A mineralized facial implant and method of making same

Abstract

The application discloses a mineralized facial implant line and a preparation method thereof, and belongs to the technical field of medical implant materials. The method comprises the following steps: performing microphysical etching on the surface of a high-molecular implant line to form a uniform micro-pit structure; adsorbing a polydopamine film on the etched surface; performing biomimetic mineralization in a supersaturated calcium-phosphorus solution containing zinc ions to form a zinc-doped hydroxyapatite coating; and covalently grafting an enzyme-sensitive drug conjugate on the surface of the coating. The implant line prepared by the method has excellent biocompatibility, strong coating bonding force, good tissue integration capacity and intelligent drug release function, can effectively reduce inflammatory reactions and prevent line body displacement, and improves the durability and safety of facial lifting.

Description

Technical Field

[0001] This invention relates to the field of medical implant materials and tissue engineering, and more specifically, to an implantable thread for facial thread lifting with a bioactive coating and intelligent drug release function, and its preparation method. Background Technology

[0002] Facial thread lifting (commonly known as "thread sculpting") is a minimally invasive cosmetic procedure that uses absorbable threads to achieve facial rejuvenation through immediate lifting and subsequent stimulation of collagen regeneration. Currently, commonly used thread materials in clinical practice include synthetic polymers such as poly(p-dioxanone) (PPDO), poly(L-lactic acid) (PLLA), and polycaprolactone (PCL), as well as natural materials such as collagen threads.

[0003] Although these materials meet the basic requirements of absorbability and biocompatibility to a certain extent, they still reveal a series of significant shortcomings in practical applications: Biocompatibility and degradation byproducts: Polyester materials such as PPDO and PLLA produce acidic small molecules (such as lactic acid and glycolic acid) during in vivo degradation, which may lead to a decrease in the pH value at the implantation site, causing aseptic inflammation, chronic granulomas, or nodule formation, affecting postoperative recovery and the patient's experience. Although collagen threads have better biocompatibility, they suffer from insufficient mechanical strength, excessively rapid degradation rate, and poor batch-to-batch stability.

[0004] Insufficient tissue integration and risk of displacement: Existing implanted threads mainly rely on barbs, serrations, or conical structures on the surface of the thread for physical "anchoring." This mechanical hooking method does not bond firmly with soft tissue. Under the influence of facial muscle activity, gravity, and the reduction of tissue swelling, the thread is prone to displacement, slippage, or even breakage, resulting in asymmetrical and short-lasting lifting effects, or even premature failure (see CN217338972U, whose disclosed serrated structure, while enhancing fixation, can cause cutting damage to the tissue). Smooth threads have even weaker fixation capabilities.

[0005] Lack of active regulation of the implantation microenvironment: Postoperative acute inflammatory response and potential infection risk are key factors affecting surgical success. Most existing implantation sutures are passive materials, lacking anti-inflammatory or antibacterial functions. Although some studies have attempted to load antibiotics or anti-inflammatory drugs through physical immersion, these methods suffer from problems such as sudden drug release, short duration of action, inability to respond to changes in the local microenvironment, and potential interference with the normal wound healing process.

[0006] To overcome the above problems, existing technologies have explored some approaches: Surface modification: such as plasma treatment of polymer wires to increase surface hydrophilicity and cell adhesion, but the modified layer is thin and has limited durability and bioactivity.

[0007] Composite coatings: Some studies have focused on preparing hydroxyapatite (HA) coatings on the surface of metal implants to improve osseointegration. However, directly applying this technology to flexible polymer implants faces challenges such as weak coating adhesion and easy cracking and peeling. HA coatings themselves do not possess intelligent drug release capabilities.

[0008] Drug delivery systems: For example, using microsphere-coated implants loaded with anti-inflammatory drugs, but drug release depends on the degradation of the microspheres, the release kinetics are difficult to control precisely, and the binding stability with the matrix is ​​poor.

[0009] Therefore, there is an urgent need in this field to develop a new type of facial implant thread and its preparation method. It should not only have excellent biocompatibility and strong tissue integration ability to prevent displacement and ensure long-lasting lifting effect, but also be able to intelligently respond to inflammatory signals at the implantation site and actively release anti-inflammatory drugs to achieve a leap from "passive implantation" to "active regulation of healing". Summary of the Invention

[0010] To overcome the shortcomings of existing technologies, this invention aims to provide a mineralized facial implant thread and its preparation method. This method employs a multi-step synergistic biomimetic mineralization and surface functionalization strategy to construct a firmly bonded, functionally integrated active coating on the implant thread surface, ultimately obtaining an implant thread product with excellent biocompatibility, anti-migration ability, and intelligent anti-inflammatory function.

