1 WO 2010043985A1 IB 2009050399 W IB2009050399 W IB 2009050399W WO 2010043985 A1 WO2010043985 A1 WO 2010043985A1
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N27/00—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means
- G01N27/26—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating electrochemical variables; by using electrolysis or electrophoresis
- G01N27/28—Electrolytic cell components
- G01N27/30—Electrodes, e.g. test electrodes; Half-cells
- G01N27/327—Biochemical electrodes, e.g. electrical or mechanical details for in vitro measurements
- G01N27/3271—Amperometric enzyme electrodes for analytes in body fluids, e.g. glucose in blood
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N33/00—Investigating or analysing materials by specific methods not covered by groups G01N1/00 - G01N31/00
- G01N33/48—Biological material, e.g. blood, urine; Haemocytometers
- G01N33/50—Chemical analysis of biological material, e.g. blood, urine; Testing involving biospecific ligand binding methods; Immunological testing
- G01N33/72—Chemical analysis of biological material, e.g. blood, urine; Testing involving biospecific ligand binding methods; Immunological testing involving blood pigments, e.g. haemoglobin, bilirubin or other porphyrins; involving occult blood
- G01N33/721—Haemoglobin
- G01N33/723—Glycosylated haemoglobin
Definitions
- the present invention relates to a method which uses a non-enzymatic, disposable screen-printed electrode strip (SPE strip) for simultaneous measurement of total hemoglobin (Hb) and percentage of glycated hemoglobin (%HbAlc) in a blood sample wherein the total Hb is estimated by amperometry or differential pulse voltammetry, and the amount of HbAIc is estimated by potentiometry. Modification of a SPE strip for potentiometric measurement of HbAIc is also disclosed.
- SPE strip non-enzymatic, disposable screen-printed electrode strip
- HbAIc is a stable minor variant of Hb, formed in vivo by non-enzymatic post-translational modification of N-terminal valine of the ⁇ -chains of Hb.
- Estimation of HbAIc is extremely valuable for long-term control of diabetes mellitus unlike direct estimation of glucose wherein one obtains information of blood sugar at the time of measurement.
- U.S. Patent No. 7,005,273 describes enzyme catalyzed electrochemical methods to measure Hb and HbAIc, and a spectrophotometric method to measure HbAIc.
- the method is based on an indirect electrochemical estimation of Hb using a measurement of dissolved oxygen and enzyme-catalyzed reactions. Disadvantages of this method relate to the stability of the enzyme and the shelf life of the system. It is well known that the dissolved oxygen levels are temperature dependent and hence a constant temperature environment needs to be maintained for the reliability of the analysis. Further, oxygen solubility in an aqueous environment is not sufficient to provide the required current signals for the indirect determination of Hb.
- U.S. Patent No. 6,677,158 describes a colorimetric method for HbAIc estimation that can be performed outside of the medical laboratory and includes several steps involving chemical addition and colour read-out devices for Hb measurement which require high dilution of the sample. This technique is rather complex and requires several manual operations. Moreover, in colorimetric measurements, sensitivity is relatively less compared to other methods.
- U.S. Patent No. 4,876,205 describes a method for assaying Hb in blood in which the blood is contacted with a sufficient amount of a ferricyanide (redox mediator) so that hemoglobin in the blood is reacted therewith and the hemoglobin is electrochemically assayed by monitoring the change in current, produced on reduction of ferricyanide by hemoglobin.
- a ferricyanide redox mediator
- the assay method incorporates a dry strip sensor with a dry mixture containing finely divided ferricyanide and a non-ionic surfactant, clerol (a mix of polyethylene oxide and polypropylene oxide and emulsifiers).
- clerol a mix of polyethylene oxide and polypropylene oxide and emulsifiers.
- the strip contains non-ionic or neutral surfactants such as Triton X-100 for Hb and a cationic surfactant for uric acid.
- the strip is used subsequently as an amperometric sensor. Neither anionic nor cationic surfactants are used in this method for sensing Hb.
- HbAIc There are known methods for analysis of HbAIc.
- the DCA2000 analyzer from Siemens Diagnostics is an automated enzyme immunoassay method for determination of HbAIc.
- Most of the commercially available analyzers employ HPLC as a tool for the assay of HbAIc [Clinical Biochemistry, 2005, 38, 88-91].
- an aspect of the present invention is to provide a rapid, non-enzymatic and direct method for simultaneous determination of HbAIc by potentiometry and total Hb by amperometry or differential pulse voltammetry in blood in a single analysis.
