Ultrasound-responsive antibacterial osteogenic composite scaffold and preparation method thereof

Abstract

The application discloses an ultrasonic response type antibacterial osteogenic composite scaffold and a preparation method thereof, and belongs to the technical field of biomedical additive manufacturing and orthopedic implant materials. The scaffold is formed by integrating a medical degradable PLLA as a base body and in-situ grown MoS2@pCu-MOF type narrow-band-gap heterojunction fillers through selective laser sintering (SLS). The application constructs a 0.6 eV narrow-band-gap type II heterojunction interface, and realizes efficient electron-hole separation under ultrasonic excitation by relying on the built-in microelectric field in the interface. Meanwhile, a stable microcurrent is generated by using the ultrasonic piezoelectric effect of MoS2, and the scaffold releases PO4 3- ions, so that the bone marrow mesenchymal stem cell osteogenic gene pathway is activated in a double-pathway cooperative mode, and the key technical pain points of traditional bone repair scaffolds, such as H2O2 dependence and insufficient antibacterial depth, are solved. The scaffold has excellent biocompatibility, can be uniformly degraded, is suitable for multiple clinical scenes such as traumatic bone defects, and has good clinical transformation and industrialization prospects.

Description

Technical Field

[0001] This invention belongs to the field of biomedical additive manufacturing and orthopedic implant materials technology, specifically involving an ultrasound-responsive MoS2@pCu-MOF / PLLA antibacterial osteogenic composite scaffold based on type II heterostructure and its SLS integrated preparation process. It is suitable for clinical repair of traumatic bone defects, bone reconstruction after bone tumor surgery, osteoporotic bone defects, diabetic infectious refractory bone defects, and war wound infectious bone defects, and belongs to the category of Class III orthopedic implant device technology. Background Technology

[0002] Bone defects, bone infections, and postoperative infection recurrence are common and complex conditions in orthopedic clinics, seriously affecting bone healing and patient prognosis. Existing bone defect repair scaffolds and treatment plans face many unavoidable technical bottlenecks, mainly concentrated in insufficient anti-infection capabilities, imbalance between antibacterial and osteogenic functions, low structural biomimicry, poor biocompatibility, and difficulties in industrialization.

[0003] Traditional antibiotic-based bone cement implantation is prone to inducing bacterial resistance with long-term implantation and has a high recurrence rate of deep postoperative infections. Silver-based and copper-based single-metal antibacterial materials have the toxicity of heavy metal ion burst release and accumulation, which can inhibit stem cell activity and hinder bone regeneration. Photodynamic antibacterial materials have a penetration depth of less than 3 mm and cannot remove hidden infection foci in deep bone marrow and large bone defects. Traditional copper phosphate-based metal-organic framework (pCu-MOF) chemodynamic therapy is highly dependent on high concentrations of H2O2 in the lesion. In normal bone tissue, low-inflammation, and the microenvironment of diabetic refractory bone defects, the H2O2 content is extremely low, resulting in insufficient reactive oxygen species generation and essentially ineffective antibacterial function.

[0004] Meanwhile, existing commercial bone repair scaffolds generally suffer from limited functionality: pure antibacterial materials lack osteoinductive and osteoconductive capabilities, while calcium-phosphorus osteogenic materials have weak antibacterial properties, making it difficult to balance anti-infection and rapid bone regeneration; most scaffolds lack a biomimetic microenvironment, failing to simulate the piezoelectric effect of natural human bone, resulting in long bone integration cycles and low repair efficiency. In terms of molding processes, traditional casting and molding processes result in disordered pores and poor connectivity, hindering cell infiltration and nutrient transport; conventional 3D-printed composite scaffolds are prone to functional filler aggregation and significant batch-to-batch performance variations, and most materials are non-degradable, requiring secondary surgery for removal, increasing patient trauma and medical costs.

[0005] In recent years, sonodynamic response materials, MOF-based composite materials, and 3D-printed bone repair scaffold technologies have developed rapidly. However, most of the patents and research published between 2024 and 2026 focus on single-technology directions such as sonodynamic modification of MoS2, single-Cu-MOF ion antibacterial properties, and conventional PLLA structure printing. Significant technological gaps remain: existing sonodynamic materials have not constructed narrow-bandgap type II heterojunctions adapted to low-power ultrasound excitation, exhibiting high charge recombination rates, low ROS production efficiency, and a general reliance on exogenous H2O2; conventional MOF-modified scaffolds rely solely on passive ion antibacterial action, lacking deep sterilization capabilities responsive to ultrasound; existing 3D-printed scaffolds only achieve structural biomimicry, failing to construct a dual-synergistic osteogenic system of "chemical ion regulation + physical electrical stimulation"; and most laboratory materials lack standardized mass production processes and complete medical safety evaluation systems, failing to meet the clinical compliance and industrialization requirements for Class III implantable devices.

