A suture-free biological amniotic membrane based on a dynamic softening polycarbonate composite ring and a preparation method thereof

Abstract

The application discloses a kind of based on dynamic softening polycarbonate composite ring's free suture biological amniotic membrane and preparation method thereof.The based on dynamic softening polycarbonate composite ring's free suture biological amniotic membrane includes the amniotic membrane tissue piece of decellularization processing and the modified polycarbonate composite ring for fixing the amniotic membrane tissue piece;The modified polycarbonate composite ring includes polycarbonate continuous phase and the dispersed phase of intelligent polymer in it, and the intelligent polymer is PLGA-PEG-PLGA tri-block copolymer.The application is by specially-made PLGA-PEG-PLGA intelligent polymer and gives modified PC composite ring dynamic modulus adjustable characteristics.After the composite ring is implanted in eye, under the action of body temperature and tear, its contact surface modulus can be reduced by 40%-68% within 24 hours, realize from "surgical rigidity" to "in situ soft" adaptive change.This fundamentally greatly reduces the mechanical friction with cornea / conjunctiva, relieves the strong foreign body sensation, pain and irritation symptom of patient after operation.

Description

Technical Field

[0001] This invention relates to the field of biomedical materials and tissue engineering, and further to a sutureless biological amnion based on a dynamically softened polycarbonate composite ring and its preparation method. Background Technology

[0002] The amniotic membrane, the innermost thin membrane of the placenta, is a natural biomaterial with low immunogenicity, anti-inflammatory, anti-fibrotic, anti-angiogenic properties, and the ability to promote epithelial cell migration and differentiation. It is widely used in ophthalmology to repair corneal and conjunctival defects and promote ocular surface reconstruction. Currently, routine amniotic membrane transplantation surgery typically involves covering the wound with an amniotic membrane flap and then suturing it to the surrounding sclera or healthy corneal / conjunctival tissue using sutures (usually 10-0 nylon sutures).

[0003] While effective, this suturing and fixation method has significant drawbacks: First, the procedure is complex and time-consuming, especially for large or irregular wounds, requiring precise suturing techniques and prolonging the operation. Second, the suturing itself causes iatrogenic secondary injury; needle puncture can lead to bleeding, increase the risk of infection, and may trigger a more severe inflammatory response. Third, postoperative discomfort is intense; the suture knots and threads continuously rub against the ocular surface, causing significant foreign body sensation, pain, photophobia, tearing, and other symptoms, severely impacting the quality of life during the postoperative recovery period. Finally, there is a risk to the reliability of fixation; the sutures may loosen as tissue edema subsides or break due to the patient rubbing their eyes, leading to amniotic membrane displacement or detachment, and causing surgical failure.

[0004] To avoid suturing issues, existing techniques attempt to use bio-adhesives (such as fibrin glue) or rigid supports for fixation. However, bio-adhesives often lack sufficient adhesive strength in the moist ocular surface environment, and their degradation products may affect the healing microenvironment. While support rings or contact lenses made of rigid materials such as polymethyl methacrylate (PMMA) provide physical support, their hardness and poor oxygen permeability can severely compress the cornea with prolonged wear, hindering tear circulation and oxygen exchange, leading to corneal edema, neovascularization, and even ulceration, causing significant foreign body sensation and pain for patients. Silicone is relatively soft, but its mechanical support is weak, resulting in insufficient stability for fixing the amniotic membrane, and its hydrophobic surface has poor biocompatibility with ocular tissues.

[0005] Therefore, current technology lacks an amniotic membrane transplantation solution that can simultaneously meet the following requirements: 1) providing reliable and easy-to-operate sutureless fixation; 2) the fixation device itself has excellent biocompatibility; 3) minimizing long-term foreign body sensation and mechanical irritation on the ocular surface postoperatively; and 4) not interfering with the normal physiological environment of the ocular surface (such as oxygen permeability and tear exchange). The core challenge lies in the fact that the fixation device needs sufficient initial rigidity and structural strength to support the surgical procedure and ensure amniotic membrane stability, while simultaneously achieving mechanical property matching with the soft, mechanically sensitive ocular tissues (cornea, conjunctiva) after implantation to avoid long-term pressure and friction. Summary of the Invention

[0006] In order to overcome one of the technical problems existing in the prior art, the present invention provides a sutureless biological amnion based on a dynamically softened polycarbonate composite ring and its preparation method.

