Preparation method of porous hollow glass bead drug carrier and drug carrier

Abstract

The invention relates to the technical field of drug carriers, in particular to a preparation method of a porous hollow glass bead drug carrier and the drug carrier. The preparation method of the porous hollow glass bead drug carrier comprises the following steps: coating the surfaces of hollow glass beads with a composite coating solution, and curing to obtain the hollow glass beads coated with the composite coating, wherein the composite coating solution comprises a resin emulsion and calcium carbonate used as a pore-forming template; then reacting the hollow glass beads coated with the composite coating in an acid solution to dissolve calcium carbonate in the composite coating and retain a resin matrix in the composite coating; and then the hollow glass beads are placed in a hydrofluoric acid solution for etching and pore-forming of the hollow glass beads. By regulating and controlling the adding amount or particle size of calcium carbonate particles in the composite coating solution, the number of holes in the surface of the final microbead can be linearly controlled, quantitative pore forming is achieved, stable release of the medicine is facilitated, and the burst release effect of the medicine is avoided; and meanwhile, the resin is used as an etching mask, so that the mechanical strength is improved.

Description

A method for preparing a porous hollow glass microsphere drug carrier and the drug carrier Technical Field

[0001] This invention relates to the field of drug carrier technology, specifically to a method for preparing a porous hollow glass microsphere drug carrier and the drug carrier itself. Background Technology

[0002] Hollow glass microspheres are considered a highly promising drug carrier due to their hollow structure, high loading capacity, good chemical stability, and excellent biocompatibility. However, the key technological bottleneck in achieving efficient and controllable drug release lies in how to prepare micropores of uniform size and controllable number on their surface.

[0003] Currently, the main methods for creating pores in hollow glass microspheres include chemical etching, laser drilling, and mechanical methods. Laser drilling offers high precision but the equipment is expensive and extremely inefficient, making it unsuitable for large-scale production. Mechanical methods struggle to control the quality and reproducibility of the pores. Chemical etching typically involves immersing an entire batch of microspheres in hydrofluoric acid, controlling the etching time and concentration. While simple, this method results in highly random and uncontrollable pores in terms of number, size, and distribution, leading to significant differences in drug loading and release behavior between different batches and even within the same batch of microspheres, making it difficult to meet the stringent quality uniformity requirements of pharmaceutical formulations. Furthermore, over-etching severely weakens the mechanical strength of the microspheres, making them prone to breakage. This can lead to collapse during subsequent processing and applications, compromising the reliability of the carrier.

[0004] For example, Chinese patent application CN121130164A, published on December 16, 2025, discloses a porous hollow glass microsphere that can release collagen and its application. The process involves etching the hollow glass microspheres in a hydrofluoric acid solution to create a pore structure on the outer wall that connects the outside and the inner cavity of the hollow glass microspheres, thus obtaining porous hollow glass microspheres for impregnating collagen.

[0005] The pores formed by the hollow glass microspheres created by the above-mentioned hydrofluoric acid etching are randomly distributed and vary in number, resulting in poor drug sustained release effect, unstable sustained release, easy drug burst release effect, and long-term etching can lead to low mechanical strength, which is not conducive to the subsequent application of drug carriers. Summary of the Invention

[0006] The first objective of this invention is to provide a method for preparing porous hollow glass microsphere drug carriers, thereby solving the problems of stable sustained release and burst release effects of existing drug carriers.

[0007] The second objective of this invention is to provide a porous hollow glass microsphere drug carrier that solves the problems of stable sustained release and burst release effects of existing drug carriers.

[0008] To solve the above-mentioned technical problems, the technical solution of the preparation method of porous hollow glass microsphere drug carrier of the present invention is as follows: a preparation method of porous hollow glass microsphere drug carrier includes the following steps: coating the surface of hollow glass microspheres with a composite coating liquid and curing it to obtain hollow glass microspheres coated with a composite coating, wherein the composite coating liquid includes a resin emulsion and calcium carbonate used as a pore-forming template; then reacting the hollow glass microspheres coated with the composite coating in an acid solution to dissolve the calcium carbonate in the composite coating while retaining the resin matrix in the composite coating; and then etching the hollow glass microspheres in a hydrofluoric acid solution to form pores.

