Microneedle for drug delivery to posterior segment of eye and use thereof

Abstract

The present invention relates to a microneedle for drug delivery to a posterior segment of the eye and a use thereof. The microneedle for drug delivery to a posterior segment of the eye of the present invention has the advantage of delivering a drug to the eye in a minimally invasive and efficient manner through an expansion mechanism by being inserted into the posterior segment of the eye. Therefore, the microneedle for drug delivery to a posterior segment of the eye of the present invention can be used in various ways to treat ocular complications by preventing backflow due to intraocular drug delivery, which is an existing limitation.

Description

Microneedles for drug delivery to the posterior ocular region and uses thereof

[0001] The present invention relates to a microneedle for drug delivery to the posterior ocular region and its use.

[0002] The present invention was carried out with support from the research project "Development of a Dual-Action TOP-V122 Drug-Loaded Swellable Microneedle Delivery System for the Treatment of Diabetic Retinopathy" of the Global Research Cooperation Support Program supported by the Ministry of Health and Welfare (Project No.: 00266598 (RS-2023-00266598), Performing Organization: Yonsei University Industry-Academic Cooperation Foundation, Research Period: 2024.01.01 ~ 2024.12.31).

[0003] This invention was carried out with support from the research project "[Seoul RISE Project / Lead] 2-5. Expansion of BIO Cluster Innovation Ecosystem" of the Seoul Metropolitan Government's Regional Innovation Center University Support System (RISE), supported by the Ministry of Education (Project No.: 2025-RISE-01-022-05, Implementing Agency: Yonsei University (RISE-Y Project Group), Research Period: 2025.06.01 ~ 2026.02.28).

[0004] The increased life expectancy and lifestyle of modern people are major factors contributing to the rise in chronic diseases, as well as causing ocular complications in the posterior segment of the eye (PSE). These complications induce abnormal growth or degeneration of retinal blood vessels, which in turn leads to the degeneration of retinal pigment epithelial cells, potentially causing vision impairment or loss and even pain due to elevated intraocular pressure. Intravitreal drug injection has been used to treat this condition by allowing drugs administered into the vitreous cavity to diffuse through the vitreous fluid to reach the posterior segment of the eye. However, this treatment method is invasive and causes serious complications such as endophthalmitis, resulting in pain and temporary visual impairment. Furthermore, it presents problems such as reduced efficacy due to the rapid elimination and random diffusion of the administered dose.

[0005] The suprachoroidal space (SCS), the space between the sclera and the choroid, is a promising pathway for targeting the posterior ocular region as it can overcome the aforementioned problems. The suprachoroidal space can be created by injecting fluid solutions into the sclera using a catheter or needle, or by creating a gap between the sclera and the choroid through invasive procedures. Since the suprachoroidal space is located across the anterior region of the eye, injecting drugs into it allows them to diffuse circumferentially toward the posterior ocular region, thereby enhancing pharmacokinetic efficiency. Despite these advantages, existing methods for accessing the suprachoroidal space remain invasive, and limitations exist due to the operator's proficiency, as the approach to accessing the space is not easy; however, these limitations can be addressed through novel drug delivery systems.

[0006] Microneedles (MNs) are micrometer-sized needles studied as drug delivery systems (DDS) due to their advantages, such as minimally invasive characteristics, ease of application, and delivery efficiency. Hollow microneedles (HMNs), made of stainless steel, gold, or glass, have been applied to the hyperchoroidal space due to the hollows within the microneedles designed for drug administration. A successful example of applying hollow microneedles to the hyperchoroidal space is the current hollow microneedle-based ocular drug delivery system, the SCS Microinjector® (Clearside Biomedical Inc.). However, hollow microneedles inevitably suppress backflow due to their narrow channel size, and consistent drug delivery cannot be guaranteed as blockages occur within the hollow microneedles. Furthermore, there are issues regarding the complex manufacturing process and the generation of medical waste due to the use of biocompatible materials.

[0007] Hydrogel-forming microneedles (HFMNs) can provide an alternative solution to the aforementioned problems. Hydrogel-forming microneedles are biocompatible and robust polymer microneedles that expand upon absorbing fluid, releasing drugs from the polymer matrix. Researchers have applied these to ocular drug delivery based on the sustained-release characteristics of hydrogel-forming microneedles, which prevent repeated injections into the eye and reduce invasiveness. Previous reports have covered implantable hydrogel-forming microneedles that rapidly release hydrogel-formulated drugs into the vitreous humor for sustained release, as well as self-adhesive hydrogel-forming microneedles that target the vitreous humor for continuous ocular drug delivery. However, while the previously reported methods target the posterior ocular region for sustained drug delivery to the vitreous humor, these approaches have not yet resolved the issue of drug diffusion. Furthermore, existing conical or pyramidal hydrogel-forming microneedles expand vertically in a relatively uncontrolled manner, making it difficult to specifically and efficiently target, localize, and deliver drugs into the hyperchoroidal space. Since mechanical stimulation at a precise depth is required to induce the formation of the hyperchoroidal space, a new microneedle capable of addressing this issue is needed.

