CN103751852A - Preparation method of three-dimensional artificial random porous structure tissue engineering scaffold - Google Patents

Abstract

The invention relates to a method for preparing a three-dimensional artificial random porous structure tissue engineering scaffold, which relates to the technical field of biomaterials. The present invention aims to solve the problem of design and manufacture of tissue engineering scaffold bionic structure, and proposes a design method for constructing a bionic shape randomly distributed scaffold porous structure under the desired porosity and pore diameter requirements, and adopts 3D additive manufacturing The method is shaped to make a tissue substitute. The advantages of the present invention are: the bracket has a 3D through-hole structure that meets the requirements of bionics, which ensures the transmission of nutrients and waste metabolism while also taking into account certain bionic mechanical properties; it can conveniently control the distribution range of the porosity and pore size of the bracket, and construct a bionic structure with Random pore structures with functional gradients are expected to achieve structural biomimetic properties; this method is applicable to a wide range of materials, such as: metal materials, non-metal materials, and medical polymer materials, etc., which can meet the user's personalized tissue repair needs.

Description

Preparation method of a three-dimensional artificial random porous structure tissue engineering scaffold

technical field

The invention belongs to the technical field of biomaterials, and is particularly suitable for the preparation of scaffold materials for biomedical tissue engineering, specifically a method for designing and preparing a three-dimensional artificial random structure tissue engineering scaffold.

Background technique

Tissue engineering is an emerging medical technology. It applies the principles and technologies of life science and engineering. Based on a correct understanding of the relationship between tissue structure and function in normal and pathological states, it researches and develops methods for repairing and maintaining various aspects of the human body. Biological substitutes for the function and shape of tissues and organs after damage have attracted much attention. Its core is a three-dimensional space complex composed of biological materials and cells. The basic method is to adsorb normal tissue cells cultured in vitro on a biological material with good biocompatibility and reasonable structure, and combine the cell-biological material In the in vivo environment, cells perform various physiological activities on biomaterials to achieve the purpose of repairing wounds.

The key to fabricating tissue engineering scaffolds is to fabricate their internal porous structure, and the shape of the pores will directly affect the growth process of cells. In principle, the function of scaffolds is to provide an environment to stimulate cellular behaviors such as: adhesion, migration, proliferation, differentiation, maintenance, and death through cell-scaffold, cell-cell interactions. Tissue engineering scaffolds can realize the initial support of tissues, the initial adhesion of cells and the controllable formation of cells into tissues or organs in in vivo or in vitro culture. An ideal scaffold should have these characteristics: 1) There is a connected high-porosity porous structure inside, which can adapt to cell growth, nutrient flow delivery and metabolite discharge; 2) Biocompatibility and tissue growth matching 3) Surface chemical characteristics that promote cell adhesion, proliferation, and differentiation; 4) Mechanical properties that match the surrounding tissue.

Anisotropic porosity can guide bone regeneration along the direction of porosity and mechanical strength gradients, which can control stem cell differentiation and promote tissue function. Different pore structures can affect the direction and speed of movement of cells approaching and away from the structure, which becomes a physiological mechanism by which the extracellular environment controls cell behavior. A random pore structure with a certain porosity is an ideal structure after natural selection and evolution. Compared with the regular porous structure, it has superior mechanical properties and permeability, has more diverse pore shapes to meet the different needs of cells, can ensure a certain porosity while taking into account certain mechanical strength requirements, and its 3D connectivity Pores facilitate the infusion of nutrients into the inside of the scaffold, discharge of cell metabolic waste, and create an environment conducive to cell growth.

In the manufacture of porous scaffolds, although there are some traditional manual methods such as: salt filtration method, gas foaming method, freeze-drying method, these methods can only achieve rough estimation of a few parameters (such as: porosity, pore size). tuning, fine control is not possible. Recently developed additive manufacturing technologies, such as selective laser sintering, laser rapid prototyping, free-body manufacturing, 3D printing, stereolithography and other technologies, have solved this problem and successfully applied to forming complex parts. Now, these technologies have also been introduced into the field of tissue engineering, and the results prove that this technology has the potential to be used to manufacture scaffold products with more complex and highly biomimetic pore structures and mechanical properties, and can precisely form the microscopic morphology of the scaffold and control the space of growth factors. Distribution to meet the needs of personalized tissue repair.

