Powder-based Janus double-layer hydrogel for in-situ gelling at anastomotic stoma

Abstract

The invention provides a powder-based Janus double-layer hydrogel capable of forming gel in situ at an anastomotic stoma. The powder-based Janus double-layer hydrogel consists of a powder adhesion layer and a photocuring anti-adhesion layer, and can be formed on the surface of an anastomotic stoma in situ; when the precursor powder particles are hydrated after being in contact with digestive tract mucus, aldehyde groups and amino groups are dissociated, the aldehyde groups and the amino groups are subjected to Schiff base reaction, chemical crosslinking is induced to be formed among the precursor powder particles, and meanwhile, a loose porous structure formed by stacking the precursor powder is fixed and maintained; therefore, a complete, continuous, loose and porous powder adhesion layer hydrogel network is obtained; the photocuring anti-sticking layer is formed by initiating a precursor solution through ultraviolet light, and the precursor solution comprises 15% by mass of poly-zwitterionic macromolecules, 5% by mass of methacrylated biomacromolecules and a phosphate buffer solution of a photoinitiator LAP. According to the present invention, the in-situ gel forming can be performed on the anastomotic stoma surface, and advantages of rapid wet adhesion, good wrapping property, good biocompatibility, corrosion resistance, easy operation and the like are provided.

Description

Technical Field

[0001] The invention relates to the technical field of biomedical macromolecular hydrogels, in particular to a powder-based Janus double-layer hydrogel capable of forming gel in situ at anastomotic sites. Background Art

[0002] Radical surgery is the primary surgical treatment for gastrointestinal diseases such as gastrointestinal tumors, intestinal ischemia, and inflammatory bowel disease. Despite significant advances in surgical techniques and instrumentation over the years, complications such as anastomotic fistula, intestinal obstruction, and infection remain unavoidable after gastrointestinal surgery. Among them, anastomotic fistula is one of the most serious complications after gastrointestinal surgery, and its occurrence is related to the presence or absence of neoadjuvant chemoradiotherapy, surgical duration, anastomotic site location, blood supply, anastomotic technique, anastomotic tension, intestinal pressure, and the patient's physical condition. Following gastric and esophageal surgery, the incidence of anastomotic fistula can reach 10%, and the incidence of colorectal anastomotic fistula ranges from 1.4 to 10%.

[0003] The occurrence of anastomotic leakage not only prolongs hospitalization and increases financial burden, but also increases the incidence of postoperative complications and the risk of reoperation. In mild cases, it can adversely affect patients' long-term survival and quality of life, while in severe cases, it can lead to diffuse peritonitis, shock, and even death. Studies have also shown that the occurrence of anastomotic leakage in rectal cancer is associated with an increased risk of recurrence within 5 years after surgery (13.3% vs 4.6%; P = 0.005).

[0004] Therefore, preventing anastomotic fistula is crucial for gastrointestinal surgery. Currently, the main preventive measures include preoperative mechanical bowel preparation and prophylactic antibiotics, intraoperative prophylactic stoma placement, ensuring anastomotic blood supply, reducing anastomotic tension, and using appropriate staplers. These measures can reduce the incidence of anastomotic fistula to a certain extent, but some procedures are complex, require high surgical skills, increase operative time, and still inevitably carry the risk of anastomotic fistula.

[0005] Current commercially available adjuvants, such as Tachosil or Tisseel, can be applied around the digestive tract and promote healing to some extent. However, due to their lack of adhesive properties and their obstruction by the mucus on the surface of the gastrointestinal tract, they struggle to adhere effectively to and retain on the anastomotic surface, resulting in limited effectiveness in occluding and preventing fistulas. Hydrogel patches, with their wet adhesive properties, can effectively and long-term occlude and treat perforated hollow organs and ruptured, bleeding solid organs, and have the potential to be applied to anastomotic problems. However, digestive tract surgery often results in uneven, complex, and irregular anastomotic surfaces due to different anastomotic methods (e.g., end-to-end, end-to-side, and side-to-side). Pre-prepared biomaterials, such as patches, often fail to thoroughly and completely cover complex digestive anastomoses, resulting in gaps between the material and the anastomotic site and making it difficult to effectively block potential digestive fluid leakage. Furthermore, biomaterial rejection can lead to secondary peritoneal adhesions, further exacerbating the patient's condition, a factor often overlooked in previous approaches.