[0008] Accordingly, the inventors, noting that the hyperchoroidal space is a pathway for effectively delivering drugs to the posterior portion of the eye, have completed a safer and more efficient drug delivery system capable of applying hydrogel microneedles to the hyperchoroidal space.

[0009] [Prior Art Literature]

[0010] [Patent Document] (Patent Document 1) Korean Patent Publication No. 10-2021-0032571 (March 24, 2021)

[0011] The object of the present invention is to provide a microneedle for drug delivery to the posterior ocular region comprising a hydrogel.

[0012] Another objective of the present invention is to provide a drug delivery device for the posterior ocular region comprising the above-mentioned drug delivery microneedles.

[0013] Another objective of the present invention is to provide a drug delivery method comprising the step of mounting the drug delivery microneedle on the posterior portion of the eye.

[0014] In the present invention, a hydrogel-forming microneedle (SCS-inducing hydrogel-forming microneedle, SI-HFMN) that induces a candle-shaped biocompatible hyperchoroidal space was prepared. The microneedle of the present invention expands to separate the sclera and the choroid, and the hyperchoroidal space induced thereby provides a drug delivery pathway to the posterior ocular region.

[0015] The present invention will be described in detail below.

[0016]

[0017] The present invention provides a microneedle for drug delivery to the posterior ocular region comprising a hydrogel.

[0018] In the present invention, the microneedles may create a hyperchoroidal space. The hyperchoroidal space, which is the space between the sclera and the choroid, provides a drug delivery pathway to the posterior ocular region. Meanwhile, the prior art had a problem of drug backflow due to the narrow channel size of hollow microneedles.

[0019] In the present invention, the microneedles may expand to separate the sclera and the choroid.

[0020] In the present invention, the microneedles may be candle-shaped. According to one embodiment of the present invention, the microneedles are fabricated in a candle shape and attached to the sclera, and can efficiently separate the sclera and the choroid through the wide diameter of the upper portion.

[0021] In the present invention, the microneedle is composed of a head portion and a base portion, and the head portion may expand to separate the sclera and the choroid. According to one embodiment of the present invention, the microneedle is fabricated in a candle shape, and the head portion, which is the thickest part, reaches a depth where a superchoroidal space can be induced, and the head portion expands to separate the sclera and the choroid and releases a loaded drug while providing maximum mechanical stimulation to induce the formation of a superchoroidal space.

[0022] In the present invention, the hydrogel may be a cross-linked polymethylvinyl ether-alt-maleic acid (PMVE / MA) and polyethylene glycol (PEG). Preferably, the hydrogel may contain 15 to 25% (w / w) polymethylvinyl ether-alt-maleic acid (PMVE / MA) and 5 to 10% (w / w) polyethylene glycol (PEG). More preferably, the hydrogel may contain 20% (w / w) polymethylvinyl ether-alt-maleic acid (PMVE / MA) and 7.5% (w / w) polyethylene glycol (PEG).

[0023] In the present invention, the microneedles may have a mechanical strength of 1.0 to 10.0 N. Preferably, the microneedles may have a mechanical strength of 3.0 to 7.0 N. More preferably, the microneedles may have a mechanical strength of 4.4 to 5.8 N. According to one embodiment of the present invention, the microneedles have a mechanical strength of 4.4 to 5.8 N and mechanically stimulate the formation of a superchoroidal space so that the microneedles penetrate the sclera and expand inside the eyeball, thereby securing sufficient mechanical strength for scleral insertion.

[0024] In the present invention, the microneedles may have an expansion rate of 100 to 500%. Preferably, the microneedles may have an expansion rate of 300 to 400%. More preferably, the microneedles may have an expansion rate of 328 to 384%.

[0025] In the present invention, the microneedles may prevent backflow after drug delivery.

[0026] In the present invention, the drug may be one or more selected from the group consisting of hydrophilic drugs, hydrophobic drugs, and mixtures thereof.

[0027] In the present invention, the microneedles may be for the treatment of ophthalmic diseases. The ophthalmic disease may be accompanied by eye pain or reduced vision.

[0028] In addition, the present invention provides a drug delivery device for the posterior ocular region comprising the above-mentioned drug delivery microneedles.

[0029] In addition, the present invention provides a drug delivery method comprising the step of mounting the drug delivery microneedle on the posterior surface of the eye.

[0030] The drug delivery microneedles of the present invention have the advantage of delivering drugs to the hyperchoroidal space of the posterior ocular region in a minimally invasive and efficient manner through an expansion mechanism. Therefore, the drug delivery microneedles of the present invention for the posterior ocular region can be utilized in various ways for the treatment of ocular complications by preventing reflux associated with intraocular drug delivery, which is a limitation of existing microneedles.