[0006] In summary, there is an urgent clinical need for an integrated bone repair composite scaffold that is H2O2-free, provides deep ultrasound-guided anti-infection, synergistically promotes antibacterial and osteogenic effects, has a precisely controllable structure, is biosafe and biodegradable, and can be mass-produced. Summary of the Invention

[0007] Purpose of the invention This invention aims to overcome the shortcomings of existing technologies, such as chemically driven antibacterial dependence on H2O2, weak ability to clear deep infections, imbalance of antibacterial and osteogenic functions, poor molding precision, insufficient biosafety, and low industrialization stability. It provides an ultrasound-responsive antibacterial osteogenic composite scaffold and its preparation method, achieving the technical effects of autonomous antibacterial action without external triggering, deep sterilization and film removal, synergistic bone regeneration through dual mechanisms, personalized and precise molding, and safe and biodegradable mass production, which can meet the clinical repair needs of complex bone defects in multiple scenarios.

[0008] Technical solution To achieve the above-mentioned objectives, the present invention adopts the following technical solution: An ultrasound-responsive MoS2@pCu-MOF / PLLA antibacterial osteogenic composite scaffold is disclosed. The composite scaffold is formed by sintering a biodegradable medical-grade poly-L-lactic acid (PLLA) matrix with MoS2@pCu-MOF type II heterojunction nanofiller. The MoS2@pCu-MOF is a stable type II cross-band heterojunction structure composed of molybdenum disulfide nanosheets supported in situ on a copper phosphate-based metal-organic framework. The heterojunction interface forms a fixed built-in micro-electric field. The composite scaffold is integrally formed by selective laser sintering (SLS), with a porosity of 50%~60%, a pore size of 200~300 μm, a pore connectivity of ≥92%, a dimensional accuracy error of ≤±50 μm, and a compressive strength of ≥25 MPa.

[0009] Under clinically safe low-power ultrasound stimulation of 1.8 W / cm², the MoS2@pCu-MOFⅡ heterostructure can efficiently separate electron-hole pairs without relying on in vivo H2O2 or exogenous chemical additives. It autonomously and stably generates hydroxyl radicals (·OH) and singlet oxygen (¹O2), which, combined with ultrasound mechanical vibration, dually destroy the bacterial cell membrane and biomembrane structure. The scaffold can uniformly and slowly release PO4³⁻ osteogenic ions, and at the same time, it generates a stable ultrasound piezoelectric microcurrent of ≥12 μA / cm² based on the piezoelectric effect of MoS2. Through the dual pathway of "ion chemical regulation + microcurrent physical stimulation", the osteogenic pathway is synergistically activated, realizing the integrated function of deep anti-infection and rapid bone regeneration.

[0010] Furthermore, the overall band gap of the MoS2@pCu-MOF type II heterojunction is 0.6 eV, with the pure pCu-MOF bulk band gap being 2.1 eV and the pure MoS2 bulk band gap being 1.4 eV. The heterojunction interface constructs a stable built-in micro-electric field at the atomic level, maintaining an electric field strength stably between 0.45 and 0.55 V. This forces electrons to migrate directionally from the MoS2 conduction band to the pCu-MOF conduction band, and holes to migrate directionally from the pCu-MOF valence band to the MoS2 valence band. This significantly suppresses disordered electron-hole recombination at the physical level, improving charge separation efficiency by 4.1 times compared to single materials and ROS production by 3.2 times compared to pure pCu-MOF chemodynamic therapy. This invention is strictly limited to a type II cross-band heterojunction, distinct from type I nested heterojunctions and Z-type composite structures. It can achieve stable and continuous reactive oxygen species generation under low-power ultrasonic excitation without energy loss, which is the core defining characteristic for achieving H2O2-free autonomous antibacterial activity.

[0011] Furthermore, the MoS2@pCu-MOF nanofiller is added to the PLLA matrix at a mass fraction of 5 wt%~15 wt%; the composite scaffold has a cell survival rate of >95%, meets the GB / T 16886 medical material safety standard, has no cytotoxicity or hemolytic sensitization reaction, can be uniformly and completely degraded in vivo, with a degradation cycle of 6~12 months, and the degradation rate matches the growth rate of new bone tissue.

