CN114642764A

CN114642764A - Bone tissue engineering shape-divided support construction method

Info

Publication number: CN114642764A
Application number: CN202011509153.0A
Authority: CN
Inventors: 阮长顺; 屈华伟
Original assignee: Shenzhen Institute of Advanced Technology of CAS
Current assignee: Shenzhen Institute of Advanced Technology of CAS
Priority date: 2020-12-18
Filing date: 2020-12-18
Publication date: 2022-06-21
Anticipated expiration: 2040-12-18
Also published as: CN114642764B

Abstract

The invention relates to the technical field of biomedical materials, in particular to a method for constructing a bone tissue engineering shape-divided support. The method comprises the following steps: obtaining a physical geometry of a target bone replacement; determining a 2D shape-spanning tree curve according to the physical geometry of the target bone substitute; carrying out circumferential array on the 2D shape-divided tree curve by using the axis of the target bone defect to construct a 2D shape-divided layer; designing 2D concentric circular curves at the bifurcating positions of the 2D fractal tree curves, and forming a 2D circular layer by using the 2D concentric circular curves with different diameters; on the basis of the 2D shaping layer and the 2D annular layer, a 3D shaping layer and a 3D annular layer are created according to the diameter of the tows and the height of the target bone substitute; the materials are axially stacked layer by layer to construct a fractal support of the bone tissue engineering. The invention solves the technical problem that the radial gradient pore change is relatively lacked when the existing bracket is constructed.

Description

Bone tissue engineering shape-divided support construction method

Technical Field

The invention relates to the technical field of biomedical materials, in particular to a method for constructing a shape-divided support for bone tissue engineering.

Background

Critical bone defects are one of the important problems in orthopedics today, and seriously affect people's health and quality of life. Although autologous bone grafting has been the gold standard of treatment, the number of available bones limits its widespread clinical use. In this case, tissue engineering was proposed in 1987 with the aim of obtaining artificial alternatives for tissue replacement and regeneration. The ideal bone scaffold (material) should have biological activity, mechanical support, permeability, biodegradability, etc. Wherein the interconnected porous structure is effective in promoting cell proliferation and ingrowth as well as transport of nutrients and oxygen, and promoting tissue regeneration.

In order to simulate the gradient pore structure of "marrow cavity-cancellous bone-cortical bone" of natural bone, Computer Aided Design (CAD) methods including Voronoi tesselation method, Triple Periodic Minimum Surface (TPMS), topology optimization, etc. have been used to design bone scaffold models having a gradient structure, but the manufacturing techniques of the scaffold obtained by the above methods are mainly Selective Laser Melting (SLM), Electron Beam Melting (EBM), Stereolithography (SLA), etc.

Although the design of the controllable gradient pore scaffold can be realized in the prior art, the manufacturing process matched with the controllable gradient pore scaffold is not friendly to cells, even harmful, such as the high temperature of processing, the toxicity of photosensitive materials and the like, and the requirement of the biological 3D printing bone tissue engineering scaffold on a radial gradient pore structure cannot be met.

While extrusion 3D printing is widely used due to its simplicity of operation, wide range of materials available, and the ability to perform cell printing, there are some stents designed with axially graded pores by adjusting parameters such as extruded strand diameter and distribution spacing (bitter S M, Smith B T, Diaz-Gomez L, et al, fabrication and mechanical properties of 3D printed vertical units and gradient scans for bone and osseointegration [ J ] acetic materials, 2019,90:37-48), but the study of the stent' S radial gradient variation is lacking. That is, for the existing research on the extrusion type 3D printing gradient pore scaffold, the axial gradient pore distribution of the scaffold is mainly realized around the axial accumulation, and how to realize the gradient pore change simulating the natural bone from the cancellous bone to the cortical bone is relatively absent. Therefore, how to design and prepare a bionic gradient pore bone tissue engineering scaffold based on extrusion type 3D printing is a big problem in tissue engineering of the current 3D printing technology.

Disclosure of Invention

The embodiment of the invention provides a method for constructing a shape-divided scaffold for bone tissue engineering, which at least solves the technical problem that gradient pore changes are relatively deficient when the existing scaffold is constructed.

According to the embodiment of the invention, the method for constructing the bone tissue engineering shape-divided scaffold comprises the following steps:

obtaining a physical geometry of a target bone replacement;

determining a 2D shape-spanning tree curve according to the physical geometry of the target bone substitute;

carrying out circumferential array on the 2D shape-divided tree curve by using the axis of the target bone defect to construct a 2D shape-divided layer;

designing 2D concentric circular curves at the branching positions of the 2D shape-dividing tree curves, and forming a 2D circular layer by using the 2D concentric circular curves with different diameters;

on the basis of the 2D shape-dividing layer and the 2D ring layer, a 3D shape-dividing layer and a 3D ring layer are created according to the diameter of the tows and the height of the target bone substitute, and the 3D shape-dividing layer and the 3D ring layer are axially stacked to construct a bone tissue engineering shape-dividing support 3D model.

