Abstract:
The invention relates to a transdermal microneedle array patch for measuring a concentration of a hypodermal target molecule. The transdermal microneedle array patch includes a substrate, a microneedle unit, a signal processing unit and a power supply unit. The microneedle unit at least comprises a first microneedle set used as a working electrode and a second microneedle set used as a reference electrode, the first and second microneedle sets arranging on the substrate. Each microneedle set comprises at least a microneedle. The first microneedle set comprises at least a sheet having a through hole on which a barbule forms at the edge. One of the sheet provides the through hole from which the barbules at the edge of the other sheets go through, and the barbules are disposed separately.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    The invention relates to a transdermal microneedle array patch, particularly a transdermal microneedle array patch which obtains physiologic data of a human body by measuring the concentration of hypodermal target molecules. 
         [0003]    2. Description of the Related Art 
         [0004]    Tissue fluid is mainly contained in subcutaneous tissue and includes amino acids, sugars, fatty acids, coenzymes, hormones, neurotransmitters, salts and waste products from the cells. Moreover, the tissue fluid is also the major communication channel for cell and blood. The concentrations of the various components in the tissue fluid are useful for determining user&#39;s physiological conditions. 
         [0005]    The medicine will be slowly released over a long period in tissue fluid when the patient takes or injects the medicine. The concentration variation of medicine in the tissue fluid is continually monitored during development of medicine and clinical experiment. Therefore, the tissue fluid is commonly sampled to further examine or analyze in medical treatment of patient. 
         [0006]    The commercially available physiological examination instruments generally withdraw tissue fluid by using a needle piercing through stratum corneum. However, the patient may feel painful for this kind of invasive sampling way. Moreover, the patient may be infected by microorganism originally present on epidermis and entering the patient body as the stratum corneum is pierced by a needle. Transdermal sensor with array-arranged microneedles pricking through skin is developed to withdraw tissue fluid in painless and minimally-invasive way. 
         [0007]    The array-arranged microneedles of a transdermal sensor can be manufactured with standard semiconductor process such as photolithograph process and etching process. U.S. Pat. No. 7,344,499 discloses a process for manufacturing silicon microneedles. As can be seen from the second paragraph of the twelve column of this patent, firstly a silicon wafer with a first patterned photoresist layer is prepared. Next, a through hole is defined on the wafer by anisotropic etching. Afterward, a chromium layer is coated on the wafer and a second patterned photoresist layer is formed atop the through hole to function as circular etching mask. Next, the wafer is then etched to form outer tapered wall for the microneedles. However, the silicon-based microneedles are brittle and tend to break when the microneedles prick through user&#39;s skin. 
         [0008]    Alternatively, hollow microneedles with resin barbules are proposed, where the barbules are drilled by laser processing. Firstly, sheet with barbules is formed by extruding polyimide or polyether ether ketone, and then the barbules are drilled by laser to form hollow microneedles. However, the microneedles have compact size such that the barbules may have ragged edge after extrusion. Moreover, it is difficult to form a hollow microneedle with off-axis through hole or central through hole having uniform inner diameter by laser processing. 
       SUMMARY OF THE INVENTION 
       [0009]    One object of the present invention is to provide a transdermal microneedle array patch, where the transdermal microneedle array patch has microneedles made by punching or etching to have sufficient mechanical strength. The microneedle can be kept intact after the microneedle pricks user&#39;s skin for sensing. The microneedle has such structure that the sensing polymer can be advantageously coated on inner surface of the tip of the microneedle. The sensing polymer can be prevented from falling as the microneedle pricks user&#39;s skin for sensing. 
         [0010]    Accordingly, the present invention provides a transdermal microneedle array patch. The transdermal microneedle array patch includes a substrate, a microneedle unit, a signal processing unit and a power supply unit. The microneedle unit at least comprises a first microneedle set used as a working electrode and a second microneedle set used as a reference electrode, the first and second microneedle sets arranging on the substrate. Each microneedle set comprises at least a microneedle. The first microneedle set comprises at least a sheet having a through hole on which a barbule forms at the peripheral. One of the sheets provides the through hole from which the barbules at the edge of the other sheets go through, and the barbules are disposed separately. 