- the present invention relates to a screen-printed electrode (SPE) strip for simultaneous measurement of total Hb and %HbAlc in a blood sample.
- the strip includes four electrodes.
- the SPE strip is non-enzymatic.
- the SPE strip is disposable.
- the invention also relates to a non-enzymatic, disposable screen-printed electrode (SPE) strip for simultaneous measurement of total Hb by amperometry or differential pulse voltammetry, and %HbAlc by potentiometry in a blood sample. Still another aspect of the invention is that the strip is used in a method for simultaneous measurement of total Hb and % HbAIc in a blood sample.
- the present invention also relates to a kit for simultaneous measurement of total Hb and %HbAlc in blood sample comprising a SPE strip (as described above), a lysis solution, and a surfactant solution.
- the kit may also include a lancet, a blotting paper strip, an empty vial and an instruction insert.
- Figure 1 is a block diagram of the SPE strip and its connection to a meter.
- FIG. 2 is a block diagram of the hardware and the functional details of the meter.
- Figure 3 is a diagram of a screen-printed electrode (SPE) strip.
- SPE screen-printed electrode
- Figure 4A shows a typical calibration plot for Hb by amperometry.
- Figure 4B shows the electrode response for Hb by amperometry.
- Figure 5A shows a typical calibration plot for Hb by differential pulse voltammetry (DPV).
- Figure 5B shows the electrode response for Hb by differential pulse voltammetry
- Figure 6 shows the DPV response of Hb in 1.5 mM of Sodium dodecylsulphate (SDS) in acetate buffer of pH 5.0 [Hb cone. 0.7-1.7 g/dl].
- Figure 7 shows the potentiometric estimation of HbAIc (the graph line having square symbols ⁇ ) using aminophenylboronic acid polymer film on the electrode surface and estimation of Hb (the graph line with triangle symbols A).
- Figure 8 shows the potentiometric estimation of HbAIc using aminophenylboronic acid in solution.
- Figure 9 shows the potentiometric estimation of HbAIc by using an electrode that has been modified with carbon ink using water-insoluble 4-phenyl- vinyl boronic acid (the graph line having square symbols ⁇ ) and an electrode that has been modified with carbon ink using 3-thiophene boronic acid (the graph line with triangle symbols A).
- screen printed electrode (SPE) strip refers to an electrode strip described below. It is to be understood that although the electrodes can be formed by using screen-printing, the invention is not limited to the use of screen-printing to form the electrodes. Other printing methods or other methods to form the electrodes can be used.
- Nestian response range refers to a range of concentration in which the slope (defined by mV/decade of concentration) is less than the "ideal" Nernstian slope of 59 mV/decade.
- modified electrode refers to an electrode whose surface is coated with layers of the desired functional materials specific to the application.
- a screen-printed carbon or graphite electrode is modified by a water insoluble boronic acid compound.
- differential pulse voltammetry refers to an electro-analytical technique in which a square wave pulse superimposed on a potential dc ramp (linear increase of potential with time) is applied on the sensing electrode and the differential current output is plotted against the applied dc potential.
- reaction area refers to the area on the electrode, which is exposed to the blood sample.
- Glassy carbon also called vitreous carbon refers to a non-graphitizing carbon, which combines glassy and ceramic properties with those of non-graphitizing carbon. The most important properties are high temperature resistance, extreme resistance to chemical attack and impermeability to gases and liquids. Glassy carbon is widely used as an electrode material in electrochemistry.
- meter refers to an instrument, which measures potential difference and current signal generated at the electrode surface when the electrode comes in contact with the blood sample.
- concentration of HbAIc is converted into potential difference
- concentration of Hb is converted into current signal
- both Hb and %HbAlc values are displayed on the screen of the meter.
- Hb consists of four protein chains with four heme portions (Fe 2+ /Fe 3+ ) and is located in the erythrocytes. While not being bound by any theory, the approach of this invention involves analyzing Hb by exploiting the redox behaviour of the heme portions (Fe 2 VFe 3+ ) in Hb molecule using a disposable, screen printed electrode surface coated with a material such as carbon, graphite, gold, platinum, palladium, or a printing ink as described below.
- the method according to this invention includes determining the total amount of Hb in a sample by electrochemically measuring the voltammetric current due to iron (II) and iron (III) redox centers in Hb using surfactant-enhanced current signal amplification methodologies.
- the electrode potential is fixed at a level where the heme molecule interacts with the electrode surface to undergo electron transfer reaction.
