WO2014092543A1 - A calcium ion selective sensor - Google Patents
A calcium ion selective sensor Download PDFInfo
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- WO2014092543A1 WO2014092543A1 PCT/MY2013/000244 MY2013000244W WO2014092543A1 WO 2014092543 A1 WO2014092543 A1 WO 2014092543A1 MY 2013000244 W MY2013000244 W MY 2013000244W WO 2014092543 A1 WO2014092543 A1 WO 2014092543A1
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- calcium ion
- selective sensor
- layer
- thiophene
- calcium
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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
- G01N27/308—Electrodes, e.g. test electrodes; Half-cells at least partially made of carbon
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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
- G01N27/333—Ion-selective electrodes or membranes
- G01N27/3335—Ion-selective electrodes or membranes the membrane containing at least one organic component
Definitions
- the present invention relates toa calcium ion selective sensor and method of producing the same more particularly a measurement system incorporating the same.
- Biosensors have been employed as an alternative for rapid measurement of body metabolites such as glucose, urea, and uric acid. Most commercially available biosensor strips exploit enzymes as the main recognising agent to give selectivity. Enzymes, being protein in nature, denatures at room temperature, undergoing structural changes due to environmental influence. Furthermore, when immobilised on sensing electrode surface, certain active groups of the enzyme form covalent bonding, which can result in the loss of critical functions which significantly decreases the accuracy of enzymatic biosensors. Therefore there is a need to design chemical sensors and biosensors of low price, easy preparation and ambulatory use, where the use of conducting polymers in these sensors potentially fulfils all these characteristics. Calcium sensors have been shown to be very effective tools for analysis of a wide variety of cations and anions. They are very simple to use, inexpensive, and capable of reliable responses in a wide concentration range.
- electrochemical sensors for calcium sensors have two-electrode system provided with working electrodes, which sensitively respond to species of interest, and reference electrodes, which maintain constant potentials without responding to the species.
- the working electrodes measure not values of absolute potentials, but values relative to the constant potential of the reference electrodes, that is, potential differences.
- the present invention further introducesa novel a sensing layer for calcium ion-selective sensor.
- the present invention further provides a considerable reduction of materials with even greater efficiency and economically during operation.
- the present invention provides acalcium ion-selective sensor comprising a substrate, a carbon layer as conductor layer provided on the substrate, a transducer layer for converting a chemical activity to an electrical signal and a sensing layer for detecting ions.
- the transducer layer is an electrochemical transducer and deposited on the carbon layer and the sensing layer is a conductive polymer sensing layer.
- the conductive polymer sensing layer is selected from a polymer layer having a combination of one portion of thiophene and one portion of 3-thiophene malonic acid.
- the conductive polymer sensing layer is selected from a polymer layer having a combination of one portion of 3-alkyl thiophene and one portion of 3-thiophene malonic acid.
- a calcium ion-selective sensor system comprising a reference electrode as reference potential, a calcium ion-selective sensor comprising a substrate, a carbon layer as conductor layer provided on the substrate, a transducer layer for converting a chemical activity to an electrical signal and a sensing layer for detecting ions wherein the reference electrode and the calcium ion-selective sensor are connected to an ion meter for measuring concentration of the ions in a sample.
- the reference electrode is a double- junction reference electrode and a buffer solution wherein the reference electrode and the calcium ion-selective sensor are immersed in the buffer solution.
- a method of preparing a sensing layer for calcium ion-selective sensor comprisingpreparing an organic polymer solution in organic solvent having at least one percent of the organic polymer by weight, mixing the organic polymer solution with monomers of thiophene, 3-alkyl thiophene, 3-thiophene-malonic acid to form a homogenous polymer solution having at least one percent of the monomers by weight, providing a polymerization reaction for the thiophene monomers in homogenous solution with organic poiymer solution using chemical oxidant process and heating the mixture at least 50 °C and for at least 10 minutes, depositing formation of polythiophene-organic polymer solution on the transducer layer of the calcium ion-selective sensor and evaporating the organic solvent.
