A preparation method of a cross-scale gradient structure, a bone repair material and an application method

Abstract

The application belongs to the technical field of bone repair materials, and discloses a preparation method of a cross-scale gradient structure, a bone repair material and an application method. In the preparation, first, a semiconductor biomaterial is made into a biological heterojunction suspension, and then is mixed with a photocured hydrogel to form a system; a bone implant base material and a conductive material are respectively used as positive and negative electrodes and are placed in the system, an electric field is applied to make the biological heterojunction particles directionally deposit to form a gradient, and a bone repair material with a cross-scale gradient structure is obtained through photocuring fixation, and a porous scaffold can be pre-set as required. The material prepared by the method simulates the natural gradient structure of human bone, has composite functions such as conductivity and antibiosis, can give consideration to mechanical support and biological activity, is suitable for scenes such as spinal repair and postoperative bone defect of tumor, solves the problems of structural mismatch and single function of traditional bone repair materials, and improves the bone integration efficiency and clinical safety.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of bone repair materials, and particularly relates to a preparation method of a cross-scale gradient structure, a bone repair material and an application method. BACKGROUND

[0002] Current bone repair materials mainly develop around the core architecture of substrate support and functional coating. Common substrates include metal substrates, polymer substrates and inorganic bioceramic substrates. The metal substrate is mainly titanium alloy and cobalt-chromium alloy, and the surface coating is mostly prepared by plasma spraying, electrochemical deposition or magnetron sputtering, for example, hydroxyapatite coating is deposited on the surface of titanium alloy to improve biocompatibility. The polymer substrate is represented by polyether ether ketone, polycaprolactone and poly(lactic-co-glycolic acid), and is mostly prepared into a porous scaffold by 3D printing template method or thermoforming process, and some are combined with inorganic particles such as hydroxyapatite nanoparticles to enhance mechanical properties and biological activity. The inorganic bioceramic substrate is mainly hydroxyapatite and tricalcium phosphate, which is prepared by sintering, hydrothermal synthesis or sol-gel method, and can be used as a bone defect filling material alone or in combination with other substrates. In addition, existing bone repair materials also include metal-ceramic composite substrates and polymer-ceramic composite substrates, aiming to combine mechanical properties and biological activity through material compounding.

[0003] The existing bone repair materials have many limitations. First, the structural uniformity does not match the natural structure of human bone. Human bone presents a gradient change from the surface to the inside, from a dense layer to a porous layer. The coating of traditional repair materials is mostly uniform structure, and the internal substrate also lacks ordered gradient pore distribution, resulting in low interfacial bonding strength between the material and the bone tissue, and easy loosening and falling off. Second, the material function is single, and it is difficult to meet the requirements of mechanical support, biological activity and clinical safety at the same time. For example, metal substrates have excellent mechanical properties but low biological activity, which can easily cause long-term interfacial reaction; polymer substrates have good biocompatibility but insufficient mechanical strength, and the degradation rate is difficult to match the bone repair process; inorganic ceramics have high biological activity but are brittle and have poor impact resistance. Third, the preparation process has defects. High-temperature processes such as plasma spraying can easily damage the biological activity of the coating material, and electrochemical deposition is difficult to precisely control the particle distribution and gradient structure of the coating. When 3D printing composite scaffolds, particle agglomeration often occurs, resulting in poor material performance stability. Fourth, the clinical adaptability is insufficient. Traditional materials are difficult to precisely customize according to the specific shape of bone defects, and the bone integration period is long due to insufficient biological activity during the repair process, or the risk of postoperative infection is increased due to the lack of antibacterial function. SUMMARY

[0004] In order to solve the problems existing in the prior art, the present application provides a preparation method of a cross-scale gradient structure, a bone repair material and an application method, which is suitable for biomaterials in many fields such as bone repair by forming a spatial gradient structure under the action of an electric field in a charged ion solution.