[0007] The technical solution of the present invention is as follows: A sutureless biological amniotic membrane based on a dynamically softened polycarbonate composite ring, comprising a decellularized amniotic tissue sheet and a modified polycarbonate composite ring for fixing the amniotic tissue sheet; The modified polycarbonate composite ring comprises a continuous polycarbonate phase and a smart polymer dispersed therein, wherein the smart polymer is a PLGA-PEG-PLGA triblock copolymer.

[0008] Preferably, in the PLGA-PEG-PLGA triblock copolymer, the number average molecular weight of the PEG (polyethylene glycol) segments is 1500-3000 Da.

[0009] Preferably, in the PLGA-PEG-PLGA triblock copolymer, the molar ratio of LA (lactic acid) to GA (glycolic acid) in the PLGA (polylactic acid-glycolic acid copolymer) segment is (70:30) to (80:20).

[0010] Preferably, the mass percentage of the PLGA-PEG-PLGA triblock copolymer in the modified polycarbonate composite ring is 5% to 30%.

[0011] Preferably, the mass percentage of the PLGA-PEG-PLGA triblock copolymer in the modified polycarbonate composite ring is 8%, 15%, or 25%.

[0012] Preferably, the PLGA-PEG-PLGA triblock copolymer is prepared by the following method: under anhydrous and oxygen-free conditions, using stannous octoate as a catalyst, lactide (LA), glycolide (GA) and hydroxyl-terminated polyethylene glycol (HO-PEG-OH) undergo ring-opening polymerization at a reaction temperature of 120-140℃ for 8-24 hours; after the reaction, it is dissolved in an organic solvent, precipitated in excess cold alcohol, washed, and dried to obtain purified PLGA-PEG-PLGA triblock copolymer.

[0013] Preferably, the modified polycarbonate composite ring is fixed to the amniotic tissue sheet by physical clamping or by biodegradable suture fixation.

[0014] The above-mentioned method for preparing the sutureless biological amnion based on dynamically softened polycarbonate composite rings includes the following steps: S1. Amniotic membrane pretreatment: Amniotic membrane tissue is obtained, decellularized and cleaned, cut, and terminally sterilized to obtain amniotic membrane tissue slices; S2. Preparation of modified polycarbonate composite ring: Dried polycarbonate and PLGA-PEG-PLGA triblock copolymer are melt-blended in a twin-screw extruder at 250℃-270℃ and granulated; the resulting composite material granules are dried and injection molded at a mold temperature of 80℃-100℃ to obtain the modified polycarbonate composite ring; S3. Composite assembly: Under aseptic conditions, the amniotic membrane tissue slices obtained in step S1 are fixed onto the modified polycarbonate composite ring obtained in step S2 by physical clamping or suturing to obtain the sutureless biological amniotic membrane.

[0015] The above-mentioned application of the sutureless biological amniotic membrane based on dynamically softened polycarbonate composite rings in the preparation of medical devices for ocular surface wound repair.

[0016] Preferably, the ocular surface wound includes corneal defects, wounds after pterygium excision, and ocular surface burns or chemical wounds.

[0017] Beneficial Effects: This invention provides a novel sutureless biological amniotic membrane based on a dynamically softening polycarbonate composite ring. The modified PC composite ring is endowed with adjustable dynamic modulus through a specially formulated PLGA-PEG-PLGA smart polymer. After implantation, the contact surface modulus of this composite ring decreases by 40%-68% within 24 hours under the influence of body temperature and tear film, achieving an adaptive transition from "surgical rigidity" to "in-situ softness." This fundamentally and significantly reduces mechanical friction with the cornea / conjunctiva, alleviating postoperative symptoms such as intense foreign body sensation, pain, and irritation. Animal experiments indirectly confirm its effectiveness in reducing postoperative irritation and promoting comfortable healing.

[0018] The sutureless biological amniotic membrane based on a dynamically softened polycarbonate composite ring described in this invention provides a stable physical fixation for the amniotic membrane through a precise ring structure design (clamping or suturing), completely avoiding the risks of loosening and detachment associated with traditional suture fixation. The product is pre-assembled and ready to use, greatly simplifying surgical procedures, shortening surgical time, and reducing reliance on the surgeon's suturing skills.