[0011] To achieve the above objectives, the technical solution of the present invention is as follows: In a first aspect, the present invention provides a method for preparing mineralized facial implant threads.

[0012] The core concept of this method is as follows: First, the surface of the polymer implantation thread substrate is activated to create a micro-mechanical interlocking structure and introduce a strongly adhesive interface layer; then, a zinc-doped hydroxyapatite (Zn-HA) coating is mineralized and grown under biomimetic conditions, which has both bioactivity and antibacterial properties; finally, an enzyme-sensitive drug conjugate is fixed on the surface of the mineralized coating through covalent grafting to achieve intelligent drug release triggered by the inflammatory microenvironment.

[0013] Specifically, the preparation method includes the following key steps: S1. Microscopic Physical Etching: The polymer implanted wire is immersed in a weakly oxidizing mixed acid solution and treated at 25–40°C for 1–10 minutes to form a uniform micro-pit structure on the surface. This step aims to create a uniformly distributed nano / micro-scale pit (micro-pits and fibrous structure) on the surface of the wire without severely damaging its mechanical properties. This roughened surface provides a basis for the physical anchoring of subsequent coatings, significantly increasing the bonding area and mechanical locking force compared to a smooth surface or chemical treatment alone. The step parameters (25–40°C, 1–10 minutes) ensure the uniformity and controllability of the etching, avoiding over-etching that would reduce the wire strength.

[0014] S2. Polydopamine Adsorption: The etched embedded wire is immersed in a Tris-HCl buffer solution containing polydopamine and agitated at 25–37°C for 6–12 hours to form a PDA film. In this invention, PDA molecules can penetrate deep into the micro-pits formed in step S1 and adhere firmly, forming an ultrathin biomimetic adhesion layer. This PDA layer has a dual key function: firstly, as a "molecular glue," it strongly binds the etched surface to the subsequent mineralization layer through covalent / non-covalent interactions; secondly, the phenolic hydroxyl and amino groups on its surface can efficiently adsorb calcium, phosphorus, and zinc ions in the solution, providing a large number of uniform active sites for the heterogeneous nucleation of hydroxyapatite, which is a prerequisite for obtaining a uniform and dense mineralized coating.

[0015] S3. Zinc-doped biomimetic mineralization: PDA-modified implanted wires are immersed in a zinc-ion-containing mineralization solution and allowed to stand at 35–40°C for 3–5 days to form a zinc-doped hydroxyapatite coating. This step simulates the mineral deposition process in a biological organism. Ions enriched on the PDA layer guide hydroxyapatite (HA) crystals to preferentially nucleate on their surface and grow along a specific direction, forming a coating that is firmly bonded to the substrate. Zinc ion (Zn²⁺) doping (concentration 1–5 mmol / L) is introduced into the HA lattice. As described in the background art, a simple HA coating has good biocompatibility but lacks antibacterial properties. The introduction of Zn²⁺ endows the coating with durable antibacterial properties (by disrupting bacterial cell membranes and interfering with metabolism). At the same time, experiments show that appropriate zinc doping does not significantly impair the biological activity of HA; on the contrary, it may promote the activity of osteoblast-related cells, achieving a preliminary synergy between "antibacterial" and "promoting bone / soft tissue regeneration" functions.

[0016] S4. Surface Chemical Grafting: After amination of the mineralized implantation wire surface, an enzyme-sensitive drug conjugate is covalently grafted onto it via click chemistry. First, the Zn-HA coating is aminosilylated to introduce amino groups; then, a bifunctional crosslinking agent (such as Sulfo-SMCC) is used to convert the amino groups into maleimide active groups. Finally, a pre-synthesized enzyme-sensitive drug conjugate with terminal thiol groups (-SH) is covalently grafted onto the coating surface via click chemistry (thiol-maleimide). Compared to physical adsorption or encapsulation methods, this covalent grafting strategy effectively prevents drug burst release, ensuring that the drug does not easily detach during transportation, storage, and the initial implantation phase.

[0017] Furthermore, we optimized the etching solution, using a mixture of concentrated hydrochloric acid and hydrogen peroxide. This mixture has moderate oxidizing power, effectively etching the surfaces of commonly used polymers such as PPDO and PLLA to form the desired micro-rough structure, while avoiding the excessive degradation of the polymer backbone or drastic deterioration of mechanical properties that might occur with strong oxidants (such as concentrated nitric acid or aqua regia). A volume ratio of 3:1 to 7:1 is the optimized range, balancing etching efficiency with substrate protection.