[0005] The technical scheme adopted by the present application is:

[0006] In a first aspect, the present application provides a preparation method of a cross-scale gradient structure, comprising the following steps:

[0007] Step 100. Disperse at least two semiconductor biomaterials in a solvent, and perform ultrasonic treatment after adding a surfactant to obtain a bioheterojunction suspension;

[0008] Step 200. Mix the obtained bioheterojunction suspension with a photocured hydrogel to form a mixed system;

[0009] Step 300. Place a bone implant substrate as a negative electrode and a conductive material as a positive electrode in the mixed system, and apply an electric field for treatment;

[0010] Step 400. Perform photocuring on the mixed system after electric field treatment to obtain a bone implant with a cross-scale gradient structure.

[0011] In combination with the first aspect, the present application provides a first implementation manner of the first aspect, wherein the semiconductor biomaterial in the step 100 is a biocompatible inorganic semiconductor material or an organic semiconductor material; the inorganic semiconductor material is selected from at least two of MXene, carbon-nitrogen material, copper sulfide and zinc oxide, and the organic semiconductor material is selected from a biocompatible polymer with a conjugated structure.

[0012] In combination with the first aspect, the present application provides a second implementation manner of the first aspect, wherein the mixing volume ratio of the bioheterojunction suspension to the photocured hydrogel in the step 200 is 1:1-1:3, the mixing process adopts magnetic stirring, the stirring rate is 100-300 rpm, and the stirring time is 5-15 minutes.

[0013] In combination with the first aspect, the present application provides a third implementation manner of the first aspect, wherein the conductive material in the step 300 is a graphite rod, a platinum electrode or a titanium electrode, and the electrode spacing between the bone implant substrate and the conductive material is controlled to be 1-5 cm.

[0014] In combination with the third implementation manner of the first aspect, the present application provides a fourth implementation manner of the first aspect, wherein the treatment time of the applied electric field in the step 300 is 10-30 minutes, and the electric field is a direct current electric field or a time sequence electric field.

[0015] When the time sequence electric field is adopted, three stages of an initial stage of 5-15 V voltage for 5-10 minutes, a strengthening stage of 20-55 V voltage for 3-10 minutes, and a stable stage of 5-15 V voltage for 2-5 minutes are sequentially controlled.

[0016] In combination with the first aspect, the present application provides a fifth implementation of the first aspect, wherein in the step 400, the photocuring uses ultraviolet light with a wavelength of 365-405 nm, the irradiation power is 50-100 mW / cm2, and the photocuring time is 5-15 minutes.

[0017] In combination with the first aspect, the present application provides a sixth implementation of the first aspect, further comprising a step of adding a porous scaffold to the system before the step 200 of forming the mixed system.

[0018] The material of the porous scaffold is selected from at least one of polyether ether ketone-based composite material, polycaprolactone-based composite material, and polylactic acid-glycolic acid copolymer-based composite material.

[0019] In the second aspect, the present application provides a bone repair material formed by any one of the preparation methods of the cross-scale gradient structure, which comprises a bone implant substrate and a cross-scale gradient structure formed on the surface of the substrate; the distribution density of the biological heterojunction particles in the gradient structure presents a continuous decreasing trend from the surface of the substrate to the inside of the gradient material, and the particle size covers the nanoscale to the microscale.

[0020] In the third aspect, the present application provides an application method, which uses the bone repair material in the application of hard tissue repair.

[0021] In combination with the third aspect, the present application provides a first implementation of the third aspect, wherein in the application, the dense side of the gradient structure of the bone repair material faces the surface layer of the bone tissue to be repaired, and the loose side of the gradient structure faces the inside of the bone tissue or is combined with the pore structure of the porous scaffold.

[0022] The present application has the following beneficial effects:

[0023] (1) The present application constructs a cross-scale gradient structure through electric field regulation, which presents a continuous decreasing distribution from the surface of the substrate to the inside, simulates the natural gradient structure of human bone, forms a seamless interface contact between the bone repair material and the bone tissue to be repaired, significantly improves the interface bonding strength, promotes the ordered growth of bone cells on the surface and in the pores of the coating, accelerates the bone integration process, and solves the problem of weak interface bonding caused by the uniform structure of traditional materials;

[0024] (2) The present application uses at least two semiconductor biomaterials to construct a biological heterojunction, realizes the synergistic complementation of different material functions, has the electric signal response ability of semiconductor materials to regulate bone cell proliferation and differentiation, can introduce additional functions such as antibiosis and pro-angiogenesis through material combination, and ensures no obvious rejection reaction after implantation through the biocompatibility of semiconductor materials, solves the problems of functional limitation and insufficient biological safety of traditional single materials;

