Photocurable 3d-printed bioceramic osteochondral scaffold and preparation method therefor

Abstract

A photocurable 3D-printed bioceramic osteochondral scaffold, comprising a cartilage repair layer and a subchondral bone repair layer that are formed of the same material, wherein the cartilage repair layer has a porous structure having a first pore size, and the first pore size is 100-1000 µm; the subchondral bone repair layer has a porous structure having a second pore size, and the second pore size is 300-1000 µm; the cartilage repair layer and the subchondral bone repair layer interdigitate at the interface to form a porous structure having a third pore size, and the third pore size is 50-300 µm; the third pore size is less than the first pore size and the second pore size. The osteochondral scaffold can not only ensure the infiltration of bone marrow blood carrying bioactive substances such as bone marrow mesenchymal stem cells and growth factors into cartilage defect sites, but also prevent vascular invasion from the subchondral bone repair layer, thereby inhibiting calcification of the cartilage layer; and the subchondral bone repair layer provides sufficient support for the repair of the cartilage layer during the repair process.

Description

Photopolymerization 3D Printing of Bioceramic Osteocartilage Scaffolds and Their Preparation Methods

[0001] Cross-references to related applications

[0002] This application claims the benefit and priority of Chinese Patent Application No. 202411535652.5, filed on October 31, 2024, entitled “Photocuring 3D Printing Bioceramic Osteocartilage Scaffold and Preparation Method Thereof”, the entire contents of which are incorporated herein by reference. Technical Field

[0003] This invention relates to the field of medical biomaterial preparation and tissue engineering technology. Specifically, this invention relates to a photopolymerization 3D printed bioceramic osteocartilage scaffold and its preparation method. Background Technology

[0004] Articular cartilage is a vital structure in human joints, playing a crucial role in motor function. Due to its unique structure and poor healing ability, articular cartilage is difficult to repair itself once damaged, severely impacting joint function and forcing many athletes to retire. For the general population, articular cartilage damage typically accelerates joint degeneration, leading to osteoarthritis and significantly affecting quality of life. Therefore, articular cartilage injury is a common and difficult-to-treat joint disease in clinical practice, and its repair and regeneration remain a key and challenging topic in sports medicine and orthopedic surgery.

[0005] Traditional cartilage repair surgeries, such as debridement and microfracture surgery, can improve symptoms in some patients, but the newly formed cartilage tissue is usually fibrocartilage. Fibrocartilage is not durable and the long-term treatment effect of the surgery is poor.

[0006] With advancements in biomaterials science, cell-free scaffold methods have recently emerged. These scaffolds are made from biomaterials that allow for cell adhesion and differentiation to support cartilage tissue regeneration. These scaffolds can be combined with microfracture techniques to cover bone marrow stimulation sites, stabilizing blood clots and enhancing the differentiation of cellular precursors into chondrocytes. On the other hand, the condition of the subchondral bone is considered a key factor influencing articular cartilage regeneration. Therefore, a new therapeutic principle focusing on cartilage and subchondral bone tissue has been developed: an innovative double-layer scaffold has been invented and introduced into clinical application. This technique requires only a single surgery and provides regenerative support for the proliferation and differentiation of resident cells into subchondral bone and cartilage tissue.

[0007] Currently, cartilage repair scaffold products can be categorized into two types based on their phase structure: gel-based and multilayer scaffold (membrane)-based. Gel-based products are typically made from collagen or chitosan gels, such as ChondroFiller, Coltrix CartiRegen, JointRep, and BST-Cargel. These products gel in situ after injection into the damaged area, offering advantages such as minimally invasive procedures and simple surgical manipulation. However, gels have relatively weak mechanical strength and degrade rapidly, generally making them unsuitable for repairing severe or long-term cartilage injuries. Scaffold-based products, on the other hand, are two- or three-layer scaffold or membrane structures, such as MaioRegen, Chondro-Gide, and ChondroMimetic. These scaffolds usually require fixation via sutures or adhesives after implantation. However, due to significant differences in mechanical strength between different layers of the scaffold, weak interlayer adhesion, and insecure fixation, the scaffold may loosen, delaminate, or even disintegrate within the body, leading to repair failure.

[0008] The method of fixing the scaffold to the wound is crucial for successful cartilage repair. Traditional cartilage scaffold products use methods such as in-situ gelation, adhesive bonding, or sutures for fixation, but due to weak adhesive strength and poor mechanical properties, it is difficult to guarantee the long-term stability of the implant. Cartiheal's Agili-C uses an aragonite scaffold formed from calcined coral bone as its raw material, and the scaffold has good mechanical properties. However, Agili-C's raw material is coral bone, and coral is a scarce natural resource in my country, making large-scale commercial development unlikely. In addition, the microstructure of calcined coral is difficult to control, which is not conducive to product standardization. To achieve the desired effect, biomaterials must be injected into the scaffold, but this still cannot change the rigid structure of the scaffold itself, introducing many unstable factors into the cartilage repair process. Therefore, there is an urgent need to find a cartilage scaffold that can be firmly fixed to the wound, has good mechanical properties, and can guarantee the long-term stability of the implant. Summary of the Invention

[0009] To address the problems existing in the prior art, this invention provides a photopolymerization 3D printing bioceramic osteocartilage scaffold and its preparation method.

