3D printing knee joint cartilage repair stent integrated with drug sustained release function

Abstract

The invention provides a 3D printing knee joint cartilage repair scaffold integrated with a drug sustained release function, and belongs to the technical field of tissue engineering and intelligent biological materials. The stent is personalized and customized based on image data of a patient, and has gradient pore structures of a cartilage phase, a transition phase and a bone phase, a spiral interpenetrating nutrition channel, a partitioned microfluidic drug chamber and a mechanical response micro-column array. Through the pH / enzyme double-response plugging membrane, time-space accurate release of anti-inflammatory drugs, growth factors and antibiotics is realized, and pulse-type drug delivery is triggered under a joint activity load. The stent significantly promotes regeneration of transparent cartilage. The problems that an existing stent is single in structure, uncontrollable in drug release, insufficient in deep nutrition and disjunction in mechanics and biology are solved, the stent has excellent biocompatibility, mechanical stability and clinical convertibility, and an efficient and intelligent integrated regeneration solution is provided for knee joint cartilage injuries.

Description

Technical Field

[0001] This invention relates to the fields of biomedical engineering and tissue engineering, and more specifically, to a 3D-printed knee cartilage repair scaffold with integrated drug sustained-release function. Background Technology

[0002] Knee cartilage injury is a common challenge in sports medicine and orthopedics. Because articular cartilage lacks blood vessels, nerves, and lymphatic systems, its self-repair capacity is extremely limited. Once a full-thickness defect occurs, penetrating the subchondral bone, it often fails to heal, leading to chronic pain, joint dysfunction, and accelerating the development and progression of osteoarthritis. Currently, commonly used clinical treatments include microfracture surgery, autologous / allogeneic cartilage transplantation, matrix-induced autologous chondrocyte transplantation, MACC (Mandatory Collateralization Injection), and tissue-engineered scaffold implantation. Among these, tissue-engineered scaffolds are considered one of the most promising treatment strategies due to their customizability, biocompatibility, and potential regenerative guidance capabilities.

[0003] In recent years, researchers have developed a variety of porous scaffold materials for cartilage repair, such as collagen, hyaluronic acid, polylactic acid, PLA, polycaprolactone, PCL, gelatin methacrylamide, GelMA, and their complexes. To improve repair efficacy, some studies have attempted to load growth factors, such as TGF-β3 and BMP-2, or anti-inflammatory drugs, such as dexamethasone, into the scaffolds to regulate the local microenvironment and promote chondrocyte proliferation and matrix synthesis. Furthermore, the introduction of 3D printing technology has enabled precise control over the pore structure, mechanical properties, and shape matching of the scaffolds, further advancing the development of personalized cartilage repair.

[0004] However, existing technologies still have the following key shortcomings, which seriously restrict their clinical efficacy and application promotion: Most existing scaffolds employ a uniform porous structure, with pore size, porosity, and mechanical properties remaining spatially unchanged. This makes it difficult to reproduce the multi-scale gradient anatomical features of natural cartilage, from the dense, wear-resistant superficial zone to the deep, mineralized transition zone. This leads to: The deep layer lacks a microenvironment to guide osseointegration, and the cartilage-bone interface is weak, making it prone to displacement or detachment. The inability to simultaneously meet the different microenvironmental needs of chondrocytes and osteoblasts limits the overall repair of full-thickness defects.

[0005] Current drug-eluting stents generally employ simple physical embedding or blending methods, where drug release depends on material degradation or diffusion, which presents significant drawbacks. Significant burst release effect: A large amount of drug is rapidly released in the early stages of implantation, which not only causes waste but may also inhibit cell activity; Release kinetics are out of sync with biological processes: for example, anti-inflammatory drugs should be released at high concentrations in the early stages, while growth factors need to be continuously supplied after cell infiltration, but existing systems cannot achieve on-demand release; Lack of environmental responsiveness: It cannot sense physiological signals such as local pH, enzyme activity or mechanical stimulation, and thus cannot achieve intelligent feedback regulation.

[0006] Although porous structures facilitate cell migration, the channels of traditional scaffolds are mostly randomly distributed and not interconnected, which leads to: difficulty in effectively diffusing nutrients such as glucose and oxygen to the deeper layers of the scaffold; accumulation of metabolic waste, causing cell necrosis in the central region; and regeneration of tissue being limited to the surface of the scaffold, with voids or fibrous tissue forming in the deeper layers, affecting the quality of repair and mechanical integrity.

[0007] While most hydrogel scaffolds possess good bioactivity, they suffer from low mechanical strength and poor durability, making them prone to deformation or breakage under joint loads. High-strength polymer scaffolds, such as pure PCL, often lack sufficient bioactivity and have poor cell affinity. More importantly, existing scaffolds are all static systems, unable to convert the physiological and mechanical signals from patient rehabilitation training into biochemical signals that promote regeneration, thus missing the crucial mechanism of mechano-biochemical coupling in natural cartilage development.

[0008] Although 3D printing supports customized shapes, most research remains at the level of structural replication and does not integrate drug delivery, sensing or response functions. At the same time, existing solutions often require in vitro pre-culture of cells, such as MACC, which is complicated, costly and time-consuming, and faces obstacles such as immune rejection and regulatory approval, making it difficult to popularize in primary hospitals.

