Application of degradable shape memory polyurethane in preparation of ureteral stent

Abstract

The invention provides application of degradable shape memory polyurethane in preparation of a ureteral stent, and belongs to the technical field of polymer materials. The invention discloses a degradable ureteral stent based on shape memory polyurethane ISO2-PU, which has excellent shape memory function, mechanical property, degradation property, anti-crusting property and biological safety, and can effectively solve the problems of inconvenience in placement, insufficient mechanical property, non-degradation, easiness in crusting and the like in the prior art. Good application prospects are realized.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of polymer materials, and particularly relates to a use of a degradable shape memory polyurethane in preparation of a ureteral stent. BACKGROUND

[0002] Ureteral obstruction is a common urological disease that will cause damage to kidney function. Its causes of disease include upper urinary tract stone impaction, ureteral injury caused by pelvic surgery and external compression caused by tumors. Under normal circumstances, stones with a diameter of less than 4 mm will be spontaneously discharged from the body through urination, but larger stones cannot be discharged from the body through urination and will cause symptoms such as severe pain, urethral obstruction, hydronephrosis, infection and bleeding; iatrogenic ureteral injury is a terrible complication in pelvic surgery, which is usually discovered after surgery and is accompanied by symptoms such as flank pain, abdominal distension, hematuria and dysuria; obstruction caused by external compression of tumors can cause renal failure and even necrosis. The treatment approach for obstruction in clinical practice is usually to place a ureteral stent.

[0003] At present, there are various types of materials for ureteral stents on the market, and three types of ureteral stents, namely, silicone, polyurethane and metal, are still mainly used in clinical practice. Compared with other materials, silicone is not easy to form a biological membrane and crust, which makes it have a unique advantage in the application of ureteral stents. However, silicone material is soft, which increases the difficulty of placement, and a coating needs to be introduced on the surface of silicone to improve its flexibility in order to alleviate the problem of difficult placement. In addition, the tensile strength of the silicone ureteral stent is low, and it cannot play a good supporting and drainage role, resulting in low drainage efficiency. Compared with silicone ureteral stents, polyurethane ureteral stents have better mechanical properties and higher urination efficiency. Polyurethane material has higher friction with ureteral tissue, and can better keep consistent with urinary peristalsis, thereby reducing the incidence of displacement. However, polyurethane ureteral stents are more likely to form crusts, and long-term interaction with urine and extensive inflammatory response can cause the stent to break. Metal ureteral stents are mainly used for the treatment of ureteral obstruction caused by malignant external compression (such as cervical cancer, ovarian cancer and colorectal cancer) and patients who need long-term indwelling of ureteral stents. Compared with polymeric ureteral stents, metal ureteral stents have poorer biocompatibility and higher cost. The process of insertion and removal is also very complex, and metal stents are prone to displacement.

[0004] Shape memory polyurethane (SMPUs) is a block copolymer composed of soft and hard segments, the soft segment is usually a polyether or polyester macromolecular diol, and the hard segment is formed by the reaction of diisocyanate (coupling agent) with small molecular diol or diamine (chain extender). At present, SMPUs have been widely applied to the field of tissue repair, such as the construction of blood vessels and the repair of bone tissue.

[0005] The literature (DOI: 10.14136 / j.cnki.issn1673-2812.2019.01.004) reports a SMPUs ureteral stent—PCLU4 ureteral stent—using polycaprolactone diol as the soft segment, isophorone diisocyanate as the hard segment, and 1,4-butanediol as the chain extender. However, this stent has poor tensile strength, slow degradation rate, and fails to solve the problems of easy crusting of ureteral stents. Summary of the Invention

[0006] In order to address the problems existing in the prior art, the purpose of this invention is to provide a use of biodegradable shape memory polyurethane ISO2-PU in the preparation of ureteral stents.

[0007] This invention provides the use of shape memory polyurethane in the fabrication of biological scaffolds, wherein the shape memory polyurethane is composed of diisocyanate, soft segment polymer, and Linear polymers polymerized in a molar ratio of (1.2-8):1:(0.2-7) have a molecular weight of 20,000-150,000.

[0008] The soft segment polymer is polylactic acid, polyglycolic acid, polycaprolactone, polypolyol, or a copolymer of at least two of these.

[0009] Furthermore, the soft segment polymer is represented as HO-R-OH, and the structural formula of the shape memory polyurethane is shown in Formula I:

[0010]

[0011] Where x is selected from 1 to 10, and y is selected from 1 to 10;

[0012] For the repeating unit of the soft segment polymer;

[0013] It is a repeating unit of diisocyanate, or diisocyanate and The repeating unit of the copolymer.

[0014] Furthermore, the molecular weight of the soft segment polymer is 1000-10000.

[0015] Furthermore, the soft segment polymer is a polymer of lactic acid and polyol.

[0016] Furthermore, the molar ratio of repeating lactic acid units to repeating polyol units in the soft segment polymer is (10-102):(1-20).

[0017] Furthermore, the structural formula of the soft segment polymer is shown in Formula II:

[0018]

[0019] wherein m, n are independently selected from 4-50, and r is selected from 1-20.

[0020] Further, the diisocyanate is selected from aliphatic diisocyanate or aromatic diisocyanate, the aliphatic diisocyanate including hexamethylene diisocyanate, lysine diisocyanate, isophorone diisocyanate, dicyclohexylmethane diisocyanate, and the aromatic diisocyanate including at least one of toluene diisocyanate or diphenylmethane diisocyanate.

[0021] Further, the is:

[0022]

[0023] Further, the biological stent is a ureteral stent.

[0024] Further, the biological stent is obtained by melt extrusion or hot-pressing of shape memory polyurethane and coiling the tube.

[0025] In summary, the present application provides a degradable ureteral stent based on shape memory polyurethane ISO2-PU, which has excellent shape memory function, mechanical properties, degradation performance, anti-crust performance and biological safety, can effectively solve the problems of inconvenient implantation, insufficient mechanical properties, non-degradation and easy crusting in the prior art, and has good application prospect.

