A porous double-gradient bone scaffold with shape memory effect and a preparation method thereof

Abstract

The application belongs to the technical field of biological materials, and specifically discloses a porous double-gradient bone scaffold with shape memory effect and a preparation method thereof. The porous double-gradient bone scaffold comprises a porous lattice structure with multiple structural layers made of a memory material, internal pores of the porous lattice structure are through, and the porosity of the porous lattice structure presents double-gradient change. The bone scaffold of the application has excellent matching degree with the bone, can well adapt to the porosity and arrangement mode of human cortical bone and cancellous bone, and has shape memory effect, can be compressed before being implanted into a patient's body, effectively reduces the size of the scaffold, only a small incision can be opened at a defect site during a surgery process, shape recovery occurs after being implanted into the human body during the surgery, the size is increased to a shape matching the defect site before compression, and the shape completely matches the defect site.

Description

Technical Field

[0001] This application belongs to the field of biomaterials technology, and more specifically, relates to a porous dual-gradient bone scaffold with shape memory effect and its preparation method. Background Technology

[0002] Bones are the primary support structure for all human activities. Factors such as population aging, trauma, infection, and tumors can cause bone tissue defects. Bones have a certain regenerative capacity and can repair minor injuries, but when the size of bone defects exceeds a certain value, artificial intervention is required, such as implanting a scaffold for repair.

[0003] In related technologies, bone tissue is mainly divided into two parts: cortical bone and cancellous bone. Cortical bone is dense, possessing high strength and density, and bears the main load-bearing function; cancellous bone is highly porous, with a high porosity, accommodating blood vessels, bone cells, etc., and serving as a channel for the transport of nutrients and waste. The porosity and mechanical properties of cortical bone and cancellous bone are different. Currently, traditional synthetic material scaffolds used clinically, such as ceramic materials and traditional medical metal material scaffolds, are large in size and have simple structural designs. During implantation, large incisions need to be made at the site of the defect, resulting in greater trauma to the body. Moreover, the fit between the implanted bone scaffold and the bone is poor, urgently requiring improvement. Summary of the Invention

[0004] In response to the deficiencies or improvement needs of existing technologies, this application provides a porous dual-gradient bone scaffold with shape memory effect and its preparation method, aiming to solve the problems of poor matching between existing bone scaffolds and bones and large surgical wounds.

[0005] This application provides a porous dual-gradient bone scaffold with shape memory effect, comprising a porous lattice structure with multiple structural layers made of memory material, wherein the internal pores of the porous lattice structure are interconnected, and the porosity of the porous lattice structure exhibits a dual-gradient change.

[0006] Compared with existing technologies, the bone scaffold conceived in this application employs a dual-gradient porous lattice structure, which can well adapt to the porosity and arrangement of human cortical and cancellous bone. This allows it to adapt to the human environment and ensure the transport of nutrients to the bone and the repair of defects, promoting growth and repair of the defect sites. Furthermore, this bone scaffold exhibits shape memory effect, allowing for compression before implantation, effectively reducing the scaffold's size. During surgery, only a small incision needs to be made at the defect site. After implantation, the scaffold recovers its shape, increasing in size to match the predetermined shape of the defect site, achieving a perfect fit. This design, by utilizing shape memory effect, effectively reduces surgical incisions and, after implantation, matches irregular defect sites, stimulating bone tissue repair through stress.

[0007] As a further preferred embodiment, the unit cell of the porous lattice structure is a five-mode superstructure composed of double-cone rods, wherein the middle diameter of the double-cone rods is larger than the diameters at both ends.

[0008] As a further preferred embodiment, the matrix structure of the five-mode superstructure is a diamond lattice structure.

[0009] As a further preferred embodiment, the diameters at both ends of the double-cone rod are 0.17mm-0.23mm, and the diameter in the middle is 0.25mm-0.4mm.

[0010] As a further preferred embodiment, in the porous lattice structure, the two ends of the biconical rods between different layers have the same diameter, while the middle diameter is different.

[0011] As a further preferred embodiment, the porosity of the porous lattice structure gradually increases from both ends to the middle.

[0012] As a further preferred embodiment, the shape memory material is NiTi shape memory alloy powder.

[0013] As a further preferred embodiment, the NiTi shape memory alloy powder has a Ni element mass fraction of 55.75% and a powder particle size of 15μm-53μm.