Further, the method further comprises:

equally dividing the bone tissue engineering shape-divided support 3D model into n-1 areas along the radius direction, and respectively calculating the porosity of each area, wherein n is an integer more than or equal to 2;

and obtaining the bone tissue engineering fractal support 3D model with radial gradient pores by adjusting the related fractal primary patterns, iteration rules, iteration times, all-level bifurcation angles of the 2D fractal tree curves, the number of circumferential arrays of the 2D fractal tree curves and the diameter parameters of tows.

Further, the method further comprises:

constructing a manufacturing code for the radial gradient pore tissue engineering scaffold based on a programming software, a manufacturing code definition rule of a commercial printer and a printer feeding motion parameter, wherein the 2D fractal layer curve and the 2D circular ring layer curve of the obtained bone tissue engineering fractal scaffold 3D model with the radial gradient pores;

modifying and adjusting related printer feeding motion parameters until the diameter of the actually extruded tows of the 3D printer is close to that of the tows of the bone tissue engineering fractal support 3D model with radial gradient pores;

and realizing the design of the whole 3D model and the acquisition of manufacturing codes in parameterized design software, and then carrying out 3D printing preparation on the bracket.

Further, before the bone tissue engineering fractal support is prepared by 3D printing, the method further comprises:

polylactic-co-glycolic acid (PLGA) and 1, 4-dioxane in a proportion of 0.8-1.2g/2-3ml are magnetically stirred for 8-12 hours to prepare printing ink; wherein the printing ink material is one or more combined biological materials or cell biological ink containing one or more combinations.

Further, the physical geometry of the target bone substitute is determined from the CT or MRI medical image data by the mics medical processing software.

And further, determining a 2D fractal shape tree curve according to the inner diameter size, the outer diameter size, the fractal primary pattern, the iteration rule and the iteration times of the physical geometric size of the target bone substitute.

Further, on the basis of the 2D shaping layer and the 2D circular layer, a circle with the same diameter as the extruded tows of the 3D printer moves along the line of the 2D shaping layer and the 2D circular layer by taking the center of the circle as a reference point, the normal line of the center of the circle is always superposed with the 2D line, and the circle stretches and deviates to form the 3D shaping layer and the 3D circular layer which are mutually supported. The bottom layer is a 3D shaping layer, the position of the 3D annular layer is located by shifting a numerical value of the distance between layers along the axial direction, and then the layers are sequentially stacked layer by layer along the axial direction until the height of the target bone defect is reached, so that the construction of the bone tissue engineering shape-divided support 3D model is completed.

Further, the 2D fractal layer curve and the 2D circular ring layer curve of the obtained bone tissue engineering fractal support 3D model with the radial gradient pores are combined with the manufacturing code definition rule of a commercial printer and the feeding motion parameters of the printer, and the manufacturing code for the radial gradient pore tissue engineering support is constructed through a Python programming language.

Further, the feeding motion parameters of the printer comprise the extrusion air pressure of printing ink, the motion speed of the printing head, the height of the printing head from the bottom receiving platform and the rheological property of the ink.

Further, the design and manufacturing codes of the whole 3D model are obtained in a parametric design software Grasshopper carried by the Rhino, and a 'design-manufacturing' workflow of 3D printing of the fractal-shaped scaffold for the radial gradient pore bone tissue engineering is constructed, and the workflow can be modified in a one-key type parametric mode according to target requirements.

Further, the bone tissue engineering fractal-shaped scaffold prepared by 3D printing is subjected to three-dimensional reconstruction through Micro-CT SkyScan1176, and the porosity of all regions in the whole and radial directions is evaluated on the basis of reconstruction.

Furthermore, the bone tissue engineering fractal support with the iteration number N being more than or equal to 3 has the characteristic that the porosity is gradually reduced from inside to outside, and the trend that the porosity gradient is reduced along with the increase of the iteration number is more and more obvious.

Further, the method also includes:

constructing a bone tissue engineering fractal shape scaffold design-manufacturing workflow in a parameterization manner to obtain a manufacturing code (G-code);

printing and preparing a fractal scaffold for bone tissue engineering and carrying out CT three-dimensional reconstruction to evaluate the porosity of the scaffold.

A storage medium storing a program file capable of implementing any one of the above bone tissue engineering fractal scaffold constructing methods.

A processor for executing a program, wherein the program executes the bone tissue engineering fractal scaffold construction method.

The invention provides a method for constructing a bone tissue engineering shape-dividing support, and provides a shape-dividing tree curve with an iteration function based on bionic and fractal design. The fractal tree curve is formed by constructing a 2D fractal layer by a circumferential array according to the axis of target bone defect, constructing a 2D circular ring layer according to the 2D fractal layer, and constructing a 3D fractal layer and a 3D circular ring layer by stretching and offsetting a circle with the interlayer distance as the diameter along the 2D fractal layer and the 2D circular ring layer on the basis of the 2D fractal layer and the 2D circular ring layer.