[0026] Compared with the literature (DOI: 10.14136 / j.cnki.issn1673-2812.2019.01.004), the present application has the following beneficial effects:

[0027] (1) The shape fixation rate (R f ) of the ISO2-PU ureteral stent of the present application is 99.6%, and the shape recovery rate (R r ) is 90.2%, while the shape fixation rate and the shape recovery rate of the PCLU4 ureteral stent are more than 87%, so the ISO2-PU ureteral stent of the present application has better shape memory function;

[0028] (2) The maximum tensile strength of the ISO2-PU ureteral stent of the present application at 37℃ can reach 25.1±2.0MPa, while the tensile strength of the PCLU4 ureteral stent is only 18.8MPa, so the ISO2-PU ureteral stent of the present application has better mechanical properties;

[0029] (3) The ISO2-PU ureteral stent of the present application has a residual weight of 61% of the initial weight after degradation in urine for 12 weeks, while the degradation rate of the PCLU4 ureteral stent is slow, and the residual weight is still 66% of the initial weight after degradation for 14 weeks, so the ISO2-PU ureteral stent of the present application has better degradation performance;

[0030] (4) The ISO2-PU ureteral stent of the present application also has excellent anti-crust performance, and the crust rate after 12 weeks is only 4.2%.

[0031] Obviously, according to the above content of the present application, according to the ordinary technical knowledge and common means in the art, other various forms of modifications, replacements or changes can be made without departing from the above basic technical idea of the present application.

[0032] The above content of the present application will be further described in detail through the specific embodiments below. However, this should not be understood as the scope of the above subject matter of the present application being limited to the following embodiments. Any technology realized based on the above content of the present application belongs to the scope of the present application. BRIEF DESCRIPTION OF DRAWINGS

[0033] Figure 1 Synthesis scheme of PDLLA-PEG400-PDLLA.

[0034] Figure 2 Synthesis scheme of HDI-ISO-HDI.

[0035] Figure 3 Synthesis scheme of ISO2-PU (DI represents HDI-ISO-HDI; R represents PDLLA-PEG400-PDLLA; DI' represents the main chain of HDI-ISO-HDI).

[0036] Figure 4 Synthesis scheme of HDI-ISO-HDI 1 H NMR spectrum (a) and FTIR spectrum (b).

[0037] Figure 5 Synthesis scheme of ISO2-PU.

[0038] Figure 6 FTIR spectra of PDLLA-PEG400-PDLLA and ISO2-PU.

[0039] Figure 7 FTIR spectra of PDLLA-PEG400-PDLLA and ISO2-PU 1 H NMR spectrum.

[0040] Figure 8GPC curves for ISO2-PU (chloroform for flowability).

[0041] Figure 9 It is a tubular support formed by hot pressing and film formation of ISO2-PU followed by winding and melt extrusion.

[0042] Figure 10 The TGA(a) and DTGA(b) curves are shown before and after heat treatment of ISO2-PU.

[0043] Figure 11 GPC curves of ISO2-PU before and after heat treatment at 100℃ (trichloromethane as the mobile phase).

[0044] Figure 12 The DSC curves of ISO2-PU before and after hot pressing at 100℃ are shown.

[0045] Figure 13 DSC curves of ISO2-PU ureteral stent after immersion in AU(a) and PBS(b) for different times.

[0046] Figure 14 The diagram shows a flat plate compression test (a) and an axial tension test (b).

[0047] Figure 15 The compressive stress-strain curves (a) and compressive strength (b) of the ISO2-PU stent (n=4) are shown.

[0048] Figure 16 The tensile stress-strain curves (a), tensile strength (b), and elongation at break (c) of the ISO2-PU scaffold are shown (n=4).

[0049] Figure 17 Tensile properties of ISO2-PU stents after immersion in a medium at 37℃ for different times (AU: tensile stress-strain curve (a), breaking strength (b) and elongation at break (c); PBS: tensile stress-strain curve (d), breaking strength (e) and elongation at break (f) (n=4)).

[0050] Figure 18 The diagram shows the 2D shape memory process (a) and the 3D shape memory process (b) of ISO2-PU.

[0051] Figure 19 The shape memory performance of ISO2-PU in three scenarios: folding-unfolding, unfolding-bending, and bending-unfolding (a: air, b: AU, c: PBS, d: shape recovery rate) (n=3).

[0052] Figure 20The curve showing the change in the residual mass of the ISO2-PU stent over degradation time (degradation solution: artificial urine; n=3).

[0053] Figure 21 SEM images of the surfaces of Silicon, PU, ​​and ISO2-PU after immersion in artificial urine for different times.

[0054] Figure 22 The crusting of Silicon, PU, ​​and ISO2-PU in artificial urine is shown (yellow marks indicate the crusted area, and green lines represent the entire surface area).

[0055] Figure 23 The crust coverage rate of Silicon, PU and ISO2-PU after soaking in artificial urine for different times (n=3).

[0056] Figure 24 Subcutaneous placement of ISO2-PU ureteral stent (a) and commercial PU ureteral stent (b) in rats.

[0057] Figure 25 The relative proliferation rate (RGR) of the three cell types on the ISO2-PU membrane (n=3).

[0058] Figure 26 Live / dead staining images of cells after co-culturing with ISO2-PU for 24 hours.

[0059] Figure 27 Laser confocal microscopy images of cells after 24 hours of co-culturing with ISO2-PU.

[0060] Figure 28 For the pathological analysis of rat muscle tissue (the last number in the sample name represents the number of weeks after implantation).

[0061] Figure 29 Histopathological analysis of major organs of rats (the last number in the sample name represents the number of weeks of implantation). Detailed Implementation

[0062] The raw materials and equipment used in this invention are all known products, obtained by purchasing commercially available products.

[0063] Unless otherwise specified, the "room temperature" condition referred to in this invention is 25±5℃.

