CN110876818A

CN110876818A - Method for promoting PLGA degradation of bone repair material

Info

Publication number: CN110876818A
Application number: CN201911249311.0A
Authority: CN
Inventors: 章培标; 郝莉莉; 郭敏; 王宗良
Original assignee: Changchun Institute of Applied Chemistry of CAS
Current assignee: Changchun Institute of Applied Chemistry of CAS
Priority date: 2019-12-09
Filing date: 2019-12-09
Publication date: 2020-03-13
Anticipated expiration: 2039-12-09
Also published as: CN110876818B

Abstract

The invention provides a method for promoting PLGA degradation of a bone repair material, which comprises the following steps: under the action of an alternating magnetic field, alternating current stimulation is carried out on the ferroferric oxide nano particle-PLGA composite scaffold modified by the oleic acid, so that PLGA degradation is promoted. According to the invention, the oleic acid modified ferroferric oxide nano particles and PLGA (polylactic acid-glycolic acid copolymer) are combined to form the composite scaffold, under the stimulation of an alternating magnetic field, the oleic acid modified ferroferric oxide nano particles can effectively improve the degradation efficiency of the PLGA, and the degradation rate of the PLGA can be regulated and controlled by controlling the strength and time of the alternating magnetic field, so that the controllable degradation of the PLGA in vivo is realized; meanwhile, the oleic acid modified ferroferric oxide nanoparticles also have a T2 nuclear magnetic development tracing effect, and can track and observe the material degradation change and new bone growth conditions before and after bone formation at the defect part.

Description

Method for promoting PLGA degradation of bone repair material

Technical Field

The invention relates to the technical field of biological materials, in particular to a method for promoting PLGA degradation of a bone repair material.

Background

In recent years, more and more inorganic synthetic materials and organic synthetic polymer materials have been researched and developed as tissue engineering scaffolds or bone repair materials, and are gradually applied to clinics. The biodegradable material is an important component in tissue engineering, is an important factor for controlling the interaction with cells and tissues, and along with the development of the tissue engineering, people put forward new requirements on a matrix material for tissue regeneration, expect to research and develop a scaffold material for inducing cell adhesion, proliferation and differentiation, adapt the mechanical property of the material to a transplanted part, and match the degradation rate of the material in vivo with the growth rate of the tissue.

In the prior art, bone repair materials with different degradation rates are obtained by presetting the molecular weight, the polydispersity index, the stereoregularity and the polymer component proportion of the materials, and then are implanted into a body for application. However, when the bone repair scaffold is really implanted into the body, due to the existence of various uncertain factors such as movement, blood circulation and the like, the degradation process of the material in the body is complex, and the real in-vivo control cannot be realized.

Therefore, the degradable bone repair material polyester such as PLGA, which is commonly used in clinical practice, has the following defects when applied as a tissue engineering repair material: 1) the degradation regulation and control performance after implantation is lacked, the degradation rate can be only regulated and controlled by the molecular weight, the crystallinity and the proportion of copolymer components of in-vitro preset materials at present, and the real-time regulation and control can not be realized after the implantation of organisms; 2) the lack of in vivo traceability, the low density due to the porosity of such materials, makes it impossible to follow-up the post-implantation observations by means of existing Magnetic Resonance Imaging (MRI) or X-ray imaging. If the degradation rate of the implant is not matched with the tissue growth rate, the bone healing speed can be hindered and the healing quality can be influenced; meanwhile, the absorbable implant material is retained in the body for too long time (namely, the degradation rate is too slow or the degradation efficiency is poor), so that chronic inflammation is caused, and cavities are formed at the implanted part to influence the healing of bone tissues. Therefore, how to really realize controllable degradation in vivo, improve degradation efficiency and trace is a difficult point in research.