[0006] Therefore, to address the above problems, it is necessary to develop a Janus hydrogel that can be formed in situ on the surface of the digestive tract, can quickly adhere to the digestive tract and perform its functions, and can prevent anastomotic fistula while avoiding anastomotic leakage and abdominal adhesion caused by foreign body reaction of the material. Summary of the Invention

[0007] In response to the shortcomings of the prior art, the present invention aims to provide a powder-based Janus bilayer hydrogel that forms in situ at the anastomotic site. This powder-based Janus bilayer hydrogel can be formed in situ on the surface of biological tissue, such as the anastomotic site, and exhibits rapid wet adhesion, excellent sealing properties, good biocompatibility, and corrosion resistance. It can effectively prevent anastomotic fistulas and the occurrence of peritoneal adhesions.

[0008] The technical solution of the present invention is as follows: A powder-based Janus double-layer hydrogel that forms gel in situ at the anastomosis. The powder-based Janus double-layer hydrogel consists of two layers: a powder adhesion layer and a light-cured anti-adhesion layer, and can be formed in situ on the anastomotic surface. When the precursor powder particles come into contact with the digestive tract mucus and become hydrated, aldehyde and amino groups are released. Schiff base reactions occur between the aldehyde and amino groups, inducing chemical cross-linking between the precursor powder particles. At the same time, the loose porous structure formed by the accumulation of the precursor powder is fixed and maintained, thereby obtaining a complete, continuous, loose and porous powder adhesion layer hydrogel network. The photocurable anti-sticking layer is formed by a precursor solution initiated by ultraviolet light, wherein the precursor solution contains 15% by mass of polyzwitterionic polymer, 5% by mass of methacrylated biomacromolecule and phosphate buffer solution of photoinitiator LAP.

[0009] The precursor powder of the powder adhesion layer is composed of aldehyde-containing macromolecules and amino-containing macromolecules; the aldehyde-containing macromolecules include one or more of oxidized chondroitin sulfate, oxidized hyaluronic acid and oxidized sodium alginate; the amino-containing macromolecules include one or more of chitosan lactate, polylysine and gelatin.

[0010] The polyzwitterionic polymer of the precursor solution includes one or more of polysulfobetaine, polycarboxybetaine and polyphosphorylcholine; correspondingly, the monomer includes one or more of sulfobetaine methacrylate, carboxybetaine methacrylate and 2-methacryloyloxyethylphosphorylcholine.

[0011] The methacrylated biomacromolecules in the precursor solution include one or more of methacrylated hyaluronic acid, methacrylated gelatin, methacrylated chondroitin sulfate, and methacrylated chitosan.

[0012] The precursor powder of the powder adhesion layer is composed of aldehyde-containing macromolecules and amino-containing macromolecules.

[0013] The powder adhesion layer contains powders of oxidized chondroitin sulfate and chitosan lactate in a mass ratio of 3:7 to 7:3.