[0064] Example 1: Preparation of ISO2-PU ureteral stent

[0065] 1. Synthesis of PDLLA-PEG400-PDLLA macromolecular diol

[0066] Synthesis of PDLLA-PEG400-PDLLA macromolecular diol, such asFigure 1 Specifically, as shown, 288g of D,L-lactide (2mol), 16g of PEG400 (0.04mol), and 162mg of Sn(Oct)2 (0.4mmol) were added to a single-necked flask at a molar ratio of 5000:100:1. The flask was evacuated for 1 hour and then sealed. The reaction was then carried out in an oil bath at 140℃ for 24 hours. The product was purified three times using a dichloromethane-ice-anhydrous ethanol (-20℃) system; finally, it was purified once more using dichloromethane-ice-n-hexane (-20℃). After vacuum drying, 275g of PDLLA-PEG400-PDLLA was obtained for later use.

[0067] 2. Synthesis of long-chain diisocyanate HDI-ISO-HDI

[0068] Synthesis of long-chain diisocyanate HDI-ISO-HDI as follows Figure 2 As shown, specifically: 160 g HDI (0.8 mol) and 29.2 g ISO (0.2 mmol) were added to a single-necked flask; DMF was then added at a DMF:ISO volume-to-mass ratio of 6:1; finally, Sn(Oct)2 was added at a molar ratio of Sn(Oct)2:ISO = 1:500; the reaction was carried out at 75 °C for 1 h under nitrogen protection. The sample was washed with anhydrous n-hexane to remove unreacted HDI, yielding approximately 100 g of granular HDI-ISO-HDI for later use.

[0069] 3. Synthesis of ISO2-PU

[0070] The synthesis route of ISO2-PU is as follows: Figure 3 As shown, specifically: First, 220g of PDLLA-PEG400-PDLLA was added to a four-necked flask. HDI-ISO-HDI was added at a molar ratio of HDI-ISO-HDI:PDLLA-PEG400-PDLLA = 1.5:1.0, followed by DMF. The mixture was dissolved and stirred at 75℃ for 1 hour. Then, Sn(Oct)2 was added, and the reaction was allowed to proceed for 3 hours. Finally, ISO was added at a ratio of PDLLA-PEG400-PDLLA:ISO = 1.0:0.5, and the reaction was allowed to proceed for 16 hours. The product was purified three times at room temperature using a dichloromethane-anhydrous ethanol system; finally, it was purified once more using dichloromethane-n-hexane. After vacuum drying, 218g of ISO2-PU was obtained for later use.

[0071] 4. Fabrication of ISO2-PU ureteral stent

[0072] Hot-pressed tubing: At 100℃, fully dried ISO2-PU material is placed between two PTFE plates. The PTFE plates are then placed between the upper and lower heating plates of the hot press and fixed. Pressure is applied to 5MPa, held for 30s, and then released. This process is repeated three times. Pressure is then applied to 10MPa, held for 30s, and then released. This process is repeated twice. Finally, pressure is applied to 15MPa and held. The power is turned off, and the material is allowed to cool naturally for 3 hours before being demolded on a 40℃ heating plate. The membrane is then rolled into a tube using a 2mm diameter iron core and the ends are sealed with chloroform to obtain a ureteral stent.

[0073] Melt extrusion: Fully dried ISO2-PU granules are fed into the hopper of a single-screw extruder and melted to form a tube. The inlet temperature is room temperature, the temperature of the middle section of the bolt is 110℃, and the extrusion outlet temperature is 80℃. The die diameter is 2mm. After cooling with room temperature air, a ureteral stent is obtained.

[0074] The following experimental examples demonstrate the beneficial effects of the present invention.

[0075] Experimental Example 1: Structural Characterization

[0076] 1. Experimental Methods

[0077] (1) FTIR characterization

[0078] Fourier transform infrared spectroscopy (Nicolet iS50) was used to record the HDI-ISO-HDI, PDLLA-PEG400-PDLLA, and ISO2-PU samples in the range of 400–4000 cm⁻¹. -1 Characteristic peaks within the range. HDI-ISO-HDI samples were prepared using the KBr pelleting method. First, all relevant instruments were wiped at least three times with degreased cotton balls soaked in anhydrous ethanol, dried under infrared light, and then an appropriate amount of spectrally pure KBr was placed in an agate mortar and ground until the KBr particles showed adhesion. The KBr was then placed in a pelleting mold, pressurized to 15 MPa, and held for 30 seconds to form a transparent sheet, i.e., a KBr blank. 1–2 mg of HDI-ISO-HDI was mixed with spectrally pure KBr (100 mg), ground into a fine powder in an agate mortar, and a transparent sheet was prepared using the same method. FTIR spectra were then acquired using transmission mode. PDLLA-PEG400-PDLLA and ISO2-PU samples were dissolved in dichloromethane to prepare solutions of 15 mg / mL. 50 μL of each solution was applied to the KBr surface, evaporated to form a film under infrared light, and FTIR spectra were acquired using transmission mode.

[0079] (2) 1 H NMR characterization

[0080] Dissolve an appropriate amount of HDI-ISO-HDI in deuterated trifluoroacetic acid to prepare a 15 mg / mL solution; dissolve fully dried PDLLA-PEG400-PDLLA and ISO2-PU in deuterated chloroform to prepare 15 mg / mL solutions. Then, collect samples using a nuclear magnetic resonance spectrometer (model: AVANCE NEO 400). 1 H NMR spectrum.

[0081] (3) Molecular weight determination of ISO2-PU

[0082] ISO2-PU was prepared into a 25 mg / mL solution using chromatographic grade chloroform. The weight-average molecular weight (Mb) of the sample was then determined using a gel permeation chromatography system (Waters 1515) at a flow rate of 1.0 mL / min. w Number-average molecular weight (M) n ) and molecular weight distribution index (PDI).

[0083] 2. Experimental Results

[0084] (1) Structural characterization of HDI-ISO-HDI

[0085] When excess HDI reacts with ISO, the theoretical molecular structure of the product is: HDI-(ISO-HDI)n (n≥1, and an integer). The HDI-(ISO-HDI)n obtained using a 4:1 molar ratio of HDI to ISO was subjected to... 1 H NMR characterization, results as follows Figure 4 As shown in (a). In 1 In the 1H NMR spectrum, the peaks at δ = 5.30–5.33 ppm (H-5 and H-2), δ = 5.10 ppm (H-4), δ = 4.80 ppm (H-3), and δ = 3.99–4.30 ppm (H-1 and H-6) are attributed to proton absorption peaks on the ISO ring. The peaks at δ = 3.12–3.27 ppm (Ha, H-a'), δ = 1.56–1.70 ppm (Hb, H-b'), and δ = 1.33–1.51 ppm (Hc, H-c') are attributed to methylene proton absorption peaks in HDI. Figure 2 The molar ratio of HDI to ISO in HDI-(ISO-HDI)n can be calculated according to formula (1) based on the integral area (I) of peak δ=3.12~3.27ppm(Ha,H-a') and peak δ=4.80ppm(H-3).