Based on this, the prior art proposes to use magnetic particles and polymer composite, such as patent application No. ZL201410522351.9, using microbeam GdPO with weak paramagnetism₄·H₂The O and the bone repairing material are blended to prepare the composite film, and the magnetic-thermal effect of gadolinium is utilized to release the nano materialA certain amount of heat, thereby promoting degradation of the bone repair material; and gadolinium has the functions of nuclear magnetic imaging and CT imaging tracing, and can be used for observing the growth condition of new bones and the degradation change of materials. However, the curie point of gadolinium is less than 20 ℃, the magnetic material shows paramagnetism once the curie point temperature is exceeded, the magnetocaloric effect is low and even disappears, so the experimental result is not ideal, the in vivo degradation of the repair material cannot be effectively promoted, when the material is degraded for 7 weeks under the magnetic field condition, the maximum mass loss of the material is only about 5.5%, and the degradation effect is poor.

Disclosure of Invention

In view of the above, the present invention provides a method for promoting degradation of a bone repair material PLGA, which can effectively improve the in vivo degradation efficiency of the bone repair material PLGA, can realize in vivo controllable degradation, can generate a tracing effect, and can monitor in real time the in vivo change of the bone repair material and the new bone formation condition.

The invention provides a method for promoting PLGA degradation of a bone repair material, which comprises the following steps:

under the action of an alternating magnetic field, alternating current stimulation is carried out on the ferroferric oxide nano particle-PLGA composite scaffold modified by the oleic acid, so that PLGA degradation is promoted.

Preferably, the conditions of the alternating current stimulation are as follows:

the intensity of the alternating magnetic field is 200-500 Gs, a Helmholtz coil with the frequency of 350-400 KHz is adopted, and the alternating current is controlled to be 20-40A.

Preferably, the oleic acid modified ferroferric oxide nanoparticles are prepared by the following steps:

a) FeCl is added₃·6H₂Dispersing O and sodium oleate in a solvent to obtain a dispersion liquid;

b) heating and back-distilling the dispersion liquid, cooling and layering, taking an upper oil phase, and carrying out rotary evaporation on the solvent to obtain an iron oleate compound;

c) and mixing the iron oleate compound with an organic solution of oleic acid for thermal decomposition reaction, washing and drying to obtain oleic acid modified ferroferric oxide.

Preferably, in step a):

the FeCl₃·6H₂The molar ratio of O to sodium oleate is 1: 2.8-3;

the solvent is a mixture of water, an organic solvent A and an organic solvent B;

the organic solvent A is selected from one or more of ethanol, methanol and ethyl acetate;

the organic solvent B is selected from one or more of n-hexane, petroleum ether or cyclohexane;

the volume ratio of the water to the organic solvent A to the organic solvent B is (2-5) to (5-10).

Preferably, in step b):

the temperature of the heating reflux is 70-85 ℃, and the time is 4-6 h.

Preferably, in step c):

the temperature of the thermal decomposition reaction is 300-320 ℃, and the time is 0.5-1 h;

the dosage ratio of the iron oleate compound to the organic solution of oleic acid is (16-20) g to (123-134) mL;

the organic solution of the oleic acid is a mixed solution of the oleic acid and an organic solvent C; wherein the volume ratio of the oleic acid to the organic solvent C is (120-130) to (3-4);

the organic solvent C is one or more selected from octadecene, nonadecene and eicosene.

Preferably, the mass ratio of oleic acid in the oleic acid modified ferroferric oxide is less than or equal to 30%;

the granularity of the ferroferric oxide nano particles modified by the oleic acid is 5-30 nm.

Preferably, the oleic acid modified ferroferric oxide nanoparticle-PLGA composite scaffold is prepared by the following steps:

s1) dispersing the ferroferric oxide nano particles modified by oleic acid in a solvent to obtain a suspension;

s2) dissolving PLGA in the suspension to obtain mixed solution;

s3) preparing a bracket by using the mixed solution as a base material to obtain the composite bracket.

Preferably, the step S3) includes:

s3a) injecting the mixed solution into a cavity with a built-in pore-foaming agent, compacting, freeze-drying, and demolding to obtain a prefabricated bracket;

s3b) soaking the prefabricated scaffold in water to replace a solvent and dissolve the pore-forming agent, and drying to obtain the composite scaffold.

