4D printing composite scaffold for repairing irregular bone defects, preparation method and application thereof

Abstract

The invention discloses a 4D printing composite scaffold for repairing irregular bone defects and a preparation method and application of the 4D printing composite scaffold. The scaffold has a negative Poisson's ratio structure, is prepared from a body fluid responsive hydrogel material through 4D printing, and can be spontaneously converted into a target shape matched with a bone defect part from an initial shape in a body fluid environment. According to the 4D printing composite stent for repairing the irregular bone defect, provided by the invention, aiming at the core contradiction that the shape of a traditional 3D printing stent is fixed and the irregular bone defect is complex in form and difficult to accurately prejudge before an operation, accurate matching of the defect form before the operation is not needed by virtue of the synergistic effect of the body fluid responsive material and the negative Poisson's ratio structure; when implanted, the stent enters in a compressed state in a minimally invasive mode, spontaneously deforms under stimulation of body fluid after an operation, and finally is highly attached to the contour of a defect part, the limitation that a traditional stent needs to be polished on site and is difficult to adapt to complex defects is thoroughly eliminated, and fundamental crossing from static geometric matching to dynamic function self-adaption is achieved.

Description

Technical Field

[0001] This invention belongs to the field of biomaterials technology, specifically, it relates to a 4D-printed composite scaffold for repairing irregular bone defects, its preparation method and its application. Background Technology

[0002] In the fields of orthopedic clinical treatment and basic research, irregular bone defects caused by trauma, tumors, or infections have always been a core challenge for orthopedic surgeons and researchers. Currently, autologous bone transplantation remains the recognized "gold standard" for the clinical treatment of irregular bone defects, but its application has significant limitations. It may not only cause complications such as poor wound healing and infection at the donor site, but also often leads to pain and loss of sensation in the donor area. In severe cases, it may even require a second surgery, placing an additional burden on the patient's physical and mental well-being.

[0003] Compared to autologous bone transplantation, allogeneic bone transplantation, while addressing the scarcity of bone tissue to some extent, still faces significant challenges. As a foreign tissue, allogeneic bone is prone to triggering recipient immune rejection and carries the potential risk of infection transmission, severely limiting its clinical application. To compensate for the shortcomings of both autologous and allogeneic bone transplantation, artificial materials such as titanium alloys and polyetheretherketone (PEEK) have been gradually introduced as bone graft substitutes in clinical practice. While these materials possess excellent mechanical properties and can meet the support requirements of bone tissue, they generally suffer from incomplete tissue interface integration during the integration process with the host bone tissue. This interface defect directly leads to the inability to form a stable connection between the graft and the host bone, resulting in graft loosening and detachment, ultimately causing functional bone repair failure and hindering the achievement of ideal treatment outcomes.

[0004] Although researchers have developed a variety of biomaterials for bone regeneration in an attempt to solve the above problems, most of them lack the ability to actively adapt to irregular bone defect morphology due to the physical properties of the materials themselves. They cannot accurately match the complex contours of the defect area, which greatly reduces their application value in the repair of irregular bone defects.

[0005] The emergence of 3D printing technology has brought new ideas to the repair of irregular bone defects. Theoretically, 3D printing can produce bone repair materials that closely match the morphology of bone defects. However, in actual clinical surgery, due to the uncertainty of surgical procedures and the discrepancy between the actual morphology of the bone defect area and the preoperative imaging assessment, the implantation of 3D-printed bone repair materials often requires on-site grinding and adjustment. This process not only prolongs the operation time but may also enlarge the patient's wound and increase the risk of postoperative infection, thus hindering its clinical promotion.

[0006] 4D printing technology has achieved a performance breakthrough compared to 3D printing. The components it produces can dynamically adjust their shape, properties, and functions over time under predetermined external stimuli (such as heat, water, light, and pH changes). Based on this characteristic, theoretically, 4D-printed bone scaffolds can undergo rapid morphological changes after implantation, using the in vivo physiological environment or controlled external stimuli, to match the contours of irregular bone defects. This allows for a complete and stable interface with the host bone tissue, potentially improving bone repair outcomes.