[0009] This invention improves upon existing technologies by providing a method for preparing porous hollow glass microsphere drug carriers. The method involves coating microspheres with a composite coating solution of resin emulsion and calcium carbonate. Calcium carbonate serves as a pore-forming template. After dissolving the calcium carbonate in acid, a porous resin protective layer is obtained. These pores penetrate the resin protective layer to the surface of the microspheres. By simply adjusting the amount or particle size of calcium carbonate particles in the composite coating solution, the number of pores on the final microsphere surface can be linearly controlled, achieving a breakthrough from "random pore creation" to "quantitative pore formation." The number of pores is a core parameter determining the drug release rate. The drug carrier of this invention enables precise drug release kinetics regulation across a wide range, from rapid release to ultra-long-term sustained release, and effectively suppresses the initial burst release effect. The resin protective layer, acting as an etching mask, further strengthens the framework, significantly improving the overall mechanical strength of the hollow glass microspheres and preventing breakage during production and use. Furthermore, the coating itself can serve as a platform for subsequent functionalization modifications or be modified to acquire environmental responsiveness, thereby developing more intelligent drug delivery systems.

[0010] The preparation method provided by this invention involves coating, acid treatment and other processes that are all mature industrial technologies. The process flow is simple, reproducible and very suitable for large-scale production, thus solving the problem of transforming laboratory technology into industrial technology.

[0011] Preferably, the mass ratio of resin emulsion to calcium carbonate is (10~15):(0.1~1); the viscosity of the resin emulsion is 30~80 mPa·s, or 30~50 mPa·s. Under the above process parameters, a uniform composite coating can be obtained through the coating process. The mass ratio of resin emulsion to calcium carbonate is further preferably 10:(0.1~1).

[0012] Preferably, the mass of resin emulsion corresponding to each 1-3g of hollow glass microspheres is 10-15g. Using this amount allows the composite coating formed by the composite coating solution to have a relatively thin thickness of 1-5μm, which facilitates subsequent acid etching and the formation of micropores at the calcium carbonate sites.

[0013] Preferably, the acid solution is a 0.5-1M hydrochloric acid solution, and the reaction time in the acid solution is 10-20 minutes. Under these conditions, calcium carbonate can be dissolved rapidly without significantly affecting the resin matrix. More preferably, the concentration of the hydrochloric acid solution is 0.5-0.7M, and the reaction time is 10-15 minutes.

[0014] Preferably, the volume fraction of the hydrofluoric acid solution is 1-3%, and the etching time in the hydrofluoric acid solution is 5-10 minutes. The hydrofluoric acid solution can be prepared by mixing concentrated hydrofluoric acid (40-48% by mass) with water. The aforementioned concentrated hydrofluoric acid (40-48% by mass) is a commercially available product. Using this concentration of hydrofluoric acid solution and the processing time can achieve good pore-opening effect and minimize adverse effects on the resin layer.

[0015] Preferably, the hollow glass microspheres have an average particle size of 50-60 μm. Hollow glass microspheres with this average particle size are low in cost and facilitate delivery and drug release as drug carriers.

[0016] Preferably, the resin emulsion is an aqueous polyurethane emulsion. Aqueous polyurethane emulsions have good mechanical properties and good resistance to acid and alkali corrosion, and can maintain the coating structure well during the process.

[0017] Preferably, the thickness of the resin layer in the composite coating is 1-5 μm, and the average particle size of the calcium carbonate is 2-5 μm, wherein the particle size of the calcium carbonate is greater than the thickness of the resin matrix in the composite coating. Calcium carbonate is used as a pore-forming template, that is, the particle size of the calcium carbonate is greater than the thickness of the resin layer in the composite coating. After being treated in an acid solution to dissolve the calcium carbonate, the resin layer has pores extending from the outside of the resin layer to the surface of the hollow glass microspheres.

[0018] The technical solution of the porous hollow glass microsphere drug carrier of the present invention is as follows: a porous hollow glass microsphere drug carrier, comprising hollow glass microspheres and a resin protective layer covering the surface of the hollow glass microspheres, wherein the resin protective layer has pores extending from the outside of the resin protective layer to the surface of the hollow glass microspheres, and the outer wall of the hollow glass microspheres located in the area of ​​the pores has a channel structure that connects the surface and the inner cavity of the hollow glass microspheres.

[0019] This invention provides a porous hollow glass microsphere drug carrier. By coating it with a resin protective layer, the resin protective layer not only serves as an etching mask but also strengthens the framework, significantly improving the overall mechanical strength of the hollow glass microspheres and preventing them from breaking during production and use. Furthermore, by controlling the pore structure and number of pores in the resin protective layer, a wide range of precise drug release kinetics regulation can be achieved, from rapid release to ultra-long-term sustained release. It can also effectively suppress the initial burst release effect. Moreover, the coating itself can serve as a platform for subsequent functionalization modifications or be modified to make it environmentally responsive, thereby developing a more intelligent drug delivery system.