Preferably, under the action of an alternating magnetic field, stimulating for 5-10 hours every day, and co-stimulating for 600-900 hours;

the degradation rate of the composite scaffold is regulated and controlled in real time by controlling the strength and time of the alternating magnetic field.

The invention provides a method for promoting PLGA degradation of a bone repair material, which comprises the following steps: under the action of an alternating magnetic field, alternating current stimulation is carried out on the ferroferric oxide nano particle-PLGA composite stent modified by oleic acid, and PLGA degradation is promoted. According to the invention, the oleic acid modified ferroferric oxide nano particles and PLGA (polylactic acid-glycolic acid copolymer) are combined to form the composite scaffold, under the stimulation of an alternating magnetic field, the oleic acid modified ferroferric oxide nano particles can effectively improve the degradation efficiency of the PLGA, and the degradation rate of the PLGA can be regulated and controlled by controlling the strength and time of the alternating magnetic field, so that the controllable degradation of the PLGA in vivo is realized; meanwhile, the oleic acid modified ferroferric oxide nanoparticles also have a T2 nuclear magnetic development tracing effect, and can track and observe the material degradation change and new bone growth conditions before and after bone formation at the defect part.

Drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to the provided drawings without creative efforts.

FIG. 1 is an XRD test pattern of a sample obtained in example 1;

FIG. 2 is an FTIR spectrum of a sample obtained in example 1;

FIG. 3 is a graph showing the change in mass loss of a stent under different degradation times with and without electric field stimulation;

FIG. 4 is a graph showing the change in weight average molecular weight of a stent under different degradation times in the presence and absence of electric field stimulation.

Detailed Description

According to the invention, the oleic acid modified ferroferric oxide nano particles and PLGA (polylactic acid-glycolic acid copolymer) are combined to form the composite scaffold, under the stimulation of an alternating magnetic field, the oleic acid modified ferroferric oxide nano particles can effectively improve the degradation efficiency of the PLGA, and the degradation rate of the PLGA can be regulated and controlled by controlling the strength and time of the alternating magnetic field, so that the controllable degradation of the PLGA in vivo is realized; meanwhile, the oleic acid modified ferroferric oxide nanoparticles also have a T2 nuclear magnetic development tracing effect, and can track and observe the material degradation change and new bone growth conditions before and after bone formation at the defect part.

GdPO in the prior art₄·H₂O belongs to paramagnetic substances, ferroferric oxide belongs to ferromagnetic substances, and when the particle size of the ferroferric oxide is smaller than the critical size, the superparamagnetic substance with a single-domain structure can be shown, and the magnetic response of different magnetic materials to a magnetic field is different. There is no relevant report about whether ferroferric oxide nanoparticles can regulate and control the degradation rate of the material through the magnetocaloric effect. The research of the applicant shows that both super-paramagnetic ferroferric oxide and oleic acid modified ferroferric oxide can generate a degradation promoting effect on PLGA through magnetic field stimulation, and compared with high-magnetism ferroferric oxide (the saturation magnetization Ms is 60-70 emu/g), the low-magnetism oleic acid modified ferroferric oxide nanoparticles (the saturation magnetization Ms is 40-50 emu/g) can improve the degradation efficiency of PLGA better, and the reason is presumed to be that the magnetocaloric degradation is not only related to the type and saturation magnetization of magnetic materials, but also related to the type and saturation magnetization of the magnetic materialsThe magnetic nanoparticles are involved in dispersibility in a degradable polymer material, entanglement with polymer chains, and the like.

In the invention, the oleic acid modified ferroferric oxide nanoparticles are preferably prepared by the following method:

With respect to step a):

in the present invention, the FeCl₃·6H₂The mol ratio of O to sodium oleate is preferably 1 to (2.8-3). The solvent is preferably water, a mixture of an organic solvent A and an organic solvent B. Wherein the water is preferably primary water (i.e. water obtained by once distillation); the organic solvent A is preferably one or more of ethanol, methanol and ethyl acetate; the organic solvent B is preferably one or more of n-hexane, petroleum ether or cyclohexane. In the solvent, the volume ratio of water to the organic solvent A to the organic solvent B is preferably (2-5) to (5-10). The dispersing mode is not particularly limited, and the materials are mixed and uniformly dispersed according to a conventional dispersing means well known to those skilled in the art. After the dispersion, a dispersion liquid was obtained.

