Hydrogel material for iontophoresis

Abstract

[Problem] To develop a method with which a medicine such as insulin can be delivered in a minimally invasive manner. [Solution] It was discovered that even types of insulin that form a multimer in aqueous solution can be delivered transdermally in a minimally invasive manner through iontophoresis by holding the insulin or modified insulin in a non-ionic hydrogel.

Description

Hydrogel materials for iontophoresis

[0001] The present invention relates to polymeric material compositions for the iontophoretic delivery of insulin or insulin variants, and to transdermal delivery devices containing such compositions.

[0002] Diabetic patients often require daily subcutaneous injections of insulin. Without subcutaneous insulin injections, blood sugar control can become poor, and in the worst case scenario, there's a risk of hyperglycemia leading to a serious condition. However, daily administration is not only time-consuming, but injecting insulin into the same area can lead to the formation of hard lumps (insulin balls) under the skin due to adipose hyperplasia, where subcutaneous fat accumulates at the injection site, and insulin-derived amyloid (a fibrous protein substance). Even if you try to rotate your injection site, induration can still occur due to factors like your dominant hand or the location of each injection being more convenient.

[0003] On the other hand, iontophoresis (IP) is a transdermal drug delivery technology that uses a weak electric current. Compared to conventional administration methods, it has advantages such as avoiding the hepatic first-pass effect and enabling non-invasive administration, making it an administration method that can improve patients' quality of life. Therefore, if insulin can be administered by IP, minimally invasive subcutaneous administration will be possible without damaging the skin. The development of a device could make it possible to automate administration, which could also improve medication adherence.

[0004] However, for certain drugs to be delivered by IP, the drug must have some degree of hydrophobicity and charge, and a molecular weight of 1x10 ４ There are limitations, such as the amount of insulin that does not exceed 1000 mg / mL. In other words, proteins and nucleic acids that are generally highly hydrophilic and have large molecular weights are difficult to deliver by IP. In fact, it is known that transdermal delivery of human insulin by IP is difficult because the insulin monomer (molecular weight: 5.8 kDa) easily forms a dimer or a hexamer (molecular weight: 36 kDa) (e.g., Non-Patent Document 1).

[0005] Kanikkannan et al., Journal of Controlled Release, Vol. 59, Issue 1, 99-105, 1999

[0006] Therefore, an object of the present invention is to develop a method for minimally invasively delivering drugs such as insulin.

[0007] As a result of extensive research aimed at solving the above-mentioned problems, the present inventors have found that by retaining insulin or insulin variants in a nonionic hydrogel, even insulin species that form multimers in aqueous solution can be delivered transdermally with minimal invasiveness by iontophoresis, leading to the present invention. Furthermore, they have found that certain insulin variants, which are known to form multimers in aqueous solution, can be efficiently delivered by iontophoresis.

[0008] That is, in one aspect, the present invention relates to a polymer material composition suitable as a drug-carrying medium in iontophoresis, and more specifically, to the following: <1> A polymer material composition for delivering insulin or an insulin variant into the body of a subject by iontophoresis, the composition comprising a nonionic hydrogel retaining insulin or an insulin variant therein; <2> The composition according to <1> above, in which the nonionic hydrogel forms a three-dimensional network structure by crosslinking a first polymer unit having two or more nucleophilic functional groups at the side chain or end with a second polymer unit having two or more electrophilic functional groups at the side chain or end; <3> The composition according to <2> above, in which the polymer unit has a polyalkylene glycol skeleton; <4> The composition according to <2> above, in which the polymer unit is a di-, tri-, tetra-, or octa-branched polyethylene glycol; <5> The nucleophilic functional group is selected from the group consisting of a thiol group and an amino group, and the electrophilic functional group is selected from the group consisting of a maleimidyl group, an N-hydroxy-succinimidyl (NHS) group, a sulfosuccinimidyl group, a phthalimidyl group, an imidazoyl group, an acryloyl group, a nitrophenyl group, and —CO ２ PhNO ２<6> The composition according to <1> above, wherein the insulin or insulin variant has a multimeric structure; <7> The composition according to <6> above, wherein the insulin or insulin variant having a multimeric structure is a dimer or hexamer; <8> The composition according to <6> or <7> above, wherein the insulin or insulin variant having a multimeric structure has a molecular weight of 10 kDa or more.