         [0011]    The microneedles of the working electrode of the transdermal microneedle array patch according to the invention may be subjected to surface modification, in view of the target molecule to be sensed. The target molecule may be a biological molecule, such as glucose, cortisol or fatty acids. Also, the target molecule may be a pharmaceutical molecule, such as antibiotics. The transdermal microneedle array patch of the present invention may be used for pharmaceutical monitoring during the administration of a medication for a chronic disease or a specific pharmaceutical. Personalized medication of a specific dosage or frequency of administration can be provided based on the individual metabolism of the pharmaceutical. 
         [0012]    The microneedle of the present invention has sufficient mechanical strength. The microneedle can be kept intact after the microneedle pricks user skin for sensing. Moreover, the microneedle has simple manufacture process, which is beneficial for mass production. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0013]      FIG. 1  shows the exploded view of the transdermal microneedle array patch according to an embodiment of the present invention from one viewing direction. 
           [0014]      FIG. 2  shows the exploded view of the transdermal microneedle array patch from another viewing direction. 
           [0015]      FIG. 3  shows a schematic exploded view of the microneedle unit according to an embodiment of the present invention. 
           [0016]      FIG. 4  is a top view of the microneedle set functioning as working electrode according to an embodiment of the present invention. 
           [0017]      FIG. 5  is a top view of the microneedle set functioning as working electrode according to another embodiment of the present invention. 
           [0018]      FIG. 6  is a top view of the microneedle set functioning as working electrode according to still another embodiment of the present invention. 
           [0019]      FIG. 7  is a top view of the microneedle set functioning as working electrode according to still another embodiment of the present invention. 
           [0020]      FIG. 8  shows a perspective of an assembled transdermal microneedle array patch according to an embodiment of the present invention. 
           [0021]      FIG. 9  shows a sectional of an assembled transdermal microneedle array patch according to an embodiment of the present invention. 
           [0022]      FIG. 10  is a partially sectional view of  FIG. 9 , where sensing polymer is coated on the barbules. 
           [0023]      FIG. 11  is a partially sectional view of  FIG. 9 , where sensing polymer is coated on a test strip. 
           [0024]      FIG. 12  shows a partially sectional view of an assembled transdermal microneedle array patch according to another embodiment of the present invention. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0025]    The features of the invention believed to be novel are set forth with particularity in the appended claims. The invention itself, however, may be best understood by reference to the following detailed description of the invention, which describes an exemplary embodiment of the invention, taken in conjunction with the accompanying drawings, in which: 
         [0026]      FIG. 1  shows the exploded view of the transdermal microneedle array patch according to an embodiment of the present invention from one viewing direction, and  FIG. 2  shows the exploded view of the transdermal microneedle array patch from another viewing direction. The transdermal microneedle array patch of the present invention mainly comprises a substrate  10 , a microneedle unit  20 , a flexible pad  30 , a signal processing unit  41 , a power supply unit  43  and a cover  50 , where the signal processing unit  41  and the power supply unit  43  are arranged on a circuit board  40 . 
         [0027]    According to an embodiment of the present invention, the microneedle unit  20  comprises a first microneedle set  22  used as a working electrode, a second microneedle set  24  used as a reference electrode, and a third microneedle set  26  used as a counter electrode. The flexible pad  30  has an opening  32  through which the microneedle unit  20  passes. The microneedle unit  20  further comprises electric conducting posts  21 ,  23 ,  25  to respectively and electrically connect to the contacts  42 ,  44  and  46  on the circuit board  40 . The transdermal microneedle array patch of the present invention uses the flexible pad  30  to have tight fit with the user&#39;s muscle during operating thereof. 
