Injectable adhesive microcarrier with layered structure as well as preparation method and application of injectable adhesive microcarrier

Abstract

The invention discloses an injectable adhesive microcarrier with a layered structure as well as a preparation method and application of the injectable adhesive microcarrier, a hydrogel microcarrier is constructed by a microfluidic technology, and the size of the microcarrier is adjusted by adjusting the flow rate and the voltage; the generated polydopamine is attached to the surface of the microcarrier through a dopamine oxidation auto-polymerization method, and the layered microcarrier with adhesion and responsiveness is obtained. The prepared microcarrier has a three-dimensional network structure and a hydrophilic property, can provide sufficient space for loading of various drugs, and controls the photo-thermal conversion property of the microcarrier by adjusting near-infrared irradiation, so that the drug release process is controlled, and the drug delivery efficiency is improved. Due to the characteristics, the injectable adhesive microcarrier with the layered structure can overcome the limitation of a middle ear drug delivery system. The invention has the advantages of reusability, low cost, simplicity in operation, convenience, reliability, high biocompatibility, inner ear targeting and the like.

Description

Technical Field

[0001] The invention belongs to the field of biomaterials, and in particular relates to an injectable adhesive microcarrier with a layered structure and a preparation method and application thereof. Background Art

[0002] Hearing loss is one of the most common health defects in adults. According to the World Hearing Report released by the World Health Organization (WHO) in 2021, a total of 1.5 billion people in the world suffer from varying degrees of hearing loss, of which about 430 million suffer from disabling hearing loss. Hearing loss causes economic losses of more than US$979.6 billion worldwide each year. The latest results of the second national sample survey of people with disabilities show that hearing-impaired patients in my country account for 24.2% of the total number of people with disabilities. In addition, my country is facing severe and complex hearing disadvantages, especially industrial noise pollution and the continued deepening of the aging population. Deafness has become an increasingly serious disease affecting national health and economic and social development.

[0003] At present, the inner ear drug delivery systems in clinical practice are mainly divided into systemic administration and local inner ear administration. The former is the most commonly used drug delivery method in clinical practice. Many drugs enter the cochlea in very small amounts or cannot pass through the blood labyrinth, which limits the application of systemic administration in inner ear treatment. In contrast, intratympanic injection of drugs can bypass these barriers, increase the drug concentration in the cochlea to increase the drug efficacy, and reduce the systemic exposure of the drug. However, due to the presence of the Eustachian tube, it is difficult for the drug to remain in the middle ear cavity, and repeated injections are required to achieve the desired therapeutic effect. In order to avoid the damage caused by multiple injections and improve the therapeutic effect, local drug delivery systems derived from various materials such as microcatheters, micropumps, hydrogels, micro- and nanoparticles have emerged. Although great progress has been made, most of these carriers are controversial due to their simple structure, low biocompatibility and easy degradation in the body, and the therapeutic effect is unsatisfactory. In addition, due to the unique anatomical structure of the inner ear, carriers without sufficient adhesion are difficult to stay in the middle ear cavity for a long time, and drugs cannot continue to enter the inner ear to exert their therapeutic effects. Therefore, it is of great significance for the prevention and treatment of deafness to construct a multifunctional delivery carrier with minimally invasive delivery and controllable manipulation characteristics and to find a safer and more effective inner ear drug delivery strategy. Summary of the invention

[0004] Purpose of the invention: The technical problem to be solved by the present invention is to provide an injectable middle ear microcarrier with adhesiveness and responsiveness and a preparation method thereof in view of the deficiencies of the prior art, so as to solve the shortcomings of the traditional inner ear drug delivery method, such as poor targeting, low bioavailability and poor biocompatibility.

[0005] In order to achieve the above object, the technical solution adopted by the present invention is as follows: A method for preparing an injectable adhesive microcarrier with a layered structure comprises the following steps: (1) Building a microfluidic device, adding an aqueous alginate solution to an aqueous calcium chloride solution under the action of an electric field to obtain monodisperse alginate microcarriers; (2) dissolving dopamine in Tris buffer to prepare a dopamine (DA) solution, and reacting in the dark to obtain adhesive polydopamine (PDA) nanoparticles; (3) Soaking the alginate microcarrier prepared in step (1) in the dopamine solution prepared in step (2) to carry out a polymerization reaction, so that the polydopamine nanoparticles adhere to the surface of the alginate microcarrier, and freeze-drying the product.

[0006] Specifically, in step (1), the solute of the alginate aqueous solution is sodium alginate, and the concentration is 10-20 g / L.