[0014] The powder-based Janus double-layer hydrogel that forms gel in situ at the anastomosis comprises the following synthesis steps: 1) Preparation of aldehyde-containing macromolecules: Dissolve chondroitin sulfate, hyaluronic acid, or sodium alginate in deionized water, add sodium periodate solution to oxidize the chondroitin sulfate, dialyze, freeze-dry, and pulverize to obtain a powder of the aldehyde-containing macromolecule; 2) Preparation of a powder adhesion layer hydrogel: Powders of aldehyde-containing macromolecules and amino-containing macromolecules are thoroughly mixed in a mass ratio of 3:7 to 7:3, ground evenly, and applied to the surface of the digestive tract tissue by smearing or spraying. The powder particles absorb water, adhere, and cross-link to quickly form an adhesion layer hydrogel. 3) Preparation of polyzwitterionic polymer: Dissolve the zwitterionic monomer in phosphate buffer solution, add thermal initiator ammonium persulfate and co-initiator tetramethylethylenediamine, allow polymerization to proceed, and obtain the polyzwitterionic polymer after dialysis and freeze-drying. 4) Preparation of methacrylated biomacromolecules: Dissolve hyaluronic acid, gelatin, chondroitin sulfate, or chitosan in deionized water, add methacrylic anhydride dropwise, allow to react fully, dialyze, and freeze-dry to obtain the methacrylated biomacromolecules; 5) Preparation of a photocurable anti-adhesive layer hydrogel: Dissolve the polyzwitterionic polymer and methacrylated biomacromolecule in a phosphate buffer solution at a mass fraction of 15% and 5%, respectively. Add an appropriate amount of initiator LAP to obtain a precursor solution. Spray or apply the precursor solution to the powder adhesion layer and irradiate with 365nm UV light for 30 seconds to several minutes to form a gel.

[0015] Compared with the prior art, the present invention can achieve at least the following beneficial effects: 1. The present invention utilizes the stacking effect, rapid hydration and Schiff base crosslinking mechanism of water-soluble powder particles. The powder particles sprayed onto the surface of the digestive tract destroy the mucus barrier on the surface of the digestive tract through hydration, establishing direct physical and chemical adhesion with the digestive tract, overcoming the difficulty of biological materials in establishing good adhesion to the digestive tract; at the same time, the hydrated powder particles are rapidly cross-linked through the Schiff base reaction of aldehyde and amino groups, thereby forming a powder adhesion layer hydrogel that completely covers and encapsulates the digestive tract in situ; in addition, the loose and porous structure formed by the stacking of powder particles is fixed and maintained under the action of crosslinking, so that the powder adhesion layer hydrogel has a loose and porous structure, which not only provides space for cell adhesion and growth, but also provides a platform for the photocurable anti-adhesion layer to be anchored on the surface of the digestive tract.

[0016] 2. The powder used in the present invention can be evenly sprayed onto the irregularly shaped surface of the digestive tract by spraying or coating, forming a hydrogel coating that completely covers the digestive tract without leaving any gaps and tightly fits. It has the characteristics of adapting to complex shapes and surfaces, and effectively avoids potential cavities for digestive fluid to seep out.

[0017] 3. The present invention uses an in-situ powder-based Janus double-layer hydrogel, whose powder adhesion layer and light-cured anti-sticking layer remain stable in a variety of digestive juices and digestive enzymes, can withstand the corrosion of a variety of digestive juices and digestive enzymes, and effectively prevent peritoneal inflammation caused by the leakage of digestive juices and digestive enzymes.

[0018] 4. The in situ powder-based Janus double-layer hydrogel used in the present invention can prevent anastomotic fistula while avoiding digestive fluid exudation and abdominal adhesion caused by foreign body reaction of the material, and has powerful biomedical functions for practical application in complex abdominal environments. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 The rheological properties of the powder adhesion layers prepared in Examples 1-5.

[0020] Figure 2 The adhesion strength of the powder adhesion layer prepared in Examples 1-5.

[0021] Figure 3a The stability of the powder-based Janus double-layer hydrogel powder adhesion layer in different digestive fluid solutions.

[0022] Figure 3b The stability of powder-based Janus double-layer hydrogel photocurable anti-sticking layer in different digestive fluid solutions.

[0023] Figure 4 The pore structure of powder-based Janus double-layer hydrogel under scanning electron microscope; The scale of the powder adhesion layer is 50 μm, the same as the photocurable anti-adhesion layer; the scale of the double-layer hydrogel is 150 μm.

