Strontium ion / zoledronic acid loaded composite gel and preparation method thereof

Abstract

The invention is applicable to the technical field of biomedical materials, and provides strontium ion / zoledronic acid loaded composite gel and a preparation method thereof, and the preparation method comprises the following steps: preparing sulfydryl modified sodium hyaluronate and double bond modified carboxymethyl chitosan; the preparation method comprises the following steps: sequentially preparing mesoporous silica microspheres doped with strontium ions, sulfhydrylated mesoporous silica microspheres doped with strontium ions, and sulfhydrylated mesoporous silica microspheres loaded with zoledronic acid doped with strontium ions; the preparation method comprises the following steps: respectively dissolving sulfydryl-modified sodium hyaluronate and double-bond-modified carboxymethyl chitosan in deionized water, stirring and mixing with zoledronic acid-loaded sulfhydrylated strontium ion-doped mesoporous silica microspheres, adding a photoinitiator, and irradiating under ultraviolet light. The composite gel prepared by the invention integrates mechanical support, biocompatibility, intelligent drug release and synergistic osteogenesis / vascularization promotion, and can be applied to preparation of high-performance osteoporotic bone defect repair materials.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of biomedical materials, and particularly relates to a composite gel loaded with strontium ions / zoledronic acid and a preparation method thereof. BACKGROUND

[0002] Osteoporosis is a systemic bone disease characterized by bone mass loss and bone microstructure destruction, which significantly increases the risk of bone defects in patients. The repair of such osteoporotic bone defects faces severe challenges: on the one hand, the local bone formation ability of patients is severely low, and the osteoblast activity is insufficient; on the other hand, the bone defect area is often accompanied by poor vascularization, and the transportation of nutrients and repair cells is blocked, further delaying the healing process. Traditional bone defect repair materials often fail to meet the special needs of such pathological microenvironments: they either lack effective biological activity to stimulate osteogenesis and vascularization, or cannot provide suitable mechanical support and degradation performance.

[0003] In recent years, the research of functional bone repair materials has focused on the introduction of bioactive factors. Strontium ions have been proven to have a dual promotion effect: they can significantly enhance the differentiation and mineralization ability of osteoblasts, and effectively stimulate endothelial cell proliferation and angiogenesis; as a strong bisphosphonate, zoledronic acid can effectively inhibit the activity of osteoclasts, preventing pathological bone resorption and creating favorable conditions for bone regeneration. In theory, the synergistic effect of strontium ions and zoledronic acid is expected to provide a more optimized treatment for osteoporotic bone defects, however, most studies focus on a single function, or only pay attention to drug delivery itself, lacking an effective integration strategy for active factor delivery and scaffold materials with suitable mechanical properties, which makes it difficult for the material to fill the defect while providing continuous biological stimulation and stable physical support for bone healing. SUMMARY

[0004] The purpose of the embodiments of the present application is to provide a preparation method of a composite gel loaded with strontium ions / zoledronic acid, aiming to solve the problems raised in the background art.

[0005] The embodiments of the present application are implemented in the following way: a preparation method of a composite gel loaded with strontium ions / zoledronic acid, comprising the following steps: Sodium hyaluronate is dissolved in deionized water to obtain a sodium hyaluronate solution, and solid cysteamine hydrochloride is added to obtain thiol-modified sodium hyaluronate; Carboxymethyl chitosan is dissolved in deionized water to obtain a carboxymethyl chitosan solution, and liquid glycidyl methacrylate is added to obtain double bond-modified carboxymethyl chitosan; Cetyltrimethylammonium bromide and ammonia water are dissolved in deionized water to obtain a mixed solution, and tetraethyl orthosilicate and strontium chloride hexahydrate are added to obtain mesoporous silica microspheres doped with strontium ions; dispersing the strontium ion-doped mesoporous silica microspheres into a toluene solution, adding 3-mercaptopropyl trimethoxysilane to obtain mercapto-modified strontium ion-doped mesoporous silica microspheres; dispersing the mercapto-modified strontium ion-doped mesoporous silica microspheres into deionized water, adding solid zoledronic acid to obtain zoledronic acid-loaded mercapto-modified strontium ion-doped mesoporous silica microspheres; respectively, to obtain precursor solutions A and B; mixing the precursor solutions A, B and the zoledronic acid-loaded mercapto-modified strontium ion-doped mesoporous silica microspheres by stirring, adding a photoinitiator, and irradiating under ultraviolet light to form a strontium ion / zoledronic acid-loaded composite gel.