At present, there are still many difficulties in the design and construction of random porous scaffolds for additive manufacturing, such as: how to design a randomly distributed porous structure with bionic properties, and how to automatically determine the basic elements (position and shape) of irregular pores everywhere. , How to further control the pore size distribution and porosity distribution of the structure to meet the bionic needs and so on. These difficulties have become bottlenecks limiting the design, manufacture and application of biomimetic structural tissue engineering scaffolds.

Contents of the invention

The purpose of the present invention is to solve the problems that the traditional design method cannot flexibly and accurately construct the random porous structure, and the traditional preparation method has high cost, unstable process, residual pore-forming agent, low strength of the scaffold, etc., and provides a tissue engineering of a three-dimensional artificial random porous structure Preparation method of scaffold.

The preparation method of the tissue engineering scaffold of the three-dimensional artificial random porous structure provided by the present invention is to design the random porous structure based on the triple periodic minimal surface (TPMS) method, and to prepare the scaffold by the method of additive manufacturing. The specific steps are:

1. Establish a 3D digital internal and external model of the artificial random porous structure scaffold, the steps are:

a. Construct a random function so that the value range of the function is within the required range of porosity and pore size of natural bone;

b. Substituting the random function into the porosity control item and pore size control item in the TPMS implicit function, the internal shape structure of the scaffold is controlled by the constructed TPMS implicit function, and a 3D digital internal structure model of the scaffold is established;

c. According to the external shape data of natural tissue or the external shape data of the artificial implant, a 3D digital external surface model of the bracket is established.

d. Combining the internal structure model established in step b with the external surface model established in step c, the final generated solid model is exported in STL format to guide the subsequent 3D additive manufacturing process.

Second, the 3D additive manufacturing method is used to prepare artificial random porous structure scaffolds.

The 3D additive manufacturing method includes: selective laser sintering method, free entity manufacturing method, 3D printing method, and photocuring three-dimensional modeling method. Such as: selective laser sintering, the steps are:

Spread a thin layer of biological material powder on the working platform, and the computer controls the laser head to sinter only the powder in the specified area of the model in a specific area. After this layer is sintered, the computer control platform moves down a thin layer, and then spreads the powder again. The next layer is sintered, and the scaffold is formed by this layer-by-layer stacking method. The advantage of this technology is that the powder can act as a support structure to support the formed object of the previous layer, so any complex 3D pore structure can be manufactured.

As a tissue substitute, the scaffold has good pore connectivity and random distribution shape, which is beneficial for cells to obtain nutrients and discharge waste, while taking into account certain mechanical strength, providing cells with a benign 3D growth space. The present invention selects materials in the form of powder as forming raw materials, and the optional materials are extensive, including metals, non-metals, and medical polymer materials, etc., specifically: titanium, magnesium, bioactive glass, hydroxyapatite, and high biocompatibility Molecular materials (such as: polylactic acid and its polymers, polyglycolide, polylactic acid-polyglycolide copolymer, polycaprolactone, poly-β-hydroxybutyrate, poly-β-hydroxybutyrate-polyhydroxy valerate copolymer, polycaprolactone-polyethylene glycol multi-block copolymer or polyurethane).

Advantage of the present invention and beneficial effect are:

Using computer-aided design to design tissue engineering scaffolds with bionic functions and random pore structures, and to precisely manufacture this porous structure through additive manufacturing methods, it is possible to realize the preparation of personalized scaffolds for users. The porosity control term and pore size control term in the triple periodic minimum surface implicit function can conveniently control the distribution range of scaffold porosity and pore size, and then accurately construct random porous scaffold materials with desired pore parameters, and by changing Each control item can conveniently construct a random pore structure with a desired gradient to achieve various bionic properties. At the same time, the 3D additive manufacturing method adopted can accurately manufacture ideal products according to the model. The invention is applicable to a wide range of materials, and currently widely used in tissue engineering, metal materials, non-metal materials and many types of high molecular polymer materials with biological inertness/activity can be formed by the method of the invention. The products produced have: the overall connectivity of pores and entities, randomness of shape, and functional gradient, and take into account the porosity, pore size and biomechanical properties of human tissues/organs. It can not only be used as an implant material with excellent bone growth guidance and induction ability, but also can be used in scientific research: control the subtle changes in the internal structure of the scaffold, and investigate which porous scaffold can best meet the growth needs of specific cells.