- the current observed is directly proportional to the amount of heme present, which in turn is related to the concentration of total Hb present in the given test solution.
- the Hb is treated as described below with a current- enhancing surfactant.
- the released heme group shows significant redox characteristics at the electrode without a redox mediator.
- the heme group can also be released from the Hb molecule using sonic ation followed by centrifugation or by providing the Hb molecule a chemical link to redox mediators (such as ferrocene, methylviologen, etc.).
- the current signal can thus be amplified by using the ionic surfactant and is converted to g/dL of Hb and displayed on the screen of the meter.
- Measurement of HbAIc HbAIc is the glycated form of Hb resulting from the condensation reaction between hexose sugars and Hb.
- HbAIc has been analyzed using a potentiometric approach unlike optical, redox-mediated amperometry, immunoassay and other methods such as quartz crystal mass balance methods.
- the water-insoluble boronic acid compound added as described below results in a complex being formed between boronate and the cis-diol groups of sugars present in the HbAIc.
- an equilibrium potential of the electrode surface is developed that depends on the HbAIc concentration in the sample. The potential difference arises due to change in pKa value of the boronic acid compound at the electrode surface.
- the SPE strip (which is connected directly or indirectly to a meter) is wet by the solution containing red blood corpuscles (RBCs), the presence of Hb and HbAIc is detected by amperometry or differential pulse voltammetry, and potentiometry respectively.
- the current signal can be amplified by using an ionic surfactant, which is converted to g/dL of Hb and displayed on the screen of the meter.
- the SPE strip includes contact pads that are the upper portion of the electrodes and are illustrated by 12 in Figure 3; insulating material, which is the substrate, and insulating non-porous film, which is the electrical insulating film.
- the strip which may be disposable, is used for non-enzymatic detection of Hb and %HbAlc. It comprises: (i) A substrate, which is an electrical insulator. Types of electrical insulators that can be used include but are not limited to glass epoxy board; electrically nonconducting polymer material such as polystyrene; or fiber-reinforced epoxy (FRE) substrates of thickness varying from 0.3 mm to 1.0 mm. In an aspect of the invention, the substrate is FRE. (ii) A conducting film, which is coated on one side of the substrate to form four independent electrodes, namely, (a) counter electrode, (b) working electrode, (c) reference electrode and (d) modified electrode.
- a substrate which is an electrical insulator. Types of electrical insulators that can be used include but are not limited to glass epoxy board; electrically nonconducting polymer material such as polystyrene; or fiber-reinforced epoxy (FRE) substrates of thickness varying from 0.3 mm to 1.0
- the electrical insulating film has properties of electrical insulation with very high impedance of greater than 10 12 ohms. This material is used to coat the conducting film to provide the electrical insulation.
- the electrical insulating film can be a commercially available material.
- An example of an electrical insulating film is XV1300U.V. -NOTATION WHITE", INK NO. CFSN6022, supplied by
- the SPE strip comprises four electrodes wherein electrode 1 (counter electrode), electrode 2 (working electrode) and electrode 3 (reference electrode) are used for estimation of Hb by amperometry or differential pulse voltammetry; and electrode 3 and electrode 4 (modified electrode) are used for estimation of HbAIc by potentiometry.
- Electrode 3 is a common reference electrode for both amperometry and potentiometry. The electrodes are independent of each other and do not touch each other. Electrodes 1, 2, 3 and 4 are shown in Figure 3. According to an aspect of the invention, the locations for the electrodes are marked and one side of the substrate is coated with a conducting film using screen-printing or a similar printing method to form the electrodes. Other methods can also be used to form the electrodes.
- the conducting film is selected from gold, platinum, palladium, silver, carbon or graphite or a printing ink which has the property of adhering to the surface of the substrate without any smearing so that the electrodes remain independent of each other.
- the conducting film accepts or donates electrons and can be used as the mediator to transfer electrons between the analyte and the electrode in the redox reaction.
- printing ink is used as the conducting film and the printing ink typically used is a carbon or graphite ink or a mixture of a carbon and silver ink.
- the material for coating the electrodes is a carbon conducting film or carbon printable ink. Any commercially available conductive carbon ink which gives an electrochemical response for standard cyclic voltammetry experiments can be used.
- a material that can be used for coating the substrate using screen-printing is a conductive carbon paste procured from Coates,
- This conductive carbon paste can be used as an ink to print on predetermined areas of the substrate to form the electrodes.