[0012] Furthermore, the ultrasound response conditions are as follows: ultrasound power 1.8 W / cm², single treatment duration 5 min, which is a safe and non-invasive condition for human tissue; under the synergistic effect of ultrasound, the fluorescence intensity of bacterial outer membrane permeability reaches 140, the OD420 value of inner membrane permeability is 0.25, the bacterial glutathione (GSH) consumption rate is >80%, completely destroying the bacterial antioxidant system and cell membrane integrity; the bactericidal rate against Staphylococcus aureus is ≥99%, the bactericidal rate against Escherichia coli is ≥98.5%, the bacterial biofilm clearance rate is ≥96%, and the effective penetration depth of ultrasound is ≥5 cm, which can completely remove deep hidden infection lesions in bone defects.

[0013] Furthermore, the PO4³⁻ ions and ultrasonic piezoelectric microcurrent can synergistically activate the Runx2 / BMP-2 / Wnt-10b osteogenic gene pathway in bone marrow mesenchymal stem cells, forming a dual synergistic osteogenic mechanism: PO4³⁻ ions can participate in the in-situ mineralization and deposition of hydroxyapatite, constructing a biomimetic inorganic mineral structure of bone; ≥12 μA / cm² microcurrent can activate calcium ion channels in stem cell membranes, promoting cell adhesion, spreading, proliferation, and osteogenic differentiation, and bidirectionally upregulating the mRNA and protein expression levels of core osteogenic genes. In the cell co-culture system, the scaffold can increase early ALP activity in stem cells by 30.8% and late-stage calcium nodule formation by 36%, significantly accelerating bone mineralization and bone integration processes, while also improving the inflammatory microenvironment of osteoporosis and hyperglycemia, adapting to the repair of refractory bone defects.

[0014] A method for preparing an ultrasound-responsive MoS2@pCu-MOF / PLLA antibacterial osteogenic composite scaffold as described above includes the following steps: S1. Preparation of thin-layer MoS2 nanosheets by hydrothermal method: 0.02 mol sodium molybdate dihydrate and 0.1 mol thiourea were dissolved in 80 mL of ultrapure water and magnetically stirred for 30 min until completely clear. The solution was transferred to a polytetrafluoroethylene-lined reactor and kept at 200 ℃ for 12 h. After natural cooling, the black precipitate was collected. The nanosheets were washed 5 times by alternating centrifugation with ethanol and ultrapure water at a speed of 8000 r / min for 10 min each time. The nanosheets were then vacuum dried at 60 ℃ for 24 h to obtain thin-layer MoS2 nanosheets with a thickness of 5-15 nm. The nanosheets were free of lumpy agglomeration and had high purity.

[0015] S2. In-situ hydrothermal synthesis of MoS2@pCu-MOF type II heterojunction nanopowder: All raw materials were medical-grade high-purity (purity ≥99.9%). Dry MoS2 powder was dispersed in an ethanol-water mixture (volume ratio 3:7), ultrasonically dispersed at 300 W for 60 min, and then copper nitrate trihydrate and organic phosphate ligand were added sequentially. The mixture was continuously magnetically stirred for 40 min to form a uniform suspension. The suspension was transferred to a high-pressure reactor and kept at 160 ℃ for 8 h to uniformly grow pCu-MOF nanocrystals in situ on the surface of the MoS2 sheets, spontaneously forming a structurally stable type II cross-band heterojunction. After natural cooling to room temperature, the composite powder was collected by low-speed centrifugation at 6000 r / min. The powder was washed three times with ethanol to thoroughly remove free copper ions and unreacted organic ligands, and repeatedly washed with ultrapure water until the supernatant was colorless and transparent with no copper ion color reaction. The powder was then freeze-dried at -40 ℃ for 24 hours. h, to avoid high temperature damage to the band structure and micromorphology of the heterojunction interface, to obtain high-purity heterojunction powder; single batch synthesis amount ≥50 g, overall powder dispersion >97%, uniform grain size, no agglomeration, batch performance deviation ≤3%, meeting the stability requirements of pilot production.

[0016] S3. Preparation of Composite Printing Powder: Accurately weigh MoS2@pCu-MOF powder and medical spherical PLLA powder (particle size 50~80 μm, medical implant grade) according to the preset mass ratio; place them in a planetary ball mill, configure zirconia grinding balls with a ball-to-powder ratio of 5:1, add a trace amount of medical-grade dispersant (addition amount ≤0.5 wt%), and ball mill at 250 r / min for 4 h at room temperature in the dark, isolating moisture and impurities throughout the process to obtain uniform composite printing powder; Powder quality control standards: multi-point EDS elemental analysis shows that Mo and Cu elements are uniformly distributed, with no localized agglomeration; powder repose angle ≤32°, excellent flowability, suitable for high-speed uniform powder spreading by SLS; the prepared composite powder is sealed in a vacuum aluminum foil bag for moisture-proof and light-proof storage, with a shelf life of 3 months, to prevent powder oxidation, agglomeration, and deterioration due to moisture.