         [0028]    The signal processing unit  41  electrically connects to the microneedle unit  20  and receives a concentration data of hypodermal target molecules sensed by the microneedle unit  20 . The signal processing unit  41  generates a sensing signal manifesting the current physiological condition of user after processing the received concentration data. The power supply unit  43  provides working power to the transdermal microneedle array patch of the present invention. 
         [0029]      FIG. 3  shows a schematic exploded view of the microneedle unit  20  according to an embodiment of the present invention. The first microneedle set  22  comprises a first sheet  222  and a second sheet  224  stacked with the first sheet  222 . The first sheet  222  has at least one first through hole  2222  defined thereon, and a first barbule  2224  at peripheral of the first through hole  2222 . The second sheet  224  has at least one second through hole  2242  defined thereon, and a second barbule  2244  at peripheral of the second through hole  2242 , where the second barbule  2244  penetrates the first through hole  2222  to juxtapose the first barbule  2224 . The second sheet  224  of the first microneedle set  22  comprises barb  2246  at the peripheral thereof and matched with the aperture  102  defined on the substrate  10 . According to another embodiment, the second sheet  224  of the first microneedle set  22  comprises conductive pin  2248  at the peripheral thereof. The conductive pin  2248  can be inserted into a slot  104  defined on the substrate  10  to electrically connect to the conductive post  21 . 
         [0030]    Similarly, the second microneedle set  24  comprises a first sheet  242 . The first sheet  242  has at least one first through hole  2422  defined thereon, and a first barbule  2424  at peripheral of the first through hole  2422 . The first sheet  242  of the second microneedle set  24  comprises barb  2426  at the peripheral thereof and matched with the aperture  102  defined on the substrate  10 . According to another embodiment, the first sheet  242  of the second microneedle set  24  comprises conductive pin  2428  at the peripheral thereof. The conductive pin  2428  can be inserted into a slot  104  defined on the substrate  10  to electrically connect to the conductive post  23 . 
         [0031]    Similarly, the third microneedle set  26  also comprises a first sheet  262 . The first sheet  262  has at least one first through hole  2622  defined thereon, and a first barbule  2624  at peripheral of the first through hole  2622 . The first sheet  262  of the third microneedle set  26  comprises barb  2626  at the peripheral thereof and matched with the aperture  102  defined on the substrate  10 . According to another embodiment, the first sheet  262  of the third microneedle set  26  comprises conductive pin  2628  at the peripheral thereof. The conductive pin  2628  can be inserted into a slot  104  defined on the substrate  10  to electrically connect to the conductive post  25 . 
         [0032]    According to an embodiment of the present invention, the first microneedle set  22 , the second microneedle set  24 , and the third microneedle set  26  can be made by punching or etching process. The material of the barbules is selected from the group consisting of stainless steel, nickel, nickel alloy, titanium, titanium alloy, carbon nanotube, and silicon. The surface of the barbules is coated with biologically compatible metal. The material of the barbules can also be selected from the group consisting of polycarbonate, polymethacrylic acid, polytetrafluoroethylene, and polyester. The surface of the barbules is also coated with biologically compatible metal. Moreover, the height of the barbules is 300-600 micrometers; the base width of the barbules is 150-450 micrometers. The separation between tips of the barbules is 500-3000 micrometers. 
         [0033]    With reference to  FIGS. 4 to 7 ,  FIG. 4  is a top view of the microneedle set functioning as working electrode according to an embodiment of the present invention. The first microneedle set  22  comprises a first sheet  222  and a second sheet  224  stacked with the first sheet  222 . The first sheet  222  has at least one first through hole  2222  defined thereon, and a first barbule  2224  at peripheral of the first through hole  2222 . The second sheet  224  has at least one second through hole  2242  defined thereon, and a second barbule  2244  at peripheral of the second through hole  2242 , where the second barbule  2244  penetrates the first through hole  2222  to juxtapose the first barbule  2224 . 