[0006] Another purpose of the embodiments of the present application is to provide a strontium ion / zoledronic acid-loaded composite gel prepared by the above preparation method.

[0007] Another purpose of the embodiments of the present application is to provide an application of the strontium ion / zoledronic acid-loaded composite gel in the preparation of bone defect repair materials.

[0008] The strontium ion / zoledronic acid-loaded composite gel provided by the embodiments of the present application integrates mechanical support, biocompatibility, intelligent drug release, and synergistic osteogenesis and angiogenesis, and can be applied in the preparation of high-performance osteoporotic bone defect repair materials, and creatively solves the key bottleneck of insufficient comprehensive performance of repair materials. The embodiments of the present application utilize the thiol-dual bond click chemistry reaction between the mercapto-modified sodium hyaluronate and the dual bond-modified carboxymethyl chitosan to realize rapid and stable crosslinking under 365nm ultraviolet light. The light-triggered crosslinking strategy overcomes the defects of uncontrollable traditional chemical crosslinking and slow biological crosslinking, and can accurately form in situ, thereby providing persistent mechanical support for bone defect filling. The embodiments of the present application creatively prepare strontium ion-doped mesoporous silica microspheres. The introduction of strontium ions is not a simple addition, but realizes the synergistic effect of double biological effects: on the one hand, the sustained release of strontium ions effectively stimulates the activity of osteoblasts, significantly enhances the osteoinductivity of the material; on the other hand, it can simultaneously and significantly promote the neovascularization of the bone defect area; this "osteogenesis-angiogenesis coupling" property is crucial for solving the problems of low bone formation ability and insufficient local blood supply commonly existing in osteoporosis patients, thereby accelerating the bone healing process. The embodiment of the present application creatively prepares the mesoporous silica microspheres loaded with zoledronic acid and doped with strontium ions, and through the synergistic effect of the thiol modification and the mesoporous silica structure, the controllable slow release of the strong anti-osteoporosis drug zoledronic acid can be realized. Not only the potential side effects caused by drug burst release can be effectively avoided, and the drug safety can be ensured, but also the local effective drug concentration can be maintained for a long time, and the pathological microenvironment of osteoporotic bone defect is targeted, so that the repair effect of osteoporotic bone defect is improved. The composite gel prepared in the embodiment of the present application can realize the double regulation of promoting osteogenesis, that is, zoledronic acid inhibits osteoclasts, and strontium ions continuously promote osteoblast differentiation, forming a dynamic balance of 'anti-absorption-promotion', which will be significantly better than the treatment strategy of a single drug. BRIEF DESCRIPTION OF DRAWINGS

[0009] Figure 1 A flow chart of a preparation method of a composite gel loaded with strontium ions / zoledronic acid is provided for the embodiment of the present application. Figure 2 A Fourier infrared spectrum of the composite gel material obtained in the comparative example 1 of the present application; HA is sodium hyaluronate; HA-SH is thiol-modified sodium hyaluronate; CMCS is carboxymethyl chitosan; CMCS-GMA is double bond modified carboxymethyl chitosan; HSCG is a composite gel generated by the reaction of HA-SH and CMCS-GMA; Figure 3 A scanning electron microscope image of the composite gel loaded with strontium ions / zoledronic acid obtained in the embodiment 1 of the present application; Figure 4 A transmission electron microscope image of the mesoporous silica microspheres loaded with zoledronic acid and doped with strontium ions obtained in the embodiment 1 of the present application; Figure 5 Particle size distribution diagrams of the microspheres obtained in steps S4 and S5 in the embodiment 1 of the present application, respectively; Figure 6 Modulus-amplitude scanning diagrams of the composite gels obtained in the embodiments 1-3 and the comparative example 1 of the present application; Figure 7 Stress-strain curves of the compressive strength of the composite gels obtained in the embodiments 1-3 and the comparative example 1 of the present application; Figure 8 A comparison diagram of the results of the BMSC cell proliferation experiment of the composite gels obtained in the embodiments 1-3 and the comparative example 1 of the present application; Figure 9 A comparison diagram of the results of the HUVEC cell angiogenesis experiment of the composite gels obtained in the embodiments 1-3 and the comparative example 1 of the present application. DETAILED DESCRIPTION

[0010] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0011] The specific implementation of the present invention is described in detail below with reference to specific embodiments.