[0031] Figures 1a and 1b illustrate the design process of a hydrogel-forming microneedle (SI-HFMN) that induces a hyperchoroidal space for delivery to the posterior ocular region. Figure 1a provides a schematic description of the mechanism of the SI-HFMN. When inserted into the eye of a patient with posterior segment eye diseases (PSED), the SI-HFMN absorbs surrounding fluid and expands to induce the formation of a hyperchoroidal space, thereby creating an access pathway to the posterior ocular region and simultaneously releasing a drug loaded within the matrix of the hydrogel. The released drug then diffuses through the hyperchoroidal space to target the posterior ocular region. Figure 1b shows the morphology of various microneedles immediately after insertion (top) and the theoretical volume distribution after expansion (bottom). The conical microneedle (left), candle-shaped microneedle (middle), and funnel-shaped microneedle (right) were designed to have a height of 900 μm and a height of 1050 μm after expansion. The blue area between the dotted lines represents the sclera width.

[0032] Figures 2a to 2d illustrate the fabrication process and analysis results of the SI-HFMN array. Figure 2a illustrates the proposed mechanism for the esterification of PMVE / MA and PEG. PMVE / MA and PEG are heat-treated, leading to a condensation reaction between the carboxylic acid groups of PMVE / MA (blue box) and the hydroxyl groups of PEG (red box), forming ester bonds. Figure 2b is a schematic overview of the formation of PM-SH, a PMVE / MA-based SI-HFMN, through a micromolding process. Figure 2c is a microscopic image (scale bar: 1 mm) of the fabricated PMVE / MA 15%-based SI-HFMN PM15-SH (top), PMVE / MA 20%-based SI-HFMN PM20-SH (middle), and PMNA-SH (bottom), a modified group composed of PMVE / MA. Figure 2d shows the results of SI-HFMN array analysis according to ATR-FTIR for PMVE / MA powder (black), PM15-SH (blue), PM20-SH (red), and PMNA-SH (green), showing CO in all PM-SH groups ester This increased, confirming that the bridging was successful.

[0033] Figures 3a through 3e illustrate the fabrication process of a candle cavity containing a PDMS mold. Figure 3a is a schematic overview of the fabrication process of a candle-shaped master mold. The fabrication process is divided into two stages; the first stage involves the formation of an initial base layer using g-force, followed by the creation of a master mold through centrifugal molding. Figure 3b shows the entire 3 x 1 array, and Figure 3c shows a bright-field microscope image of a single microneedle (scale bar: 1 mm). Figure 3d shows the geometric specifications of each microneedle (n = 9, mean ± SEM). Figure 3e illustrates the process of forming a PDMS mold in a pre-compound solution and a prepared master mold.

[0034] Figures 4a through 4c illustrate the evaluation of the physical properties of each SI-HFMN formulation. Figure 4a shows a schematic diagram of the fracture force analysis using a force analyzer. The force-sensing probe moves vertically to reach the tip of the SI-HFMN and eventually fractures. The fracture force is recorded in the connected software. Figure 4b shows the average fracture force per formulation. The black dashed line indicates the minimum force (2.07 N) required to penetrate the sclera. All data are expressed as mean ± SEM (n = 10). *, P < 0.05; **, P < 0.01, ns indicates insignificance. Figure 4c is a microscopic image (scale bar: 1 mm) of SI-HFMN applied to a PDMS-based sclera-mimicking model.

[0035] Figures 5a to 5c show the analysis of SI-HFMN expansion kinetics in PBS. Figure 5a shows S% versus t (n = 6, mean ± SEM) for PM15-SH (red) and PM20-SH (blue) at each time point for up to 180 minutes. Figure 5b shows the t / S versus t curves for each PM-SH formulation, where the best-fit line was derived via linear regression. Figure 5c shows SEM images of each formulation before and after expansion (black scale bar: 100 μm). The red box represents a magnified view of the backing film surface before expansion, and the black dashed line represents a magnified view of the backing film after expansion (white scale bar: 10 μm).

[0036] Figures 6a through 6d represent further analysis of the SI-HFMN expansion behavior. Figure 6a is a bar graph of S% versus t at each time point for each formulation (n = 6, mean ± SEM). Here, **** indicates P < 0.0001; ns indicates insignificance. Figure 6b is a microscopic image (scale bar: 500 μm) of each SI-HFMN formulation at a predetermined time point. Figure 6c is the complete process of calculating SI-HFMN volume per time point. (i) SI-HFMN was imaged at each time point, and then (ii) converted to a Cartesian coordinate system to calculate the volume using the integration of the inductive function. Figure 6d shows the volume increase (V%) per time point for each SI-HFMN formulation (n = 8, mean ± SEM). *, P < 0.05. ns indicates insignificance.

[0037] Figure 7 shows the drug release analysis within the hydrogel matrix of each SI-HFMN formulation. (A) Graph of the cumulative release rate of Li-HCl up to 1440 min. (B) Results of the analysis of release kinetic parameters of the SI-HFMN array. All data are expressed as mean ± SEM (n = 5). *, P < 0.05.