[0010] On one hand, this invention provides a photopolymerization 3D-printed bioceramic osteocartilage scaffold, comprising a cartilage repair layer and a subchondral bone repair layer formed of the same material, wherein,

[0011] The cartilage repair layer includes a porous structure with a first pore size of 100-1000 μm.

[0012] The subchondral bone repair layer includes a porous structure with a second pore size of 300-1000 μm.

[0013] The cartilage repair layer and the subchondral bone repair layer are adjacent to each other and are constructed such that they interweave at the interface to form a porous structure with a third pore size of 50-300 μm.

[0014] The first pore diameter, the second pore diameter, and the third pore diameter satisfy the following conditions: the third pore diameter is smaller than the first pore diameter, the third pore diameter is smaller than the second pore diameter, and the size of the third pore diameter is sufficient to prevent blood vessels from invading the cartilage repair layer.

[0015] In some embodiments of the present invention, the first aperture is 600-800 μm.

[0016] In some embodiments of the present invention, the second pore size is 400–600 μm.

[0017] In some embodiments of the present invention, the third aperture is 100–300 μm.

[0018] In some embodiments of the present invention, the pore wall thickness of the porous structure of the cartilage repair layer is 100-300 μm.

[0019] In some embodiments of the present invention, the pore wall thickness of the porous structure of the subchondral bone repair layer is 200-400 μm.

[0020] In some embodiments of the present invention, the osteocartilage scaffold is generally frustum-shaped, wherein the cartilage repair layer forms the upper part of the frustum and the subchondral bone repair layer forms the lower part of the frustum.

[0021] In some embodiments of the present invention, the taper of the frustum is 1:100 to 1:20.

[0022] In some embodiments of the present invention, the cartilage repair layer is mainly composed of a vertical pore structure, which is consistent with the arrangement of chondrocytes.

[0023] In some embodiments of the present invention, the cartilage repair layer is further provided with side holes.

[0024] In some embodiments of the present invention, the porosity of the cartilage repair layer is 50%-80%.

[0025] In some embodiments of the present invention, the porosity of the subchondral bone repair layer is 40%-60%.

[0026] In some embodiments of the present invention, the pore walls of the cartilage repair layer and the subchondral bone repair layer are rounded or chamfered.

[0027] In some embodiments of the present invention, the photocurable 3D printing paste for forming the cartilage repair layer and the subchondral bone repair layer includes one or more of the following substances: hydroxyapatite, β-tricalcium phosphate, and bioactive glass.

[0028] In some embodiments of the present invention, the solid volume fraction of the photocurable 3D printing slurry forming the cartilage repair layer and the subchondral bone repair layer is 40% to 58%.

[0029] In some embodiments of the present invention, the viscosity of the photocurable 3D printing slurry used to form the cartilage repair layer and the subchondral bone repair layer is 400–8580 mP·s.

[0030] On the other hand, the present invention provides a method for preparing a photopolymerizable 3D printed bioceramic osteocartilage scaffold, the method comprising the following steps:

[0031] A scaffold model is established, comprising a cartilage repair layer and a subchondral bone repair layer. The cartilage repair layer includes a porous structure with a first pore size of 100-1000 μm; the subchondral bone repair layer includes a porous structure with a second pore size of 300-1000 μm; the cartilage repair layer and the subchondral bone repair layer are adjacent to each other and configured such that a pore structure with a third pore size of 50-300 μm is formed at their junction; wherein the first, second, and third pore sizes satisfy the following conditions: the third pore size is smaller than the first pore size, the third pore size is smaller than the second pore size, and the third pore size is sufficient to prevent blood vessels from invading the cartilage repair layer.

[0032] A printing paste for preparing a cartilage repair layer and a subchondral bone repair layer is provided, wherein the paste comprises ceramic powder, photosensitive resin, photoinitiator, light absorber, and dispersant;

[0033] A scaffold preform is formed by 3D printing using printing paste.

[0034] The scaffold preform is sintered after post-treatment.

[0035] In some embodiments of the present invention, the ceramic powder includes one or more of the following substances: hydroxyapatite, β-tricalcium phosphate, and bioactive glass.

[0036] In some embodiments of the present invention, the solid volume fraction in the printing paste is 40% to 58%.

[0037] In some embodiments of the present invention, the viscosity of the printing paste is 400–8580 mP·s.

[0038] In some embodiments of the present invention, the first aperture is 600-800 μm.

