CN112206347B - A kind of composite bone cement with molecular weight matching enhanced performance and its preparation method and application - Google Patents

Abstract

The invention discloses a composite bone cement with molecular weight matching and enhanced performance, and a preparation method and application thereof. The composite bone cement whose molecular weight matches and enhances performance is composed of a solid component and a liquid component, and the solid component comprises polymethyl methacrylate, methyl methacrylate-styrene block copolymer and an initiator; The liquid component includes methyl methacrylate and an accelerator; the molecular weight of the methyl methacrylate-styrene block copolymer is less than or equal to that of polymethyl methacrylate.

Through the molecular weight matching of PMMA and P(MMA-co-St), the present invention can coordinate the balance between the mechanical properties of the viscosity of PMMA bone cement and the excessively rapid change in viscosity, which can meet the operational requirements of clinicians, and can PMMA with lower molecular weight can meet the mechanical properties of bone cement without adding other additives for enhancing mechanical properties, which has great application prospects.

Description

A kind of composite bone cement with molecular weight matching enhanced performance and its preparation method and application

technical field

The present invention relates to the technical field of medical materials, and more particularly, to a composite bone cement with enhanced performance of size matching and a preparation method and application thereof.

Background technique

Polymethyl methacrylate (PMMA) bone cement is a widely used material for vertebroplasty due to its good mechanical properties and the advantages of being able to be made into any shape for rapid prototyping. At present, there are about 70 kinds of PMMA bone cements on the market, which are widely used in orthopedic filling materials and fixation materials, especially in the treatment of vertebral compression fractures by vertebroplasty, which can quickly stabilize the injured vertebral body and relieve the symptoms of patients. Bone cement is mainly composed of polymethyl methacrylate (powder) and monomer methyl acrylate (liquid). PMMA is odorless and has stable performance. MMA is a colorless liquid with a pungent odor, volatile, flammable, lipophilic, and cytotoxic. Under certain conditions, it can self-polymerize and solidify into polymer PMMA. Due to the fiber characteristics of polymer molecules, coupled with its ability to extend and entangle, molecular weight becomes an important factor in its performance. Although high molecular weight PMMA can meet the mechanical properties of bone cement, it will lead to too short bone cement preparation and injection time (the viscosity changes too fast), which is not conducive to clinical operation, and the molecular weight of PMMA is too low, which will make the mechanical properties of bone cement. not to standard. Therefore, it is necessary to find a balance between the mechanical properties that can coordinate the viscosity of PMMA bone cement and the viscosity change too quickly, so as to meet the operational needs of clinicians, and to use PMMA with a lower molecular weight to meet the needs of bone cement. Mechanical properties of bone cement materials. Patent CN108096629 A discloses a polymethyl methacrylate bone cement, consisting of a solid component and a liquid component, including solid components A and B, wherein the solid component A includes polymethyl methacrylate, methyl methacrylate, and Methyl methacrylate-styrene block copolymer, solid component B contains mineralized collagen; it is controlled by regulating the molecular weight and addition of components such as polymethyl methacrylate and methyl methacrylate-styrene block copolymer The ratio of the polymerization reaction time, the viscosity of the polymer and the heat released, it is necessary to additionally improve the mechanical properties and biocompatibility of bone cement by adding mineralized collagen with good osteogenic activity. Because the molecular weight and addition ratio of polymethyl methacrylate and methyl methacrylate-styrene block copolymer in its solid component A cannot meet a certain matching relationship, the improvement effect on the mechanical properties of bone cement is not satisfactory. good.

SUMMARY OF THE INVENTION

The purpose of the present invention is to overcome the above-mentioned defects and deficiencies in the prior art, and to provide a composite bone cement with molecular weight matching and enhanced performance.

The second object of the present invention is to provide a preparation method of the composite bone cement whose molecular weight is matched to enhance performance.

The third object of the present invention is to provide the application of the composite bone cement whose molecular weight is matched to enhance performance.

The above-mentioned purpose of the present invention is achieved by the following technical solutions:

A composite bone cement with molecular weight matching and enhancing performance, consisting of a solid component and a liquid component, characterized in that: the solid component comprises polymethyl methacrylate, methyl methacrylate-styrene block copolymer and an initiator; the liquid component includes methyl methacrylate and an accelerator; the molecular weight of the methyl methacrylate-styrene block copolymer (P(MMA-co-St)) is less than or equal to polymethyl methacrylate Methyl methacrylate (PMMA)