[0014] The preparation method provided in the second aspect of this application adopts the following technical solution:

[0015] A preparation method for preparing any of the porous dual-gradient bone scaffolds with shape memory effect described in the first aspect, comprising the following steps:

[0016] Based on known skeletal structural features, a porous lattice structure model with interconnected internal pores and porosity exhibiting a dual gradient variation is constructed.

[0017] The porous lattice structure model is sliced ​​to obtain three-dimensional slice data;

[0018] Using shape memory materials as raw materials, porous dual-gradient bone scaffolds with shape memory effect are prepared by printing layer by layer based on three-dimensional slice data.

[0019] As a further preferred embodiment, the steps for constructing the porous lattice structure model include:

[0020] Construct a five-mode superstructure model composed of double-cone rods;

[0021] Based on the five-mode superstructure model, a porous lattice structure layer model is constructed.

[0022] Based on the known skeletal structure features, the diameter of the biconical rod in the porous lattice structure layer model is set to obtain multiple porous lattice structure layer models with different porosities.

[0023] By combining porous lattice structure layer models with different porosities, a porous lattice structure model in which the porosity exhibits a dual gradient variation is formed.

[0024] In summary, compared with the prior art, the technical solutions conceived in this application have the following main technical advantages:

[0025] 1. This porous dual-gradient bone scaffold can mimic the porosity and arrangement of human cortical and cancellous bone. By adjusting the middle and end diameters of the single-cell bipyramidal rod structure, the porosity of the porous lattice structure can be controlled. Furthermore, a gradient porosity distribution structure can be set according to the internal structure of human bone. A dual-gradient porosity structure is constructed through the overlapping and cooperation between layers, and the internal pores are interconnected. This design allows the bone scaffold to adapt to the human environment and ensure the transport of nutrients to human bone and the repair of defects, promoting the growth and repair of defects.

[0026] 2. This porous dual-gradient bone scaffold has a shape memory effect, which allows it to be compressed in a low-temperature environment outside the body, effectively reducing the size of the scaffold. During surgery, only a small incision needs to be made at the defect site. After implantation in the human body, the temperature rises to the body temperature, and a phase transition occurs inside the scaffold, resulting in shape recovery. The size increases to the shape predetermined before compression to match the defect site, achieving a perfect match. With this design, the shape memory effect can be used to effectively reduce the surgical incision, and after implantation, it matches irregular defect sites, stimulating bone tissue repair through stress.

[0027] 3. This design ensures tight connections between layers by keeping the diameters of the two ends of the biconical rods between different layers constant, thereby achieving structural stability and pore connectivity in the porous lattice structure. Furthermore, by adjusting the middle diameter of the biconical rods in different layers, the middle diameter of each layer gradually decreases from the top and bottom layers to the middle layer, resulting in a double-gradient distribution of porosity in the porous lattice structure that gradually increases from the top and bottom to the middle. The porous double-gradient bone scaffold designed in this way can match the bone structure and has good biocompatibility and mechanical properties. Attached Figure Description

[0028] Figure 1 This is a schematic diagram of the overall structure of a porous dual-gradient bone scaffold with shape memory effect provided in an embodiment of this application;

[0029] Figure 2 This is a physical illustration of a porous dual-gradient bone scaffold provided in an embodiment of this application;

[0030] Figure 3 This is a schematic diagram of a five-mode superstructure provided in an embodiment of this application;

[0031] Figure 4 This is a front view of a porous dual-gradient bone scaffold provided in an embodiment of this application;

[0032] Figure 5 This is a performance diagram of a NiTi alloy for a porous dual-gradient bone scaffold provided in an embodiment of this application;

[0033] Figure 6 This is a graph showing the change in shape recovery rate of a porous dual-gradient bone scaffold with shape memory effect after compression, as provided in an embodiment of this application.

[0034] Figure 7 This is a flowchart illustrating the fabrication process of a porous dual-gradient bone scaffold provided in an embodiment of this application. Detailed Implementation

[0035] To make the objectives, technical solutions, and advantages of this application clearer, the following detailed description is provided in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the scope of this application.

[0036] The following is in conjunction with the appendix Figures 1-7 This application will be described in further detail.

[0037] This application discloses a porous dual-gradient bone scaffold with shape memory effect. (Refer to...) Figures 1-4The porous dual-gradient bone scaffold with shape memory effect includes a porous lattice structure with multiple structural layers made of memory material. The internal pores of the porous lattice structure are interconnected, and the porosity of the porous lattice structure exhibits a dual-gradient change.

