Application of a zwitterionic polymer injectable hydrogel as a vitreous substitute

Abstract

This invention relates to the field of materials science and technology, and discloses the application of zwitterionic polymer injectable hydrogels as vitreous substitutes. Zwitterionic monomers selected from CBUIA, CBUTA, CBOH, CBMA, or MPC are dissolved in an aqueous phase, and polymerization is initiated by an initiator to obtain a hydrogel. After swelling equilibrium, the zwitterionic polymer injectable hydrogel is obtained. This invention uses initiator-initiated free radical polymerization of monomers and prepares physically cross-linked pure zwitterionic hydrogels through multi-hydrogen bond interactions or chain entanglement. The pure zwitterionic hydrogel with injectable properties is prepared through swelling equilibrium. It exhibits good biocompatibility, which is beneficial for improving the affinity of this zwitterionic polymer-based hydrogel vitreous substitute to the vitreous cavity, reducing adverse reactions after implantation. Furthermore, the preparation method is simple and the conditions are mild, making it more suitable for large-scale promotion and use as a vitreous substitute in ocular surgery, and it exhibits excellent biofouling resistance.

Description

Technical Field

[0001] This invention relates to the field of materials science and technology, specifically to the application of an amphoteric polymer injectable hydrogel as a vitreous substitute. Background Technology

[0002] The vitreous body is a transparent gel-like substance that fills the vitreous cavity between the lens and the retina. It is primarily composed of hyaluronic acid and collagen, and is a highly hydrated, avascular extracellular gel matrix. It functions to provide refractive power, support the retina, and regulate intraocular oxygen and pressure. With increasing age and the occurrence of accidents, the incidence of vision-threatening diseases such as rhegmatogenous retinal detachment, severe diabetic retinopathy, penetrating ocular trauma, macular holes, and proliferative vitreoretinopathy increases annually, seriously affecting patients' quality of life. Vitrectomy-retinal surgery is an effective treatment for blinding fundus diseases; however, because the vitreous body lacks regenerative capacity, postoperative implantation of an artificial vitreous substitute is necessary to provide intraocular pressure and prevent retinal detachment and optic nerve damage.

[0003] Currently, commonly used vitreous substitutes in clinical practice mainly include perfluorocarbon liquid, silicone oil, and inert expanding gas. Although silicone oil and expanding gas have been proven to be effective filling materials, they have certain side effects as vitreous substitutes and may not be ideal treatment options for patients with eye diseases. Silicone oil filling can cause blurred vision, and patients need to maintain a face-down posture for extended periods. Furthermore, silicone oil can emulsify, leading to problems such as increased intraocular pressure and inflammation. Long-term silicone oil filling requires additional removal surgery; otherwise, it may increase the risk of cataracts and glaucoma. The side effects of expanding gas mainly include postoperative increased intraocular pressure, cataracts, foveal sensitivity, and corneal endothelial changes. Simultaneously, due to the difference in refractive index between the gas and eye tissue, it may cause temporary visual impairment. These side effects reduce the therapeutic effect of vitreous substitutes.