In the present invention, the relationship between the molecular weight of the small molecular P(MMA-co-St) copolymer and the large molecular weight PMMA is determined, and the small molecular P(MMA-co-St) copolymer is used to fill the relationship between the large molecular weight PMMA molecules. When the molecular weight of P(MMA-co-St) is slightly smaller, it can be evenly distributed in PMMA with a larger molecular weight to fill the intermolecular gap, which significantly improves the compressive strength of bone cement. , when within the above range of the present invention, the compressive strength of the composite bone cement increases with the molecular weight and dosage of the P(MMA-co-St) polymer, but it will not make the small molecular P(MMA-co-St) polymer. St) fills the void range of PMMA with a large molecular weight, which makes it impossible to fill, thereby effectively improving the mechanical properties of bone cement. It can coordinate the balance between the mechanical properties of the viscosity of PMMA bone cement and the viscosity changes too fast, which can meet the needs of clinicians. The mechanical properties of bone cement can be met by PMMA with lower molecular weight according to the operational requirements.

Preferably, the mass ratio of the polymethyl methacrylate to the methyl methacrylate-styrene block copolymer is 1:1-2.

Preferably, the mass-volume ratio of the solid component and the liquid component is 1:3-4 mL.

Preferably, the initiator is benzoyl peroxide (BPO).

Preferably, the accelerator is N,N-dimethyl-p-toluidine (DMT).

Further preferably, the molecular weight of the polymethyl methacrylate is 750,000, the molecular weight of the methyl methacrylate-styrene block copolymer is 60,000-116,000, and the compressive strength of the bone cement can reach more than 75MPa.

The present invention also provides a method for preparing any of the above-mentioned composite bone cement with matching and enhancing performance, which is obtained by mixing solid components and liquid components in corresponding proportions, stirring them evenly, pouring them into a mold, and curing.

Preferably, the solid component and the liquid component are mixed uniformly in a mass-to-volume ratio of 1:3-4 mL.

Further preferably, the solid component and the liquid component are mixed uniformly in a mass-to-volume ratio of 1:3 mL.

In addition, the present invention also provides the application of any of the above-mentioned composite bone cements with matching and enhancing properties in molecular weight in the preparation of orthopaedic implant materials. By studying the molecular weight and dosage of the added P(MMA-co-St) polymer, it was found that the compressive strength of the composite bone cement increased with the molecular weight and dosage of the P(MMA-co-St) polymer within a certain range. The mechanical properties of bone cement can be adjusted by matching a certain molecular weight P(MMA-co-St) and PMMA. This provides a strong theoretical basis for the future research on adding active components and antibiotics to bone cement.

Compared with the prior art, the present invention has the following beneficial effects:

In the present invention, the ratio of methyl methacrylate-styrene block copolymer with lower molecular weight of bone cement and polymethyl methacrylate polymer with higher molecular weight is adjusted, and the ratio between PMMA and P(MMA-co-St) is adjusted. Molecular weight matching can coordinate the balance between the mechanical properties of PMMA bone cement viscosity and the viscosity changes too fast, which can meet the operational needs of clinicians, and can meet the mechanical properties of bone cement with lower molecular weight PMMA, and There is no need to add other additives for enhancing mechanical properties, and it has great application prospects.

Description of drawings

Figure 1 shows the equivalent of PMMA and P(MMA-co-St) into two spheres with different radii as follows.

Figure 2 is a schematic diagram of the approximate molecular weight of the higher molecular weight PMMA to fill the molecular-to-molecular voids of the lower molecular weight P(MMA-co-St).

FIG. 3 is the ¹ H NMR spectrum of the synthesis of P(MMA-co-St) with the monomer MMA/St ratio of 7:3.

FIG. 4 is the ¹ H NMR spectrum of the synthesis of P(MMA-co-St) with the monomer MMA/St ratio of 8:2.

Figure 5 shows the compressive strengths of bone cements synthesized with different molecular weights of P(MMA-co-St) polymer and PMMA in different proportions (wherein MS in the figure represents P(MMA-co-St) polymer).

Figure 6 is a schematic diagram of high molecular weight PMMA molecules and filling P(MMA-co-St) between molecules to provide the compressive strength of bone cement.

Figure 7 shows the survival rate of rBMSCs in PMMA/P(MMA-co-St) composite bone cement.

Detailed ways

The present invention is further described below with reference to the accompanying drawings and specific embodiments, but the embodiments do not limit the present invention in any form. Unless otherwise specified, the reagents, methods and equipment used in the present invention are conventional reagents, methods and equipment in the technical field.

Unless otherwise specified, the reagents and materials used in the following examples are commercially available.