[0009] Current cartilage repair scaffolds still have systemic shortcomings in terms of structural biomimicry, intelligent drug release, nutrient delivery efficiency, biomechanical-biological synergy, and clinical applicability. Therefore, this paper proposes a 3D-printed knee cartilage repair scaffold with integrated drug sustained-release function. Summary of the Invention

[0010] The purpose of this invention is to address the problems raised in the existing background technology. To achieve the above-mentioned objective, this invention provides the following technical solution: a 3D-printed knee cartilage repair scaffold with integrated drug sustained-release function. The knee cartilage repair scaffold is a biomimetic biphase continuous gradient structure body constructed from biocompatible biodegradable composite materials through multi-material 3D printing. The body is divided into a cartilage phase layer, a transition phase layer, and a bone phase layer along the thickness direction from the articular surface to the subchondral bone. The cartilage phase layer and the bone phase layer are connected by a continuous spiral interpenetrating channel network to form a through-hole nutrient transport channel. The microfluidic partitioned drug loading chamber array is embedded in the main body. The chambers are partitioned according to spatial location and loaded with different functional drugs. The release sequence is controlled by a responsive occlusion membrane. A bioactive modification layer is set on the outer surface of the stent. The overall geometry of the stent is customized based on the patient's medical imaging data, with a matching error ≤0.2 mm.

[0011] As a preferred technical solution of the present invention, in the biomimetic dual-phase continuous gradient structure body, the porosity of the cartilage phase layer is... Satisfying 20%≤ ≤40%, porosity of bone layer Satisfying 65%≤ ≤85%, the porosity of the transition phase layer exhibits a nonlinear gradient change, satisfying the functional relationship: in For thickness coordinates, Total thickness ,index The gradient control parameter has a range of values. ; The continuous spiral interpenetrating channel network has a diameter of It consists of a spiral channel with a pitch of The channel wall thickness is Connectivity ≥ 95%.

[0012] As a preferred embodiment of the present invention, the microfluidic partitioned drug loading chamber array includes: The surface chamber, 0–1 mm deep, is filled with anti-inflammatory drugs, and the top of the chamber is covered with a pH-responsive hydrogel sealing membrane. The middle chamber, with a depth of 1–2.5 mm, is loaded with growth factors, and the sidewalls of the chamber are equipped with nanoporous valves cross-linked with MMP-13 enzyme-sensitive peptides. The deep chamber is >2.5 mm deep, loaded with antibiotics, and the bottom of the chamber is connected to the micropores of the bone layer, with release triggered by the degradation rate; Each chamber is independently sealed, with a volume of 0.1–1.0 μL and a spacing of 300–800 μm, arranged in a hexagonal honeycomb pattern.

[0013] As a preferred technical solution of the present invention, the pH-responsive hydrogel sealing membrane is copolymerized from 2-dimethylaminoethyl methacrylate (DMAEMA) and GelMA. When the local pH is ≤6.5 (inflammatory microenvironment), it undergoes protonation swelling, and the pore size expands to >50 nm, triggering drug release.

[0014] As a preferred embodiment of the present invention, it further includes a biodegradable mechanical-biochemical coupled micropillar array, wherein the micropillars are vertically distributed within the cartilage phase layer and have a height of [missing information]. , diameter is high modulus Made of composite material (elastic modulus ≥ 1.5 GPa), hollow inside and filled with drug-loaded hydrogel; When the stent is subjected to cyclic compressive loads (frequency 1 Hz, strain 10–15%), the micropillars elastically buckle, compressing the internal hydrogel and achieving pulsed drug release triggered by mechanical stimulation. The release amount per load is... satisfy: in For compressive strain, .

[0015] As a preferred technical solution of the present invention, the bone layer is embedded with radially arranged gradient mineralized microchannels. The inner wall of the channel is deposited sequentially from the inside to the outside with amorphous calcium phosphate (ACP), low-crystallinity hydroxyapatite (HA) and high-crystallinity HA, with the crystallinity increasing linearly from 0% to 70%, which promotes bone integration. The microchannels intersect with the spiral interpenetrating pore network to form a three-dimensional through-hole vascularized guiding path.

[0016] As a preferred embodiment of the present invention, the composite material comprises: and And by introducing Graphene oxide (GO) enhances thermal conductivity and cell-directed migration ability; the compressive modulus of the scaffold in a wet state... satisfy And in 10 6 Modulus retention ≥85% after multiple compression cycles (1 Hz, 10% strain).

[0017] As a preferred technical solution of the present invention, the microfluidic chamber and the helical interpenetrating channel network are integrally formed in the 3D printing process through a multi-nozzle collaborative deposition process: the first nozzle extrudes GelMA-based ink containing cells / drugs, the second nozzle simultaneously deposits molten PCL as structural support and chamber wall, and the third nozzle sprays photoinitiator atomized liquid to achieve in-situ cross-linking, with interlayer alignment accuracy ≤ ±20μm.

[0018] As a preferred embodiment of the present invention, the bioactive modified layer comprises a bifunctional coating: the bottom layer consists of covalent anchoring sites formed by treatment with a silane coupling agent (such as APTES), and the surface layer consists of a covalent complex of RGD peptide and hyaluronic acid (HA), with a molar ratio of... Surface charge density (pH=7.4) significantly promotes chondrocyte adhesion and anti-fibrosis.

[0019] As a preferred embodiment of the present invention, the scaffold can maintain a local TGF-β3 concentration of ≥10 ng / mL in the fourth week after implantation, while the shear strength at the interface between the newly formed tissue and the host cartilage is ≥0.3 MPa; in vitro dynamic compression experiments show that the drug release rate under loading conditions is 2–4 times higher than that under static conditions, confirming the effectiveness of the mechanical-biochemical coupling release mechanism.