[0024] Figure 5 The cell compatibility of powder-based Janus bilayer hydrogel. Part a is the CCK-8 data chart of the powder adhesion layer O5C5; Part b is the CCK-8 data chart of the light-cured anti-sticking layer.

[0025] Figure 6 The blood compatibility of powder-based Janus double-layer hydrogel. Part a shows the blood compatibility and hemolysis rate of the light-cured anti-adhesive layer; Part b shows the blood compatibility and hemolysis rate of the powder adhesion layer.

[0026] Figure 7 The powder-based Janus double-layer hydrogel is effective in preventing colorectal anastomotic fistula. Part a is the group without hydrogel; part b is the powder control group containing only the powder adhesion layer; part c is the experimental group of powder-based Janus double-layer hydrogel.

[0027] Figure 8 The effect of powder-based Janus double-layer hydrogel on preventing peritoneal adhesions. Part a is the group without hydrogel; part b is the control group containing only the powder adhesion layer; and part c is the experimental group treated with powder-based Janus double-layer hydrogel.

[0028] Figure 9 The powder-based Janus double-layer hydrogel is non-toxic to multiple organs in mice. The upper part is the control group, and the lower part is the experimental group. DETAILED DESCRIPTION

[0029] The present invention is further described in detail below with reference to specific examples, but the present invention is not limited to the following specific examples.

[0030] In the powder adhesion layer, different aldehyde-containing macromolecules and amino-containing macromolecule powders were mixed in a ratio of 1:1 to obtain Examples 1-9. The gelling effects are shown in Table 1 below.

[0031]

[0032] Preferably, we specifically use Example 1 as an example for illustration. In Examples 2-9, only steps 1) and 4 below are changed. The remaining steps are the same or can be adjusted accordingly by a person skilled in the art. A powder-based Janus double-layer hydrogel is prepared according to the following steps: 1) Synthesis of oxidized chondroitin sulfate: Dissolve 10 g of chondroitin sulfate in 100 mL of deionized water, purging with nitrogen. Once the chondroitin sulfate is fully dissolved, slowly add 40 mL of aqueous sodium periodate solution (0.1 g / mL) dropwise to the solution. Stir continuously in the dark for 6 hours. Then, add 10 mL of ethylene glycol solution and stir for 30 minutes to terminate the reaction. Dialyze against deionized water (molecular weight cutoff 3500 Da) for at least 4 days, changing the deionized water at least twice daily. After dialysis, freeze-dry and powderize to obtain oxidized chondroitin sulfate.

[0033] 2) Synthesis of Methacryloylated Hyaluronic Acid: Dissolve 10 g of hyaluronic acid in 500 mL of phosphate buffer solution. Once fully dissolved, adjust the pH to 8-9. Slowly add 6 mL of methacrylic anhydride dropwise to the solution in an ice-water bath. Remove from the ice-water bath and continue the reaction with constant stirring for 4 hours. Then, dialyze against deionized water (molecular weight cut-off 3500 Da) for at least 4 days, changing the deionized water at least twice daily. After dialysis, freeze-dry to obtain methacryloylated hyaluronic acid.

[0034] 3) Synthesis of polysulfobetaine polymer: Dissolve 10 g of sulfobetaine methacrylate in 50 mL of phosphate buffer, add 20 mg of ammonium persulfate and 100 μL of TEMED, and stir overnight at room temperature. Dialyze against phosphate buffer (molecular weight cutoff 3500 Da) for at least 4 days, changing deionized water at least twice daily. After dialysis, freeze-dry and powder to obtain polysulfobetaine polymer.

[0035] 4) Preparation of powder for the powder adhesion layer: Mix oxidized chondroitin sulfate powder and chitosan lactate powder in a mass ratio of 3:7 to 7:3, grind and mix thoroughly to obtain powder for the powder adhesion layer. For the convenience of the subsequent performance comparison experiment description, the powder prepared when the mass ratio of oxidized chondroitin sulfate to chitosan lactate in the powder is x:y is named as O x C y .