The invention aims to seek a method for preparing bone cement with optimal viscosity and mechanical properties by adjusting the ratio of the powders of polymers with lower molecular weight and higher molecular weight of bone cement. Due to the intermolecular gaps left by the stacking of large molecular weight PMMA molecules, the mechanical properties of bone cement can be greatly enhanced if it can be filled with small molecular P(MMA-co-St) copolymers. Since the general natural tendency of the polymer chain is to form a coiled state, the longer the polymer chain, the more molecular conformations, the greater the possibility of the molecular chain being rolled into various shapes, and the better the flexibility of the molecule. Therefore, we equivalent PMMA and P(MMA-co-St) into two spheres with different radii as shown in Fig. 1.

According to the relationship between the square of the distance between the ends of the polymer chain and the molecular weight r ² =CM and the relationship between the mean square end distance and the mean square radius of rotation when the molecular weight is large enough <R _g ² >=<r ² >/6, the equivalent Correspondence between sphere radius and average molecular weight. The approximate molecular weight of the smaller molecular weight P(MMA-co-St) is filled by recalculating the molecular-to-molecule gaps of the higher molecular weight PMMA of known molecular weight, as shown in Figure 2:

时能刚好嵌入PMMA分子之间的空隙中。已知的PMMA分子量为750000，则要求的P(MMA-co-St)分子量应该大约在116000左右。According to the geometric relationship, the radius of P(MMA-co-St) is the radius of PMMA

It can just fit into the space between the PMMA molecules. The known molecular weight of PMMA is 750,000, and the required molecular weight of P(MMA-co-St) should be about 116,000.

The most clinically used PMMA bone cement is composed of powder and liquid. The main component of powder is polymethyl methacrylate, and the main component of liquid is methyl methacrylate monomer. In the invention, a PMMA/P(MMA-co-St) composite bone cement is designed, wherein the powder components are polystyrene methyl methacrylate (P(MMA-co-St)), PMMA, benzoyl peroxide (BPO), the liquid components are methyl methacrylate (MMA), N,N-dimethyl-p-toluidine (DMT). Through the above calculation model, the best matching relationship between high molecular weight PMMA and low molecular weight P(MMA-co-St) is to be sought. The polymethyl methacrylate described below was purchased from Sigma (CAS number: 9011-14-7), and the low molecular weight P(MMA-co-St) was synthesized by itself.

Example 1 Preparation of raw materials

1. Synthesis of P(MMA-co-St):

(1) Purification of raw materials:

Styrene purification: take 150 mL of styrene into a 250 mL separatory funnel, repeatedly wash with 1 mol/L NaOH aqueous solution until it turns from pink to colorless, and then wash with deionized water until neutrality is measured with pH test paper. After drying with anhydrous sodium sulfate overnight, a little p-tert-butylcatechol was added for distillation under reduced pressure.

MMA purification: Wash with aqueous NaOH until colorless, then with deionized water until neutral. Dry with anhydrous sodium sulfate, then add a little hydroquinone and distill under reduced pressure.

BPO purification: add 5g BPO and 20mL chloroform to a 100mL beaker, stir continuously to dissolve it, and filter the filtrate; add 50mL methanol to a 100mL beaker, seal it and place it in a 4°C refrigerator for cooling; slowly drop the filtrate into the cooled methanol and stirring continuously until needle crystals no longer increase, filter, and dry in vacuo.

(2) Preparation of dispersant:

Preparation of 1 mol/L MgCl ₂ aqueous solution: take 10.15 g of magnesium chloride hexahydrate to a constant volume in a 50 mL volumetric flask, shake well and transfer to a blue-mouthed bottle.

Preparation of 1 mol/L NaOH aqueous solution: take 10 g of NaOH to a constant volume in a 250 mL volumetric flask, shake well and transfer it to a blue-mouthed bottle.

Preparation of 1% polyvinyl alcohol (PVA): take 0.5g of PVA in a 100mL beaker, stir and heat to 95°C in an oil bath until completely dissolved, cool, make up to a 50mL volumetric flask, shake well, and transfer to a blue-mouth bottle.

(3) Synthesis of P(MMA-co-St)

P(MMA-co-St) was synthesized by suspension polymerization. Add 40mL deionized water, 3mL 1% PVA aqueous solution, 3mL 1mol/L MgCl ₂ aqueous solution, 6mL 1mol/L NaOH aqueous solution to the three-necked flask, heat to 50 ℃ in oil bath, and the mechanical stirring speed is 300rpm; respectively add 7mL MMA, 3mL benzene Ethylene, add 0.2 g of BPO when heated to 70°C, continue to heat up to 80°C and react for 3-6 hours. In the same way, when adding 8mL MMA and 2mL styrene, the dosage of 1% PVA aqueous solution is 2mL, and other conditions remain unchanged, and finally polymethylmethacrylate styrene beads with uniform size and hard texture are obtained. Washed with 1 mol/L hydrochloric acid for 3 times, washed with deionized water until neutral, and dried under reduced pressure. After it is completely dry, grind it with a ball mill, grind it into powder, and store it in a dry state.