[0020] Compared with the prior art, the beneficial effects of the present invention are as follows: The scaffold of this invention adopts a continuous gradient structure in three zones: cartilage phase, transition phase, and bone phase, accurately simulating the anatomical and mechanical properties of natural cartilage from the surface dense collagen to the deep calcified cartilage and subchondral bone. Combined with radial gradient mineralization microchannels, it simultaneously promotes hyaline cartilage formation and osseointegration, effectively solving the clinical problems of cartilage failure, bone failure, and easy interface delamination in the repair of full-thickness cartilage defects. Animal experiments show that the shear strength of the interface between the newly formed tissue and the host cartilage reaches 0.34±0.04 MPa at 12 weeks after surgery, which is significantly higher than that of traditional scaffolds and close to the natural cartilage-bone integration strength.

[0021] This invention achieves precise spatiotemporal, on-demand intelligent drug delivery: a zoned microfluidic chamber environment-responsive sealing membrane; a surface pH-responsive membrane rapidly releases anti-inflammatory drugs during the inflammatory phase (pH ≤ 6.5), inhibiting early fibrosis; a middle layer MMP-13 enzyme-sensitive valve releases growth factors during cell infiltration, promoting matrix synthesis; and a deep layer provides sustained-release antibiotics to prevent deep infections. A mechanically triggered micropillar array: under the physiological load generated by rehabilitation training, pulsed release of TGF-β3 is achieved, with a dynamic release rate 54.5% higher than under static conditions, significantly enhancing the efficiency of functional matrix deposition.

[0022] This invention significantly improves cell survival and tissue homogeneity within the scaffold: a continuous spiral interpenetrating pore network with a connectivity rate of ≥96% constructs a three-dimensional through-hole nutrient transport channel, breaking through the bottleneck of external survival and internal death caused by diffusion limitations in traditional scaffolds. This invention possesses excellent mechanical adaptability and long-term service stability: the wet compressive modulus is 1.35±0.12MPa, within the ideal range for natural cartilage, and 0.5 and 2.0 MPa, avoiding stress shielding or excessive wear; after 10 6 After multiple cycles of compression, simulating one year of daily activities, the modulus retention rate is ≥87%, which is far superior to the traditional hydrogel scaffold (<65%), ensuring the structural integrity in the early stages of repair. The surface RGD-hyaluronic acid dual-function coating has both adhesion-promoting and anti-fibrotic effects, reducing scar tissue invasion and maintaining joint surface smoothness.

[0023] This invention supports personalized precision medicine and shortens the rehabilitation cycle: it is customized based on the patient's MRI / CT data, with a shape matching error of ≤0.2 mm; The intelligent release mechanism and mechanical response design enable the scaffold to actively adapt to the individual's rehabilitation process without the need for secondary surgery or external intervention. Animal models show that hyaline cartilage-like tissue appears as early as 8 weeks after surgery, and the repair quality is close to normal at 12 weeks. The MRI T2 value is 38.2 ms, compared to the normal 35 and 40 ms, which is expected to significantly shorten the clinical rehabilitation time.

[0024] The GelMA, PCL, nHA, and GO used in this invention are all FDA / CE certified or widely studied biomaterials, and their degradation products are non-toxic and metabolizable. The invention employs mature multi-nozzle extrusion 3D printing technology, which is compatible with existing biomanufacturing platforms and has the feasibility for large-scale production. This invention not only achieves several original breakthroughs in structure and function, but also demonstrates significant advantages in repair effect, safety, intelligence and clinical applicability. It provides an efficient, reliable and scalable regenerative medicine solution for knee cartilage damage, and has important scientific value and broad industrialization prospects. Attached Figure Description

[0025] Figure 1 This is a schematic diagram of the structure provided by the present invention; Figure 2 This is a schematic diagram of the structure provided by the present invention; Figure 3 A block diagram of the gradient porous structure parameters of the support provided by the present invention; Figure 4 This is a block diagram of 3D printing material parameters provided by the present invention; Figure 5 This is a flowchart of drug loading data provided by the present invention. Detailed Implementation

[0026] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention.

[0027] Therefore, the following detailed description of the embodiments of the present invention is not intended to limit the scope of the claimed invention, but merely illustrates some embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention. It should be noted that, in the absence of conflict, the embodiments and features and technical solutions in the embodiments of the present invention can be combined with each other. It should be noted that similar reference numerals and letters in the following figures indicate similar items; therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures.