[0007] Specifically, in step (1), the end of the microfluidic device is placed under an electric field, and the alginate aqueous solution droplets are formed into a Taylor cone by the action of the electric field; the electric field voltage is 8-14KV, and the flow rate of the alginate aqueous solution added by the microfluidic device is 80-120 mL / h. The droplet size can be precisely controlled by adjusting the voltage, height, and flow rate parameters on the peristaltic pump, and the liquid can be divided into droplets of different sizes. The droplet size decreases with increasing voltage and flow rate, and becomes smaller with increasing height.

[0008] Specifically, in step (1), the concentration of the calcium chloride aqueous solution is 10-20 g / L; the obtained monodisperse alginate microcarriers are washed with pure water to remove the residual calcium chloride on the surface.

[0009] Specifically, in step (1), the diameter of the monodisperse alginate microcarriers obtained is 80-95 μm.

[0010] Specifically, in step (2), the Tris buffer has a concentration of 10 mM and a pH value of 8.5, and the concentration of the prepared dopamine solution is 1-4 mg / mL.

[0011] Specifically, in step (2), the alginate microcarrier is reacted in a dopamine solution in the dark for more than 10 hours, and the average diameter of the adhesive polydopamine (PDA) nanoparticles is 100-140 nm. PDA is obtained by oxidative self-polymerization, and polydopamine is grafted onto the surface of the microcarrier using surface modification technology to give it good tissue adhesion and photothermal properties. Step (2) and step (3) can be reacted in the same step, and the generated polydopamine is attached to the surface of the microcarrier by the method of dopamine oxidative self-polymerization, so as to obtain a layered microcarrier with adhesion and responsiveness. PDA can be quickly loaded on the surface of the microcarrier, and the loading rate can reach 24.24±0.45% after 24 hours.

[0012] The freeze-dried adhesive and responsive layered injectable microcarriers have a three-dimensional network structure and hydrophilic properties, which can ensure that the thermoresponsive hydrogel microspheres can expand rapidly in the solution and absorb a large amount of liquid. The freeze-dried thermoresponsive hydrogel microcarriers reached swelling equilibrium after being soaked in PBS for 4 hours, and the swelling capacity was more than 4000 times.

[0013] In addition, the prepared adhesive and responsive layered injectable microcarriers can be heated to 40°C after 1 W / cm² infrared irradiation. In five on / off cycles of exposure to near-infrared light irradiation. In each cycle, when the near-infrared light is turned on, the sodium alginate microcarriers show a rapid temperature rise to 40°C and immediately cool back to their initial temperature after the near-infrared light is turned off, showing controllable thermal properties.

[0014] Furthermore, the injectable adherent microcarriers with a layered structure prepared by the above preparation method are also within the protection scope of the present invention, and the average diameter of the prepared injectable microcarriers is 82-95 μm.

[0015] Furthermore, the present invention also claims the use of the above-mentioned injectable microcarrier for loading antioxidant drugs, wherein the antioxidant drugs include but are not limited to the universal antioxidant α-lipoic acid.

[0016] Furthermore, the present invention also claims to protect the use of the above-mentioned injectable microcarriers for drug administration to the middle ear, specifically: preparing a drug solution, immersing the injectable adhesive microcarriers with a layered structure in the drug solution, allowing the drug solution to fully penetrate into the pores of the microcarriers, thereby achieving drug loading. Beneficial Effects

[0017] (1) Based on microfluidic technology, hydrogel microcarriers are constructed by microfluidic technology, and the size of the microcarriers is adjusted by adjusting the flow rate and voltage. The generated polydopamine is attached to the surface of the microcarrier by the self-polymerization of dopamine oxidation, that is, a hierarchical injectable adhesive microcarrier. The prepared microcarrier has a three-dimensional network structure and hydrophilic properties, which can provide sufficient space for the loading of various drugs. The photothermal conversion properties of the microcarrier are controlled by adjusting near-infrared irradiation, thereby realizing the control of the drug release process. These properties enable the hierarchical injectable adhesive microcarrier of the present invention to overcome the limitations of the middle ear drug delivery system. This microfluidic-based preparation method has the advantages of low cost, simple operation, convenience and reliability.