[0019] The sutureless biological amniotic membrane based on dynamically softened polycarbonate composite rings described in this invention exhibits significantly lower pH variations (0.3-0.8) in its extract compared to the standard limit (1.5); lower heavy metal content (4.2-5.1 μg / g) compared to the standard limit (10 μg / g); a grade 1 cytotoxicity test result; and a high relative growth rate (RGR) of 88%-92%. Furthermore, both pyrogen and eye irritation tests were negative. These data fully demonstrate the material's excellent biocompatibility and safety.

[0020] The sutureless biological amniotic membrane based on dynamically softened polycarbonate composite rings described in this invention exhibits a wide range of overall tensile strength, from 6.95 MPa to 28.36 MPa, providing suitable mechanical support for ocular surface wounds of varying severity. Simultaneously, it retains the inherent bioactivity of the amniotic membrane, effectively promoting epithelial cell migration, inhibiting inflammation and fibrosis, and animal experiments have shown that it can achieve complete wound healing.

[0021] The sutureless biological amniotic membrane based on dynamically softened polycarbonate composite rings described in this invention can be widely used for wound covering after pterygium excision, repair of corneal ulcer perforation, repair of ocular surface chemical or thermal burns, reconstruction after ocular surface tumor resection, and other ocular diseases, and has great clinical application potential and market value. Detailed Implementation

[0022] The following embodiments provide a further detailed explanation of the present invention, but the embodiments do not limit the scope of protection of the present invention.

[0023] Synthesis Example 1: Preparation of PLGA-PEG-PLGA (LA:GA=75:25, PEG Mn=2000) In a glove box filled with high-purity nitrogen, 4.00 g (2.00 mmol) of dehydrated HO-PEG2000-OH (number average molecular weight 2000 Da), 4.32 g (30.0 mmol) of lactide (LA), and 1.16 g (10.0 mmol) of glycolide (GA) were added to a 100 mL Schlenk flask that had been baked and dehydrated. The calculated LA / GA molar ratio was 75 / 25, and the molar ratio of total monomer (LA+GA) to initiator (PEG) was 20:1. 20 mL of anhydrous xylene was added, and the mixture was stirred until partially dissolved. Then, 0.1 mL of a toluene solution of stannous octoate (0.1 mol / L, containing 0.01 mmol of Sn(Oct)₂) was added using a microsyringe. The flask was sealed, removed from the glove box, connected to a vacuum / nitrogen circulation system, evacuated, and then purged with nitrogen. This process was repeated three times. Under nitrogen protection, the reaction flask was placed in an oil bath at 130°C and the reaction was magnetically stirred for 12 hours. After the reaction was completed, the mixture was cooled to room temperature, and the viscous reactant was dissolved in 40 mL of dichloromethane. Then, under vigorous stirring, the solution was added dropwise to 400 mL of ice-cold anhydrous diethyl ether to precipitate the product. The white solid was collected by filtration, dissolved again in 20 mL of dichloromethane, and then added dropwise to 200 mL of ice-cold methanol for a second precipitation to purify the product. After filtration, the resulting white flocculent solid was dried in a vacuum drying oven at 35°C for 48 hours to constant weight, yielding approximately 7.8 g of product, with a yield of approximately 85%.

[0024] Synthesis Example 2: Preparation of PLGA-PEG-PLGA (LA:GA=80:20, PEG Mn=1500) Referring to Synthesis Example 1, HO-PEG1500-OH (3.00 g, 2.00 mmol), LA (4.61 g, 32.0 mmol), and GA (0.93 g, 8.0 mmol) were used, with the LA / GA molar ratio set at 80 / 20 and the monomer / initiator molar ratio at 20:1. The reaction conditions were the same.

[0025] Synthesis Example 3: Preparation of PLGA-PEG-PLGA (LA:GA=70:30, PEG Mn=3000) Referring to Synthesis Example 1, HO-PEG3000-OH (6.00 g, 2.00 mmol), LA (3.60 g, 25.0 mmol), and GA (1.74 g, 15.0 mmol) were used, with the LA / GA molar ratio set at 70 / 30 and the monomer / initiator molar ratio at 20:1. The reaction conditions were the same.