- the thickness of the conducting film on the substrate is between 20 to 60 microns. In another aspect of the invention, the thickness of the conducting film is about 30 microns.
- each electrode of the SPE strip which is exposed to the solution containing the red blood corpuscles (RBCs) (region 15 in Figure 3), may be:
- Electrode 1 (counter electrode):
- Electrode 2 (working electrode):
- Electrode 3 Length - 3.0 mm to 10.0 mm, preferably 5.0 mm
- Electrode 4 (modified electrode):
- Length - 3.0 mm to 10.0 mm preferably 5.0 mm Width - 0.3mm to 2.0 mm, preferably 0.5 mm Thickness - 20 microns to 150 microns, preferably 60 microns.
- the substrate After the substrate is coated with the conducting film, it is dried at a temperature from 90 0 C to 150 0 C, preferably at about 120 0 C, for about 30 minutes to 60 minutes, preferably for about 45 minutes.
- the substrate After drying, the substrate is dipped in an acid.
- acids that can be used are 10% chromic acid, 10% sulfuric acid, 5-10% nitric acid or 10% hydrochloric acid solution for 10.0 minutes.
- the coated substrate is dipped in 10% chromic acid solution.
- the substrate is removed from the chromic acid solution and washed with water three times for 2 to 15 minutes per wash, preferably, about 10 minutes per wash.
- the substrate is again dried, preferably at about 70 0 C for about 20 minutes.
- An electrical insulating film is applied to the strip by screen printing or another method except on the contact pads and the section of the strip identified as region 15 in Figure 3.
- the conducting film of the fourth electrode (modified electrode), is modified by a water-insoluble boronic acid compound using screen printing or the like at the portion of the electrode that will be immersed in the sample of RBCs shown as 16 in Figure 3.
- This modified coating enables changes such as potential, resistance by electrochemical reaction between the modified electrode and reference electrode to be used to determine the % HbAIc.
- Electrode modification is not possible with the soluble form of boronic acid compounds because the electrode will lose its sensing ability due to the leaching of HbAlc-selective boronic acid and the associated functional groups.
- water-insoluble boronic acid compounds have been used to modify the fourth electrode (electrode 4).
- the water- insoluble boronic acid compound may be selected from 4-phenyl-vinyl boronic acid, aminophenyl boronic acid and thiophene boronic acid. In one aspect of the invention 4-phenyl vinyl boronic acid is used.
- the fourth electrode can be modified according to the following procedures: (a) A water-insoluble boronic acid compound is dissolved in a suitable low volatile solvent that can dissolve the water insoluble boronic acid compound.
- the solvent may be selected from isopropyl alcohol, ethanol, propanol and acetone.
- the solution obtained can be blended with the conductive carbon paste in a weight ratio of 1:0.5 to 1:4, preferably in a ratio of about 1:1 and used for printing on the substrate for potentiometric estimation of HbAIc.
- the printed carbon electrode is modified with a film (thickness: approx.5-10 ⁇ m) of a water-insoluble boronic acid compound, by electro-deposition on the carbon electrode using electro-polymerization procedure/conditions.
- the water-insoluble boronic acid compound and sodium fluoride are dissolved in hydrochloric acid solution.
- Polymerization is effected by dipping the screen-printed fourth carbon electrode in this solution without stirring.
- the fourth electrode potential is scanned between 0.0 and 1.1 V until the charge in the cathodic scan reaches 10 mC cm " . A deep bluish-green film is obtained and it is washed with water.
- the electrode is thus modified and then rinsed with water, followed by rinsing in phosphate buffered saline (PBS) solution.
- PBS phosphate buffered saline
- Other processes can be used to prepare the modified electrode. Only the portion of the fourth electrode that will be immersed in the sample of RBCs is modified.
- Figure 3 describes a screen-printed electrode (SPE) strip. It consists of four electrodes, namely, counter electrode 1, working electrode 2, reference electrode 3 and modified electrode 4. Basically, the electrodes are screen printed on the substrate 13 using a conducting film. Preferably, the conductive carbon ink of resistance in the range 15 ohms to 25 ohms is used to screen print the electrodes 1, 2, 3 and 4 on substrate 13. Contact pads 12 are at the top end of the electrodes and are used to provide the electrical connection with the connector 8 in Figure 1. Preferably, the width of the contact pads is the same for all four electrodes. An electrically insulating film 14 is screen printed on all the electrode surfaces except for the contact pads and the section of the electrodes identified as region 15.