[0018] We further optimized the PDA concentration, and the concentration of 1-3 mg / mL was selected through experiments. If the concentration is too low, it is difficult to form a continuous and complete PDA film, which affects the adhesion and nucleation effect; if the concentration is too high, it may lead to an excessively thick and uneven PDA layer, or even increased internal stress, which will reduce its bonding strength with the substrate and mineralization layer.

[0019] We further optimized the key ion concentrations of the mineralization solution. The ratio of calcium ion concentration (7–9 mmol / L) to hydrogen phosphate concentration (1–5 mmol / L) (Ca / P) is close to the theoretical value of hydroxyapatite and is in a slightly oversaturated state, which is conducive to mild and continuous biomimetic mineralization under PDA induction, forming a coating with moderate crystallinity and strong adhesion. The zinc ion concentration (1–5 mmol / L) ensures that Zn²⁺ can be effectively incorporated into the HA lattice to obtain stable antibacterial properties, while avoiding excessive concentration that may lead to abnormal crystal growth or increased risk of cytotoxicity.

[0020] We further optimized the structure of the enzyme-sensitive drug conjugate, which is the core molecule for achieving the intelligent drug release function of this invention. It consists of three parts: (a) a thiol group: serving as a fixed end for click chemistry with maleimide groups on the coating surface, ensuring a firm graft; (b) a polypeptide chain (GPLGVRGK), which is a specific substrate sequence for matrix metalloproteinase-9 (MMP-9) (this polypeptide chain is cited from the literature Netzel-Arnett S, Fields GB, Birkedal-Hansen H, et al. Sequence specificities of human fibroblast and neutrophilcollagenases[J]. Journal of Biological Chemistry, 1991, 266(11): 6747-6755.). MMP-9 is expressed at low levels during normal tissue healing, but is significantly upregulated at sites of inflammation, infection, or active tissue remodeling. The design of this sequence links drug release to the degree of local inflammation; (c) an anti-inflammatory drug (dexamethasone): a potent glucocorticoid used to suppress inflammatory responses. The polypeptide chain chemically conjugates with the hydroxyl group of dexamethasone via the amino group of its terminal lysine residue, forming a stable conjugate. When inflammation occurs at the implantation site and the concentration of MMP-9 enzyme increases, the enzyme specifically cleaves this polypeptide chain, thereby releasing dexamethasone and achieving precise regulation of "drug release only when inflammation occurs".

[0021] The present invention can also employ the following post-processing steps: cleaning the grafted implanted wire, freeze-drying it, and then sterilizing it with electron beam irradiation. Cleaning removes unreacted substances, freeze-drying facilitates long-term storage and maintains the porous structure of the coating, and electron beam irradiation sterilization (dose 25 kGy) ensures the product is sterile and has minimal impact on the coating structure and drug activity.

[0022] Secondly, the present invention provides a mineralized facial implant thread prepared by the above method.

[0023] Preferably, the multi-layer gradient structure of the embedding line, viewed in cross-section, consists of the following features from the inside out: Polymer matrix: Provides the main mechanical tensile strength; materials can be PPDO, PLLA, etc. Nano-roughened interface: Formed by etching in step S1, it is the physical basis for enhancing coating adhesion. Polydopamine (PDA) interlayer: An ultrathin adhesion layer that acts as a "bridge" for bonding and nucleation. Zinc-doped hydroxyapatite (Zn-HA) mineralization layer: The core functional layer, providing bioactivity, antibacterial properties, and a porous structure that bonds to tissues. Covalently grafted enzyme-sensitive drug conjugate layer: The outermost intelligent response unit, responsible for sensing and regulating the local inflammatory microenvironment. This gradient structure is not a simple stacking, but rather achieves strong chemical and physical bonding between layers through the aforementioned process steps, with functionally progressive and synergistic layers.

[0024] In a preferred embodiment, the polymeric thread matrix is ​​poly(p-dioxanone) (PPDO). Experiments show that the method of the present invention is particularly suitable for the surface functionalization modification of PPDO threads, which can significantly improve their clinical application performance.

[0025] The beneficial effects of this invention are comprehensively reflected in: 1) Strong coating adhesion: Through the synergy of "physical etching + PDA chemical adhesion", the industry problem of easy peeling of inorganic coatings on flexible polymer substrates is solved.