[0012] Example 1: A composite gel loaded with strontium ions / zoledronic acid, the preparation method of which is as follows Figure 1 As shown, the specific steps include: Step S1, dissolving 1 g of sodium hyaluronate (HA) with a molecular weight of 1.0-1.8 MDa in 100 mL of deionized water, and magnetically stirring until completely dissolved to obtain a sodium hyaluronate solution; adding 955 mg of 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride and 575 mg of N-hydroxysuccinimide in sequence to the obtained solution, and magnetically stirring until completely dissolved; adding 283 mg of cysteamine hydrochloride to the above-obtained mixed solution, and magnetically stirring in a dark environment at 25° C. for 24 hours; placing the obtained mixed solution into a dialysis bag, dialyzing with deionized water for 7 days, and freeze-drying at -80° C. for 3 days to obtain thiol-modified sodium hyaluronate (HA-SH); Step S2, dissolving 1 g of carboxymethyl chitosan (CMCS) in 100 mL of deionized water, and magnetically stirring until completely dissolved to obtain a carboxymethyl chitosan solution; adding 1 mL of glycidyl methacrylate to the obtained solution, and magnetically stirring until uniformly mixed, and magnetically stirring at 25° C. in a dark environment for 24 hours; the obtained mixed solution is placed in a dialysis bag, dialyzed with deionized water for 7 days, and freeze-dried at -80° C. for 3 days to obtain double-bond modified carboxymethyl chitosan (CMCS-GMA); Step S3, 0.728g of hexadecyltrimethylammonium bromide and 2mL of ammonia water were sequentially added to 100mL of deionized water, and magnetically stirred until completely dissolved (magnetically stirred at 40°C for 1h); 4.167g of tetraethyl orthosilicate and 0.34g of strontium chloride hexahydrate were sequentially added to the obtained mixed solution, and magnetically stirred until uniformly mixed (magnetically stirred at 40°C for 5h); the organic solvent was removed, and the mixture was centrifuged at 10000rpm for 10min. After washing three times with ethanol and deionized water alternately, the nanoparticles were collected by centrifugation, placed in a vacuum drying oven, and vacuum dried at 60°C for 24h; the obtained product was placed in a tubular heating furnace, heated to 700°C at a heating rate of 2°C / min, and calcined for 3h to remove excess hexadecyltrimethylammonium bromide to obtain mesoporous silica microspheres doped with strontium ions (MSN / Sr); Step S4, 150 mg of dried mesoporous silica microspheres doped with strontium ions were placed in a vacuum oven, activated at 80°C for 12 h; 150 mg of activated mesoporous silica microspheres doped with strontium ions were dispersed in 30 mL of toluene, and stirred magnetically until the particles were uniformly distributed; 0.2 mL of 3-mercaptopropyl trimethoxysilane was slowly added to the above solution, and refluxed at 110°C for 24 h under condensation; the organic solvent was removed, and the nanoparticles were collected by centrifugation at 10,000 rpm for 10 min, washed with ethanol and deionized water alternately for three times, and then dried in a vacuum drying oven at 60°C for 24 h, to obtain mercapto-modified mesoporous silica microspheres doped with strontium ions; Step S5, 500 mg of dried mercapto-modified mesoporous silica microspheres doped with strontium ions were dispersed in 200 mL of deionized water, and stirred magnetically until the particles were uniformly distributed; 200 mg of zoledronic acid was added to the above mixed solution, and stirred magnetically until completely dissolved, and then stirred magnetically at 25°C for 6 h; the solution was removed, and the nanoparticles were collected by centrifugation at 10,000 rpm for 10 min, washed with water and ethanol alternately for three times, and then freeze-dried at -80°C for 3 days, to obtain mercapto-modified mesoporous silica microspheres doped with strontium ions loaded with zoledronic acid (MSN / Sr / ZA); Step S6, the mercapto-modified sodium hyaluronate obtained in step S1 and the double bond-modified carboxymethyl chitosan obtained in step S2 were separately dissolved in deionized water to obtain precursor solutions A and B; the precursor solutions A, B and the microspheres obtained in step S5 were thoroughly stirred and mixed, and a photoinitiator was added, and then irradiated under ultraviolet light; the volume ratio of the precursor solutions A and B was 1:4, the concentration of the microspheres was 0.1% (w / v), the wavelength of the ultraviolet light was 365 nm, 0.5% (w / v) of the photoinitiator was added, and the irradiation time was 1 min, to obtain a strontium ion / zoledronic acid-loaded composite gel (named as HSCG@MSN / Sr / ZA).