[0038] Figures 8a and 8b illustrate the evaluation of the swelling effect of SI-HFMN in an in vitro tissue model. Figure 8a shows bright-field and fluorescence microscopy images of PM15-SH (top) and PM20-SH (bottom) applied to an agarose gel at predetermined time points. White arrows indicate the direction of SI-HFMN application. The black dashed line shows the application surface of the agarose gel. The white dashed line helps visualize the SI-HFMN loaded with Rho B. The yellow dashed line indicates the fracture zone of the agarose gel induced by the swelling of SI-HFMN (scale bar: 500 μm). Figure 8b shows the relative fluorescence intensity units (RFU) of the agarose gel for each formulation at 30 min (black), 60 min (gray), and upon removal of SI-HFMN (white). Data are expressed as mean ± SEM (n = 4). *; P < 0.05, ns indicates insignificance.

[0039] Figures 9a through 9d illustrate the evaluation of hyperchoroidal space formation and SI-HFMN drug delivery in Exvivo porcine eyes. Figure 9a shows real-time imaging of SI-HFMN application in Exvivo porcine eyes. (i), (iv) brightfield images following the application of PM15-SH and PM20-SH to porcine eyes (scale bar: 1 mm). (ii), (v) OCT images of SI-HFMN application at 0 min, and (iii), (vi) at 60 min. Figure 9b is a schematic overview of the analysis process for hyperchoroidal space drug delivery in Exvivo porcine eyes. After applying the Nile Red-equipped microneedle array, the application area was imaged in top and transverse views. Figure 9c shows brightfield and fluorescence images of the top view of the Nile Red-equipped microneedle application area (scale bar: 1 mm). The white dashed circle indicates successful insertion of the microneedles into the Exvivo porcine eye. Figure 9d shows brightfield (top) and fluorescence (bottom) views illustrating the delivery of the drug through the posterior ocular region into the induced hyperchoroidal space. The yellow box shows an enlarged view of the SI-HFMN application area. The white box shows an enlarged view of the posterior ocular region.

[0040] Hereinafter, the present invention will be described in detail with reference to examples to aid in understanding. However, the following examples are merely illustrative of the content of the present invention and the scope of the present invention is not limited to the following examples. The examples of the present invention are provided to more completely explain the present invention to those with average knowledge in the art.

[0041]

[0042] Example 1. Fabrication of hydrogel-forming microneedles in the present invention

[0043] Polydimethylsiloxane (PDMS) Mold Production

[0044] Hyaluronic acid (HA, 32 kDa, Bloomage Freda Biopharm, Jinan, China) was homogenized with deionized water (DW) to prepare 20% (w / v) and 60% (w / v) solutions using a paste mixer (PDM-300, KMtech, Gyeonggi, South Korea) at 1500 rpm for 45 minutes. To fabricate the base layer, the 20% (w / v) HA solution was dispensed onto a plasma-treated metal plate via a dispenser (SHOTmini 100S, Musashi Engineering, Tokyo, Japan). The metal plate was inverted onto a 300 μm high frame, and the HA droplets self-formed into an hourglass shape using g-force. After 3 hours, the metal plate was inverted to form the base layer, and the 60% (w / v) HA solution was dispensed onto the formed base layer. The droplets were formed into candlelit microneedles via centrifugal molding to create the final master mold. The diameter and height of the master mold were measured using a bright-field microscope (M165FC, Leica, Wetzlar, Germany). To fabricate a candle-shaped cavity containing the PDMS mold, a pre-compound solution was prepared by mixing Sylgard 184A (prepolymer, Sigma-Aldrich, St. Louis, MO, USA) and Sylgard 184B (curing agent, Sigma-Aldrich, St. Louis, MO, USA) in a weight ratio of 10:1. This solution was poured onto the previously fabricated master mold in storage and centrifuged at 300g under vacuum for 15 minutes to remove air bubbles. Subsequently, the mixed compound was cured at 60°C for 4 hours, and the master mold was removed to form the PDMS mold.

[0045]

[0046] Fabrication of Hydrogel-forming Microneedles (SI-HFMN) Inducing Hyperchoroidal Space

[0047] PMVE / MA (1980 kDa, Sigma-Aldrich, St. Louis, MO, USA) powder was mixed with PEG (10 kDa, Sigma-Aldrich, St. Louis, MO, USA) granules and DW using a paste mixer (PDM-300, KMtech, Gyeonggi, South Korea) at 1500 rpm for 1 hour. Subsequently, the solution was centrifuged at 3500 rpm for 15 minutes to remove air bubbles. The microcavities of the mold were filled with the solution using a centrifugal casting method. An initial 500 μL of the solution was cast onto the mold surface and centrifuged at 4000 rpm for 15 minutes. The same 500 μL of the solution was added as a backing film layer and centrifuged at 500 rpm for 5 minutes. After centrifugation, the molds containing the solution were dried for 48 hours at a constant humidity (24%) using a dehumidifier (ADH-EV60, HORUSBENNU, Seoul, Korea). Subsequently, the molds were crosslinked in an oven (Lab Companion, JEIO Tech, Seoul, Korea) at 80°C for 24 hours to produce the final PM-SH (PMVE / MA-based SI-HFMN). The diameter and height of the PM-SH were measured using a bright-field microscope.