[0009] In another aspect, the present invention also relates to a device and method for transdermal delivery of a drug solution by iontophoresis, and more specifically, provides: <9> a device for transdermal delivery of a drug solution, comprising positive and negative electrodes that are electrodes for performing iontophoresis, a power supply connected to the positive and negative electrodes, and a solution holder connected to each of the positive and negative electrodes, wherein the solution holder connected to the negative electrode contains a nonionic hydrogel that holds insulin or an insulin variant therein; <10> a method for transdermal delivery of a drug solution by iontophoresis, comprising the steps of: contacting the positive and negative electrodes connected to a solution holder that contains a nonionic hydrogel that holds insulin or an insulin variant therein with the skin of a subject; and applying a voltage to the positive and negative electrodes to deliver the insulin or insulin variant into the skin; and <11> a method for performing iontophoresis using an aqueous solution of an insulin variant that forms a multimer.

[0010] The present invention uses a nonionic hydrogel as a drug-holding medium, thereby enabling minimally invasive transdermal delivery of insulin species that form multimers, which has been difficult to achieve in the past, by iontophoresis.

[0011] Figure 1 is a schematic diagram of a rat with an iontophoresis device installed. Figure 2 is a schematic diagram of iontophoresis using a solution as the negative electrode (left: comparative example) and a schematic diagram of iontophoresis using a gel as the negative electrode (right: example). Figure 3 is a graph showing the change in blood glucose level when iontophoresis was performed on regular insulin (Novolin R) in solution (comparative example). Figure 4 is a graph showing the change in blood glucose level when an insulin-containing gel was used (in the figure, ◯: insulin solution, ● and △: insulin-containing gel). Figure 5 is a graph showing the change in blood glucose level (left) and the rate of change (right) after iontophoresis using an insulin variant (insulin aspart). Figure 6 shows the change in blood glucose level in individual rats after transdermal administration of insulin aspart: gel group (left) and solution group (right). Figure 7 shows the change in blood glucose level in individual rats after transdermal administration of insulin lispro: gel group (left) and solution group (right). FIG. 8 shows the changes in blood glucose levels in individual rats after transdermal administration of insulin glulisine: gel group (left) and solution group (right).

[0012] The following describes embodiments of the present invention. The scope of the present invention is not limited to these descriptions, and other than the following examples, the present invention can be implemented with appropriate modifications within the scope that does not depart from the spirit of the present invention.

[0013] The polymeric material composition of the present invention is for delivering insulin or an insulin variant into the body of a subject by iontophoresis, and is characterized by comprising a nonionic hydrogel that retains insulin or an insulin variant therein. The nonionic hydrogel is suitable as a drug-retaining medium for iontophoresis.

[0014] "Iontophoresis" is a technique that uses a weak electric current to deliver a substance to be delivered into the body through the epidermis, which is normally difficult to pass through, by the electroosmotic force that is generated. See, for example, Kogure et al., Drug Delivery System, 36-3, 198-208, 2021.

[0015] A device system for iontophoresis typically includes positive and negative electrodes, a power supply connected to the positive and negative electrodes, and a solution reservoir connected to each of the positive and negative electrodes. Specifically, for example, two components with electrodes are attached to the skin. An anionic drug is enclosed in the negative solution reservoir, and a cationic drug is enclosed in the positive solution reservoir. The electrodes of both components are then connected, and a voltage is applied. The drug migrates into the skin, and at the same time, endogenous ions that pair with the drug are extracted from the skin into the solution reservoir. Ion exchange also occurs in the other solution reservoir, completing an electrical circuit. Furthermore, when a voltage is applied to the skin, water moves from the positive electrode to the negative electrode, allowing uncharged drugs that do not dissociate via ions to be delivered transdermally.