[0007] From a materials and structural design perspective, most traditional bone repair scaffolds currently employ a positive Poisson's ratio lattice structure. The mechanical properties of this structure limit its compressibility and expansion capacity, making it difficult to meet the clinical needs of minimally invasive implantation. In contrast, negative Poisson's ratio materials possess unique mechanical response characteristics. When longitudinal tensile strain is applied, the material expands laterally; when longitudinal compressive strain is applied, it contracts laterally. Utilizing this property in bone repair scaffold design allows the scaffold to be compressed to a minimum volume in three dimensions, enabling implantation through smaller incisions, achieving minimally invasive treatment goals, and reducing surgical trauma to patients.

[0008] Therefore, combining 4D printing technology with negative Poisson's ratio structures, and giving full play to the advantages of both in terms of morphological adaptability and minimally invasive implantation, has important clinical significance for overcoming the technical bottleneck of repairing irregular bone defects.

[0009] In view of this, the present invention is proposed. Summary of the Invention

[0010] The technical problem to be solved by the present invention is to overcome the shortcomings of the prior art and provide a 4D printed composite scaffold for repairing irregular bone defects, its preparation method and its application.

[0011] To achieve the above objectives, the technical solution of the present invention is as follows: In a first aspect, the present invention provides a 4D-printed composite scaffold for repairing irregular bone defects. The scaffold has a negative Poisson's ratio structure and is made of a body fluid responsive hydrogel material by 4D printing. It can spontaneously transform from an initial shape to a target shape that matches the bone defect site in a body fluid environment.

[0012] In a preferred embodiment, the fluid-responsive hydrogel material is formulated by mixing fluid-responsive hydrogel ink and bone cement powder.

[0013] In a preferred embodiment, the fluid-responsive hydrogel material comprises fluid-responsive hydrogel ink and bone cement powder in a mass ratio of 80% and 20%, respectively.

[0014] In a preferred embodiment, the body fluid-responsive hydrogel ink is formulated from the following components, with the remainder being ultrapure water: 10% w / v hydrogel material; 10% w / v polyethylene glycol diacrylate; 3‰ w / v sodium polyacrylate; 1% w / v photoinitiator; 0.025% w / v light absorber.

[0015] In a preferred embodiment, the hydrogel material includes at least one of gelatin, sodium alginate, and chitosan.

[0016] In a preferred embodiment, the photoinitiator is lithium phenyl-2,4,6-trimethylbenzoylphosphinate.

[0017] In a preferred embodiment, the light-absorbing agent is lemon yellow.

[0018] Secondly, the present invention provides a method for preparing a 4D-printed composite scaffold for repairing irregular bone defects as described above, comprising the following steps: S1. Prepare body fluid responsive hydrogel materials according to the formula; S2. Design a three-dimensional model with a negative Poisson's ratio structure according to the required deformation effect; S3. Use 4D printing technology to print the body fluid responsive hydrogel material into a scaffold.

[0019] In a preferred embodiment, the printing parameters in step S3 are: Light intensity 3mW / cm 2 ; Number of base layers: 20; Exposure time: 12 seconds; Grassroots exposure time: 20 seconds; The peeling distance is 3mm; Peeling speed 20 mm / min; Peeling recovery speed: 180 mm / min; Lift height 1mm; Lifting speed 100mm / min; The platform temperature is controlled at 40℃; The temperature of the material tank is controlled at 40℃.

[0020] Thirdly, the present invention provides the application of the 4D-printed composite scaffold for repairing irregular bone defects as described above in the preparation of medical devices for repairing irregular bone defects.

[0021] After adopting the above technical solution, the 4D printed composite scaffold for repairing irregular bone defects, the preparation method and its application provided by the present invention have the following beneficial effects compared with the prior art.