[0086] HDI / ISO = I H-a ′ +a / (I H-3 ×4)(1)

[0087] according to Figure 4 (a) The calculation shows that HDI / ISO is close to 2 (7.74 / (1.00×4)≈2), indicating that the molar ratio of HDI to ISO in the product is 2:1. Therefore, the product structure is HDI-(ISO-HDI)1, that is, HDI-ISO-HDI.

[0088] Figure 4 (b) shows the FTIR spectrum of HDI-ISO-HDI at 2273 cm⁻¹. -1 An absorption peak of the -NCO group is visible at [location missing]. Since unreacted HDI was removed by washing with dried n-hexane after the complete reaction of HDI and ISO, this -NCO absorption peak should originate from the terminal -NCO of the HDI-ISO-HDI group. Furthermore, at 1698 cm⁻¹... -1 Absorption peaks were observed at the -C=O group of the urethane bond. These results further confirm the successful synthesis of HDI-ISO-HDI.

[0089] (2) Structural characterization of ISO2-PU

[0090] Based on the molar ratio of HDI-ISO-HDI, PDLLA-PEG400-PDLLA, and ISO used in the synthesis of ISO2-PU, the theoretical structural formula of ISO2-PU should be: Figure 5 The structure shown.

[0091] 1) FTIR characterization

[0092] Figure 6 The FTIR spectra of PDLLA-PEG400-PDLLA and ISO2-PU are shown. Compared to the former, the FTIR spectrum of ISO2-PU is at ~1529 cm⁻¹. -1 ~1621cm -1 and 3300-3400cm -1 New absorption peaks appeared at all locations, belonging to the absorption peaks of amide II band (-NH bending vibration), amide I band (-C=O stretching vibration), and the stretching vibration absorption peak of -NH in the carbamate bond, respectively. Furthermore, in the ISO2-PU spectrum, a peak was observed at 2273 cm⁻¹. -1 The absence of the characteristic absorption peak of -NCO indicates that HDI-ISO-HDI has completely reacted with PDLLA-PEG400-PDLLA and ISO to form the target product ISO2-PU.

[0093] 2) 1 H NMR characterization

[0094] To further verify the successful synthesis of ISO2-PU, samples of PDLLA-PEG400-PDLLA and ISO2-PU were collected, respectively. 1 H NMR spectra, results as follows Figure 7 As shown. In PDLLA-PEG400-PDLLA 1 In the 1H NMR spectrum, several characteristic peaks appeared: the peak at δ = 5.16 ppm (HA) is the -CH proton absorption peak on the lactoyl unit of the macromolecular diol; the peak at δ = 4.35 ppm (HC) is the -CH2 proton absorption peak of the PDLLA block in PEG400; the peak at δ = 4.25 ppm (H-A') is the -CH proton absorption peak of the terminal lactic acid residue of the macromolecular diol connected to -OH; the peak at δ = 3.64 ppm (HD) is the -CH2 proton absorption peak in PEG400; the peak at δ = 1.57 ppm (HB) is the -CH3 proton absorption peak of the lactoyl unit of the macromolecular diol; and the peak at δ = 1.48 ppm (H-B') is the -CH3 proton absorption peak of the terminal lactic acid residue of the macromolecular diol.

[0095] Using PDLLA-PEG400-PDLLA 1 The H NMR spectrum, by integrating the characteristic peaks, yields I. H-A =17.08, I H-A'+C =1.00, and the molecular weight (M) of PDLLA-PEG400-PDLLA is calculated based on the integral and formula (2). n The value is 7900. The number of moles of the macromolecular diol per unit mass can be calculated based on the molecular weight of PDLLA-PEG400-PDLLA, which is the basis for achieving the feed ratios of PDLLA-PEG400-PDLLA, HDI-ISO-HDI, and ISO.

[0096]

[0097] Compared to PDLLA-PEG400-PDLLA, ISO2-PU's 1 The 1H NMR spectrum showed significant changes: proton absorption peaks belonging to HDI, namely H-a', H-b', and H-c', appeared at δ = 3.14 ppm, δ = 1.38 ppm, and δ = 1.28 ppm, respectively; characteristic proton peaks on the ISO ring, namely H-1 to H-6, appeared at δ = 5.12 ppm, δ = 4.78 ppm, δ = 4.50 ppm, and δ = 3.98 ppm. Furthermore, the peaks at δ = 4.36–4.46 ppm (H-A') and δ = 1.48 ppm (H-B') almost completely disappeared. These results further confirm the successful synthesis of ISO2-PU.

[0098] 3) Molecular weight detection

[0099] The molecular weight of ISO2-PU was determined using GPC, and the results are as follows: Figure 8 As shown. Number-average molecular weight (M) of ISO2-PU n The weight-average molecular weight (M) is 37.7 kDa. w The value is 86.9 kDa, and the polydispersity index (PDI) is 2.31.

[0100] (3) Structural characterization of ISO2-PU ureter

[0101] The outer diameter ranges of ureteral stents obtained by hot-pressing and melt extrusion are 2.7–3.0 mm and 1.4–1.5 mm, respectively. Figure 9 Within the commonly used ureteral stent outer diameter range (1.23–4.67 mm).

[0102] The ISO2-PU ureteral stents used in the following experimental examples are all ureteral stents obtained by thermoforming and rolling.

[0103] Experiment Example 2: Testing the thermal properties of ISO2-PU ureteral stent

[0104] 1. Experimental Methods

[0105] (1) DSC test: This test was performed on a DSC3+ professional differential scanning calorimeter from Mettler Toledo GmbH, Switzerland. In the test procedure, the sample temperature was first raised from 20℃ to 180℃ and held for 3 min; then cooled to -10℃ and held for 3 min; finally, it was raised to 150℃ again. The temperature change rate during the test was 10℃ / min.