[0038] Specifically, the porous lattice structure includes multiple interconnected porous lattice structure layers. The unit cell of the porous lattice structure layer is a five-mode superstructure composed of biconical rods, and the unit cell preferably presents a regular octahedral shape, wherein the middle diameter of the biconical rod is larger than the diameters at both ends.

[0039] As a preferred embodiment, the matrix structure of the five-mode superstructure is preferably a diamond lattice structure. For ease of understanding, Figure 3 A schematic diagram of a five-mode superstructure composed of double-cone rods is shown.

[0040] As a preferred embodiment, in the five-mode superstructure, the diameters at both ends of the double-cone rod are 0.17mm-0.23mm, and the diameter in the middle is 0.25mm-0.4mm.

[0041] As a preferred embodiment, the length L of the double-cone rod in the five-mode superstructure is... mm.

[0042] Preferably, the side length of the unit cell in the porous lattice structure is 2 mm. The unit cell size is 2 mm × 2 mm × 2 mm.

[0043] Preferably, the overall average volume fraction of the porous lattice structure is 9%-11%, which matches the cancellous bone in human bones; more preferably, the average volume fraction of the porous lattice structure is 9.19%.

[0044] Preferably, the diameters at both ends of the biconical rods between different layers of the porous lattice structure remain constant, while the middle diameters of the biconical rods in different layers differ and can be adjusted. This design ensures tight connections between layers and allows for adjustment of the porosity and relative density of the porous lattice structure layers.

[0045] Preferably, the porous lattice structure has a dual gradient distribution where the diameter is largest and the porosity is smallest in the middle of the upper and lower biconical rods, and the diameter is smallest and the porosity is largest in the middle of the middle biconical rod, with the porosity gradually increasing from the top and bottom to the middle.

[0046] For ease of understanding, Figure 4 A front view of a porous dual-gradient five-mode matrix bone scaffold is shown, where d represents the diameter of both ends of the biconical rod, which is directly selected as 0.2 mm, and D represents the middle diameter of the biconical rod, which is selected in the range of 0.25 mm to 0.40 mm.

[0047] Preferably, in a single-layer structure, the relative density of the porous lattice structure layer is 7% to 15%.

[0048] It should be noted that relative density is the ratio of the actual density of a material to its theoretical density (i.e., the density in a fully compacted state).

[0049] It is clear that in other embodiments, the porosity and relative density of each layer of porous lattice structure can be adjusted by adjusting the middle diameter of different layers of biconical rods, depending on the actual required density, thereby achieving the adjustment of the porous lattice structure.

[0050] Furthermore, the materials selected for this porous dual-gradient bone scaffold include, but are not limited to, NiTi shape memory alloy powder with a near-equal atomic ratio, wherein the Ni element mass fraction is 55.75%, and the powder particle size is 15μm-53μm. This type of powder possesses excellent shape memory properties, and its particle size is suitable for printing using laser powder bed fusion technology. For ease of understanding, Figure 5 The performance diagram of NiTi shape memory alloy, the raw material for this bone scaffold, is shown.

[0051] Furthermore, the shape memory effect described in this scheme refers to the ability to be compressed at low temperatures and to recover its original shape after the temperature is raised. The specific changes in the shape recovery rate of this bone scaffold after compression are as follows: Figure 6 As shown.

[0052] Furthermore, this porous dual-gradient bone scaffold is manufactured using additive manufacturing methods, preferably laser powder bed melting technology. The shape memory deformation temperature of the scaffold can be controlled by adjusting the parameters of the laser powder bed melting technology. Preferably, the austenite transformation termination temperature is generally around body temperature (37°C).

[0053] In this design, the mechanical properties of the bone scaffold are controlled by additive manufacturing to ensure a match. The bone scaffold can be compressed and directly implanted into the defective part of the human bone. After adapting to body temperature, it will recover its shape and promote the repair and growth of the defective part of the human bone.

[0054] This application also discloses a preparation method for preparing any of the above-mentioned porous dual-gradient bone scaffolds with shape memory effect. The preparation method includes the following steps:

[0055] S1: Based on known skeletal structural features, a porous lattice structure model with interconnected internal pores and a porosity exhibiting a dual gradient variation is constructed.