With respect to step b):

in the heating reflux, the heating temperature is preferably 70-85 ℃ in the heating reflux, and the reflux is carried out for 4-6 h. Then cooling and demixing are carried out, after cooling and demixing, the upper oil phase is preferably washed by water, and then rotary evaporation treatment is carried out to remove the solvent. In the invention, the rotary evaporation temperature is preferably 35-45 ℃. After the solvent is removed by the rotary evaporation, an iron oleate compound which is Fe is obtained³⁺And C₁₇H₃₃CO₂ ^-The iron oleate complex formed.

With respect to step c):

in the invention, the organic solution of oleic acid is a mixed solution of oleic acid and an organic solvent C; the organic solvent C is preferably one or more of octadecene, nonadecene and eicosene, and is used as a reaction solvent for thermal decomposition reaction. Wherein the volume ratio of the oleic acid to the organic solvent C is preferably (120-130): (3-4). The dosage ratio of the iron oleate compound to the organic solution of oleic acid is (16-20) g to (123-134) mL.

The thermal decomposition temperature is preferably 300-320 ℃, and at the temperature, the organic solvent C boils to fully thermally decompose the iron oleate. The time of thermal decomposition is preferably 0.5-1 h.

The washing is preferably carried out by using an organic solvent, and in some embodiments, by using a mixed solution of petroleum ether and absolute ethyl alcohol; in some embodiments, the volume ratio of the petroleum ether to the absolute ethyl alcohol is 1: (3-5). After washing, centrifugation and drying were carried out. In the present invention, the drying is preferably vacuum drying; the drying temperature is preferably 20-60 ℃. And drying to obtain the oleic acid modified ferroferric oxide nano particles.

Compared with IO-OA nano particles obtained by other preparation methods, the thermal decomposition method for preparing the oleic acid modified ferroferric oxide (marked as IO-OA) nano particles has better degradation promoting effect on PLGA. Laboratory studies prove that compared with IO-OA synthesized by a coprecipitation method, the IO-OA obtained by the preparation method has higher saturation susceptibility, uniform size and difficult oxidation, and can generate higher magnetocaloric heat under the same magnetic field condition, thereby accelerating PLGA degradation; compared with the commercially available IO-OA, the preparation method can obtain IO-OA with a proper modification rate, and can achieve better dispersibility and effective entanglement in PLGA, thereby realizing faster acceleration of PLGA degradation.

In the invention, the mass ratio of oleic acid in the oleic acid modified ferroferric oxide is preferably less than or equal to 30%, more preferably 15-30%, and most preferably 20-25%; under the modification rate, the polylactic-co-glycolic acid (PLGA) can be better combined and coacted with PLGA to promote the degradation of the PLGA, if the modification rate is too low, IO-OA particles can be agglomerated and generate heat unevenly in a PLGA stent, and if the modification rate is too high, IO-OA particles can be entangled by themselves and cannot achieve the effects of uniform dispersion in the PLGA and effective entanglement with a matrix. In the present invention, the mass ratio or modification ratio refers to the mass percentage of the oleic acid chain in the total mass of the entire nanoparticle.

In the invention, the granularity of the ferroferric oxide nano particle modified by oleic acid is preferably 5-30 nm, more preferably 5-15 nm, and most preferably 8-12 nm.

In the invention, the ferroferric oxide nano particle-PLGA composite stent modified by oleic acid is preferably prepared by the following method:

s2) dissolving PLGA in the suspension to obtain mixed solution;

With respect to step S1):

in the present invention, the solvent is preferably N-methylpyrrolidone (i.e., NMP) and/or hexafluoroisopropanol. The preferable dosage ratio of the oleic acid modified ferroferric oxide nanoparticles to the solvent is (150-200) mg to (30-40) mL. The dispersion is preferably ultrasonic dispersion. After uniform dispersion, a suspension is obtained.