[0016] The polymeric material composition of the present invention can be connected below an electrode as a drug-retaining medium. Typically, the polymeric material composition is placed so as to be in close contact with the skin, and a flat electrode is placed on top of it. Since the nonionic hydrogel of the present invention retains insulin or an insulin variant inside, the polymeric material composition of the present invention is usually connected to the negative electrode (cathode). In this case, a solution such as phosphate buffer solution (PBS) is stored in the solution-retaining portion on the positive electrode (anode).

[0017] The nonionic hydrogel in the polymer material composition of the present invention is a gel formed by crosslinking hydrophilic polymers with each other. As mentioned above, since the technique of iontophoresis is a mechanism that also utilizes changes in charge, a nonionic hydrogel that does not have an electric charge is preferred. In this specification, the term "gel" generally refers to a dispersion system of polymers that has lost fluidity, and in which the storage modulus G' and the loss modulus G" satisfy the relationship G'≧G". Furthermore, the term "hydrogel" refers to a gel that contains water.

[0018] The hydrophilic polymer may be any known hydrophilic polymer in the art, provided that it can form a hydrogel through a gelation reaction (crosslinking reaction, etc.) in an aqueous solution. More specifically, the hydrophilic polymer is preferably a polymer that can form a network structure, particularly a three-dimensional network structure, by crosslinking the polymers together in the final gel. Representative examples include polymers having multiple branches of polyalkylene glycol skeletons. Additionally, polymers having a polyvinyl skeleton, such as methyl methacrylate, can also be used.

[0019] In a preferred embodiment, the nonionic hydrogel in the polymer material composition of the present invention forms a three-dimensional network structure by crosslinking a first polymer unit having two or more nucleophilic functional groups at its side chains or terminals with a second polymer unit having two or more electrophilic functional groups at its side chains or terminals. The total number of nucleophilic functional groups and electrophilic functional groups is preferably five or more. It is more preferable that these functional groups are present at the terminals.

[0020] Nucleophilic functional groups present in the first polymer unit include thiol groups (-SH) (also called sulfhydryl groups) and amino groups, and those skilled in the art can appropriately use known nucleophilic functional groups. Preferably, the nucleophilic functional group is a thiol group or an amino group. The nucleophilic functional groups may be the same or different, but are preferably the same. When the functional groups are the same, the reactivity with the electrophilic functional groups that form crosslinks becomes uniform, making it easier to obtain a hydrogel with a uniform three-dimensional structure.

[0021] The electrophilic functional group present in the second polymer unit can be a maleimidyl group (maleimide group) or an active ester group. Examples of the active ester group include an N-hydroxy-succinimidyl (NHS) group and a sulfosuccinimidyl group. Those skilled in the art can appropriately use other known electrophilic functional groups. Preferably, the electrophilic functional group is a maleimidyl group or an active ester group. The electrophilic functional groups may be the same or different, but are preferably the same. When the functional groups are the same, the reactivity with the nucleophilic functional groups that form crosslinks becomes uniform, making it easier to obtain a hydrogel with a uniform three-dimensional structure.

[0022] Although there are no particular limitations on the combination of nucleophilic functional groups and electrophilic functional groups, a combination that does not generate a leaving group during the crosslinking reaction is preferred from the viewpoint of eliminating the need for washing or purification after crosslinking. That is, between the combination of an amino group and an active ester group and the combination of a sulfhydryl group and a maleimidyl group, the latter, which does not generate a leaving group, is more preferred.