[0056] The specific steps for constructing the porous lattice structure model include:

[0057] S11: Construct a five-mode superstructure model composed of biconical rods (i.e., construct a five-mode superstructure unit cell).

[0058] S12: Based on the five-mode superstructure model, a preliminary periodically arranged porous lattice structure layer model is constructed (i.e., a single-layer structure is constructed).

[0059] S13: Based on the known skeletal structure features, the diameter of the biconical rod in the porous lattice structure layer model is set according to the porosity requirements to obtain multiple porous lattice structure layer models with different porosities.

[0060] S14: Combine porous lattice structure layer models with different porosities to ensure complete interlayer bonding and present a dual gradient distribution that matches the skeleton (such as human bone), so as to form a porous lattice structure model with porosity exhibiting dual gradient changes (i.e., construct the overall model).

[0061] For ease of understanding, in some specific embodiments, the specific steps for constructing and combining porous lattice structure layers with different porosities are as follows:

[0062] Select a double-conical rod with both ends having the same diameter, change the middle diameter according to the porosity distribution, and construct a 7×7 array in the horizontal XY direction (in other embodiments, arrays with other row and column combinations can also be used) to construct a single-layer porous lattice structure layer.

[0063] The porosity of a single layer can be changed by altering the size of the middle diameter of the biconical rod, and layers with different porosities can be derived based on the desired dual gradient distribution.

[0064] The layers are bonded together according to their porosity distribution, ensuring that the end points of the upper surface of the lower layer and the lower surface of the upper layer completely overlap, thus allowing the pores between the layers to be interconnected. The porosity distribution is as follows: the middle diameter of the upper and lower double-cone rods is large with low porosity, while the middle double-cone rods have a small middle diameter and high porosity.

[0065] S2: Slice the porous lattice structure model to obtain three-dimensional slice data;

[0066] S3: Using shape memory materials as raw materials, a porous dual-gradient bone scaffold with shape memory effect is prepared by printing layer by layer based on three-dimensional slice data.

[0067] Among them, NiTi alloy powder with near-equal atomic ratio and shape memory effect is preferably used as raw material, and laser powder bed melting technology is used to print layer by layer to manufacture a porous dual-gradient bone scaffold with shape memory effect.

[0068] The laser power of the laser powder bed fusion technology used is preferably 200-300W, and the scanning rate is preferably 900-1300mm / s. In some specific embodiments, the printing parameters of the laser powder bed fusion technology used are: laser power 250W, scanning speed 1100mm / s, and layer thickness 40μm.

[0069] For ease of understanding, Figure 7 A flowchart illustrating the manufacturing process of a porous dual-gradient bone scaffold is presented.

[0070] Example:

[0071] The five-mode superstructure unit cell was constructed using COMSOL software. First, a trapezoid with variable parameters for the middle and end diameters was constructed on the sketch. A double-cone rod was constructed by rotation and mirroring. The double-cone rod was then used to construct the unit cell in space according to the five-mode superstructure configuration. After the unit cell was constructed, a 7×7 array was constructed in the horizontal direction. The array size can be changed according to the specific application. A single-layer five-mode superstructure lattice was constructed and exported as an igs model file.

[0072] Based on the requirements of the bone structure unit cell and the porosity requirements, the size of the middle diameter is changed, and the above steps are repeated to derive the single-layer structure of other layers. After all single-layer models are constructed, all IGS model files are imported into the COMSOL model, arranged according to the dual-gradient porosity distribution, ensuring that the end diameters coincide. Boolean operations are performed on the single-layer models to find their intersection, constructing the overall dual-gradient structure. The obtained model is then repaired and sliced ​​in Magics software.

[0073] The material is manufactured using fused deposition modeling (FDM) technology, employing near-equal atomic ratio NiTi alloy powder. The additive manufacturing equipment melts and deposits the material layer by layer based on three-dimensional slice data to obtain a porous dual-gradient bone scaffold with shape memory effect.

[0074] In summary, this porous dual-gradient bone scaffold, designed according to this scheme, can mimic the porosity and arrangement of human cortical and cancellous bone. By adjusting the middle and end diameters of the single-cell bipyramidal rod structure, the porosity of the porous lattice structure can be controllably varied. Furthermore, a gradient pore distribution structure can be set according to the internal structure of human bone. A dual-gradient porous structure is constructed through the overlapping and cooperation between layers, with interconnected internal pores. This porous bone scaffold can adapt to the human body environment and ensure the transport of nutrients to human bone and the repair of defects, promoting the growth and repair of damaged areas. It is particularly suitable for the treatment of diseases in the cancellous bone of the human body.