With respect to step S2):

in the invention, the dosage ratio of the PLGA to the suspension obtained in the step S1) is preferably (15-20) g: 100 mL. In the dissolving process, stirring is preferably carried out, and the stirring time is preferably 24-36 h. After uniform dissolution, mixed liquor is obtained.

With respect to step S3):

in the present invention, the preparation of the stent using the mixed solution obtained in step S2) as a base material preferably includes:

In the step S3a), the pore-forming agent is preferably sucrose. The grain size of the sucrose is preferably 0.25-0.4 μm. In some embodiments of the invention, the cavity is a syringe. In some embodiments, the syringe is a 2mL syringe. The volume ratio of the sucrose in the cavity is preferably 85-95%. And injecting the mixed solution into a cavity with a built-in pore-foaming agent, compacting, and freeze-drying. The temperature of the freeze drying is preferably-80 ℃, and the time is preferably 0.5-2 h. And (4) demolding to obtain the prefabricated support after the treatment.

In the step S3b), the water used is preferably deionized water. The temperature of the water is preferably 4-25 ℃. In the process of soaking the prefabricated support in water, preferably, deionized water is replaced once every 3-6 hours, and the prefabricated support is soaked for 72-96 hours to fully replace the organic solvent of the prefabricated support and dissolve the pore-forming agent. Drying after the soaking treatment; and drying at room temperature to obtain the oleic acid modified ferroferric oxide nanoparticle-PLGA composite scaffold.

In the oleic acid modified ferroferric oxide nanoparticle-PLGA composite stent, the mass ratio of the oleic acid modified ferroferric oxide nanoparticles to the composite stent is preferably 1-10%. If the proportion of the oleic acid modified ferroferric oxide nanoparticles is too low, the degradation promoting effect is poor, and if the proportion is too high, the local temperature in the magnetic heating process is too high after the stent is implanted into a body, so that inflammatory reaction is brought to host tissues.

According to the invention, the ferroferric oxide nano particle-PLGA composite scaffold modified by oleic acid is used as a tissue repair material, and alternating current stimulation is carried out under the action of an alternating magnetic field to promote PLGA degradation.

In the invention, the intensity of the alternating magnetic field is preferably 200-500 Gs, and in some embodiments of the invention, the intensity is 300 Gs; the time is preferably: stimulating for 5-10 h every day, and co-stimulating for 600-900 h. Under the conditions, the degradation rate of PLGA can reach 50-70%. The invention can adjust and control the degradation rate of the stent in real time by controlling the strength and time of the alternating magnetic field, so that the PLGA can realize controllable degradation in vivo.

In the invention, in the alternating current stimulation, a Helmholtz coil with the frequency of 350-400 KHz is preferably adopted, namely the period is 1/350000-1/400000 s, and the current direction is changed once in each period. The alternating current is preferably 20-40A; under above-mentioned electric current scope, promotion support degradation that can be better, if the electric current undersize, can not reach the effect of obvious accelerated support degradation, can't effective monitoring, if the electric current is too big, the inside high temperature of support, the alternation stimulus in the short time (in a week) can lead to the support to collapse, loses practical application and worth.

According to the invention, the ferroferric oxide nano particles modified by oleic acid are applied to the PLGA bone repair material, so that the degradation efficiency of PLGA is improved, the in-vivo controllable degradation is realized, meanwhile, the T2 nuclear magnetic imaging tracing effect can be generated, and the material degradation change and new bone growth conditions before and after the bone formation of the defect part can be tracked and observed.

Specifically, the method for promoting the degradation of the bone repair material PLGA provided by the invention has the following beneficial effects:

(1) the ferroferric oxide nano particles modified by oleic acid are applied to the PLGA repair material, so that the degradation efficiency of PLGA can be effectively improved. Moreover, compared with magnetic ferroferric oxide (the saturation susceptibility Ms is 60-70 emu/g), the low-magnetism oleic acid modified ferroferric oxide nanoparticles (the saturation susceptibility Ms is 40-50 emu/g) can improve the PLGA degradation efficiency better.