Drawings

The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this application, illustrate embodiment(s) of the invention and together with the description serve to explain the invention without limiting the invention. In the drawings:

FIG. 1 is a flow chart of the method for constructing a scaffold in different shapes for bone tissue engineering according to the present invention;

FIG. 2 is a graph of a proposed fractal tree based on Koch snowflakes;

FIG. 3 is a schematic of 0-3 iterations of the fractal tree curves (A1, B1, C1, D1) and an iteration rule graph (A2, B2, C2, D2);

FIG. 4 is a schematic diagram of the design and manufacture of a bone tissue engineering fractal support based on extrusion type 3D printing;

FIG. 5 is a pore gradient plot of a bone tissue engineering fractal-shaped scaffold with 90 degrees tow orthogonality (common stacking manner of extrusion type 3D printing) and 0-3 iterations;

FIG. 6 is a rule that the bone tissue engineering scaffold is equally divided into six regions a-f along the radial direction;

FIG. 7 is a flow chart of the "design-manufacture" workflow of 3D printing of a fractal scaffold for radial gradient pore bone tissue engineering;

fig. 8 is a pictorial view of a 90 ° orthogonal (90 °), 0 iteration (N ═ 0), and 3 iterations (N ═ 3) bone tissue engineering fractal shape scaffold obtained by extrusion 3D printing;

fig. 9 is the bulk and local porosity of bone tissue engineering scaffolds prepared by 3D printing at 90 ° orthogonality (90 °), 0 iteration (N ═ 0), and 3 iterations (N ═ 3).

Detailed Description

In order to make the technical solutions of the present invention better understood, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

It should be noted that the terms "first," "second," and the like in the description and claims of the present invention and in the drawings described above are used for distinguishing between similar elements and not necessarily for describing a particular sequential or chronological order. It is to be understood that the data so used is interchangeable under appropriate circumstances such that the embodiments of the invention described herein are capable of operation in sequences other than those illustrated or described herein. Furthermore, the terms "comprises," "comprising," and "having," and any variations thereof, are intended to cover a non-exclusive inclusion, such that a process, method, system, article, or apparatus that comprises a list of steps or elements is not necessarily limited to those steps or elements expressly listed, but may include other steps or elements not expressly listed or inherent to such process, method, article, or apparatus.

Example 1

According to an embodiment of the present invention, there is provided a method for constructing a bone tissue engineering fractal scaffold, referring to fig. 1, including the following steps:

s101, acquiring the physical geometric size of the target bone substitute;

s102, determining a 2D shape-divided tree curve according to the physical geometric dimension of the target bone substitute;

s103, constructing a 2D fractal layer by carrying out circumferential array on the 2D fractal tree curve by using the axis of the target bone defect;

s104, designing 2D concentric circular curves at the branching positions of the 2D fractal tree curves, and forming a 2D circular layer by using the 2D concentric circular curves with different diameters;

s105, creating a 3D (three-dimensional) fractal layer and a 3D circular layer according to the diameter of the tows and the height of the target bone substitute, and axially stacking the 3D fractal layer and the 3D circular layer by layer to construct a bone tissue engineering fractal-shaped bracket;

s106, constructing a bone tissue engineering fractal shape support design-manufacturing workflow in a parameterization mode to obtain a manufacturing code;

and S107, preparing a bone tissue engineering fractal-shaped scaffold by 3D printing and evaluating the porosity of the scaffold by CT three-dimensional reconstruction.

The invention provides a method for constructing a bone tissue engineering shape-divided support, and provides a shape-divided tree curve with an iteration function based on bionic and fractal design. The fractal tree curve is used for constructing a 2D fractal layer by a circumferential array according to the axis of target bone defect, and constructing a 2D circular ring layer according to the 2D fractal layer, on the basis of the 2D fractal layer and the 2D circular ring layer, extruding a circle with the same diameter of a tow by a 3D printer, moving along the lines of the 2D fractal layer and the 2D circular ring layer by taking the center of the circle as a reference point, enabling the center normal of the circle to coincide with the 2D line all the time, stretching and offsetting the circle to form the 3D fractal layer and the 3D circular ring layer, mutually supporting the 3D fractal layer and the 3D circular ring layer, stacking the 3D printing bone tissue engineering fractal support 3D model layer by layer, and constructing a stable structure by layer.

Wherein, the method further comprises:

the bone tissue engineering fractal support 3D model with radial gradient pores is obtained by adjusting parameters including fractal primary patterns, iteration rules, iteration times, all-level bifurcation angles of 2D fractal tree curves, the number of circumferential arrays of the 2D fractal tree curves, interlayer distances and the like.

Wherein, the method further comprises:

modifying and adjusting related printer feeding motion parameters until the diameter of the actually extruded tows of the 3D printer is close to the interlayer distance of the 3D model of the bone tissue engineering fractal support with radial gradient pores;

Wherein, prior to obtaining the physical geometry of the target bone substitute, the method further comprises:

polylactic-co-glycolic acid (PLGA) and 1, 4-dioxane are magnetically stirred for 8 to 12 hours at a ratio of 0.8 to 1.2g/2 to 3ml to prepare printing ink; wherein the printing ink material is one or more combined biological materials or cell biological ink containing one or more combinations.

Wherein, the physical geometry size of the target bone substitute is determined by Mimics medical processing software according to CT or MRI medical image data.

And determining a 2D shape-divided tree curve according to the inner diameter size and the outer diameter size of the target bone substitute in the physical geometric dimension, the fractal primary pattern, the iteration rule and the iteration times.