[0026] Product Example 1: Preparation of a sutureless biological amnion based on dynamically softened polycarbonate composite rings Formulation: 92 wt% medical grade polycarbonate (PC), 8 wt% PLGA-PEG-PLGA prepared in the above synthesis example 1.

[0027] Preparation method: (1) After vacuum drying the two raw materials at 80°C for 12 hours, they were added to a co-rotating twin-screw extruder and melt-blended and extruded at 260°C. The resulting composite material granules were dried at 80°C for 6 hours, and then injection molded into upper and lower rings for clamping and fixing using a precision injection molding machine at a mold temperature of 90°C and an injection pressure of 90 MPa.

[0028] (2) Obtain human amniotic membrane, remove cells by trypsin / EDTA shaking, wash thoroughly with PBS, cut into 14 mm diameter discs, lay flat on a sterile carrier, and sterilize by γ-ray irradiation using a cobalt-60 source at a dose of 25 kGy.

[0029] (3) In an ISO Class 5 clean bench, place the sterile amniotic membrane in the bearing groove of the lower ring, cover it with the upper ring, apply appropriate pressure until the buckle mechanism is locked, and complete the aseptic assembly.

[0030] Key performance indicator tests: The composite ring was immersed in simulated tear fluid (pH=7.4) at 37℃, and the change in its surface compressive modulus was tested using a dynamic mechanical analyzer. At 0 hours (dry), the modulus was 1120±45 MPa. After 24 hours of immersion, the modulus decreased to 650±30 MPa, a decrease of 42.0%. The dynamic coefficient of friction after 24 hours was measured to be 0.29±0.02 using a friction testing machine (with fresh porcine corneas as the mating pair).

[0031] Tensile strength: The tensile strength of the final composite product was tested according to the above method, and the result was 15.01 MPa.

[0032] pH: The pH value was determined according to the pH determination method in General Chapter 0631 of Part IV of the Pharmacopoeia of the People's Republic of China (2025 Edition). The pH value difference between the test solution and the blank control solution was 0.8, which meets the requirement of not exceeding 1.5.

[0033] Heavy metal content: determined according to the second method of the General Chapter 0821 Heavy Metals Test Method in Part IV of the Pharmacopoeia of the People's Republic of China (2025 Edition), the result was 4.2 μg / g, which meets the requirement of not more than 10 μg / g.

[0034] Cytotoxicity assay: The extract was prepared according to GB / T 16886.12-2023 and tested using the MTT assay. The test solution was added to a 96-well plate that had been confluent with L929 cells. After culturing for 24 hours, the cells showed good morphology. The relative growth rate (RGR) measured by the MTT assay was 92%, and the cytotoxicity grade was 1, which meets the requirement of not exceeding grade 2.

[0035] Pyrogen testing: The pyrogen test was conducted according to the 2025 edition of the Pharmacopoeia of the People's Republic of China, Part IV, 1142. The highest temperature increase in the three rabbits was less than 0.6℃, and the total temperature increase was less than 1.3℃, so they were judged to be pyrogen-free.

[0036] No irritation: Rabbit eye irritation test was conducted according to Appendix D of GB / T 16886.23-2023. The results were observed at 1h, 24h, 48h and 72h after the test liquid was instilled into the eyes. There was no eye irritation reaction compared with the control side.

[0037] Product Example 2: Preparation of a sutureless biological amnion based on dynamically softened polycarbonate composite rings Formulation: 85 wt% medical grade polycarbonate (PC), 15 wt% PLGA-PEG-PLGA prepared in the above synthesis example 2.

[0038] The preparation method is the same as in Product Example 1.

[0039] Key performance indicators: After immersion in simulated tear fluid at 37℃ for 24 hours, the surface compressive modulus decreased from 980±40 MPa to 410±20 MPa, a decrease of 58.2%. The dynamic coefficient of friction after 24 hours was 0.21±0.02.

[0040] Tensile strength: 22.87 MPa. pH difference: 0.5. Heavy metal content: 4.8 μg / g. Cytotoxicity: RGR 90%, grade 1. Pyrogen: No pyrogen reaction. Eye irritation: No eye irritation.

[0041] Product Example 3: Preparation of a sutureless biological amnion based on dynamically softened polycarbonate composite rings Formulation: 75 wt% medical grade polycarbonate (PC), 25 wt% PLGA-PEG-PLGA prepared in the above synthesis example 3.

