Polylactic acid / silicon-doped hydroxyapatite composite material for bone fixation devices and preparation method and application thereof

Abstract

The application provides a polylactic acid / silicon-doped hydroxyapatite composite material for bone fixation devices and a preparation method and application thereof. The polylactic acid / silicon-doped hydroxyapatite composite material is prepared by using polylactic acid as a matrix and silicon-doped hydroxyapatite as a reinforcing body through a melt blending method. When the content of the silicon-doped hydroxyapatite is 10%, the composite material has the best thermal stability and mechanical properties (the bending strength is 66.1 MPa); the in-vitro degradation experiment proves that the degradation rate of the composite material can be changed by changing the content of the silicon-doped hydroxyapatite, thereby meeting the requirements of an implant site; in the cytotoxicity experiment, after 10wt% of the silicon-doped hydroxyapatite is added into the polylactic acid, the decrease of the cell survival rate is reduced, which indicates that the addition of the silicon-doped hydroxyapatite improves the cell activity of the polylactic acid composite material.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of biomedical materials, and particularly relates to a polylactic acid / silicon-doped hydroxyapatite composite material for bone fixation devices and a preparation method and application thereof. BACKGROUND

[0002] In the field of biomaterials science, hydroxyapatite is a kind of bioactive material that attracts much attention, and its crystal lattice structure is a close-packed hexagonal type. Under the condition of stable crystal lattice structure, part of the ion sites of hydroxyapatite can be freely replaced, so that calcium ions can be replaced by various metal ions, thereby changing the physical, chemical characteristics of hydroxyapatite and its mechanical properties in vivo and in vitro.

[0003] In the human body, not only metal elements exist, but also a large number of non-metal elements such as silicon elements, fluorine elements and chlorine elements. These non-metal elements also play an important role in the human body and play an important role in regulating the physicochemical properties and biological functions of natural bone tissue. Therefore, these non-metal elements can also be doped into hydroxyapatite to improve its performance.

[0004] Silicon element is an essential trace element in the human body, which affects the development and mineralization of the skeleton and bone function metabolism in the human body. Studies have shown that the absence of silicon elements will lead to abnormal bone development, deformity and tooth development disorders and other serious consequences. When the missing silicon elements are supplemented, the adverse phenomena disappear. Accordingly, it can be inferred that silicon is indispensable in the skeleton. Therefore, it is of great significance to study the influence of introducing silicon elements into hydroxyapatite on the biological functionality of hydroxyapatite in the field of biomedicine.

[0005] The prior art discloses that nano-hydroxyapatite is compounded in polylactic acid to endow the material with osteogenic activity, but there is no application of silicon-doped hydroxyapatite compounded in polylactic acid as a bone repair material. SUMMARY

[0006] In view of the above shortcomings or improvement needs of the prior art, the present application provides a polylactic acid / silicon-doped hydroxyapatite composite material for bone fixation devices and a preparation method and application thereof.

[0007] In order to achieve the above purpose, the present application adopts the following technical solutions:

[0008] In the first aspect, the present application provides a preparation method of a polylactic acid / silicon-doped hydroxyapatite composite material for bone fixation devices, comprising the following steps:

[0009] Mixing polylactic acid and silicon-doped hydroxyapatite to obtain a mixture;

[0010] Placing the mixture in a banbury mixer for melt blending to obtain a composite;

[0011] The composite is first hot-pressed and then cold-pressed to obtain a polylactic acid-silicon-doped hydroxyapatite composite, i.e. a polylactic acid / silicon-doped hydroxyapatite composite for bone fixation devices.

[0012] Preferably, in the step of melt blending the mixture in an internal mixer, the temperature of the internal mixer is controlled to be 180-190°C, the screw rotation speed is controlled to be 110-120 r / min, and the melt blending time is controlled to be 7-10 min.

[0013] Preferably, in the step of first hot-pressing and then cold-pressing the composite, the hot-pressing specifically comprises:

[0014] The composite is preheated at a temperature of 210-220°C for 6-10 min, and then kept at a temperature of 210-220°C and a pressure of 10-12 MPa for 5-10 min.

[0015] Preferably, in the step of first hot-pressing and then cold-pressing the composite, the cold-pressing specifically comprises: keeping the hot-pressed composite at a temperature of 20-25°C and a pressure of 10-12 MPa for 5-10 min.

[0016] Preferably, the mass fraction of the silicon-doped hydroxyapatite in the mixture is 5-20%.

[0017] Preferably, the mass fraction of the silicon-doped hydroxyapatite in the mixture is 10%.

[0018] Preferably, the method for preparing the silicon-doped hydroxyapatite comprises the following steps:

[0019] The calcium salt solution is heated to 65-70°C under an inert atmosphere, and then acetic acid silicon is added to the calcium salt solution; after the acetic acid silicon is completely dissolved, the temperature is raised to 90-95°C to obtain a calcium salt-silicon salt mixed solution;

[0020] The phosphorus salt solution is added dropwise to the calcium salt-silicon salt mixed solution, and after the dropwise addition is completed, the pH of the system is adjusted to 10.8-11.2 to obtain a mixed solution;

[0021] The mixed solution is kept at 90-95°C for 3-4 h, and after the reaction is completed, filtration, washing and drying are performed to obtain the silicon-doped hydroxyapatite.

[0022] Preferably, the method for preparing the calcium salt solution is:

[0023] The calcium nitrate tetrahydrate is added to water to obtain the calcium salt solution; the concentration of the calcium salt solution is 0.5-0.6 mol / L;

[0024] The method for preparing the phosphorus salt solution is:

[0025] Ammonium dihydrogen phosphate dodecahydrate is added into water to obtain a phosphorus salt solution; the concentration of the phosphorus salt solution is 0.05-0.1 mol / L;

[0026] The silicon concentration in the calcium salt-silicon salt mixed solution is 0.01-0.02 mol / L.

[0027] The volume ratio of the calcium salt-silicon salt mixed solution to the phosphorus salt solution is (2-3):(1-2).

[0028] In a second aspect, the application further provides a polylactic acid / silicon-doped hydroxyapatite composite material for bone fixation devices, which is prepared by the preparation method.

[0029] In a third aspect, the application further provides the polylactic acid / silicon-doped hydroxyapatite composite material prepared by the preparation method or the use of the polylactic acid / silicon-doped hydroxyapatite composite material in preparing bone repair materials.