[0018] (2) The hierarchical injectable adhesive microcarrier prepared by the present invention has a three-dimensional network structure and hydrophilic properties, which can provide sufficient space for the loading of various drugs. It can be used to treat deafness, and the photothermal conversion properties of the microcarrier can be controlled by adjusting near-infrared irradiation, thereby achieving controlled drug release process. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] The present invention will be further described in detail below in conjunction with the accompanying drawings and specific embodiments, and the above and / or other advantages of the present invention will become more clear.

[0020] Figure 1 Schematic diagram of the preparation of hierarchical injectable adherent microcarriers and their application in inner ear delivery.

[0021] Figure 2 Optimization and adhesion properties of injectable adhesive microcarriers with hierarchical structures (a) Electron microscopy images of PDA nanoparticles. (bc) Microscopic images of MCs and PDA@MCs. (de) Scanning electron microscopy images of PDA@MCs. (f) Particle size statistics of PDA@MCs at different voltages. (gh) Statistical size distribution of MCs and PDA@MCs (n = 150). (i) Swelling curves of PDA@MCs in PBS. (jk) Adhesion properties of MCs and PDA@MCs.

[0022] Figure 3 The drug loading rate and drug loading capacity of injectable adhesive microcarriers with hierarchical structures: (a) Confocal scanning images of PDA@MCs loaded with RHB at different immersion times. (b) Standard curve of RHB in PBS. (c) Drug loading capacity of PDA@MCs within 24 hours.

[0023] Figure 4 The distribution and metabolism of the injectable adhesive microcarrier loaded with drugs in the cochlea. (a) Fluorescence images of the in vivo cochlea of ​​the mouse middle ear injected with PDA@MCs-Cy7 at different time points for 11 consecutive days. (b) Fluorescence images of the isolated cochlea of ​​the mouse middle ear injected with PDA@MCs-Cy7 at different time points for 11 consecutive days. (c) Images of the in vivo cochlea of ​​the mouse middle ear injected with Cy7 at different time points for 4 consecutive days in the control group. (d) Fluorescence images of the isolated cochlea of ​​the mouse middle ear injected with Cy7 at different time points for 4 consecutive days in the control group. (e) Relative fluorescence intensity of the in vivo cochlea of ​​the mouse injected with PDA@MCs-Cy7 at different time intervals. (f) Relative fluorescence intensity of the isolated cochlea of ​​the mouse injected with PDA@MCs-Cy7 at different time intervals. (g) Relative fluorescence intensity of the in vivo cochlea of ​​the mouse in the control group at different time intervals. (h) Relative fluorescence intensity of the isolated cochlea of ​​the mouse in the control group at different time intervals.

[0024] Figure 5In vivo photothermal study of injectable adhesive microcarriers with hierarchical structures (a) In vivo thermal imaging of MCs and PDA@MCs injected into the middle ear of mice and irradiated with 1W / cm2 near-infrared radiation for 5 minutes. (b) Fluorescence intensity in the cochlea of ​​the control group without NIR and the experimental group with NIR. (c) Statistical analysis of the fluorescence intensity in the cochlea of ​​the two groups in (b).

[0025] Figure 6 The layered structure of the injectable adhesive microcarrier was used to verify its ability to antagonize cisplatin ototoxicity in mice. (a) Timeline of injection of PDA-MCs-ALA. (bd) Spreading of the cochlear basilar membrane of mice in the control group, cisplatin group, and PDA@MCs-ALA group. (e) Statistical analysis of the survival rate of OHCs in each group. (fh) ABR results of mice in each group. DETAILED DESCRIPTION

[0026] The present invention can be better understood with reference to the following examples. Example 1

[0027] Combination Figure 1 As shown, the preparation method of the layered structured injectable adhesive microcarrier of the present invention comprises the following steps: (1) Building a microfluidic device, adding an aqueous alginate solution to an aqueous calcium chloride solution under the action of an electric field to obtain monodisperse alginate microcarriers; (2) dissolving dopamine in Tris buffer to prepare a dopamine (DA) solution, and reacting in the dark to obtain adhesive polydopamine (PDA) nanoparticles; (3) Soaking the alginate microcarrier prepared in step (1) in the dopamine solution prepared in step (2) to carry out a polymerization reaction, so that the polydopamine nanoparticles adhere to the surface of the alginate microcarrier, and freeze-drying the product.