[0042] The preparation method is the same as in Product Example 1.

[0043] Key performance indicators: After immersion in simulated tear fluid at 37℃ for 24 hours, the surface compressive modulus decreased from 750±35 MPa to 240±15 MPa, a decrease of 68.0%. The dynamic coefficient of friction was as low as 0.15±0.01 after 24 hours.

[0044] Tensile strength: 28.36 MPa. pH difference: 0.3. Heavy metal content: 5.1 μg / g. Cytotoxicity: RGR 88%, grade 1. Pyrogen: No pyrogen reaction. Eye irritation: No eye irritation.

Claims

1. A sutureless biological amnion based on a dynamically softened polycarbonate composite ring, characterized in that, The amniotic tissue sheet includes a decellularized amniotic tissue sheet and a modified polycarbonate composite ring for fixing the amniotic tissue sheet; The modified polycarbonate composite ring comprises a continuous polycarbonate phase and a smart polymer dispersed therein, wherein the smart polymer is a PLGA-PEG-PLGA triblock copolymer.

2. The sutureless biological amnion based on a dynamically softened polycarbonate composite ring according to claim 1, characterized in that, In the PLGA-PEG-PLGA triblock copolymer, the number average molecular weight of the PEG (polyethylene glycol) segments is 1500-3000 Da.

3. The sutureless biological amnion based on a dynamically softened polycarbonate composite ring according to claim 1, characterized in that, In the PLGA-PEG-PLGA triblock copolymer, the molar ratio of LA (lactic acid) to GA (glycolic acid) in the PLGA (polylactic acid-glycolic acid copolymer) segment is (70:30) to (80:20).

4. The sutureless biological amnion based on a dynamically softened polycarbonate composite ring according to claim 1, characterized in that, The mass percentage of the PLGA-PEG-PLGA triblock copolymer in the modified polycarbonate composite ring is 5% to 30%.

5. The sutureless biological amnion based on a dynamically softened polycarbonate composite ring according to claim 4, characterized in that, The mass percentage of the PLGA-PEG-PLGA triblock copolymer in the modified polycarbonate composite ring is 8%, 15%, or 25%.

6. The sutureless biological amnion based on a dynamically softened polycarbonate composite ring according to claim 1, characterized in that, The PLGA-PEG-PLGA triblock copolymer was prepared by the following method: under anhydrous and oxygen-free conditions, stannous octoate was used as a catalyst to carry out a ring-opening polymerization reaction of lactide (LA), glycolide (GA) and hydroxyl-terminated polyethylene glycol (HO-PEG-OH). The reaction temperature was 120-140℃ and the reaction time was 8-24 hours. After the reaction was completed, the copolymer was dissolved in an organic solvent, precipitated in excess cold alcohol, washed, and dried to obtain the purified PLGA-PEG-PLGA triblock copolymer.

7. The sutureless biological amnion based on a dynamically softened polycarbonate composite ring as described in claim 1, Its features are, The modified polycarbonate composite ring is fixed to the amniotic tissue sheet by physical clamping or by biodegradable suture fixation.

8. The method for preparing the sutureless biological amnion based on dynamically softened polycarbonate composite rings according to any one of claims 1-7, characterized in that, It includes the following steps: S1. Amniotic membrane pretreatment: Amniotic membrane tissue is obtained, decellularized and cleaned, cut, and terminally sterilized to obtain amniotic membrane tissue slices; S2. Preparation of modified polycarbonate composite ring: Dried polycarbonate and PLGA-PEG-PLGA triblock copolymer are melt-blended in a twin-screw extruder at 250℃-270℃ and granulated; the resulting composite material granules are dried and injection molded at a mold temperature of 80℃-100℃ to obtain the modified polycarbonate composite ring; S3. Composite assembly: Under aseptic conditions, the amniotic membrane tissue slices obtained in step S1 are fixed onto the modified polycarbonate composite ring obtained in step S2 by physical clamping or suturing to obtain the sutureless biological amniotic membrane.

9. The use of the sutureless biological amniotic membrane based on dynamically softened polycarbonate composite rings as described in any one of claims 1-7 in the preparation of medical devices for the repair of ocular surface wounds.

10. The application according to claim 9, characterized in that, The ocular surface wounds include corneal defects, wounds after pterygium excision, and ocular surface burns or chemical injuries.