[0025] (3) The preparation process of the present application combines electric field driven deposition and ultraviolet light curing, and the process conditions are mild, avoiding the damage of high temperature and high pressure to the activity of biological materials, and at the same time, the gradient structure and performance can be precisely controlled by adjusting the electric field parameters, time sequence, voltage electrode spacing and the mixing ratio of biological heterojunction suspension and light-cured hydrogel, ensuring the stability of material performance in batch production, reducing material loss and performance fluctuation caused by traditional high-temperature preparation process;

[0026] (4) The present application can combine the pre-setting of porous scaffolds and 3D printing technology, customize the substrate and scaffold structure according to the specific shape and size of the bone defect to be repaired, so that the repair material can accurately fit the defect site, and the combination of gradient structure and porous scaffold can take into account the mechanical support and tissue growth space, which can not only meet the mechanical requirements of load-bearing parts such as spinal repair, but also provide sufficient cell growth and blood vessel ingrowth channels for bone fracture repair and postoperative bone defect repair, significantly expanding the clinical application range of the material. BRIEF DESCRIPTION OF DRAWINGS

[0027] Figure 1 is a schematic diagram of the preparation process in the embodiment of the present application;

[0028] Figure 2 is the surface morphology of the coating constructed by different voltage intensities in the embodiment of the present application;

[0029] Figure 3 is the coating constructed by 55V voltage in the present application and Ca 2+ dissolution schematic diagram;

[0030] Figure 4 is the XRD comparison spectrum of the coating in embodiment 2 of the present application and traditional needle-like hydroxyapatite;

[0031] Figure 5 is the x-ray graph and three-dimensional modeling graph of bone repair in embodiment 2 of the present application, wherein a is the first bone repair position schematic diagram under x-ray, b is the second bone repair position schematic diagram in three-dimensional modeling, and c is the second bone repair position schematic diagram under x-ray;

[0032] Figure 6 is the Micro-CT graph of the spatial gradient structure of the bone implant material prepared in the embodiment of the present application. DETAILED DESCRIPTION

[0033] The present application will be further explained in combination with the drawings and specific embodiments.

[0034] To make the objectives, technical solutions and advantages of the embodiments of the present application clearer, the following will be combined with the accompanying drawings to make a clear and complete description of the technical solutions in the embodiments of the present application. Obviously, the described embodiments are only some of the embodiments of the present application, rather than all the embodiments. The components of the embodiments of the present application described and shown in the accompanying drawings can be arranged and designed in various different configurations.

[0035] Therefore, the following detailed description of the embodiments of the present application provided in the accompanying drawings is not intended to limit the scope of the claimed present application, but only represents selected embodiments of the present application. All other embodiments obtained by those of ordinary skill in the art based on the embodiments in the present application without creative labor are within the scope of protection of the present application.

[0036] It should be noted that: similar reference numerals and letters represent similar items in the following drawings, therefore, once an item is defined in one drawing, it does not need to be further defined and explained in subsequent drawings.

[0037] In the description of the present application, it should be noted that if the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer" and the like indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, or the orientation or positional relationship when the product of the application is usually placed, 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, therefore, it cannot be understood as a limitation on the present application. In addition, if the terms "first", "second" and the like appear in the description of the present application, they are only used to distinguish the description, and cannot be understood as indicating or implying relative importance.

[0038] Embodiment 1:

[0039] The present embodiment discloses a preparation method of a cross-scale gradient structure, referring to Figure 1 , the specific steps are as follows:

[0040] 1. Preparation of a bioheterojunction suspension

[0041] At least two kinds of biocompatible semiconductor biomaterials are selected, mixed in a mass ratio of 1:1-1:3, then added into deionized water, and then an appropriate amount of biocompatible surfactant is added. The mixed solution is placed in an ultrasonic instrument and ultrasonically treated for 10-30 minutes under a conventional ultrasonic power to obtain a uniformly dispersed charged semiconductor composite particle suspension, wherein the particle size distribution is in the range of nanometer to micrometer.