[0036] 5) Prepare a photocurable release layer precursor solution: Dissolve methacrylated hyaluronic acid and polysulfobetaine in phosphate buffer to final concentrations of 5% and 15% by weight, respectively. Add the photoinitiator LAP to a final concentration of 2.5 mg / mL. Store the resulting photocurable release layer precursor solution in a dark place.

[0037] 6) Preparation of a powder-based Janus bilayer hydrogel: The powder for the powder adhesion layer was sprayed onto a moistened mold surface. The powder absorbed water and quickly formed a gel. Subsequently, a photocurable release layer precursor was dropwise added to the surface of the powder adhesion layer. The powder-based Janus bilayer hydrogel was then irradiated with 365nm UV light for 30s-60s.

[0038] 7) In situ formation of a powder-based Janus bilayer hydrogel on biological tissue: The powder of the powder adhesion layer is applied or sprayed onto the surface of the biological tissue. The powder absorbs water, adheres, and crosslinks to form a powder adhesion layer. Subsequently, a photocurable release layer precursor is applied or sprayed onto the surface of the powder adhesion layer. Irradiation with 365nm UV light for 30s-60s results in the in situ formation of the powder-based Janus bilayer hydrogel.

[0039] According to the different proportions of the components in step 5), specific examples 10-14 are obtained as shown in Table 2 below.

[0040] The powder adhesion layers prepared in Examples 1-5 were subjected to performance tests, mainly including the following tests: 1) Storage modulus and loss modulus: Dynamic oscillation tests were performed on hydrogels (20 mm diameter) with powder-coated layers of varying mass ratios using a HAAKE RS6000 rotational rheometer (Thermo Scientific, Germany). A parallel plate fixture (PP20 Ti) was used, with the plate spacing set to 1.0 mm and the test temperature set to 25°C. The strain was set to 1%, and a frequency sweep (0.1–100 Hz) was performed to obtain the storage modulus and loss modulus of the hydrogels at different frequencies ( Figure 1 ).

[0041] 2) Evaluation of adhesion performance: In order to determine the adhesion performance of the powder adhesion layer with different component ratios to biological tissues, a T-type peel strength test was performed. The fresh and moist pig large intestine was cut into strips with a width of 10 mm. The powder was evenly applied to the serosal surface of the fresh and moist pig large intestine. The application area was 20 mm × 10 mm, and the powder thickness was about 1 mm. A 40 mm × 10 mm cloth strip was glued to the surface of the powder gel with 502 glue and waited for 5 minutes. The pig large intestine and the cloth strip were clamped at both ends of the tensile machine fixture at a constant displacement rate of 20 mm / min. The maximum peel strength obtained by the tensile machine was recorded ( Figure 2 ).

[0042] The Janus hydrogel prepared in step 6) was subjected to performance testing. In the powder adhesion layer of different embodiments, the storage modulus of O5C5 ( Figure 1 ) and adhesion strength ( Figure 2 ) is the best, so the powder adhesion layer of the subsequent Janus hydrogel is O5C5.

[0043] 3) Stability of powder-based Janus bilayer hydrogels in digestive fluids: Powder-based adhesive layer hydrogels and photocurable release layer hydrogels of uniform volume and shape were immersed in bile, intestinal fluid (containing trypsin, lipase, and amylase), gastric fluid (containing pepsin), and phosphate buffer solution at room temperature, respectively, and shaken at 60 rpm. The hydrogels were removed at designated time points, surface moisture was removed by blotting, and the hydrogels were weighed. The residual mass percentage was calculated using the following formula: Weight Remaining (%) = (W t - W0) / W0× 100% Among them, W t is the weight at different time points, and W0 is the initial weight of the hydrogel just prepared.