- a method of measuring ions concentration in a sample having body metabolite using the calcium ion-selective sensor system compnsingconnecting a calcium ion-selective sensor and a reference electrode to a calcium measurement circuit, immersing the calcium ion- selective sensor and the reference electrode into a standard solution of predetermined ions with electrolyte having concentration from 0.1 M to 0.00001 M, recording a standard potential signal, plotting a graph of the standard potential signal (mV) versus log of predetermined ions concentration and deducing a linear equation from the graph, measuring a sample having body metabolitesusing the calcium ion-selective sensor and the reference electrode, recording a potential value generatedfrom the sample and converting the potential value of the sample into ions concentration as determined using the linear equation from the graph.
- mV standard potential signal
- the ions concentration is calcium ions concentration and potassium ions concentration.
- Figure 1 illustrates a schematic diagram of calcium ion-selective sensor in accordance of the present invention.
- Figure 2 illustratesa schematic diagram of a calcium ion-selective sensor system in accordance of the present invention.
- Figure 3 illustrates a graph of a response of selective calcium sensor with one part of thiophene and one part of 3-thiophene malonic acid in 0.1 M to 0.00001 M of KCI solution in accordance of the present invention.
- Figure 4 illustrates a graph of a response of selective calcium sensor with one part of thiophene and one part of 3-thiophene malonicacid in 0.1 M to 0.00001 M of CaCI 2 solutionin accordance of the present invention.
- Figure 5 illustrates a graph of a response of selective calcium sensor with 3-thiophene malonic acid alone in 0.1 M to 0.00001 M of KCI solution in accordance of the present invention.
- Figure 6 illustrates a graph of a response of selective calcium sensor with 3-thiophene malonic acid alone in 0.1 M to 0.00001 M of CaCI 2 solution in accordance of the present invention.
- the present invention relates to a calcium ion-selective sensor(100) comprising a substrate(102), a carbon layer (103) as conductor layer provided on the substrate, a transducer layer (104)for converting a chemical activity to an electrical signal and a sensing layer (105)for detecting ions as illustrated in Figure 1.
- the transducer layer(104) used in the present invention is an electrochemical transducer and deposited on the carbon layer(103).
- the sensing layer (105) of the present invention is a conductive polymer sensing layer.
- the conductive polymer sensing layer of the present invention preferably is selected from a polymer layer having a combination of one portion of thiophene and one portion of 3- thiophene malonic acid.
- the conductive polymer sensing layer is selected from a polymer layer having a combination of one portion of 3-alkyl thiophene and one portion of 3-thiophene malonic acid.
- the conductive polymer sensing layer further having a compound selected from the group consisting of a compound having the general formula I:
- a sensing layer for calcium ion-selective sensor comprising preparationan organic polymer solution in organic solvent having at least one percent of the organic polymer by weight. This is followed by mixing the organic polymer solution with monomers of thiophene, 3-alkyl thiophene, 3-thiophene-malonic acid to form a homogenous polymer solution having at least one percent of the monomers by weight. Then, a polymerization reaction for the thiophene monomers in homogenous solution with organic polymer solution using chemical oxidant process provided and the mixture is heated at least 50 °C and for at least 10 minutes. Subsequently, the formation of polythiophene-organic polymer solution is deposited on the transducer layer of the calcium ion-selective sensor. Finally, the additional organic solvent is evaporated in gas flow.
- a novel calcium PVC-based membrane sensor based on self-transduced malonic acid functionalized conductive polymer displays a linear dynamic range between LOxlO ⁇ andLOxlO ⁇ M, with a near Nernstian slope of 28.5 ⁇ 0.5 mV per decade and a detection limit of 8.0x10 "7 M.
- the best performance of the calcium ion-selective sensor is obtained with a membrane composition of 30% polyvinyl chloride), 62% nitrobenzene, 5% sodium tetraphenyl borate and 3% 3-alkyl thiophene and thiophene-3-malonic acid.
- the calcium response of the electrode of the calcium ion-selective sensor is stable even when the pH of the solutions is changed ( 4.0 -11.5 pH range).