[0028] The prepared hierarchical injectable adhesive microcarriers (PDA@MCs) are immersed in a drug solution to allow the drug solution to fully penetrate into the pores of the microcarriers, thereby obtaining drug-loaded injectable microspheres, which can be administered to the middle ear by injection, effectively preventing and treating deafness. Example 2

[0029] In this example, polypamine was used to modify the surface of sodium alginate microcarriers. Dopamine (DA) was prepared in 10 mM Tris buffer (PH = 8.5) and protected from light for 12 hours to produce adhesive polydopamine (PDA). The obtained PDA nanoparticles showed significant uniformity with an average diameter of 127 ± 7.44 nm (see Figure 2 (a) Layered injectable hydrogel microcarriers endowed with adhesive and responsive properties after polymerization with PDA. Example 3

[0030] This embodiment provides a method for preparing a hierarchical structured injectable adhesive microcarrier (PDA@MCs), comprising the following steps: Step S1, construction of microcarrier Build a microfluidic platform and prepare monodisperse sodium alginate microcarriers: Dissolve 20g / L high-viscosity sodium alginate and draw it into a syringe. The voltage generator is used to provide different voltages and generate an electric field. Under the action of the electric field, the droplets at the end of the channel are deformed into a Taylor cone, and then the droplets are collected in a container containing 20g / L calcium chloride (CaCl2) solution. By changing the flow rate and voltage in the microcontroller, the liquid is divided into droplets of different sizes. Then, the microcarriers are washed with pure water (repeated 3 times) to remove residual calcium chloride.

[0031] Adjust the size of microspheres according to demand: By adjusting the voltage, height and flow rate, i.e. the flow rate parameter on the peristaltic pump, the droplet size can be precisely controlled. The droplet size decreases with increasing voltage and flow rate, and becomes smaller with increasing height. Finally, the voltage was selected to be 12KV and the flow rate was 100 mL / h. The diameter of the prepared microcarrier was 86.9 ± 4.8μm (see Figure 2 (b, g, f).

[0032] Step S2: Construction of PDA-modified adhesive and responsive layered injectable microcarriers Dopamine (DA) of different concentrations was weighed and dissolved in 10 mM Tris buffer (PH = 8.5), and then the prepared microcarriers were immersed in the DA solution in the reaction. After 12 hours of reaction in the dark, polydopamine (PDA) was obtained. After the microcarriers were polymerized with PDA, the diameter of the injectable hydrogel microcarriers (PDA@MCs) with adhesion and responsiveness was 87.6.6 ± 5.0 μm, and the size was uniform (see Figure 2 in ce, h).

[0033] Step S3: Adhesion properties of the prepared injectable adhesive microcarrier with layered structure The simple microcarriers (MCs) and PDA@MCs were adhered to the surface of mouse skin, immersed in water and shaken. After shaking, PDA@MCs remained adhered to the surface of mouse skin, while MCs quickly slipped off the skin surface (see Figure 2 Thus, PDA imparts adhesion properties to microcarriers. Example 4

[0034] Study on drug loading rate and drug loading capacity of prepared injectable adhesive microcarriers with hierarchical structure (PDA@MCs): The freeze-dried porous PDA@MCs hydrogel microspheres were immersed in lipoic acid (ALA) solution, and the drugs were adsorbed into the three-dimensional network structure of PDA@MCs by reabsorption and swelling. In order to determine the loading behavior of the drug, we chose rhodamine B (RHB) instead of ALA as a model drug. After the drug loading was completed, the supernatant was collected, and the microcarriers were repeatedly washed with fresh PBS to remove excess drugs on the surface. The washing liquid was also collected, mixed with the supernatant taken out before, and the volume was fixed. 100μL of the solution was aspirated into a 96-well plate, and the drug absorbance was measured using an enzyme reader to calculate the drug encapsulation rate and loading rate. In addition, the microcarriers were observed using a confocal microscope to determine the distribution of the drug in the microcarriers. It can be observed from the laser confocal image that RHB with red fluorescence is evenly distributed in the PDA@MCs, indicating that the drug was completely loaded after immersion for 12 hours (see Figure 3 (a) in the figure. Next, the loading rate of polydopamine alginate microcarriers was studied by the standard curve method. First, the standard curve of RHB in PBS was recorded. Then, the loading rate of PDA@MCs was calculated by measuring the absorbance of RHB in PBS. PDA@MCs could load about 23.62±0.26% of RHB after immersion for 10 minutes, and 24.24±0.45% of RHB after 24 hours, at which time the loading capacity of the photothermal microcarrier reached saturation. This result shows that PDA@MCs has a fast loading capacity, which may be related to its porous structure and is easy to use. Example 5

