Patent Application
20230157577
This invention is in a field of material and chemical science relating to a non-invasive wearable sensor device for detecting biomarkers in secretion.
Nowadays, the innovation of wearable sensor device is widely used in the applications of health care and preliminary diagnosis in order to monitor patient's health condition and indicate the wearer's health abnormality. In particular, the wearable sensor device with a non-invasive design can detect the samples with a real-time and continuous analysis since it is created to be worn on the human body for health monitoring. Sweat is the most suitable sample for the wearable sensor device because it is secreted from the human skin which can be collected continuously and is less contaminated compared to other secretion samples, such as tear, saliva or urine, etc. In sweat, there are several biomarkers which can indicate the health condition and can be used for medical diagnosis, for example, glucose, lactate, urea, creatinine and uric acid.
Owing to the advantages mentioned above, the wearable sensor device has been developed to be more efficient to be used in a wide range of applications. In general, the principle of biomarker detection relies on the specific interaction with the bio-receptors, such as enzyme, antibody, nucleic acid and DNA, immobilized on the surface of the sensor. The reaction of the biological substances with the target biomarkers leads to physical and chemical changes, such as electron flow, oxygen generation, change in moisture, heat and color, which can be detected using different techniques.
The detection techniques commonly integrated with the wearable sensor device for determination of biomarkers in sweat are the colorimetric and electrochemical techniques. From previous studies, the sensor was provided on flexible polymer substrates, which is grooved as small channels called microfluidic channels, so the secretion sample can flow through the channels and reach the sensor.
Rogers et al. (US 2018/0064377 A1) developed a colorimetric wearable sensor device by using flexible polymer substrates to detect the sweat rate, pH and concentration of chloride, glucose and lactate in sweat.
Bandodkar et al. (Science Advances, 5, 1-15, 2019) developed a wearable sensor device for determination of glucose, lactate, chloride ion, pH and sweat rate by using the colorimetric and electrochemical techniques and the volumetric analysis.
Javey et al. (US 2018/0263539 A1) developed a wearable sensor device for detecting glucose, lactate, sodium ion and potassium ion in sweat by using electrochemical detection together with monitoring human body's temperature. The sensor device was developed by installing the sensor, detector and processor on flexible polymer substrates, and using microfluidic pattern as a detection system, therefore leading to the use of smaller amount of reagents and samples. However, this system must be delicately prepared because of its complicated pattern. Therefore, this complexity in the fabrication process results in a high production cost.
Additionally, Jia et al. (Analytical Chemistry, 85, 14, 6553-6560, 2013) designed a tattoo-based wearable sensor which has a capability to monitor lactate in sweat during exercise.
Bandodkar et al. (Analyst, 138, 1, 123-128, 2013) developed a tattoo-based sensor for glucose determination in order to diagnose diabetes. These mentioned studies utilize the electrochemical technique by installing the wearable sensors on polymer substrates. By using such substrates, the ventilation rate of human body is apparently decreased, causing dampness and irritation on the skin.
The development of sensors using textiles, especially thread, as a base material is an alternative approach for creating simple, low-cost wearable sensor devices owing to the self-microfluidic property and the small size of the thread compared to other base materials which help to reduce the amount of enzymatic assay and simplify the fabrication and design process of the flow channel, therefore leading to cost reduction. Previously, several researchers developed a textile-based colorimetric sensor as following examples.
Xiao et al. (Cellulose, 26, 4553-4562, 2019) developed a colorimetric wearable sensor based on a combination of thread and filter paper and sewed on cloth for detection of glucose in sweat. However, the filter paper is fragile and lacks robustness for wearers with high sweat rate.
Li et al. (Cellulose, 25, 4831-4840, 2018) developed a colorimetric sensor based on a thread for detection of glucose in urine using a knotted thread for colorimetric readout. This thread-based sensor is more durable than the paper-based sensor. Nonetheless, on the difficulty in controlling the knot size can lead to inconsistency and change in color and the uneven surface can cause difficulty in interpretation and error.
There are several studies on the development of electrochemical wearable sensors.