[0020] Preferably, the number of pores on the surface of each hollow glass microsphere is 20 to 400. Quantitative pore creation is achieved by controlling the number of pores.

[0021] Preferably, the thickness of the resin protective layer is 1~5μm. This thickness allows for the effective utilization of the drug loading capacity and the inherent properties of hollow glass microspheres, such as their hollow structure and good biocompatibility. Attached Figure Description

[0022] Figure 1 is a schematic diagram of the composite coating in Embodiment 1 of the present invention; Figure 2 is a schematic diagram of the composite coating in Embodiment 1 of the present invention after calcium carbonate is dissolved; Figure 3 is a schematic diagram of the composite coating in Embodiment 1 of the present invention after calcium carbonate is dissolved and after hydrofluoric acid etching; In the figures: 1, calcium carbonate particles; 2, polyurethane coating layer; 3, hollow glass microspheres. Detailed Implementation

[0023] The technical concept of the preparation method of porous hollow glass microsphere drug carrier provided by the present invention is as follows: Porous hollow glass microspheres can be used as drug carriers. In the prior art, when preparing porous structures on the outer wall of hollow glass microspheres by chemical etching, the number, size and distribution of pores formed are uncontrollable, resulting in poor drug sustained release effect, unstable sustained release, easy drug burst release effect, and excessive etching will seriously weaken the mechanical strength of microspheres.

[0024] This invention linearly controls the number of pores on the surface of the final microspheres by simply adjusting the amount or size of calcium carbonate particles added to the composite coating solution, thereby achieving quantitative pore formation, which is beneficial for stable drug release and avoids drug burst release effects. At the same time, the resin not only serves as an etching mask but also plays a role in reinforcing the skeleton, thereby improving mechanical strength.

[0025] The method for preparing porous hollow glass microsphere drug carriers provided by the present invention includes the following steps: coating the surface of hollow glass microspheres with a composite coating solution and curing it to obtain hollow glass microspheres coated with a composite coating solution. The composite coating solution consists of a resin emulsion with a mass ratio of (10~15):(0.1~1) and calcium carbonate used as a pore-forming template. The mass of the resin emulsion corresponding to each 1~3g of hollow glass microspheres is 10~15g. The thickness of the resin layer in the composite coating solution is smaller than the particle size of the calcium carbonate. Then, the hollow glass microspheres coated with the composite coating solution are reacted in a 0.5~1M acid solution for 10~20min to dissolve the calcium carbonate in the composite coating solution while retaining the resin matrix in the composite coating solution. Finally, the hollow glass microspheres are etched in a 1~3% hydrofluoric acid solution for 5~10min.

[0026] Specifically, the hollow glass microspheres have an average particle size of 50-60 μm; the resin layer in the composite coating has a thickness of 1-5 μm; the calcium carbonate has an average particle size of 2-5 μm; and the resin in the resin emulsion is water-based polyurethane. The resin emulsion is prepared from water and resin.

[0027] Specifically, the number of pores on the surface of each hollow glass microsphere is 20 to 400.

[0028] Specifically, the coating is achieved by coating the surface of hollow glass microspheres with a composite coating liquid using a fluidized bed coating method, a spray drying method, or a dip coating method.

[0029] Specifically, the resin emulsion is preferably an aqueous polyurethane emulsion, and the curing is a drying process.

[0030] Specifically, the viscosity of the resin emulsion is 30~80 mPa·s. In practical use, it can be prepared by diluting commercially available waterborne polyurethane emulsion. Specifically, the waterborne polyurethane resin was purchased from Anhui Anda Huatai AH-1704B-2, with a viscosity of 100~300 mPa·s. After dilution with a certain proportion of water, the viscosity was controlled to be 30~80 mPa·s.

[0031] Based on the aforementioned drug carrier, an active pharmaceutical ingredient can be further loaded to construct a drug delivery system. The structure of this drug delivery system includes the aforementioned porous hollow glass microsphere drug carrier and the active pharmaceutical ingredient filling the pores, channels, and cavities within the porous hollow glass microsphere drug carrier and the inner cavity of the hollow glass microspheres.