- SPE screen-printed electrode
- Region 15 is the portion of the electrodes that come in contact with the sample containing the RBCs (5 in Figure 1) for determination of concentration of hemoglobin and glycated hemoglobin. Only the portion of electrode 4 that is to be immersed in the sample is modified using a water insoluble boronic acid compound and is shown as 16 in Figure 3. Additionally, the invention also relates to a non-enzymatic, electrochemical method for simultaneous measurement of total Hb and % HbAIc in blood sample using the SPE strip (as described above) comprising the steps of:
- step (b) removing the plasma to obtain red blood corpuscles (RBCs) either by decanting the plasma or by dipping a blotting paper strip in sample obtained in step (a) ;
- step (c) treating the sample containing the RBCs obtained in step (b) with a surfactant solution; (d) contacting the sample obtained in step (c) with the SPE strip;
- the blood sample collected from the patient is subjected to pre-treatment to separate red blood corpuscles (RBCs) from plasma by adding a lysis solution.
- Plasma is removed either by decanting or by dipping a blotting paper in the blood sample with lysis solution and the RBCs obtained are treated with the surfactant solution.
- the lysis solution may be selected from 50% ethanol; IM acetic acid (in water) 0.2M acetic acid (in water) 0.2M citric acid (in water); ethyl alcohol/water (1:1) and NaCl (in water).
- the ratio of the lysis solution to the sample is 1:1 to 1:20 (v/v), preferably, 1:10 (v/v).
- the surfactant may be selected from all types of cationic, anionic, e.g. ionic surfactants and preferably is selected from gemini surfactants, didodecyldimethylammonium bromide, cetyltrimethylammonium bromide, benzyltrimethylammonium bromide, phenacylthiazolium bromide, aminoguanidine hydrochloride, thiourea, phenacyl-thiazoliumZ-pyridinium bromide, sodium dodecylsulfate, sodium polystyrenesulfonate, and sodium salts of benzene- /naphthalene-mono-/di-/tri-sulfonic acids.
- the ratio of the surfactant to the sample of RBCs is 1:1 to 1:20 (v/v) and preferably 1:10 (v/v
- the SPE strip is introduced into the sample containing treated RBCs.
- a potential difference is generated due to reaction of HbAIc on the surface of the boronic acid modified electrode. This potential difference is measured with respect to the reference electrode and is converted into %HbAlc and displayed on the screen of a meter.
- a current signal is generated between electrodes 1, 2 and 3 proportional to the concentration of hemoglobin wherein the Fe 2 VFe 3+ reaction takes place on the electrode surface.
- the current signal is converted to g/dL of Hb and displayed on the screen of the meter.
- the functional details of the meter are shown in Figure 2.
- the dotted line separates the components of the Printed Circuit Board (PCB) comprising a preamplifier and Microcontroller Unit (MCU) modules.
- PCB Printed Circuit Board
- MCU Microcontroller Unit
- the Hb electrodes (electrode 1, 2 and 3) generate the current signal, which is subsequently converted into equivalent voltage signal through a current to voltage converter.
- the modified electrode directly generates a potential difference, which in turn is measured as a voltage signal.
- Both the voltage signals corresponding to Hb and HbAIc respectively are amplified through Instrumentation Amplifier.
- the Analog to Digital Converter (ADC) converts the amplified analog voltage signals to equivalent digital signals.
- the MCU processes the digital data and directly displays the Hb value in terms of g/dL and HbAIc as a percentage value on Alphanumeric Display. In an aspect of the present invention, both the values of total Hb and HbAIc are required to calculate the value of %HbAlc.
- the percentage of HbAIc is calculated as follows:
- %HbAlc [(HbAlc/total Hb) x 100].
- the entire analysis may be completed within five to ten minutes after collection of the blood.
- Hb and HbAIc can each be measured and quantified and there is no interference between the measurements and quantification of each as it pertains to the other.
- Figure 1 shows block diagram of how a typical analysis is carried out by connecting the SPE strip with the meter.
- the sample in vial 6 contains red blood corpuscles (RBCs) 5, which have been isolated from plasma.
- the surfactant solution preferably an ionic surfactant solution is added to vial 6 to preferentially release Heme proteins.
- the RBCs are mixed with the surfactant solution and can be analyzed.
- the SPE strip 7 is connected to the connector end 8 of the meter 10, through the cable 9.
- the sensor measures the concentration of Hb and HbAIc in the vial, the MCU calculates both Hb and HbAIc in g/dL and % unit respectively.