Wang et al. (US2019/0090809 A1) developed a wearable sensor using screen-printed carbon electrode on clothes to detect β-nicotiamide adenine dinucleotide (NADH), hydrogen peroxide (H2O2), potassium ferrocyanide, trinitrotoluene (TNT), dinitrotoluene (DNT) in liquid and gas phases using amperometry or potentiometry technique. Nevertheless, the fabrication of the screen-printed working electrode requires a large amount of carbon ink, and the carbon electrode can be severely damaged while stretching the clothes. In addition, in this study, there is no modification made to the electrode with a conductive material for enhancing the electrical conductivity; therefore, leading to a poor electron transfer reaction on the electrode surface. Furthermore, any highly specific biological substance was not used, so interferences in the sample can disturb the detection mechanism. Thus, this sensor has suboptimal performance compared to other studies, which improve the performance of the sensors by modifying or improving the property of electrodes with a conductive material and highly specific biological substances.
Liu et al. (Lab on a Chip, 16, 2093-2097, 2016) developed an embroidered electrochemical sensor by coating carbon ink on the thread and using it as working and counter electrodes. For reference electrode, the thread is coated by Ag/AgCl ink. Then, the working electrode is further coated by a specific enzyme to detect glucose and lactate in blood. In order to detect the analytes in the blood sample, blood drawing, which is an invasive procedure, unavoidably causes pain and damage to the sampling sites and some patients have limitations for blood drawing. Furthermore, the embroidered electrochemical sensor embroidered on bandages (Biosensors and Bioelectronics, 98, 189-194, 2017) was developed for detection of biomarkers in wounds, such as uric acid. This platform can be fabricated by coating carbon ink and Ag/AgCl ink on the threads, and then embroidering the bandages using the threads.
On the other hand, Liu et al. used merely carbon ink for electrode modification and used a specific enzyme for the analysis. There is no modification step using the conductive material, therefore leading to a poor electron transfer process which causes low sensitivity and inefficiency of the analyte detection. Therefore, the detection efficiency and sensitivity can be improved by electrode modifications.
A non-invasive wearable sensor device for detecting biomarkers in secretion of this invention was developed by using a combination of the colorimetric and electrochemical techniques to obtain a highly accurate and precise analysis. The invention uses a textile as a base material of the sensors because it has an outstanding self-microfluidity which allows self-absorption of the secretion samples. Moreover, this sensor can be readily fabricated at low cost while providing high efficiency and durability for being worn on human bodies. Herein, the novel sensor has been developed by modifying colorimetric and electrochemical sensor with a liquid absorber for high efficiency sample absorption and retention. In addition, it can increase the probability of absorbing and contacting with the target biomarkers in the secretion sample and the specific enzyme can be immobilized on the sensor even better. Moreover, modifying the base material using the liquid absorber before coating it with a conductive material and optionally a mediator on the electrochemical sensor can enhance the electrochemical conductivity of the sensor.
This sensor is not only suitable for the analysis of small amount of samples and highly sensitive to detection of the low concentration samples, but it can also be used for a simultaneous determination of various biomarkers in the samples by using the colorimetric technique in combination with the electrochemical technique for confirming the results in more accurate and precise manner.
This invention relates to a non-invasive wearable sensor device for detecting biomarkers in secretion. The sensor device comprises a colorimetric sensor comprising a base material coated with a liquid absorber, a colorimetric reagent and enzyme specific for target biomarkers, wherein when the colorimetric sensor contacts with the secretion, the enzyme specific for target biomarkers together with the colorimetric reagent causing the color change which is proportional to concentrations of the target biomarkers, and the colorimetric sensor is installed on a substrate such that it can be attached to and detached from the sensor device. The sensor device also comprises an electrochemical sensor comprising three electrodes, namely, a reference electrode (RE), a working electrode (WE) and a counter electrode (CE) that are installed on a substrate such that they can be attached to and detached from the sensor device. The electrochemical sensor is connected to an electrochemical detector and processor, and an end of those three electrodes is coated with a conductive material. The electrochemical detector and processor work together with the electrochemical sensor, and comprises a microcontroller, a real-time clock module, a battery as a power source, a button, a display and electrochemical circuits. The electrochemical circuit comprises an operational amplifier, a current source controller, a current-to-voltage converter, a digital-to-analog converter, analog-to-digital converters and a resistor. All components of the electrochemical detector and processor are electrically connected. The sensor device further comprises a housing to which the colorimetric sensor, electrochemical sensor and electrochemical detector and processor are installed. The housing is formed such that allows the colorimetric sensor and electrochemical sensor to contact with the secretion directly and continuously during wearing of the sensor device.