[0023] In a preferred embodiment, the first and second polymer units are polyethylene glycols (PEGs) with multiple branches, such as di-, tri-, tetra-, or octa-branched. Tetra-branched polyethylene glycols are particularly preferred. Gels composed of such a tetra-branched polyethylene glycol backbone are commonly known as Tetra-PEG gels. A mesh-like network is constructed by an AB cross-end coupling reaction between two tetra-branched polymers, each of which has an electrophilic functional group, such as an activated ester structure, and a nucleophilic functional group, such as an amino group, at its terminal (Matsunaga et al., Macromolecules, Vol. 42, No. 4, pp. 1344-1351, 2009). Furthermore, Tetra-PEG gels can be easily prepared in situ by simply mixing two polymer solutions. Using Tetra-PEG technology, it is also possible to control the gelation time by adjusting the pH and ionic strength during hydrogel preparation. Because the resulting hydrogels are primarily composed of PEG, they also have excellent biocompatibility. Compounds A and B can be selected from the branched polyethylene glycol group depending on the intended use, shape, etc. of the final hydrogel.

[0024] In addition to the above-mentioned combinations of nucleophilic functional groups and electrophilic functional groups, covalent bond-forming reactions known to those skilled in the art, such as cycloaddition reactions between azides and alkynes and other reactions known as click chemistry, can also be used as appropriate.

[0025] The molecular weight of PEG used as the first and second polymer units is typically 4×10 ４ The weight average molecular weight of the copolymer may be less than 5×10. 3 ~4×10 ４ , more preferably 1×10 ４ ~4×10 ４ , and more preferably 1×10 ４ ~2×10 ４ In a preferred embodiment, the first polymer unit and / or the second polymer unit may be 4×10 ４ It has the following weight average molecular weight:

[0026] Non-limiting examples of preferred PEG having a nucleophilic functional group at its terminal include a compound represented by the following formula (I) having four branches of a polyethylene glycol backbone and a thiol group at its terminal.

[0027] n １１ ~n １４ may be the same or different. １１ ~n １４ The closer the values ​​of n are, the more uniform the three-dimensional structure can be, resulting in higher strength. Therefore, in order to obtain a high-strength hydrogel, it is preferable that n be the same. １１ ~n １４ If the value of is too high, the strength of the gel will be weak, and １１ ~n １４ If the value of n is too low, the gel is difficult to form due to the steric hindrance of the compound. １１ ~n １４ is an integer value of 28 to 227, preferably 56 to 227, and more preferably 56 to 114.

[0028] In the above formula (I), R １１ ~R １４ is a linker moiety connecting the functional group and the core moiety. １１ ~R １４ may be the same or different, but are preferably the same in order to produce a high-strength hydrogel having a uniform three-dimensional structure. １１ ~R １４ is C １ -C ７ Alkylene group, C ２ -C ７ Alkenylene group, —NH—R １５ -, -CO-R １５ -, -R １６ -O-R １７ -, -R １６ -NH-R １７ -, -R １６ -CO ２ -R １７ -, -R １６ -CO ２ -NH-R １７ -, -R １６ -CO-R １７ -, R１６ -NH-CO-R １７ -or-R １６ —CO—NH—R １７ - where R １５ is C １ -C ７ represents an alkylene group. １６ is C １ -C ３ represents an alkylene group. １７ is C １ -C ５ represents an alkylene group.

[0029] Here, "C １ -C ７ The term "alkylene group" means an alkylene group having 1 to 7 carbon atoms, which may be branched, and is a straight-chain C １ -C ７ Alkylene group or C having one or more branches ２ -C ７ It means an alkylene group (having 2 to 7 carbon atoms including branches). １ -C ７ Examples of the alkylene group include a methylene group, an ethylene group, a propylene group, and a butylene group. １ -C ７ Examples of the alkylene group are -CH2-, -(CH2)2-, -(CH2)3-, -CH(CH3)-, -(CH2)3-, -(CH(CH3))2-, -(CH2)2-CH(CH3)-, -(CH2)3-CH(CH3)-, -(CH2)2-CH(C2H5)-, -(CH2)6-, -(CH ２ )2-C(C2H5)2-, and -(CH2)3C(CH3)2CH2-.

[0030] "C ２ -C ７ The term "alkenylene group" refers to a branched or straight-chain alkenylene group having 2 to 7 carbon atoms and having one or more double bonds in the chain, and examples thereof include divalent groups having double bonds formed by removing 2 to 5 hydrogen atoms from adjacent carbon atoms of the alkylene group.