[0004] Therefore, an ideal vitreous substitute should meet the following requirements as much as possible: (1) good biocompatibility with surrounding tissues; (2) colorless and transparent. Its viscoelasticity, density, and refractive index are similar to those of natural vitreous; (3) certain surface tension to effectively support the retina; (4) long-term stability in vivo; (5) easy to operate, and can be injected into the vitreous cavity with a small needle; (6) suitable for intraocular filling in retinal detachment surgery. In recent years, some in-situ cross-linked polymer hydrogels with high water content and transparency have been explored as vitreous substitutes. Such hydrogels are both injectable and stable, able to maintain a constant swelling rate, remain stable for a long time, and maintain normal intraocular pressure without affecting light transmission. However, these polymers are prone to degradation or foreign body reactions after implantation, thus limiting their application as long-term vitreous substitutes. Inflammation and fibrosis caused by exogenous materials are manifestations of rejection reactions in vivo and are natural manifestations of mammalian self-protection mechanisms. Polyethylene glycol (PEG), as a hydrophilic and biocompatible polymer, has been widely studied to improve bioinertness and reduce immunogenicity. However, the degradation of PEG in vivo and potential anti-PEG immune responses may reduce its physiological retention time. Zwitterionic polymers exhibit excellent biofouling properties due to their superior surface hydration; long-term implantation does not trigger foreign body reactions, fibrous capsule formation, or immune responses. Studies have reported the use of injectable hydrogels containing zwitterionic polymers for vitreous replacement. However, the introduction of non-zwitterionic components into zwitterionic polymers may reduce the material's antifouling performance; simultaneously, chemically cross-linked zwitterionic polymers may cause the chemical bonds in the polymer network to break under high shear forces, thereby reducing the material's mechanical and optical properties. Summary of the Invention

[0005] Based on this, the present invention provides an injectable hydrogel vitreous substitute based on multi-hydrogen bond interactions or chain entanglement of an ultrapure zwitterionic polymer, aiming to solve the problems of insufficient antifouling performance, excessively rapid degradation rate, poor biocompatibility, and poor optical properties of existing hydrogels after injection. This injectable hydrogel, through optimized molecular structure, enhances the material's stability and biocompatibility while improving its antifouling performance, thus better meeting the requirements of vitreous substitutes.

[0006] To achieve the above objectives, the present invention provides an application of zwitterionic polymer injectable hydrogel as a vitreous substitute, comprising: dissolving zwitterionic monomers with structures shown in formulas (1), (2), (3), (4), and (5) in an aqueous phase, and polymerizing carbon-carbon double bonds by initiating an initiator to obtain a hydrogel; subsequently, swelling the hydrogel in phosphate buffered saline (PBS), physiological saline, or deionized water to finally obtain a zwitterionic polymer injectable hydrogel.

[0007]

[0008] The zwitterionic monomers with structures shown in formulas (1), (2), (3), (4), and (5) are polymerized sequentially to form zwitterionic polymers with the following molecular formulas:

[0009]

[0010] The Chinese names of the zwitterionic monomers and corresponding polymers with the structures shown in formulas (1), (2), (3), (4), and (5) of this invention are as follows:

[0011] The zwitterionic monomer of formula (1) is carboxybetaine urea acrylate (CBUIA), and its polymer is polycarboxybetaine urea acrylate (PCBUIA).

[0012] The zwitterionic monomer of formula (2) is carboxybetaine carbamate acrylate (CBUTA), and its polymer is polycarboxybetaine carbamate acrylate (PCBUTA).

[0013] The zwitterionic monomer of formula (3) is 2-((2-hydroxy-3-(methacryloyloxy)propyl)dimethylammonium)acetate (CBOH), and its polymer is 2-poly((2-hydroxy-3-(methacryloyloxy)propyl)dimethylammonium)acetate (PCBOH);

[0014] The zwitterionic monomer of formula (4) is 3-[[2-(methacryloyloxy)ethyl]dimethylammonium]propionate (CBMA), and its polymer is poly3-[[2-(methacryloyloxy)ethyl]dimethylammonium]propionate (PCBMA);

[0015] The zwitterionic monomer of formula (5) is 2-methacryloyloxyethyl phosphorylcholine (MPC), and its polymer is poly-2-methacryloyloxyethyl phosphorylcholine (PMPC).

[0016] Preferably, one of the zwitterionic monomers in the structures shown in formulas (1), (2), (3), (4), and (5) is dispersed in an aqueous phase, and a carbon-carbon double bond is polymerized by an initiator to obtain a hydrogel. The solid content of the hydrogel is 0.30–0.60 g / ml, 0.30–0.70 g / ml, 0.30–0.70 g / ml, 0.35–0.70 g / ml, and 0.40–0.80 g / ml, respectively. When the zwitterionic monomers of formulas (1), (2), (3), (4), and (5) are used in combination, the solid content of the hydrogel is preferably 0.35–0.60 g / ml, for example, 0.35 g / ml, 0.40 g / ml, 0.45 g / ml, 0.50 g / ml, 0.55 g / ml, and 0.60 g / ml.