An object of this invention is to develop a non-invasive wearable sensor device for detecting biomarkers in secretion. The sensor device of this invention can be developed by using the base material which is a textile due to its self-microfluidity and high wearing comfort properties. The sensor is highly sensitive to detection of a trace level of secretion samples, therefore highly efficient and useful for tracking user's health status and enable the users to preliminary evaluate and record health information by themselves which would provide advantages in medical diagnosis. This can also facilitate the doctor and reduce the cost of hospital visits of the user. Therefore, this invention can improve people's life quality and reduce the medical cost for the government.
The present invention relates to a non-invasive wearable sensor device for detecting biomarkers in secretion which will be described by the following details with reference to the accompanying figures.
The sensor device of this invention comprising:
a colorimetric sensor (1) comprising a base material coated with a liquid absorber, a colorimetric reagent and enzyme specific for target biomarkers,
wherein when the colorimetric sensor (1) contacts with the secretion, the enzyme specific for target biomarkers together with the colorimetric reagent causing the color change which is proportional to concentrations of the target biomarkers, and the colorimetric sensor (1) is installed on a substrate (5) such that it can be attached to and detached from the sensor device;
an electrochemical sensor (2) comprising three electrodes, namely, a reference electrode (RE) (6), a working electrode (WE) (7) and a counter electrode (CE) (8) that are installed on a substrate (10) such that they can be attached to and detached from the sensor device, wherein the electrochemical sensor (2) is connected to an electrochemical detector and processor (3), and
an end of the three electrodes (9) is coated with a conductive material, and
the working electrode (7) comprises a base material which is coated with a conductive material, liquid absorber and enzyme specific for target biomarkers, and optionally a mediator, and
optionally, more than one colorimetric sensor (1) or electrochemical sensor (2) is installed on the sensor device in order to detect several biomarkers simultaneously, and when the secretion contacts with the electrochemical sensor (2), the enzyme specific for target biomarkers being on the working electrode (7) reacts with the target biomarkers causing a number of electrons on a surface of the working electrode (7) that are converted into current signals passing through the electrochemical detector and processor (3), the current signals being proportional to concentrations of the target biomarkers, and the electrochemical detector and processor (3) that works together with the electrochemical sensor (2) comprising:
wherein all components of the electrochemical detector and processor (3) are electrically connected and installed on a substrate, and
a number of the electrochemical circuits (11, 25) installed in the electrochemical detector and processor (3) corresponds to a number of the electrochemical sensor (2) installed on the sensor device;
a housing (4) to which the colorimetric sensor (1), electrochemical sensor (2), and electrochemical detector and processor (3) are installed,
wherein the housing (4) is formed such that allows the colorimetric sensor (1) and electrochemical sensor (2) to contact with the secretion directly and continuously during wearing of the sensor device, and
the housing (4) is made of a material that is selected from a group consisting of textile, paper, polymer, metal, ceramic and a combination thereof.
In one embodiment, the base material is made of a textile which is natural fiber, synthetic fiber, conductive fiber or a combination thereof, and is in a form of fiber, thread, fabric or a combination thereof.
The base material may be made of paper, polymer, metal, ceramic or a combination thereof.
The base material for the colorimetric sensor (1) and electrochemical sensor (2) can be made of the same or different material.
In a preferred embodiment, the mediator is selected from a group consisting of metal hexacyanoferrate, Prussian blue, cobalt hexacyanoferrate, cobalt phthalocyanine (CoPc), tetracyanoquinodimethane (TCNQ), potassium ferricyanide, ferrocene and its derivatives and a combination thereof.
The mediator has a concentration in a range of 0.001-10% by weight of the base material.
The liquid absorber is selected from a group consisting of positive ion, negative ion, carbon nanomaterial which is graphene or its derivatives, carbon nanotube, cationic or anionic polymer which is chitosan or its derivatives, cellulose or its derivatives, alginate or its derivatives, pullulan or its derivatives and a combination thereof.
The liquid absorber coated on the colorimetric sensor (1) and electrochemical sensor (2) has a concentration of in a range of 0.001-10% by weight of the base material.