         [0034]      FIG. 5  is a top view of the microneedle set functioning as working electrode according to another embodiment of the present invention. The first microneedle set  22  comprises a first sheet  222 , a second sheet  224  and a third sheet  226  stacked with each other. The first sheet  222  has at least one first through hole  2222  defined thereon, and a first barbule  2224  at peripheral of the first through hole  2222 . The second sheet  224  has at least one second through hole  2242  defined thereon, and a second barbule  2244  at peripheral of the second through hole  2242 . The third sheet  226  has at least one third through hole  2262  defined thereon, and a third barbule  2264  at peripheral of the third through hole  2262 . The second barbule  2244  and the third barbule  2264  penetrates the first through hole  2222  to juxtapose the first barbule  2224 , and the tips of the barbules are in right triangular arrangement from top view. 
         [0035]      FIG. 6  is a top view of the microneedle set functioning as working electrode according to still another embodiment of the present invention. The first microneedle set  22  comprises a first sheet  222 , a second sheet  224  and a third sheet  226  stacked with each other. The first sheet  222  has at least one first through hole  2222  defined thereon, and a first barbule  2224  at peripheral of the first through hole  2222 . The second sheet  224  has at least one second through hole  2242  defined thereon, and a second barbule  2244  at peripheral of the second through hole  2242 . The third sheet  226  has at least one third through hole  2262  defined thereon, and a third barbule  2264  at peripheral of the third through hole  2262 . The second barbule  2244  and the third barbule  2264  penetrates the first through hole  2222  to juxtapose the first barbule  2224 , and the tips of the barbules are in isosceles triangular arrangement from top view. 
         [0036]      FIG. 7  is a top view of the microneedle set functioning as working electrode according to still another embodiment of the present invention. The first microneedle set  22  comprises a first sheet  222 , a second sheet  224 , a third sheet  226  and a fourth sheet  228  stacked with each other. The first sheet  222  has at least one first through hole  2222  defined thereon, and a first barbule  2224  at peripheral of the first through hole  2222 . The second sheet  224  has at least one second through hole  2242  defined thereon, and a second barbule  2244  at peripheral of the second through hole  2242 . The third sheet  226  has at least one third through hole  2262  defined thereon, and a third barbule  2264  at peripheral of the third through hole  2262 . The fourth sheet  228  has at least one fourth through hole  2282  defined thereon, and a fourth barbule  2284  at peripheral of the fourth through hole  2282 . The second barbule  2244 , the third barbule  2264  and the fourth barbule  228  penetrates the first through hole  2222  to juxtapose the first barbule  2224 , and the tips of the barbules are in rectangular arrangement from top view. 
         [0037]    In the embodiments shown in  FIGS. 4 to 7 , the barbule  2224  of the first microneedle set  22  comprises a tip  2221  and a base  2223 . The tips of those barbules, after the sheets are stacked together, are not at the same altitudes. Namely, some barbules pass more through holes than other barbules. Alternatively, the height of the barbules can be such designed, based on the stacked order of sheets, that the tips of those barbules, after the sheets are stacked together, are at the same altitudes. 
         [0038]      FIG. 8  shows a perspective of an assembled transdermal microneedle array patch according to an embodiment of the present invention.  FIG. 9  shows a sectional of an assembled transdermal microneedle array patch according to an embodiment of the present invention. In this shown embodiment, the first microneedle set  22  comprises a first sheet  222  and a second sheet  224  stacked with each other. The first sheet  222  and the second sheet  224  can be assembled by punching peripherals thereof. The second microneedle set  24  comprises only a first sheet  242  and the third microneedle set  26  comprises only a first sheet  262 . The transdermal microneedle array patch of the present invention uses the flexible pad  30  to have tight fit with the user&#39;s muscle during operation thereof. 
         [0039]    The first microneedle set  22  of the working electrode of the transdermal microneedle array patch according to the invention may be subjected to surface modification, in view of the target molecule to be sensed. The target molecule may be a biological molecule, such as glucose, cortisol or fatty acids. Also, the target molecule may be a pharmaceutical molecule, such as antibiotics. The transdermal microneedle array patch of the present invention may be used for pharmaceutical monitoring during the administration of a medication for a chronic disease or a specific pharmaceutical. Personalized medication of a specific dosage or frequency of administration can be provided based on the individual metabolism of the pharmaceutical. 