[0031] On the other hand, non-limiting specific examples of preferred PEGs having an electrophilic functional group at their termini include compounds represented by the following formula (II), which have four branches of a polyethylene glycol backbone and a maleimidyl group at their termini:

[0032] In the above formula (II), n ２１ ~n ２４ may be the same or different. ２１ ~n ２４ The closer the values ​​of n are, the more uniform the three-dimensional structure of the hydrogel will be, and the higher the strength will be, so it is preferable, and it is more preferable that they are the same. ２１ ~n ２４ If the value of is too high, the strength of the gel will be weak, and ２１ ~n ２４ If the value of n is too low, the gel is difficult to form due to the steric hindrance of the compound. ２１ ~n ２４ is an integer value of 11 to 569, preferably 28 to 227, and more preferably 56 to 114.

[0033] In the above formula (II), R ２１ ~R ２４ is a linker moiety connecting the functional group and the core moiety. ２１ ~R ２４ may be the same or different, but are preferably the same in order to produce a high-strength gel having a uniform three-dimensional structure. ２１ ~R ２４ are the same or different, and C １ -C ７ Alkylene group, C ２ -C ７ Alkenylene group, —NH—R ２５ -, -CO-R ２５ -, -R ２６ -O-R ２７ -, -R ２６ -NH-R ２７ -, -R ２６ -CO ２ -R ２７ -, -R ２６ -CO ２ -NH-R ２７ -, -R ２６ -CO-R２７ -, -R ２６ -NH-CO-R ２７ - or -R ２６ —CO—NH—R ２７ - where R ２５ is C １ -C ７ represents an alkylene group. ２６ is C １ -C ３ represents an alkylene group. ２７ is C １ -C ５ represents an alkylene group.

[0034] In this specification, alkylene groups and alkenylene groups may have one or more optional substituents. Examples of the substituents include, but are not limited to, alkoxy groups, halogen atoms (which may be fluorine, chlorine, bromine, or iodine atoms), amino groups, mono- or di-substituted amino groups, substituted silyl groups, acyl groups, and aryl groups. When an alkyl group has two or more substituents, they may be the same or different. The same applies to the alkyl moieties of other substituents containing an alkyl moiety (e.g., alkyloxy groups, aralkyl groups, etc.).

[0035] Furthermore, in this specification, when a functional group is defined as "optionally having a substituent," the type of the substituent, the substitution position, and the number of the substituent are not particularly limited, and when two or more substituents are present, they may be the same or different. Examples of the substituent include, but are not limited to, an alkyl group, an alkoxy group, a hydroxyl group, a carboxyl group, a halogen atom, a sulfo group, an amino group, an alkoxycarbonyl group, and an oxo group. These substituents may further have a substituent.

[0036] The nonionic hydrogel used in the present invention may be used as it is in a water-containing state after gel formation, or may be dried after gel formation and then added with insulin or the like.

[0037] The drug retained inside the nonionic hydrogel is insulin or a modified insulin. For example, it can be human insulin or a modified form (insulin analog) in which the amino acid sequence of human insulin has been partially altered by genetic recombination. Examples of such modified forms include insulin aspart (monomer Mw: 5825.44), in which proline at position 28 of the B chain of human insulin is replaced with aspartic acid, and insulin lispro (monomer Mw: 5807.57), in which proline at position 28 of the B chain of human insulin is replaced with lysine at position 29.

[0038] It is known that human insulin forms hexamers in formulations, and even after subcutaneous injection, a mixture of hexamers, dimers, and monomers is present. When human insulin forms multimers, its molecular weight increases, making it impossible to deliver by conventional iontophoresis. On the other hand, modified insulins, while designed to dissociate into monomers after subcutaneous injection, remain in hexamer form in formulations, and delivery by iontophoresis has also been considered difficult. An analogue modified to remain in a monomeric form in formulations is insulin glulisine (monomer Mw: 5822.58), in which asparagine at position 3 of the human insulin B chain is replaced with lysine and lysine at position 29 is replaced with glutamic acid. However, its delivery by iontophoresis has not yet been demonstrated.