[0022] (1) The 4D-printed composite scaffold for repairing irregular bone defects provided by this invention addresses the core contradiction between the "fixed shape" of traditional 3D-printed scaffolds and the "complex morphology and difficulty in accurate preoperative prediction" of irregular bone defects. Relying on the synergistic effect of fluid-responsive materials and negative Poisson's ratio structure, it eliminates the need for precise preoperative matching of defect morphology. During implantation, it enters in a compressed state with minimal invasiveness. After surgery, it spontaneously deforms under the stimulation of body fluids, ultimately achieving a high degree of fit with the contour of the defect site. This completely eliminates the limitations of traditional scaffolds that require on-site grinding and are difficult to adapt to complex defects, achieving a fundamental leap from "static geometric matching" to "dynamic functional self-adaptation".

[0023] (2) The 4D-printed composite scaffold for repairing irregular bone defects provided by this invention significantly improves the minimally invasiveness and precision of the surgery. With the mechanical property of "longitudinal compression and transverse contraction" of the negative Poisson's ratio structure, the scaffold can be compressed to its minimum volume in three dimensions, requiring only a smaller incision for implantation, greatly reducing surgical trauma to patients. At the same time, after implantation, the scaffold can autonomously deform and fit the defect through body fluids, eliminating the need for complex adjustments by medical staff during the operation, reducing the difficulty and duration of the operation, and reducing the risk of complications such as postoperative infection and poor wound healing, truly meeting the clinical needs for minimally invasive and precise treatment.

[0024] (3) The 4D-printed composite scaffold for repairing irregular bone defects provided by the present invention enhances the integration effect between the scaffold and the host tissue. The process of the scaffold dynamically fitting the defect can form a complete and tight tissue interface, avoiding the loosening and detachment problems caused by the incomplete interface of traditional scaffolds. On the other hand, the composite system of body fluid responsive hydrogel and bone cement used in the scaffold not only has excellent biocompatibility, but also provides a suitable microenvironment for bone regeneration, promotes the spread, proliferation and formation of new bone tissue of rat mesenchymal stem cells, effectively shortens the bone healing cycle and improves the stability and success rate of repair.

[0025] (4) The 4D-printed composite scaffold for repairing irregular bone defects provided by this invention endows tissue engineering scaffolds with "intelligent" attributes, transforms the repair process from passive support to active intervention, realizes the controllability of repair function in time and space, and represents the development direction of the next generation of bone repair materials. Attached Figure Description

[0026] The accompanying drawings, as part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments and descriptions of the invention are used to explain the invention, but do not constitute an undue limitation of the invention. Obviously, the drawings described below are merely some embodiments, and those skilled in the art can obtain other drawings based on these drawings without creative effort. In the drawings: Figure 1 This is a schematic diagram of the shape design of a 4D-printed composite scaffold for repairing irregular bone defects provided by the present invention; Figure 2 It provides a negative Poisson structure deformation simulation of a 4D-printed composite scaffold shape for repairing irregular bone defects; Figure 3 This is a schematic diagram of the compression and swelling results of the hydrogel scaffold sample provided by the present invention; Figure 4 This is a schematic diagram of the compression and swelling results of the hydrogel-bone cement scaffold sample provided by the present invention; Figure 5 This is a CT image of the hydrogel-bone cement scaffold sample provided by the present invention; Figure 6 This is a diagram showing the results of a live / dead staining experiment on a hydrogel-bone cement scaffold sample provided by the present invention. Figure 7 This is a schematic diagram of the cytoskeleton staining results of the hydrogel-bone cement scaffold sample provided by the present invention. Figure 8 This is a schematic diagram of the CCK-8 cell proliferation and cytotoxicity detection results of the body fluid responsive hydrogel material provided by the present invention; Figure 9 This is a schematic diagram of the in vivo modeling experiment results of the hydrogel-bone cement scaffold sample provided by the present invention; Figure 10 This is a schematic diagram of the hematoxylin-eosin staining results of a sample tissue after the dehydration scaffold provided by this invention was placed in an irregular defect for 8 weeks; Figure 11 This is a schematic diagram of the results of the Masson staining experiment on the sample tissue after the dehydration scaffold provided by this invention was placed in an irregular defect for 8 weeks.