         [0040]    For specificity, the first microneedle set  22  may be subjected to surface modification, in view of the target molecule to be sensed. Specifically, a molecule selected from the group consisting of an antibody, an aptamer, a single-chain variable fragment (ScFv), a carbohydrate, and a combination thereof, may be coated on the surface of the microneedles. In one embodiment of the present invention, the first microneedle set  22  of the working electrode is modified with glucose oxidase (GOx) for sensing (blood) glucose. For coupling of an antibody or an aptamer, self-assembled monolayer (SAM) may be applied to the microneedle deposited with gold, before adding the antibody or the aptamer. Next, in order to ensure the specificity, a blocking molecule is applied to the position that the antibody or the aptamer fails to be coupled on SAM. To increase sensitivity, carbon nanotubes may be further mixed into the gold layer. Below the various methods for manufacturing modified electrodes are described. 
         [0041]    The method for manufacturing streptavidin-modified electrode includes steps as below. The working electrode deposited with a gold layer was treated with 200 mM of 3,3-dithiodipropionic acid for 30 min to form a self-assembled monolayer (SAM), and then washed thoroughly with distilled water. The activation of carboxylic groups were performed on the electrode after incubation with 100 mM of N-(3-dimethylaminopropyl)-N-ethylcarbodiimide (EDC) and 1 mM N-hydroxysuccinimide (NHS) for an hour. Afterward, the electrode was incubated overnight with 1 mg/ml streptavidin in PBS buffer (pH 7.5). The free carboxyl groups on the electrode were blocked by incubation with 100 mMof ethanolamine for 20 min. Finally, 10 nM of biotinylated DNA aptamer was incubated on streptavidin coated electrode for 40 min, and washed thoroughly with distilled water. 
         [0042]    Take tetracycline sensing as an example. Tetracycline is an antibiotic commonly used for treating organ inflammation of a patient. For tracing the changes in concentration of tetracycline over time in a patient&#39;s body, a transdermal microneedle array patch coupling a biotinylated ssDNA aptamer on a surface of the microneedle of streptavidin-modified electrode is suitable to measure the concentration of tetracycline, wherein the biotinylated ssDNA aptamer has specificity to tetracycline. Therefore, the transdermal microneedle array patch of the present invention may be used for pharmaceutical monitoring during the administration of a medication for a chronic disease or a specific pharmaceutical. Personalized medication of a specific dosage or frequency of administration can be provided based on the individual metabolism of the pharmaceutical. 
         [0043]    To increase sensitivity, carbon nanotubes may be further mixed into the gold layer. The method for manufacturing multiwalled carbon nanotube (MWCNT) chemically modified electrode includes steps as below. Carboxylic derivative of CNTs was obtained from commercial available MWCNTs by refluxing in 4 M HNO 3 . The thus obtained oxidized MWCNTs (20 mg) were refluxed in SOCl 2  (10 mL) for 12 h. The resulting mixture was decanted, and excess SOCl 2  was removed in vacuo. A solution of mercaptoethanol (2 mL, 30 mmol) and of triethylamine (1 mL, 7 mmol) in CH 2 Cl 2  (10 mL) was added, and the mixture was refluxed for 24 h. The suspension was centrifuged and the solid repeatedly washed with methanol to give derivatized MWCNTs. The MWCNTs-CME was prepared by dipping the cleaned gold electrode in a sonicated suspension of 3 mg of derivatized nanotubes in 1 mL of DMSO for 48 h. Finally, 10 nM of biotinylated DNA aptamer was incubated on streptavidin coated electrode for 40 min, and washed thoroughly with distilled water. 