[0030] The polylactic acid / silicon-doped hydroxyapatite composite material for bone fixation devices, the preparation method and the use thereof have the following beneficial effects over the prior art:

[0031] 1. The preparation method of the polylactic acid / silicon-doped hydroxyapatite composite material for bone fixation devices uses polylactic acid as a matrix and silicon-doped hydroxyapatite as a reinforcing body, and prepares polylactic acid-silicon-doped hydroxyapatite composite materials with different formula ratios by using a melt blending method under optimal process conditions. Related characterization proves the successful preparation of polylactic acid-silicon-doped hydroxyapatite. When the content of silicon-doped hydroxyapatite is 10%, the composite material has the best thermal stability and mechanical properties (the bending strength is 66.1 MPa). In addition, under this ratio, the composite material has the lowest decrease rate of bending performance after 20 days of degradation; at the same time, compared with polylactic acid-nano hydroxyapatite composite materials, the polylactic acid-silicon-doped hydroxyapatite composite material has higher bending strength; this is because silicon ions (Si 2+ ) partially replace calcium sites in the hydroxyapatite (HA) crystal lattice, cause lattice distortion, increase the defect density of the crystal, make the combination of polylactic acid and nano hydroxyapatite more compact, and thus make the composite material have better mechanical properties;

[0032] 2. The in vitro degradation experiment proves that the mechanical properties of the polylactic acid-silicon-doped hydroxyapatite composite material can be changed by changing the content of silicon-doped hydroxyapatite. The degradation rate of the composite material can be changed by changing the content of silicon-doped hydroxyapatite, so as to meet the requirements of the implant site; in addition, silicon ions will be released during the degradation process, which can activate the Wnt / β-catenin signaling pathway of osteoblasts and promote the proliferation and differentiation of osteoblasts.

[0033] 3. Cytotoxicity experiment shows that the decrease of cell survival rate is reduced after 10wt% of silicon-doped hydroxyapatite is added into polylactic acid in the cytotoxicity experiment, which indicates that the addition of silicon-doped hydroxyapatite improves the cell activity of polylactic acid composite material. BRIEF DESCRIPTION OF DRAWINGS

[0034] In order to more clearly illustrate the technical solutions of the embodiments of the present application or the prior art, the drawings needed to be used in the following embodiment or prior art description will be briefly introduced. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can also be obtained by those skilled in the art without creative labor on the basis of these drawings.

[0035] Figure 1 The infrared spectrograms of the silicon-doped hydroxyapatite (Si-HA) used in Example 1 and the polylactic acid-silicon-doped hydroxyapatite composite materials with different formula ratios prepared in Examples 1-4 and the polylactic acid material PLA prepared in Comparative Example 1;

[0036] Figure 2 The TG (a) and DTG (b) curve graphs of the polylactic acid-silicon-doped hydroxyapatite composite materials with different formula ratios prepared in Examples 1-4 and the polylactic acid material PLA prepared in Comparative Example 1 at 0-600℃;

[0037] Figure 3 The DSC heating curve (a) and cooling curve (b) graphs of the polylactic acid-silicon-doped hydroxyapatite composite materials with different formula ratios prepared in Examples 1-4 and the polylactic acid material prepared in Comparative Example 1;

[0038] Figure 4 The XRD spectrograms of the silicon-doped hydroxyapatite (Si-HA) used in Example 1 and the polylactic acid-silicon-doped hydroxyapatite composite materials with different formula ratios prepared in Examples 1-4 and the polylactic acid material prepared in Comparative Example 1;

[0039] Figure 5 The bending strength of the polylactic acid-silicon-doped hydroxyapatite composite materials with different formula ratios prepared in Examples 1-4 and the polylactic acid material prepared in Comparative Example 1;

[0040] Figure 6 The bending strength of the polylactic acid material prepared in Comparative Example 1 and the polylactic acid-nano hydroxyapatite composite materials in Comparative Examples 2-5;

[0041] Figure 7 The tensile fracture surface morphology graphs of the polylactic acid-silicon-doped hydroxyapatite composite materials with different formula ratios prepared in Examples 1-4 and the polylactic acid material prepared in Comparative Example 1;

[0042] Figure 8 (a) is the flexural property graph of the different formula ratio of polylactic acid-silicon doped hydroxyapatite composite material after degradation of 0, 5, 10, 20 days; Figure 8 (b) is the Si ion release amount of 10wt% PLA / Si-HA in Example 2 after degradation of 0, 5, 10, 20 days;

[0043] Figure 9 The cell survival rate graph of mouse osteoblasts in the leaching solution of 10wt% PLA / Si-HA in Example 2. DETAILED DESCRIPTION

[0044] The technical solutions in the embodiments of the present application will be clearly and completely described below in combination with the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments of the present application, all other embodiments obtained by those skilled in the art without creative work fall within the scope of the present application.

[0045] In the description of the present application, it should be understood that the orientation or position relationship indicated by terms such as "upper" is based on the orientation or position relationship shown in the drawings, or the orientation or position relationship commonly used when the product of the present application is used, or the orientation or position relationship commonly understood by those skilled in the art, which is only for the convenience of describing the present application and simplifying the description, and does not indicate or imply that the indicated device or element must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as a limitation on the present application.

[0046] The sequence of the following embodiments is not limited as the preferred sequence of the embodiments. In addition, in the description of the present application, the term "comprising" means "including but not limited to". Various embodiments of the present application can exist in the form of a range; it should be understood that the description in the form of a range is only for the convenience and brevity, and should not be understood as a hard limitation on the scope of the present application; therefore, it should be considered that the described range has been specifically disclosed all possible sub-ranges and single values within the range. For example, it should be considered that the range description from 1 to 6 has specifically disclosed sub-ranges, such as from 1 to 3, from 1 to 4, from 1 to 5, from 2 to 4, from 2 to 6, from 3 to 6, etc., as well as single numbers within the range, such as 1, 2, 3, 4, 5 and 6, regardless of the range. In addition, whenever a numerical range is indicated in this document, it refers to any cited number (fraction or integer) within the indicated range.

[0047] The embodiment of the present application provides a preparation method of a polylactic acid / silicon doped hydroxyapatite composite material for bone fixation instrument, which comprises the following steps:

[0048] mixing polylactic acid and silicon-doped hydroxyapatite to obtain a mixture;

[0049] melting and blending the mixture in an internal mixer to obtain a composite;

[0050] first hot-pressing and then cold-pressing the composite to obtain a polylactic acid-silicon-doped hydroxyapatite composite, which is a polylactic acid / silicon-doped hydroxyapatite composite for bone fixation devices.

[0051] In some embodiments, in the step of melting and blending the mixture in an internal mixer, the temperature of the internal mixer is controlled to be 180-190℃, the screw rotation speed is controlled to be 110-120r / min, and the melting and blending time is controlled to be 7-10min.

[0052] In some embodiments, in the step of first hot-pressing and then cold-pressing the composite, the hot-pressing specifically comprises:

[0053] preheating the composite at a temperature of 210-220℃ for 6-10min, and then keeping the temperature at 210-220℃ and the pressure at 10-12MPa for 5-10min.