[0027] It should be noted that these accompanying drawings and textual descriptions are not intended to limit the scope of the invention in any way, but rather to illustrate the concept of the invention to those skilled in the art by referring to specific embodiments. Detailed Implementation

[0028] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments will be clearly and completely described below with reference to the accompanying drawings. The following embodiments are used to illustrate the present invention, but are not intended to limit the scope of the present invention.

[0029] In the description of this invention, it should be noted that the terms "upper", "lower", "front", "rear", "left", "right", "vertical", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention 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 limiting this invention.

[0030] [Example 1] This embodiment provides a 4D-printed composite scaffold for repairing irregular bone defects. The scaffold has a negative Poisson's ratio structure and is made of a body fluid responsive hydrogel material by 4D printing. It can spontaneously transform from its initial shape to a target shape that matches the bone defect site in a body fluid environment.

[0031] It should be noted that fluid responsiveness refers to the ability of a material to swell, degrade, or exhibit shape memory effects upon contact with bodily fluids, thereby driving the overall deformation of the scaffold.

[0032] Most traditional bone repair scaffolds use a positive Poisson's ratio lattice structure, which limits their compressibility or expansion capacity. A negative Poisson's ratio structure is a tensile structure, such as a periodic arrangement of concave hexagonal, arrowhead-shaped, or star-shaped cavities. Using a negative Poisson's ratio structure allows the scaffold to compress to a minimum in three dimensions, achieving minimally invasive implantation. This structure allows the scaffold to expand laterally under pressure, thus better conforming to and supporting the defect cavity.

[0033] This invention incorporates time as a fourth dimension, overcoming the limitations of traditional 3D printing for static scaffold manufacturing. The scaffold is not static after implantation but undergoes controllable changes in shape, volume, or performance under predetermined stimuli. This application prints an easily implantable compressible structure using a negative Poisson's ratio design. Under external pressure, the scaffold rotates, compressing the ribs to achieve overall compression; during swelling, the opposite occurs. Swelling and deformation are completed within the body, perfectly fitting the defect area.

[0034] Hydrogel materials are a key foundation for this invention, and the fluid-responsive hydrogel material provided by this invention possesses the ability to respond to bodily fluids. Specifically, the fluid-responsive hydrogel material is formulated by mixing fluid-responsive hydrogel ink and bone cement powder in weight proportions of 80% and 20%, respectively, wherein the bone cement is calcium phosphate bone cement. The fluid-responsive hydrogel material provided by this invention exhibits excellent biocompatibility, and its mechanical strength is controlled through composite materials. The scaffold that perfectly conforms to the defect can promote cell migration, thereby achieving earlier bone repair.

[0035] Furthermore, the body fluid-responsive hydrogel ink is formulated with the following components, the remainder being ultrapure water: A 10% w / v hydrogel material, including at least one of gelatin, sodium alginate, and chitosan, preferably methacrylamide gelatin (GelMA); 10% w / v polyethylene glycol diacrylate (PEGDA); 3‰ w / v sodium polyacrylate PAAS; A 1% w / v photoinitiator, preferably lithium phenyl-2,4,6-trimethylbenzoylphosphine; 0.025% w / v light absorber, preferably lemon yellow.

[0036] Methacrylamide gelatin (GelMA) is a double-bond modified gelatin that can be cross-linked and cured into a gel under ultraviolet and visible light with the aid of a photoinitiator. GelMA combines the characteristics of both natural and synthetic biomaterials. Polyethylene glycol polyacrylate (PEGDA) has excellent molding properties, but both are relatively brittle. Therefore, this invention introduces sodium polyacrylate (PAAS) to improve mechanical properties. Calcium phosphate bone cement, when mixed with hydrogel, undergoes self-curing upon contact with body fluids, which can stabilize scaffolds that have adapted to the shape of the defect.