[0032] The aforementioned active pharmaceutical ingredients include, but are not limited to, small molecule chemical pharmaceutical ingredients, peptides, proteins, nucleic acids, or growth factors, which can be loaded using a negative pressure impregnation method.

[0033] Taking bovine serum albumin (BSA) loading as an example, the porous hollow glass microsphere drug carrier is immersed in a BSA solution under negative pressure, followed by washing and drying to complete the loading process. For instance, 1g of the above porous hollow glass microsphere drug carrier can be immersed in 25-50mL of BSA solution and treated at -0.095MPa to -0.1MPa for 30min to 2h. The concentration of the BSA solution can be 10-20mg / mL.

[0034] The aforementioned drug delivery system enables a wide range of precise drug release kinetics regulation, from rapid release to ultra-long sustained release, and can effectively suppress the initial burst release effect.

[0035] The embodiments of the present invention will be further described below with reference to specific examples. Unless otherwise specified, the chemical reagents involved in the following examples are all commercially available conventional products.

[0036] I. Preparation Method and Specific Embodiments of the Porous Hollow Glass Microsphere Drug Carrier of the Present Invention Example 1: The porous hollow glass microsphere drug carrier of this embodiment includes hollow glass microspheres and a polyurethane layer coating the surface of the hollow glass microspheres. The polyurethane layer has pores extending from the outside of the polyurethane layer to the surface of the hollow glass microspheres. The outer wall of the hollow glass microspheres located in the area of ​​the pores has a channel structure that connects the surface and the inner cavity of the hollow glass microspheres. The particle size of the hollow glass microspheres is 50 μm, the thickness of the polyurethane layer is 1.5 μm, the average pore size of the pores is 2 μm, and the number of pores on the surface of each hollow glass microsphere is 20-30.

[0037] The preparation method of the porous hollow glass microsphere drug carrier in this embodiment is as follows: 1) Preparation of composite coating: Take 1g of hollow glass microspheres with an average particle size of 50μm and place them in a fluidized bed coating machine. Prepare coating solution: Mix 10g of aqueous polyurethane emulsion (solvent is water, viscosity is 50 mpa•s) with 0.1g of calcium carbonate particles with an average particle size of 2μm and disperse evenly by ultrasonication. Under appropriate fluidizing air and atomizing pressure, spray the coating solution onto the surface of the hollow glass microspheres. After drying, a composite coating is obtained, as shown in Figure 1. The composite coating includes a polyurethane coating layer 2 covering the surface of the hollow glass microspheres 3 and calcium carbonate particles 1 dispersed in the polyurethane coating layer 2. The thickness of the polyurethane coating layer 2 is approximately 1.5μm.

[0038] 2) Preparation of porous resin layer: The hollow glass microspheres coated with the composite coating obtained in step 1) are immersed in 0.5M hydrochloric acid solution and magnetically stirred for 10 minutes to ensure that the calcium carbonate particles 1 are completely dissolved while the aqueous polyurethane coating layer 2 is not dissolved, as shown in Figure 2. Hollow glass microspheres coated with porous polyurethane layer are obtained, which have pores that extend from the outside of the polyurethane layer to the surface of the hollow glass microspheres.

[0039] 3) Etching: After washing the hollow glass microspheres coated with the porous polyurethane layer obtained in step 2) twice with deionized water, immerse them in a 1% (v / v) hydrofluoric acid solution and etch for 5 minutes. This etches a pore structure that connects the surface and inner cavity of the hollow glass microspheres, creating a porous structure where the outer wall of the microspheres is located in the pore area of ​​the porous structure. After etching, wash with a large amount of deionized water until neutral, and freeze-dry to obtain hollow glass microspheres A with a small number (approximately 20-30 per microsphere) of through-pores on the surface, as shown in Figure 3.

[0040] It should be noted that the number of through holes on the surface of hollow glass microspheres obtained under the same parameter conditions as in this embodiment is not the same, and the number of through holes ranges from 20 to 30 per microsphere.

[0041] Example 2: This example of a porous hollow glass microsphere drug carrier includes hollow glass microspheres and a polyurethane layer coating the surface of the hollow glass microspheres. The polyurethane layer has pores extending from the outside of the polyurethane layer to the surface of the hollow glass microspheres. The outer wall of the hollow glass microspheres, located in the region of the pores, has a channel structure that connects the surface and the inner cavity of the hollow glass microspheres. The particle size of the hollow glass microspheres is 50 μm, the thickness of the polyurethane layer is 1.5 μm, the average pore size is 2 μm, and the number of pores on the surface of each hollow glass microsphere is 100-150.