(2) According to the invention, by controlling the appropriate oleic acid modification rate (20-25%) in the oleic acid modified ferroferric oxide nanoparticles, compared with other products with modification rates, PLGA degradation can be better promoted.

(3) According to the invention, the oleic acid modified ferroferric oxide nanoparticles are prepared by adopting a specific thermal decomposition method, and compared with IO-OA nanoparticles prepared by other preparation methods, the oleic acid modified ferroferric oxide nanoparticles have a better degradation promoting effect on PLGA. As proved by small-scale research, compared with IO-OA synthesized by a coprecipitation method and IO-OA sold in the market, the IO-OA prepared by the preparation method can realize faster acceleration of PLGA degradation.

(4) According to the invention, by controlling a proper alternating magnetic field condition, the oleic acid modified ferroferric oxide nano particles can be stimulated to better realize PLGA degradation.

(5) Experiments prove that a certain degradation rule exists between the PLGA degradation promoting effect of the IO-OA nano particles and the alternating magnetic field conditions, the degradation rate of the IO-OA nano particles to the PLGA can be regulated and controlled in real time by controlling the strength and time of the alternating magnetic field, the controllable degradation of the PLGA in vivo is realized, and the repair requirements of different bone defect parts are met.

(6) The IO-OA nano particle can also generate a T2 nuclear magnetic development tracing effect, and can track and observe the material degradation change and new bone growth condition before and after bone formation at a defect part.

For a further understanding of the invention, reference will now be made to the following examples describing preferred embodiments of the invention, but it is to be understood that the description is intended to illustrate further features and advantages of the invention and is not intended to limit the scope of the claims. In the following examples, PLGA was used as a commercial product, and the weight average molecular weight was 200KDa, and the mass ratio of lactic acid was 75%.

Example 1 preparation of oleic acid-modified ferroferric oxide nanoparticles

1.1 sample preparation

Taking 0.02mol FeCl₃·6H₂O and 0.06mol of sodium oleate are placed in 140mL of solvent (the volume ratio of primary water to ethanol to normal hexane is 3: 4: 7), and ultrasonic dispersion is carried out (the power is 240w, the duration is 30 min); then, the mixture is distilled back for 5 hours at the temperature of 80 ℃, cooled and layered, the upper oil phase is washed three times by 40mL of water, and the solvent is evaporated in a rotary manner (the temperature is 40 ℃ and the time is 20min), so that the iron oleate compound is obtained.

Adding 120mL of octadecene and 3mL of oleic acid into the iron oleate compound, heating to 320 ℃, and preserving heat for 0.5 h. Washing the sample with a mixed solution of petroleum ether and absolute ethyl alcohol (volume ratio is 1: 4) until the supernatant is colorless, centrifuging and then drying in vacuum to obtain the oleic acid modified ferroferric oxide nanoparticles (marked as IO-OA).

1.2 characterization and testing of samples

(1) The obtained product is characterized by X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR), and the results are respectively shown in figures 1 and 2, wherein figure 1 is an XRD test pattern of the sample obtained in example 1, and figure 2 is an FTIR spectrum of the sample obtained in example 1. It can be seen that the characteristic peaks of the sample in the XRD pattern are well matched with those of magnetite crystals with an inverse cubic spinel structure (JCPDS 19-0629), and the characteristic peaks of characteristic functional groups of oleic acid, such as-CH 2-, COO-, C ═ C, appear in the FTIR spectrum, which proves that the obtained product is ferroferric oxide modified by oleic acid.

(2) The resulting product was subjected to a thermogravimetric analysis (TGA) and the result showed that the modification rate of the sample was 24%.

(3) And (3) performing Transmission Electron Microscope (TEM) characterization on the obtained product, wherein the result shows that the particle size of the obtained particles is 5-15 nm.