Wherein, on the basis of 2D shape-dividing layer and 2D ring layer, according to the silk bundle diameter and the height of target bone substitute establish 3D shape-dividing layer and 3D ring layer, its axial is piled up and is constructed bone tissue engineering and divide shape support 3D model to include:

extruding a circle with the same diameter of a tow by a 3D printer, moving along the lines of a 2D parting layer and a 2D circular ring layer by taking the center of the circle as a reference point, and enabling the center normal line of the circle to coincide with the 2D lines all the time, wherein the circle is stretched and deviated to form the 3D parting layer and the 3D circular ring layer, the bottommost layer is the 3D parting layer, the position of the 3D circular ring layer is located by deviating the numerical value of the distance between layers along the axial direction, and then the 3D circular ring layer is sequentially circularly stacked along the axial direction until the height of the target bone defect is reached, so that the construction of the 3D model of the bone tissue engineering parting support is completed.

The 2D fractal layer curve and the 2D circular ring layer curve of the obtained bone tissue engineering fractal support 3D model with the radial gradient pores are combined with the manufacturing code definition rule of a commercial printer and the printer feeding motion parameters, and a GhPython battery is used in a parameterized design software Grasshopper to construct a manufacturing code for the radial gradient pore tissue engineering support through a Python programming language.

The feeding motion parameters of the printer comprise extrusion air pressure of printing ink, motion speed of a printing head, height of the printing head from a bottom receiving platform and ink rheological property.

The method comprises the steps of obtaining design and manufacturing codes of a whole 3D model in a parametric design software Grasshopper of the Rhino, constructing a 'design-manufacturing' workflow of a fractal-shaped scaffold for 3D printing of radial gradient pore bone tissue engineering, and performing one-key parametric modification on the workflow according to target requirements.

Wherein the Micro-CT imaging system SkyScan1176 is used to reconstruct the scaffold in three dimensions to obtain its overall and fractional porosity.

The method for constructing the bone tissue engineering scaffold in different shapes according to the present invention is described in detail in the following embodiments:

the invention belongs to the technical field of biomedical materials, and particularly relates to a construction method of a bone tissue engineering fractal scaffold with radial gradient pores based on bionic and fractal design, and a parameterized scaffold 'design-manufacture' workflow is built. The fractal-shaped scaffold with porosity gradient change along the radius direction is constructed under computer-aided design, so that the structure has controllable gradient pores; the constructed scaffold simulates the pore morphology of natural bone from cancellous bone to cortical bone, and can be used for repairing and regenerating tissue engineering; and secondarily developing the existing commercial 3D printer to complete the preparation of the support. The fractal scaffold for bone tissue engineering can be used for preparing tissue engineering scaffolds with different gradient pores and different properties according to actual requirements.

The invention relates to a bionic and fractal design-based bone tissue engineering shape-divided support construction method with radial gradient pores, in particular to a shape-divided tree curve design, a bone tissue engineering shape-divided support construction, a support design-manufacture working data stream construction and a support construction method thereof.

The invention aims to overcome the defects of the prior art in the design of a bone tissue engineering bracket in a radial gradient pore structure, provides a construction method of a bone tissue engineering bracket with radial gradient pores based on bionic and fractal design, and carries out 'design-manufacture' workflow of secondary development and bracket construction on the conventional commercial 3D printer. According to the method, the controllable gradient pore based on the extrusion type 3D printing can be obtained, and the controllable gradient pore can be used for repairing and regenerating bone tissues and other tissues. Specifically, the invention can dynamically change the scaffold model according to the bone defect size parameters of a patient, construct the 'design-manufacture' workflow of the bone tissue engineering fractal-shaped scaffold, and secondarily develop the existing commercial 3D printer so as to prepare the designed radial gradient pore bone tissue engineering scaffold. Meanwhile, the production and manufacturing cost is saved by secondary development of the existing commercial 3D printer.

The specific steps of the invention are summarized as follows:

1) polylactic-co-glycolic acid (PLGA) and 1, 4-dioxane were magnetically stirred at a ratio of 1g/2.5ml for 10 hours to prepare printing inks. The printing ink material can be one or more combined biological materials or cell biological ink containing one or more combinations.

2) The physical geometry (such as inner diameter, outer diameter, height and the like) of the target bone substitute is determined according to medical image data such as CT or MRI and the like through medical processing software such as Mimics and the like.

3) And determining a 2D shape-dividing tree curve according to the inner and outer diameter sizes, the fractal primary patterns, the iteration rules and the iteration times of the target bone substitute in the step 2).

4) Carrying out circumferential array on the 2D shape-divided tree curve obtained in the step 3) by using the axis of the target bone defect to construct a 2D shape-divided layer.

5) According to the 2D shaping layer determined in the step 4), in order to realize mutual supporting between layers of the 3D support, 2D concentric circular ring curves are designed at the branching positions of the 2D shaping tree curves, and the concentric 2D circular ring curves with different diameters form a 2D circular ring layer.

6) According to the 2D shaping layers determined in the step 5), each 2D shaping layer is set to comprise n 2D concentric circular curves, and n is an integer larger than or equal to 2.