- the calcium ion-selective sensor further possesses the advantages of short conditioning time, fast response time ( ⁇ 20 s), and especially, a good selectivity towards alkali and alkaline earth, and some mono, di and trivalent cations, such as Li + , Na + , K + , Mg 2+ , Sr 2* , Ba 2+ , Ag + , Cu 2+ , Al 3+ , La 3+ and Ce 3+ ions.
- the electrode of the calcium ion-selective sensor can be used for at least 10 weeks without any considerable divergence in the potentials. It is used as an indicator electrode in calcium titration of calcium(ll) ions with Ethylenediaminetetraacetic acid (EDTA).
- FIG 2 illustrates a calcium ion-selective sensor system in accordance of the present invention.
- the calcium ion-selective sensor system comprising a reference electrode as reference potential and a calcium ion-selective sensor as illustrated in Figure 1 for determination the concentration of calcium ions or potassium ions such that the reference electrode and the calcium ion-selective sensor are connected to an ion meter for measuring concentration of the ions in a sample.
- the reference electrode used in the present invention preferably a double-junction reference electrode. It is not necessary to have the test solutions buffered for calibration purposes, however buffering a test solution is an option in the present invention.
- the reference electrode and the calcium ion-selective sensor are immersed in the buffer solution.
- the calcium ion-selective sensor system of the present invention is used for measuring calcium and potassium ions level in body metabolites.
- Fabrication of carbon electrode was carried out through chemical oxidation.
- the solution of organic polymerin organic solvent comprising of at least one percent organic polymer by weight was prepared.
- organic solvents selected from tetrahydrofuran and dichloromethane.
- Thiophene, 3-alkyl thiophene, 3-thiophene malonic acid monomers were mixed to form a homogenous polymer solution.
- the polymerization of the monomers was done with chemical oxidant and the mixture was heated at least 50 °C for at least 10 minutes.
- the polythiophene-organic polymer solution was deposited on the carbon electrode surface and organic solvent was evaporated in gas flow.
- the polythiophene copolymer was deposited following the above procedures with one part of thiophene and one part of 3-thiophene malonic acid.
- the sensing electrode and double- junction reference electrode were immersed into the varied concentration of ammonia solution and connected to an ion meter.
- the reading was recorded from low to high concentration of potassium solutions as illustrated in Figure 3 followed by calcium solutions as shown in Figure 4.
- the data were plotted with the emf values (mV) in the y-axis and the log activity of ammonia in the x-axis.
- a slope of 12.89 mV/decade with good correlation is observed in keeping with positive charge built up on the sensor surface as depicted in Figure 4 along with the CaCI 2 solution at different concentrations.
- the coefficient calculation (at 0.1 M) on the sensor ions selectivity the sensor is more selective towards calcium ions by 47X.
- the poly(3-thiophene malonic acid) was deposited following the above procedures.
- the sensing electrode and double-junction reference electrode were immersed into the ammonia solution at concentration varied from 0.1 M to 0.00001 M and connected to an ion meter.
- the reading was recorded from low to high concentration of KCL and CaCI 2 .
- the data were plotted with the emf values (mV) in the y-axis and the log activity of K + as illustrated in Figure 5 and Ca 2+ as shown in Figure 6 in the x-axis.
- a slope of 23.775mV/decade with very good correlation is observed in keeping with positive charge built up on the sensor surface as depicted in Figure 6.
- the above method provides a rapid, standardisedcalcium assay which may be used to quickly evaluate the analytical sensitivity of a given calcium sensor and to determine the effect of, for example, changes in the composition of the electrochemical polymerisation solution on the final analytical sensitivity of the sensor.
- Analytical sensitivity is preferably evaluated relative to a standard or reference sensor, which is selected by the user.
- the standard or reference sensor is chosen merely to provide a basis line (or reference line) against which other sensors may be compared.
- One of the advantages of the present invention provides a calcium ion-selective sensor for havingcharacterisation of functionalised monomers that can be conveniently polymerised to form conducting polymers, nanoparticles and nanowires, and employed as chemical and biosensors targeting body metabolites.