[0106] (2) TGA test: The test was performed on a TGA2 thermogravimetric analyzer from Mettler Toledo, Switzerland, with a heating rate of 10°C / min throughout the test.

[0107] (3) GPC Test: The change in molecular weight of ISO2-PU before and after heat treatment was detected to indicate the thermal stability of the ISO2-PU scaffold. Chromatographic grade chloroform was used as a solvent to prepare a solution of ISO2-PU with a concentration of 25 mg / mL before and after heat treatment. The molecular weight of the sample was detected using a gel permeation chromatograph (Waters 1515) at a flow rate of 1.0 mL / min. w M n And PDI.

[0108] 2. Experimental Results

[0109] (1) Thermogravimetric analysis

[0110] Thermal stability is a prerequisite for hot processing. The thermal stability of ISO2-PU was evaluated using TGA. Figure 10 The TGA and DTG curves of ISO2-PU before and after heat treatment are shown. The initial decomposition temperature of the raw ISO2-PU is 245.8℃, and the initial decomposition temperature of ISO2-PU after heat treatment is 250.2℃. The DTG curves show that the temperatures with the fastest decomposition rates of ISO2-PU before and after processing are 275.8℃ and 280.3℃, respectively. These results indicate that a heat treatment temperature of 100℃ is much lower than the thermal decomposition temperature of ISO2-PU, and heat treatment at 100℃ has no significant effect on the thermal stability of ISO2-PU.

[0111] (2) Molecular weight detection

[0112] During hot processing, unstable groups in the PU structure, such as urethane groups, may undergo thermal degradation, leading to a decrease in molecular weight. Therefore, the molecular weight of ISO2-PU before and after hot pressing was further measured to examine whether ISO2-PU underwent thermal degradation during hot pressing. The GPC curves of ISO2-PU before and after hot pressing are shown below. Figure 11 As shown, the corresponding molecular weight and molecular weight distribution results are shown in Table 1. The molecular weight of ISO2-PU before hot pressing... n M w The PDI values ​​were 37.7 kDa, 86.9 kDa, and 2.31, respectively, and the corresponding values ​​after hot pressing were 35.0 kDa, 81.9 kDa, and 2.34. These results indicate that hot pressing has no significant effect on the molecular weight of ISO2-PU, further demonstrating that the 100℃ hot pressing process is suitable for processing ISO2-PU ureteral stents.

[0113] Table 1. M of ISO2-PU before and after hot pressing at 100℃ n M w and PDI

[0114]

[0115] (3) DSC test

[0116] The shape memory temperature of ISO2-PU is its T0. g DSC was used to detect T. g The result is as follows Figure 12 As shown, no melting endothermic peak was observed in ISO2-PU before and after hot pressing, indicating that ISO2-PU does not have a clear crystalline structure and is an amorphous polymer. The Tg of ISO2-PU before and after processing... g The values ​​were 40.4℃ and 40.6℃ respectively, indicating that hot pressing at 100℃ had a significant impact on its TT. g There was no significant impact.

[0117] Water has a plasticizing effect on polymer molecular chains and may reduce the polymer's T0. g Values. This experiment collected DSC curves of ISO2-PU ureteral stents soaked in AU and PBS for 2 h, 12 h, 24 h, and 48 h. Figure 13 The results showed that after ISO2-PU ureter was immersed in PBS and AU for 48 hours, its T... g The values ​​decreased only slightly (40.6℃→39.9℃; 40.6℃→40.0℃), which should be related to the low water absorption rate of ISO2-PU and the weak plasticizing effect of water molecules on the ISO2-PU chain.

[0118] Experiment Example 4: Testing the mechanical properties of ISO2-PU ureteral stent

[0119] 1. Experimental Methods

[0120] A ureteral stent is placed inside the ureter to provide support and drainage. The mechanical properties of the stent, including its radial compressive strength and axial tensile strength, directly affect its effectiveness.

[0121] (1) Radial compressibility

[0122] The radial compressive properties of the support were tested using a small, multi-scale, in-situ mechanical testing system, such as... Figure 14 As shown in (a). The sample dimensions are an outer diameter of 2.8 mm and a length of 5 mm. Fixed-distance compression was used, with a maximum compression distance of 50% of the support's inner diameter. The compression test procedure was as follows: First, the support was placed on a circular platform, and then the upper circular platform was moved downwards until it contacted the support and stopped. Then, it was moved downwards at a speed of 5 mm / min until the upper circular platform compressed the support to 50% of its inner diameter. Then, the upper circular platform was moved upwards again at a speed of 5 mm / min until it separated from the support surface.

[0123] (2) Axial tensile properties

[0124] The axial tensile properties of the support were tested using a small, multi-scale, in-situ mechanical testing system, such as... Figure 14 (b) shows the sample size of a ureteral stent with an outer diameter of 2.8 mm and an effective length of 20 mm. According to YY / T0872-2013 "Test Method for Ureteral Stents", the loading rate is 200 mm / min.

[0125] (3) Effects of water on the mechanical properties of ISO2-PU ureteral stents

[0126] Tensile mechanical tests were performed on ureteral stents after soaking in AU and PBS for 0h, 2h, 12h, 24h, and 48h, respectively. Fourier transform infrared spectroscopy in reflectance mode was used to collect data from ISO2-PU ureteral stents soaked in AU and PBS for different times at 4000–400 cm⁻¹. -1 Infrared absorption peaks within the range.

[0127] 2. Experimental Results

[0128] (1) Radial compressibility

[0129] The radial compression results of the ISO2-PU ureteral stent are as follows: Figure 15 As shown, the maximum compressive strength at room temperature (25℃) reached 8.5±0.5MPa, but the strain of the stent did not return to its initial state after stress removal. This is related to the fact that ISO2-PU is in a glassy state at 25℃ and lacks high elasticity. When the temperature is increased to near body temperature (36.5℃, 37℃, 37.5℃), due to the proximity to the glass transition temperature (~40℃), the stent exhibits high elasticity in the glass transition region, and the stent basically rebounds to its initial state after the compressive stress is removed. The maximum compressive strengths at 36.5℃, 37℃, and 37.5℃ are 5.1±0.2MPa, 4.7±0.1MPa, and 4.2±0.1MPa, respectively.