[0035] Distribution and metabolism of PDA@MCs-loaded drugs in the cochlea: In vivo absorption and transport distribution is a major part of the in vivo evaluation of drug-carrying systems. It is worth noting that as a commonly used near-infrared fluorescent dye, Cy7 can generate signals in deep tissues, so it is used to simulate drug molecules and tracked by an in vivo imaging system (IVIS). In this study, Cy7 fluorescent dye was selected to replace ALA for in vivo tracing observation, and IVIS was used to observe the distribution of PDA@MCs in the cochlea after intratympanic administration. Cy7 was loaded in PDA@MCs, and continuous observation was performed using IVIS, and the fluorescence results were statistically analyzed. The results showed that the fluorescence signal of the injected PDA@MCs-Cy7 lasted for more than 11 days and showed a slow downward trend (Figure 4a, e). In addition, 11 days after PDA@MCs-Cy7 was injected into the middle ear, fluorescent signals were observed in the isolated cochlea of ​​mice in the PDA@MCs-Cy7 group, proving that the drug can passively penetrate into the inner ear through the RWM (see Figure 4b, f). In contrast, the fluorescence signal of the carrier in the control group (direct injection of Cy7) lasted only about 4 days (see Figure 4c, g), and there was almost no fluorescence in the cochlea after 4 days in the inner ear (see Figure 4d, h). These results show that PDA@MCs has obvious adhesion, increases the retention time of drug microspheres in the middle ear cavity, and improves the bioavailability of drugs. Example 6

[0036] In vivo photothermal effect and drug release of PDA@MCs The results of in vitro studies showed that the photothermal heating properties of PDA@MCs can be controlled by adjusting the NIR irradiation. On this basis, to further verify the photothermal properties of PDA@MCs to accelerate drug release without burning the skin in vivo, we injected PDA@MCs into the middle ear of mice. PDA@MCs heated effectively under NIR irradiation and heated to 42°C within 5 minutes after receiving NIR irradiation, indicating that it has appropriate in vivo heating capacity (see Figure 5 (a).

[0037] The PDA added to the thermoresponsive microcarrier can be controllably released through near-infrared stimulation. When the PDA-doped hydrogel microparticles are exposed to near-infrared light, the local temperature rises, and the drug molecules undergo faster molecular motion, thereby accelerating the release of the drug. Once the near-infrared is turned off, the temperature will gradually return to room temperature and the drug release will slow down. In order to further evaluate the effect of photothermal on the entry of drugs into the inner ear, we performed near-infrared heating on the PDA@MCs-Cy7 injected into the middle ear. The control group was not heated, and the fluorescence intensity of the cochlea in the two groups was observed during the same time period to evaluate whether near-infrared accelerates the entry of drugs into the inner ear. Studies have found that the fluorescence intensity of the cochlea after photothermal treatment was higher than that of the control group at different time periods (see Figure 5 b, c). Therefore, it is shown that Cy7 is released from the microparticles and can promote the entry of drugs into the inner ear to promote drug delivery after near-infrared irradiation. This study provides important technical guidance and theoretical basis for the construction and functional modification of microcarriers in this project. Example 7

[0038] Statistical results of mouse suprabasal outer hair cells (OHCs) and hearing loss assessment The hearing protection effect of PDA@MCs-ALA against cisplatin (CDDP) ototoxicity was evaluated by an adult mouse model. The injection level of the mouse middle ear is a prerequisite for inner ear treatment. PDA@MCs are small in diameter and easy to inject, making them a good biomaterial for middle ear drug delivery. The mouse tympanic membrane was exposed under a microscope, and then PDA@MCs-ALA was injected into the middle ear. In order to further investigate the pre-protective effect of PDA@MCs-ALA, we conducted the following animal experiments: 40-day-old mice were divided into a control group, a CDDP group, and a PDA@MCs-ALA group. The control group mice only had a tympanic membrane perforation model in the ear. In the CDDP group, after the tympanic membrane perforation model was made in the mouse ear, 25 mg / Kg of CDDP was intraperitoneally injected. In the PDA@MCs-ALA group, PDA@MCs-ALA was first injected into the mouse ear, and then 25 mg / Kg of CDDP was intraperitoneally injected the next day (see Figure 6 (a).