[0039] In some embodiments of the present invention, the second pore size is 400–600 μm.

[0040] In some embodiments of the present invention, the third aperture is 100–300 μm.

[0041] In some embodiments of the present invention, the osteocartilage scaffold is generally frustum-shaped, wherein the cartilage repair layer forms the upper part of the frustum and the subchondral bone repair layer forms the lower part of the frustum.

[0042] In some embodiments of the present invention, the taper of the frustum is 1:100 to 1:20.

[0043] The present invention has the following beneficial technical effects compared with the prior art:

[0044] This invention designs a porous structure for the cartilage repair layer and the subchondral bone repair layer, both made of the same material, and creates an interface with smaller pores at their junction through interlacing. This simulates the function of a calcified layer, ensuring that bone marrow blood carrying bioactive substances such as bone marrow mesenchymal stem cells and growth factors can penetrate to the cartilage defect site, while also preventing vascular invasion of the subchondral bone repair layer and thus preventing cartilage calcification. Furthermore, during the repair process, the subchondral bone repair layer provides sufficient support for the repair of the cartilage layer.

[0045] This invention further improves the performance of the osteocartilage scaffold with an interlaced structure by controlling the printing paste used to form the cartilage repair layer and the subchondral bone repair layer, thus preventing the scaffold from cracking at the junction and improving the mechanical properties, dimensional accuracy, and yield of the scaffold.

[0046] The present invention further designs the stent as a frustum-shaped structure, which is easier to implant than the traditional cylindrical stent. The stent can be stably fitted into the damaged site without the need for other fixation methods. Attached Figure Description

[0047] Figure 1 is a perspective view of a three-dimensional model of the osteochondral scaffold of Embodiment 1 of the present invention.

[0048] Figure 2 is a top view of Figure 1, showing the interface structure formed by the interlacing of the cartilage repair layer and the underlying bone repair layer.

[0049] Figure 3 is a three-dimensional view of the osteochondral scaffold model of Comparative Example 3.

[0050] Figure 4 is a top view of Figure 3.

[0051] Figure 5 is a scanning electron microscope image of the interface between the upper and lower layers of the osteocartilage scaffold in Embodiment 6 of the present invention.

[0052] Figure 6 shows the repair effect of the osteochondral double-layer scaffold of Example 6 and the single-layer scaffold of Comparative Example 3 on articular cartilage defects in New Zealand rabbits, with a control group.

[0053] Figure 7a is a stained tissue section of the osteochondral scaffold of Embodiment 6 of the present invention used for the repair of articular cartilage defects in New Zealand rabbits.

[0054] Figure 7b is a stained tissue section of the osteochondral scaffold used in Comparative Example 3 for repairing articular cartilage defects in New Zealand rabbits. Detailed Implementation

[0055] The present invention will be described in detail below with reference to specific embodiments. These specific embodiments are only used to illustrate the present invention and do not constitute any limitation on the scope of protection of the present invention.

[0056] In a specific embodiment of the present invention, the osteochondral repair scaffold comprises a two-layer structure: an upper layer repairing cartilage and a lower layer repairing subchondral bone. The upper cartilage repair layer is predominantly composed of vertical pores, consistent with the arrangement of chondrocytes. Furthermore, the cartilage repair layer can incorporate lateral pores to facilitate the migration of surrounding cartilage tissue cells to the defect site. The pore size of the porous structure in the cartilage repair layer is approximately 100-1000 μm, preferably 600-800 μm; the pore wall thickness is 100-300 μm, and the porosity is 50%-80%. This design ensures the mechanical strength of the scaffold while providing more space for cartilage regeneration, resulting in a faster degradation rate compared to the lower bone repair layer.

[0057] In a specific embodiment of the present invention, the porous structure of the lower bone repair layer has a pore size of approximately 300-1000 μm, preferably 400-600 μm. This pore size range is more suitable for bone repair, promotes osteogenic differentiation of stem cells, and simultaneously promotes bone tissue angiogenesis. The pore wall thickness of the lower bone repair layer is 200-400 μm, and the porosity is 40-60%. The mechanical properties of the lower bone repair layer are better than those of the cartilage repair layer, and its degradation rate is slower, thus providing sufficient support for the repair of the cartilage layer.

[0058] In a specific embodiment of the present invention, the shape of the pores in the porous structure of the cartilage repair layer and the underlying bone repair layer can be designed in various shapes, such as honeycomb, cross-shaped, round, square, etc. The junction of the cartilage repair layer and the underlying bone repair layer forms small pores with a diameter of 50-300μm by intersecting lines (pore walls), which can simulate the cartilage calcification layer. This ensures that the bone marrow blood carrying bioactive substances such as bone marrow mesenchymal stem cells and growth factors can penetrate into the cartilage defect site, while also preventing the invasion of the underlying blood vessels and preventing the cartilage layer from calcifying.