[0026] 2) Strong tissue integration: The porous micro-nano structure of the Zn-HA coating is similar to the composition of bone / teeth, which can promote cell adhesion and collagen ingrowth, achieve "biological anchoring", and greatly improve the resistance to displacement.

[0027] 3) Excellent biocompatibility: Zn-HA neutralizes acidic degradation products and reduces foreign body reactions; the sustained release of Zn²⁺ provides long-lasting antibacterial effects and reduces the risk of infection.

[0028] 4) Intelligent drug release: Based on the MMP-9 enzyme response drug release system, it realizes precise and on-demand drug delivery triggered by the inflammatory microenvironment, which is highly effective in anti-inflammatory and has a low risk of systemic side effects.

[0029] 5) Synergistic effect: The three functions of "antibacterial (Zn²⁺) - anti-inflammatory (intelligent drug release) - regeneration promotion (HA bioactivity)" work synergistically in time and space to create a microenvironment conducive to tissue healing and integration. Detailed Implementation

[0030] The present invention will be further described below with reference to embodiments.

[0031] The main raw materials used in the examples are as follows: PPDO implantation thread (0.3 mm in diameter, 30 cm in length) Concentrated hydrochloric acid (analytical grade) Hydrogen peroxide (30%) Polydopamine hydrochloride (Sigma) Calcium chloride, dipotassium hydrogen phosphate, zinc sulfate, etc. (all analytical grade) 3-Aminopropyltriethoxysilane (APTES) Sulfo-SMCC (Thermo) Dexamethasone, peptide Cys-GPLGVRGK (solid-phase synthesis) Example

[0032] S1. Preparation of etching solution: Mix concentrated hydrochloric acid and hydrogen peroxide at a volume ratio of 5:1 to obtain the etching solution; S2, Bionic Etching: Immerse the PPDO implanted wire completely in the etching solution, treat it at 30°C for 5 minutes, and then rinse it with deionized water 3 times. S3, PDA adsorption: Prepare a Tris-HCl buffer (pH=8.5) containing 2 mg / mL polydopamine, immerse the etched lines in the buffer, and shake at 30℃ and 80 RPM for 10 hours. After removal, wash with PBS. S4. Preparation of mineralization solution: Add calcium chloride (Ca²⁺ 8 mmol / L), sodium chloride, sodium bicarbonate, magnesium chloride, dipotassium hydrogen phosphate (PO₄³⁻ 3 mmol / L), and zinc sulfate (Zn²⁺ 3 mmol / L) to deionized water in sequence, and adjust the pH to 6.85; S5. Biomimetic mineralization: Immerse the PDA modification line in the mineralization solution, seal it, and place it at 38℃ for 4 days to mineralize. Replace the mineralization solution every 12 hours. S6. Cleaning: After mineralization, remove the product and clean it with deionized water at 180 RPM for 1.5 hours by shaking, changing the water every 8 minutes. S7. Surface amination: Immerse the mineralized line in 2% APTES anhydrous ethanol solution and react at room temperature for 2 hours, then wash with ethanol. S8. Maleimide activation: Immerse the aminated wire in PBS containing 1 mM Sulfo-SMCC and react in the dark for 1.5 hours, then wash with PBS. S9. Preparation of drug conjugates: Cys-GPLGVRGK polypeptide was synthesized by solid-phase synthesis, and its Lys terminus was conjugated with dexamethasone to obtain Cys-(GPLGVRGK)-Dex. S10, Surface grafting: Immerse the activated wire in PBS containing the above conjugate, shake at 25°C for 12 hours, and then wash with PBS; S11. Freeze-drying and sterilization: After cleaning, the sample is freeze-dried and then sterilized by electron beam irradiation (dose 25 kGy). Example

[0033] The difference from Example 1 is as follows: The S2 etching time has been changed to 8 minutes; The concentration of Zn²⁺ in the S4 mineralization solution was changed to 1 mmol / L; S5 mineralization time changed to 3 days; The S10 grafting reaction time has been changed to 6 hours.

[0034] The remaining steps are the same as in Example 1. Example

[0035] The difference from Example 1 is as follows: The S1 etching solution ratio is concentrated hydrochloric acid: hydrogen peroxide = 3:1; The adsorption time of S3 PDA was changed to 6 hours, and the oscillation speed was changed to 50 RPM. The concentration of Ca²⁺ in the S4 mineralized solution was changed to 7 mmol / L, and the concentration of PO₄³⁻ was changed to 5 mmol / L. The S5 mineralization temperature was changed to 35℃; The remaining steps are the same as in Example 1.