[0075] Furthermore, this porous dual-gradient bone scaffold utilizes NiTi alloy powder with shape memory effect, manufactured using laser powder bed melting technology. This high-precision manufacturing allows for the customization of complex and precise porous structures for different defect sites. The printed scaffold exhibits shape memory effect, enabling compression under low-temperature conditions outside the body, effectively reducing its size. During surgery, only a small incision needs to be made at the defect site. After implantation, the temperature rises to body temperature, causing a phase transition within the scaffold, resulting in shape recovery. The scaffold then increases in size to match the pre-defined shape of the defect site, achieving a perfect fit. Therefore, this design effectively reduces surgical incisions by utilizing shape memory effect, and after implantation, it matches irregular defect sites, stimulating bone tissue repair through stress.

[0076] It should be understood that expressions such as "comprising" and "may include" as used in this application indicate the existence of the disclosed functions, operations, or constituent elements, and do not limit one or more additional functions, operations, and constituent elements. In this application, terms such as "comprising" and / or "having" may be interpreted as indicating a specific characteristic, number, operation, constituent element, component, or combination thereof, but should not be interpreted as excluding the existence or possibility of adding one or more other characteristics, numbers, operations, constituent elements, components, or combinations thereof.

[0077] It should be understood that the terms “center,” “upper,” “lower,” “front,” “rear,” “left,” “right,” “vertical,” “horizontal,” “inner,” “outer,” “clockwise,” “counterclockwise,” “axial,” “radial,” and “circumferential” indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this application.

[0078] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this application, "multiple" means two or more, unless otherwise explicitly specified.

[0079] In this application, unless otherwise expressly specified and limited, the terms "installation," "connection," "linking," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection between two components. Those skilled in the art can understand the specific meaning of the above terms in this application according to the specific circumstances.

[0080] Those skilled in the art will readily understand that the above description is merely a preferred embodiment of this application and is not intended to limit this application. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A porous dual-gradient bone scaffold with shape memory effect, characterized in that, This includes a porous lattice structure with multiple structural layers made of memory material, wherein the internal pores of the porous lattice structure are interconnected, and the porosity of the porous lattice structure exhibits a dual gradient variation. The unit cell of the porous lattice structure is a five-mode superstructure composed of double cone rods, wherein the middle diameter of the double cone rods is larger than the diameters at both ends. In the porous lattice structure, the two ends of the biconical rods between different layers have the same diameter, while the middle diameter is different, and the porosity of the porous lattice structure gradually increases from the two ends to the middle.

2. The porous dual-gradient bone scaffold as described in claim 1, characterized in that, The matrix structure of the five-mode superstructure is a diamond lattice structure.

3. The porous dual-gradient bone scaffold as described in claim 1, characterized in that, The diameters at both ends of the double-cone rod are 0.17mm-0.23mm, and the diameter in the middle is 0.25mm-0.4mm.

4. The porous dual-gradient bone scaffold as described in any one of claims 1-3, characterized in that, The shape memory material is NiTi shape memory alloy powder.

5. The porous dual-gradient bone scaffold as described in claim 4, characterized in that, The NiTi shape memory alloy powder has a Ni element mass fraction of 55.75% and a powder particle size of 15μm-53μm.

6. A preparation method for preparing a porous dual-gradient bone scaffold with shape memory effect as described in any one of claims 1-5, characterized in that, The preparation method includes the following steps: Based on known skeletal structural features, a porous lattice structure model with interconnected internal pores and porosity exhibiting a dual gradient variation is constructed. The porous lattice structure model is sliced ​​to obtain three-dimensional slice data; Using shape memory materials as raw materials, porous dual-gradient bone scaffolds with shape memory effect are prepared by printing layer by layer based on three-dimensional slice data.

7. The preparation method according to claim 6, characterized in that, The steps for constructing the porous lattice structure model include: Construct a five-mode superstructure model composed of double-cone rods; Based on the five-mode superstructure model, a porous lattice structure layer model is constructed. Based on the known skeletal structure features, the diameter of the biconical rod in the porous lattice structure layer model is set to obtain multiple porous lattice structure layer models with different porosities. By combining porous lattice structure layer models with different porosities, a porous lattice structure model in which the porosity exhibits a dual gradient variation is formed.

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