[0059] In a specific embodiment of the present invention, the scaffold is designed as a frustum, with a larger diameter at the upper end where the cartilage repair layer is located and a smaller diameter at the lower end where the lower bone repair area is located, with a taper of 1:100 to 1:20. During surgical procedures, it is difficult to maintain absolute perpendicularity between the drill hole and the cartilage surface. Even with only a small taper, the cylindrical scaffold may have difficulty fitting snugly against the wound, generating additional stress that could cause the scaffold to break. Compared to traditional cylindrical scaffolds, the frustum-shaped scaffold is easier to implant and less prone to breakage during the repair process, thus improving the repair outcome.

[0060] In a specific embodiment of the present invention, the pore walls of the cartilage repair layer and the underlying bone repair layer can be chamfered or rounded to reduce the stress between the layers and further improve the mechanical properties of the scaffold.

[0061] In a specific embodiment of the present invention, the bioceramic osteocartilage repair scaffold of the present invention is prepared using Digital Light Processing (DLP) 3D printing technology. The preparation method of the bioceramic osteocartilage scaffold based on photopolymerization 3D printing includes the following steps:

[0062] 1. Design the support model:

[0063] Digital 3D model design of osteocartilage scaffold: Digital 3D models of the osteocartilage scaffold are designed using 3D design software such as Solidworks, 3ds Max, Cinema 4D, Maya, Rhinoceros, or ZW3D. The models are converted to STL format and imported into slicing software such as Cura, Simplify3D, PrusaSlicer, 10dim, or Magics. The slice thickness is 25-100 μm, preferably 30-50 μm.

[0064] 2. Preparation of printing paste:

[0065] The bioceramic powder, photosensitive resin, photoinitiator, light absorber, and dispersant are mixed evenly and then ball-milled in a planetary ball mill for 2-8 hours to obtain a ceramic slurry. The bioceramic powder can be a commonly used bioceramic material in the art, including but not limited to one or more mixtures of hydroxyapatite, β-tricalcium phosphate, and bioactive glass. The photosensitive resin, photoinitiator, light absorber, and dispersant can be selected from commonly used photosensitive resins, photoinitiators, light absorbers, and dispersants in the art.

[0066] Due to the structural differences between the cartilage repair layer and the underlying bone repair layer, the osteocartilage scaffold of this invention is prone to cracking or pore blockage between the upper and lower layers after calcination. To further improve the mechanical properties of the scaffold and avoid cracking or pore blockage after calcination, this invention increases the solid content of the ceramic slurry, controlling the solid volume fraction of the slurry to 40%–58% (or controlling the weight percentage of the solid phase in the slurry to 65%–80%). Furthermore, this invention further regulates the viscosity of the slurry. High solid content typically leads to increased viscosity of the ceramic slurry, and excessively high viscosity can cause printing failures. This invention reduces the viscosity of the slurry by adding dispersants, including but not limited to: BYK110, BYK111, BYK-180, PX4310, KOS110, RD-9784, S18, oleic acid, KH560, sodium polyacrylate, etc. The dispersant accounts for 1% to 5% of the ceramic powder by mass, so that the viscosity of the slurry meets the printing requirements. In a specific embodiment of the present invention, the slurry viscosity is controlled between 400 and 8580 mP·s.

[0067] Furthermore, ceramic powder causes ultraviolet light scattering during the curing process, with high-solids-content slurries exhibiting more severe light scattering, easily leading to over-curing during printing. This invention can also effectively reduce light scattering and improve printing accuracy by adding light absorbers. Light absorbers include, but are not limited to, UV-327, UV-9, UV-531, and graphite. The light absorber constitutes 0.2% to 2% of the mass of the photosensitive resin.

[0068] 3. Printing of the support blank:

[0069] The ceramic slurry is poured into the material tank of the photopolymer 3D printer. The digitized model after slicing is imported into the execution software to start printing. The process parameters are adjusted and optimized to print and prepare the ceramic support blank.

[0070] 4. Post-processing of the bracket preform:

[0071] The uncured slurry adhering to the surface and internal channels of the stent is removed by ultrasonic cleaning with ethanol combined with spin drying. The cleaned stent is then subjected to UV curing for 2-10 minutes to improve the strength of the preform.

[0072] 5. Sintering of the support:

[0073] The cured scaffold was placed in a ceramic crucible and transferred to a muffle furnace for gradual sintering in air. The sintering procedure was as follows: the temperature was increased from room temperature to 200°C at a rate of 0.5-2°C / min, held for 1-2 hours to remove moisture from the scaffold blank; then increased from 200°C to 400°C at a rate of 0.2-1°C / min, held for 1-3 hours to remove hydrogen and oxygen components from the resin; then increased from 400°C to 600°C at a rate of 0.2-1°C / min, held for 1-3 hours to remove carbon from the resin; finally, the temperature was increased from 600°C to 1000-1200°C at a rate of 0.5-2°C / min, held for 2-4 hours to achieve a dense bioceramic sinter. The heating rate at each stage should be strictly controlled to prevent cracking of the scaffold due to rapid gas expulsion.