[0036] The difference from Example 1 is that steps S2 and S3 are omitted, that is, etching and PDA adsorption are not performed, and mineralization is performed directly.

[0037] The difference from Example 1 is that zinc sulfate is not added to the mineralization solution in step S4, that is, a zinc-free hydroxyapatite coating is prepared.

[0038] 1. Coating adhesion test 1.1 The samples from Example 1 were ultrasonically treated using an ultrasonic cleaner with a power of 300W for 30 minutes. After treatment, they were freeze-dried, and the coating peeling was observed using SEM. The coating residue rate was calculated by weighing. The results showed that after ultrasonic treatment, there was no significant large-scale peeling of the coating, and the coating residue rate was greater than 98%. This proves that the coating is firmly bonded to the substrate and can meet the mechanical requirements of implantation and the in vivo environment.

[0039] Table 1. Coating adhesion test results

[0040] 1.2 Nanoscale scratch tests were performed on Example 1 (the present invention group) and Comparative Example 1 (zinc-HA group, i.e., skipping the etching and PDA adsorption steps and directly mineralizing). Using a nanoscale scratch instrument, a linearly increasing load from 0 to 100 mN was applied, with a scratch length of 500 μm. The critical load at which the coating first showed continuous peeling was recorded, and the peeling phenomenon was observed using SEM.

[0041] Table 2. Results of Nanoscale Scratch Test

[0042] The results showed that the coating adhesion of the present invention group was approximately three times that of the zinc-HA group. The zinc-HA group's coating was grown directly on a smooth, inert PPDO surface, resulting in weak adhesion, primarily through physical attachment. In contrast, the present invention group created a nanoscale mechanical interlocking structure through biomimetic etching, while the PDA film provided strong chemical adhesion and numerous nucleation sites, enabling the HA crystals to be fixed to the substrate.

[0043] 2. Displacement resistance test Each of the samples from Example 1 and Comparative Example 1 in section 1.2 was cut to a length of 3 cm and implanted into polyacrylamide hydrogel to simulate human soft tissue, with an implantation depth of 5 mm. One end of each group was fixed using a mechanical testing machine, and the suture was pulled out vertically at a speed of 5 mm / min. The maximum pull-out force and the pull-out condition were recorded.

[0044] Table 3 Results of displacement resistance test

[0045] The results showed that the resistance to displacement of the sample in Example 1 was approximately 2.7 times that of Example 1 (zinc-HA group), and this resistance to displacement stemmed from the bonding between the coating and the tissue. While the zinc-HA group exhibited bioactivity, its coating had weak bonding and potentially poor uniformity. The present invention group, due to its stronger bonding and more uniform coating, possessed a porous structure that allowed for a wider and stronger bond with the gel (simulated tissue), thus requiring greater force to separate it.

[0046] 3. In vitro enzyme-responsive drug release kinetics A 2.0 cm section of sample from Example 1 was used as the experimental group. Solution A (PBS buffer only) and Solution B (PBS buffer containing 100 ng / mL recombinant human MMP-9 enzyme) were prepared. The experimental group samples were placed in Solutions A and B, respectively, with three replicates for each. The solutions were placed in a constant-temperature shaker at 37°C and 60 RPM. All solutions were collected at 0.5, 1, 2, 4, 8, 12, 24, 48, 72, and 120 h, and equal volumes of solution were added. The dexamethasone content in each group's solution was determined by high-performance liquid chromatography (HPLC).

[0047] Table 4 Results of in vitro enzyme-responsive drug release kinetics test

[0048] The results showed that the drug release rate in solution A was slow, reaching only 5.9% after 5 days, while the drug release in solution B was extremely rapid, reaching a plateau at 72 hours, and the drug content in solution B was 16 times that in solution A. This indicates that the drug release from the implanted thread of this invention is highly dependent on the presence of the MMP-9 enzyme.

[0049] 4. In vitro anti-inflammatory effect test Take a 1 cm long sample from Example 1 and place it in an EP tube containing 1 mL of sterile PBS. To simulate the inflammatory microenvironment and trigger drug release, add recombinant human MMP-9 enzyme to the PBS to a final concentration of 100 ng / mL. Incubate at 37°C for 24 hours, then collect the supernatant and filter it through a 0.22 μm filter membrane for sterilization to obtain the "sample extract". Prepare a "blank extract" using a standard PPDO thread in the same manner.