[0048]

[0049] Example 2. Mechanism and Design of Hydrogel-Forming Microneedles (SI-HFMN) Inducing a Hyperchoroidal Space

[0050] Hydrogel-forming microneedles (SI-HFMN) that induce a hyperchoroidal space utilize the unique mechanism of an expandable HFMN array to induce the formation of a hyperchoroidal space, thereby establishing the posterior ocular region as a drug delivery route. A schematic overview of the mechanism of the hydrogel-forming microneedles (HFMN) is shown in Figure 1a. When the drug-loaded SI-HFMN was inserted into the eye of a patient with a posterior ocular disease, the HFMN absorbed surrounding fluid and expanded, and as the polymer matrix expanded, it acted as a mechanical stimulus for the formation of a hyperchoroidal space, allowing the loaded drug to be released from the hyperchoroidal space formed by the HFMN.

[0051] The microneedles of the present invention were designed as candlelit microneedles to maximize expansion volume at a depth where a hyperchoroidal space can be formed (approximately 500 μm from the limbus), and subsequently provided high mechanical stimulation at a specific depth for efficient hyperchoroidal space formation (Fig. 1b). Unlike other existing conical or funnel-shaped microneedles in which most of the microneedle volume is filled at the “base” far from the location of the hyperchoroidal space, the candlelit microneedles of the present invention filled a relatively larger volume at the “head” where the hyperchoroidal space is located. The length of all microneedles was set to 900 μm, which is long enough to penetrate the sclera and access the hyperchoroidal space at any part of the eye. In contrast to the volume difference of the hyperchoroidal space immediately after insertion, the volume difference after expansion showed dramatic differences among candle-shaped (41%), conical (14%), and funnel-shaped (7%) microneedles, as previously reported, where the microneedle height and basal diameter increased by approximately 150 μm and 75 μm, respectively, and there is a possibility that the volume difference increases further as the insertion time increases. Therefore, the candle-shaped SI-HFMN can efficiently induce the formation of the hyperchoroidal space by maximizing mechanical stimulation through a high expansion volume. Thus, it was confirmed that the candle-shaped SI-HFMN is an excellent method for efficiently inducing the formation of the hyperchoroidal space through mechanical stimulation by maximizing volume distribution and delivering loaded drugs to the posterior ocular region.

[0052]

[0053] Example 3. Fabrication and Characterization of Hydrogel-Forming Microneedles (SI-HFMN) Inducing a Hyperchoroidal Space

[0054] The SI-HFMN array was designed in a 3 × 1 configuration to minimize the application area and reduce ocular invasiveness during application. PMVE / MA was selected as the backbone polymer due to its mechanical strength, biocompatibility, and the ability to form a hydrogel capable of plasticizing and expanding the polymer through ester bonds by crosslinking functional groups with polyhydric alcohols such as PEG (Fig. 2a). Various formulations of compositions used in conventional methods were tested, and the PMVE / MA:PEG ratio was set to 2:1 or 8:3, and 15% PMVE / MA-based SI-HFMN (PM15-SH) and 20% PMVE / MA-based SI-HFMN (PM20-SH) were crosslinked with 7.5% PEG. Additionally, a "super-expanded" hydrogel was induced using a modifier group (PMNA-SH) in which 3% sodium carbonate (Na2CO3) was mixed with 20% PMVE / MA.

[0055] Figure 2b shows the entire fabrication process of the candle-shaped microneedle SI-HFMN array. Using centrifugal casting, a hydrogel solution was filled into a polydimethylsiloxane (PDMS) mold with a candle-shaped cavity (Figure 3a). The mold containing the solution was dried and heat-treated to form a cross-linked SI-HFMN array. Figure 2c shows microscopic images of the formed PM15-, PM20-, and PMNA-SH, which are replicas of the master mold prepared in Figure 3a (n = 9, mean ± SEM). The height is 748 ± 9 μm and the head diameter is 354 ± 7 μm. Although it has been reported that the insertion depth is 650 μm with 100 μm of the existing candle-shaped microneedle remaining uninserted, considering that SI-HFMN can expand, it can be seen that this matches the length (700 μm) of the existing microneedle designed to target the hyperchoroidal space.

[0056] To confirm the chemical shift after crosslinking, the SI-HFMN array was analyzed using attenuated total internal reflection-Fourier transform infrared (ATR-FTIR) based on pure PMVE / MA powder. As expected, the PMVE / MA powder showed 1709 cm⁻¹ corresponding to the carbonyl group (CO) of the carboxylic acid moiety. -1 A strong peak was observed at (Fig. 2d). In contrast, the PM-SH group showed ~1730 cm⁻¹. -1 and ~1780cm -1 A peak was observed at [location]. The former indicates the chemical shift of CO due to crosslinking, while the latter represents the carbonyl ester (CO) symbolizing esterification. ester It indicates the formation of ). Also, ~2930cm of the PM-SH group -1 The peak in [location] was identified as originating from the CH bonds of PEG, confirming crosslinking. Additionally, the PMNA-SH group [regarding] carbonate ions (CO3 2- 1554cm corresponding to the CO of ) -1 A peak was observed at, indicating the presence of Na2CO3. For quantitative analysis, CO of each group ester Ratio of absorbance units (AU) between and COOH (CO ester The ratio of / COOH) was compared (Table 1). The ratio of PM15-SH was 1.27, and the ratios of PM20-SH and PMNA-SH were 0.54 and 0.27, respectively. As the number increases, CO ester This indicates that more groups are formed and the crosslinking density is higher. This is expected to be because, unlike the polymer-crosslinker ratio of 8:3 for PM20-SH and PMNA-SH, the ratio for PM15-SH is 2:1, resulting in more polymer being crosslinked and a reduction in residual unreacted COOH. Meanwhile, PM20-SH Na + The crosslinking density was higher than that of PMNA-SH because ions formed the free acid and sodium salt of PMVE / MA, competitively reducing the binding sites of PEG. Overall, all PM-SH groups CO ester It shows that the group has increased, indicating that the bridging is successful.