[0028] Example 1: A 3D-printed knee cartilage repair scaffold with integrated drug sustained release function, which is a biomimetic dual-phase continuous gradient structure body constructed by multi-material 3D printing of biocompatible biodegradable composite material. The body is divided into cartilage phase layer 1, transition phase layer 2 and bone phase layer 3 along the thickness direction from the articular surface to the subchondral bone. The cartilage phase layer 1 and bone phase layer 3 are connected by a continuous spiral interpenetrating channel network 4 to form a through nutrient transport channel. The cartilage phase layer 1 has a thickness of 0.8–1.5 mm, a porosity of 70%–85%, and an average pore size of 150–300 μm; the bone phase layer 3 has a thickness of 1.2–2.0 mm, a porosity of 50%–65%, and an average pore size of 300–500 μm; the transition phase layer 2 has a thickness of 0.5–1.0 mm, and its porosity and pore size exhibit a linear gradient along the thickness direction, satisfying: in, and These represent the depth positions of transition phase layer 2. Porosity and average pore size at the location; The porosity and pore size at the end of cartilage phase layer 1; The porosity and pore size at the starting end of bone phase layer 3; This represents the total thickness of the cartilage phase layer 1; The thickness of the transition phase layer 2; ; The helix angle θ of the continuous helical interpenetrating channel network 4 satisfies The diameter of the channel is The channel spacing is Channel connectivity ; The microfluidic partitioned drug loading chamber array is embedded in the main body. The chambers are partitioned according to spatial location and loaded with different functional drugs. The release sequence is controlled by a responsive blocking membrane. The chamber array contains at least three functional zones: a surface chamber loaded with an anti-inflammatory drug, dexamethasone, and a concentration... The middle chamber is loaded with chondrogenic growth factor (TGF-β3) at a concentration of 10–100 ng / mL, and the deep chamber is loaded with osteointegrative factor (BMP-2) at a concentration of 50–200 ng / mL; the volume of each chamber is [missing information]. The spacing is ; The responsive blocking membrane is composed of a pH / enzyme dual-responsive hydrogel, and its drug release kinetics conform to the modified Korsmeyer-Peppas model. in, Let be the cumulative release fraction at time t, k be the release rate constant, and n be the release exponent; in the inflammatory microenvironment To achieve pulsed or accelerated release; in physiological environments Maintaining zero-order or near-zero-order sustained release; A bioactive modification layer disposed on the outer surface of the scaffold; The bioactive modified layer has a thickness of RGD peptide or hyaluronic acid grafted layers, with a grafting density of 0.5–2.0 pmol / cm². 2 Increased cell adhesion rate by ≥40% (compared to unmodified surface); The overall geometry of the stent is customized based on the patient's medical imaging data, with a matching error of ≤0.2 mm; The compressive modulus of the support exhibits a gradient distribution along the thickness direction, satisfying: ,in (Cartilage phase 1), (Bone layer 3), H is the total thickness of the scaffold. This ensures that the mechanical properties match the natural cartilage-bone interface; the scaffold withstands physiological loads. Next cycle 10 6 Subsequent deformation recovery rate ≥90%.

[0029] In the biomimetic two-phase continuous gradient structure, the porosity of the cartilage phase layer 1 is... Satisfying 20%≤ ≤40%, porosity of bone layer 3 Satisfying 65%≤ ≤85%, the porosity of the transition phase layer 2 exhibits a nonlinear gradient change, satisfying the functional relationship: in For thickness coordinates, Total thickness ,index The gradient control parameter has a range of values. ; Continuous helical interpenetrating channel network 4 consists of a diameter of It consists of a spiral channel with a pitch of The channel wall thickness is Connectivity ≥ 95%.

[0030] The microfluidic partitioned drug loading chamber array includes: The surface chamber, 0–1 mm deep, is filled with anti-inflammatory drugs, and the top of the chamber is covered with a pH-responsive hydrogel sealing membrane. The middle chamber, with a depth of 1–2.5 mm, is loaded with growth factors, and the sidewalls of the chamber are equipped with nanoporous valves cross-linked with MMP-13 enzyme-sensitive peptides. The deep chamber is >2.5 mm deep and is loaded with antibiotics. The bottom of the chamber is connected to the bone layer through 3 micropores, and the release is triggered by the degradation rate. Each chamber is independently sealed, with a volume of 0.1–1.0 μL and a spacing of 300–800 μm, arranged in a hexagonal honeycomb pattern.

[0031] The pH-responsive hydrogel sealing membrane is copolymerized from 2-dimethylaminoethyl methacrylate (DMAEMA) and GelMA. When the local pH is ≤6.5 (inflammatory microenvironment), it undergoes protonation swelling, expanding the pore size to >50 nm and triggering drug release.

[0032] It also includes a biodegradable mechanical-biochemical coupled micropillar array, with the micropillars vertically distributed within the cartilage phase layer 1, at a height of [missing information]. , diameter is high modulus Made of composite material (elastic modulus ≥ 1.5 GPa), hollow inside and filled with drug-loaded hydrogel; When the stent is subjected to cyclic compressive loads (frequency 1 Hz, strain 10–15%), the micropillars elastically buckle, compressing the internal hydrogel and achieving pulsed drug release triggered by mechanical stimulation. The release amount per load is... satisfy: in For compressive strain, .

[0033] The bone layer 3 contains radially arranged gradient mineralized microchannels. The inner walls of the channels are deposited sequentially from the inside out with amorphous calcium phosphate (ACP), low-crystallinity hydroxyapatite (HA), and high-crystallinity HA. The crystallinity increases linearly from 0% to 70%, promoting bone integration. The microchannels intersect with the spiral interpenetrating pore network 4 to form a three-dimensional vascularized guiding pathway.

[0034] Composite materials include: and And by introducing Graphene oxide (GO) enhances thermal conductivity and cell-directed migration ability; the compressive modulus of the scaffold in a wet state... satisfy And in 10 6 Modulus retention ≥85% after multiple compression cycles (1 Hz, 10% strain).

[0035] The microfluidic chamber and the helical interpenetrating channel network 4 are integrally formed in the 3D printing process through a multi-nozzle collaborative deposition process: the first nozzle extrudes GelMA-based ink containing cells / drugs, the second nozzle simultaneously deposits molten PCL as structural support and chamber wall, and the third nozzle sprays photoinitiator atomized liquid to achieve in-situ cross-linking, with interlayer alignment accuracy ≤ ±20μm.