[0017] S4 and SLS laser selective sintering integrated molding: The SLS molding chamber is evacuated and protected with high-purity nitrogen gas. The oxygen content in the chamber is continuously monitored and stably controlled to <0.1% to prevent high-temperature oxidation and carbonization of PLLA and failure of functional fillers. The molding substrate is preheated to 60 ℃ to eliminate molding temperature difference stress and avoid scaffold warping, deformation, and cracking. A three-dimensional CAD biomimetic model is constructed based on the patient's bone defect CT / MRI scan data, and the gradient pore structure is adaptively adjusted to achieve personalized molding. Layered sintering is performed using a fiber infrared laser with the following process parameters: laser power 8~12 W, scanning rate 100~300 mm / s, layer thickness 50μm, and scanning spacing 0.1 mm. Powder is precisely laid layer by layer and laser melting and sintering are performed to fully melt and encapsulate the nanofiller in the PLLA matrix, achieving a tight bond between the filler and the matrix. After molding, the scaffold is slowly cooled in the furnace for 2 h in a nitrogen inert atmosphere to completely eliminate the molding internal stress, ensuring the dimensional accuracy and mechanical stability of the scaffold, and obtaining a porous scaffold semi-finished product with complete structure and interconnected pores.

[0018] Furthermore, the preferred molding process parameters in step S4 are: laser power 10 W, scanning rate 200 mm / s, scanning spacing 0.1 mm, and substrate preheating 60 ℃. Under these parameter ranges, the powder sintering is uniform, without over-burning or unsintered defects. After molding, the composite scaffold has a compressive strength ≥25 MPa, and the optimal embodiment has a compressive strength of 28 MPa. The bending strength is ≥18 MPa, and the elastic modulus matches that of human cortical bone, fully meeting the physiological load of human bone and the mechanical needs of daily activities.

[0019] S5. Post-processing and Aseptic Packaging: The semi-finished product is first thoroughly purged with low-pressure dust-free airflow to remove any unsintered free powder residue in the pores of the stent. Then, it undergoes three ultrasonic cleanings with anhydrous ethanol, each lasting 15 minutes, to remove surface organic residues and fine impurities. It is then vacuum-dried at 40°C for 6 hours to completely remove solvent and moisture. Following this, it undergoes a 100W argon atmosphere low-temperature plasma surface treatment for 5 minutes to optimize the surface hydrophilicity of the stent, reducing the water contact angle to below 35°, significantly improving the adhesion, spreading, and proliferation capabilities of stem cells. Medical-grade ethylene oxide (EO) sterilization is performed at 45°C for 12 hours, followed by 72 hours of ventilation and desorption after sterilization to ensure EO residue ≤10 μg / g, meeting the standards for Class III implantable devices. Finally, vacuum aseptic packaging is completed in a Class 10,000 GMP cleanroom, with a sterility assurance level (SAL) ≤10⁻. 6 It is free of pyrogens and allergens and can be directly used for clinical implantation.

[0020] A clinical application of the composite scaffold described above, wherein the composite scaffold is used to prepare implantable devices for repairing deep-infected bone defects, applicable scenarios include traumatic bone defects, bone reconstruction after bone tumor resection, osteoporotic bone defects, repair of war wound bone infections, and diabetic refractory bone defects; the method of use is as follows: after the scaffold is implanted into the bone defect lesion, it is periodically irradiated externally with low-power ultrasound at 1.8 W / cm², with a single irradiation of 5 min and an interval of 24 h. There is no thermal damage or tissue stimulation throughout the process, and no need for additional implantation of antibiotics or metal ion sustained-release systems. It simultaneously achieves in-situ sterilization, removal of biofilm, inhibition of infection recurrence and acceleration of bone regeneration, and is suitable for long-term implantation and repair needs.

[0021] Optimization of implementation parameters and operating condition adaptation scheme 1. General standard working conditions: MoS2@pCu-MOF filler addition amount 10 wt%, ultrasonic power 1.8 W / cm², SLS laser power 10 W, suitable for repairing various bone defects in plains and normal climates, with optimal comprehensive antibacterial, osteogenic and mechanical properties.

[0022] 2. Low-infection, mild bone defect conditions: The filler addition amount is 5 wt%, which is suitable for mild cases and low infection risk bone defects. While ensuring basic repair performance, it further reduces the risk of material toxicity and has higher biosafety.

[0023] 3. Severe infection and large bone defect conditions: The filler addition amount is 15 wt%, which enhances the ROS generation efficiency and antibacterial and biofilm elimination capabilities, and is suitable for severe infection and large bone defects after osteomyelitis and tumor surgery.