The liquid absorber coated on the colorimetric sensor (1) and electrochemical sensor (2) can be the same or different material and comprise one or more types of material.
The colorimetric reagent is selected from a group consisting of aniline derivatives, i.e. N-ethyl-N-(3-sulfopropyl)-3-methoxyaniline, sodium salt, monohydrate (ADPS), N-ethyl-N-(3-sulfopropyl) aniline, sodium salt (ALPS), N-ethyl-N-(2-hydroxy-3-sulfopropyl)-3,5-dimethoxyaniline, sodium salt (DAOS), N-(2-hydroxy-3-sulfopropyl)-3,5-dimethoxyaniline, sodium salt (HDAOS), N,N-bis(4-sulfobutyl)-3,5-dimethylaniline, disodium salt (MADB), N-ethyl-N-(2-hydroxy-3-sulfopropyl)-3,5-dimethylaniline, sodium salt, monohydrate (MAOS), N,N-bis(4-sulfobutyl)-3-methylaniline, disodium salt (TODB), N-ethyl-N-(2-hydroxy sulfopropyl)-3-methylaniline, sodium salt, dihydrate (TOOS), N-ethyl-N-(3-sulfopropyl)-3-methylaniline, sodium salt, monohydrate (TOPS); benzidine derivatives, i.e. 3,3′-,5,5′-tetramethylbenzidine (TMBZ), 3,3′-,5,5′-tetramethylbenzidine, dihydrochloride, dihydrate, (TMB-HCl), 3,3-diaminobenzidine, tetrahydrochloride (DAB), 4-aminoantipyrine, potassium iodide; azo dyes; triphenylmethane dyes; fluorescent dyes; acridine dyes; miscellaneous dyes; anthraquinone dyes; sulfonephthalein dyes; benzein dyes; xanthene dyes; phthalein dyes; thiazole dyes; coumarin dyes; chalcone dyes; nitro dyes; heterocyclic dyes; polymethine dyes; flavone dyes; indigoid dyes; naphthalene dyes; azine dyes; oxazine dyes; hydrazide dyes; quinoline dyes; styryl dyes; oxazone dyes, i.e. bromocresol green, bromophenol red, methyl orange, methyl red, phenolphthalein, thymol blue, litmus, phenol red and a combination thereof.
The colorimetric reagent has a concentration in a range of 0.0001-10% by weight of the base material.
The enzyme specific for target biomarkers is selected from a group consisting of oxidase enzymes, i.e. glucose oxidase, horseradish peroxidase, lactate oxidase, cholesterol oxidase, creatinine amidohydrolase, urease and a combination thereof.
The enzyme specific for target biomarkers coated on the colorimetric sensor (1) and electrochemical sensor (2) has a concentration in a range of 0.01-1,000 units per gram of the base material.
The enzyme specific for target biomarkers coated on the colorimetric sensor (1) and electrochemical sensor (2) can be the same or different enzyme.
The reference electrode (6) is an ink or electrode which comprises carbon or Ag/AgCl as a main component.
The counter electrode (8) is an ink or electrode which comprises carbon, Ag/AgCl or platinum (Pt) as a main component.
The conductive material is selected from a group consisting of carbon-based nanomaterials, i.e. graphene or its derivatives, carbon nanotubes; metal-based nanoparticles, i.e. gold, silver, platinum, nickel, copper; conductive polymer, i.e. polyaniline, polypyrrole, poly(3,4-ethylenedioxy thiophene):polystyrene sulfonate; conductive ink or adhesive, i.e. Ag/AgCl ink, carbon ink; conductive tape, i.e. silver tape, copper tape and a combination thereof.
The conductive material coated on the working electrode (7) and the end of the three electrodes (9) has a concentration in a range of 1-1000% by weight of the base material.
The conductive material coated on the working electrode (7) and the end of the three electrodes (9) can be the same or different material.
The substrate of the colorimetric sensor (1), electrochemical sensor (2) and electrochemical detector and processor (3) is selected from a group consisting of textile, paper, polymer, metal, ceramic and a combination thereof.
The substrate of the colorimetric sensor (1), electrochemical sensor (2) and electrochemical detector and processor (3) can be the same or different material.