[0036] The bioactive modification layer comprises a bifunctional coating: the bottom layer consists of covalent anchoring sites formed by treatment with a silane coupling agent (such as APTES), and the top layer is a covalent complex of RGD peptide and hyaluronic acid (HA), with a molar ratio of... Surface charge density (pH=7.4) significantly promotes chondrocyte adhesion and anti-fibrosis.

[0037] The scaffold maintained a local TGF-β3 concentration ≥10 ng / mL at week 4 post-implantation, while the shear strength at the interface between the newly formed tissue and the host cartilage was ≥0.3 MPa. In vitro dynamic compression experiments showed that the drug release rate under loading conditions was 2–4 times higher than that under static conditions, confirming the effectiveness of the mechanical-biochemical coupling release mechanism.

[0038] The working principle of a 3D-printed knee cartilage repair scaffold integrating drug sustained-release function is based on three core concepts: biomimetic structure, intelligent response release mechanism, and mechanical-biochemical coupling regulation. Through the synergistic effect of multi-scale structures and functional units, it dynamically adapts to the biological time sequence requirements of knee cartilage damage repair after implantation, achieving precise intervention throughout the entire process from inflammation suppression, cell recruitment, matrix synthesis to tissue integration. The specific principle is as follows: A biomimetic gradient structure provides physical support and microenvironment guidance: The scaffold uses multi-material 3D printing technology to construct a continuous gradient structure in three zones: cartilage phase, transition phase, and bone phase, accurately simulating the zonal characteristics of natural knee cartilage from the surface dense collagen network to the deep calcified cartilage and subchondral bone. Cartilage phase 1 (surface): low porosity (20–40%), small pore size (100–200 μm), providing a smooth and wear-resistant surface to resist joint friction; Transitional phase 2 (middle layer): moderate porosity (40–60%), supporting chondrocyte migration and type II collagen deposition; Bone phase layer 3 (deep): High porosity (65–85%) and contains radially gradient mineralized microchannels that promote vascular ingrowth and bone integration.

[0039] Meanwhile, the continuous spiral interpenetrating pore network 4 (diameter 150–300 μm) spanning three layers forms a three-dimensional through-hole nutrient / metabolite transport channel, solving the problem of cell necrosis due to limited diffusion inside traditional scaffolds, and significantly improving the depth and uniformity of tissue regeneration.

[0040] Microfluidic partitioned chambers enable precise spatiotemporal drug delivery: The stent integrates a microfluidic partitioned drug loading chamber array, pre-loaded with different functional drugs according to spatial location, and the release sequence is controlled by an environmentally responsive occlusion structure: Surface chamber: loaded with dexamethasone, topped with a pH-responsive hydrogel membrane. Postoperative local inflammation causes the microenvironment pH to drop to ≤6.5, triggering membrane swelling and rupture, rapidly releasing anti-inflammatory drugs (1–7 days), inhibiting macrophage activation and fibrosis; The middle chamber is loaded with TGF-β3 and has MMP-13 enzyme-sensitive peptide cross-linked nanopore valves on its sidewalls. As chondrocytes infiltrate and secrete matrix metalloproteinases (MMP-13), the pore valves degrade, continuously releasing growth factors (7–28 days) and promoting the synthesis of cartilage-specific matrix (such as type II collagen and proteoglycans). Deep chambers: Loaded with vancomycin, which is slowly released through PCL / nHA matrix degradation (>14 days) to prevent deep infections.

[0041] 3. Mechano-biochemical coupled micropillar array enables on-demand pulsed release: A biodegradable, mechanically responsive micropillar array is embedded within the scaffold cartilage phase layer 1. High-modulus PCL / nHA hollow micropillars are filled with drug-eluting hydrogel. Under the cyclic compressive load (frequency ≈ 1 Hz, strain 10–15%) generated by daily knee joint activities: the micropillars undergo controllable elastic flexion, compressing the internal hydrogel; The drug is triggered to be released in a pulse, and the release amount is positively correlated with the loading intensity (ΔM∝ε^m); this achieves an intelligent feedback mechanism that administers the drug more when there is more activity, which is especially suitable for the peak demand for growth factors during rehabilitation training.

[0042] 4. Surface functionalization and material degradation synergistically promote tissue integration The scaffold surface is modified with an RGD-hyaluronic acid bifunctional coating. RGD promotes chondrocyte adhesion, while hyaluronic acid provides lubrication and inhibits fibroblast invasion, reducing scar formation. The degradation rate of the composite material (GelMA / PCL / nHA / GO) is synchronized with the formation of new tissue: GelMA hydrolyzes within 4–6 weeks, PCL degrades gradually within 6–12 months, and nHA provides early mechanical support and induces mineralization. Gradient-crystallized hydroxyapatite microchannels in bone phase layer 3 guide host bone tissue to grow in a directional manner along the channels, achieving seamless biomechanical integration of the cartilage-bone interface.

[0043] After implantation, the scaffold works in a dynamic synergy with the above-mentioned structural and functional units: early stage (1–7 days): rapid anti-inflammatory and antibacterial action to create a favorable regenerative microenvironment; mid-stage (7–28 days): continuous promotion of cartilage regeneration and enhanced drug delivery through mechanical stimulation to accelerate the deposition of functional matrix; late stage (>28 days): the scaffold gradually degrades, the newly formed cartilage fuses with the host tissue, and the integrity and mechanical properties of the articular surface are restored.

[0044] The working process of a 3D-printed knee cartilage repair scaffold integrating drug sustained-release function can be divided into three stages: preoperative customization, intraoperative implantation, and postoperative dynamic repair. These stages are closely linked, forming a closed-loop personalized treatment process. Details are as follows: Preoperative customization stage: Medical imaging acquisition: High-resolution MRI or CT scans are performed on the patient's knee joint to obtain three-dimensional anatomical data of the cartilage defect area, including the location, depth, area and morphology of the surrounding cartilage / bone tissue.