[0024] 4. Special working conditions with high altitude and large temperature difference: Based on the standard process, a low temperature annealing step is added to slow down the cooling rate after SLS molding, eliminate low temperature stress, optimize the low temperature dimensional stability and mechanical retention rate of the scaffold, and adapt to bone defect repair scenarios in high altitude and cold, outdoor combat injury, and extreme temperature difference environments. There is no significant attenuation of antibacterial, osteogenic, and mechanical properties under extreme temperatures.

[0025] 5. Diabetic Infected Bone Defect Conditions: Using an optimal filler ratio of 10 wt%, relying on the deep ultrasonic antibacterial and long-lasting anti-inflammatory properties, it is adapted to the microenvironment of diabetic bone defects characterized by high blood sugar, high inflammation, and low cell activity. It can effectively eliminate drug-resistant bacteria, improve the local microenvironment, and promote the repair of refractory bone defects.

[0026] Beneficial effects Compared with the prior art, the present invention has the following prominent substantive features and significant progress: 1. Breaking through the H2O2 dependence bottleneck of traditional chemodynamic therapy, achieving autonomous antibacterial action without external triggering. This invention constructs a 0.6 eV narrow bandgap MoS2@pCu-MOF type II heterojunction. Through an interface-stable built-in electric field, it efficiently separates electron-hole pairs, significantly suppressing disordered charge recombination and significantly improving charge separation efficiency. The ROS production is 3.2 times higher than that of the pure pCu-MOF system. It can stably generate reactive oxygen species in the normal physiological environment of low H2O2 in vivo and in the low-inflammatory microenvironment of diabetes, completely solving the industry pain point of antibacterial failure in low-inflammatory lesions of traditional CDT therapy.

[0027] 2. Achieve precise, deep-penetration anti-infection with low-power ultrasound, eliminating bacterial resistance. Utilizing clinically safe low-power ultrasound at 1.8 W / cm², it causes no thermal damage or stimulation to human soft tissue and bone. The effective penetration depth of ultrasound can reach 6 cm, thoroughly clearing hidden infection foci deep in the bone marrow and large bone defects. Through a dual mechanism of ROS oxidative damage and ultrasonic mechanical membrane disruption, it powerfully consumes intracellular GSH in bacteria, disrupts cell membrane integrity and biomembrane structure, and broadly kills Gram-positive and Gram-negative bacteria without the need for antibiotics, thus eliminating bacterial resistance and drug toxicity at the source.

[0028] 3. Constructing an ion-acoustic-electric dual-mode synergistic osteogenic system to significantly shorten the bone integration cycle. This invention innovatively combines PO4³⁻ ion mineralization regulation with ultrasonic piezoelectric microcurrent physical stimulation, synergistically upregulating the expression of Runx2 / BMP-2 / Wnt-10b core osteogenic genes through dual pathways. This effectively promotes stem cell adhesion, proliferation, and osteogenic differentiation, increases early ALP activity and late-stage calcium nodule deposition, significantly accelerates bone mineralization and bone integration, and improves the inflammatory microenvironment of osteoporosis and hyperglycemia, making it suitable for the repair of various refractory bone defects.

[0029] 4. SLS integrated precision molding, with excellent structural biomimicry and mechanical adaptability. This invention adopts standardized SLS additive manufacturing process, with precise control over the scaffold porosity, pore size, and pore connectivity. The pore connectivity is ≥92%, and the three-dimensional through-pore structure adapts to cell infiltration, nutrient transport, and angiogenesis. The molding accuracy is ±50 μm, and personalized modeling and printing can be achieved by combining patient CT / MRI images, accurately matching bone defects of different shapes and sizes. The PLLA matrix can completely degrade at a uniform rate of 6-12 months, and the degradation rate is highly matched with the bone regeneration rate, eliminating the need for secondary surgery for removal. The scaffold has stable mechanical properties, and its elastic modulus conforms to the human body's natural bone, effectively supporting postoperative mechanical loads and preventing defect collapse and displacement.

[0030] 5. High biocompatibility, fully compliant with Class III implantable device standards. This invention provides uniform and sustained release of copper and molybdenum ions, with no local accumulation or toxicity; the finished product exhibits a cell viability rate >95%, a hemolysis rate ≤1%, and exhibits no cytotoxicity, skin sensitization, or local tissue irritation; EO sterilization residue and sterility assurance levels meet standards, with no pyrogen reaction, ensuring complete medical safety.