7) Determining the interlayer distance (i.e. the diameter of the filament bundle) and the axial array number according to the height of the target bone substitute on the basis of obtaining the 2D shaping layer and the 2D annular layer in the steps 4) and 5). The 2D shape-distribution layer and the 2D circular ring layer can be formed by stretching and offsetting a circle with the diameter as the distance between the layers along a line. And the bottommost layer is a 3D shaping layer, the position of the 3D annular layer is positioned by shifting a numerical value of the interlayer distance along the axial direction, and then the 3D annular layer is circularly stacked along the axial direction in sequence until the height of the target bone defect is reached, so that the construction of the bone tissue engineering shape-divided support 3D model is completed.

8) Equally dividing the scaffold 3D model obtained in the step 7) into n-1 regions along the radius direction, and respectively calculating the porosity of each region, wherein n is derived from the step 6).

9) And (3) obtaining the 3D model of the bone tissue engineering fractal support with the radial gradient pores by adjusting parameters including fractal primary patterns, iteration rules, iteration times, all-level bifurcation angles of the 2D fractal tree curves, the number of circumferential arrays of the 2D fractal tree curves, interlayer distances and the like related in the steps 3) to 8).

10) Extracting the 2D fractal layer curve and the 2D circular layer curve of the stent 3D model obtained in the step 9), and constructing a manufacturing code for the radial gradient pore tissue engineering stent based on parametric design software Grasshopper in combination with parameters such as a manufacturing code (G-code) definition rule of a commercial printer, printer feeding motion and the like.

11) Modifying and adjusting the feeding motion parameters of the printer related to the step 10) until the diameter of the actually extruded tows of the 3D printer is close to the interlayer distance of the 3D model of the bracket. The feeding motion parameters of the printer comprise extrusion air pressure of printing ink, motion speed of a printing head, height of the printing head from a bottom receiving platform and ink rheological property.

12) And 3) realizing the design of the whole 3D model and the acquisition of a manufacturing code (G-code) in the parametric design software Grasshopper carried by the Rhino in the steps 3) to 11), and then carrying out 3D printing preparation on the scaffold, namely constructing a 'design-manufacturing' workflow of the fractal-shaped scaffold for 3D printing of the radial gradient pore bone tissue engineering, wherein the workflow can be modified in a one-key type parameterization mode according to the target requirement.

13) 3D printing is carried out based on the step 1) and the step 12) to prepare the bone tissue engineering fractal-shaped scaffold, and low-temperature freeze-drying treatment is carried out on the bone tissue engineering fractal-shaped scaffold.

14) And (3) carrying out three-dimensional reconstruction on the bone tissue engineering shape-divided support prepared in the step 13), obtaining the porosity of the whole body and each local area by combining the step 8) through Boolean operation, and evaluating the radial gradient porosity of the whole body and each local area.

The key points of the technology of the invention are as follows:

1. the method is applied to bionic and fractal science to design the 2D fractal shape tree curve.

2. The 2D fractal tree curve proposed in the invention forms a 2D fractal layer by surrounding the axis array of the target bone defect.

3. In order to realize the structural stability of the 3D printing support, the invention provides that a 2D concentric circular curve is arranged at a bifurcation point of a 2D fractal layer curve, and the concentric 2D circular curves with different diameters form a 2D circular layer.

4. According to the invention, the 2D shaping layer and the 2D ring layer are stretched and offset along a line by using a circle with the diameter as the interlayer distance to form the 3D shaping layer and the 3D ring layer, and are stacked layer by layer along the axial direction until the height of the target bone defect is reached, so that the construction of the 3D model of the bone tissue engineering shape-divided support is completed.

5. In the invention, the design of the whole 3D model and the acquisition of a manufacturing code (G-code) are realized in the Grasshopper which is parameterized design software carried by the Rhino, and the subsequent 3D printing preparation of the scaffold is realized, so that a one-key parameterized 3D printing radial gradient pore bone tissue engineering fractal-shaped scaffold design-manufacturing workflow is constructed.

6. The invention provides a design and preparation method of a bone tissue engineering fractal-shaped scaffold with radial pore gradient, which can be used for extrusion type biological 3D printing.

7. The fractal-shaped scaffold with the radial pore gradient for bone tissue engineering designed by the invention comprises but is not limited to extrusion type 3D printing.

8. The printing ink can comprise one or more of biological materials such as high molecular materials, hydrogel and the like.

9. The printing ink according to the invention may comprise one or more cells.

The invention at least comprises the following protection points:

1. the invention provides a sub-shape tree curve with an iteration function based on bionic and fractal design. The fractal tree curve is iterated for 3 times or more than 3 times (N is more than or equal to 3 times), and the design of the bone tissue engineering fractal support with radial gradient pores can be realized by constructing the fractal layer and the annular layer.

2. According to the invention, the fractal layer and the annular layer are used for mutual supporting, and the 3D printing radial gradient pore bone tissue engineering fractal support with a stable structure is constructed by layer-by-layer stacking.

3. The fractal support for bone tissue engineering provided by the invention can be correspondingly adjusted according to the size of the target bone defect.

4. The invention constructs a 'design-manufacture' workflow of 3D printing of a fractal-shaped scaffold for radial gradient pore bone tissue engineering based on parameterized design software Grasshopper. The target bone tissue engineering scaffold can be easily obtained by modifying parameters such as fractal primary patterns, iteration rules, iteration times, all levels of bifurcation angles of 2D fractal tree curves, the number of circumferential arrays of the 2D fractal tree curves, interlayer distances, manufacturing code (G-code) definition rules, printer feeding motions and the like through one key.