[0045] Digital model reconstruction and scaffold structure: The three-dimensional model of the defect area is reconstructed using medical image processing software (such as Mimics); the scaffold model with gradient pore structure, spiral interpenetrating channel network 4, microfluidic drug chamber array and mechanically responsive micropillars is constructed using CAD system to ensure that the shape and defect contour matching error is ≤0.2 mm.

[0046] Multi-material bio-ink formulation: Formulate GelMA / PCL / nHA / GO composite bio-ink (GelMA 10 wt%, PCL 15 wt%, nHA 3 wt%, GO 1 wt%). Preparation of drug-loaded microspheres: Dexamethasone (Dex), TGF-β3 and vancomycin (Van) were encapsulated using a double emulsion method, with particle size controlled at 20–50 μm and encapsulation efficiency ≥85%; Different drug microspheres are premixed into the ink of the corresponding layer according to their functional zones, or individually loaded into the microfluidic printing channel.

[0047] Multi-nozzle 3D printing and post-processing: A multi-material extrusion bioprinter is used to simultaneously deposit structural materials (PCL / nHA) and functional materials (GelMA + drug) to construct partitioned chambers and gradient channels; after printing, it is cross-linked by ultraviolet light (365nm, 10 mW / cm). 2 Cured at 120 s, and coated with RGD-hyaluronic acid dual-function coating, then freeze-dried and sterilized for later use.

[0048] Intraoperative implantation stage: Debridement and defect preparation: The knee joint is exposed during surgery, and necrotic tissue and fibrous scars in the cartilage damage area are thoroughly removed. The defect edges are trimmed to a regular geometric shape to ensure that the scaffold can fit tightly.

[0049] Precise stent implantation: The customized stent is aseptically removed and accurately placed into the defect cavity along the cartilage-bone interface, with bone layer 3 facing the subchondral bone and cartilage layer 1 facing the joint cavity; if necessary, bioabsorbable sutures or fibrin glue are used for fixation to ensure initial stability.

[0050] Intraoperative verification of compatibility: Intraoperative navigation or fluorescent labeling confirms that the stent fits the host tissue seamlessly, without any obvious gaps or protrusions.

[0051] Postoperative dynamic repair phase (time series is key) Days 1–7: Inflammation Suppression and Infection Control Period The local tissues develop an inflammatory response due to surgical trauma, and the pH value drops to ≤6.5; The pH-responsive sealing membrane in the surface microfluidic chamber swells and ruptures, rapidly releasing dexamethasone (accounting for 40–60% of the total drug load), inhibiting the NF-κB pathway, and reducing pro-inflammatory factors such as IL-1β and TNF-α; Vancomycin is released simultaneously into deep chambers to maintain a local concentration above the MIC and prevent postoperative infection. Chondrocytes begin to migrate from the defect edge to the surface of the scaffold.

[0052] Days 7–28: Peak period of cartilage regeneration and matrix synthesis Infiltrating chondrocytes secrete MMP-13 enzyme, which degrades the enzyme-sensitive peptide pore valves in the middle chamber. TGF-β3 is continuously released (accounting for 50–70% of the total drug load), activating the Smad2 / 3 signaling pathway and promoting the synthesis of large amounts of type II collagen (COL2A1) and proteoglycans. The patient begins rehabilitation training, with the joint subjected to cyclic compressive loads (≈1 Hz, 10–15% strain). Mechanically responsive micropillar arrays buckle under pressure, pulse-like extrusion of internal growth factors, achieving "activity-enhanced drug delivery" and significantly improving matrix deposition efficiency; The helical interpenetrating pore network 4 ensures the transport of nutrients (glucose, oxygen) to deeper layers, supporting cell survival.

[0053] Days 28–84: Tissue maturation and scaffold degradation and integration period The GelMA matrix undergoes gradual hydrolysis (weeks 4–6), and the PCL backbone slowly degrades (6–12 months). The degradation products are non-toxic and metabolizable. Newly formed cartilage tissue gradually fills the scaffold pores, and the type II collagen network becomes denser; The bone phase layer 3 gradient mineralization microchannels guide the ingrowth of host bone tissue, forming a cartilage-bone transition zone (tidemark-like structure). The mechanical properties of the scaffold evolved in sync with the newly formed tissue, with the compressive modulus gradually decreasing from an initial 1.2 MPa to approximately 0.8 MPa, which is comparable to that of natural cartilage. At week 12, the shear strength at the interface between the newly formed tissue and the host cartilage was ≥0.3 MPa, and the articular surface returned to smooth continuity.

[0054] After a dynamic repair process of about 3 months, the scaffold completed its mission of temporary support and intelligent regulation and was completely replaced by functional hyaline cartilage tissue. The patient's knee pain was relieved and range of motion was restored. MRI showed that the signal of the defect area was close to that of normal cartilage, achieving dual regeneration of anatomical structure and biological function.

[0055] Experimental Example 1: Methods: The three-dimensional pore structure of the scaffold was reconstructed by Micro-CT scanning (5 μm resolution); the surface morphology and micropillar array were observed by SEM; the wet compressive modulus (n=6) was tested by a universal testing machine; and the hydrophilicity was determined by a contact angle meter.

[0056] Control group: Traditional uniform pore GelMA / PCL scaffold (no gradient, no microfluidic chamber, no microcolumn).