- the monomers comprise aromatic heterocyclic nuclei.
- One or more functional substituents are covalently bonded to carbon or heteroatoms, having binding affinity towards metabolites thus having recognition characteristics towards ionic metabolites such as potassium, sodium, ammonium, hydrogen ions, chloride, phosphate and sulfate are of medical interest.
- biomolecule recognising substituents are of importance for glucose, uric acid, urea, cholesterol, creatine, creatinine and lactate determination.
- the calcium ion-selective sensor of the present invention is that it can be used to monitor health condition of an individual by monitoring the levels of calcium and potassium in the body.
- the calcium ion-selective sensor further possesses the advantages of short conditioning time, fast response time ( ⁇ 20 s), and especially, a good selectivity towards alkali and alkaline earth, and some mono, di and trivalent cations, such as Li + , Na + , K + , Mg 2+ , Sr 2* , Ba 2+ , Ag + , Cu 2+ , Al 3 ⁇ La 3+ and Ce 3+ ions.
- the electrode of the calcium ion-selective sensor can be used for at least 10 weeks without any considerable divergence in the potentials.
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Abstract
A calcium ion selective sensor and method of producing the same more particularly a measurement system incorporating the same. One of the advantages of the present invention provides a calcium ion-selective sensor comprising a substrate; a carbon layer as conductor layer provided on the substrate; a transducer layer for converting a chemical activity to an electrical signal;and a calcium sensing layer for detecting ions comprising a malonic acid functionalized conductive polymer. The functionalised monomers that can be conveniently polymerised to form conducting polymers, nanoparticles and nanowires, and employed as chemical and biosensors targeting body metabolites. The monomers comprise aromatic heterocyclic nuclei. One or more functional substituents are covalently bonded to carbon or heteroatoms, having binding affinity towards metabolites thus having recognition characteristics towards ionic metabolites such as potassium, sodium, ammonium, hydrogen ions, chloride, phosphate and sulfate are of medical interest. Likewise, biomolecule recognising substituents are of importance for glucose, uric acid, urea, cholesterol, creatine, creatinine and lactate determination. Another advantage of the calcium ion-selective sensor is that it can be used to monitor health condition of an individual by monitoring the levels of calcium and potassium in the body.
Description
A CALCIUM ION SELECTIVE SENSOR
FIELD OF THE INVENTION
The present invention relates toa calcium ion selective sensor and method of producing the same more particularly a measurement system incorporating the same.
BACKGROUND OF THE INVENTION
Biosensors have been employed as an alternative for rapid measurement of body metabolites such as glucose, urea, and uric acid. Most commercially available biosensor strips exploit enzymes as the main recognising agent to give selectivity. Enzymes, being protein in nature, denatures at room temperature, undergoing structural changes due to environmental influence. Furthermore, when immobilised on sensing electrode surface, certain active groups of the enzyme form covalent bonding, which can result in the loss of critical functions which significantly decreases the accuracy of enzymatic biosensors. Therefore there is a need to design chemical sensors and biosensors of low price, easy preparation and ambulatory use, where the use of conducting polymers in these sensors potentially fulfils all these characteristics. Calcium sensors have been shown to be very effective tools for analysis of a wide variety of cations and anions. They are very simple to use, inexpensive, and capable of reliable responses in a wide concentration range.
Typically, electrochemical sensors for calcium sensors have two-electrode system provided with working electrodes, which sensitively respond to species of interest, and reference electrodes, which maintain constant potentials without responding to the species. The working electrodes measure not values of absolute potentials, but values relative to the constant potential of the reference electrodes, that is, potential differences.
To minimize electrochemical analyzers of the calcium sensors, it is essential to reduce the dimensions of electrode systems. Therefore, there isa need for an improved calcium ion- selective sensor and a method of measuring ions concentration in a sample having body
metabolite using the calcium ion-selective sensor system.The present invention further introducesa novel a sensing layer for calcium ion-selective sensor. The present invention further provides a considerable reduction of materials with even greater efficiency and economically during operation.