5. The bone tissue engineering fractal-shaped scaffold with the radial gradient pores designed by the invention can be prepared by an extrusion type 3D printing technology.

6. According to the method, the 3D model and the three-dimensional reconstruction model of the stent are equally divided along the radial direction, and the porosity of each region is calculated to evaluate the gradient pore change of each region in the radial direction.

Compared with the prior art, the invention brings many advantages, at least as follows:

1. the radial gradient pore bone tissue engineering shape-dividing support realizes the controllability of pores with radial gradients based on extrusion type 3D printing, and is suitable for the preparation of radial gradient bone tissue engineering supports with different scales.

2. A 'design-manufacture' workflow of 3D printing of the fractal-shaped scaffold for the radial gradient pore bone tissue engineering is set up, and design and manufacture parameters can be adjusted according to different requirements to obtain a target scaffold.

3. The 'design-manufacture' workflow of the radial gradient pore tissue engineering scaffold built by the invention can complete the secondary development of common commercial common/industrial/medical extrusion type 3D printers according to the manufacturing code rules of different printers, thereby reducing the production and manufacturing cost.

4. The invention provides an evaluation rule for evaluating gradient pores at equal intervals in the radial direction.

The invention is proved to be feasible by experimental verification, and the specific implementation case is as follows:

A. the fractal tree curves were designed in the parametric software Grasshopper carried by rhino6.0 itself, with inspiration from koch snowflakes (see fig. 2A-B) and koch curves (see fig. 2C), showing the results of the curves iterated 0-3 times, respectively (see fig. 2D). Wherein FIG. 2A is a snowflake 2D model, FIG. 2B is a Koch snowflake iterated 3 times within a regular triangle, and FIGS. 2C and 2D are a Koch curve and a fractal-like tree curve iterated 0-3 times, respectively.

B. The main parameters affecting the fractal tree curve are the number of iterations and the bifurcation angles at each level (see fig. 3), and particularly, the lines of the odd-numbered regions of the fractal tree curve are all along the radius direction, such as the lines FG and HI of fig. 3C 2.

C. The bone tissue engineering fractal support is formed by stacking a 3D fractal layer and a 3D ring layer by layer and supporting each other, wherein the 3D fractal layer and the 3D ring layer are respectively formed by stretching a 2D fractal layer curve and a 2D ring layer curve through a circle with the distance between layers as the diameter, the 2D fractal layer curve is formed by cutting out a fractal tree curve of a tail line and performing circumference array by using a bone defect axis, and the 2D ring layer curve constructs a plurality of 2D concentric ring curves by using a bifurcation point of the fractal tree curve. A schematic design and manufacturing diagram of a fractal-shaped scaffold for bone tissue engineering based on extrusion-based 3D printing is shown by taking a fractal-shaped tree curve iteration for 3 times as an example (as shown in fig. 4).

D. Designing a common bone tissue engineering shape-divided support 3D model constructed by shape-divided tree curves which are orthogonal at 90 degrees and iterated for 0-3 times on the basis of the condition that the whole porosity of the support is the same, respectively calculating the porosity of each local area of the model (as shown in figure 5), and equally dividing the support into six areas a-f along the radius direction (as shown in figure 6). With the gradual increase of the iteration times, particularly the gradient of the pore change of the fractal-shaped scaffold in the bone tissue engineering after 3 times of iteration is gradually obvious, and the trend is similar to that from sparse to dense of cancellous bone to cortical bone. The fractal tree curve can realize the radial gradient porosity of the bone tissue engineering fractal support after fractal iteration for 3 times or more.

E. According to a normal adult femur CT reconstruction model, a hollow cylinder with the inner diameter of 8mm, the outer diameter of 22mm and the height of 3mm is selected as a target support.

F. And 3 times of iteration is carried out to construct the fractal scaffold for the radial gradient pore bone tissue engineering. Wherein, the branching angles of the fractal tree curves are respectively 40 degrees, 30 degrees and 12.8 degrees; the 2D fractal layer curve consists of 12 circular array fractal tree curves, and the 2D circular layer curve consists of seven circular rings with the diameter of 0.3mm and the equal spacing of 1.1167 mm.

G. A3D printing work flow of designing and manufacturing the fractal-shaped scaffold for the radial gradient pore bone tissue engineering is built in Grasshopper, and the physical geometric dimensions (inner diameter, outer diameter and height), fractal parameters, manufacturing code rules and the like of a target bone defect can be changed in a parameterization mode to construct the work flow of designing and manufacturing the radial gradient pore tissue engineering scaffold (as shown in figure 7). Where fig. 7A is a flow chart of this workflow and fig. 7B-J are cell diagrams of the implementation of this workflow in Grasshopper software. Fig. 7B is a geometric parameter of a target bone defect, fig. 7C is a fractal parameter required by a fractal tree curve, fig. 7D is a battery customized for fractal scaffold design, fig. 7E is a porosity gradient change analysis based on Grasshopper and Origin, fig. 7F is a 2D curve obtained by bone tissue engineering fractal scaffold CAD model and used for simulations of mechanical properties, permeability and other parameters by software such as Abaqus and Comsol, fig. 7G is a 2D curve obtained by bone tissue engineering fractal scaffold design and including a fractal layer and a circular ring layer, fig. 7H is a parameter writing rule of a manufacturing code of a commercial printer Bioscaffolder 3.1 used in the present invention, fig. 7I is a manufacturing code (G-code) generation instruction written based on GhPython, and fig. 7J is a manufacturing code format (. nc) recognizable by an output 3D printer.