[0037] [Example 2] This embodiment provides a method for preparing the 4D-printed composite scaffold for repairing irregular bone defects as described in the previous embodiments, including the following steps: S1. Prepare body fluid responsive hydrogel materials according to the formula; S2. Design a three-dimensional model with a negative Poisson's ratio structure according to the required deformation effect; S3. Use 4D printing technology to print the body fluid responsive hydrogel material into a scaffold.

[0038] As an example, step S1 includes: S11. Prepare body fluid responsive hydrogel ink by dissolving 10g lyophilized GelMA + 10g PEGDA aqueous solution + 0.6g PAAS (50% concentration) aqueous solution + 1g photoinitiator phenyl-2,4,6-trimethylbenzoyl lithium phosphine (LAP) + 0.025g light absorber tartrazine in 88.375g ultrapure water and stirring magnetically to dissolve. S12. The body fluid responsive hydrogel ink prepared in S11 and calcium phosphate bone cement powder are vortex-mixed at a ratio of 80% hydrogel ink + 20% bone cement powder to obtain a body fluid responsive hydrogel material.

[0039] The bracket shape design in step S2 is as follows: Figure 1 As shown, Abaqus was used to perform dynamic analysis. Figure 2The stress distribution of structures with different bar diameters and a cell size of 4 mm under tensile stress simulation at 15% and 30% strain is shown. To investigate the effect of different bar diameters on the negative Poisson's ratio effect of the structure, a point set was set in the tensile simulation to output the average displacement in different directions. The strain in each direction of the structure under tension was calculated, and the change of Poisson's ratio under tension was finally obtained. As shown in the figure, the smaller the bar diameter, the stronger the negative Poisson's ratio effect exhibited by the chiral structure.

[0040] In step S3, the BP8601PRO projection-type photopolymer 3D printer from Suzhou Yongqinquan Intelligent Equipment Co., Ltd. is used for printing. The printing parameters are shown in the table below.

[0041] Table 1 Printing Parameters

[0042] The above method was used to print the scaffold sample, in which: Figure 3 The comparative sample is printed with body fluid responsive hydrogel ink without bone cement powder. The hydrogel scaffold is printed with a size of 7*7*7mm, which becomes 4*4*3.5mm after dehydration and compression, and 8*8*8mm after re-swelling. The volume can change by 9 times from compression to re-swelling, and the recovery time after compression is 120-150 seconds.

[0043] Figure 4 The sample was printed from a fluid-responsive hydrogel material including bone cement. The hydrogel-bone cement scaffold was printed with a size of 7*7*7mm. After dehydration and compression, it became 5*5*4mm, and after re-swelling, it became 8*8*8mm. The volume can change by 5 times from compression to re-swelling. The recovery time after compression is 12-15 minutes.

[0044] The addition of bone cement reduces the rate of change in the stent's volume, increases the recovery time after compression, and enhances the controllability of the stent's shape changes under the stimulation of body fluids.

[0045] Figure 5 This is a CT image of a hydrogel-bone cement scaffold sample. The CT scan shows that the bone cement is uniformly distributed within the hydrogel scaffold.

[0046] Figure 6The images show the results of the live / dead staining assay for hydrogel-bone cement scaffold samples. The assay was performed using the Beyotime Calcein / PI Cell Viability and Cytotoxicity Assay Kit (catalog number C2015S). Control group consisted of pure cell culture; GelMA group consisted of 10% GelMA hydrogel-cured patches co-cultured with cells; GPP group consisted of humor-responsive hydrogel ink-cured patches co-cultured with cells; and GPPC group consisted of humor-responsive hydrogel material including bone cement-cured patches co-cultured with cells (the same applies below). The results showed no significant dead cells in any group, demonstrating good biocompatibility of the material.

[0047] Figure 7 The results of the cytoskeleton staining experiment on the hydrogel-bone cement scaffold samples were obtained by Solarbio FITC-labeled phalloidin + Beyotime DAPI C1002. The results showed that the cytoskeleton was well-distributed and exhibited high survival rate in rat mesenchymal stem cells co-cultured with different materials.