(4) The sample was tested for saturation magnetic susceptibility using a Vibrating Sample Magnetometer (VSM), which showed a saturation magnetic susceptibility of 46 emu/g.

Example 2 preparation of ferroferric oxide nanoparticles

The preparation process of the embodiment 1 is carried out, except that sodium oleate is not added, and the temperature is kept at 320 ℃ for 2h, so as to obtain pure ferroferric oxide nanoparticles (marked as IO).

The obtained product is characterized and tested according to the characterization method of the embodiment 1, and the result shows that the obtained product is pure ferroferric oxide and has the particle size of 15-30 nm. The saturation magnetic susceptibility was 65 emu/g.

EXAMPLE 3 preparation of scaffolds

3.1 preparation of oleic acid-modified ferroferric oxide nanoparticle-PLGA composite scaffold

180mg of IO-OA nano-particles prepared in example 1 are dispersed in 35mL of N-methylpyrrolidone, and uniformly mixed by ultrasonic dispersion (power 240w, duration 1h) to obtain a suspension. Thereafter, 5g of PLGA was dissolved in the suspension by mechanical stirring and stirred overnight to obtain a mixture.

And (3) injecting the mixed solution into a 2mL injector (the volume ratio of sucrose in the injector is 90%) with sucrose (the particle size is 0.25-0.4 mu m), compacting, freeze-drying at-80 ℃ for 1h, and demolding to obtain the prefabricated support.

And placing the obtained prefabricated scaffold in deionized water at 10 ℃, replacing the deionized water once every 4h, soaking the prefabricated scaffold in the water for 96h to fully replace the organic solvent and dissolve the sucrose particles, and drying the prefabricated scaffold at room temperature to obtain the oleic acid modified ferroferric oxide nano particle-PLGA composite scaffold (marked as IO-OA/PLGA).

3.2 preparation of ferroferric oxide nanoparticle-PLGA composite scaffold

According to the preparation process in 3.1, except that the IO-OA nano particles are replaced by the IO nano particles prepared in the embodiment 2, the ferroferric oxide nano particle-PLGA composite stent (marked as IO/PLGA) is obtained.

3.3 preparation of PLGA scaffolds

The preparation process in 3.1 is carried out, except that no IO-OA nano-particles are added, and the PLGA stent is obtained.

EXAMPLE 4 testing of Stent degradability

Adopts the method that the temperature is 37 ℃, the humidity is 100 percent, and CO is adopted₂Performing a magnetic control degradation test on the material by using a 5% cell culture box, and simulating an in-vivo microenvironment; the scaffold was placed in phosphate buffer and then placed in the cell incubator.

A Helmholtz coil with the frequency of 350KHz is selected, and the alternating current is controlled to be 20A. The type 3 scaffolds prepared in example 3 (IO-OA/PLGA, IO/PLGA, PLGA scaffolds) were respectively placed in an alternating magnetic field (intensity of 300Gs) and stimulated for 8h each day. After a period of degradation, the degradation performance of different scaffolds in phosphate buffer solution was tested by a weight loss method in combination with an instrumental analysis method, and compared with a control sample without an applied electric field, and the results are shown in fig. 3 and 4. FIG. 3 is a graph showing the change in mass loss of the scaffold with and without electric field stimulation for different degradation times, and FIG. 4 is a graph showing the change in weight average molecular weight of the scaffold with and without electric field stimulation for different degradation times.

As can be seen from FIGS. 3 and 4, the mass loss change and the weight average molecular weight change trend of the type 3 scaffolds (IO-OA/PLGA, IO/PLGA, PLGA scaffolds) at different times are similar under the condition of no alternating magnetic field stimulation (corresponding to AMF < - > in the figure), and similar degradation behaviors are shown.