Referring to
Referring to
An exemplary embodiment of the colorimetric sensor (1) according to this invention is shown in
An exemplary embodiment of the electrochemical sensor (2) is shown in
As shown in
All components of the electrochemical detector and processor (3) are electrically connected and installed on the substrate. The number of electrochemical circuits in the electrochemical detector and processor (3) can be installed corresponding to the number of the electrochemical sensor (2) on the sensor device.
The housing (4) of the sensor device comprises an area for installing the colorimetric sensor (1), electrochemical sensor (2), and electrochemical detector and processor (3). The housing (4) is in a form that allows an attachment to human body, so the colorimetric sensor (1) and electrochemical sensor (2) contact with the secretion directly and continuously during wearing the sensor device. The housing (4) can be made of a material that is selected from a group consisting of textile, paper, polymer, metal, ceramic and a combination thereof.
Preparation of the Non-Invasive Wearable Sensor Device of this Invention
The Preparation of the Sensor Device can be Carried Out by the Following Steps.
a. Preparation of the Colorimetric Sensor (1)
The base material was cut to an appropriate size. Then, the liquid absorber was prepared as a solution with a concentration of 0.001-10% w/v. The solvent for the solution can be selected from water or acid solution, such as acetic acid, hydrochloric acid, and citric acid. After that, the base material was coated with the liquid absorber solution using a technique selected from immersion or dropping, and then left to dry at a room temperature. A multi-layer coating can be made by using the same or different coating material.
The enzyme specific for target biomarkers was prepared as a solution with a concentration of 1-1,000 units/mL. The enzyme was then immobilized on the base material using a technique selected from dropping, immersion or coating, and then left to dry at 20-30° C. for 5-60 min.
The colorimetric agent was prepared as a solution with a concentration of 0.001 to 10% w/v. The colorimetric agent was then used to coat the base material having the immobilized enzyme obtained from the above step. The coating technique can be selected from dropping, immersion or coating, and then left to dry at 20-30° C. for 5-60 min. Finally, the colorimetric sensor was installed on the substrate to absorb the secretion while the device is being worn.
b. Preparation of the Electrochemical Sensor (2)
Starting with a preparation of the working electrode (7), the base material was cut to an appropriate size, and then coated with the conductive material, which can be in various forms such as solid, liquid, suspension or solution. The concentration of the conductive suspension or solution is in a range of 20-70% w/w. The dispersant or solvent can be selected from water, organic solvent or a mixture of organic solvent. The conductive suspension or solution can additionally contain a mediator. The coating technique can be selected from dropping, immersion, coating or plating. The conductive suspension or solution was then dried out at 20-30° C. for 5-60 min. A multi-step coating can be carried out several times, typically 1-10 times. Then, the solution of liquid absorber was prepared with a concentration of 0.001-10% w/v by using water as a solvent. The base material was then coated with the liquid absorber solution using a technique selected from dropping, immersion, coating, and then left to dry at 20-30° C. for 5-60 min. The coating step using the liquid absorber solution can be done before and/or after the coating step using the conductive material. The multi-step coating can be carried out by using the same or different material. Then, the working electrode (7) prepared from the above explanation, reference electrode (6) and counter electrode (8) were installed on the substrate. Importantly, these three electrodes must contact with the secretion while the device is being worn, but each electrode must not contact with each other. Then, the end of three electrodes (9) were coated with the conductive material with a concentration of 20-70% w/w. The working electrode was immobilized with the enzyme with the concentration of 1-1000 unit/mL using a technique selected from dropping, immersion, coating, and then left to dry at 20-30° C. for 5-60 min.
c. Preparation of the Electrochemical Detector and Processor (3)
The electrochemical detector and processor (3) can be fabricated by connecting the circuit and assembling its components. The components comprise the microcontroller, real-time clock, button, display, battery and electrochemical circuit. The electrochemical circuit comprises the operational amplifier, current source controller, current-to-voltage converter, digital-to-analog converter, analog-to-digital converter and resistor. All components were installed on a substrate selected from textile, paper, polymer, metal, ceramic or a combination thereof. The components were connected electrically. The number of electrochemical circuits in the electrochemical detector and processor (3) which is installed corresponds to the number of electrochemical sensors on the device.