[0050] Mouse mononuclear macrophage leukemia cells were cultured in DMEM high-glucose medium containing 10% fetal bovine serum and 1% penicillin-dextrose antibody at 37°C for 24 hours. Cells in logarithmic growth phase were cultured at 1 × 10⁶ cells per well. 5 The cells were seeded at a density of 100 cells / well in a 24-well plate, with 1 mL of complete culture medium added to each well. The cells were then cultured for 24 hours to allow them to adhere to the plate.

[0051] Take 500 μL each of the sample extract and blank extract, and add 500 μL of complete culture medium containing 1 μg / mL LPS to each. Continue to prepare the solutions in an incubator at 37℃ for 24 h. After the incubation, centrifuge and collect the supernatant. Use an ELISA kit to determine the concentrations of TNF-α and IL-6 in the supernatant.

[0052] Table 5 Results of in vitro anti-inflammatory efficacy test

[0053] The results showed that the TNF-α concentration in the sample group was reduced by 85% and the IL-6 concentration was reduced by 78% compared with the control group, proving that the sample of the present invention can effectively inhibit the release of inflammatory factors and produce a good anti-inflammatory effect.

[0054] 5. Antibacterial performance test 5.1 A 1.0 cm section of the mineralized implantation line from Example 1 was taken, sterilized with 75% ethanol, and rinsed three times with sterile PBS. It was then placed in a sterile petri dish for later use as the experimental group. Simultaneously, a standard PPDO implantation line was treated in the same manner to serve as the blank group. Control group 1 was prepared using the sample from Comparative Example 1, and control group 2 was prepared using the zinc-free mineralization solution from Comparative Example 2. Staphylococcus aureus was inoculated into petri dishes and cultured with shaking at 37°C for 18-24 hours. After incubation, the bacterial suspension was diluted with PBS buffer to a concentration of approximately 1.0 × 10⁻⁶. 5 – 3.0 × 10 5 Working bacterial suspension at CFU / mL.

[0055] Take 40 μL of working bacterial suspension and evenly drop it onto the entire surface of the experimental and control groups, then immediately cover with a sterile polyethylene film and incubate at 37°C with shaking for 24 hours. After the incubation, wash out the bacteria and count the viable cells.

[0056] Table 6. Antibacterial performance test results

[0057] The results showed that after 24 hours, the number of viable bacteria in both Comparative Example 2 and the control group increased by approximately one order of magnitude compared to the initial inoculum (from 10). 4 Increased to 10 5 (CFU / sample), indicating that the bacteria grew and multiplied normally under the experimental conditions. In contrast, the antibacterial rates against Staphylococcus aureus in Example 1 and Comparative Example 1 reached 99.95% and 98.51%, respectively, with the viable bacterial count reduced by three orders of magnitude. This demonstrates that the zinc-containing mineralized coating embedded line of the present invention has excellent antibacterial properties, which can be attributed to the sustained release of Zn²⁺. Zn²⁺ can disrupt the integrity of bacterial cell membranes, interfere with their enzyme systems, and induce the production of reactive oxygen species, thereby killing or inhibiting bacterial growth.

[0058] 5.2 Simultaneously, samples from Example 1 and Comparative Example 1 were placed in 50 mL of SBF simulated body fluid and kept at 37°C. At 1, 3, 6, 21, 24, 48, and 72 hours, 2 mL of the solution was transferred for zinc content detection. Subsequently, 2 mL of SBF simulated body fluid was added to maintain a constant volume. The zinc content of the samples was determined using ICP-MS.

[0059] Table 7: Results of Zn²⁺ Release Kinetics Measurement

[0060] The results showed a statistically significant difference in the Zn²⁺ release kinetics between the two groups of samples (P < 0.05). The release from the sample in Example 1 was more gradual, controllable, and sustained. The PDA layer itself is dense and firmly bonded to the substrate. The Zn-HA coating grown after modification may have a more ordered and tightly bound crystal structure, slowing down the dissolution rate of the coating and the diffusion rate of ions. The catechol and amino functional groups abundant in PDA may have a certain coordination effect on Zn²⁺, playing a role in sustained release and achieving regulation of Zn²⁺ release.