[0017] Preferably, the initiator is an ultraviolet (UV) photoinitiator or a thermal initiator, wherein: the UV photoinitiator is selected from 2-hydroxy-2-methyl-1-phenyl-1-propanone, 2-hydroxy-4'-(2-hydroxyethoxy)-2-methylphenylpropanone, or benzoyl peroxide; the thermal initiator is selected from organic peroxides, azo compounds, or persulfates, and the corresponding polymerization reaction temperature is 40-80℃, such as 40℃, 45℃, 50℃, 65℃, 70℃, etc.

[0018] The zwitterionic polymer injectable hydrogel of the present invention can be prepared by the following method:

[0019] Step 1: Dissolve the zwitterionic monomer in deionized water, mix well, add a photoinitiator or a thermal initiator, and stir and vortex to obtain a homogeneous solution.

[0020] Step 2: Irradiate the mixed solution under ultraviolet light or at a suitable temperature to initiate the reaction, then demold to obtain a zwitterionic polymer hydrogel;

[0021] Step 3: Immerse the zwitterionic polymer injectable hydrogel obtained in Step 2 in a buffer solution and allow it to swell and reach equilibrium for several days to obtain the zwitterionic polymer injectable hydrogel.

[0022] The method for preparing zwitterionic polymer injectable hydrogels as described above involves mixing zwitterionic monomers with deionized water in a ratio of 0.2g to 0.6g: 0.8ml to 0.4ml, for example, 0.2g: 0.8ml, 0.3g: 0.7ml, 0.4g: 0.6ml, 0.5g: 0.5ml, 0.6g: 0.4ml, etc.

[0023] In the preparation method of the zwitterionic polymer injectable hydrogel described above, the molar amount of photoinitiator in the mixed solution is 0.1% to 1% of the molar amount of zwitterionic monomers, for example, 0.1%, 0.3%, 0.5%, 0.8%, 1%, etc.

[0024] In the preparation method of the zwitterionic water polymer injectable gel described above, the photoinitiator is 2-hydroxy-2-methyl-1-phenyl-1-propanone, 2-hydroxy-4'-(2-hydroxyethoxy)-2-methylphenylpropanone, or benzoyl peroxide, preferably 2-hydroxy-2-methyl-1-phenyl-1-propanone; the polymerization reaction time is 2400–4800 s, preferably 2400–3600 s.

[0025] The method for preparing zwitterionic polymer injectable hydrogels as described above, wherein the thermal initiator is an organic peroxide, an azo compound, or a persulfate, preferably one of benzoyl peroxide, azobisisobutyronitrile, or potassium persulfate; the polymerization reaction temperature is 40–80°C, preferably 60–70°C; and the polymerization reaction time is 20–60 minutes, preferably 30–50 minutes.

[0026] In the preparation method of the zwitterionic polymer injectable hydrogel described above, the swelling equilibrium solution is phosphate buffered saline (PBS), physiological saline, or deionized water, preferably PBS.

[0027] In the preparation method of the zwitterionic polymer injectable hydrogel described above, the swelling equilibrium time is 48h to 120h, preferably 72h; the swelling equilibrium temperature is 20 to 40℃, preferably 37℃.