[0054] In some embodiments, in the step of first hot-pressing and then cold-pressing the composite, the cold-pressing specifically comprises: keeping the hot-pressed composite at a temperature of 20-25℃ and a pressure of 10-12MPa for 5-10min.

[0055] In some embodiments, the mass fraction of the silicon-doped hydroxyapatite in the mixture is 5-20%.

[0056] In some embodiments, the mass fraction of the silicon-doped hydroxyapatite in the mixture is 10%.

[0057] In some embodiments, the method for preparing the silicon-doped hydroxyapatite comprises the following steps:

[0058] S1, heating a calcium salt solution to 65-70℃ under an inert atmosphere, then adding silicon acetate to the calcium salt solution, heating to 90-95℃ after the silicon acetate is completely dissolved, to obtain a calcium salt-silicon salt mixed solution;

[0059] adding a phosphorus salt solution dropwise to the calcium salt-silicon salt mixed solution, adjusting the pH of the system to 10.8-11.2 after the dropwise addition is completed, to obtain a mixed solution;

[0060] S2, keeping the mixed solution at 90-95℃ for 3-4h, after the reaction is completed, filtering, washing, and drying to obtain the silicon-doped hydroxyapatite.

[0061] In some embodiments, the preparation method of the calcium salt solution is:

[0062] The calcium salt solution is prepared by adding calcium nitrate tetrahydrate into water, and the concentration of the calcium salt solution is 0.5-0.6 mol / L.

[0063] The preparation method of the phosphorus salt solution is as follows:

[0064] The phosphorus salt solution is prepared by adding ammonium dihydrogen phosphate dodecahydrate into water, and the concentration of the phosphorus salt solution is 0.05-0.1 mol / L.

[0065] The concentration of silicon in the calcium salt-silicon salt mixed solution is 0.01-0.02 mol / L.

[0066] The volume ratio of the calcium salt-silicon salt mixed solution to the phosphorus salt solution is (2-3):(1-2).

[0067] In some embodiments, the inert atmosphere includes at least one of nitrogen, helium, neon, and argon.

[0068] Preferably, in some embodiments, the preparation method of the silicon-doped hydroxyapatite includes the following steps:

[0069] S1, the calcium salt solution is transferred to a three-neck reaction flask under nitrogen protection, a magnetic stirrer is added, and nitrogen is introduced to remove oxygen; an oil bath is used to heat to 65-70℃, and silicon acetate is added and stirred until completely dissolved; the temperature is raised to 90-95℃, and the phosphorus salt solution is added dropwise through a separatory funnel at a rate of 1-2 drops per second; the pH of the system is adjusted to 11±0.2 in real time (titrated with ammonia water (5wt%) and verified with alkaline pH test paper), and a mixed solution is obtained to prevent local supersaturation and cause heterogeneous nucleation;

[0070] S2, the reaction system is closed, the reaction temperature is maintained at 90-95℃, and the stirring is continued for 3-4 hours to ensure the directional growth of the crystals;

[0071] S3, after the reaction is completed, the reaction solution is allowed to settle overnight, and then filtered through a Buchner funnel (0.22μm filter membrane); the product is washed with deionized water for 3 times (the amount of washing liquid is 3 times the volume of the product); after ultrasonic assisted purification (ultrasonic treatment at 40kHz for 10-15min), the product is filtered again to remove residual impurities; and the product is dried at 80℃ under vacuum overnight, ground, and then the silicon-doped hydroxyapatite powder without agglomeration is obtained.

[0072] In some embodiments, before the polylactic acid and the zinc-doped silicon-doped hydroxyapatite are mixed, the polylactic acid and the zinc-doped silicon-doped hydroxyapatite are respectively dried at a temperature of 40-50℃ for 10-15h.

[0073] Based on the same inventive concept, the application also discloses a polylactic acid / silicon-doped hydroxyapatite composite material for bone fixation devices, which is prepared by the above preparation method.

[0074] Based on the same inventive concept, the application further discloses a polylactic acid / silicon-doped hydroxyapatite composite material for bone fixation devices prepared by the preparation method and application of the polylactic acid / silicon-doped hydroxyapatite composite material in preparing bone repair materials.

[0075] The polylactic acid / silicon-doped hydroxyapatite composite material for bone fixation devices, the preparation method and the application thereof are further illustrated in the following specific examples. This part further illustrates the content of the application in combination with specific examples, but should not be understood as a limitation of the application. Unless otherwise specified, the technical means adopted in the examples are conventional means familiar to those skilled in the art. Unless otherwise specified, the reagents, methods and equipment adopted in the application are conventional reagents, methods and equipment in the art.

[0076] In the following examples, the preparation method of the silicon-doped hydroxyapatite comprises the following steps:

[0077] S1, the calcium salt solution is transferred to a three-neck reaction bottle under nitrogen protection, a magnetic stirrer is added, and nitrogen is introduced to remove oxygen; an oil bath is used for heating to 65℃, acetic acid silicon is added, stirring is performed until complete dissolution, the temperature is raised to 90℃, and a calcium salt silicon salt mixed solution is obtained; the phosphorus salt solution is added to the obtained calcium salt silicon salt mixed solution at a rate of 1 drop per second through a separatory funnel; the pH of the system is adjusted to 11 for titration in real time to prevent local supersaturation from causing heterogeneous nucleation, and a mixed solution is obtained;

[0078] S2, the reaction system is closed, the reaction temperature is maintained at 90℃, and stirring is continued for 3 hours to ensure directional growth of the crystals;

[0079] S3, after the reaction is completed, the reaction solution is allowed to settle overnight, and then suction filtration is performed through a Buchner funnel (0.22 μm filter membrane), and the reaction solution is washed with deionized water for 3 times (the amount of the washing solution is 3 times the volume of the product); after ultrasonic-assisted purification (ultrasonic treatment at 40 kHz for 10-15 min), secondary suction filtration is performed to remove residual impurities; vacuum drying is performed at 80℃ overnight, and then the agglomerated silicon-doped hydroxyapatite powder is obtained after grinding. Preferably, the preparation method of the calcium salt solution is as follows:

[0080] Calcium nitrate tetrahydrate is added to water to obtain a calcium salt solution; the concentration of the calcium salt solution is 0.5 mol / L;

[0081] The preparation method of the phosphorus salt solution is as follows:

[0082] Ammonium dihydrogen phosphate dodecahydrate is added to water to obtain a phosphorus salt solution; the concentration of the phosphorus salt solution is 0.05 mol / L;

[0083] The silicon concentration in the calcium salt silicon salt mixed solution is 0.01 mol / L;

[0084] The volume ratio of the calcium salt silicon salt mixed solution to the phosphorus salt solution is 2:1.