[0057] Experimental Example 2: Drug Release Kinetics Test Methods: The drug-loaded scaffold was immersed in PBS (pH=7.4) or simulated inflammatory fluid (pH=6.0) at 37℃, and samples were taken at regular intervals. The concentration of TGF-β3 was detected by ELISA, and the contents of dexamethasone and vancomycin were detected by HPLC. The dynamic loading group was subjected to cyclic compression at 1 Hz and 10% strain.

[0058] Grouping: Group A: Static release (pH=7.4); Group B: Static release (pH=6.0); Group C: Dynamic loading and release (pH=7.4 + compression).

[0059] Experimental Example 3: In vitro cell compatibility and functional evaluation Methods: Human primary chondrocytes were seeded on the surface of a scaffold, and the proliferation rate was measured on days 1, 3, and 7 using the CCK-8 assay; the expression of COL2A1, Aggrecan, and SOX9 genes on day 7 was detected by qPCR; and type II collagen deposition was observed by immunofluorescence staining.

[0060] Control group: blank GelMA / PCL stent.

[0061] Experiment 4: Repair Experiment of Full-Thickness Cartilage Defects in Rabbit Knee Joint Animal model: New Zealand white rabbits (n=24) were used to establish a full-thickness cartilage defect of the femoral condyle with a diameter of 4 mm and a depth of 2 mm.

[0062] Grouping (8 animals per group): Experimental group: implanted with the stent of this invention; Control group 1: Implantation of traditional uniform pore scaffolds; Control group 2: Blank defect (no material implanted).

[0063] Observation time points: 4 weeks, 8 weeks and 12 weeks after surgery.

[0064] Evaluation indicators: MRI (T2 mapping) is used to assess the quality of cartilage repair. Histological (HE, Safranin O / Fast Green staining) score (ICRS II criteria); Biomechanical testing: interfacial shear strength; Immunohistochemistry: expression of type II collagen and MMP-13.

[0065] Test data Table 1: Comparison of physicochemical properties of stents (n=6, mean ± SD)

[0066] Table 2: Cumulative drug release rate (Day 7 / Day 28)

[0067] Note: In group B, the release of TGF-β3 was significantly accelerated on day 7 (p<0.01), and the release of TGF-β3 in group C was 54.5% higher than that in group A (p<0.001).

[0068] Table 3: Results of in vitro cell experiments (Day 7)

[0069] Table 4: Model-free histological scores (ICRSII, maximum score 12 points)

[0070] The experimental group had a significantly higher score at 12 weeks than the other two groups (p<0.001).

[0071] Table 5: Interfacial shear intensity and MRI T2 value at 12 weeks

[0072] The normal T2 value of rabbit cartilage is approximately 35–40 ms, while the experimental group is close to the normal level.

[0073] III. Experimental Analysis Significant structural advantages: Micro-CT and SEM confirmed that the scaffold of this invention successfully constructed a complex structure of gradient pores + helical interpenetrating channels + microcolumn array, with a channel connectivity rate of up to 96%, which is far superior to the traditional scaffold (72.5%), providing a physical basis for cell infiltration and nutrient transport.

[0074] The smart release mechanism is effective: Dexamethasone release was accelerated at pH 6.0, verifying inflammatory response; Dynamic loading significantly increased the release of TGF-β3, confirming the feasibility of the mechanical-biochemical coupling release mechanism. Vancomycin provides sustained release for more than 28 days, meeting the clinical requirements for anti-infection cycles.

[0075] Promotes functional cartilage regeneration: In vitro experiments showed that the scaffold of the present invention significantly enhanced chondrocyte proliferation and expression of specific matrix genes; in vivo experiments showed that at 12 weeks, the newly formed tissue exhibited hyaline cartilage characteristics (strongly positive for Safranin O and abundant type II collagen) and was tightly integrated with the host tissue (shear strength 0.34 MPa).

[0076] Mechanical properties match physiological needs: The initial modulus of the scaffold (1.35 MPa) is close to that of natural cartilage (0.5–2.0 MPa), and after 10... 6 After multiple compression cycles, the retention rate is >87%, indicating long-term service capability.

[0077] IV. Conclusion The stent of this invention, through innovative designs such as biomimetic gradient structure, microfluidic partitioned drug loading, and mechanically responsive micropillars, successfully achieves intelligent drug delivery integrating spatial positioning, time programming, and mechanical triggering. In a rabbit knee joint full-thickness cartilage defect model, the scaffold significantly promoted the regeneration of high-quality hyaline cartilage, and the repair effect after 12 weeks was close to that of normal cartilage, which was significantly better than the traditional scaffold. The stent possesses excellent mechanical stability, biocompatibility, and degradation compatibility, making it safe, effective, and with potential for clinical translation.

[0078] The above embodiments are only used to illustrate the present invention and are not intended to limit the technical solutions described herein. Although the present invention has been described in detail with reference to the above embodiments, the present invention is not limited to the specific embodiments described above. Therefore, any modifications or equivalent substitutions to the present invention, as well as all technical solutions and improvements that do not depart from the spirit and scope of the invention, are covered within the scope of the claims of the present invention.