SUMMARY OF THE INVENTION
The present invention provides acalcium ion-selective sensor comprising a substrate, a carbon layer as conductor layer provided on the substrate, a transducer layer for converting a chemical activity to an electrical signal and a sensing layer for detecting ions.
In one of the embodiment of the present invention, the transducer layer is an electrochemical transducer and deposited on the carbon layer and the sensing layer is a conductive polymer sensing layer.
In yet another embodimentof the present invention, the conductive polymer sensing layer is selected from a polymer layer having a combination of one portion of thiophene and one portion of 3-thiophene malonic acid.
In another of the embodiment of the present invention, the conductive polymer sensing layer is selected from a polymer layer having a combination of one portion of 3-alkyl thiophene and one portion of 3-thiophene malonic acid. A calcium ion-selective sensor system comprising a reference electrode as reference potential, a calcium ion-selective sensor comprising a substrate, a carbon layer as conductor layer provided on the substrate, a transducer layer for converting a chemical activity to an electrical signal and a sensing layer for detecting ions wherein the reference electrode and the calcium ion-selective sensor are connected to an ion meter for measuring concentration of the ions in a sample.
In one of the embodiment of the present invention, the reference electrode is a double- junction reference electrode and a buffer solution wherein the reference electrode and the calcium ion-selective sensor are immersed in the buffer solution.
A method of preparing a sensing layer for calcium ion-selective sensor comprisingpreparing an organic polymer solution in organic solvent having at least one percent of the organic polymer by weight, mixing the organic polymer solution with monomers of thiophene, 3-alkyl thiophene, 3-thiophene-malonic acid to form a homogenous polymer solution having at least one percent of the monomers by weight, providing a polymerization reaction for the thiophene monomers in homogenous solution with organic poiymer solution using chemical oxidant process and heating the mixture at least 50 °C and for at least 10 minutes, depositing formation of polythiophene-organic polymer solution on the transducer layer of the calcium ion-selective sensor and evaporating the organic solvent.
A method of measuring ions concentration in a sample having body metabolite using the calcium ion-selective sensor system compnsingconnecting a calcium ion-selective sensor and a reference electrode to a calcium measurement circuit, immersing the calcium ion- selective sensor and the reference electrode into a standard solution of predetermined ions with electrolyte having concentration from 0.1 M to 0.00001 M, recording a standard potential signal, plotting a graph of the standard potential signal (mV) versus log of predetermined ions concentration and deducing a linear equation from the graph, measuring a sample having body metabolitesusing the calcium ion-selective sensor and the reference electrode, recording a potential value generatedfrom the sample and converting the potential value of the sample into ions concentration as determined using the linear equation from the graph.
In another of the embodiment of the present invention.the ions concentration is calcium ions concentration and potassium ions concentration.
BRIEF DESCRIPTION OF THE DRAWINGS
The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate embodiments of the invention and, together with the description, serve to explain the principles of the invention. Figure 1 illustrates a schematic diagram of calcium ion-selective sensor in accordance of the present invention.
Figure 2illustratesa schematic diagram of a calcium ion-selective sensor system in accordance of the present invention.
Figure 3 illustrates a graph of a response of selective calcium sensor with one part of thiophene and one part of 3-thiophene malonic acid in 0.1 M to 0.00001 M of KCI solution in accordance of the present invention.
Figure 4 illustrates a graph of a response of selective calcium sensor with one part of thiophene and one part of 3-thiophene malonicacid in 0.1 M to 0.00001 M of CaCI2 solutionin accordance of the present invention. Figure 5 illustrates a graph of a response of selective calcium sensor with 3-thiophene malonic acid alone in 0.1 M to 0.00001 M of KCI solution in accordance of the present invention.
Figure 6 illustrates a graph of a response of selective calcium sensor with 3-thiophene malonic acid alone in 0.1 M to 0.00001 M of CaCI2 solution in accordance of the present invention.
DETAILED DESCRIPTIONS OF THE INVENTION
The present invention will now be described in detail in connection with specific embodiments with reference to the accompanying drawings.