[0085] The silicon element in the silicon-doped hydroxyapatite prepared above accounts for 0.8% in mass fraction in the silicon-doped hydroxyapatite.

[0086] In the following comparative example, the preparation method of the nano-hydroxyapatite comprises the following steps:

[0087] S1, transfer the phosphorus salt solution to a three-necked reaction bottle under nitrogen protection, add a magnetic stirrer, and introduce nitrogen to remove oxygen; heat to 80℃ using an oil bath, and add the calcium salt solution at a rate of 1 drop per second using a constant flow pump; adjust the pH of the system to 9.0 in real time to obtain a mixed solution;

[0088] S2, add the sodium polyacrylate dispersant to the mixed solution, and the addition amount is 1% of the mass of the mixed solution, while ultrasonic assisted dispersion (ultrasonic at 40 kHz for 5 min); maintain the reaction temperature at 80℃ for 3 hours to ensure directional growth of the crystals;

[0089] S3, after the reaction is completed, the reaction solution is precipitated overnight, and then filtered through a Buchner funnel (0.22 μm filter membrane) and washed with deionized water for 3 times; after ultrasonic assisted purification (ultrasonic at 40 kHz for 10-15 min), the second filtration is performed to remove residual impurities; vacuum drying at 80℃ overnight, and then grinding to obtain non-agglomerated nano-hydroxyapatite powder;

[0090] The preparation method of the calcium salt solution is as follows:

[0091] Add calcium nitrate tetrahydrate to water to obtain a calcium salt solution; the concentration of the calcium salt solution is 0.11 mol / L;

[0092] The preparation method of the phosphorus salt solution is as follows:

[0093] Add ammonium dihydrogen phosphate dodecahydrate to water to obtain a phosphorus salt solution; the concentration of the phosphorus salt solution is 0.06 mol / L;

[0094] The dispersant is sodium polyacrylate;

[0095] The volume ratio of the calcium salt solution to the phosphorus salt solution is 1:1.

[0096] Example 1

[0097] The application embodiment provides a preparation method of a polylactic acid / silicon-doped hydroxyapatite composite material for bone fixation devices, which comprises the following steps:

[0098] S1, respectively dry polylactic acid and silicon-doped hydroxyapatite at a temperature of 40℃ for 12h;

[0099] Dry polylactic acid and silicon-doped hydroxyapatite (Si-HA) are mixed to obtain a mixture; wherein the mass fraction of the silicon-doped hydroxyapatite in the mixture is 5%, and the mass fraction of the polylactic acid is 95%;

[0100] S2, the mixture is placed in an internal mixer and melt blended at 180℃ and a screw rotation speed of 110r / min for 7min to obtain a composite;

[0101] S3, the composite is first hot-pressed and then cold-pressed to obtain a polylactic acid-silicon-doped hydroxyapatite composite (denoted as 5wt%PLA / Si-HA), which is a polylactic acid / silicon-doped hydroxyapatite composite material for bone fixation devices;

[0102] In the step of first hot-pressing and then cold-pressing the composite, the hot-pressing specifically includes:

[0103] The composite is preheated at a temperature of 210℃ for 6min, and then pressure-maintained at a temperature of 210℃ and a pressure of 10MPa for 5min;

[0104] The cold-pressing specifically includes: pressure-maintaining the hot-pressed composite at a temperature of 25℃ and a pressure of 10MPa for 5min.

[0105] Example 2

[0106] The preparation method of the polylactic acid / silicon-doped hydroxyapatite composite material for bone fixation devices provided in the embodiments of the present application is the same as that in Example 1, except that the mass fraction of the silicon-doped hydroxyapatite in the mixture is 10%, and the mass fraction of the polylactic acid is 90%, and the prepared polylactic acid-silicon-doped hydroxyapatite composite material is denoted as 10wt%PLA / Si-HA.

[0107] Example 3

[0108] The preparation method of the polylactic acid / silicon-doped hydroxyapatite composite material for bone fixation devices provided in the embodiments of the present application is the same as that in Example 1, except that the mass fraction of the silicon-doped hydroxyapatite in the mixture is 15%, and the mass fraction of the polylactic acid is 85%, and the prepared polylactic acid-silicon-doped hydroxyapatite composite material is denoted as 15wt%PLA / Si-HA.

[0109] Example 4

[0110] The preparation method of the polylactic acid / silicon-doped hydroxyapatite composite material for bone fixation devices provided in the embodiments of the present application is the same as that in Example 1, except that the mass fraction of the silicon-doped hydroxyapatite in the mixture is 20%, and the mass fraction of the polylactic acid is 80%, and the prepared polylactic acid-silicon-doped hydroxyapatite composite material is denoted as 20wt%PLA / Si-HA.

[0111] Comparative Example 1

[0112] The comparative example provides a preparation method of a polylactic acid material, which is the same as example 1, except that no silicon-doped hydroxyapatite is added, and the specific preparation process is as follows:

[0113] S1, dry the polylactic acid at a temperature of 40°C for 12h;

[0114] Put the dried polylactic acid into an internal mixer and melt blend at 180°C and a screw speed of 110r / min for 7min to obtain a composite;

[0115] S2, first heat press and then cold press the composite to obtain a polylactic acid material (denoted as PLA);

[0116] In the step of first heat pressing and then cold pressing the composite, the heat pressing specifically includes:

[0117] Preheat the composite at a temperature of 210°C for 6min, and then press at a temperature of 210°C and a pressure of 10MPa for 5min;

[0118] The cold pressing specifically includes: press the heat pressed composite at a temperature of 25°C and a pressure of 10MPa for 5min.

[0119] Comparative example 2

[0120] The comparative example provides a preparation method of a polylactic acid-nano hydroxyapatite composite material, which includes the following steps:

[0121] S1, dry the polylactic acid and nano hydroxyapatite at a temperature of 40°C for 12h, respectively;

[0122] Mix the dried polylactic acid (PLA, CAS number: 26100-51-6) and nano hydroxyapatite (nHA) to obtain a mixture; wherein the mass fraction of nano hydroxyapatite in the mixture is 5%, and the mass fraction of polylactic acid is 95%;

[0123] S2, put the mixture into an internal mixer and melt blend at 180°C and a screw speed of 110r / min for 7min to obtain a composite;

[0124] S3, first heat press and then cold press the composite to obtain a polylactic acid-nano hydroxyapatite composite material (denoted as 5wt%PLA / nHA);

[0125] In the step of first heat pressing and then cold pressing the composite, the heat pressing specifically includes:

[0126] Preheat the composite at a temperature of 210°C for 6min, and then press at a temperature of 210°C and a pressure of 10MPa for 5min;

[0127] The cold-pressing specifically includes: keeping the compound after hot-pressing at a temperature of 25°C and a pressure of 10 MPa for 5 min.