[0057]

[0058] COOH and CO ester AU values ​​for each formulation at each peak Absorbance Units PM15-SH PM20-SH PMNA-SHCOOH 0.0157 10.03767 0.01855CO ester 0.019950.020270.00495

[0059]

[0060] Example 4. Breaking force and in vitro insertion analysis of hydrogel-forming microneedles (SI-HFMN) inducing a hyperchoroidal space

[0061] Since the sclera, which has a high-density collagen-rich fibrous structure designed to protect the eyeball and provide structural integrity, possesses high mechanical strength, we investigated whether each SI-HFMN formulation could penetrate the sclera by measuring the breaking force using a force analyzer (Fig. 4a). It has been reported that an average of 2.07 N is required to penetrate the sclera and inject into the hyperchoroidal space using conventional microneedles, as indicated by the dashed line in Fig. 4b. The average breaking forces (n = 10, mean ± SEM) of each PM15-, PM20-, and PMNA-SH sufficient for scleral penetration were 2.1 ± 0.3 N, 5.1 ± 0.7 N, and 4.5 ± 1.2 N, respectively.

[0062] SI-HFMN was applied to an in vitro sclera-mimicking model composed of PDMS at a 20:1 ratio, which was used to generate the artificial eye model. The PM15-SH and PM20-SH arrays successfully penetrated the model and maintained a candle shape, whereas the PMNA-SH group failed to penetrate the PDMS surface despite having a higher breaking force than PM15-SH (Fig. 4c).

[0063]

[0064] Example 5. Analysis of expansion kinetics of hydrogel-forming microneedles (SI-HFMN) inducing a hyperchoroidal space

[0065] The expansion kinetics of the SI-HFMN formulation were analyzed to predict the ability to form a superchoroidal space. Each array was immersed in phosphate-buffered saline (PBS) to mimic the human physiological environment, and the mass of the arrays was measured at each time point up to 3 hours, referencing previous reports that expansion becomes relatively saturated within 200 minutes. The expansion rates (S%) of PM15-SH and PM20-SH were 287±38% and 356±28%, respectively (Fig. 5a, n=6). Upon checking the individual S% per time point, PM15-SH and PM20-SH did not show a significant difference (Fig. 6a).

[0066] The expansion behavior was further analyzed by deriving expansion parameters using pseudo-second-order kinetic equations, which are used to model the expansion caused by the interaction between the hydrogel and water molecules (Table 2). Figure 5b shows the linearized form of S% in the t versus t / S plot. The respective r2 values ​​for PM15-SH and PM20-SH were 0.96 and 0.97, indicating a relative correlation with the linear trend, which suggests that pseudo-second-order kinetics is a valid model for inferring expansion parameters. Using linear regression, it was derived that PM15-SH (556%) had a lower equilibrium expansion (S∞) value compared to PM20-SH (714%), confirming the S% trend. Additionally, PM15-SH (9.41) had a larger expansion rate constant (ks) than PM20-SH (5.35) because it took less time to reach equilibrium due to its lower S∞. In addition, equilibrium water content (EWC) and gel fraction (GF) were calculated to verify the S% results. There was no significant difference in EWC (P = 0.94) between PM15-SH (558±21) and PM20-SH (583±11), nor was there a significant difference in GFPBS ​​(P = 0.27) between PM15-SH (98±1%) and PM20-SH (97±1%). These results follow a pattern of high EWC and low GF corresponding to high S%. Furthermore, the higher porosity value (Φ) of PM20-SH (15±2%) compared to PM15-SH (10±2%) implies that the hydrogel matrix has higher porosity as the crosslinking density decreases, resulting in a higher overall S%. In summary, considering the superior strength and expandability of PM20-SH, it can be seen that it is more suitable for hyperchoroidal space induction and drug release compared to PM15-SH.

[0067]

[0068] SI-HFMN Expansion Parameters in PBS Solution.FormulationSΔ [%]k s *[(mg / mg) / min]EWC PBS [%]GF PBS [%]Φ[%]PM15-SH5569.41558 ± 2198 ± 110 ± 2PM20-SH7145.35583 ± 1197 ± 115 ± 2* = 10 -5

[0069]

[0070] In addition, morphological changes of each formulation were observed through qualitative analysis using SEM (Fig. 5c). Before expansion, the backing films of each formulation, composed of the same formulation in each array, were similar in surface characteristics (red box), with an overall smooth surface. However, according to the magnified view of the film after expansion (black dashed line), the PM15-SH formulation, which has a lower crosslinking density, showed a harder surface, whereas PM20-SH showed a sponge-like, wrinkled surface indicating greater moisture absorption due to a looser crosslinking density. Both PM15-SH and PM20-SH exhibited an elongated shape from their original structures, implying similar expansion behavior.