[0048] Figure 8 To detect the proliferation and cytotoxicity of CCK-8 cells in the body fluid responsive hydrogel material, the Biosharp CCK-8 kit (trade code: BS350B) was used. Results showed that after 7 days of culture, there was no statistically significant difference in cell proliferation and cytotoxicity between the body fluid responsive hydrogel material and the control group.

[0049] Figure 9 The results of the in vivo modeling experiment of the hydrogel-bone cement scaffold sample show that after the dehydrated scaffold is placed in an irregular defect, it can adapt to the defect shape by swelling in response to body fluid.

[0050] Figure 10 and 11 The images show the results of hematoxylin-eosin staining and masson staining experiments on tissue samples 8 weeks after the dehydrated scaffold was placed in the irregular defect. It can be seen that the deformed scaffold completely fits the defect area, and new bone tissue grows along the scaffold.

[0051] [Example 3] The foregoing embodiments illustrate the application of the 4D-printed composite scaffold for repairing irregular bone defects in the fabrication of medical devices for repairing irregular bone defects. This medical device is implanted into the defect in its initial shape, expands and deforms using bodily fluids, ultimately filling and fixing the defect, conforming to the defect area, and spontaneously transforming into a target shape that matches the bone defect site.

[0052] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0053] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some modifications or alterations to the above-described technical content to create equivalent embodiments without departing from the scope of the present invention. The implementation schemes in the above embodiments can also be further combined or replaced. Any simple modifications, equivalent changes and alterations made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the scope of the present invention.

Claims

1. A 4D printed composite scaffold for repairing an irregular bone defect, characterized in that: The scaffold has a negative Poisson's ratio structure, is made of a body fluid responsive hydrogel material by 4D printing, and can spontaneously transform from an initial shape to a target shape matching the bone defect site in a body fluid environment.

2. The stent of claim 1, wherein: The body fluid responsive hydrogel material is mixed and prepared from a body fluid responsive hydrogel ink and a bone cement powder.

3. The stent of claim 2, wherein: In the body fluid responsive hydrogel material, the mass ratio of the body fluid responsive hydrogel ink and the bone cement powder is 80% and 20%, respectively.

4. The stent of claim 2 or 3, wherein, The body fluid responsive hydrogel ink is prepared from the following components, with the rest being ultrapure water: 10% w / v hydrogel material; 10% w / v polyethylene glycol diacrylate; 3‰ w / v sodium polyacrylate; 1% w / v photoinitiator; 0.025% w / v light absorber.

5. The stent of claim 4, wherein: The hydrogel material includes at least one of gelatin, sodium alginate, and chitosan.

6. The stent of claim 4, wherein: The photoinitiator is lithium phenyl-2,4,6-trimethylbenzoyl phosphinate.

7. The stent of claim 4, wherein: The light absorber is lemon yellow.

8. A method for preparing a 4D-printed composite scaffold for repairing irregular bone defects according to any one of claims 1-7, characterized in that, The method includes the following steps: S1, preparing the body fluid responsive hydrogel material according to the formula amount; S2, designing a three-dimensional model with a negative Poisson's ratio structure according to the required deformation effect; S3, printing the body fluid responsive hydrogel material into a scaffold using 4D printing technology.

9. The method of claim 8, wherein the 4D-printed composite scaffold for repairing an irregular bone defect is prepared by the steps of: (a) preparing a 4D-printed composite scaffold for repairing an irregular bone defect; and (b) implanting the 4D-printed composite scaffold for repairing an irregular bone defect into a patient. In step S3, the printing parameters are as follows: Light intensity 3 mW / cm 2 ; Base layer number 20; Exposure time 12 s; Base layer exposure time 20 s; Peeling distance 3 mm; Peeling speed 20 mm / min; Peeling recovery speed 180 mm / min; Lifting height 1 mm; Lifting speed 100 mm / min; Platform temperature control 40℃; Chute temperature control 40℃.

10. Use of a 4D printed composite scaffold for repairing irregular bone defects according to any one of claims 1-7 in the preparation of a medical device for repairing irregular bone defects.

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