- the meter 10 indicates these values on the display 11.
- the present invention also relates to a kit for simultaneous measurement of total Hb and %HbAlc in blood sample comprising a SPE strip (as described above), a lysis solution, and a surfactant solution.
- the kit may also include a lancet, a blotting paper strip, an empty vial and an instruction insert.
- the lancet is used for pricking the skin so the blood can be collected in the empty vial.
- the instruction insert provides instructions for use of the kit.
- the insert may include instructions describing the steps needed to measure Hb and %HbAlc in the sample including describing how the blood is drawn, and mixed with the lysis and surfactant solutions.
- the invention thus provides a method for the estimation of %HbAlc and total Hb in a single step using a disposable, non-enzymatic screen-printed electrode strip, which incorporates electrodes for amperometry or differential pulse voltammetry and potentiometry.
- An example of an apparatus that can be used is a tabletop device that can be used in a medical practitioner's office.
- an apparatus that can be used may be operated by non-technically trained people.
- conductive carbon paste procured from Coates, Inc. (USA). This conductive carbon paste was used as an ink to print on the predetermined areas of the fibre- reinforced epoxy (FRE) substrates using a screen-printing process.
- FRE fibre- reinforced epoxy
- region 16 of electrode 4 of the SPE strip prepared in Example 1 was modified by dissolving 4-vinylphenyl boronic acid in iso-propyl alcohol (- 10 ml) and blended with the conductive carbon paste in 1:1 ratio (by weight) and was used for screen printing for potentiometric estimation of HbAIc from blood sample.
- the screen-printed carbon electrode of Example 1 was modified with a conducting polymer film (thickness: approx.5-10 ⁇ m) of amino phenyl boronic acid (PABA). It was electro-deposited on the carbon electrode using the electro- polymerization procedure/conditions, which are briefly described as follows: 3-amino phenyl boronic acid (0.04 M) of quantity 87.0 mg and sodium fluoride (0.2 M) of quantity 105.0 mg were dissolved in 12.5 ml of 0.2 M HCl solution.
- PABA amino phenyl boronic acid
- Polymerization was effected by dipping one of the screen-printed carbon electrodes in the above solution under unstirred conditions and the electrode potential was scanned between 0.0 and 1.1 V until the charge in the cathodic scan reached 10 mC cm "2 . A deep bluish-green film was obtained and it was washed with water. The electrode was thus modified and then rinsed with water, followed by PBS solution and it was ready for use.
- the standard hemoglobin sample (Catalog No. 400294022, Nicholas Piramal India Limited) (15 g/dl) was diluted ranging from concentration of 0.5g/dl to 1.9g/dl using the surfactant solution containing DDDMAB dissolved in 0.1M potassium chloride solution.
- the SPE strip, prepared in Example 1 was introduced into the above sample solution. Then the electrodes were connected to the potentiostat using appropriate connectors and the potential was swept between 0.1 to 0.8 volt at a scan rate of 100 mV/s. The peak current was measured in the peak potential range of 0.25 to 0.30 V. This was repeated with five standard samples and a calibration plot of "peak current vs. Hb concentration" was plotted.
- the standard hemoglobin sample (catalog no. 400294022, Nicholas Piramal India Limited) (15 g/dl) was diluted ranging from concentration of 0.5g/dl to 1.9g/dl using the surfactant solution containing didodecyldimethyl ammonium bromide (DDDMAB) dissolved in 0.1M potassium chloride solution.
- DDDMAB didodecyldimethyl ammonium bromide
- the SPE strip, prepared in Example 1 was introduced into the above sample solution. Then the electrodes were connected to the potentiostat using appropriate connectors in the differential pulse voltammetry (DPV) mode.
- DPV differential pulse voltammetry
- the potential was swept between -0.2 and 0.4 V at a scan rate of 5 mV/s using the parameters: step potential: 2 mV; pulse width: 50 mV; pulse period: 200 ms.
- the DPV peak current was measured in the above potential range. This was repeated with five standard samples and a calibration plot of "peak current vs. Hb concentration" was plotted. From the calibration plot, the slope of the graph was calculated and the latter was used for determination of total Hb in the test sample.
- a typical calibration plot and the electrode response for Hb in 5mM DDDMAB-IM KCl solution is shown in Figure 5A and 5B.
- the experimental calibration graph for Hb carried by differential pulse voltammetry, is linearly fitted by a straight line.
- Example 6 Calibration curve for estimation of Hb by differential pulse voltammetry using sodium dodecyl sulphate as the surfactant.