H. And combining the steps C and G to obtain a manufacturing code (G-code) which can be used for guiding the motion of the 3D printer.

I. Polylactic-co-glycolic acid (PLGA) and 1, 4-dioxane were magnetically stirred at a ratio of 1g/2.5ml for 10 hours to prepare printing inks. The bottom of the support forming platform is a fixed-30 ℃ low-temperature cooling platform so that the ink is formed at low temperature after being deposited.

J. After the printing head height positioning and the low-temperature cooling platform height measuring operation of a commercial printer Bioscaffolder 3.1 and control software GeSiM thereof are completed, the printing head is controlled to deposit ink along a specified path by uploading a manufacturing code (G-code) obtained in the step I and secondarily developed by the invention, so that the preparation of the fractal-shaped bracket for the radial gradient pore bone tissue engineering provided by the invention is completed. Wherein the inner diameter of the printing head is 0.26mm, the extrusion air pressure is 400kPa, and the moving speed is 9 mm/s.

K. After the stent is formed by 3D printing, the 1, 4-dioxane is removed by a low-temperature freeze dryer to complete the final forming of the stent (as shown in figure 8).

L. CT image acquisition was performed using Micro-CT imaging system SkyScan1176 on 3D printed prepared 90 ° orthogonal (90 °), 0 iteration (N ═ 0) and 3 iterations (N ═ 3) bone tissue engineering scaffolds, and three-dimensional reconstruction of the scaffolds using their own software such as NRecon, DataViewer, CTAn, CTvox (as in fig. 9 a-c).

M. boolean operations were performed on the CT reconstructed stent model to obtain the overall porosity of the stent and the porosity of each portion along the radial equidistant regions (see fig. 9), where n.s. represents no significant difference in the one-way variance analysis, p ≦ 0.05 is considered significant difference between the data, p ≦ 0.01 is considered more significant difference between the data, and p ≦ 0.001 is considered very significant difference between the data. As a result, the total porosity of the bone tissue engineering scaffold was not significantly different among 90 ° orthonormal (90 °), 0 iteration (N ═ 0), and 3 iterations (N ═ 3) (as shown in fig. 9D). For local porosity, regions of the 90 ° orthogonal (90 °) scaffolds a-f were substantially horizontal and without significant differences (fig. 9A and 9E), with significant differences in regions of the scaffolds a-f from 0 iteration (N ═ 0) and 3 iterations (N ═ 3) (fig. 9B-C and 9E). Wherein, the porosity of the scaffold gradually increases from inside to outside (fig. 9B and fig. 9E) by 0 times of iteration (N ═ 0), and the porosity of the scaffold gradually decreases from inside to outside by 3 times of iteration (N ═ 3), and a gradient structure simulating the gradual decrease of the porosity of the "marrow cavity-cancellous bone-cortical bone" of the natural bone is realized (fig. 9C and fig. 9E).

The alternatives of the invention are as follows:

the 3D printing radial gradient bone tissue engineering fractal-shaped scaffold provided by the invention comprises but is not limited to scaffolds/materials applied to bone tissue engineering, tissue engineering and functional gradient.

As a further improvement of the invention, the "design-and-manufacture" workflow can be implemented in multiple pieces of software or in one piece of software, and the workflow can control different print heads of one printer or multiple 3D printers of the same brand or different brands to work.

As an improvement of the invention, the original curve of the fractal tree curve designed based on fractal theory can be modified into other line combinations.

As an improvement of the invention, the scaffold 3D model can be designed into a linear or nonlinear variable gradient pore bone tissue engineering scaffold along the radius direction.

As another improvement of the invention, the software required for the scaffold workflow construction includes but is not limited to Rhino, Grasshopper, Python, GeSiM.

As another improvement of the present invention, the 3D printer type used for the scaffold workflow construction includes, but is not limited to, Extrusion printing (Extrusion printing), inkjet printing (Inkjetprinting), Laser assisted printing (Laser assisted printing), wherein Extrusion printing includes, but is not limited to, a Bioscaffolder 3.1 printer.

As a further improvement of the present invention, the preparation technology includes, but is not limited to, SLM, EBM, SLA, etc. 3D printing or additive manufacturing technologies.

As a further improvement of the present invention, the printing ink includes but is not limited to a combination of two or more of PLGA, polylactic acid (PLA), calcium phosphate (. beta. -TCP), Hydroxyapatite (HA), hydrogel, etc., and different formulation thereof.

As a further improvement of the present invention, the printed bio-ink may comprise one or more cells.

Example 2

Example 3

The above-mentioned serial numbers of the embodiments of the present invention are merely for description and do not represent the merits of the embodiments.

In the above embodiments of the present invention, the descriptions of the respective embodiments have respective emphasis, and for parts that are not described in detail in a certain embodiment, reference may be made to related descriptions of other embodiments.