[0128] Comparative Example 3

[0129] The present comparative example provides a preparation method of a polylactic acid-nano hydroxyapatite composite material. The same as Comparative Example 2, the difference is that the mass fraction of nano hydroxyapatite in the mixture is 10%, and the mass fraction of polylactic acid is 90%. The prepared polylactic acid-nano hydroxyapatite composite material is recorded as 10wt%PLA / nHA.

[0130] Comparative Example 4

[0131] The present comparative example provides a preparation method of a polylactic acid-nano hydroxyapatite composite material. The same as Comparative Example 2, the difference is that the mass fraction of nano hydroxyapatite in the mixture is 15%, and the mass fraction of polylactic acid is 85%. The prepared polylactic acid-nano hydroxyapatite composite material is recorded as 15wt%PLA / nHA.

[0132] Comparative Example 5

[0133] The present comparative example provides a preparation method of a polylactic acid-nano hydroxyapatite composite material. The same as Comparative Example 2, the difference is that the mass fraction of nano hydroxyapatite in the mixture is 20%, and the mass fraction of polylactic acid is 80%. The prepared polylactic acid-nano hydroxyapatite composite material is recorded as 20wt%PLA / nHA.

[0134] Performance characterization

[0135] Figure 1 The infrared spectrograms of the silicon-doped hydroxyapatite (Si-HA) used in Example 1 and the polylactic acid-silicon-doped hydroxyapatite composite materials of different formula ratios prepared in Examples 1-4, and the polylactic acid material PLA prepared in Comparative Example 1.

[0136] It can be seen from Figure 1 that in the infrared spectrogram of the pure polylactic acid material PLA prepared in Comparative Example 1, 1759cm -1 and 1185cm -1 are the stretching vibrations of C=O and C-O-C groups, indicating that there are ester bonds in the polylactic acid molecules. The absorption peaks at 2944cm -1 and 2995cm -1 correspond to the stretching vibrations of C-H and -CH3. In the infrared spectrogram of the silicon-doped hydroxyapatite (Si-HA), at 563cm -1 and 605cm -1The absorption peak at 3430 cm⁻¹ is a characteristic peak of the phosphate γ⁴ vibrational mode, and the absorption peak at 3430 cm⁻¹ is a characteristic peak of the hydroxyl group. The incorporation of silicon did not affect the functional groups of nano-hydroxyapatite. In contrast, the infrared spectra of the polylactic acid-silicon-doped hydroxyapatite composites in Examples 1-4, compared with silicon-doped hydroxyapatite and polylactic acid, show that the composites possess all the characteristic peaks of silicon-doped hydroxyapatite and polylactic acid, and the peak positions are not significantly shifted. This indicates that no chemical reaction occurred between polylactic acid and silicon-doped hydroxyapatite, only physical blending.

[0137] Figure 2 The graphs show the TG(a) and DTG(b) curves of polylactic acid-silicon doped hydroxyapatite composite materials prepared in Examples 1-4 with different formulation ratios, and the polylactic acid material PLA prepared in Comparative Example 1, at 0-600℃.

[0138] Depend on Figure 2 It can be seen that the samples exhibit certain thermal stability in the initial testing range of 100-300℃. For pure polylactic acid material, the temperature corresponding to a 5wt% mass loss is 303.8℃, and the temperature of the composite material increases with the increase of silicon-doped hydroxyapatite content. 5％ The values ​​showed a trend of first increasing and then decreasing, specifically 328.2℃, 331.2℃, 329.9℃, and 315.3℃. This is because the addition of silicon-doped hydroxyapatite acts as a nucleating agent, promoting the crystallization of polylactic acid (PLA) and making it less prone to molecular chain migration at high temperatures, thus improving its thermal stability. When the content of silicon-doped hydroxyapatite is too high, agglomeration occurs within the PLA, worsening its interfacial compatibility with the PLA matrix and leading to microcracks or voids at the interface. These defects reduce the thermal stability of the PLA matrix. The maximum thermogravimetric temperature (TGA) did not differ significantly among the samples, indicating that silicon-doped hydroxyapatite did not alter the kinetics of the PLA decomposition reaction.

[0139] When the test temperature reached 600℃, the polylactic acid matrix completely decomposed thermally, leaving only silicon-doped hydroxyapatite particles that were difficult to decompose thermally. Therefore, the final remaining amount of the sample can be regarded as the actual composite amount of silicon-doped hydroxyapatite. The remaining amounts of each group were 0%, 4.1%, 9.2%, 14.2%, and 19.4%, respectively, which are close to the theoretical parameters of the raw material ratio in Table 1. This indicates that during the melt blending process of polylactic acid-silicon-doped hydroxyapatite composite material, silicon-doped hydroxyapatite was successfully incorporated into polylactic acid with little loss.

[0140] Figure 3 The heating curves (a) and cooling curves (b) of the polylactic acid-silicon-doped hydroxyapatite composite materials with different formulation ratios prepared in Examples 1 to 4, and the polylactic acid material prepared in Comparative Example 1 are shown.

[0141] From Figure 3 The heating curve of (a) shows that the T g In the range of 65-70℃, the T g (glass transition temperature) of the composite materials did not change substantially. This indicates that no chemical reaction occurred between the silicon-doped hydroxyapatite and the polylactic acid, and that the nanometer hydroxyapatite only existed as a physical filler, without changing the movement ability of the polylactic acid molecular chain, which is consistent with the infrared test results.

[0142] The crystallization transition temperature of pure polylactic acid was 102.7℃, and the melting transition temperature was 168.5℃. As the content of silicon-doped hydroxyapatite increased, the T cc (crystallization transition temperature) of the composite materials gradually shifted to the left, indicating that the addition of silicon-doped hydroxyapatite improved the nucleation efficiency of polylactic acid, which may be because the silicon doping served as a heterogeneous nucleation site, inducing heterogeneous nucleation of polylactic acid.

[0143] Figure 4 XRD spectra of the silicon-doped hydroxyapatite (Si-HA) used in Example 1 and the polylactic acid-silicon-doped hydroxyapatite composite materials of different formulations prepared in Examples 1-4, as well as the polylactic acid material prepared in Comparative Example 1.

[0144] Polylactic acid is a semi-crystalline polymer, and its characteristic peak usually appears at 2θ = 16.8°. From Figure 4 It can be seen from the XRD spectrum that the XRD spectrum of pure polylactic acid has a very wide peak at 2θ = 16.8°, and is in a symmetrical state, indicating that both crystalline and amorphous regions exist at this point, which is consistent with its crystallization characteristics. When the added silicon-doped hydroxyapatite is 15wt%, a new characteristic peak appears near 2θ = 16.8° in the composite material, indicating that a certain amount of silicon-doped hydroxyapatite can cause polylactic acid to transition to a crystalline state. This may be because when the content of silicon-doped hydroxyapatite is too low, it is difficult to play a nucleating agent role. When the content of silicon-doped hydroxyapatite is too high, the ions agglomerate, the crystallization sites are unstable, and the crystallization of polylactic acid is hindered.