[0130] (2) Axial tensile properties

[0131] Further testing of the axial tensile properties of the ISO2-PU scaffold yielded the following results: Figure 16 As shown, the maximum tensile strength of the support reached 48.5±5.4MPa at room temperature (25℃); as the temperature increased, its maximum tensile strength decreased significantly, with the maximum tensile strengths at 36.5℃, 37℃, and 37.5℃ being 27.3±2.2MPa, 25.1±2.0MPa, and 23.7±1.8MPa, respectively.

[0132] (3) The effect of water molecules on the mechanical properties of ISO2-PU ureteral stents

[0133] The results of Experiment 2 show that the ISO2-PU scaffold reached saturation after immersion in AU and PBS at 37℃ for 48 hours. After absorbing water, the mechanical properties of the polymer material may change due to the plasticizing effect of water on the molecular chains. Further testing of the tensile mechanical properties of the ISO2-PU scaffold after immersion in AU and PBS for 0 h, 2 h, 12 h, 24 h, and 48 h yielded the following results: Figure 17 As shown, immersion in the medium significantly altered the stress-strain curve characteristics of the ISO2-PU scaffold. Specifically, the initial ISO2-PU scaffold exhibited a clear stress yielding curve but no significant strain enhancement characteristic.Figure 17 a) After immersion in AU and PBS, the stress yielding phenomenon disappeared, and a significant strain enhancement occurred. Figure 17 a) and d) resulted in a decrease in their maximum tensile strength, but both were still above 18 MPa (the requirement for the tensile strength of ureteral stents). Figure 17 b, e).

[0134] Experiment Example 5: Testing the shape memory performance of the ISO2-PU ureteral stent

[0135] 1. Experimental Methods

[0136] (1) Dynamic thermomechanical method

[0137] The test was performed using a DMA-Q800 dynamic mechanical analyzer from TA Instruments, USA. The shape memory properties of ISO2-PU material were evaluated using a tensile method. The sample dimensions were 50.0 mm in length, 8.0 mm in width, and 0.2 mm in thickness. The test procedure started at 25°C, and then the sample temperature was increased to the shape memory transition temperature (T0) at a rate of 5°C per minute. tran Hold for 5 minutes; then increase the strain to 50% and hold for 5 minutes; subsequently cool at a rate of 5°C / min to a shape-fixing temperature (T0) 5°C below the glass transition temperature. fix Maintain this temperature for 5 minutes; finally, after removing the external force, raise the temperature again to T at a rate of 5℃ / min. tran Shape memory is then restored to its original shape. Shape memory performance is measured by the shape retention rate (R0). f ) and shape recovery rate (R r The two are measured by equations (3) and (4), respectively.

[0138]

[0139] Where ε1 is in T tran The strain applied to the sample after isothermal treatment for 5 minutes, ε2 is the strain applied after cooling to T. fix The strain after stress removal following 5 minutes of isothermal treatment, ε3 is the strain at temperature T. tran The strain after the shape has fully recovered after 40 minutes of isothermal treatment.

[0140] (2) Special Shape Shaping-Recovery Method

[0141] To visualize the shape memory performance, the shape memory performance of three shaping methods—folding-unfolding, bending-unfolding, and unfolding-bending—was tested in three environments: air at 42°C, AU, and PBS. R was calculated based on equations (5) and (6). f With R r .

[0142]

[0143] Where θ0 is the initial angle, θ1 is the angle after shaping, θ2 is the angle after stress removal, and θ3 is the angle after shape recovery.

[0144] 2. Experimental Results

[0145] DMA is a commonly used method for quantitatively testing the shape memory effect of shape memory polymers. The two-dimensional (2D) and three-dimensional (3D) "shape-fixation-recovery" cycle diagrams of ISO2-PU obtained using DMA are illustrated below. Figure 18 The shape retention rate (R) of ISO2-PU can be calculated. f The shape recovery rate was 99.6%, and the shape recovery rate (R) was 99.6%. r The result was 90.2%, indicating that ISO2-PU has good shape retention and shape recovery capabilities.

[0146] To better verify whether the shape memory performance of ISO2-PU can achieve shape recovery of special structures (such as double J-shape) during in vivo application, the shape memory performance of ISO2-PU membrane and scaffold in three scenarios—folding-unfolding, unfolding-bending, and bending-unfolding—was tested in air, AU, and PBS environments. Figure 19 The results showed that ISO2-PU could effectively recover its shape in all three environments, with a shape recovery rate (R0). r All values ​​are above 86.5%, indicating good shape memory performance.

[0147] The above shape memory performance test results indicate that the shape memory performance of the ISO2-PU ureteral stent is expected to enable the stent to self-adapt to complex shapes in vivo.

[0148] Experiment Example 6: Testing the in vitro degradation and anti-crusting properties of ISO2-PU ureteral stent

[0149] 1. Experimental Methods

[0150] (1) Testing the mass change of ISO2-PU ureteral stent

[0151] Preparation of AU: Prepared according to the experimental method described in Experimental Example 2.

[0152] Degradation Test: The test sample was an ISO2-PU ureteral stent with a length of 20 mm and an outer diameter of 3.0 mm. According to YY / T 0473-2004 "In Vitro Degradation Test", the ratio of degradation solution volume (mL) to sample mass (g) should be greater than 30:1. Approximately 0.10 g (W0) of the dried sample was placed in a separate glass bottle, 10 mL of AU was added, and the bottle was then placed in a 37°C constant temperature shaker. Every 2, 4, 6, 8, 10, and 12 weeks, the ISO2-PU stent was removed from the degradation solution, vacuum dried, and weighed (W0). t ), and store for later use. Calculate the residual mass percentage (WR, %) according to formula (7).

[0153]

[0154] (2) Structural analysis of ISO2-PU ureteral stent during degradation

[0155] The vacuum-dried ISO2-PU scaffold from step (1) was used for the following analysis.