[0013] Example 2, a strontium ion-loaded composite gel, the preparation method comprising the following steps: Steps S1-S4: the same as steps S1-S4 in Example 1; Step S5, the mercapto-modified sodium hyaluronate obtained in step S1 and the double bond-modified carboxymethyl chitosan obtained in step S2 were separately dissolved in deionized water to obtain precursor solutions A and B; the precursor solutions A, B and the microspheres obtained in step S4 were thoroughly stirred and mixed, and a photoinitiator was added, and then irradiated under ultraviolet light; the volume ratio of the precursor solutions A and B was 1:4, the concentration of the microspheres was 0.1% (w / v), the wavelength of the ultraviolet light was 365 nm, 0.5% (w / v) of the photoinitiator was added, and the irradiation time was 1 min, to obtain a strontium ion-loaded carboxymethyl chitosan photo-crosslinked sodium hyaluronate composite gel (named as HSCG@MSN / Sr).

[0014] Example 3, a zolendronate-loaded composite gel, the preparation method comprising the following steps: Steps S1-S2: same as steps S1-S2 in Example 1; Step S3, the thiol-modified sodium hyaluronate obtained in step S1 and the double bond-modified carboxymethyl chitosan obtained in step S2 are separately dissolved in deionized water to obtain precursor solutions A and B; the precursor solutions A, B and zolendronate are fully stirred and mixed, a photoinitiator is added, and irradiation is performed under ultraviolet light; the volume ratio of the mixed precursor solutions A and B is 1:4, the concentration of zolendronate is 0.1% (w / v), 0.5% (w / v) of the photoinitiator is added, the wavelength of the ultraviolet light is 365 nm, and the irradiation time is 1 min, to obtain a zolendronate-loaded carboxymethyl chitosan photo-crosslinked sodium hyaluronate composite gel (named as HSCG@ZA).

[0015] Example 4, compared with Example 1, the difference lies in that the volume ratio of the mixed precursor solutions A and B in step S6 is adjusted to 1:3.

[0016] Example 5, compared with Example 1, the difference lies in that the volume ratio of the mixed precursor solutions A and B in step S6 is adjusted to 1:2.

[0017] Comparative Example 1, a gel, the preparation method specifically comprising the following steps: Steps S1-S2, same as steps S1-S2 in Example 1; Step S3, the thiol-modified sodium hyaluronate obtained in step S1 and the double bond-modified carboxymethyl chitosan obtained in step S2 are separately dissolved in deionized water to obtain precursor solutions A and B; the precursor solutions A, B are fully stirred and mixed, a photoinitiator is added, and irradiation is performed under ultraviolet light; the volume ratio of the mixed precursor solutions A and B is 1:4; 0.5% (w / v) of the photoinitiator is added, the wavelength of the ultraviolet light is 365 nm, and the irradiation time is 1 min, to obtain a carboxymethyl chitosan photo-crosslinked sodium hyaluronate composite gel (named as HSCG).