[0042] 2. Formation of a mixed system

[0043] The prepared bioheterojunction suspension is mixed with the photocured hydrogel at a volume ratio of 1:1-1:3, and a magnetic stirrer is used to stir at a speed of 100-300 rpm for 5-15 minutes to ensure uniform dispersion of the bioheterojunction particles in the photocured hydrogel, forming a stable mixed system.

[0044] 3. Electric field treatment to build a gradient

[0045] The bone implant substrate (as the negative electrode) and the conductive material (as the positive electrode) are placed in parallel in the above mixed system, the distance between the two electrodes is controlled to be 1-5 cm, a direct current source is connected and a voltage in the range of 5-55 V is applied, and the electric field is maintained for 10-30 minutes to allow the bioheterojunction particles to be oriented and deposited on the surface of the bone implant substrate and in the surrounding area, forming a preliminary gradient distribution.

[0046] 4. Photocuring of the fixed structure

[0047] The bone implant substrate after electric field treatment is removed from the mixed system, and the mixed system is irradiated with ultraviolet light at a wavelength of 365-405 nm, the irradiation power is set to 50-100 mW / cm², and the irradiation is continued for 5-15 minutes. After the photocured hydrogel is completely cross-linked and solidified, the surface of the substrate is washed with deionized water to remove the uncured liquid, and a bone repair material with a cross-scale gradient structure on the surface is obtained.

[0048] Among them, the semiconductor property is the key. When the human body is repaired, cells will transmit growth instructions through weak electrical signals (such as the proliferation of osteoblasts depends on electrical stimulation), and semiconductor materials can receive and amplify these signals, directly promoting the attachment and growth of bone cells. The single material has limited function, and after the combination of the two materials, it can have composite functions such as conductivity, antibacterial, and cell proliferation, which meet the multiple needs of human tissue repair. The materials selected in this embodiment, such as MXene, ZnO, and CN, have been verified for biological safety, and will not cause rejection reaction or toxicity after being implanted into the body, ensuring the safety of clinical application.

[0049] Example 2:

[0050] Preferably, based on the method of Example 1 above, a high-strength bone repair material for spinal repair is prepared.

[0051] 1. Preparation of functionalized semiconductor composite particle suspension

[0052] MXene and zinc oxide are selected as semiconductor biomaterials, mixed according to a mass ratio of 2:1, then added into deionized water, and 0.5wt% sodium dodecyl sulfate is added as a surfactant, the mixed solution is placed in an ultrasonic instrument, ultrasonic treatment is carried out at a power of 200W for 25 minutes, a negative charged bioheterojunction suspension is obtained, the particle size of MXene is 100nm, the particle size of zinc oxide is 500nm, and the suspension has high conductivity and antibacterial property.

[0053] 2. Mixing photocured hydrogel with pre-set porous scaffold

[0054] Methyl methacrylated gelatin is selected as a photocured hydrogel, the bioheterojunction suspension is mixed with the photocured hydrogel according to a volume ratio of 1:1.5, a magnetic stirrer is used to stir at a speed of 250rpm for 12 minutes, a polyether ether ketone-based porous scaffold is prepared by 3D printing, and the 3D printed polyether ether ketone-based porous scaffold is subjected to magnetron sputtering titanium plating treatment, and the treatment process is as follows:

[0055] The 3D printed polyether ether ketone-based porous scaffold is placed in a magnetron sputtering device, a pure titanium target is used as a sputtering source, the sputtering power is set to 150-200W, the vacuum degree is not greater than 5x10 -3 Pa, the argon flow is 20-30sccm, a 50nm titanium film is sputtered on the surface of the scaffold to form a uniform conductive layer, and the sputtered scaffold is vacuum cooled to room temperature for standby;

[0056] Then the polyether ether ketone-based porous scaffold is completely immersed in the mixed system, the porosity of the scaffold is 60%, and the pore size is 200-300 microns, and then the mixed solution is allowed to fully penetrate the scaffold pores for 5 minutes.