         [0044]    The method for manufacturing single-walled carbon nanotube (SWCNT) chemically modified electrode includes steps as below. Carboxylic derivative of CNTs was obtained from commercial available SWCNTs by refluxing in 4 M HNO 3 . A cystamine monolayer was assembled on the gold electrode to form a self-assembled monolayer (SAM) and the SWCNTs (reactant 2a) that was dispersed by sonicating 3 mg of the material in 1 mL of DMF were linked to the SAM surface in the presence of the coupling reagent, 1,3-dicyclohexylcarbodiimide (DCC, 3 mg) to obtain a product 2b. Next, mercaptoethanol was coupled to the carboxyl groups at the free edges of the product 2b by using DCC (2 mM mercaptoethanol solution in 1 mL of DMF and 3 mg of DCC) to obtain SWCNT chemically modified electrode. Finally, 10 nM of biotinylated DNA aptamer was incubated on streptavidin coated electrode for 40 min, and washed thoroughly with distilled water. 
         [0045]    Next, please refer to  FIG. 10 .  FIG. 10  is a partially sectional view of  FIG. 9 , where sensing polymer is coated on the barbules. More particularly, the sensing polymer is coated on the inner faces of the barbules, and anti-irritation medicine (medicine preventing skin from irritation) is coated on outer faces of the barbules. In this embodiment, the sensing polymer is a molecule selected from the group consisting of an antibody, an aptamer, a single-chain variable fragment (ScFv), a carbohydrate, glucose oxidase (GOx), hydroxybutyrate dehydrogenase (HBHD), and a combination thereof. The transdermal microneedle array patch having barbules coated with the sensing polymer can sense the concentration data of hypodermal target molecules and determine the current physiological condition of user with the concentration data. 
         [0046]      FIG. 11  is a partially sectional view of  FIG. 9 , where sensing polymer is coated on a test strip. The embodiment shown in this figure is different with the embodiment of  FIG. 10  in that the first microneedle set  22  in this embodiment is used to withdraw interstitial fluid. Therefore, the sensing polymer is coated on a test strip below the first microneedle set  22  instead of coating on the barbules. In this embodiment, the test strip is arranged between the first microneedle set  22  and the substrate  10 . The test strip comprises a conductive layer  92  and a plurality of test areas  94  on the conductive layer  92 . The test areas  94  are coated with sensing polymer and aligned with the through holes  2222  of the first microneedle set  22 . In this embodiment, the test areas  94  are defined by the resin plate  96 . Moreover, the first microneedle set  22  is fixed to the test strip by a binding layer  98 . In order to prevent the sensing polymer and the anti-irritation medicine from environment pollution, a protection layer such as an epoxy-polyurethane (Epoxy-PU) film is formed on the surface of the sensing polymer and the anti-irritation medicine. Also, since the ammeter electrochemical method is usually less selective, common interferences may present in plasma to interfere the signal. In order to achieve high selectivity for hypodermal target molecule, a semi-permeable membrane or low oxygen permeable membrane is formed on the surface of the electrode, and then a sensing polymer is formed on the semi-permeable membrane or low oxygen permeable membrane. 
         [0047]    According to one embodiment of the present invention, a wireless transmission unit (not shown in figures) may further be electrically connected to the signal processing unit  41 , and may transmit the sensor signal received from the signal processing unit  41  to a doctor for further review and diagnosis. If the doctor considers that immediate treatment or medication is required, he or she may then send an instruction signal to the user. The wireless transmission unit  41  would receive the instruction signal and the transdermal sensor may provide a signal to remind the user to pay attention to his or her physiological status or to take medication. 
         [0048]    Next, please refer to  FIG. 12 .  FIG. 12  shows a partially sectional view of an assembled transdermal microneedles continuous monitoring system according to another embodiment of the present invention. In this embodiment, the conductive pin  2248  is bent to electrically connect the contact  42  on the circuit board  40 , thus dispensing with the conductive post. 
         [0049]    As the skilled person will appreciate, various changes and modifications can be made to the described embodiments. It is intended to include all such variations, modifications and equivalents which fall within the scope of the invention, as defined in the accompanying claims.