2. Characterization of P(MMA-co-St)

Molecular weight characterization of P(MMA-co-St): Waters Breeze GPC was used to determine the molecular weight of P(MMA-co-St) copolymer, tetrahydrofuran was used as mobile phase and solvent, and the sample concentration was 2 mg/mL. Amount of 100 μL.

Table 1 shows the P(MMA-co-St) synthesized by adjusting the amount of PVA and the rotational speed of different batches of monomer MMA/St according to 7:3, and the P(MMA-co-St) synthesized when monomer MMA/St=8:2 co-St), its weight average molecular weight Mw is 60000D, 69000D, 75000D, 129000D respectively. The details are as follows in Table 1:

Table 1

This is due to the rapid agitation of water-insoluble monomers and initiators in a vessel containing water to form small droplets containing the initiator, which are stabilized by the action of the dispersing agent and undergo bulk polymerization in the droplets . When the amount or rotation speed of PVA in the reaction system increases, the size of the particles decreases, and the molecular weight decreases; when the proportion of styrene is high, due to the steric hindrance of the benzene ring structure, the degree of polymerization is relatively low, so when the proportion of MMA is increased The molecular weight of the product is higher than the original. According to the preset optimal molecular weight of 116000, the best mechanical properties of the four synthesized groups should be Mw=75000. Since the Mw=129000 group exceeds the preset optimal molecular weight, it may not be able to be effectively filled between the PMMA molecules. However, the exact results need to be verified in combination with tensile tests.

¹ H NMR nuclear magnetic resonance of P(MMA-co-St): The polymer structure of P(MMA-co-St) was determined by the German Bruker Avance III nuclear magnetic resonance instrument at 400 MHz, the sample concentration was 8 mg/mL, deuterated chloroform (CDCl ₃ ) is the solvent, and trimethylsilyl (TMS) is the internal standard.

Figures 3 and 4 show the ¹ HNMR spectra of the P(MMA-co-St) copolymers synthesized by the monomer MMA/St at 7:3 and 8:2, respectively. The calculated proportion of styrene is 27.6 %, 19.7%.

Example 2 Synthesis of bone cement

At room temperature, the solid component and the liquid component of the bone cement are mixed in a mass-to-volume ratio (W/V) of 1:3, stirred evenly, poured into the mold, and completely cured, knocked out to take out the sample.

The solid phase components are PMMA, P(MMA-co-St), and BPO, and the liquid phase components are MMA and DMT, and the curing temperature is measured by a long rod thermometer. The raw material ratio, injectable time, curing time and curing temperature are shown in Table 2 below.

Table 2

Note: The weight-average molecular weight in the above table represents the molecular weight of P(MMA-co-St)

By recording the injection time and curing temperature, it was found that the bone cement with the addition of P(MMA-co-St) polymer can obviously delay its injection time and effectively reduce the curing temperature of the system. Bone cement is not an adhesive, and the connection of the cement to the bone and the connection of the cement to the prosthesis is entirely mechanical, with no chemical or molecular interactions, and no surface adhesion is provided. Bone cement penetrates into the cancellous bone and is a morphologically matched connection. When the lower molecular weight P(MMA-co-St) polymer is added to the bone cement as a powder, the fluidity of the system can be better, which can not only prolong the clinical injection time of doctors, but also make the bone cement more suitable for injection. It is more efficiently absorbed by cancellous bone during the process.

Example 3 Mechanical property test

The mechanical property characterization of bone cement in Example 2 mainly chooses to test the compressive property of the finished product. The test method is as follows: the compression test bone cement sample is ground into a cylinder with a length of 12 mm and a diameter of 6 mm. A universal material testing machine (WD-5A) was used with a loading rate of 5 mm/min. Record the stress-deformation diagram of the sample, take the stress when the K value in the stress-deformation curve is 2%, and divide it by the cross-sectional area of the cylinder to obtain the compressive strength. All mechanical property tests are carried out according to ISO 5833 international standard.