[0039] Preferably, the insulin or insulin variant retained within the nonionic hydrogel has a multimeric structure in aqueous solution, more preferably a dimeric or hexameric structure. Furthermore, preferably, the multimeric insulin or insulin variant has a molecular weight of 10 kDa or more, or 35 kDa or more. The present invention demonstrates that these multimeric insulin species can be delivered transdermally by iontophoresis in a minimally invasive manner by retaining them within a nonionic hydrogel.

[0040] The concentration of insulin or modified insulin in the nonionic hydrogel is preferably close to 10 to 100 units / mL. For example, for normal human insulin, the range is preferably 48.7 to 731 μM, more preferably 487 to 731 μM, which includes the value corresponding to 100 units / mL typically used in insulin preparations, and most preferably 609 μM. The molar concentrations of other insulin analogs can be calculated using the "units" that represent the biological potency of insulin to obtain the values ​​above.

[0041] In another aspect, the present invention relates to a device for transdermal delivery of a drug solution by iontophoresis, characterized in that the device comprises positive and negative electrodes for performing iontophoresis, a power supply unit connected to the positive and negative electrodes, and a solution holding unit connected to each of the positive and negative electrodes, wherein the solution holding unit connected to the negative electrode contains a nonionic hydrogel holding insulin or an insulin variant therein.

[0042] Here, the specific configurations of the power supply unit, positive electrode, and negative electrode in the device may be those known in the art, but preferably the positive electrode and negative electrode are flat plate electrodes.

[0043] From another perspective, the present invention can also be said to relate to a method for performing iontophoresis using such a device. More specifically, the method of the present invention is a method for transdermal delivery of a drug solution by iontophoresis, characterized by comprising: A) a step of contacting a positive electrode and a negative electrode connected to a solution holding section containing a nonionic hydrogel holding insulin or an insulin variant therein with the skin of a subject; and B) a step of applying a voltage to the positive electrode and the negative electrode to deliver the insulin or insulin variant into the skin.

[0044] Furthermore, as demonstrated in the Examples below, the inventors have now surprisingly discovered that certain insulin variants, which were previously thought to be unsuitable for iontophoresis because they form multimers in solution, can be delivered to a certain extent without the use of a nonionic hydrogel as a vehicle. Therefore, in yet another aspect, the present invention also relates to a method for iontophoresis using an aqueous solution of a multimer-forming insulin variant. Such variants are preferably insulin aspart (monomer Mw: 5825.44), in which proline at position 28 of the human insulin B chain is substituted with aspartic acid, or insulin lispro (monomer Mw: 5807.57), in which proline at position 28 and lysine at position 29 of the human insulin B chain are substituted, as described above.

[0045] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples.

[0046] Materials: Citrate-phosphate buffer (CPB) was prepared as a buffer for the polymer solution in each experiment. CPB can be prepared by a commonly reported method. Here, it was adjusted to pH 5.0 according to the report by McIlvaine et al. (J. Biol. Chem. 49(1):183-186.). The resulting buffer was defined as 200 mM CPB (pH 5.0) and further diluted with water for injection (Hikari Pharmaceutical Co., Ltd.) to a concentration of 150 mM. Finally, 150 mM CPB (pH 5.0) was obtained. SINOPEG's 4-arm PEG-SH (PEG-SH, molecular weight 20,000), a four-branched PEG with terminal sulfhydryl groups (-SH), was dissolved in 150 mM CPB (pH 5.0) to a concentration of 20 g / L, and this solution was defined as Solution S. 4-arm PEG-MAL (PEG-MAL, molecular weight 20,000), a 4-branched PEG having a maleimide group (-MAL) at its terminal, manufactured by SINOPEG, was dissolved in 150 mM CPB (pH 5.0) to a concentration of 20 g / L, and this solution was defined as solution M.