[0044] The powder anti-adhesive layer hydrogel was evaluated to be resistant to erosion by bile and intestinal fluid ( Figure 3a ); The light-cured anti-adhesive layer can withstand the erosion of bile, intestinal fluid and gastric acid ( Figure 3b ). Both showed strong stability in digestive juice.

[0045] 4) Pore structure of powder-based Janus bilayer hydrogel: A powder-based Janus bilayer hydrogel sample was air-dried at room temperature. A scanning electron microscope (SU-3500, HITACHI) was used to observe and photograph the cross-section of the dried powder-based Janus bilayer hydrogel sample.

[0046] After evaluation, the powder-based Janus bilayer hydrogel showed a distinct bilayer structure ( Figure 4 ), where the powder adhesion layer exhibits a loose and porous perforated structure ( Figure 4 ), the photocured anti-adhesive layer showed a dense, non-porous and smooth structure ( Figure 4 ).

[0047] 5) Cytocompatibility of Powder-Based Janus Bilayer Hydrogels: To evaluate the biocompatibility of the Janus hydrogels, the CCK-8 assay was used to test the cytocompatibility of the extracts from the powder adhesion layer and the photocurable release layer of the powder-based Janus bilayer hydrogels. After UV sterilization, 1 g of the powder adhesion layer hydrogel and 1 g of the photocurable release layer hydrogel, respectively, were weighed and immersed in 10 mL of complete culture medium. The extracts were shaken at 60 rpm at 37°C for 24 hours and filtered through a 0.22 μm filter to obtain the extracts from the powder adhesion layer and the photocurable release layer. NIH 3T3 mouse fibroblasts were cultured with the original culture medium, the extracts from the powder adhesion layer, and the extracts from the photocurable release layer, respectively. NIH 3T3 cells were cultured in a CO2 incubator at 37°C for 1, 3, and 5 days. Cell viability was assessed using the CCK-8 assay at fixed time points at 1, 3, and 5 days. The cell viability (Relative Cell Viability%) of the two layers of hydrogels relative to the control group was calculated at 1, 3, and 5 days respectively according to the instructions.

[0048] The powder adhesion layer of Janus hydrogel ( Figure 5 Part a) and a light-cured release layer ( Figure 5 Part b) showed good cell compatibility.

[0049] 6) Hemocompatibility of the powder-based Janus bilayer hydrogel: First, ICR male mice were anesthetized with gas, and the beard and hair around the eyeballs were shaved. Blood was collected from the mice using the ocular bleeding method into heparinized EP tubes. The erythrocyte pellet was obtained by low-speed centrifugation. After repeated washing, an erythrocyte suspension (5%) was obtained and stored at room temperature. Deionized water was added to the positive control group; phosphate buffer was added to the negative control group; and different concentrations of powder-based Janus bilayer hydrogel were added to the experimental groups. The cells were incubated at 37°C for 1.5 hours. After low-speed centrifugation, the appearance was observed and photographed. 100 μL of the supernatant was aspirated and the absorbance was measured at 540 nm using a microplate reader (TECAN SPARK) to calculate the hemolysis rate.

[0050] After evaluation, the powder adhesion layer and light-cured anti-adhesion layer of Janus hydrogel will not cause hemolysis of red blood cells and have good blood compatibility ( Figure 6 ).

[0051] 7) Evaluation of the powder-based Janus bilayer hydrogel for preventing anastomotic leakage: First, a mouse model of rectal anastomotic leakage was established. ICR mice were fasted for one day and anesthetized with isoflurane. The abdominal hair was shaved, the skin exposed, and disinfected with alcohol. A 1-cm incision was made along the midline of the lower abdomen. The skin and peritoneum were cut layer by layer, and the rectum was exposed using surgical instruments. A transverse incision circumferentially extending halfway around the rectum was made 2 cm from the anus. The rectum was then sutured and tied three times using Prolene 8-0 surgical sutures. The untreated group underwent sutures only, the powder control group underwent in situ formation of the powder adhesion layer hydrogel, and the experimental group underwent in situ formation of the powder-based Janus bilayer hydrogel. Methylene blue solution was injected into the rectal lumen via the anus using a syringe and observed for leakage.