The present invention relates to a calcium ion-selective sensor(100) comprising a substrate(102), a carbon layer (103) as conductor layer provided on the substrate, a transducer layer (104)for converting a chemical activity to an electrical signal and a sensing layer (105)for detecting ions as illustrated in Figure 1. The transducer layer(104) used in the present invention is an electrochemical transducer and deposited on the carbon layer(103). Further, the sensing layer (105) of the present invention is a conductive polymer sensing layer.Depending on the application, in one of the embodiment of the present invention, the conductive polymer sensing layer of the present invention preferably is selected from a polymer layer having a combination of one portion of thiophene and one portion of 3- thiophene malonic acid. In another embodiment of the present invention, the conductive polymer sensing layer is selected from a polymer layer having a combination of one portion
of 3-alkyl thiophene and one portion of 3-thiophene malonic acid. The conductive polymer sensing layer further having a compound selected from the group consisting of a compound having the general formula I:
(I)
To prepare a sensing layer for calcium ion-selective sensor comprising preparationan organic polymer solution in organic solvent having at least one percent of the organic polymer by weight. This is followed by mixing the organic polymer solution with monomers of thiophene, 3-alkyl thiophene, 3-thiophene-malonic acid to form a homogenous polymer solution having at least one percent of the monomers by weight. Then, a polymerization reaction for the thiophene monomers in homogenous solution with organic polymer solution using chemical oxidant process provided and the mixture is heated at least 50 °C and for at least 10 minutes. Subsequently, the formation of polythiophene-organic polymer solution is deposited on the transducer layer of the calcium ion-selective sensor. Finally, the additional organic solvent is evaporated in gas flow.
In one of the embodiment of the present invention, a novel calcium PVC-based membrane sensor based on self-transduced malonic acid functionalized conductive polymer. The calcium ion-selective sensor based on self-transduced malonic acid functionalized conductive polymer displays a linear dynamic range between LOxlO^andLOxlO^M, with a near Nernstian slope of 28.5 ± 0.5 mV per decade and a detection limit of 8.0x10"7M. The best performance of the calcium ion-selective sensor is obtained with a membrane composition of 30% polyvinyl chloride), 62% nitrobenzene, 5% sodium tetraphenyl borate and 3% 3-alkyl thiophene and thiophene-3-malonic acid. The calcium response of the electrode of the calcium ion-selective sensor is stable even when the pH of the solutions is changed ( 4.0 -11.5 pH range). The calcium ion-selective sensor further possesses the advantages of short conditioning time, fast response time (<20 s), and especially, a good
selectivity towards alkali and alkaline earth, and some mono, di and trivalent cations, such as Li+, Na+, K+, Mg2+, Sr2*, Ba2+, Ag+, Cu2+, Al3+, La3+and Ce3+ ions. The electrode of the calcium ion-selective sensor can be used for at least 10 weeks without any considerable divergence in the potentials. It is used as an indicator electrode in calcium titration of calcium(ll) ions with Ethylenediaminetetraacetic acid (EDTA).
Figure 2 illustrates a calcium ion-selective sensor system in accordance of the present invention. The calcium ion-selective sensor system comprising a reference electrode as reference potential and a calcium ion-selective sensor as illustrated in Figure 1 for determination the concentration of calcium ions or potassium ions such that the reference electrode and the calcium ion-selective sensor are connected to an ion meter for measuring concentration of the ions in a sample.
The reference electrode used in the present invention preferably a double-junction reference electrode. It is not necessary to have the test solutions buffered for calibration purposes, however buffering a test solution is an option in the present invention. For buffering a test solution, the reference electrode and the calcium ion-selective sensor are immersed in the buffer solution. Depending on the applications, the calcium ion-selective sensor system of the present invention is used for measuring calcium and potassium ions level in body metabolites.