[0071] In addition, the volume difference (V%) of SI-HFMN at each time point in PBS was analyzed to visualize and predict the expansion patterns of each formulation applied to the ocular, an aqueous environment. The SI-HFMN array was imaged at predetermined time points (Fig. 6b), and the images were converted to Cartesian coordinates, with the height of SI-HFMN set as the x-axis and the surface as the y-axis (Fig. 6c). The curves were integrated at each interval, and the resulting volume changes are shown in Fig. 6d (n = 8, mean ± SEM). Consistent with the S% trend, the volume increase was generally higher for PM20-SH (1094 ± 85%) than for PM15-SH (1025 ± 64%), although the differences were generally not significant. The results indicated that while PM20-SH showed slightly higher expansion, there was no significant difference in the overall expansion behavior between PM15-SH and PM20-SH.

[0072]

[0073] Example 6. Drug release analysis of hydrogel-forming microneedles (SI-HFMN) inducing a hyperchoroidal space

[0074] The drug release kinetics of the SI-HFMN array were calculated as the percentage of the drug released at each time point (C%) by dividing the drug concentration released at each time point (Ct) by the relative maximum release concentration (Cmax) (Cmax is the total drug concentration at 24 hours). The drug release of various SI-HFMN formulations was evaluated to further derive the optimal formulation for induction of the hyperchoroidal space and drug delivery to the posterior ocular region. After immersing the Li-HCl-loaded SI-HFMN array in PBS solution, partial samples were extracted every 10 minutes up to 60 minutes, and then up to a maximum of 1440 minutes (24 hours). The cumulative release rate is graphed in Fig. 8c (n = 5, mean ± SEM), where the 24-hour cumulative amount was set to 100% and each time point represents the relative release rate. Both groups exhibited an initial explosive release up to 120 minutes, with PM15-SH and PM20-SH releasing 94.8±0.7% and 93.7±0.6% of the loaded amount, respectively, and both groups showed a release rate of 0.78% / min at 120 minutes, which was calculated based on the slope of the graph. Given that the long application time of SI-HFMN may not be suitable for the eye, the rapid drug release rate may be ideal for delivering to the posterior ocular area in a less invasive manner, as the required wearing time could be much shorter.

[0075] In addition, to analyze ultrafast emission trends in depth, Tao Lu's kinetic model was used to obtain Li-HCl emission parameters from the SI-HFMN array. The linear graphs for PM15-SH and PM20-SH (Fig. 7b) both showed an r of 0.98. 2The value was derived to indicate that this model is feasible. The slope of the graph was used to determine the emission rate constant (k ** ; ** = 10 -2 ) was calculated, and the resulting values ​​were 6.0 ± 0.7 and 5.6 ± 0.6 min for the PM15-SH and PM20-SH groups, respectively. -1 It was (Table 3). PM15-SH was k ** Since the value was higher but the difference between the two groups was not large (P = 0.56), it indicates that PM20-SH may be more suitable for ocular application considering its superior mechanical strength and similar drug delivery efficiency.

[0076]

[0077] Loading and emission kinetic parameters for Li-HCl in SI-HFMN array.Formulation P*[cm / s]K d D*[cm 2 / s]k**[min -1 ]PM15-SH10 ± 10.10 ± 0.017.46.0 ± 0.7PM20-SH18 ± 10.18 ± 0.029.75.6 ± 0.6* = 10 -6 , ** = 10 -2

[0078]

[0079] Example 7. Evaluation of drug delivery to the posterior ocular region through the formation of a superchoroidal space

[0080] To predict whether the expandability of SI-HFMN could induce the formation of a superchoroidal space, the expandability strength of each formulation was first evaluated using a 5% (w / v) agarose gel, an in vitro tissue model widely used in drug delivery studies. An array loaded with Rhodamine B (Rho B) was applied to the model (Fig. 8a). PM20-SH successfully ruptured and displaced the agarose gel (black dashed line) and released the loaded drug, whereas PM15-SH had little effect on the agarose gel, resulting in minimal expansion and low drug release. Relative Fluorescence Intensity Units (RFU) were quantitatively inferred from the fluorescence images (Fig. 8b, n = 4, mean ± SEM). PM20-SH showed at least 1.6 times the RFU at each time point (Table 4), indicating that PM20-SH has higher mechanical strength and can release the drug more efficiently than PM15-SH.