[0031] 6. Standardized process, strong batch stability, suitable for industrial mass production. The entire preparation process of this invention is controllable and quantifiable, with a single batch yield of heterojunction powder ≥50 g, uniform powder dispersion, and batch performance deviation ≤3%. A three-level quality control system for raw materials, semi-finished products, and finished products is established, coupled with GMP aseptic packaging technology, which completely solves the defects of existing laboratory materials in batch instability and inability to be industrialized, and has high clinical translational value. Detailed Implementation

[0032] The present invention will be further described in detail below with reference to specific embodiments. These embodiments are only for explaining the present invention and are not intended to limit the scope of protection of the present invention.

[0033] Example 1: Optimal Ratio Universal MoS2@pCu-MOF / PLLA Composite Scaffold This embodiment represents the optimal engineering implementation, suitable for most common clinical bone defect scenarios. The specific preparation steps are as follows: 1. Preparation of thin-layer MoS2 nanosheets: 0.02 mol sodium molybdate dihydrate and 0.1 mol thiourea were precisely proportioned, dissolved in 80 mL of ultrapure water, and subjected to hydrothermal reaction at 200 ℃ for 12 h. After centrifugation, alternating washing, and vacuum drying, pure thin-layer MoS2 nanosheets with a thickness of 5~15 nm were obtained.

[0034] 2. Synthesis of heterojunction powder: MoS2 powder was dispersed in a 3:7 ethanol-water mixed solvent, ultrasonically pretreated for 60 min, copper nitrate trihydrate and organophosphate ligand were added and stirred at a constant speed, and pCu-MOF grains were grown in situ by hydrothermal treatment at 160 ℃ for 8 h. After freeze-drying, high-purity MoS2@pCu-MOF powder with a dispersion of 98% was obtained, with a single batch yield of 60 g.

[0035] 3. Powder blending: According to the mass ratio of 10 wt% MoS2@pCu-MOF and 90 wt% medical PLLA powder, a trace amount of medical dispersant was added, and the mixture was ball-milled for 4 h to obtain a uniform, non-agglomerated composite printing powder.

[0036] 4. SLS molding: Using optimized process parameters, laser power 10 W, scanning rate 200 mm / s, layer thickness 50 μm, scanning spacing 0.1 mm, substrate preheating 60 ℃, molding in a nitrogen protective atmosphere, and slow cooling in the furnace, a porous scaffold with a porosity of 55%, pore size of 250 μm, and interconnected pores was obtained, with a compressive strength of 28 MPa.

[0037] 5. Post-processing and sterilization: After airflow purging, ultrasonic cleaning with ethanol, vacuum drying, plasma activation, EO sterilization and analysis, and aseptic packaging in a GMP workshop, the finished product SAL ≤ 10⁻ 6 .

[0038] Performance test results: After 5 min of ultrasound treatment at 1.8 W / cm², the ROS production was 3.2 times that of the pure pCu-MOF system, and the production of ·OH and ¹O2 was stable and controllable; the sterilization rate of Staphylococcus aureus was 99.2%, the sterilization rate of Escherichia coli was 98.8%, and the bacterial biofilm clearance rate was ≥96%; the bacterial GSH consumption rate was >80%, and the cell membrane structure was completely destroyed; the ALP activity of stem cells increased by 30.8%, the amount of calcium nodule formation increased by 36%, and the expression of osteogenic core gene protein was significantly upregulated; the cell survival rate was 96.7%, the hemolysis rate was 0.8%, and there was no sensitization reaction; the in vivo degradation cycle was 9 months, and there was no accumulation of acidic substances or inflammatory reaction during the degradation process, and the effective penetration depth of ultrasound was 6 cm.

[0039] Example 2: Scaffold for mild bone defects with low filler ratio In this embodiment, the filler content is 5 wt%, and the remaining preparation process and parameters are the same as in Example 1, suitable for repairing mild bone defects with low infection risk. Performance test results: Staphylococcus aureus sterilization rate of 96.5%, Escherichia coli sterilization rate of 95.1%, stem cell ALP activity increased by 21%, cell survival rate >97%, further improving biosafety and meeting the needs of mild bone defect repair.

[0040] Example 3: Special scaffold for severely infected bone defects with high filler ratio In this embodiment, the filler content is 15 wt%, and the remaining preparation process and parameters are the same as in Example 1. It is suitable for osteomyelitis and severe infection with large bone defects after tumor surgery. Performance test results: the sterilization rate of Staphylococcus aureus and Escherichia coli is >99.5%, and the ROS generation efficiency and biofilm removal ability are significantly improved; the scaffold porosity is 52%, the mechanical properties meet the standards, and it can completely remove deep severe infections, achieving simultaneous infection control and bone regeneration.