[0018] Performance analysis and test: The gel obtained in Comparative Example 1 is subjected to a total reflection infrared spectrum test, and the results are shown in Figure 2 The figure shows that HA is sodium hyaluronate; HA-SH is thiol-modified sodium hyaluronate; CMCS is carboxymethyl chitosan; CMCS-GMA is double bond-modified carboxymethyl chitosan; HSCG is a composite gel generated by the reaction of HA-SH and CMCS-GMA; it can be seen that the characteristic peak of -HN-CO- at 1546 cm -1 is more obvious after the thiolation reaction; the characteristic peak of -C=O- at 1715 cm -1 appears in the infrared spectrum of the double bond-modified carboxymethyl chitosan; 765 cm-1 The characteristic peak of -C-S- appears in the infrared spectrum of the HSCG composite gel, which confirms the successful preparation of the composite gel HSCG.

[0019] The strontium ion / zoledronic acid loaded composite gel obtained in Example 1 was subjected to field emission electron microscope scanning, and the results are shown in Figure 3 It can be seen that the gel presents an irregular porous microstructure, and obvious microspheres can be observed in the pores.

[0020] The thiol-modified strontium ion-doped mesoporous silica microspheres loaded with zoledronic acid obtained in Example 1 were subjected to field emission transmission electron microscope scanning, and the results are shown in Figure 4 It can be seen that the modified mesoporous silica microspheres still maintain the mesoporous structure and are still nanoscale in size.

[0021] The particle sizes of the microspheres obtained in steps S4 and S5 of Example 1 were analyzed, and the results are shown in Figure 5 It can be seen that the average particle size of the thiol-modified strontium ion-doped mesoporous silica microspheres is 650.0 nm, and the average particle size of the thiol-modified strontium ion-doped mesoporous silica microspheres loaded with zoledronic acid is 664.9 nm. Compared with the average particle size of the thiol-modified strontium ion-doped mesoporous silica microspheres, the size of the drug-loaded microspheres does not change significantly, and the original structure of the thiol-modified strontium ion-doped mesoporous silica microspheres is maintained.

[0022] The strontium ion / zoledronic acid loaded composite gel obtained in Examples 1-3 and the composite gel of Comparative Example 1 were subjected to modulus-vibration scanning test, and the results are shown in Figure 6 It can be seen that the addition of zoledronic acid does not change the storage modulus of the composite gel, but the incorporation of nanoparticles and modified nanoparticles relatively greatly improves the storage modulus of the HSCG@MSN / Sr / ZA and HSCG@MSN / Sr composite gels.

[0023] The strontium ion / zoledronic acid loaded composite gel obtained in Examples 1-3 and the composite gel of Comparative Example 1 were subjected to compression strength stress-strain curve test, and the results are shown in Figure 7 It can be seen that the addition of zoledronic acid does not change the compression modulus of the composite gel, but the incorporation of nanoparticles and modified nanoparticles relatively greatly improves the compression modulus of the HSCG@MSN / Sr / ZA and HSCG@MSN / Sr composite gels, which is almost doubled compared with the pure gel group.

[0024] The cell proliferation activity of the composite gels of Examples 1-3 and Comparative Example 1 was evaluated by in vitro culture experiments using rat bone marrow mesenchymal stem cells (BMSC, Beijing Weitong Lihua Experimental Animal Technology Co., Ltd.), and the proliferation of cells in the composite gels was detected using a Cell Counting Kit reagent, according to the following specific operation method: the sterilized samples were placed in a 48-well culture plate, 1x10 4 cell / mL cell suspension was added to each well; the cell culture plate was placed in a cell culture incubator with 5% CO2saturated humidity at 37°C, and the culture medium was changed every 2-3 days; after the cells were cultured for 1, 4 and 7 days, the original culture medium was removed, 200-400 μL of new culture medium containing 10% CKK-8 solution was added, and the culture plate was placed in the incubator for 1-4 h; 100 μL of the culture medium was taken from each well and placed in a 96-well plate; the absorbance value of each well at 450 nm wavelength was measured using an enzyme-labeled instrument (iMark, Bio-Rad, USA); the results are compared as shown in Figure 8 It can be seen from the comparison that the cell proliferation of the HSCG@MSN / Sr composite gel increased compared with the pure composite gel group due to the addition of strontium ion nanoparticles; the cell activity and proliferation of the HSCG@MSN / Sr / ZA group were the best among the four composite gels compared with the HSCG@MSN / Sr group due to the loading of zoledronic acid.