In the embodiments provided in the present application, it should be understood that the disclosed technical content can be implemented in other manners. The above-described system embodiments are merely illustrative, and for example, a division of a unit may be a logical division, and an actual implementation may have another division, for example, multiple units or components may be combined or integrated into another system, or some features may be omitted, or not executed. In addition, the shown or discussed coupling or direct coupling or communication connection between each other may be an indirect coupling or communication connection through some interfaces, units or modules, and may be electrical or in other forms.

The units described as separate parts may or may not be physically separate, and parts displayed as units may or may not be physical units, may be located in one place, or may be distributed on a plurality of units. Some or all of the units can be selected according to actual needs to achieve the purpose of the solution of the embodiment.

In addition, functional units in the embodiments of the present invention may be integrated into one processing unit, or each unit may exist alone physically, or two or more units are integrated into one unit. The integrated unit can be realized in a form of hardware, and can also be realized in a form of a software functional unit.

The integrated unit, if implemented in the form of a software functional unit and sold or used as a stand-alone product, may be stored in a computer readable storage medium. Based on such understanding, the technical solution of the present invention may be embodied in the form of a software product, which is stored in a storage medium and includes instructions for causing a computer device (which may be a personal computer, a server, or a network device) to execute all or part of the steps of the method according to the embodiments of the present invention. And the aforementioned storage medium includes: a U-disk, a Read-Only Memory (ROM), a Random Access Memory (RAM), a removable hard disk, a magnetic or optical disk, and other various media capable of storing program codes.

The foregoing is only a preferred embodiment of the present invention, and it should be noted that, for those skilled in the art, various modifications and decorations can be made without departing from the principle of the present invention, and these modifications and decorations should also be regarded as the protection scope of the present invention.

Claims

1. A bone tissue engineering shape-divided scaffold construction method is characterized by comprising the following steps:

obtaining a physical geometry of a target bone replacement;

on the basis of the 2D shape-dividing layer and the 2D circular layer, a 3D shape-dividing layer and a 3D circular layer are created according to the diameter of the tows and the height of the target bone substitute, and the 3D shape-dividing layer and the 3D circular layer are axially stacked to construct a bone tissue engineering shape-dividing support 3D model.

2. The method for constructing a bone tissue engineering fractal scaffold according to claim 1, wherein the method further comprises:

3. The method for constructing a bone tissue engineering fractal scaffold according to claim 2, wherein the method further comprises:

modifying and adjusting related feeding motion parameters of a printer until the diameter of the actually extruded tows of the 3D printer is close to that of the tows of the bone tissue engineering fractal support 3D model with radial gradient pores;

4. The method for constructing a bone tissue engineering fractal-shaped scaffold according to claim 1, wherein before 3D printing and manufacturing the bone tissue engineering fractal-shaped scaffold, the method further comprises:

5. The method for constructing a bone tissue engineering fractal scaffold according to claim 1, wherein the physical geometry of the target bone substitute is determined by means of Mimics medical processing software from CT or MRI medical image data.

6. The method for constructing the bone tissue engineering shape-divided scaffold according to claim 1, wherein a 2D shape-divided tree curve is determined according to the inner diameter size, the outer diameter size, the fractal primary pattern, the iteration rule and the iteration times of the physical geometric size of the target bone substitute.

7. The method for constructing a bone tissue engineering shape-divided scaffold according to claim 1, wherein on the basis of the 2D shape-divided layer and the 2D ring layer, a circle with the same diameter as the extruded filament bundle of the 3D printer moves along the 2D shape-divided layer and the 2D ring layer with the center as a reference point and the normal line of the center of the circle always coincides with the 2D line, and the circle is stretched and offset to form the 3D shape-divided layer and the 3D ring layer which are supported with each other. The bottom layer is a 3D shaping layer, the position of the 3D annular layer is located by shifting a numerical value of the distance between layers along the axial direction, and then the layers are sequentially stacked layer by layer along the axial direction until the height of the target bone defect is reached, so that the construction of the bone tissue engineering shape-divided support 3D model is completed.

8. The bone tissue engineering fractal scaffold construction method according to claim 3, wherein the 2D fractal layer curve and the 2D ring layer curve of the obtained bone tissue engineering fractal scaffold 3D model with radial gradient pores, the iteration number N of which is more than or equal to 3, are combined with a manufacturing code definition rule of a printer and a printer feeding motion parameter to construct a manufacturing code for the radial gradient pore tissue engineering scaffold by a Python programming language.

9. The method for constructing a bone tissue engineering shape-divided support according to claim 3, wherein the printer feed motion parameters comprise extrusion air pressure of printing ink, motion speed of a printing head, height of the printing head from a bottom receiving platform, and rheological properties of the ink.

10. The method for constructing the bone tissue engineering fractal-shaped scaffold according to claim 3, wherein the design and manufacturing codes of the whole 3D model are obtained in a parametric design software Grasshopper carried by the Rhino, the scaffold is subsequently prepared by 3D printing, and a design-manufacturing workflow of the 3D printing radial gradient pore bone tissue engineering fractal-shaped scaffold is constructed, wherein the workflow can be modified by one-key parameterization according to target requirements.