[0039] Statistical results of outer hair cells (OHCs) In order to observe CDDP ototoxicity, the cochlear outer hair cells of the control group, CDDP group and PDA@MCs-ALA group were counted. Figure 6 b), CDDP caused severe damage to the bottom and middle circles of OHCs (see Figure 6 Compared with the control group, the PDA@MCs-ALA group had a more significant protective effect on OHCs (see Figure 6 (d). As we all know, the cochlea is an important organ for sensing sound. The vibration of the basilar membrane in different forms caused by sounds of different frequencies is considered to be the basis for the cochlea to distinguish different sound frequencies. Experiments on the destruction of basilar membranes in different parts of animals and clinical studies on the causes of deafness of different natures have proved this conclusion, that is, when the base of the cochlea is damaged, high-frequency hearing is mainly affected, and when the top of the cochlea is damaged, low-frequency hearing is mainly affected. These results show that the prepared PDA@MCs-ALA group effectively delivers drugs to the inner ear and has a good protective effect on OHCs.

[0040] Auditory brainstem response (ABR) is a commonly used electrophysiological index in hearing tests and has been routinely used in basic hearing research to objectively detect the hearing of small animals. ABR thresholds were measured 3 days before treatment and 10 days after injection. The results showed that there was no change in hearing in the control group (see Figure 6 f), indicating that the hearing of mice was not damaged 10 days after tympanic membrane perforation modeling. However, the ABR threshold of the CDDP group changed significantly 10 days after CDDP treatment, showing obvious hearing loss (see g in Figure 6). In contrast, the ABR threshold of mice in the PDA@MCs-ALA group changed slightly compared with before CDDP treatment (see h in Figure 6). These results indicate that PDA@MCs successfully delivered the loaded ALA to the inner ear and played a protective role against hearing loss caused by CDDP. These results indicate that PDA@MCs-ALA significantly prevents CDDP-induced hearing loss in mice.

[0041] The present invention provides an injectable adhesive microcarrier with a layered structure and a method for preparing and applying the same. There are many methods and approaches to implement the technical solution. The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be considered as the scope of protection of the present invention. All components not specified in this embodiment can be implemented using existing technologies.

Claims

1. A method for preparing an injectable adhesive microcarrier with a layered structure, characterized in that: The steps include: (1) Building a microfluidic device, adding an aqueous alginate solution into an aqueous calcium chloride solution under the action of an electric field to obtain monodisperse alginate microcarriers; (2) dissolving dopamine in Tris buffer to prepare a dopamine solution, and reacting in the dark to obtain adhesive polydopamine nanoparticles; (3) Soaking the alginate microcarrier prepared in step (1) in the dopamine solution prepared in step (2) to carry out a polymerization reaction, so that the polydopamine nanoparticles adhere to the surface of the alginate microcarrier, and freeze-drying the product.

2. The method for preparing the layered structured injectable adhesive microcarrier according to claim 1, characterized in that: In step (1), the solute of the alginate aqueous solution is sodium alginate, and the concentration is 10-20 g / L.

3. The method for preparing the layered structured injectable adhesive microcarrier according to claim 1, characterized in that: In step (1), the dripping end of the microfluidic device is located under an electric field, and the alginate aqueous solution droplets are formed into a Taylor cone by the action of the electric field; the electric field voltage is 8-14KV, and the flow rate of the alginate aqueous solution dripped by the microfluidic device is 80-120 mL / h.

4. The method for preparing the layered structured injectable adhesive microcarrier according to claim 1, characterized in that: In step (1), the concentration of the calcium chloride aqueous solution is 10-20 g / L; the obtained monodisperse alginate microcarriers are washed with pure water to remove the residual calcium chloride on the surface.

5. The method for preparing the layered structured injectable adhesive microcarrier according to claim 1, characterized in that: In step (1), the diameter of the monodisperse alginate microcarriers obtained is 80-95 μm.

6. The method for preparing the layered structured injectable adhesive microcarrier according to claim 1, characterized in that: In step (2), the concentration of the Tris buffer is 10 mM, the pH value is 8.5, and the concentration of the prepared dopamine solution is 1-4 mg / mL.

7. The method for preparing the layered structured injectable adhesive microcarrier according to claim 1, characterized in that: In step (2), the alginate microcarrier is reacted in the dopamine solution in the dark for more than 10 hours, and the average diameter of the adhesive polydopamine nanoparticles is 100-140 nm.

8. The injectable adhesive microcarrier with a layered structure prepared by the preparation method according to any one of claims 1 to 7, characterized in that: The average diameter of injectable microcarriers is 82-95 μm.

9. Use of the injectable microcarrier according to claim 8 for loading antioxidant drugs, characterized in that: The antioxidant drug is the universal antioxidant alpha-lipoic acid.

10. Use of the injectable microcarrier according to claim 8 for drug delivery to the middle ear.

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