[0145] The diffraction peaks of the silicon-doped hydroxyapatite microparticles matched with the standard card (JCPDS 74-0566) of hydroxyapatite, and had the characteristic diffraction peaks of (002), (211), (300), (130) and the like. When the silicon-doped hydroxyapatite was added into the pure polylactic acid, the characteristic peaks of the silicon-doped hydroxyapatite appeared in the XRD spectrum of the composite material, and the intensity of the corresponding peaks of the composite material showed an increasing trend with the increase of the content of the silicon-doped hydroxyapatite, indicating that the silicon-doped hydroxyapatite was successfully mixed into the polylactic acid composite material in the process of melt blending of the polylactic acid and the silicon-doped hydroxyapatite, and corresponded to the formula ratio, which was consistent with the result of the thermogravimetric test.

[0146] Figure 5 The bending strength of the polylactic acid-silicon-doped hydroxyapatite composite materials with different formula ratios prepared in Examples 1-4 and the polylactic acid material prepared in Comparative Example 1. Figure 5 In the table, 1, 2, 3, 4, 5 represent PLA in Comparative Example 1, 5wt% PLA / Si-HA in Example 1, 10wt% PLA / Si-HA in Example 2, 15wt% PLA / Si-HA in Example 3, and 20wt% PLA / Si-HA in Example 4, respectively.

[0147] Figure 6 The bending strength of the polylactic acid-silicon-doped hydroxyapatite composite materials with different formula ratios prepared in Examples 1-4 and the polylactic acid material prepared in Comparative Example 1. Figure 6 In the table, 1, 2, 3, 4, 5 represent PLA in Comparative Example 1, 5wt% PLA / Si-HA in Example 1, 10wt% PLA / Si-HA in Example 2, 15wt% PLA / Si-HA in Example 3, and 20wt% PLA / Si-HA in Example 4, respectively.

[0148] In the table, 1, 2, 3, 4, 5 represent PLA in Comparative Example 1, 5wt% PLA / Si-HA in Example 1, 10wt% PLA / Si-HA in Example 2, 15wt% PLA / Si-HA in Example 3, and 20wt% PLA / Si-HA in Example 4, respectively.

[0149] From the above results, it can be seen that the bending strength of the polylactic acid-silicon-doped hydroxyapatite composite material is higher than that of the polylactic acid material, and the bending strength of the polylactic acid-silicon-doped hydroxyapatite composite material increases with the increase of the content of the silicon-doped hydroxyapatite. Figure 5It can be seen that the bending strength of pure polylactic acid is 63.3 MPa. After adding silicon-doped hydroxyapatite in polylactic acid, the bending strength of polylactic acid / silicon-doped hydroxyapatite shows a trend of first increasing and then decreasing. When the content of silicon-doped hydroxyapatite increases to 10 wt%, the bending strength reaches a maximum of 66.1 MPa, which is higher than that of pure polylactic acid. The above change is explained as follows: due to the poor interfacial bonding between polylactic acid and silicon-doped hydroxyapatite, when the content of silicon-doped hydroxyapatite is too low, the interfacial bonding between polylactic acid and silicon-doped hydroxyapatite may not be sufficient, which reduces the transmission efficiency of stress in the material. Poor interfacial bonding makes the composite material more prone to delamination or fracture under external force. When the content of silicon-doped hydroxyapatite is too high, silicon-doped hydroxyapatite will agglomerate in the polylactic acid matrix, which increases the defects in the polylactic acid material. These defects will act as stress concentration points, which will easily cause the material to break under stress.

[0150] From Figure 6 It can be seen that after the nano-hydroxyapatite is compounded in the polylactic acid, the bending strength of the composite material shows a trend of first increasing and then decreasing. When the content of nano-hydroxyapatite is 10 wt%, the bending strength of the composite material reaches a maximum of 63.6 MPa, which is slightly higher than that of pure polylactic acid. The above change is explained as follows: due to the poor compatibility between polylactic acid and nano-hydroxyapatite, when the content of nano-hydroxyapatite composite is too low, the interfacial bonding between polylactic acid and nano-hydroxyapatite may not be sufficient, which reduces the transmission efficiency of stress in the material. Poor interfacial bonding makes the composite material more prone to delamination or fracture under external force. When the content of nano-hydroxyapatite is too high, nano-hydroxyapatite will agglomerate in the polylactic acid matrix, which increases the defects in the polylactic acid material. These defects will act as stress concentration points, which will easily cause the material to break under stress.

[0151] Further, from Figure 5 and Figure 6 It can be seen that the bending strength of the polylactic acid-silicon-doped hydroxyapatite composite material is higher than that of the polylactic acid-nano-hydroxyapatite composite material and pure polylactic acid. Specifically, compared with the bending strength of pure polylactic acid, which is 63.3 MPa, the bending strength is increased to 66.1 MPa (an increase of 4.42%). Compared with the bending strength of the polylactic acid-nano-hydroxyapatite composite material, which is 63.6 MPa, the bending strength is increased to 66.1 MPa (an increase of 3.93%). The polylactic acid-silicon-doped hydroxyapatite composite material of the present application has better mechanical properties than pure polylactic acid and the polylactic acid-nano-hydroxyapatite composite material. The performance improvement mechanism is: lattice strengthening effect: silicon ions (Si 2+)partially replace the calcium sites in the hydroxyapatite (HA) lattice, induce lattice distortion, increase the crystal defect density, make the combination of polylactic acid and nano-hydroxyapatite more closely, and thus make the composite material have better mechanical properties.

[0152] Figure 7 The tensile fracture surface morphology of the polylactic acid-silicon-doped hydroxyapatite composite materials prepared in Examples 1-4 and the polylactic acid material prepared in Comparative Example 1; wherein (a) is PLA in Comparative Example 1, (b) is 5wt% PLA / Si-HA in Example 1, (c) is 10wt% PLA / Si-HA in Example 2, (d) is 15wt% PLA / Si-HA in Example 3, and (e) is 20wt% PLA / Si-HA in Example 4.