[0052] After evaluation, no treatment group ( Figure 7 Part a) has obvious leakage; the powder adhesion layer ( Figure 7 Part b) and powder-based Janus bilayer hydrogel ( Figure 7 Part c) can prevent leakage and anastomotic fistula.

[0053] 8) Evaluation of the powder-based Janus bilayer hydrogel for preventing peritoneal adhesions: First, a mouse colorectal anastomotic adhesion model was established. ICR mice were selected and anesthetized with isoflurane after a one-day fast. Abdominal hair was shaved with a hair clipper, and the skin was exposed and disinfected with alcohol. A 1-cm incision was made along the midline of the abdomen. The skin and peritoneum were cut, and the cecum was removed using surgical instruments. A transverse incision was made in the colon, 1 cm from the cecum, extending halfway around the colon. Three sutures were then performed and knotted using Prolene 8-0 surgical sutures. The untreated group underwent suture alone, the powder control group underwent in situ formation of the powder adhesion layer hydrogel, and the experimental group underwent in situ formation of the powder-based Janus bilayer hydrogel. The peritoneum and skin were sutured layer by layer, and the abdomen was closed. Seven days after surgery, the mice were sacrificed and observed for adhesions.

[0054] After evaluation, no treatment group ( Figure 8 of part a) and powder control group ( Figure 8 Part b) Obvious abdominal adhesion occurred at the anastomosis site; the powder-based Janus double-layer hydrogel group ( Figure 8 Part c) No abdominal adhesions occurred.

[0055] 9) Nontoxicity of the powder-based Janus bilayer hydrogel to multiple organs in mice: First, a mouse colorectal anastomotic adhesion model was established according to the method in 6). The anastomotic stoma of the control group was simply sutured without treatment, while the powder-based Janus bilayer hydrogel was in situ molded at the anastomotic stoma in the experimental group. On the 14th day after surgery, the mice were sacrificed, and the heart, liver, spleen, kidney, and lung were removed and fixed in formalin. The organs were then embedded in paraffin, sectioned, and stained with H&E to obtain H&E sections.

[0056] After evaluation, compared with the control group ( Figure 9 The powder-based Janus bilayer hydrogel group ( Figure 9 The lower part of the body) has no obvious organ toxicity to the heart, liver, spleen, kidney and lung.

[0057] Based on the above tests, we have developed a powder-based Janus bilayer hydrogel that forms in situ at the anastomotic site. This powder-based Janus bilayer hydrogel can be formed in situ on the anastomotic site and other digestive tract surfaces. It features in-situ formation, rapid wet adhesion, rupture resistance, excellent biocompatibility, and corrosion resistance. It effectively prevents anastomotic fistulas and intraperitoneal adhesions, demonstrating its robust biomedical capabilities for practical application within the complex intraperitoneal environment.

[0058] The above-described embodiments merely illustrate several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention. It should be noted that a person skilled in the art would be able to make numerous modifications and improvements without departing from the spirit of the present invention, all of which fall within the scope of protection of the present invention. Therefore, the scope of protection of the present invention shall be determined by the appended claims.

Claims

1. A powder-based Janus bilayer hydrogel that forms an in situ gel at the anastomosis, characterized in that: The powder-based Janus double-layer hydrogel consists of a powder adhesion layer and a photocurable anti-adhesion layer, and can be formed in situ on the surface of the anastomosis. When the precursor powder particles contact the digestive tract mucus and are hydrated, aldehyde groups and amino groups are released, and a Schiff base reaction occurs between the aldehyde groups and the amino groups, inducing chemical cross-linking between the precursor powder particles. At the same time, the loose porous structure formed by the accumulation of the precursor powder is fixed and maintained, thereby obtaining a complete, continuous, loose and porous powder adhesion layer hydrogel network. The photocurable anti-adhesion layer is formed by ultraviolet light initiation of a precursor solution, and the precursor solution contains 15% by mass of a polyzwitterionic polymer, 5% by mass of a methacrylated biomacromolecule and a phosphate buffer solution of a photoinitiator LAP.