[0041] Example 4: High-altitude, large-temperature-difference-adapted support frame The basic formula in this embodiment is the same as that in Example 1. A low-temperature annealing process is added after SLS molding to slow down the cooling rate, eliminate low-temperature internal stress, and optimize the low-temperature dimensional stability of the stent. Performance test results: The stent showed no deformation or degradation of mechanical properties under extreme temperature conditions. Its antibacterial and osteogenic properties remained consistent with those under normal temperature conditions, making it suitable for repairing special scenarios such as high-altitude cold environments and outdoor combat injuries.

[0042] Comparative Example 1: Pure PLLA Blank Frame It is made from pure medical-grade PLLA powder using the same SLS process, without functional fillers. Test results: It has no independent antibacterial properties, no osteogenic induction ability, only provides physical support, slow bone integration, and cannot resist postoperative bacterial infection and inflammatory response.

[0043] Comparative Example 2: Single MoS2 / PLLA Composite Scaffold Only 10 wt% MoS2 nanosheets were added, without the pCu-MOF composite heterojunction structure. Test results: No ultrasonic response to produce ROS antibacterial ability, only a weak piezoelectric osteogenesis effect, completely lacking antibacterial function, and unsuitable for repairing infected bone defects.

[0044] Comparative Example 3: Single pCu-MOF / PLLA Composite Scaffold Only 10 wt% pCu-MOF powder was added, without the MoS2 heterojunction composite structure. Test results: It is highly dependent on the generation of reactive oxygen species from high concentrations of H2O2 in vivo. Under normal physiological conditions and low-inflammatory lesions, the antibacterial rate is less than 70%, and the ROS production is extremely low. There is no piezoelectric microcurrent output or physical osteogenic stimulation pathway. It relies solely on a single ion to weakly promote bone regeneration. Its function is singular, its performance stability is poor, and it cannot simultaneously achieve anti-infection and efficient bone regeneration. Attached Figure Description

[0045] Figure 1 is a schematic diagram of the band structure of the MoS2@pCu-MOFII heterojunction of the present invention; Figure 2 is a schematic diagram of the electron-hole separation and ROS generation mechanism under ultrasonic excitation of the present invention; Figures 3 and 4 show the characteristic peak spectra of OH and O2 in the EPR test of this invention; Figures 5, 6, and 7 are X-ray photoelectron spectroscopy (XPS) spectra of the MoS2@pCu-MOF composite material of the present invention; Figure 8 shows a comparison of the SEM morphology of bacteria before and after ultrasonic treatment according to the present invention; Figure 9 shows a comparison of early osteogenic activity of the scaffolds in the present invention after ALP staining. Figure 10 shows a comparison of the late-stage osteogenic effects of alizarin red calcium nodules stained with the scaffolds of the present invention. Figures 11 and 12 are SEM images of the microstructure of the SLS-molded porous support of the present invention. Figure 13 is a flowchart of the preparation process of the present invention.

Claims

1. An ultrasound-responsive antibacterial osteogenic composite scaffold, characterized in that, The scaffold is formed by sintering a biodegradable medical PLLA matrix with MoS2@pCu-MOF type II heterojunction nanofiller. The MoS2@pCu-MOF is a stable type II cross-band heterojunction composed of molybdenum disulfide nanosheets supported in situ on a copper phosphate-based metal-organic framework, with a fixed built-in electric field at the interface. The scaffold is integrally formed using selective laser sintering (SLS), with a porosity of 50-60%, pore size of 200-300 μm, pore connectivity ≥92%, dimensional accuracy error ≤±50 μm, and compressive strength ≥25 MPa. Under clinically safe low-power ultrasound excitation at 1.8 W / cm², the MoS2@pCu-MOF heterojunction efficiently separates electron-hole pairs, autonomously and stably generating hydroxyl radicals (·OH) and singlet oxygen (¹O2) without relying on in vivo H2O2 or exogenous chemical additives. This, combined with ultrasonic mechanical vibration, causes dual destruction of bacterial membrane structure and biofilm. The scaffold can uniformly and slowly release PO4³⁻ osteogenic ions and generate ≥12 A stable ultrasonic piezoelectric microcurrent of μA / cm² is used to achieve a dual function of acoustic-dynamic deep antibacterial and ion-microcurrent synergistic osteogenic synthesis.

2. The ultrasound-responsive MoS2@pCu-MOF / PLLA antibacterial osteogenic composite scaffold according to claim 1, characterized in that, The MoS2@pCu-MOF heterojunction has an overall band gap of 0.6 eV, while the pure pCu-MOF bulk band gap is 2.1 eV and the pure MoS2 bulk band gap is 1.4 eV. A stable built-in micro-electric field of 0.45~0.55 V is formed at the heterojunction interface, driving the directional migration of electrons and holes and inhibiting disordered electron-hole recombination. The charge separation efficiency is 4.1 times higher than that of single materials, and the ROS yield is 3.2 times higher than that of pure pCu-MOF chemodynamic therapy.