[0028] Compared with the prior art, the present invention can achieve the following beneficial effects:

[0029] 1) This invention provides a simple method for preparing zwitterionic polymer injectable hydrogels. The zwitterionic supramolecular polymer hydrogel is obtained through free radical polymerization. The mechanical properties of the hydrogel can be controlled by adjusting the monomer solid content in the reaction system; that is, the mechanical properties of the hydrogel can be changed according to actual application needs. Furthermore, the zwitterionic polymer hydrogel prepared after swelling equilibrium is injectable. Physical cross-linking through multiple hydrogen bonds or chain entanglement between polymer molecules gives it shear-thinning properties, enabling it to be injectable and self-healing under external force. This invention uses high-purity zwitterionic polymers, which, compared to traditional techniques, eliminates the need for chemical cross-linking agents and avoids the introduction of other small molecule monomers.

[0030] 2) The zwitterionic polymer injectable hydrogel provided by this invention has a multi-hydrogen bond or chain entanglement structure, which can not only be injected into the vitreous cavity through minimally invasive injection, but also maintain self-healing and long-term stability without degradation after injection into the vitreous cavity; through formulation optimization, after the hydrogel swells and reaches equilibrium, it can maintain a low swelling rate for a long time to maintain intraocular pressure stability, and can also support the retina and provide a clear light path, making it suitable as a vitreous substitute.

[0031] 3) The zwitterionic polymer injectable hydrogel provided by this invention has good biocompatibility, which is beneficial to improving the affinity of this zwitterionic polymer-based hydrogel vitreous substitute to the vitreous cavity and reducing adverse reactions after implantation. At the same time, the preparation method is simple and the conditions are mild, making it more suitable for large-scale promotion and use as a vitreous substitute in ocular surgery, and it can exhibit excellent biofouling resistance. Attached Figure Description

[0032] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments.

[0033] Figure 1 The shear thinning properties of PCUIA hydrogels with different solid contents in Example 1 are shown.

[0034] Figure 2 The changes in intraocular pressure in each group within 28 days after vitrectomy.

[0035] Figure 3 The results are from slit-lamp examinations 7 days and 1 month post-surgery.

[0036] Figure 4 The results are fundus images taken 7 days and 1 month post-surgery.

[0037] Figure 5 These are the OCT test results at 7 days and 1 month post-surgery.

[0038] The objectives, features, and advantages of this invention will be further explained in conjunction with the embodiments and with reference to the accompanying drawings. Detailed Implementation

[0039] The specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are for illustration and explanation only and are not intended to limit the present invention.

[0040] Unless otherwise defined, the technical terms used in the following embodiments have the same meanings as commonly understood by those skilled in the art to which this invention pertains. Unless otherwise specified, the experimental reagents used in the following embodiments are conventional biochemical reagents; and the experimental methods described are conventional methods.

[0041] Example 1: Preparation of four groups of vitreous substitutes with different solid contents

[0042] Different masses of carboxylate betaine urea acrylate (CBUIA) monomers (0.3g, 0.35g, 0.40g, and 0.45g) were dissolved in 0.7ml, 0.65ml, 0.60ml, and 0.55ml of deionized water, respectively. 1% (as a percentage of the monomer molar ratio) of 2-hydroxy-2-methyl-1-phenyl-1-propanone (1173 photoinitiator) was added, and the solutions were placed in an ultraviolet crosslinking chamber and irradiated for 3600s. Photoinitiated free radical polymerization yielded hydrogels of pure zwitterionic supramolecular polymers with different solid contents. The hydrogels were then placed in PBS solution to reach swelling equilibrium. The resulting injectable hydrogel samples were designated as: PCCUIA-30, PCCUIA-35, PCCUIA-40, and PCCUIA-45, respectively.

[0043] Performance tests were conducted on the zwitterionic polymer injectable hydrogels prepared from the three groups of hydrogels with different solid contents, as vitreous substitutes.