[0042] The preparation method of the porous hollow glass microsphere drug carrier in this embodiment is basically the same as that in Example 1, except that the amount of calcium carbonate particles added to the coating solution is 0.5g, resulting in hollow glass microspheres B with a moderate number (about 100-150 per microsphere) of through pores on the surface.

[0043] Example 3: This example of a porous hollow glass microsphere drug carrier includes hollow glass microspheres and a polyurethane layer coating the surface of the hollow glass microspheres. The polyurethane layer has pores extending from the outside of the polyurethane layer to the surface of the hollow glass microspheres. The outer wall of the hollow glass microspheres, located in the region of the pores, has a channel structure that connects the surface and the inner cavity of the hollow glass microspheres. The particle size of the hollow glass microspheres is 50 μm, the thickness of the polyurethane layer is 1.5 μm, the average pore size is 2 μm, and the number of pores on the surface of each hollow glass microsphere is 300-400.

[0044] The preparation method of the porous hollow glass microsphere drug carrier in this embodiment is basically the same as that in Example 1, except that the amount of calcium carbonate particles added to the coating solution is 1.0g, and hollow glass microspheres C with a large number (about 300-400 per microsphere) of through pores on the surface are obtained.

[0045] II. Experimental Example: The porous hollow glass microsphere drug carrier obtained by the traditional etching method is used as a comparative example. The specific preparation method is as follows: 1g of hollow glass microspheres are directly immersed in 1% (v / v) hydrofluoric acid solution and etched for 5 minutes to obtain microspheres D with randomly distributed pores on the surface and varying numbers.

[0046] Hollow glass microspheres A, B, C, and D, representing the examples, comparative examples, and conventional drug carriers, were loaded with bovine serum albumin solution of the same concentration under vacuum conditions as model drugs. Their in vitro release behavior was then investigated in PBS buffer. The loading method for the active pharmaceutical ingredient was consistent across all drug carriers: the drug carriers were immersed in 25 mL of 10 mg / mL bovine serum albumin solution under a vacuum of -0.095 MPa for 30 min.

[0047] The drug loading test method adopts the indirect method, which measures the difference in drug solution concentration before and after drug loading. The specific steps are as follows: 1) Drug loading: Immerse a blank carrier of known mass into a drug solution of known concentration and volume, and complete the drug loading by vacuum assistance.

[0048] 2) Separation and washing: After drug loading is completed, the drug-loaded microbeads are separated by centrifugation, and the supernatant and washing solution are collected.

[0049] 3) Concentration determination: The concentration of the remaining drug in the supernatant was determined using high performance liquid chromatography.

[0050] 4) Finally, the drug loading is calculated.

[0051] The release test method is the dialysis bag method, and the specific steps are as follows: ① Establish the release system: Weigh the drug-loaded microbeads, disperse them in a small amount of release medium, and put them into a dialysis bag.

[0052] ② Start the release: Place the dialysis bag in a larger volume of release medium and shake it at a low speed.

[0053] ③ Timed sampling: Remove a certain volume of the release medium at a preset time point and immediately replenish it with an isothermal and equal volume of fresh medium.

[0054] ④ Concentration analysis and calculation: The drug concentration in each sample was determined using HPLC, and the cumulative release was calculated.

[0055] The in vitro release performance test results of the model drugs for each drug carrier are shown in Table 1. In Table 1, both traditional mesoporous silica and PLGA microspheres are commercially available products. The traditional mesoporous silica was purchased from Hangzhou Jikang New Materials Co., Ltd., with a pore size of 10~50nm; the PLGA microspheres were purchased from Beyotime, with a monomer ratio of 1:1.

[0056] Table 1. Performance comparison of the embodiments of the present invention and conventional drug carriers

[0057] As shown in Table 1: 1) Ultra-high drug loading capacity: After hydrochloric acid dissolves the calcium carbonate, large-sized "drug storage chambers" (the space originally occupied by calcium carbonate) are formed on the surface and shallow layer of the hollow glass microspheres. Subsequent hydrofluoric acid etching creates a network of interconnected micron / nanoscale pores between the chambers and between the chambers and the outside world. This multi-level structure of "large chambers + fine channels" provides far more physical space than traditional mesoporous materials (which only have nanopores), greatly improving the loading capacity.