[0156] ATR-FTIR: Fourier transform infrared spectrometer (model: Nicolet iS50) was used to collect the sample at 4000–4000 cm⁻¹. -1 FTIR spectra of the range, reflectance mode, 8 scans per sample.

[0157] 1 ¹H NMR: Weigh an appropriate amount of dried ISO2-PU sample, dissolve it in deuterated chloroform, and prepare a test solution with a concentration of 15 mg / mL. NMR was performed using an AVANCE NEO 400 nuclear magnetic resonance spectrometer. 1 H NMR spectrum.

[0158] (3) Surface crusting of ISO2-PU ureteral stent

[0159] ISO2-PU, commercial silicone, and polyurethane scaffolds were immersed in AU for a certain period of time (2, 4, 6, 8, 10, and 12 weeks), then removed and vacuum dried to constant weight. The surface crusting of the scaffolds was observed using a desktop scanning electron microscope (model: TM-4000Plus).

[0160] 2. Experimental Results

[0161] (1) Results of mass changes in ISO2-PU ureteral stent

[0162] The relationship between the residual weight percentage of the ISO-2PU scaffold in AU and degradation time is shown in the curve. Figure 20As shown, ISO2-PU began to show significant weight loss after immersion in AU for 6 weeks, and the weight began to decrease sharply after 8 weeks. After 12 weeks of degradation, its residual mass was 61.55±1.02wt%.

[0163] (2) Anti-caking results of ISO2-PU ureteral stent

[0164] This study used commercial silicone and polyurethane materials as controls, and acquired SEM images of ISO2-PU supports after immersion in 37℃AU for different times using a desktop scanning electron microscope. Figure 21 Use ImagePro software to circle the crusted area in the image. Figure 22 The area covered by the crust (yellow curve) is calculated, and then divided by the total area of ​​the entire region (green curve in the figure) to obtain the crust coverage rate. The results show ( Figure 23 At all time points, the crust coverage on the surface of the ISO2-PU scaffold was significantly lower than that of commercial silicone and polyurethane scaffolds, demonstrating the excellent anti-crusting performance of ISO2-PU material.

[0165] The experimental results show that the ISO2-PU ureteral stent has significant in vitro degradation performance and anti-crusting properties.

[0166] Experiment 7: Testing the biocompatibility of ISO2-PU ureteral stents

[0167] 1. Experimental Methods

[0168] (1) In vitro cell compatibility

[0169] ISO2-PU membranes were prepared according to the method in Example 1. The samples were sterilized by UV irradiation of both sides for 3 hours each, washed three times with PBS, and then placed in well plates. ISO2-PU membranes were added as the experimental group, and the well plate substrate served as the blank control group. DMEM high-glucose medium containing 10 vol% fetal bovine serum and 1 vol% penicillin-streptomycin was prepared.

[0170] 1) CCK-8 characterizes cell proliferation activity

[0171] Mouse fibroblasts (L929), porcine small intestinal epithelial cells (IPEC-J2), and mouse aortic vascular smooth muscle cells (MOVAS) were seeded into well plates, approximately 1.8 × 10⁻⁶ cells per well. 3100 μL of culture medium was added to each cell and incubated in a cell culture incubator at 37°C and 5% CO2. After 1, 3, and 5 days of cell culture, the residual culture medium was discarded, and the cells were washed three times with PBS. Then, 100 μL of 10% CCK-8 solution was added to each well, wrapped with aluminum foil, and incubated in a cell culture incubator for 2 hours in the dark. Finally, the absorbance (OD value) of the incubation solution at 450 nm was detected using a Model 680 microplate reader to evaluate whether the ISO2-PU material produced cytotoxicity and its effect on the proliferation of the three cell types. The relative cell proliferation rate (RGR, %) was calculated using formula (8):

[0172]

[0173] According to GB / T 16886.5—2017, a decrease in cell viability RGR greater than 30% is considered a cytotoxic reaction.

[0174] 2)Live / dead dyeing

[0175] L929, IPEC-J2 and MOVAS cells were seeded into well plates for 24 h, then the culture medium was discarded and the cells were washed once with PBS. 500 μL of cell viability / dead staining solution was added to each well, and the cells were stained at room temperature in the dark for 10 min. The staining solution was then discarded and the cells were washed once with PBS. Finally, the cells were photographed and recorded using a fluorescence microscope.

[0176] 3) Cell spreading

[0177] L929, IPEC-J2, and MOVAS cells were seeded into wells of a plate, with approximately 4.0 × 10⁶ cells per well. 3 Cells were cultured in 200 μL of culture medium and then incubated in a 37°C, 5% CO2 cell culture incubator for 24 h. The culture medium was then aspirated and the cells were washed three times with PBS. Next, 1000 μL of 4% paraformaldehyde fixative was added to each well, and the cells were fixed at 4°C for 0.5 h. The fixative was then aspirated and the cells were washed three times with PBS. Then, an appropriate amount of Trion was added to each well, and the cells were permeabilized at room temperature for 10 min. The permeabilized cells were then aspirated and the cells were washed three times with PBS. Next, 200 μL of rhodamine-labeled phalloidin staining solution was added to each well, and the cells were treated in the dark and then incubated at 4°C overnight. The staining was then aspirated and the cells were washed three times with PBS. Finally, the morphology of the three cell types was recorded using a TCS SP8 laser confocal microscope.

[0178] (2) In vivo biosafety assessment

[0179] 1) Grouping of experimental rats

[0180] Twenty-five SD rats weighing approximately 300g were randomly divided into five groups. Group 1 served as the blank control group. Groups 2 and 4 underwent subcutaneous implantation of an ISO2-PU ureteral stent, while groups 3 and 5 underwent subcutaneous implantation of a commercially available PU ureteral stent. Postoperatively, the rats' physiological activities, including feeding, behavior, and excretion, were observed daily. Group 1 was sacrificed after one week; groups 2 and 3 were sacrificed after four weeks; and groups 4 and 5 were sacrificed after eight weeks. Groups 1-5 were designated Control, ISO2-PU-4, PU-4, ISO2-PU-8, and PU-8, respectively. Figure 24 Schematic diagram of subcutaneous placement of two types of scaffolds in rats. All SD rats were fed and cared for in accordance with the guidelines of the Institutional Animal Care and Use Committee of Chongqing University (Approval No.: CQU-IACUC-RE-202306-004).