[0044] Natural vitreous humor possesses high equilibrium water content, high light transmittance, and specific refractive index and density. For vitreous substitutes, maintaining a high equilibrium water content helps preserve the vitreous's viscoelasticity, while maintaining high light transmittance allows light from the anterior segment of the eye to pass smoothly through the vitreous humor to the retina, preserving visual function. A refractive index and density similar to natural vitreous humor can reduce postoperative refractive and postural correction, minimizing patient discomfort. As a long-term vitreous substitute, the hydrogel's physical properties must be similar to those of natural vitreous humor. Therefore, the following tests were conducted:

[0045] (1) First, the basic properties of a series of hydrogels after swelling equilibrium were tested, with silicone oil as a control group. The results are summarized in Table 1. As shown in Table 1, natural vitreous gels can achieve a water content of over 98%, a density of 1.0053-1.0089, and a refractive index of 1.3345-1.3348. In contrast, PCPUIA hydrogels have a water content range of 95-98%, a transmittance of 85-90% in the wavelength range of 300-800nm, a refractive index of 1.3345-1.3389, and a density of 1.013-1.021. These properties are close to those of natural vitreous gels, which meets the requirements for vitreous gel substitutes.

[0046] Table 1 Optical and physical properties of PCPUIA hydrogel and silicone oil

[0047]

[0048]

[0049] For vitreous replacements, sufficient surface tension to seal the location of the retinal tear and to flatten the detached retina through swelling reaction force is crucial. Typically, the surface tension of the human vitreous in the liquid phase is 47.8 ± 3.8 mN / m. -1 As shown in Table 2, the average surface tension of the PCPUIA hydrogel is 44-70 mN / m. -1 The surface tension of PCUIA hydrogel is much greater than that of (silicone oil) SO, while the surface tension of PCUIA hydrogel is close to that of human vitreous body.

[0050] Table 2 Surface tension of PCPUIA hydrogel and silicone oil

[0051]

[0052] To evaluate whether the hydrogel is suitable for direct injection into the vitreous cavity, a rheological analysis of the PCPUIA hydrogel was performed, such as... Figure 1 As shown in Table 3. Figure 1 The hydrogel shown exhibits shear-thinning properties, demonstrating its self-healing ability; it can self-heal into a single unit after being extruded through a syringe.

[0053] Table 3 Storage modulus of PCPUIA hydrogel

[0054]

[0055] (2) The cell compatibility of the hydrogel was investigated using mouse fibroblasts (L929). As shown in Table 4, the cell survival rate of the hydrogel was above 95%, indicating that the hydrogel has good cell compatibility.

[0056] Table 4. Cell compatibility of PCPUIA hydrogel

[0057]

[0058] Fifteen healthy male New Zealand white rabbits were randomly divided into three groups of five rabbits each: a PCPUIA hydrogel group, a silicone oil (SO) group, and a hyaluronic acid (HA) group. SO is a commonly used vitreous substitute in clinical practice, while HA served as a gel control material. Preoperatively, the rabbits were anesthetized by intramuscular injection of xylazine hydrochloride and salbutamol 50, mydriasis was achieved using compound tropicamide eye drops, and topical anesthesia was performed using oxybuprofen hydrochloride eye drops.

[0059] The vitreous humor, which occupies two-thirds of the eyeball's volume, is crucial for maintaining intraocular pressure. Postoperative intraocular pressure monitoring can also indirectly assess whether the hydrogel is compressing the retina. Therefore, it is important to test intraocular pressure one month postoperatively. Figure 2 As shown, within two weeks, the intraocular pressure (IOP) in both the SO group and the PCPUIA hydrogel group experienced a decrease followed by a gradual return to normal. The temporary decrease in IOP postoperatively can be attributed to the minimally invasive 23G vitrectomy, consistent with previously reported early postoperative IOP hypotension. The subsequent natural return of IOP to normal also confirms that the early hypotension was surgically induced, and further indicates that the PCPUIA hydrogel material does not cause postoperative high IOP leading to glaucoma or other ophthalmic diseases. However, the IOP in the HA group was significantly lower than that in the normal control group after two weeks, which may be related to HA degradation; further monitoring of IOP in the later stages is needed. Figure 3 As shown, slit-lamp observation was performed on animals 7 days and 1 month post-surgery. No obvious inflammation was observed in any group, the lens and anterior vitreous remained transparent, and the fundus showed normal red light reflex. Figure 4 , Figure 5As shown, fundus photography and OCT were used to assess changes in the rabbit eyes at 7 days and 1 month postoperatively. Fundus photography showed that the retinas in the PCPUIA hydrogel group and the silicone oil group were orange-red, without hemorrhage, exudation, or vascular tortuosity and dilation. However, the HA group showed blurred images, which may be due to intraocular inflammation caused by the degradation products of HA. OCT results showed that the retinal structure was intact, the reflected light band was smooth and clear, and there were no pathological problems such as edema, hemorrhage, or structural disorder. This indicates that PCPUIA hydrogel, as a vitreous substitute, exhibits excellent biocompatibility and does not significantly damage the retinal structure.