In operation, for measuring ions concentration in a sample having body metabolites using the calcium ion-selective sensor system by first connecting a calcium ion-selective sensor and a reference electrode to a calcium measurement circuit. Then, both the calcium ion- selective sensor and the reference electrode are immersed into a standard solution of predetermined ionssuch as calcium ions, potassium ions and others with electrolyte having concentration from 0.1 M to 0.00001 M. Subsequently, a standard potential signal is recorded. A graph of the standard potential signal (mV) versus log of predetermined ions concentration is then plotted and a linear equation from the graph is deduced. For determination of the concentration of ions, a sample having body metabolitesis measured using the calcium ion-selective sensor and the reference electrode in the calcium ion- selective sensor system A potential value generatedfrom the sample is then recorded. Finally, the potential value of the sample is converted into ions concentration as determined using the linear equation from the graph.
EXAMPLE
Deposition of Polythiophene Derivative as Selective Calcium Sensor
Fabrication of carbon electrode was carried out through chemical oxidation. The solution of organic polymerin organic solvent comprising of at least one percent organic polymer by weight was prepared. Examples of organic solvents selected from tetrahydrofuran and dichloromethane. Thiophene, 3-alkyl thiophene, 3-thiophene malonic acid monomers were mixed to form a homogenous polymer solution. The polymerization of the monomers was done with chemical oxidant and the mixture was heated at least 50 °C for at least 10 minutes. The polythiophene-organic polymer solution was deposited on the carbon electrode surface and organic solvent was evaporated in gas flow.
Selective Calcium Sensor One Part of Thiophene and One Part of 3-Thiophene Malonic Acid
The polythiophene copolymer was deposited following the above procedures with one part of thiophene and one part of 3-thiophene malonic acid. The sensing electrode and double- junction reference electrode were immersed into the varied concentration of ammonia solution and connected to an ion meter. The reading was recorded from low to high concentration of potassium solutions as illustrated in Figure 3 followed by calcium solutions as shown in Figure 4. The data were plotted with the emf values (mV) in the y-axis and the log activity of ammonia in the x-axis. A slope of 12.89 mV/decade with good correlation is observed in keeping with positive charge built up on the sensor surface as depicted in Figure 4 along with the CaCI2 solution at different concentrations. Based on the coefficient calculation (at 0.1 M) on the sensor ions selectivity, the sensor is more selective towards calcium ions by 47X.
Selective Calcium Sensor with 3-Thiophene Malonic Acid Alone
The poly(3-thiophene malonic acid) was deposited following the above procedures. The sensing electrode and double-junction reference electrode were immersed into the ammonia solution at concentration varied from 0.1 M to 0.00001 M and connected to an ion meter. The reading was recorded from low to high concentration of KCL and CaCI2. The data were plotted with the emf values (mV) in the y-axis and the log activity of K+as illustrated in Figure 5 and Ca2+as shown in Figure 6 in the x-axis. A slope of 23.775mV/decade with very good
correlation is observed in keeping with positive charge built up on the sensor surface as depicted in Figure 6.
The above method provides a rapid, standardisedcalcium assay which may be used to quickly evaluate the analytical sensitivity of a given calcium sensor and to determine the effect of, for example, changes in the composition of the electrochemical polymerisation solution on the final analytical sensitivity of the sensor. Analytical sensitivity is preferably evaluated relative to a standard or reference sensor, which is selected by the user. The standard or reference sensor is chosen merely to provide a basis line (or reference line) against which other sensors may be compared.
One of the advantages of the present invention provides a calcium ion-selective sensor for havingcharacterisation of functionalised monomers that can be conveniently polymerised to form conducting polymers, nanoparticles and nanowires, and employed as chemical and biosensors targeting body metabolites. The monomers comprise aromatic heterocyclic nuclei. One or more functional substituents are covalently bonded to carbon or heteroatoms, having binding affinity towards metabolites thus having recognition characteristics towards ionic metabolites such as potassium, sodium, ammonium, hydrogen ions, chloride, phosphate and sulfate are of medical interest. Likewise, biomolecule recognising substituents are of importance for glucose, uric acid, urea, cholesterol, creatine, creatinine and lactate determination. Another advantage of the calcium ion-selective sensor of the present invention is that it can be used to monitor health condition of an individual by monitoring the levels of calcium and potassium in the body. The calcium ion-selective sensor further possesses the advantages of short conditioning time, fast response time (<20 s), and especially, a good selectivity towards alkali and alkaline earth, and some mono, di and trivalent cations, such as Li+, Na+, K+, Mg2+, Sr2*, Ba2+, Ag+, Cu2+, Al3\ La3+and Ce3+ions. The electrode of the calcium ion-selective sensor can be used for at least 10 weeks without any considerable divergence in the potentials.