[0153] From the morphology of Figure 7 It can be seen from the morphology that the pure polylactic acid fracture surface is flat; after the addition of silicon-doped hydroxyapatite, the composite material fracture surface is ladder-shaped, all of which are consistent with the characteristics of brittle fracture. In the polylactic acid / silicon-doped hydroxyapatite composite material with a silicon-doped hydroxyapatite content of 10wt%, the fracture surface is rougher than that of pure polylactic acid, indicating that the silicon-doped hydroxyapatite is uniformly dispersed in the polylactic acid, and the interface between the silicon-doped hydroxyapatite and the polylactic acid is well combined. When the silicon-doped hydroxyapatite content increases to 15wt%, the agglomerates of silicon-doped hydroxyapatite particles can be observed on the tensile fracture surface, which may be due to the high content of fillers, causing the silicon-doped nano-hydroxyapatite particles to easily agglomerate. The inorganic-organic interface bonding state directly affects the mechanical properties of the composite material. The agglomerates of silicon-doped hydroxyapatite may reduce its ability to transfer load as a reinforcing phase, thereby leading to a decrease in the mechanical properties of the composite material. In addition, when the silicon-doped hydroxyapatite content is 20wt%, the fracture surface of the composite material has filamentous fibers, which may be due to the uneven stress distribution inside the composite material when it is subjected to external force, causing the first yield in some areas and thus forming these elongated fibrous structures.

[0154] In Vitro Degradation Analysis of Polylactic Acid-Silicon-Doped Hydroxyapatite Composite Material

[0155] In actual bone tissue engineering applications, when the scaffold degrades in the human body, new bone tissue also grows and develops continuously, gradually replacing the degraded part and playing a supporting role. The most ideal state is that the degradation rate of the scaffold can correspond to the growth rate of the bone tissue. Therefore, in vitro degradation experiments are needed to evaluate the applicability of polylactic acid-silicon-doped hydroxyapatite composite materials in the field of bone repair.

[0156] Specifically, the pure polylactic acid (PLA) prepared in Comparative Example 1 and the polylactic acid-silicon doped hydroxyapatite composite materials prepared in Examples 1-4 with different formulation ratios were placed in 125 mL bottles made of high-density polyethylene containing phosphate buffer solution (pH 7.4±0.1) at a ratio of 1 g / 20 mL. The bottles were placed in a temperature-controlled shaker at (37±1) °C and shaken at 200 r / min. The bending properties of the materials were then tested at 0 days, 5 days (120 h), 10 days, and 20 days.

[0157] Figure 8 (a) Graphs showing the flexural properties of polylactic acid-silicon-doped hydroxyapatite composites with different formulation ratios after 0, 5, 10, and 20 days of degradation (flexural strength was tested according to GB / T 9341-2000 standard). 1, 2, 3, 4, and 5 represent PLA in Comparative Example 1, 5 wt% PLA / Si-HA in Example 1, 10 wt% PLA / Si-HA in Example 2, 15 wt% PLA / Si-HA in Example 3, and 20 wt% PLA / Si-HA in Example 4, respectively.

[0158] according to Figure 8 Data from (a) shows that after 20 days of degradation, the flexural strength of the polylactic acid (PLA) material decreased from 62.1 MPa (this 62.1 MPa and the 63.3 MPa mentioned above are from two experiments conducted using the method in Comparative Example 1; the data inconsistency between the two experiments is due to errors) to 57.8 MPa, a decrease of 6.9%. Meanwhile, the flexural strength of the composites with silicon-doped hydroxyapatite contents of 5 wt%, 10 wt%, 15 wt%, and 20 wt% decreased by 7.5%, 6.1%, 7.3%, and 9.6% respectively after 20 days, showing a trend of first increasing and then decreasing. The composite material maintained optimal flexural performance after degradation when the nano-hydroxyapatite content was 10%. Furthermore, it was observed that the rate of decrease in flexural performance of the composite material varied with the nano-hydroxyapatite content, indicating that the degradation rate of PLA can change with the nano-hydroxyapatite content. Therefore, it is possible to modify the degradation rate of the composite material by changing the nano-hydroxyapatite content, thereby meeting the requirements of the implantation site.

[0159] Figure 8(b) The ion release amount of 10wt% PLA / Si-HA in Example 2 after degradation for 0, 5, 10, 20 days, as can be seen from the figure, the composite material will continue to release silicon ions with the increase of degradation time. With the increase of time, the release amount of silicon ions shows a decreasing trend, which may be because the silicon ions released at the beginning are from the silicon-doped hydroxyapatite on the surface of the composite material. When the silicon element in the silicon-doped hydroxyapatite on the surface is depleted, the silicon-doped hydroxyapatite from the inside of the composite material is difficult to release silicon elements due to the blockage of polylactic acid, resulting in a decrease in the release rate of silicon ions.

[0160] Figure 9 The cell survival rate of mouse osteoblasts in the 10wt% PLA / Si-HA extract solution in Example 2 is as follows:

[0161] (1) The polylactic acid and the polylactic acid-silicon-doped hydroxyapatite composite material with a silicon-doped hydroxyapatite content of 10wt% were sterilized using ultraviolet light, and then soaked in a 10mg / 10mL DMEM solution. After 24h, the extract solution was diluted to 0.8mg / mL, 0.5mg / mL, 0.2mg / mL, and 0.1mg / mL.

[0162] (2) 200μL of the above prepared extract solution was added to a 24-well plate (containing 5000 MC3T3 cells per well), and three parallel samples were prepared for each experimental group. The blank group was compared with the fresh culture solution, and the plate was placed in a 37℃ cell incubator for 24h.

[0163] (3) 30μL of MTT liquid was added to each well, and the incubator was continued for 4h. Then 200μL of DMSO culture solution was added, and the shaker was incubated for 15min.

[0164] (4) 100μL of the above liquid was taken from each well of the 24-well plate, and the absorbance value at 492nm was detected.

[0165] (5) The absorbance value of the experimental group was calculated as a ratio of the absorbance value of the blank group, and the cell survival rate was evaluated.

[0166] According to Figure 9The data in the cell can know that the cell survival rate of the polylactic acid-silicon doped hydroxyapatite composite material added with 10wt% silicon doped hydroxyapatite presents a downward trend with the increase of the concentration. In the range of the extraction liquid concentration of 0.1mg / mL-0.8mg / mL, the survival rates of the mouse osteoblasts are 94.0%, 93.3%, 92.9% and 92.2% respectively when the extraction liquid concentrations are 0.1mg / mL, 0.2mg / mL, 0.5mg / mL and 0.8mg / mL respectively. When the concentration is 0.8mg / mL, the composite material still has a survival rate of 92.2%, and the cell survival rate decreases very low. It is shown that the polylactic acid-silicon doped hydroxyapatite has good biocompatibility.