[0025] The endothelial cell angiogenesis ability of the composite gels of Examples 1-3 and Comparative Example 1 was evaluated by in vitro angiogenesis experiments using human umbilical vein endothelial cells (HUVEC, Cell Resource Center of Institute of Basic Medicine, Chinese Academy of Medical Sciences), and the angiogenesis ability of various materials was tested using Matrigel, according to the following specific operation method: the sterilized samples were placed in a 48-well plate, and 1 mL of DMEM medium containing 3% serum was added to each sample well according to the proportion of material surface area / culture medium = 1.25 cm 2 / mL, and the plate was incubated in the incubator for 24 h, and the culture medium was collected as the sample leaching liquid; the Matrigel was evenly coated in a 24-well plate at 4°C, and the plate was placed in the incubator for 40 min; the sample leaching liquid was used to prepare a cell suspension at a density of 6x10 4 cell / mL, and 500 μL of the cell suspension was added to the Matrigel-coated sample well, and the plate was incubated in the incubator; after 6 h, the images of 6 randomly collected regions in each group were observed under a microscope for data statistics; the comparison chart of the results is as shown in Figure 9As shown, it can be seen that compared with the pure gel group, the number of blood vessels formed by HUVEC cells cultured in the leaching solution of the composite gel group loaded with zoledronic acid (HSCG@ZA) is increased; the number of blood vessel nodes formed by HUVEC cells in the HSCG@MSN / Sr composite gel group is more due to the addition of strontium ion nanoparticles; the number of blood vessels formed by HSCG@MSN / Sr / ZA composite gel is more dense and continuous compared with the HSCG@MSN / Sr composite gel due to the loading of zoledronic acid, and the blood vessel forming ability of endothelial cells is improved.

[0026] The above merely describes preferred embodiments of the present application and is not used to limit the present application, and any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A method for preparing a composite gel loaded with strontium ions / zoledronic acid, characterized in that: The following steps are involved: Dissolving sodium hyaluronate in deionized water to obtain a sodium hyaluronate solution, and adding solid cysteamine hydrochloride to obtain thiol-modified sodium hyaluronate; dissolving carboxymethyl chitosan in deionized water to obtain a carboxymethyl chitosan solution, and adding liquid glycidyl methacrylate to obtain double-bond modified carboxymethyl chitosan; Dissolving hexadecyltrimethylammonium bromide and ammonia water in deionized water to obtain a mixed solution, adding tetraethyl orthosilicate and strontium chloride hexahydrate to obtain mesoporous silica microspheres doped with strontium ions; Dispersing the strontium ion-doped mesoporous silica microspheres into a toluene solution, and adding 3-mercaptopropyltrimethoxysilane to obtain mercaptolated strontium ion-doped mesoporous silica microspheres; Dispersing the thiolated strontium ion-doped mesoporous silica microspheres in deionized water, and adding solid zoledronic acid to obtain zoledronic acid-loaded thiolated strontium ion-doped mesoporous silica microspheres; Thiol-modified sodium hyaluronate and double-bond-modified carboxymethyl chitosan are dissolved in deionized water to obtain precursor solutions A and B, respectively. The precursor solutions A and B are thoroughly stirred and mixed with thiol-modified strontium ion-doped mesoporous silica microspheres loaded with zoledronic acid, a photoinitiator is added, and the mixture is irradiated under ultraviolet light to form a strontium ion / zoledronic acid-loaded composite gel.

2. The preparation method according to claim 1, characterized in that The step of dissolving sodium hyaluronate in deionized water to obtain a sodium hyaluronate solution, and adding solid cysteamine hydrochloride to obtain thiol-modified sodium hyaluronate specifically comprises: Sodium hyaluronate with a molecular weight of 1.0-1.8 MDa is dissolved in deionized water and magnetically stirred until completely dissolved to obtain a sodium hyaluronate solution. 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride and N-hydroxysuccinimide are sequentially added to the solution and magnetically stirred until completely dissolved. Cysteamine hydrochloride is added to the resulting mixed solution and magnetically stirred. The resulting mixed solution is dialyzed and freeze-dried to obtain thiol-modified sodium hyaluronate.