Description of drawings

Fig. 1 is a slice diagram (a) of the artificial random porous structure cubic scaffold structure and height median layer of the present invention, and a comparison diagram with the regular porous structure and the slice (b).

Fig. 2 is a comparison diagram between the finished product of the artificial random porous structure cube support and the regular structure support of the present invention.

Figure 3 is a diagram of the external dimensions of the artificial joint components.

Fig. 4 is a 3D model diagram of the joint component adopting the scheme of the present invention.

Detailed ways

Example 1

The preparation method of the tissue engineering scaffold of the three-dimensional artificial random porous structure provided by the present invention is to design the random porous structure based on the triple periodic minimum surface method, and to prepare the scaffold by using the additive manufacturing method. The specific steps are:

1. Establish a 3D digital internal and external model of the artificial random porous structure scaffold, the steps are:

a. Construct a random function according to the distribution range of the porosity and pore size of the natural tissue, so that the function value range is within the distribution range;

Sprinkle t=27 regularly distributed 3D points into the cube, and the coordinates of each point are (t1[il,i2[il,x3[il), construct a random function:

$\mathrm{<span\; class="notranslate">\; f</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; x</span>}<span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; the\; y</span>}<span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; z</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; =</span>\underset{\mathrm{<span\; class="notranslate">\; i</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 0</span>}}{\overset{\mathrm{<span\; class="notranslate">\; t</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; \&Sigma;</span>}}}\mathrm{<span\; class="notranslate">\; h</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; i</span>}<span\; class="notranslate">\; )</span>\mathrm{<span\; class="notranslate">\; sin</span>}<span\; class="notranslate">\; (</span>\frac{{<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; x</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; x</span>}\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; [</span>\mathrm{<span\; class="notranslate">\; i</span>}<span\; class="notranslate">\; ]</span><span\; class="notranslate">\; )</span>}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; +</span>{<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; the\; y</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; x</span>}\mathrm{<span\; class="notranslate">\; 2</span>}<span\; class="notranslate">\; [</span>\mathrm{<span\; class="notranslate">\; i</span>}<span\; class="notranslate">\; ]</span><span\; class="notranslate">\; )</span>}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; +</span>{<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; z</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; x</span>}\mathrm{<span\; class="notranslate">\; 3</span>}<span\; class="notranslate">\; [</span>\mathrm{<span\; class="notranslate">\; i</span>}<span\; class="notranslate">\; ]</span><span\; class="notranslate">\; )</span>}^{\mathrm{<span\; class="notranslate">\; 2</span>}}}{\mathrm{<span\; class="notranslate">\; 30</span>}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; )</span>$

where h[i] is a random real number uniformly distributed between -1 and 1.

Solve the following constrained optimization problem:

Min(Max)f(x,y,z)

s.t.0≤x≤26

0≤y≤26

0≤z≤26 (2)

Wherein: the length, width and height of the cube support are all 26mm. Find the solution to the above problem, let the maximum value be Iila, and the minimum value be min. Let d1=2.32, d2=3.48 be the values of coefficients a, b, c in formula (4) corresponding to the maximum and minimum pore diameters required (here a=b=c), let k=(d2-d1 )/(max-min), m=d2-kmax is two linear conversion coefficients, constructs a new random function:

g(x,y,z)=kf(x,y,z)+m (3)

Its value range must be between d1 and d2.

b. Substituting the random function into the porosity control item and pore size control item in the triple periodic minimum surface implicit function, the internal shape structure of the scaffold is controlled by the constructed triple periodic minimum surface implicit function:

Choose the G-shaped triple periodic minimum surface implicit function:

θ(ax, by, cz, p)=Cos(ax)+Cos(by)+Cos(cz)+p (4) where a, b, c are pore size control items, p is porosity control item, θ (ax.by,cz,p)≤0 means that the space inside the scaffold is filled with solid material, and the others are pore spaces.