[0074] 6. Sterilization treatment:

[0075] The scaffolds prepared in step 5 were sterilized by gamma-ray irradiation after packaging.

[0076] The present invention will be further described below with reference to specific embodiments.

[0077] Example 1

[0078] A frustum-shaped double-layer scaffold was designed using Solidworks software. The 3D model of this scaffold is shown in Figure 1. The upper diameter of the scaffold containing the cartilage repair layer is 8 mm, and the lower diameter of the scaffold containing the subchondral bone repair layer is 7.7 mm. The scaffold height is 10 mm, with a corresponding taper of 3:100. The cartilage repair layer has honeycomb-like vertical pores with a diameter of 600–800 μm, while the subchondral bone repair layer has cross-shaped pores with a diameter of 400–600 μm. The pores of the upper and lower layers intersect at the interface, forming small pores of 100–300 μm, as shown in Figure 2. The pore wall thickness of the upper scaffold (i.e., the cartilage repair layer) is 0.15 mm, and the pore wall thickness of the lower scaffold (i.e., the subchondral bone repair layer) is 0.3 mm. The exported STL format file was imported into Magics slicing software, and after generating a TDP slicing file, it was imported into a 3D printer for printing.

[0079] Preparation of printing slurry: In a ball mill jar, weigh out 60g of photosensitive resin (composed of a blend of 50g of 1,6-hexanediol diacrylate, 50g of trimethylolpropane triacrylate, and 1g of trimethylbenzoyl-diphenylphosphine oxide), 120g of tricalcium β-phosphate powder, 4g of polymeric polyurethane dispersant, and 0.6g of graphite light absorber. After ball milling for 4 hours, pour the slurry into a brown reagent bottle and store it away from light to form a ceramic slurry. The viscosity of the ceramic slurry was tested using a rotational viscometer. In this slurry, the solid phase volume percentage was 40%, and the slurry viscosity was 410 mP·s.

[0080] The prepared slurry was poured into the material tank for 3D printing. The 3D printer was set to print with a layer thickness of 50μm, an exposure time of 3-15s, and a light source wavelength of 405nm.

[0081] After printing, the product was washed with anhydrous ethanol and dried for 24 hours to obtain the bracket blank.

[0082] The scaffold blank is placed in a box-type resistance furnace and sintered at 1150℃ for 3 hours to obtain a porous osteocartilage scaffold.

[0083] After packaging, the product is sterilized by gamma-ray irradiation.

[0084] After cooling, the appearance, dimensional accuracy, shrinkage rate, porosity and compressive strength of the support were characterized, and the results are shown in Table 1.

[0085] Example 2

[0086] The difference between Example 2 and Example 1 lies in the solid volume percentage and viscosity of the ceramic slurry.

[0087] In a ball mill jar, 55 g of photosensitive resin, 135 g of bioceramic powder, 4 g of dispersant, and 0.6 g of light absorber were weighed. After ball milling for 4 hours, the mixture was poured into a brown reagent bottle and stored away from light to form a ceramic slurry. The solid volume percentage of the slurry was 45%, and the viscosity was 553 mP·s.

[0088] The remaining preparation steps and parameters are the same as in Example 1. The appearance, dimensional accuracy, shrinkage rate, porosity, and compressive strength of the scaffold prepared in Example 2 were characterized, and the results are shown in Table 1.

[0089] Example 3

[0090] The difference between Example 3 and Example 1 lies in the solid volume percentage and viscosity of the ceramic slurry.

[0091] In a ball mill jar, 50 g of photosensitive resin, 150 g of bioceramic powder, 4 g of dispersant, and 0.6 g of light absorber were weighed. After ball milling for 4 hours, the mixture was poured into a brown reagent bottle and stored away from light to form a ceramic slurry. The solid volume percentage of the slurry was 50%, and the viscosity was 887 mP·s.

[0092] The remaining preparation steps and parameters are the same as in Example 1. The appearance, dimensional accuracy, shrinkage rate, porosity, and compressive strength of the scaffold prepared in Example 3 were characterized, and the results are shown in Table 1.

[0093] Example 4

[0094] The difference between Example 4 and Example 1 lies in the solid volume percentage and viscosity of the ceramic slurry.

[0095] In a ball mill jar, 45 g of photosensitive resin, 165 g of bioceramic powder, 4 g of dispersant, and 0.6 g of light absorber were weighed. After ball milling for 4 hours, the mixture was poured into a brown reagent bottle and stored away from light to form a ceramic slurry. The solid volume percentage of the slurry was 55%, and the viscosity was 2325 mP·s.