- the standard hemoglobin sample (Catalog No. 400294022, Nicholas Piramal India Limited) (15 g/dl) was diluted ranging from concentration of 0.5g/dl to 1.9g/dl using the surfactant solution containing sodium dodecyl sulphate (SDS) dissolved in 0.1M potassium chloride solution.
- SDS sodium dodecyl sulphate
- the SPE strip, prepared in Example 1 was introduced into the above sample solution. Then the electrodes were connected to the potentiostat using appropriate connectors and the potential was swept between 0.1 to 0.8 volt at a scan rate of 100 mV/s. The peak current was measured in the peak potential range of 0.25 to 0.30 V. This was repeated with five standard samples and a calibration plot of "peak current vs.
- Hb concentration was plotted. From the calibration plot, the slope of the graph was calculated and the latter was used for determination of total Hb in the test sample.
- a typical calibration plot and the electrode response for Hb in 5mM SDS - IM KCl solution is shown in the Figure 6.
- the experimental calibration graph for Hb, carried by differential pulse voltammetry, is linearly fitted by a straight line.
- Example 7 Calibration curve for estimation of %HbAlc by potentiometry using SPE strip modified by aminophenylboronic acid.
- a film of aminophenylboronic acid (PABA) was deposited on the glassy carbon electrode.
- 3-amino phenyl boronic acid (0.04 M) and sodium fluoride (0.2 M) were dissolved in hydrochloric acid (0.2M) solution.
- Polymerization was effected by keeping the working electrode in this solution along with platinum foil as counter electrode and saturated calomel as reference electrode. The electrode potential was scanned between 0.0 and 1.1 V for 3-5 scans. The modified electrode was then rinsed with water followed with PBS solution and used for further experiments. Based on these results, a linear relationship was established between concentration of HbAIc and the potential difference, enabling potentiometric estimation of the HbAIc as shown in the Figure 7.
- the graph line in figure 7 having square symbols ( ⁇ ) indicates the change in the potential difference of HbAIc as a function of concentration of HbAIc.
- the graph line in the figure with triangle symbols (A) indicate the change in the concentration of Hb alone. The separation of these two graph lines show that that there is no interference from Hb in the detection and quantification of HbAIc when both Hb and HbAIc are measured simultaneously.
- Example 8 Calibration curve for estimation of %HbAlc by potentiometry using SPE strip modified by water-soluble aminophenylboronic acid.
- SPE strip prepared in Example 1, was used for the experiment.
- Water-soluble aminophenylboronic acid (APBA) was dissolved in an electrolyte solution containing the sample and the consequent shift in electrode potential due to addition of HbAIc was measured.
- Aminophenylboronic acid in solution interacts with HbAIc, yielding a relationship between the concentration of HbAIc and the measured potential difference. This potential difference arises due to change in pKa value at the electrode surface. Based on these results, a linear relationship ( Figure 8) was established between concentration of HbAIc and the potential difference, enabling potentiometric estimation of HbAIc.
- This method estimates the potential of an electrode modified by a carbon ink of (water-insoluble) vinylphenylboronic acid, which was immersed in an electrolyte solution containing the sample (TruLab HbAIc liquid level 1 to level 4; Diagnostic System GmbH, Germany) and the consequent shift in electrode potential due to addition of HbAIc.
- This modified electrode interacts with HbAIc, yielding a relationship between the concentration of HbAIc and the measured potential difference. This potential difference arises due to change in pKa value at the electrode surface. Based on these results, a linear relationship was established between concentration of HbAIc and the potential difference, enabling potentiometric estimation of HbAIc as shown in the Figure 9. This experiment demonstrates the linear relationship between HbAIc and potential difference.
- Figure 9 shows the potentiometric estimation of HbAIc by using an electrode that has been modified with carbon ink using water-insoluble 4-phenyl- vinyl boronic acid (the graph line having square symbols ⁇ )and an electrode that has been modified with carbon ink using 3-thiophene boronic acid (the graph line with triangle symbols A).
- Hb and %HbAlc Measurement of total Hb and %HbAlc from a patient's blood sample.
- a blood sample from a diabetic patient was collected at a clinical laboratory. 20 ⁇ L of blood sample was taken in a test vial and 200 ⁇ L of lysis solution consisting of 50% ethanol was added. The vial was kept for two minutes without shaking so that plasma was separated from RBCs. The separated plasma was decanted by tilting the vial. RBC, being a thick fluid did not flow out of the vial while decanting the plasma. Then, 200 ⁇ L of surfactant 5mM ionic surfactant, cetyl trimethyl ammonium bromide (CTAB) was added and the solution was manually shaken approximately for a minute for mixing of RBC with the surfactant solution.