[0047] Preparation of Gels: Solution S and solution M were mixed at a volume ratio of 1:1, and 200 μL was immediately added to a Parafilm sheet. A circular cover glass (0.15 mm thick, φ15 mm) was placed on top of the added solution and allowed to stand overnight at room temperature in a humidified, sealed container. The next day, gelation was visually confirmed. The gel was then immersed in a sufficient amount of D-PBS(-) (Fujifilm Wako Pure Chemical Industries) and stored in a refrigerator, changing the solution at least three times over the course of a day. Furthermore, the D-PBS(-) was replaced with ultrapure water in a separate ointment container (a total of four times), and the gel was cut to the required size and air-dried at room temperature starting the day before testing. On the day of testing, various insulin solutions were added dropwise to the air-dried gel to swell it. This gel was used as a gel containing regular insulin or an insulin analog (modified form).

[0048] Preparation of Diabetic Rats: Wistar male rats were purchased at 7 weeks of age (160-170 g) and were used at 8 weeks of age after one week of pre-breeding. Two days before the percutaneous experiment, they were fasted overnight (water was available ad libitum). The following morning, streptozotocin (STZ), which specifically destroys the beta cells of the pancreatic islets of Langerhans, was administered intraperitoneally (ip) (dosage: 50 mg (1 mL saline) / kg = 5 mg (0.1 mL saline) / 100 g). Because STZ decomposes quickly, it was prepared immediately before use (50 mg / mL saline). After STZ administration, rats were allowed to eat ad libitum. The following day, the rats were used in the percutaneous absorption experiment.

[0049] Transdermal Absorption Experiment (Iontophoresis Test) An iontophoresis test was carried out according to the following procedure: A schematic diagram of a rat in which an iontophoresis device was placed is shown in Figure 1. The configuration of the iontophoresis device is shown in Figure 2.

[0050] (1) Under temporary isoflurane inhalation anesthesia, pentobarbital was administered intraperitoneally (5 mg / 0.1 mL / 200 g) to induce general anesthesia. (2) The abdominal area was carefully depilated with electric clippers and an electric shaver. A polyethylene tube was cannulated into the left femoral artery for serial blood sampling. The surgical site was locally anesthetized with lidocaine spray. (3) The top of a glass Franz-type diffusion cell was attached to the abdomen with Araldite and left to stand for at least one hour. (4) Using a cotton swab, the skin inside the glass cell was thoroughly moistened with ultrapure water. (5) A gel containing regular insulin (trade name "Novolin R") or an insulin analog (modified) was placed on the skin inside the glass cell on the head side, and a flat electrode with a metal rod was placed on top. The rubber stopper was used to adjust the gel to fit snugly against the skin. 1 mL of PBS was added to the glass cell on the tail side. Iontophoresis was then performed using the insulin analog as the negative electrode. A group was also set up in which insulin analog solution was used instead of the insulin analog-containing gel. Iontophoresis conditions: A BEX Precision Constant-Current Model BP-1000M (continuous constant current / constant voltage) was used, and iontophoresis was performed at a continuous direct current of 0.27 mA. Silver-silver chloride (Ag-AgCl) electrodes were used, with the insulin analog side serving as the cathode (AgCl) and the PBS side serving as the anode (Ag). (6) Blood samples were collected over time from the cannula, and blood glucose levels were measured using a Precision Exceed blood glucose meter. Iontophoresis was performed for 3 hours, after which the glass cell and gel were removed.

[0051] 1) Results for Regular Insulin Iontophoresis was performed using a gel containing regular insulin (Novolin R) on the negative electrode. As a comparative example, iontophoresis was similarly performed using an insulin (Novolin R) solution on the negative electrode side without using a gel. The results are shown in Figures 3 and 4.