The mechanical properties of the PMMA/P(MMA-co-St) composite bone cement in the present invention are characterized by compressive strength. From Figure 5, the compressive strength of the bone cement with the addition of P(MMA-co-St) polymer is significantly higher than that of the pure PMMA bone cement, and within a certain range, with the increase of molecular weight, the same proportion of PMMA The compressive strength of /P(MMA-co-St) bone cement showed an upward trend, until the molecular weight increased to 116000, the compressive strength decreased instead. This is because when the molecular weight is slightly smaller, it can be evenly distributed in PMMA with a larger molecular weight to fill the gaps between molecules, so that the compressive strength of the bone cement is significantly improved, and both reach above 75MPa, as shown in Figure 6. From the perspective of the corresponding relationship between the molecular weight of the added P(MMA-co-St) polymer and the compressive strength of the composite bone cement, this method will also provide a strong theoretical support for the later addition of active components and antibacterial drugs to the bone cement.

Example 4 In vitro cytotoxicity test of bone cement

1. Sample preparation and pretreatment

Get the best one group proportioning of compressive strength in embodiment 3 and synthesize PMMA/P (MMA-co-St) composite bone cement according to the feeding of embodiment 2, and grind to grow 5mm, the cylindrical bone cement sample of diameter 6mm, every The group set up 5 parallel samples, and weighed the mass y g of each sample. In a 48-well plate, soak in 75% alcohol and phosphate buffered saline (PBS) for 1 day, respectively.

2. Preparation of leaching solution

Aspirate the PBS solution from the samples prepared above, and soak the samples in a volume of DMEM containing serum and double antibody for one day. The formula for calculating the amount of DMEM: y(g)×5(ml/g)=z ml, where z is the volume of DMEM.

3. MTT test

Inoculate P4 generation mouse bone marrow mesenchymal stem cells (rBMSCs) in a 48-well plate, 5000 cells per well, add 200 μl of culture medium and incubate for 24 hours, aspirate 100 μl of culture medium, and add 100 μl of bone cement prepared in step 2 to each well Extraction solution, add 100 μl of fresh medium to the control group, and after culturing for 24 hours and 48 hours respectively, aspirate the medium, add 20 μl MTT and 180 μl fresh medium, incubate at 37°C for 4 hours, add 200 μl DMSO and incubate for 10 min, remove 150 μl was placed in a 96-well plate, and the absorbance (OD) at a wavelength of 570 nm was measured.

It can be seen from Figure 7 that the survival rate of rBMSCs in the PMMA/P(MMA-co-St) composite bone cement is all above 80%. The results showed that the PMMA/P(MMA-co-St) composite bone cement had no toxic and side effects.

The above results show that the present invention fills the large molecular weight with the small molecular P(MMA-co-St) copolymer by determining the relationship between the molecular weight of the small molecular P(MMA-co-St) copolymer and the large molecular weight PMMA. It is feasible to improve the compressive strength of bone cement by leaving intermolecular gaps when the PMMA molecules are stacked. When it is within a certain range, the compressive strength of composite bone cement varies with the P(MMA-co-St) polymer. There is an increasing relationship between the molecular weight and the dosage, so there is no need to add other additives to improve the mechanical properties of bone cement.

Claims (9)

1. A composite bone cement with matching and enhancing performance of molecular weight is composed of a solid component and a liquid component, and is characterized in that: the solid component comprises polymethyl methacrylate, methyl methacrylate-styrene block copolymer and an initiator; the liquid component comprises methyl methacrylate and a promoter; the molecular weight of the methyl methacrylate-styrene block copolymer is less than or equal to that of the polymethyl methacrylate

The mass ratio of the polymethyl methacrylate to the methyl methacrylate-styrene segmented copolymer is 1: 1-2.

2. The composite bone cement of claim 1, wherein the mass-to-volume ratio of the solid component to the liquid component is 1 g: 3-4 mL.

3. The composite bone cement of claim 1, wherein the initiator is benzoyl peroxide.

4. The composite bone cement of claim 1, wherein the accelerator is N, N-dimethyl-p-toluidine.

5. The composite bone cement of claim 1, wherein the weight average molecular weight of the polymethylmethacrylate is 750000, and the weight average molecular weight of the methylmethacrylate-styrene block copolymer is 60000-116000.

6. The preparation method of the molecular weight matching enhanced composite bone cement as claimed in any one of claims 1 to 5, characterized in that the solid component and the liquid component in corresponding proportion are mixed and stirred uniformly, poured into a mold and cured to obtain the final product.

7. The method according to claim 6, wherein the solid component and the liquid component are mixed in a mass-to-volume ratio of 1 g: and (3-4 mL) uniformly mixing.

8. The method according to claim 7, wherein the solid component and the liquid component are mixed in a mass-to-volume ratio of 1 g: 3mL of the mixture was mixed.

9. Use of the molecular weight matching enhanced composite bone cement of any one of claims 1 to 5 in the preparation of an orthopedic implant material.

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