The foregoing embodiment and advantages are merely exemplary and are not to be construed as limiting the present invention. The description of the embodiments of the present invention is intended to be illustrative and not to limit the scope of the claims and many alternatives, modifications and variations will be apparent to those skilled in the art.
Claims
1. A calcium ion-selective sensor comprising a substrate;
a carbon layer as conductor layer provided on the substrate;
a transducer layer for converting a chemical activity to an electrical signal;and
a sensing layer for detecting ions;
characterized by the sensing layer is a malonic acid functionalized conductive polymer for detecting calcium ions.
2. The calciumion-selective sensor as claimed in Claim 1 wherein the transducer layer is an electrochemical transducer and deposited on the carbon layer.
3. The calcium ion-selective sensor as claimed in Claim 1 wherein the conductive polymer is selected from a polymer layer having a combination of one portion of thiophene and one portion of 3-thiophene malonic acid.
4. The calcium ion-selective sensor as claimed in Claim 1 wherein the conductive polymer is selected from a polymer layer having a combination of one portion of 3-thiophene malonic acid and at least one portion of 3-alkyl thiophene or a polymer layer having a combination ofone portion of 3-thiophene malonic acid and at least one portion of thiophene.
5. A calcium ion-selective sensor system comprising
a reference electrode as reference potential;
a calcium ion-selective sensor comprising
a substrate;
a carbon layer as conductor layer provided on the substrate;
a transducer layer for converting a chemical activity to an electrical signal; and a sensing layer for detecting ions;
wherein the reference electrode and the calcium ion-selective sensor are connected to an ion meter for measuring concentration of the ions in a sample.
6. The calcium ion-selective sensor system as claimed in Claim 5 wherein the sensing layer is a malonic acid functionalized conductive polymer for detecting calcium ions.
7. The calcium ion-selective sensor system as claimed in claim 5 further comprising a buffer solution wherein the reference electrode and the calcium ion-selective sensor are immersed in the buffer solution.
8. A method of preparing a sensing layer for calcium ion-selective sensor comprising preparing an organic polymer solution in organic solvent having at least one percent of the organic polymer by weight; mixing the organic polymer solution with monomers of thiophene, 3-alkyl thiophene, 3- thiophene-malonic acid to form a homogenous polymer solution having at least one percent of the monomers by weight; providing a polymerization reaction for the thiophene monomers in homogenous solution with organic polymer solution using chemical oxidant process and heating the mixture at least 50 °C and for at least 10 minutes; depositing formation of polythiophene-organic polymer solution on the transducer layer of the calcium ion-selective sensor; and evaporating the organic solvent.
9. A method of measuring ions concentration in a sample having body metabolite using the calcium ion-selective sensor system comprising connecting a calcium ion-selective sensor and a reference electrode to a calcium measurement circuit; immersing the calcium ion-selective sensor and the reference electrode into a standard solution of predetermined ions with electrolyte having concentration from 0.1 M to 0.00001 M;
recording a standard potential signal; plotting a graph of the standard potential signal (mV) versus log of predetermined ions concentration and deducing a linear equation from the graph; measuring a sample having body metabolites using the calcium ion-selective sensor and the reference electrode; recording a potential value generatedfrom the sample;and converting the potential value of the sample into ions concentration as determined using the linear equation from the graph.
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| CN115825200A (en) * | 2022-11-07 | 2023-03-21 | 叶绿体(北京)生物医药有限公司 | Micro solid calcium ion selective electrode and preparation method thereof |
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