[0061] The method for preparing mineralized facial implant threads provided by this invention achieves technical effects not simply by summing the effects of each individual step, but through multi-level synergistic effects between steps S1 (physical etching), S2 (PDA adsorption), S3 (Zn-HA mineralization), and S4 (intelligent drug grafting). The following analysis, based on specific experimental data, examines these synergistic effects layer by layer: 1. The “anchoring-adhesion” synergy of S1 (physical etching) and S2 (PDA adsorption) lays a solid coating substrate.

[0062] Mechanism of action: The weak acid etching in step S1 creates a micro-rough structure (physical anchoring points) on the surface of the linear material, but this alone is insufficient to guarantee the uniformity and strong adhesion of the subsequent inorganic coating. The PDA molecules introduced in step S2 have strong adhesive properties, allowing them to fully wet and firmly adhere to these rough surfaces. More importantly, the abundant functional groups (catechol, amino groups) in PDA provide strong chemical adhesion and uniform ion adsorption sites.

[0063] Validation of synergistic effect: Table 2 (Nano-scratch test): The critical load of the coating in the "Invention Group" (Example 1), which underwent the complete S1+S2+S3 steps, was 25.3 mN; while the critical load of the "Comparative Example 1," which skipped S1+S2 and directly performed S3 mineralization, was only 8.5 mN. The former is about three times that of the latter. This directly proves that the synergistic effect of "mechanical anchoring created by physical etching" and "chemical adhesion provided by PDA" is the key to obtaining ultra-high coating adhesion. The absence of any one step would significantly reduce the bonding strength.

[0064] Table 1 (Ultrasonic Residue Rate): The samples treated with S1+S2 synergistic process all had a coating residue rate of >98% after ultrasonic treatment, further confirming the interfacial strength brought about by this synergistic effect.

[0065] 2. The "active substrate" provided by S1 and S2, together with the "guided growth" of S3 (Zn-HA mineralization), synergistically generate a mineralized layer with both strong binding and functionality. Mechanism of action: The S1+S2 steps not only enhance the bonding force, but the PDA formed by them also modifies the rough surface, providing a large number of uniform heterogeneous nucleation sites for the mineralization of the S3 step, guiding the Zn-HA crystals to grow in an orderly and dense manner, rather than being randomly deposited on a smooth surface.

[0066] Validation of synergistic effect: Table 7 (Zn²⁺ Release Kinetics): Example 1 (via S1+S2+S3) showed a gradual and sustained release of Zn²⁺ (225.4 μg / g released over 72 hours), while Comparative Example 1 (S3 only) showed a faster release (278.5 μg / g released over 72 hours). This indicates that the Zn-HA coating grown on the active substrate synergistically constructed via S1+S2 has a more ordered crystal structure and tighter binding. The PDA layer may have a coordination and sustained-release effect on Zn²⁺, achieving a synergy between "strong binding" and "controlled release".

[0067] Table 6 (Antibacterial Performance): Both Example 1 and Comparative Example 1 have high antibacterial rates (>98.5%) due to the presence of Zn²⁺. However, based on the data in Table 7, Example 1 achieves a more gradual ion release and lower potential cytotoxicity risk while maintaining high antibacterial efficiency through synergistic effects, demonstrating the synergy between "function" and "safety".

[0068] 3. The synergistic effect of "static protection-dynamic response" between the "Zn-HA mineralization layer" generated by S3 and the "intelligent drug system" grafted by S4. Mechanism of action: The Zn-HA coating formed in step S3 provides basic, sustained antimicrobial protection and bioactivity (static protection). The enzyme-sensitive drug system covalently grafted in step S4 acts as a precise "inflammation sensor" and "drug switch" (dynamic response). The two form a gradient functional layer in space and combine long-term protection with on-demand intervention in time.

[0069] Validation of synergistic effect: Table 4 (Drug Release Kinetics): In an environment without the inflammatory enzyme (MMP-9), the cumulative drug release rate after 120 hours was only 5.9%, demonstrating that the S4 covalent grafting strategy achieved long-term drug loading and avoided burst release. In an inflammatory environment, the drug release reached 78.5% after 72 hours, exhibiting a rapid response. This reflects the synergy between "robust loading" (S4 grafting technology) and "intelligent response" (enzyme sequence design), overcoming the shortcomings of physical drug loading, such as burst release and inability to target specific targets.

[0070] Table 5 (Anti-inflammatory effect): Under simulated inflammatory conditions, the extract of the present invention significantly reduced the levels of inflammatory factors TNF-α and IL-6 (by approximately 85% and 78%, respectively). This verifies that when the S3 mineralization layer is present, the drug system of S4 can be effectively triggered and exert a powerful anti-inflammatory effect, and the two work synergistically to effectively regulate the implantation microenvironment.