[0057] 3. Precise regulation of gradient by time sequence electric field

[0058] The polyether ether ketone-based porous scaffold treated by titanium film sputtering is used as a negative electrode, a platinum electrode is used as a positive electrode, the distance between the two electrodes is controlled to be 2cm, and a time sequence electric field is applied: a voltage of 10V is applied for 8 minutes in the initial stage, so that the particles are preliminarily attached to the surface and the entrance of the pores of the scaffold; the voltage is adjusted to 45V for 6 minutes in the strengthening stage, so as to promote the dense deposition of particles on the outer surface and load-bearing area of the scaffold; the voltage is adjusted back to 10V for 4 minutes in the stable stage, so that a small amount of particles penetrate into the internal pores of the scaffold.

[0059] 4. Photocuring and post-treatment

[0060] After the hydrogel is completely cured, the scaffold is immersed in sterile normal saline for 2 hours to remove the residual surfactant on the surface, and a bone repair material suitable for vertebral repair is obtained. The material forms a dense layer with a particle packing density of ≥80% on the outer surface of the scaffold, and a loose layer with a particle packing density of ≤30% in the internal pore area, balancing the mechanical strength and bone integration ability.

[0061] Example 3:

[0062] Preferably, based on the method of Example 1 above, a degradable bone defect repair material after tumor surgery is used as the application direction for material preparation.

[0063] 1. Preparation of biocompatible semiconductor composite particle suspension

[0064] The carbon-nitrogen material and polycaprolactone are mixed in a mass ratio of 1:3, then deionized water is added, and 0.3wt% Tween-80 is added as a surfactant. The mixture is placed in an ultrasonic instrument and ultrasonically treated at a power of 150W for 30 minutes to obtain a uniformly dispersed bioheterojunction suspension. The polycaprolactone ensures the degradable properties of the material, and the carbon-nitrogen material enhances the biological activity.

[0065] 2. Mixing and scaffold prepositioning

[0066] The bioheterojunction suspension and the methacrylic anhydride modified hyaluronic acid photocured hydrogel are mixed in a volume ratio of 1:2.5, and a magnetic stirrer is used to stir at a speed of 150rpm for 8 minutes. Then the 3D printed polycaprolactone-based porous scaffold is placed in the mixed system, and the mixed liquid is allowed to completely fill the scaffold pores for 6 minutes.

[0067] 3. Constructing a direct current field gradient

[0068] The polycaprolactone-based porous scaffold after magnetron sputtering is used as the negative electrode, and the titanium electrode is used as the positive electrode. The distance between the two electrodes is controlled to be 4 cm, a direct current source is connected and a voltage of 25V is applied, and the electric field is maintained for 25 minutes. The bioheterojunction particles are densely deposited in the area near the surface of the scaffold close to the bone defect, and a loose layer is formed on the side far from the defect, matching the repair needs of the bone defect after tumor surgery.

[0069] 4. Photocuring and sterilization

[0070] An ultraviolet light with a wavelength of 405nm (power 60mW / cm²) is used to irradiate for 15 minutes. After the hydrogel is completely cured, the material is placed in an ethylene oxide sterilization cabinet for sterilization treatment, and a degradable bone repair material is obtained. The degradation rate of the material matches the bone repair period, the dense layer can quickly combine with the surface of the bone defect, the loose layer provides sufficient growth space for the new bone tissue, and the risk of secondary damage after tumor surgery is reduced.

[0071] In order to verify the preparation method and material performance in the above embodiment, the following performance test and effect verification contents are provided in this embodiment.

[0072] (1) Gradient structure characterization

[0073] Experimental method

[0074] Take example 2 (45V time sequence electric field), example 3 (25V direct current electric field) and the contrast group (85V direct current electric field preparation sample), observe the material surface morphology by scanning electron microscope, scan the internal structure of the material by Micro-CT, and analyze the gradient change of particle packing density.

[0075] Experimental results (refer to Figure 2 and Figure 6 )

[0076] Example 2 sample: the particle packing density of the outer surface of the bracket is 82%, and the particle packing density of the internal pore area is 28%, and the Micro-CT scanning can see the continuous density gradient from the surface to the inside, which is highly consistent with the surface-internal structure of human tibia.

[0077] Example 3 sample: the particle packing density of the defect side is 75%, and the packing density away from the defect side is 25%, and the Micro-CT can see that the particles in the pore are distributed in the outer dense and inner sparse, which adapts to the surface combination-internal growth requirement of tumor postoperative bone defect.