Substituting a=b=c=g(x, y, z), p=0 into formula (4), the pore diameter can be controlled to 1000-1500μm, and the pores

Rate control is about 50%.

c. Establish a 3D digital outer surface model of the stent according to the external shape data of the natural tissue or the shape data of the artificial implant;

The shape data is a cubic area, which is the constraint condition in formula (2):

s.t.0≤x≤26

0≤y≤26

0≤z≤26

d. Combine the internal structure model established in step b with the external surface model established in step c, and finally the generated model is saved in STL format and exported to guide the subsequent 3D additive manufacturing process;

2. Import the STL file into the 3D printer or the rapid prototyping machine input system, select the desired material, and then prepare the artificial random porous structure scaffold consistent with the model structure.

Adopt the method of the present invention to carry out computer-aided design, 3D design model as shown in Figure 1 (take a slice at the median height, convenient to show its 2D features), as can be seen from Figure 1, random pores have more variety than regular pores The pore structure is characterized by anisotropy everywhere. The model was exported in STL format and input into the additive manufacturing system, and the finished product of artificial random porous structure cube bracket was prepared by 2D layer stacking method ^. The pore size is 1000-1500μm, and the porosity is about 50%.

Example 2

Figure 3 is the design outline of the artificial joint components (see Example 1 for the specific design process). The required material is titanium metal. The radius of the outer surface of the hemisphere is 32mm, the radius of the inner surface is 26mm, and the eccentricity of the inner and outer spherical surfaces is 5.5mm. The thickness of the cylinder is the same as that of the spherical shell, the heights of the outer surface and the inner surface are 7mm and 12.2mm respectively, the top of the spherical shell is punched with a Ф3mm hole, and there are 6 equally spaced circular array of holes Ф6mm around it, the axis passes through the center of the outer spherical surface and The angle with the bottom surface is 50°. It is required that the surface layer is distributed with random porous structure, and the inner layer is a solid structure. The 3D model designed according to the present invention is as shown in Figure 4, the thickness of the porous layer is 3mm, and the rest is a solid layer, the porosity is about 67%, and the aperture is 1-1.5mm. The porous layer and the solid layer are integrated. There is no interface between them.

Examples show that the design model of the present invention can flexibly, automatically and accurately combine random porous structures and external shapes, avoid secondary processing in one step, ensure the required porosity and pore size, and cooperate with 3D additive manufacturing methods to accurately manufacture The scaffold structure required by the model is produced to meet the individual needs of bionics.

Claims (4)

1. the preparation method of the tissue engineering bracket of the artificial random loose structure of a three-dimensional, the method is based on three reset cycle minimal surfaces (triply periodic minimal surface, abbreviation TPMS) method designs random loose structure, and adopt increasing material manufacture method to prepare this support, concrete steps are:

1st, the inside and outside model of 3D digitized of setting up artificial random loose structure support, step is:

A, structure random function, make function value in the porosity of natural bone, in the claimed range of pore-size;

B, by the porosity control item in random function substitution TPMS implicit expression function and pore-size control item, the external morphology structure of support is controlled by constructed TPMS implicit expression function, sets up the digitized internal structure model of support 3D;

C, according to the external shape data of natural fabric or the shape data of artificial implantation, set up the 3D digitized outer surface model of support;

The outer surface model that d, the internal structure model that b step is set up and c step are set up combines, and generates final physical model and derives with STL form, in order to instruct follow-up 3D to increase material manufacture process;

2nd, adopt 3D to increase the artificial random loose structure support of material manufacture method preparation.

2. method according to claim 1, is characterized in that described 3D increases material manufacture method and comprises: selective laser sintering method, free entity autofrettage, 3D impact system, and photocuring three-dimensional contouring method.

3. method according to claim 2, is characterized in that the concrete steps of described increasing material manufacture process are:

Work platforms is spread to the biomaterial powder of a thin layer, by the powder in computer control laser head Sintering Model appointed area, this one deck sintering is complete, computer control platform moves down the distance of a thin layer, again spread powder, one deck under sintering, until support reaches desired height, so support entity is made by this accumulation mode in layer.

4. method according to claim 3, is characterized in that described dusty material is: titanium, magnesium, bioactivity glass, hydroxyapatite and biocompatible polymer material (as: polylactic acid and polymer thereof, PGA, polylactic acid-PGA copolymer, polycaprolactone, poly-beta-hydroxy-butanoic acid ester, poly-beta-hydroxy-butanoic acid ester-poly-hydroxyl pentanoate copolymer, polycaprolactone-polyethylene glycol segmented copolymer or polyurethane).

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