[0071] 4. Integrating all steps to achieve a synergistic leap in "mechanical performance-biological integration". Mechanism of action: The ultimate manifestation of the aforementioned multi-level synergy is that the implanted thread as a whole is upgraded from "mechanical gripping by barbs" to "bone-like integration achieved through bioactive coating".

[0072] Validation of synergistic effect: Table 3 (Resistance to Displacement): The maximum pull-out force of Example 1 (0.85 N) is much higher than that of Comparative Example 1 (0.32 N), and a large amount of tissue residue is left upon pull-out. This directly demonstrates that it is due to the step-by-step synergy of steps S1-S4 that a composite functional coating capable of strong biocompatibility with soft tissue is ultimately formed on the surface of the implanted thread. This bonding strength far exceeds the effect of simple physical friction or a single biological coating.

[0073] in conclusion: The inventiveness of this invention lies not only in the superposition of steps, but also in revealing the following clear synergistic path: S1 and S2 work together to solve the fundamental problem of weak adhesion of functional coatings on flexible polymer substrates; based on this, S3 works together to guide the growth of a dense and functionally controllable Zn-HA active layer; the S3 layer then works together with the S4 system to construct an integrated intelligent response system of "antibacterial-monitoring-anti-inflammatory". Ultimately, the technical synergy of all steps translates into a synergistic improvement in product performance, namely, the unity of high coating adhesion, excellent antibacterial properties, precise anti-inflammatory properties, and excellent tissue integration. Experimental data (Tables 1-7) fully and mutually corroborately demonstrate the existence of the above synergistic effect and the significant technological progress it brings. Therefore, the preparation method for which this invention seeks protection is an indivisible and complete technical solution that produces synergistic effects.

Claims

1. A method for preparing mineralized facial implant threads, characterized in that, Includes the following steps: S1. Microscopic physical etching: The polymer embedded wire is immersed in a weak oxidizing mixed acid solution and treated at 25-40°C for 1-10 minutes to form a uniform micro-pit structure on the surface. S2, Polydopamine adsorption: The etched embedded wires are immersed in Tris-HCl buffer solution containing polydopamine and shaken at 25-37°C for 6-12 hours to form a PDA film. S3. Zinc-doped biomimetic mineralization: PDA-modified embedded wires are immersed in a mineralization solution containing zinc ions and allowed to stand at 35-40°C for 3-5 days to form a zinc-doped hydroxyapatite coating. S4. Surface chemical grafting: After amination of the mineralized implanted wire surface, it is covalently grafted with an enzyme-sensitive drug conjugate through a click chemical reaction.

2. The preparation method according to claim 1, characterized in that, The weak oxidizing mixed acid solution mentioned in step S1 is prepared by mixing concentrated hydrochloric acid and hydrogen peroxide in a volume ratio of 3:1 to 7:

1.

3. The preparation method according to claim 1, characterized in that, The concentration of polydopamine in the buffer solution in step S2 is 1~3 mg / mL.

4. The preparation method according to claim 1, characterized in that, The concentration of calcium ions in the mineralization solution described in step S3 is 7–9 mmol / L, the concentration of hydrogen phosphate is 1–5 mmol / L, and the concentration of zinc ions is 1–5 mmol / L.

5. The preparation method according to claim 1, characterized in that, The enzyme-sensitive drug conjugate described in step S4 comprises: a thiol group for surface immobilization, a polypeptide chain GPLGVRGK that can be specifically cleaved by the MMP-9 enzyme, and the anti-inflammatory drug dexamethasone.

6. The preparation method according to claim 5, characterized in that, The polypeptide chain forms a drug conjugate by conjugating its lysine-terminal amino group with the hydroxyl group of dexamethasone.

7. The preparation method according to claim 1, characterized in that, It also includes step S5: cleaning and freeze-drying the grafted implantation wire, and then sterilizing it by electron beam irradiation.

8. A mineralized facial implant thread prepared by the method described in any one of claims 1 to 7.

9. The mineralized facial implant thread according to claim 8, characterized in that, Its cross-section, from the inside out, includes: a polymer matrix, a nano-roughened interface layer, a polydopamine intermediate layer, a zinc-doped hydroxyapatite mineralization layer, and a covalently grafted enzyme-sensitive drug conjugate layer.

10. The mineralized facial implant thread according to claim 9, characterized in that, The polymer matrix is ​​poly(p-dioxanone).

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