Upon connection of the electrochemical sensor (17) to the electrochemical circuit (11), the operational amplifier (18) measures the different voltage of the working electrode (WE) and reference electrode (RE). The different voltage is fed to the microcontroller (12) through the analog-to-digital converter (22). The different voltage is also fed back to the current source controller (19) through the negative input. The current source controller (19) measures the different voltage between the target voltage and the input voltage. The target voltage is determined by the microcontroller (12) through the digital-to-analog converter (21). The measured different voltage of the operational amplifier (18) affects the amount of electrical current fed to the sensor cell through the counter electrode (CE). For the WE and RE to have a determined voltage, a certain level of electrical current must be applied to the CE node. The current-to-voltage converter (20) has functions as follows.
Since the input impedance of the operational amplifier is very high, the electrical current from the sensor cell flows only through WE node across a resistor (24). This shows that the current-to-voltage converter (20) obtains voltage Vc at the analog-to-digital converter (23). The digital signal is fed into the microcontroller so that the current flowing into the sensor cell can be calculated using the equation I=Vc/Rm. The system also includes the battery (14) that is a power source which can be a disposable or rechargeable one. The system also includes the button (15) for changing modes and start the operation in each mode. The system also includes the display (16) for showing the measurement results and the real-time clock module (13) for a current timing signal.
d. Assembling of the Components on the Housing (4)
The assembling can be carried out by installing the colorimetric sensor (1), electrochemical sensor (2), and electrochemical detector and processor (3) on the housing (4), which can be selected from textile, paper, polymer, metal, ceramic or a combination thereof.
The mechanism of the sensor device of this invention is such that when the secretion sample directly contacts with the colorimetric agent, the immobilized specific enzyme will react with the target biomarker and decompose such biomarker. One of the products from the reaction is hydrogen peroxide, which reacts with the colorimetric agent, resulting in the change of color on the colorimetric sensor (1). As for the electrochemical sensor (2), as soon as the secretion sample contacts with the three electrodes, the specific enzyme immobilized on the working electrode (7) will decompose the target biomarker. One of the products from the reaction is hydrogen peroxide, which is a key compound for the electron transfer reaction. After the electron transfer reaction, there is an electrical current in the sensor system which can be detected by the electrochemical technique. The electrochemical detector and processor (3) will measure the current of the counter electrode (8) of the electrochemical sensor (2) on the condition that the voltage of the working electrode (7) and reference electrode (6) is constant. Thus, the current in the system varies directly with the concentration of the target biomarkers.
Exemplary embodiments of the sensor device of this invention include but not limit to the below examples.
Example 1: Certain exemplary techniques and fabrication processes of a wristwatch-based wearable sensor device for simultaneous detection of glucose and lactate in sweat are described below.
Step 1: Preparation of the Colorimetric Sensor (1)
Step 2: Preparation of the Electrochemical Sensor (2)
The thread coated with the carbon nanotube/Prussian blue/chitosan was used as the working electrode, which is ready for further specific modification for the target biomarker.
Preparation of the Counter Electrode (CE) (8) and Reference Electrode (RE) (6)
Preparation of the Working Electrode for Glucose Detection
Preparation of the Working Electrode for Lactate Detection
Step 3: Preparation of the Electrochemical Detector and Processor (3)
The circuit was connected and the components including a microprocessor, a real-time clock, a control button, a display, a battery and an electrochemical circuit, which is composed of an operational amplifier, a current source controller, a current-to-voltage converter, a digital-to-analog converter, an analog-to-digital converter, and a resistor are installed on a circuit board. Every component was assembled as shown in
Step 4: Assembling of Each Components on the Housing (4)
A housing (4) was designed as a wristwatch which has channels for insertion of the colorimetric sensor (1), electrochemical sensor (2), and electrochemical detector and processor (3). Each component mentioned above was assembled together.
Example 2: Certain exemplary techniques and fabrication of standard color chart will now be described.
Preparation of Standard Color Chart for Glucose
Preparation of Standard Color Chart for Lactate
Example 3: An example of the use of sensor device for simultaneous detection of glucose and lactate will now be described.
Best mode of the invention is as described in the detailed description of the invention.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2001001314 | Mar 2020 | TH | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/TH2020/000032 | 5/27/2020 | WO |