Claims

1. A 3D-printed knee cartilage repair scaffold integrating drug sustained-release function, characterized in that, The knee joint cartilage repair scaffold is a biomimetic dual-phase continuous gradient structure constructed by multi-material 3D printing of biocompatible biodegradable composite material. The main body is divided into a cartilage phase layer (1), a transition phase layer (2) and a bone phase layer (3) along the thickness direction from the articular surface to the subchondral bone. The cartilage phase layer (1) and the bone phase layer (3) are connected by a continuous spiral interpenetrating channel network (4) to form a through nutrient transport channel. The microfluidic partitioned drug loading chamber array is embedded in the main body. The chambers are partitioned according to spatial location and loaded with different functional drugs. The release sequence is controlled by a responsive occlusion membrane. A bioactive modification layer is set on the outer surface of the stent. The overall geometry of the stent is customized based on the patient's medical imaging data, with a matching error ≤0.2 mm.

2. The 3D-printed knee cartilage repair scaffold with integrated drug sustained-release function according to claim 1, characterized in that, In the biomimetic biphase continuous gradient structure, the porosity of the cartilage phase layer (1) is... Satisfying 20%≤ ≤40%, porosity of bone layer (3) Satisfying 65%≤ ≤85%, the porosity of the transition phase layer (2) exhibits a nonlinear gradient change, satisfying the functional relationship: in For thickness coordinates, Total thickness ,index The gradient control parameter has a range of values. ; The continuous spiral interpenetrating channel network (4) consists of a diameter of It consists of a spiral channel with a pitch of The channel wall thickness is Connectivity ≥ 95%.

3. The 3D-printed knee cartilage repair scaffold with integrated drug sustained-release function according to claim 1, characterized in that, The microfluidic partitioned drug loading chamber array includes: The surface chamber, 0–1 mm deep, is filled with anti-inflammatory drugs, and the top of the chamber is covered with a pH-responsive hydrogel sealing membrane. The middle chamber, with a depth of 1–2.5 mm, is loaded with growth factors, and the sidewalls of the chamber are equipped with nanoporous valves cross-linked with MMP-13 enzyme-sensitive peptides. The deep chamber is >2.5 mm deep and is loaded with antibiotics. The bottom of the chamber is connected to the micropores of the bone layer (3), and release is triggered by the degradation rate. Each chamber is independently sealed, with a volume of 0.1–1.0 μL and a spacing of 300–800 μm, arranged in a hexagonal honeycomb pattern.

4. The 3D-printed knee cartilage repair scaffold with integrated drug sustained-release function according to claim 3, characterized in that, The pH-responsive hydrogel sealing membrane is copolymerized from 2-dimethylaminoethyl methacrylate (DMAEMA) and GelMA. When the local pH is ≤6.5 and the inflammatory microenvironment is present, protonation swelling occurs, and the pore size expands to >50 nm, triggering drug release.

5. The 3D-printed knee cartilage repair scaffold with integrated drug sustained-release function according to claim 1, characterized in that, It also includes a biodegradable mechanical-biochemical coupled micropillar array, wherein the micropillars are vertically distributed within the cartilage phase layer (1) and have a height of , diameter is high modulus Made of composite material, hollow inside and filled with drug-loaded hydrogel; When the stent is subjected to cyclic compressive loads, the micropillars elastically buckle, compressing the internal hydrogel and triggering a pulsed drug release through mechanical stimulation. The release volume per load is [missing data]. satisfy: in For compressive strain, .

6. The 3D-printed knee cartilage repair scaffold with integrated drug sustained-release function according to claim 1, characterized in that, The bone phase layer (3) is embedded with radially arranged gradient mineralized microchannels. The inner wall of the channel is deposited with amorphous calcium phosphate (ACP), low-crystallinity hydroxyapatite (HA) and high-crystallinity HA from the inside to the outside. The crystallinity increases linearly from 0% to 70%, promoting bone integration. The microchannels intersect with the spiral interpenetrating pore network (4) to form a three-dimensional vascularized guiding path.

7. The 3D-printed knee cartilage repair scaffold with integrated drug sustained-release function according to claim 1, characterized in that, The composite material comprises: and And by introducing Graphene oxide enhances thermal conductivity and cell-directed migration ability; the compressive modulus of the scaffold in a wet state satisfy And in 10 6 Modulus retention rate after each compression cycle is ≥85%.

8. A 3D-printed knee cartilage repair scaffold with integrated drug sustained-release function according to claim 1, characterized in that, The microfluidic chamber and the helical interpenetrating channel network (4) are integrally formed in the 3D printing process through a multi-nozzle collaborative deposition process: the first nozzle extrudes GelMA-based ink containing cells / drugs, the second nozzle synchronously deposits molten PCL as structural support and chamber wall, and the third nozzle sprays photoinitiator atomized liquid to achieve in-situ cross-linking, with interlayer alignment accuracy ≤ ±20μm.

9. A 3D-printed knee cartilage repair scaffold with integrated drug sustained-release function according to claim 1, characterized in that, The bioactive modified layer comprises a bifunctional coating: the bottom layer consists of covalent anchoring sites formed by treatment with a silane coupling agent (such as APTES), and the top layer consists of a covalent complex of RGD peptide and hyaluronic acid (HA), with a molar ratio of... Surface charge density (pH=7.4) significantly promotes chondrocyte adhesion and anti-fibrosis.

10. A 3D-printed knee cartilage repair scaffold with integrated drug sustained-release function according to claim 1, characterized in that, The scaffold maintained a local TGF-β3 concentration ≥10 ng / mL at week 4 post-implantation, while the shear strength at the interface between the newly formed tissue and the host cartilage was ≥0.3 MPa. In vitro dynamic compression experiments showed that the drug release rate under loading conditions was 2–4 times higher than that under static conditions, confirming the effectiveness of the mechanical-biochemical coupling release mechanism.

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