3. The ultrasound-responsive MoS2@pCu-MOF / PLLA antibacterial osteogenic composite scaffold according to claim 1, characterized in that, The MoS2@pCu-MOF nanofiller is added to the PLLA matrix at a mass fraction of 5-15 wt%; the scaffold has a cell survival rate of >95%, no obvious cytotoxicity or hemolytic sensitization reaction, and an in vivo degradation period of 6-12 months, with the degradation rate matching the growth rate of new bone tissue.

4. The ultrasound-responsive MoS2@pCu-MOF / PLLA antibacterial osteogenic composite scaffold according to claim 1, characterized in that, The ultrasonic stimulation conditions were 1.8 W / cm², with a single treatment time of 5 min. Under the synergistic effect of ultrasound, the fluorescence intensity of bacterial outer membrane permeability reached 140, the OD420 value of inner membrane permeability was 0.25, and the bacterial glutathione (GSH) consumption rate was >80%. The sterilization rate against Staphylococcus aureus was ≥99%, the sterilization rate against Escherichia coli was ≥98.5%, the bacterial biofilm removal rate was ≥96%, and the effective penetration depth of ultrasound was ≥5 cm.

5. The ultrasound-responsive MoS2@pCu-MOF / PLLA antibacterial osteogenic composite scaffold according to claim 1, characterized in that, The PO4³⁻ ions and ultrasound microcurrent synergistically activate the Runx2, BMP-2, and Wnt-10b osteogenic gene pathways in bone marrow mesenchymal stem cells; under the cell co-culture system, early ALP activity of stem cells is increased by 30.8%, late-stage calcium nodule formation is increased by 36%, and bone mineralization and bone integration are accelerated.

6. A method for preparing the ultrasound-responsive MoS2@pCu-MOF / PLLA antibacterial osteogenic composite scaffold according to any one of claims 1 to 5, characterized in that, It includes the following steps: S1. Preparation of 5-15 nm thin-layer MoS2 nanosheets by hydrothermal method; S2. In-situ hydrothermal synthesis of MoS2@pCu-MOFⅡ type heterojunction nanopowder, with a single batch synthesis amount ≥50 g, powder dispersion >97%, and batch performance deviation ≤3%; S3. MoS2@pCu-MOF powder and medical PLLA powder are ball-milled and mixed to prepare uniform composite printing powder; S4. The three-dimensional porous biomimetic scaffold is integrally formed using selective laser sintering (SLS) technology, with forming accuracy controlled at ±50 μm. S5. The stent undergoes purging cleaning, surface activation, EO sterilization and analysis, and aseptic packaging. The finished product's sterility assurance level (SAL) is ≤10⁻. 6 Thus, a medical implantable composite stent was obtained.

7. The preparation method according to claim 6, characterized in that, In step S2, the in-situ synthesis process uses medical-grade high-purity molybdenum source, copper salt, and organophosphorus ligand. In a mixed solvent system with an ethanol-water volume ratio of 3:7, the reaction is carried out at 160 °C for 8 h to grow pCu-MOF grains in situ on the surface of MoS2 sheets. The interfacial bandgap is precisely controlled to form a 0.6 eV narrow bandgap type II heterojunction.

8. The preparation method according to claim 6, characterized in that, Step S4 SLS molding process parameters: laser power 8~12 W, scanning rate 100~300 mm / s, layer thickness 50 μm, scanning spacing 0.1 mm, substrate preheating 60 ℃, nitrogen atmosphere protection molding, and the compressive strength of the molded support ≥25 MPa.

9. The application of the composite scaffold according to any one of claims 1 to 5 in the preparation of implantable devices for repairing deep-infected bone defects, characterized in that, Application scenarios include traumatic bone defects, bone reconstruction after bone tumor resection, osteoporotic bone defects, repair of war wound bone infections, and diabetic infectious refractory bone defects.

10. The application according to claim 9, characterized in that, Usage: After the stent is implanted into the bone defect site, it is periodically irradiated with low-power ultrasound at 1.8 W / cm², 5 min per session, with an interval of 24 h. There is no thermal damage or tissue stimulation throughout the process. It can simultaneously achieve in-situ sterilization, removal of bacterial biofilm, inhibition of infection recurrence and acceleration of bone regeneration. There is no need to implant additional antibiotics or metal ion sustained-release systems. It is suitable for long-term repair treatment of various types of bone defects.

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