[0167] In summary:

[0168] The polylactic acid-silicon doped hydroxyapatite composite material with different contents of silicon doped hydroxyapatite is prepared by using the melt blending method, and the composite material can be used in the research field of bone repair. The specific conclusions are as follows:

[0169] (1) The polylactic acid-silicon doped hydroxyapatite composite material with different formulations is prepared by using the melt blending method under the best process conditions, taking polylactic acid as the matrix and silicon doped hydroxyapatite as the reinforcing body. The related characterization proves the successful preparation of the polylactic acid-silicon doped hydroxyapatite. When the content of the silicon doped hydroxyapatite is 10%, the composite material has the best thermal stability and mechanical properties (the bending strength is 66.1MPa). In addition, under this ratio, the composite material has the lowest decrease rate of bending performance after 20 days of degradation; at the same time, compared with the polylactic acid-nano hydroxyapatite composite material, the polylactic acid-silicon doped hydroxyapatite composite material has higher tensile strength; this is because the silicon ions (Si 2+ ) partially replace the calcium sites in the hydroxyapatite (HA) crystal lattice, induce lattice distortion, increase the defect density of the crystal, make the combination of polylactic acid and nano hydroxyapatite more closely, and thus make the composite material have better mechanical properties;

[0170] (2) The in vitro degradation experiment proves that the mechanical properties of the polylactic acid-silicon doped hydroxyapatite composite material can be changed by changing the content of the silicon doped hydroxyapatite. The degradation rate of the composite material can be changed by changing the content of the silicon doped hydroxyapatite, so as to meet the requirements of the implanted site; in addition, silicon ions will be continuously released during the degradation process, which can activate the Wnt / β-catenin signal pathway of the osteoblasts and promote the proliferation and differentiation of the osteoblasts.

[0171] (3) The cytotoxicity experiment shows that after 10wt% of the silicon doped hydroxyapatite is added in the polylactic acid, the decrease of the cell survival rate is reduced, which indicates that the addition of the silicon doped hydroxyapatite improves the cell activity of the polylactic acid composite material.

[0172] The above description is only the preferred embodiment of the present application, and is not intended to limit the present application. 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 polylactic acid / silicon-doped hydroxyapatite composite material for a bone fixation device, characterized by, The method comprises the following steps: polylactic acid and silicon-doped hydroxyapatite are mixed to obtain a mixture; the mixture is placed in an internal mixer for melt blending to obtain a composite; the composite is first hot-pressed and then cold-pressed to obtain a polylactic acid-silicon-doped hydroxyapatite composite material, which is a polylactic acid / silicon-doped hydroxyapatite composite material for bone fixation devices; the mass fraction of the silicon-doped hydroxyapatite in the mixture is 5-20%.

2. The method for preparing polylactic acid / silicon-doped hydroxyapatite composite material for bone fixation instruments according to claim 1, wherein, In the step of placing the mixture in the internal mixer for melt blending, the temperature of the internal mixer is controlled to be 180-190°C, the screw rotation speed is controlled to be 110-120 r / min, and the melt blending time is controlled to be 7-10 min.

3. The method of claim 1, wherein the polylactic acid / silicon-doped hydroxyapatite composite material for a bone fixation device is prepared by the steps of: (a) mixing a polylactic acid and a silicon-doped hydroxyapatite; (b) kneading the mixture; (c) extruding the kneaded mixture; (d) molding the extruded mixture; and (e) sintering the molded mixture. In the step of first hot-pressing and then cold-pressing the composite, the hot-pressing specifically comprises: the composite is preheated at a temperature of 210-220°C for 6-10 min, and then pressure-maintained at a temperature of 210-220°C and a pressure of 10-12 MPa for 5-10 min.

4. The method of claim 1, wherein the polylactic acid / silicon-doped hydroxyapatite composite material for a bone fixation device is prepared by the steps of: (a) mixing a polylactic acid and a silicon-doped hydroxyapatite; (b) kneading the mixture; (c) extruding the kneaded mixture; (d) molding the extruded mixture; and (e) sintering the molded mixture. In the step of first hot-pressing and then cold-pressing the composite, the cold-pressing specifically comprises:

5. The method of claim 1, wherein the polylactic acid / silicon-doped hydroxyapatite composite material for a bone fixation device is prepared by the steps of: (a) mixing a polylactic acid and a silicon-doped hydroxyapatite; (b) kneading the mixture; (c) extruding the kneaded mixture; (d) molding the extruded mixture; and (e) sintering the molded mixture. the hot-pressed composite is pressure-maintained at a temperature of 20-25°C and a pressure of 10-12 MPa for 5-10 min.

6. The method of claim 1, wherein the polylactic acid / silicon-doped hydroxyapatite composite material for a bone fixation device is prepared by the steps of: (a) mixing a polylactic acid and a silicon-doped hydroxyapatite; (b) kneading the mixture; (c) extruding the kneaded mixture; (d) molding the extruded mixture; and (e) sintering the molded mixture. The mass fraction of the silicon-doped hydroxyapatite in the mixture is 10%. The preparation method of the silicon-doped hydroxyapatite comprises the following steps: a calcium salt solution is heated to 65-70°C under an inert atmosphere, then silicon acetate is added to the calcium salt solution, the silicon acetate is completely dissolved, the temperature is increased to 90-95°C, and a calcium salt-silicon salt mixed solution is obtained; a phosphorus salt solution is added dropwise to the calcium salt-silicon salt mixed solution, the pH of the system is adjusted to 10.8-11.2 after the dropwise addition is completed, and a mixed solution is obtained; 7. The method of claim 6, wherein the polylactic acid / silicon-doped hydroxyapatite composite material for a bone fixation device is prepared by the steps of: (a) mixing a polylactic acid and a silicon-doped hydroxyapatite; (b) kneading the mixture; (c) extruding the kneaded mixture; (d) molding the extruded mixture; and (e) sintering the molded mixture. the mixed solution is kept at 90-95°C for 3-4 h, after the reaction is completed, filtration, washing and drying are performed to obtain the silicon-doped hydroxyapatite. The preparation method of the calcium salt solution is as follows: calcium nitrate tetrahydrate is added to water to obtain the calcium salt solution; the concentration of the calcium salt solution is 0.5-0.6 mol / L; The preparation method of the phosphorus salt solution is as follows: ammonium dihydrogen phosphate dodecahydrate is added to water to obtain the phosphorus salt solution; the concentration of the phosphorus salt solution is 0.05-0.1 mol / L; the silicon concentration in the calcium salt-silicon salt mixed solution is 0.01-0.02 mol / L; 8. A polylactic acid / silicon-doped hydroxyapatite composite material for a bone fixation device, characterized by, the volume ratio of the calcium salt-silicon salt mixed solution to the phosphorus salt solution is (2-3):(1-2). The silicon-doped hydroxyapatite is prepared by using the preparation method in any one of claims 1-7.

9. The polylactic acid / silicon-doped hydroxyapatite composite material for bone fixation devices prepared by using the preparation method in any one of claims 1-7 or the polylactic acid / silicon-doped hydroxyapatite composite material for bone fixation devices in claim 8 is applied to the preparation of bone repair materials.

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