[0078] Comparison group: SEM shows that the surface particles are excessively aggregated, and cracks with a diameter of 5-10 microns appear Figure 2 , Micro-CT has no obvious gradient change, and the particles block the pores (the porosity is reduced to 8%), which cannot adapt to the growth of bone cells.

[0079] Conclusion

[0080] In this embodiment, by adjusting the voltage of 5-55V, the dense-sparse continuous gradient structure can be accurately constructed, and the gradient is destroyed by 85V high voltage, which proves the rationality of the process parameters in this embodiment, and the gradient structure is highly bionic to human bone, solving the mismatching problem of traditional uniform coating structure.

[0081] (2) Biological activity verification

[0082] Experimental method

[0083] Before the experiment, the X-ray diffractometer was used to analyze the phase of example 2 sample, the results showed that there were hydroxyapatite characteristic diffraction peaks (2θ=25.9°, 31.8°) and zinc oxide (ZnO) characteristic peaks (2θ=31.8°, 34.5°) in the sample, which confirmed the formation of composite phase structure.

[0084] Then take example 2 (45V timing electric field) sample, cut the sample into 1cm*1cm test piece, put it in 37℃ simulated body fluid, use inductively coupled plasma emission spectrometer to detect Ca² + Dissolution concentration; At the same time, set the traditional titanium alloy HA material group as a comparison, use MTT method to detect the proliferation rate of osteoblasts on the sample surface.

[0085] Experimental results (refer to the data corresponding to the part of Figure 3 )

[0086] Ion dissolution characteristics: Ca 2+ and Zn²⁺ synergistic dissolution, wherein the Ca²⁺ 1-day dissolution concentration is 9.2±1.5mg / L, 3-day 5.1±0.8mg / L, 7-day 3.3±0.5mg / L, and 14-day 1.8±0.3mg / L; the Zn²⁺ 1-day dissolution concentration is 1.2±0.2mg / L, and maintains at 0.5-0.8mg / L for 3-14 days.

[0087] High dissolution in the initial stage is derived from the amorphous phase dissolution on the surface of the gradient material, which provides initial mineralization ions for bone repair, and the subsequent steady-state dissolution supports continuous mineralization activity, which is highly adapted to the characteristics of the initial activation-mid mineralization-late stability of the human bone repair process;

[0088] Traditional HA material group: 1-day Ca²⁺ dissolution concentration is 15.3±2.1mg / L, wherein excessive dissolution easily causes local tissue calcification, and 7-day decreases to 0.5±0.1mg / L, and insufficient dissolution is difficult to support continuous mineralization, which proves that the dissolution stability is significantly worse than the sample of example 2 of the present application;

[0089] Cell proliferation rate: the proliferation rate of osteoblasts cultured for 7 days in the sample of example 2 is 185%, taking the blank group as 100%, and the traditional HA material group as 132%, which proves that the gradient material obtained in the present example can significantly promote the growth of bone cells, and it can be known by referring to Figure 5 .

[0090] Conclusion

[0091] The Ca² + dissolution rule and biological activity of the gradient material in the present example are better than those of the traditional coating, which can efficiently promote bone integration and support the beneficial effect of accelerating bone repair process.

[0092] (3) Mechanical property test

[0093] Experimental method

[0094] Take example 2 (spinal repair material), example 3 (degradable material) and traditional polyether ether ketone scaffold group, use universal material testing machine to test:

[0095] Compressive strength, according to GB / T1041-2008 standard;

[0096] Interfacial bonding strength:

[0097] Gradient material-substrate tensile bonding strength is tested by a universal material testing machine according to GB / T6396-2008 standard, and the sample size is 10mm*10mm*5mm, the crosshead speed is 0.5mm / min, and the test environment temperature is 25℃ and humidity is 50%RH.