3. The preparation method according to claim 1, characterized in that The step of dissolving carboxymethyl chitosan in deionized water to obtain a carboxymethyl chitosan solution, and adding liquid glycidyl methacrylate to obtain double-bond modified carboxymethyl chitosan specifically comprises: The carboxymethyl chitosan is dissolved in deionized water and magnetically stirred until completely dissolved to obtain a carboxymethyl chitosan solution; glycidyl methacrylate is added to the obtained solution and magnetically stirred until uniformly mixed; the obtained mixed solution is dialyzed and freeze-dried to obtain double-bond modified carboxymethyl chitosan.

4. The preparation method according to claim 1, characterized in that The step of dissolving hexadecyltrimethylammonium bromide and ammonia water in deionized water to obtain a mixed solution, and adding tetraethyl orthosilicate and strontium chloride hexahydrate to obtain mesoporous silica microspheres doped with strontium ions specifically includes: Hexadecyltrimethylammonium bromide and ammonia water were sequentially added into deionized water and magnetically stirred until completely dissolved to obtain a mixed solution; Tetraethyl orthosilicate and strontium chloride hexahydrate are sequentially added to the mixed solution and magnetically stirred until the mixture is uniformly mixed; the organic solvent is removed, the mixture is centrifuged, and the mixture is alternately washed with ethanol and deionized water, the nanoparticles are collected by centrifugation, and vacuum dried; the resulting product is then placed in a tubular heating furnace for heating and calcination to remove excess hexadecyltrimethylammonium bromide, thereby obtaining mesoporous silica microspheres doped with strontium ions.

5. The preparation method according to claim 1, characterized in that The step of dispersing the strontium ion-doped mesoporous silica microspheres into a toluene solution and adding 3-mercaptopropyltrimethoxysilane to obtain mercaptolated strontium ion-doped mesoporous silica microspheres specifically comprises: The method comprises the following steps: activating mesoporous silica microspheres doped with strontium ions; dispersing the activated mesoporous silica microspheres doped with strontium ions in toluene, magnetically stirring the activated mesoporous silica microspheres doped with strontium ions until the particles are evenly distributed, adding 3-mercaptopropyltrimethoxysilane, and condensing and refluxing the mixture; removing the organic solvent, centrifuging the mixture, washing the mixture alternately with ethanol and deionized water, collecting the nanoparticles by centrifugation, and vacuum drying the nanoparticles to obtain mercaptolated mesoporous silica microspheres doped with strontium ions.

6. The preparation method according to claim 1, characterized in that The step of dispersing the thiolated mesoporous silica microspheres doped with strontium ions in deionized water and adding solid zoledronic acid to obtain the thiolated mesoporous silica microspheres doped with strontium ions loaded with zoledronic acid specifically comprises: The thiolated mesoporous silica microspheres doped with strontium ions are dispersed in deionized water and magnetically stirred until the particles are evenly distributed; zoledronic acid is added and magnetically stirred until it is completely dissolved; the solution is removed by centrifugation, and the mixture is alternately washed with water and ethanol. The nanoparticles are collected by centrifugation and freeze-dried to obtain thiolated mesoporous silica microspheres doped with strontium ions loaded with zoledronic acid.

7. The preparation method according to claim 1, characterized in that In the step of thoroughly stirring and mixing precursor solutions A and B and thiolated strontium ion-doped mesoporous silica microspheres loaded with zoledronic acid, adding a photoinitiator, and irradiating under ultraviolet light to form a composite gel loaded with strontium ions / zoledronic acid, the volume ratio of the precursor solution A to the precursor solution B is 1:2-4, the concentration of the thiolated strontium ion-doped mesoporous silica microspheres loaded with zoledronic acid is 0.1-0.5% w / v, and the concentration of the photoinitiator is 0.45-0.55% w / v.

8. A composite gel loaded with strontium ions / zoledronic acid, characterized in that: The invention is prepared by the preparation method according to any one of claims 1 to 7.

9. Use of the composite gel loaded with strontium ions / zoledronic acid according to claim 8 in preparing bone defect repair materials.

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