It can also be seen from FIG. 3 that the mass loss of the IO-OA/PLGA scaffold at different times is always higher than that of the IO/PLGA and PLGA scaffolds under the condition of the alternating magnetic field stimulation (corresponding to AMF + in the figure), and the mass loss is obviously improved especially at 12 weeks and 16 weeks. Meanwhile, as can be seen from FIG. 4, in the condition of alternating magnetic field stimulation, the molecular weight of the IO-OA/PLGA scaffold is reduced rapidly in the initial degradation stage, and the molecular weight is always lower than that of the IO/PLGA scaffold and the PLGA scaffold. Therefore, the degradation rate of the IO-OA/PLGA stent is obviously superior to that of the IO/PLGA and PLGA stents, and the low-magnetic IO-OA nano particles are improved in degradation rate compared with the high-magnetic IO nano particles.

Example 5 degradation of PLGA by IO-OA nanoparticles prepared by different preparation methods

(1) Preparing IO-OA nano particles by adopting a coprecipitation method:

taking 4mmol of FeCl₂·4H₂O、6mmolFeCl₃·6H₂O, 32mmol of sodium oleate and 36mmol of sodium hydroxide, and placing the mixture in 84mL of solvent (the volume ratio of primary water to ethanol to toluene is 3: 4: 7); then, in N₂Under protection, the reaction solution is distilled back for 4 hours at the temperature of 75 ℃, cooled to room temperature, poured into 350mL of ethanol, and black precipitates are collected by a magnet; and finally, washing the sample with primary water for 3 times, collecting the sample with a magnet, and then carrying out freeze drying to obtain the IO-OA nano particles.

The IO-OA nanoparticles obtained by the characterization and testing method in example 1 were tested, and the results show that the co-precipitation method has a low yield, the OA modification rate on the surface of the nanoparticles is low (only 4%), when the nanoparticles are compounded with PLGA, the nanoparticles cannot be uniformly dispersed in the PLGA matrix, the effect of effectively entangling with the polymer chains cannot be achieved, and as a result, a good degradation promoting effect cannot be achieved.

Example 6 degradation of PLGA by IO-OA nanoparticles of different modification rates

The preparation process of example 1 was followed to prepare oleic acid-modified ferriferrous oxide nanoparticles, except that the thermal decomposition time of the iron oleate complex was reduced (i.e. the thermal decomposition time was less than 0.5h), and the results showed that while the OA modification rate in the product was increased, the crystallinity and magnetic properties of ferriferrous oxide were greatly reduced, which resulted in a reduction in the magnetocaloric degradation effect.

Prepare oleic acid modified ferriferrous oxide nanoparticles according to the preparation process of example 1, except that the time for thermal decomposition of the iron oleate complex is controlled to be 2 hours, so as to obtain IO-OA nanoparticles with oleic acid modification rate of about 3%, similar to pure ferriferrous oxide, and the magnetocaloric degradation effect is reduced compared with example 1.

Therefore, the method is proved to be capable of further improving the PLGA degradation effect by controlling the appropriate modification rate.

The above description of the embodiments is only intended to facilitate the understanding of the method of the invention and its core idea. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without departing from the spirit or scope of the invention. Thus, the present invention is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method of promoting PLGA degradation of a bone repair material, comprising:

2. The method according to claim 1, characterized in that the conditions of the alternating current stimulation are:

3. The method according to claim 1, wherein the oleic acid-modified ferroferric oxide nanoparticles are prepared by:

4. A method according to claim 3, characterized in that in step a):

the FeCl₃·6H₂The molar ratio of O to sodium oleate is 1: 2.8-3;

5. A method according to claim 3, characterized in that in step b):

the temperature of the heating reflux is 70-85 ℃, and the time is 4-6 h.

6. A method according to claim 3, characterized in that in step c):

7. The method according to any one of claims 1 to 6, characterized in that the mass ratio of oleic acid in the oleic acid-modified ferroferric oxide is less than or equal to 30%;

8. The method according to claim 1, wherein the oleic acid-modified ferroferric oxide nanoparticle-PLGA composite scaffold is prepared by:

s2) dissolving PLGA in the suspension to obtain mixed solution;

9. The method according to claim 8, wherein the step S3) comprises:

10. The method according to claim 1 or 2, characterized in that under the action of the alternating magnetic field, the stimulation is carried out for 5-10 h every day, and the co-stimulation is carried out for 600-900 h;