[0052] As a result, when regular insulin (Novolin R) was used in solution for iontophoresis, blood glucose levels did not decrease (Figure 3; and circles in Figure 4). This is thought to be because insulin exists as a hexamer, and its molecular size prevents delivery. In contrast, blood glucose levels decreased in the group that also used insulin-containing gel (● and △ in Figure 4). This is thought to be because insulin temporarily became a monomer during electrophoresis in the gel and was then delivered to the blood.

[0053] 2) Results for modified insulin (analog) Figure 5 shows the results of iontophoresis using modified insulin (analog) instead of regular insulin.

[0054] The graph shows the change in blood glucose levels and the rate of change after IP administration of 0.27 mA of insulin aspart. The experimental groups were a group in which blood glucose levels were measured without any administration (△), an insulin analog-encapsulated gel group (●), and an insulin analog solution group (◯) (n=1 for each group). While blood glucose levels remained high in the group without any administration, blood glucose levels decreased in the two insulin-administered groups. This is thought to be the result of insulin being delivered transdermally via IP. Similar results were obtained between the two insulin-administered groups. In other words, insulin can be administered either in solution or impregnated in a gel.

[0055] The changes in blood glucose levels for individual animals for insulin aspart, insulin lispro, and insulin glulisine are shown for the insulin analog-encapsulated gel group and the insulin analog solution group (Figures 6 to 8). Figure 6 shows the changes in blood glucose levels for individual rats after transdermal administration of insulin aspart; the gel group (left) and the solution group (right). Figure 7 shows the changes in blood glucose levels for individual rats after transdermal administration of insulin lispro; the gel group (left) and the solution group (right). Figure 8 shows the changes in blood glucose levels for individual rats after transdermal administration of insulin glulisine; the gel group (left) and the solution group (right).

[0056] As a result, iontophoresis reduced blood glucose levels in all insulin analog encapsulated gel groups, and the effect was equivalent to that of the insulin solution group.

Claims

1. A polymeric material composition for iontophoretic delivery of insulin or modified insulin into the body of a subject, comprising a nonionic hydrogel having insulin or modified insulin retained therein.

2. The composition of claim 1, wherein the nonionic hydrogel forms a three-dimensional network structure by cross-linking a first polymer unit having two or more nucleophilic functional groups on the side chain or at the end with a second polymer unit having two or more electrophilic functional groups on the side chain or at the end.

3. The composition according to claim 2, wherein the polymer unit has a polyalkylene glycol backbone.

4. The composition of claim 2, wherein the polymer unit is a di-, tri-, tetra-, or octa-branched polyethylene glycol.

5. The nucleophilic functional group is selected from the group consisting of a thiol group and an amino group, and the electrophilic functional group is selected from the group consisting of a maleimidyl group, an N-hydroxy-succinimidyl (NHS) group, a sulfosuccinimidyl group, a phthalimidyl group, an imidazoyl group, an acryloyl group, a nitrophenyl group, and a -CO ２ PhNO ２ 3. The composition of claim 2 selected from the group consisting of:

6. The composition according to claim 1, wherein the insulin or modified insulin has a multimeric structure.

7. The composition according to claim 6, wherein the insulin or insulin variant having a multimeric structure is a dimer or hexamer.

8. The composition according to claim 6 or 7, wherein the insulin or modified insulin having a multimeric structure has a molecular weight of 10 kDa or more.

9. A device for transdermal delivery of a drug solution, comprising positive and negative electrodes for performing iontophoresis, a power supply connected to the positive and negative electrodes, and a solution holding portion connected to each of the positive and negative electrodes, wherein the solution holding portion connected to the negative electrode contains a nonionic hydrogel holding insulin or an insulin variant therein.

10. A method for transdermal delivery of a drug solution by iontophoresis, comprising the steps of: contacting a positive electrode and a negative electrode connected to a solution holding section containing a nonionic hydrogel holding insulin or an insulin variant therein with the skin of a subject; and applying a voltage to the positive electrode and the negative electrode to deliver the insulin or insulin variant into the skin.

11. A method of performing iontophoresis using an aqueous solution of a modified insulin that forms a multimer.

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