[0181] 2) Detection indicators after rat dissection

[0182] First, rats were euthanized painlessly under overdose anesthesia. Then, the subcutaneous tissue was incised and dissected, and the implanted ureteral stent and a small amount of surrounding muscle tissue were removed. These tissues were fixed in 4% paraformaldehyde fixative at 4°C for 24 hours. Subsequently, five organs—heart, liver, spleen, lung, and kidney—were collected. These organs were also fixed in 4% paraformaldehyde fixative at 4°C for 24 hours. Finally, the muscle tissue and internal organs were paraffin-embedded, sectioned, stained with hematoxylin and eosin (HE), and subjected to pathological examination.

[0183] 2. Experimental Results

[0184] (1) Evaluation of in vitro cytotoxicity

[0185] 1) CCK-8

[0186] The proliferation activity of L929, IPEC-J2, and MOVAS cells was detected using CCK-8 assay after 5 days of co-culture with ISO2-PU membrane. The results are as follows: Figure 25 As shown, L929, IPEC-J2, and MOVAS cell lines all maintained normal proliferation rates. Compared with the blank control group, the relative proliferation rates of the three cell lines at the three time points were all above 90%, indicating that the ISO2-PU material had no significant toxicity to L929, IPEC-J2, and MOVAS cell lines.

[0187] 2)Live / dead dyeing

[0188] live / dead stain( Figure 26 The results showed that L929, IPEC-J2 and MOVAS cells did not cause significant cell death after being co-cultured with ISO2-PU for 24 hours.

[0189] 3) Cell spreading

[0190] Figure 27 The images show the cell morphology of L929, IPEC-J2, and MOVAS cells co-cultured with ISO2-PU membranes for 12 h and 24 h. Compared with the blank control, the cell spreading morphology of the experimental groups showed no significant difference at 12 h and 24 h, indicating that ISO2-PU has good cell compatibility.

[0191] (2) In vivo safety evaluation

[0192] The in vivo biocompatibility of the ISO2-PU ureteral stent was evaluated using a rat subcutaneous implantation assay at 4 and 8 weeks, with corresponding sample labels of PU-4, PU-8, and ISO2-PU-4, ISO2-PU-8. Histopathological examination of the surrounding muscle tissue after stent implantation was performed; HE staining results are shown below. Figure 28 As shown in the figure. Neither the ISO2-PU ureteral stent nor the commercially available PU ureteral stent induced acute inflammatory response or persistent inflammation. There were no significant differences in pathology between the ISO2-PU experimental group and the PU control group compared to the blank group. No abnormal changes such as myofibril degeneration, inflammatory cell infiltration, or necrosis were observed in the surrounding muscle tissue sections. Histopathological examinations were performed on the major organs of the rats: heart, liver, spleen, lungs, and kidneys. HE staining results are shown in the figure. Figure 29 As shown in the figure, there were no significant differences in organ and tissue morphology between the rats and the control group. The parenchymal structure of each organ was normal, with no obvious tissue damage, inflammation, or fibrosis, and no changes in cell structure were observed. These results indicate that ISO2-PU has good in vivo safety.

[0193] Cytotoxicity evaluation tests showed that the ISO2-PU scaffold was not cytotoxic to fibroblasts, epithelial cells, or endothelial cells. Subcutaneous implantation tests in rats showed that the ISO2-PU scaffold did not cause significant lesions in surrounding muscle tissue and major organs, demonstrating good in vivo biocompatibility.

[0194] In summary, this invention provides a biodegradable ureteral stent based on shape memory polyurethane ISO2-PU. This stent has excellent shape memory function, mechanical properties, degradation performance, anti-crusting performance, and biocompatibility. It can effectively solve the problems of inconvenient insertion, insufficient mechanical properties, non-degradability, and easy crusting in existing technologies, and has good application prospects.

Claims

1. Use of a shape memory polyurethane in the preparation of a biological stent, said shape memory polyurethane being polymerized from a diisocyanate, a soft segment polymer and a linear polymer having a molecular weight of 20,000-150,000, polymerized in a molar ratio of (1.2-8) : 1 : (0.2-7); The soft segment polymer is polylactic acid, polyglycolic acid, polycaprolactone, polyhydric alcohol or a copolymer of at least two of them.

2. Use according to claim 1, characterized in that, The soft segment polymer is represented as HO-R-OH, and the structural formula of the shape memory polyurethane is shown as Formula I: wherein x is selected from 1-10, and y is selected from 1-10. R is a repeat unit of the soft segment polymer; repeating units of diisocyanates, or repeating units of copolymers of diisocyanates with polyols.

3. Use according to claim 1 or 2, characterized in that, The molecular weight of the soft segment polymer is 1000-10000.

4. Use according to claim 1, characterized in that, The soft segment polymer is a polymer of lactic acid and polyhydric alcohol.

5. Use according to claim 4, characterized in that, The molar ratio of the repeating units of lactic acid and the repeating units of polyhydric alcohol in the soft segment polymer is (10-102):(1-20).

6. Use according to claim 5, characterized in that, The structural formula of the soft segment polymer is shown as Formula II: wherein m and n are independently selected from 4-50, and r is selected from 1-20.

7. Use according to claim 1 or 2, characterized in that, The diisocyanate is selected from aliphatic diisocyanate or aromatic diisocyanate, the aliphatic diisocyanate including hexamethylene diisocyanate, lysine diisocyanate, isophorone diisocyanate, dicyclohexylmethane diisocyanate, and the aromatic diisocyanate including at least one of toluene diisocyanate or diphenylmethane diisocyanate.

8. Use according to claim 7, characterized in that, The is:

9. Use according to claim 1, characterized in that, The biological stent is a ureteral stent.

10. Use according to claim 1, characterized in that, The biological stent is obtained by rolling the tube after melt extrusion or hot pressing of the shape memory polyurethane.

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