- CTL cetyl trimethyl ammonium bromide
- the solution was ready for analysis.
- the SPE strip modified by 4-phenyl-vinyl-boronic acid was inserted in the vial.
- a potential difference was generated due to reaction of HbAIc on the surface of boronic acid modified electrode which was measured with respect to the reference electrode and was converted into %HbAlc and displayed on the screen of the meter.
- a current signal generated between electrodes 1, 2 and 3 proportional to the concentration of hemoglobin was converted to g/dL of Hb and displayed on the screen of the meter.
- the Hb concentration was 10.52 g/dl and the %HbAlc value was 9.3%.
- Sample from the same patient was analysed using Chloestech GDX AlC testing system and HbAIc was estimated to be 9.2%.
Abstract
Description
Claims
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EP09786300A EP2359146A1 (en) | 2008-10-14 | 2009-02-02 | Non-enzymatic electrochemical method for simultaneous determination of total hemoglobin and glycated hemoglobin |
MX2011003952A MX2011003952A (en) | 2008-10-14 | 2009-02-02 | Non-enzymatic electrochemical method for simultaneous determination of total hemoglobin and glycated hemoglobin. |
BRPI0914373A BRPI0914373A2 (en) | 2008-10-14 | 2009-02-02 | "non-enzymatic electrochemical method for simultaneous determination of total hemoglobin and glycosylated hemoglobin" |
AU2009305121A AU2009305121A1 (en) | 2008-10-14 | 2009-02-02 | Non-enzymatic electrochemical method for simultaneous determination of total hemoglobin and glycated hemoglobin |
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EP (1) | EP2359146A1 (en) |
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US8702931B2 (en) | 2011-04-18 | 2014-04-22 | Indian Institute Of Science | Low cost electrochemical disposable sensor for measuring glycated hemoglobin |
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GB2551943B (en) | 2012-04-13 | 2018-08-01 | Smartcare Tech Limited | Improvements in and relating to sample measurement |
US10564123B2 (en) | 2014-05-25 | 2020-02-18 | United Arab Emirates University | Bioreactor system and method of operating same for cellular composition identification and quantification |
EP3190970B1 (en) * | 2014-09-08 | 2023-08-16 | Indian Institute of Science | Device and method for detection of haemoglobin and its complexes |
US11435344B2 (en) * | 2014-09-08 | 2022-09-06 | Indian Institute Of Science | Electrochemical biosensor and a method of sensing albumin and its complexes |
US10640801B2 (en) * | 2015-09-25 | 2020-05-05 | The Board Of Regents Of The University Of Texas System | Devices and methods using modified paper electrodes for the detection of hemoglobin A1C and glucose |
US11703513B2 (en) * | 2017-08-07 | 2023-07-18 | Polymer Technology Systems, Inc. | Systems and methods for enzymatic A1C detection and quantification |
EP3887398A4 (en) | 2018-11-29 | 2022-10-19 | Polymer Technology Systems, Inc. | Systems and methods for electrochemical point-of-care detection of hemoglobin |
GB2591455B (en) * | 2020-01-21 | 2022-08-17 | Univ Of Colombo | Nonenzymatic electrochemical sensors |
US20220221423A1 (en) * | 2020-03-26 | 2022-07-14 | Universiti Malaya | An electrochemical sensor for detecting and characterizing a biological material |
US11852577B2 (en) | 2021-09-29 | 2023-12-26 | Orange Biomed Ltd., Co. | Apparatus for measuring properties of particles in a solution and related methods |
US11747348B2 (en) * | 2021-09-29 | 2023-09-05 | Orange Biomed Ltd., Co. | Apparatus for measuring glycation of red blood cells and glycated hemoglobin level using physical and electrical characteristics of cells, and related methods |
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- 2009-02-02 AU AU2009305121A patent/AU2009305121A1/en not_active Abandoned
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- 2009-02-02 BR BRPI0914373A patent/BRPI0914373A2/en not_active IP Right Cessation
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Cited By (1)
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US8702931B2 (en) | 2011-04-18 | 2014-04-22 | Indian Institute Of Science | Low cost electrochemical disposable sensor for measuring glycated hemoglobin |
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BRPI0914373A2 (en) | 2015-10-20 |
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