[0058] 2) Ultra-long and stable release time: The drug is mainly stored in the "large chamber" inside the microbeads. During release, the drug must diffuse through a long, tortuous network of small-pore "connecting channels." This process creates extremely strong diffusion resistance, greatly slowing down the release rate. By adjusting the size of the calcium carbonate particles (controlling the volume of the drug storage chamber) and the concentration / time of hydrofluoric acid (controlling the size and length of the connecting channels), the release kinetics can be precisely controlled, achieving customized sustained release from days to weeks.

[0059] 3) Extremely low burst release effect: In traditional porous drug carriers, drugs adsorbed on the outer surface of the carrier and at the entrance of the main pores can cause severe initial burst release. In this invention, the outer surface of the carrier is completely covered by a polyurethane curing layer, and hydrofluoric acid only corrodes the uncovered "blank spots" to form release channels. Therefore, almost all the drug is sealed inside, with no drug adsorbed on the surface, thus fundamentally eliminating burst release.

[0060] 4) Excellent release concentration stability: The "drug reservoir" is equivalent to a stable drug reservoir, continuously and uniformly delivering the drug outward through the "rate-limiting channel". As long as the drug concentration in the reservoir does not change significantly, the release rate can remain relatively constant (close to zero-order release), which is crucial for maintaining stable blood drug concentration and reducing side effects.

[0061] In summary, this invention enables precise control of the number of pores on the surface of the final glass microspheres by controlling the amount of calcium carbonate particles incorporated, thereby achieving precise management of the drug release rate. The hollow glass microspheres prepared by this method have advantages such as controllable pore structure, low drug burst release effect, high mechanical strength, and good reproducibility, making them suitable for biomedical fields such as long-acting sustained-release injections and targeted drug delivery systems.

[0062] Finally, it should be noted that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing a porous hollow glass microsphere drug carrier, characterized in that, Includes the following steps: A composite coating liquid is coated on the surface of hollow glass microspheres and cured to obtain hollow glass microspheres coated with a composite coating. The composite coating liquid includes a resin emulsion and calcium carbonate used as a pore-forming template. Then, the hollow glass microspheres coated with the composite coating are reacted in an acid solution to dissolve the calcium carbonate in the composite coating while the resin matrix in the composite coating is retained. Hollow glass microspheres are then etched into pores in a hydrofluoric acid solution.

2. The method for preparing porous hollow glass microsphere drug carriers as described in claim 1, characterized in that, The mass ratio of resin emulsion to calcium carbonate is (10~15):(0.1~1); the viscosity of the resin emulsion is 30~80 mPa•s, or 30~50 mPa•s.

3. The method for preparing porous hollow glass microsphere drug carriers as described in claim 1 or 2, characterized in that, The mass of resin emulsion corresponding to each 1-3g of hollow glass microspheres is 10-15g.

4. The method for preparing porous hollow glass microsphere drug carriers as described in claim 1, characterized in that, The acid solution is a 0.5-1M hydrochloric acid solution, and the reaction time in the acid solution is 10-20 minutes.

5. The method for preparing porous hollow glass microsphere drug carriers as described in claim 1, characterized in that, The volume fraction of the hydrofluoric acid solution is 1-3%, and the etching time in the hydrofluoric acid solution is 5-10 min.

6. The method for preparing porous hollow glass microsphere drug carriers as described in claim 1, characterized in that, The hollow glass microspheres have an average particle size of 50~60μm.

7. The method for preparing porous hollow glass microsphere drug carriers as described in claim 1, characterized in that, The resin emulsion is an aqueous polyurethane emulsion.

8. The method for preparing porous hollow glass microsphere drug carriers as described in claim 1 or 6, characterized in that, The thickness of the resin layer in the composite coating is 1~5μm, and the average particle size of the calcium carbonate is 2~5μm. The particle size of the calcium carbonate is greater than the thickness of the resin matrix in the composite coating.

9. A porous hollow glass microsphere drug carrier, characterized in that, It includes hollow glass microspheres and a resin protective layer covering the surface of the hollow glass microspheres. The resin protective layer has pores extending from the outside of the resin protective layer to the surface of the hollow glass microspheres. The outer wall of the hollow glass microspheres located in the area of ​​the pores has a channel structure that connects the surface and the inner cavity of the hollow glass microspheres.

10. The porous hollow glass microsphere drug carrier as described in claim 9, characterized in that, The thickness of the resin protective layer is 1~5μm.

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