2. The powder-based Janus bilayer hydrogel capable of in situ gelation at the anastomosis according to claim 1, characterized in that: The precursor powder of the powder adhesion layer is composed of aldehyde-containing macromolecules and amino-containing macromolecules; the aldehyde-containing macromolecules include one or more of oxidized chondroitin sulfate, oxidized hyaluronic acid and oxidized sodium alginate; the amino-containing macromolecules include one or more of chitosan lactate, polylysine and gelatin.

3. The powder-based Janus double-layer hydrogel capable of in situ gelation at the anastomosis according to claim 1, characterized in that: The polyzwitterionic polymer of the precursor solution includes one or more of polysulfobetaine, polycarboxybetaine and polyphosphorylcholine; correspondingly, the monomer includes one or more of sulfobetaine methacrylate, carboxybetaine methacrylate and 2-methacryloyloxyethylphosphorylcholine.

4. The powder-based Janus bilayer hydrogel capable of in situ gelation at the anastomosis according to claim 1, characterized in that: The methacrylated biomacromolecules in the precursor solution include one or more of methacrylated hyaluronic acid, methacrylated gelatin, methacrylated chondroitin sulfate, and methacrylated chitosan.

5. The powder-based Janus double-layer hydrogel capable of in situ gelation at the anastomosis according to claim 1, characterized in that: The precursor powder of the powder adhesion layer is composed of aldehyde-containing macromolecules and amino-containing macromolecules.

6. The powder-based Janus double-layer hydrogel capable of in situ gelation at the anastomosis according to claim 1 or 5, characterized in that: The powder adhesion layer contains powders of oxidized chondroitin sulfate and chitosan lactate in a mass ratio of 3:7 to 7:

3.

7. The powder-based Janus double-layer hydrogel capable of in situ gelation at the anastomosis according to claim 1, characterized in that: The synthesis steps include: 1) Preparation of aldehyde-containing macromolecules: Dissolve chondroitin sulfate, hyaluronic acid, or sodium alginate in deionized water, add sodium periodate solution to oxidize the chondroitin sulfate, dialyze, freeze-dry, and pulverize to obtain a powder of the aldehyde-containing macromolecule; 2) Preparation of a powder adhesion layer hydrogel: Powders of aldehyde-containing macromolecules and amino-containing macromolecules are thoroughly mixed in a mass ratio of 3:7 to 7:3, ground evenly, and applied to the surface of the digestive tract tissue by smearing or spraying. The powder particles absorb water, adhere, and cross-link to quickly form an adhesion layer hydrogel. 3) Preparation of polyzwitterionic polymer: Dissolve the zwitterionic monomer in phosphate buffer solution, add thermal initiator ammonium persulfate and co-initiator tetramethylethylenediamine, allow polymerization to proceed, and obtain the polyzwitterionic polymer after dialysis and freeze-drying. 4) Preparation of methacrylated biomacromolecules: Dissolve hyaluronic acid, gelatin, chondroitin sulfate, or chitosan in deionized water, add methacrylic anhydride dropwise, allow to react fully, dialyze, and freeze-dry to obtain the methacrylated biomacromolecules; 5) Preparation of a photocurable anti-adhesive layer hydrogel: Dissolve the polyzwitterionic polymer and methacrylated biomacromolecule in a phosphate buffer solution at a mass fraction of 15% and 5%, respectively. Add an appropriate amount of initiator LAP to obtain a precursor solution. Spray or apply the precursor solution to the powder adhesion layer and irradiate with 365nm UV light for 30 seconds to several minutes to form a gel.

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