[0096] The remaining preparation steps and parameters are the same as in Example 1. The appearance, dimensional accuracy, shrinkage rate, porosity, and compressive strength of the scaffold prepared in Example 4 were characterized, and the results are shown in Table 1.

[0097] Example 5

[0098] The difference between Example 5 and Example 1 lies in the solid volume percentage and viscosity of the ceramic slurry.

[0099] In a ball mill jar, 40 g of photosensitive resin, 174 g of bioceramic powder, 4 g of dispersant, and 0.6 g of light absorber were weighed. After ball milling for 4 hours, the mixture was poured into a brown reagent bottle and stored away from light to form a ceramic slurry. The solid volume percentage of the slurry was 58%, and the viscosity was 8580 mP·s.

[0100] The remaining preparation steps and parameters are the same as in Example 1. The appearance, dimensional accuracy, shrinkage rate, porosity, and compressive strength of the scaffold prepared in Example 5 were characterized, and the results are shown in Table 1.

[0101] Comparative Example 1

[0102] The difference between Comparative Example 1 and Example 1 lies in the solid volume percentage and viscosity of the ceramic slurry.

[0103] In a ball mill jar, 40 g of photosensitive resin, 180 g of bioceramic powder, 4 g of dispersant, and 0.6 g of light absorber were weighed. After ball milling for 4 hours, the mixture was poured into a brown reagent bottle and stored away from light to form a ceramic slurry. The solid volume percentage of the slurry was 60%, and the viscosity was 15700 mP·s.

[0104] The remaining preparation steps and parameters were the same as in Example 1. The appearance, dimensional accuracy, shrinkage rate, porosity, and compressive strength of the scaffold prepared in Comparative Example 1 were characterized, and the results are shown in Table 1.

[0105] Comparative Example 2

[0106] The difference between Comparative Example 2 and Example 1 lies in the solid volume percentage and viscosity of the ceramic slurry.

[0107] In a ball mill jar, 65 g of photosensitive resin, 105 g of bioceramic powder, 4 g of dispersant, and 0.6 g of light absorber were weighed. After ball milling for 4 hours, the mixture was poured into a brown reagent bottle and stored away from light to form a ceramic slurry. The solid volume percentage of the slurry was 35%, and the viscosity was 332 mP·s.

[0108] The remaining preparation steps and parameters were the same as in Example 1. The appearance, dimensional accuracy, shrinkage rate, porosity, and compressive strength of the scaffold prepared in Comparative Example 2 were characterized, and the results are shown in Table 1.

[0109] Table 1. Performance characterization of osteocartilage scaffolds in Examples 1-5 and Comparative Examples 1-2

[0110] As can be seen from the characterization results of Examples 1-5 in Table 1, when the solid volume fraction of the printing paste is 40% to 58% and the paste viscosity is 400 to 8580 mP·s, the osteocartilage scaffold has an intact appearance, no obvious cracks, and no pore blockage. Furthermore, the dimensional accuracy and compressive strength can meet the requirements for use.

[0111] As can be seen from the characterization results of Comparative Example 2 in Table 1, when the solid volume fraction in the printing slurry is less than 40% and the slurry viscosity is less than 400 mP·s, obvious cracks appear at the connection between the upper and lower layers of the osteocartilage scaffold, and the dimensional accuracy and compressive strength are significantly worse, which cannot meet the usage requirements.

[0112] As can be seen from the characterization results of Comparative Example 1 in Table 1, when the solid volume fraction in the printing slurry is higher than 58% and the slurry viscosity is higher than 15700 mP·s, although the dimensional accuracy and compressive strength of the osteocartilage scaffold are significantly better, the high slurry viscosity increases the difficulty of 3D printing and cleaning, and the scaffold experiences pore blockage. Therefore, it cannot meet the usage requirements.

[0113] Example 6

[0114] The double-layer scaffold was designed using ZW3D software. Similar to the scaffold 3D models in Examples 1-5, this example also uses a frustum-shaped double-layer scaffold, but with reduced dimensions. The upper diameter of the scaffold containing the cartilage repair layer is 5mm, the lower diameter of the scaffold containing the lower bone repair layer is 4.8mm, the scaffold height is 5mm, and the corresponding taper is 1:25. The pore wall thickness of the upper scaffold is 0.15mm, the pore wall thickness of the lower scaffold is 0.3mm, and the porosity is 60.2%.

[0115] The upper cartilage repair layer has honeycomb-like vertical pores with a diameter of 600–800 μm, while the lower subchondral bone repair layer has cross-shaped pores with a diameter of 400–600 μm. The pores of the upper and lower layers intersect at the interface, forming small pores with a diameter of 100–300 μm. The exported STL format file is imported into 10dim slicing software to generate a TDP slicing file, which is then imported into a 3D printer for printing.