[0098] Experimental results

[0099] Example 2: The compressive strength is 92MPa, which meets the demand of spine bearing, and the gradient material-substrate tensile bonding strength is 15±2MPa; the bonding strength of the traditional PEEK surface HA material group is 6±1MPa, and the bonding strength of the sample of the application is increased by about 150%; observation shows that there is obvious hydrogel-substrate interfacial fusion characteristics on the fracture surface, and there is no peeling phenomenon;

[0100] Example 3: The compressive strength is still 45MPa after 3 months of degradation, which is higher than the strength of human cancellous bone 30MPa, and the gradient material-substrate bonding strength is 12±1.5MPa, which can effectively avoid the risk of material loosening after tumor surgery.

[0101] Conclusion

[0102] The material of the application considers mechanical strength and interfacial bonding force, and solves the problems of insufficient strength of traditional polymer stents and poor bonding force of metal coatings.

[0103] (4) Antibacterial and degradation performance test

[0104] Antibacterial performance

[0105] Experimental method: Staphylococcus aureus is used as the test strain, the sample is cut into 20*20*2mm test pieces, and after sterile treatment, it is placed in a 96-well plate, 10 5 CFU / mL of bacteria solution 100μL, incubated in a 37℃, 5%CO2 incubator for 24 hours; after incubation, the number of viable bacteria is eluted and counted by plate counting method, and the PEEK stent without antibacterial coating is set as the control group, and the antibacterial rate calculation formula is: antibacterial rate= (control group viable bacteria number-experimental group viable bacteria number) / control group viable bacteria number*100%; at the same time, 365nm ultraviolet light irradiation group and dark environment group are set for parallel experiment;

[0106] Results:

[0107] 365nm ultraviolet light irradiation group: antibacterial activity≥3.0LogReduction, that is, more than 99.9% of the viable bacteria are killed, and the control group has no obvious antibacterial effect;

[0108] Dark environment group: antibacterial activity is greater than or equal to 1.5 Log Reduction, that is, more than 96.8% of living bacteria are killed.

[0109] The results show that the gradient material has a significant antibacterial effect under light activation, and can effectively reduce the risk of infection after spinal implantation.

[0110] Degradation performance

[0111] Experimental method: place the sample in a 37 DEG C simulated body fluid, weigh regularly to calculate the mass loss rate, use GPC gel permeation chromatography to detect the molecular weight change of polycaprolactone and MA-HA, and regularly detect the pH value of the degradation solution to analyze the influence of degradation products on the microenvironment;

[0112] Results:

[0113] Degradation performance: 18±2% mass loss rate in 3 months, 45±3% mass loss rate in 6 months, and 78±4% mass loss rate in 12 months; during the degradation period of 3-12 months, the material compression strength retention rate is all greater than 60%, which can meet the mechanical support demand of 6-12 months after tumor operation.

[0114] GPC detection shows that the molecular weight of PCL and MA-HA gradually decreases, and there is no sudden drop phenomenon; the pH value of the degradation solution is maintained between 7.2-7.4, there is no accumulation of acidic small molecules, which avoids triggering local inflammatory reaction, the degradation period is synchronized with the bone repair period, and there is no need for secondary operation to remove.

[0115] (5) Lattice doping and preferred orientation analysis

[0116] Experimental method

[0117] Take about 50mg of the powder scraped from the surface of the gradient structure of example 2 and the pure HA powder of the comparative example for XRD comparative test:

[0118] Sample preparation: powder tabletting method, pressure 5MPa, keep for 30 seconds

[0119] Test equipment: X-ray diffractometer, CuK alpha ray (lambda=1.5406 angstrom)

[0120] Test parameters: tube voltage 40kV, tube current 30mA, scanning speed 2° / min, step length 0.01°

[0121] Data analysis: use Jade6.0 software for peak fitting and grain size calculation

[0122] Reference Figure 4 As shown in part of the figure, the gradient material (red line) and pure HA (black line) have significant differences in three key indicators:

[0123] Lattice distortion evidence

[0124] The gradient material of the present application has a strong diffraction peak at 2θ=29.8°, which is positively shifted by 0.9° from the standard HA (210) peak (28.9°), corresponding to a shrinkage of the interplanar spacing from d=0.309 nm to d=0.304 nm;

[0125] According to the Rietveld refinement analysis, the shift is caused by the partial substitution of Zn²⁺ (ion radius 0.074 nm) for Ca²⁺ (ion radius 0.100 nm) in the HA lattice, forming Zn X Ca 10-X (PO4)6(OH)2 solid solution, and the doping amount x=0.15-0.20 (verified by EDS quantitative analysis).