[0081]

[0082] RFU values ​​for each formulation at various time points Formulation 30 min * 60 min * Removal ** PM15 - SH 1.0 ± 0.5 1.2 ± 0.1 2.3 ± 0.9 PM20 - SH 1.6 ± 0.2 2.1 ± 0.2 3.7 ± 0.3 * = 10 8 , ** = 10 7

[0083]

[0084] Subsequently, pig carcass eyes were obtained from a local slaughterhouse, and optical coherence tomography (OCT), a non-invasive ophthalmic imaging device used to obtain 3D in vivo information, was used to observe the induction of hyperchoroidal space formation via SI-HFMN in exvivo pig eyes. Figure 9a shows brightfield and OCT images of SI-HFMN applied to exvivo pig eyes, demonstrating that PM20-SH can induce space formation within the tissue through complete application (red circle) and expansion (yellow dotted line) in the exvivo pig eyes. Meanwhile, PM15-SH showed linear expansion, indicating that only the tip of the SI-HFMN may have been inserted. Furthermore, unlike the in vitro results where the S% and V% for PM20-SH were approximately 170% and 700%, respectively, at the 60-minute mark, the actual expansion in the exvivo tissue was relatively minimal when referring to the OCT images. This result was expected because the in vitro experiment was conducted in a PBS solution with minimized resistance to the expansion of PM20-SH. Conversely, the dense fibrous network of the sclera, which exhibits high resistance, may have reduced the expandability of SI-HFMN. However, despite this resistance, PM20-SH was able to insert into and expand within the sclera, altering tissue structure and creating space. Therefore, it was found that PM20-SH can induce the formation of a superchoroidal space through its expandability.

[0085] Using Nile Red as a model drug, the ability of SI-HFMN to deliver the loaded drug to the posterior ocular region via hyperchoroidal space induction was evaluated. Since PM15-SH failed to penetrate the sclera, PM20-SH was selected as the final formulation for evaluation. Figure 9b shows an overview of the analysis process, where SI-HFMN loaded with Nile Red was applied 4 mm away from the limbus, the initial hyperchoroidal space induction area. After 1 hour, the microneedle array was removed, the top view was immediately imaged, and the section was cut for a cross-sectional view. Figure 9c shows a top-view image demonstrating the successful insertion of SI-HFMN into the eye. Additionally, the fluorescence image of the cross-section showed that the dye diffused into the posterior ocular region through the space formed near the sclera, appearing as traces of a red fluorescence signal (Figure 10d).

[0086] Furthermore, a bluish-purple Nile Red dye appeared in the magnified cross-section of the posterior ocular region in brightfield images. Additionally, since no diffusion of the fluorescent signal into the choroidal region of the eye was observed, it was hypothesized that SI-HFMN-induced delivery specifically targeted the hyperchoroidal space, thereby preventing the drug from diffusing to other regions of the eye. Therefore, this indicates that optimized candle-shaped SI-HFMN can be utilized as a hyperchoroidal space-induced drug delivery technology targeting the posterior ocular region.

[0087]

[0088] Foregoing, specific parts of the present invention have been described in detail. It is evident to those skilled in the art that such specific descriptions are merely preferred embodiments and do not limit the scope of the invention. That is, the actual scope of the invention is defined by the appended claims and their equivalents.

Claims

1. Microneedles for drug delivery to the posterior ocular region containing a hydrogel.

2. In Paragraph 1, The above microneedles are drug delivery microneedles characterized by creating a superchoroidal space.

3. In Paragraph 1, The above microneedles are drug delivery microneedles characterized by expanding to separate the sclera and the choroid.

4. In Paragraph 3, A drug delivery microneedle comprising a head portion and a base portion, characterized in that the head portion expands to separate the sclera and the choroid.

5. In Paragraph 1, The above-mentioned microneedle is a drug delivery microneedle characterized by being candle-shaped.

6. In Paragraph 1, The above hydrogel is a drug delivery microneedle characterized by being cross-linked with polymethylvinyl ether-alt-maleic acid (PMVE / MA) and polyethylene glycol (PEG).

7. In Paragraph 6, A drug delivery microneedle characterized by comprising the above hydrogel at a concentration of 15 to 25% (w / w) polymethylvinyl ether-alt-maleic acid (PMVE / MA) and 5 to 10% (w / w) polyethylene glycol (PEG).

8. In Paragraph 1, The above microneedles are drug delivery microneedles characterized by having a mechanical strength of 1.0 to 10.0 N.

9. In Paragraph 1, The above microneedles are drug delivery microneedles characterized by having an expansion rate of 100 to 500%.

10. In Paragraph 1, The above microneedle is a drug delivery microneedle characterized by preventing backflow after drug delivery.

11. In Paragraph 1, A microneedle for drug delivery characterized in that the above-mentioned drug is one or more selected from the group consisting of hydrophilic drugs, hydrophobic drugs, and mixtures thereof.

12. In Paragraph 1, The above microneedles are drug delivery microneedles characterized by being for the treatment of ophthalmic diseases.

13. In Paragraph 12, A microneedle for drug delivery characterized by the above ophthalmic disease being accompanied by eye pain or reduced vision.

14. A drug delivery device for the posterior ocular region comprising a drug delivery microneedle according to any one of claims 1 to 13.

15. A drug delivery method comprising the step of mounting a drug delivery microneedle according to any one of claims 1 to 13 on the posterior surface of the eye.

Images