[0116] The ceramic slurry used in Example 6 was the same as that in Example 2. The ceramic slurry was poured into the feed tank of the photopolymer 3D printer, and a frustum-shaped support model was loaded. The 3D printer was set to print with a layer thickness of 25 μm, an exposure time of 5-20 seconds, and a light source wavelength of 405 nm.

[0117] After printing, the product was washed with anhydrous ethanol and dried for 24 hours to obtain the bracket blank.

[0118] The unfinished support blank was placed in a box-type resistance furnace and sintered at 1100℃ for 3 hours to obtain a porous ceramic support with a frustum-shaped double-layer structure. After sealing and packaging, the product was sterilized by gamma-ray irradiation.

[0119] The double-layer scaffold of Example 6 was observed by scanning electron microscopy (SEM), and the image is shown in Figure 5. As can be seen from the figure, the upper layer (cartilage repair layer) and the lower layer (lower bone repair layer) are intertwined. At the interface between the upper and lower layers, small pores of 100-300 μm are formed by the interlacing of the lines of the upper and lower layers. The pore diameter formed at the interface (i.e., the third pore diameter) is smaller than the pore diameter of the upper layer (i.e., the first pore diameter) and the pore diameter of the lower layer (i.e., the second pore diameter).

[0120] Comparative Example 3

[0121] Comparative Example 3 and Example 6 are identical in overall dimensions, printing paste, preform printing, sintering, and sterilization. The only difference is that Comparative Example 3 is a frustum-shaped single-layer support, as shown in Figure 3, with cross-shaped holes of 400–600 μm in diameter and 0.3 mm in wall thickness. A top view of this support model is shown in Figure 4. Because this comparative example is a single-layer support, it lacks the double-layer design of Example 6, making it impossible to form a staggered perforated structure at the junction of the two layers.

[0122] The sterilized double-layer scaffold of Example 6 and the single-layer scaffold of Comparative Example 3 were used in animal cartilage injury repair experiments to evaluate the effect of scaffold structure on cartilage injury repair.

[0123] Thirty-six New Zealand rabbits were used and divided into a control group, a single-layer scaffold group, and a double-layer scaffold group, with 12 rabbits in each group. Samples were collected at 6 and 12 weeks, with 6 rabbits at each time point. A full-thickness cartilage injury model was created by drilling a hole in the femoral trochlea of ​​the New Zealand rabbits using a 5 mm diameter drill bit. The wound diameter was 5 mm and the depth was 5 mm.

[0124] The double-layer scaffold of Example 6 and the single-layer scaffold of Comparative Example 3 were implanted into the aforementioned drilled sites, respectively. The control group received no scaffold implantation. Tissue samples were taken from rabbits in each group at 6 and 12 weeks post-surgery for morphological observation. The repair results of the damaged areas are shown in Figure 6. As can be seen from Figure 6, in the control group, the cartilage damage site was not repaired after 6 and 12 weeks, with only some fibrous tissue growing, indicating that a 5mm diameter cartilage injury in New Zealand rabbits cannot heal spontaneously. In the single-layer scaffold group, no repair was observed at 6 weeks, but the damaged area was filled at 12 weeks, although the surface was not smooth and showed a significant difference from the surrounding cartilage tissue, indicating that while the single-layer scaffold has some repair effect, it is not ideal. In the double-layer scaffold group, the damaged area was filled at 6 weeks and completely repaired at 12 weeks, with the repaired tissue integrating well with normal cartilage.

[0125] The mucosal portion in contact with the scaffold was removed and stained with hematoxylin and eosin (HE). The results are shown in Figures 7a and 7b. Figures 7a and 7b show that the joint section staining results of the double-layer and single-layer scaffold groups indicate that the cartilage repair surface in the double-layer scaffold group was smooth, and the newly formed cartilage was hyaline cartilage; while significant calcification was observed in the cartilage layer of the single-layer scaffold group.

[0126] Animal experiments have shown that the double-layer scaffold of the present invention has a significant effect on promoting cartilage damage repair and preventing cartilage layer calcification.

[0127] The present invention has been specifically described above with reference to specific embodiments. These specific embodiments are for illustrative purposes only and should not be construed as limiting the scope of protection of the present invention. Those skilled in the art can make various modifications, changes, or substitutions to the present invention without departing from its essence and scope. Therefore, various equivalent variations made in accordance with the present invention still fall within the scope of the present invention.

Claims

1. A photopolymerization 3D printed bioceramic osteocartilage scaffold, characterized in that: The osteocartilage scaffold comprises a cartilage repair layer and a subchondral bone repair layer formed of the same material, wherein... The cartilage repair layer includes a porous structure with a first pore size of 100-1000 μm. The subchondral bone repair layer includes a porous structure with a second pore size of 300-1000 μm. The cartilage repair layer and the subchondral bone repair layer are adjacent to each other and are constructed such that they interweave at the interface to form a porous structure with a third pore size of 50-300 μm. The first pore diameter, the second pore diameter, and the third pore diameter satisfy the following conditions: the third pore diameter is smaller than the first pore diameter, the third pore diameter is smaller than the second pore diameter, and the size of the third pore diameter is sufficient to prevent blood vessels from invading the cartilage repair layer.