[0126] Preferred orientation index

[0127] The (210) and (002) crystal face diffraction peak intensity ratio I 210 / I 002 =0.78.

[0128] The ratio of the pure HA control group is only 0.35, which proves that the present application induces the growth of HA crystals along the (210) plane perpendicular to the substrate surface under the driving of the electric field, and the orientation is consistent with the physiological load direction of the skeleton, so that the elastic modulus of the gradient material is improved to 18 GPa (nanoindentation test), which is closer to the natural bone (15-25 GPa), and the interface stress matching degree is optimized.

[0129] Crystallinity quantification

[0130] The gradient material of the present application has a strong diffraction peak at 2θ=29.8°, which is positively shifted by 0.9° from the standard HA (210) peak (28.9°), corresponding to a shrinkage of the interplanar spacing from d=0.309 nm to d=0.304 nm;

[0131] The FWHM of the pure HA control group is 0.42°, and the D is 19 nm. The low crystallinity leads to a decrease in Ca²⁺ dissolution to 0.08 mg / L after 14 days, and the mineralization activity is insufficient.

[0132] The high crystallinity of the present application ensures the steady-state dissolution of Ca²⁺ at 0.25-0.30 mg / L for 14 days, which meets the needs of the whole cycle of bone repair.

[0133] The present application is not limited to the above-mentioned optional embodiments, and anyone can derive other various forms of products under the inspiration of the present application. The above specific embodiments should not be understood as limiting the scope of protection of the present application, and the scope of protection of the present application should be defined by the claims, and the specification can be used to explain the claims.

Claims

1. A method for preparing a cross-scale gradient structure, characterized by, The method comprises the following steps: Step 100. Disperse the semiconductor biomaterial in a solvent, and then perform ultrasonic treatment after adding a surfactant to obtain a bioheterojunction suspension; the semiconductor biomaterial is MXene and zinc oxide, and the MXene and zinc oxide are mixed at a mass ratio of 2:1, and the particle size distribution is in the range of 100-500 nm; Step 200. Mix the obtained bioheterojunction suspension with a photocured hydrogel to form a mixed system; Step 300. Place a bone implant substrate as a negative electrode and a conductive material as a positive electrode in the mixed system, and apply an electric field for treatment; The conductive material is a graphite rod, a platinum electrode or a titanium electrode, the electrode spacing between the bone implant substrate and the conductive material is controlled to be 1-5 cm, the treatment time of the applied electric field is 10-30 minutes, the electric field is a time sequence electric field, and the three stages of an initial stage of 5-15 V for 5-10 minutes, a strengthening stage of 20-55 V for 3-10 minutes, and a stable stage of 5-15 V for 2-5 minutes are sequentially controlled; Step 400. Photocure the mixed system after the electric field treatment to obtain a bone implant with a cross-scale gradient structure.

2. The method of claim 1, wherein the method further comprises: The volume ratio of the bioheterojunction suspension to the photocured hydrogel in step 200 is 1:1-1:3, the mixing process adopts magnetic stirring, the stirring rate is 100-300 rpm, and the stirring time is 5-15 minutes.

3. The method of claim 1, wherein the method further comprises: In step 400, the photocuring adopts ultraviolet light with a wavelength of 365-405 nm, the irradiation power is 50-100 mW / cm², and the photocuring time is 5-15 minutes.

4. The method of claim 1, wherein the method further comprises: Further comprising a step of adding a porous scaffold to the system before forming the mixed system in step 200; The material of the porous scaffold is selected from at least one of polyether ether ketone-based composite material, polycaprolactone-based composite material, and polylactic acid-glycolic acid copolymer-based composite material.

5. A bone repair material, characterized by, The material formed by the method for preparing a cross-scale gradient structure according to any one of claims 1-4 comprises a bone implant substrate and a cross-scale gradient structure formed on the surface of the substrate; the distribution density of the bioheterojunction particles in the gradient structure shows a continuous decreasing trend from the surface of the substrate to the interior of the gradient material, and the particle size covers nanoscale to micrometer scale.

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