2. The osteocartilage scaffold as described in claim 1, characterized in that: The first pore size is 600–800 μm.

3. The osteocartilage scaffold as described in claim 1, characterized in that: The second pore size is 400–600 μm.

4. The osteocartilage scaffold as described in claim 1, characterized in that: The third aperture is 100–300 μm.

5. The osteocartilage scaffold as described in claim 1, characterized in that: The porous structure of the cartilage repair layer has a pore wall thickness of 100-300 μm.

6. The osteocartilage scaffold as described in claim 5, characterized in that: The porous structure of the subchondral bone repair layer has a pore wall thickness of 200-400 μm.

7. The osteocartilage scaffold as described in claim 1, characterized in that: The osteocartilage scaffold is generally shaped like a frustum, with the cartilage repair layer forming the upper part of the frustum and the subchondral bone repair layer forming the lower part of the frustum.

8. The osteocartilage scaffold as described in claim 7, characterized in that: The taper of the frustum is 1:100 to 1:

20.

9. The osteocartilage scaffold as described in claim 1, characterized in that: The cartilage repair layer is mainly composed of vertical pores, which are arranged in accordance with the chondrocytes.

10. The osteocartilage scaffold as described in claim 9, characterized in that: The cartilage repair layer is also provided with side holes.

11. The osteocartilage scaffold as described in claim 1, characterized in that: The porosity of the cartilage repair layer is 50%-80%.

12. The osteocartilage scaffold as described in claim 1, characterized in that: The porosity of the subchondral bone repair layer is 40%-60%.

13. The osteocartilage scaffold as described in claim 1, characterized in that: The pore walls of the cartilage repair layer and the subchondral bone repair layer are rounded or chamfered.

14. The osteocartilage scaffold as described in claim 1, characterized in that: The photocurable 3D printing paste that forms the cartilage repair layer and the subchondral bone repair layer includes one or more of the following substances: hydroxyapatite, β-tricalcium phosphate, and bioactive glass.

15. The osteocartilage scaffold as described in claim 14, characterized in that: The solid volume fraction of the photocurable 3D printing slurry that forms the cartilage repair layer and the subchondral bone repair layer is 40% to 58%.

16. The osteocartilage scaffold as described in claim 15, characterized in that: The viscosity of the photocurable 3D printing slurry that forms the cartilage repair layer and the subchondral bone repair layer is 400–8580 mP·s.

17. A method for preparing a photopolymerized 3D printed bioceramic osteocartilage scaffold, characterized in that, The preparation method includes the following steps: A scaffold model is established, comprising a cartilage repair layer and a subchondral bone repair layer. The cartilage repair layer includes a porous structure with a first pore size of 100-1000 μm; the subchondral bone repair layer includes a porous structure with a second pore size of 300-1000 μm; the cartilage repair layer and the subchondral bone repair layer are adjacent to each other and configured such that a pore structure with a third pore size of 50-300 μm is formed at their junction; wherein the first, second, and third pore sizes satisfy the following conditions: the third pore size is smaller than the first pore size, the third pore size is smaller than the second pore size, and the third pore size is sufficient to prevent blood vessels from invading the cartilage repair layer. A printing paste for preparing a cartilage repair layer and a subchondral bone repair layer is provided, wherein the paste comprises ceramic powder, photosensitive resin, photoinitiator, light absorber, and dispersant; A scaffold preform is formed by 3D printing using printing paste. The scaffold preform is sintered after post-treatment.

18. The preparation method according to claim 17, characterized in that, The ceramic powder includes one or more of the following substances: hydroxyapatite, β-tricalcium phosphate, and bioactive glass.

19. The preparation method according to claim 18, characterized in that, The solid volume fraction in the printing paste is 40%–58%.

20. The preparation method according to claim 18 or 19, characterized in that, The viscosity of the printing paste is 400–8580 mP·s.

21. The preparation method according to claim 18, characterized in that, The first pore size is 600–800 μm.

22. The preparation method according to claim 18, characterized in that, The second pore size is 400–600 μm.

23. The preparation method according to claim 18, characterized in that, The third aperture is 100–300 μm.

24. The preparation method according to claim 18, characterized in that, The osteocartilage scaffold is generally shaped like a frustum, with the cartilage repair layer forming the upper part of the frustum and the subchondral bone repair layer forming the lower part of the frustum.

25. The preparation method according to claim 24, characterized in that, The taper of the frustum is 1:100 to 1:20.

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