[0060] (3) In order to further demonstrate the beneficial effects of the present invention, based on Example 1, other zwitterionic polymer injectable hydrogels with different solid contents were prepared by changing the zwitterionic monomer types, and their performance as glass substitutes was tested using the same method. The zwitterionic monomer types, solid contents and related test data are summarized in Table 5.

[0061] Table 5

[0062]

[0063] As shown in Table 1, the PCPUTA, PCBOH, PCBMA, and PMPC hydrogels of this invention all achieve performance comparable to that of the PCPUTA hydrogel. The high water content of the PCPUTA, PCPUTA, PCBOH, PCBMA, and PMPC hydrogels prepared in this invention ensures osmotic pressure balance within the eye, preventing tissue dehydration; their visible light transmittance is close to the light transmission requirements of the cornea and lens; by regulating the polymer's hydrophilicity-hydrophobicity balance, their surface tension is similar to that of the natural vitreous body, ensuring compatibility with intraocular tissues (such as the retina) and preventing interfacial peeling; density matching ensures long-term stability after intraocular filling; and their excellent biocompatibility meets the requirements for long-term implantation. The prepared hydrogels are highly compatible with the natural vitreous body in terms of solid content, water content, optical properties, interfacial characteristics, and biocompatibility.

[0064] While specific embodiments of the present invention have been described above, those skilled in the art should understand that these are merely illustrative examples, and various changes or modifications can be made to these embodiments without departing from the principles and essence of the present invention. The scope of protection of the present invention is defined only by the appended claims.

Claims

1. Use of an injectable hydrogel of a zwitterionic polymer as a vitreous substitute, characterized in that, The injectable hydrogel of the zwitterionic polymer is prepared by dissolving at least one of the zwitterionic monomers shown in formula (1), (2), (3), (4), (5) in an aqueous phase, and initiating polymerization of the carbon-carbon double bond by an initiator to obtain a hydrogel, and then swelling and equilibrating the hydrogel in a phosphate buffered saline solution, physiological saline or deionized water to obtain the hydrogel; Formula (1) Formula (2) Formula (3) Formula (4) Formula (5).

2. Use of a zwitterionic polymeric injectable hydrogel according to claim 1 as a vitreous substitute, characterized in that, The use amount ratio of the zwitterionic monomer to deionized water is 0.2 g-0.6 g: 0.8 ml-0.4 ml.

3. Use of a zwitterionic polymeric injectable hydrogel according to claim 1 as a vitreous substitute, characterized in that, The use amount of the initiator is 0.1%-1% of the molar amount of the zwitterionic monomer.

4. Use of a zwitterionic polymeric injectable hydrogel according to claim 1 as a vitreous substitute, characterized in that, The initiator is a UV initiator or a thermal initiator, wherein: The UV initiator is 2-hydroxy-2-methyl-1-phenyl-1-propanone or 2-hydroxy-4'-(2-hydroxyethoxy)-2-methylpropiophenone. The thermal initiator is an organic peroxide, an azo compound or a persulfate.

5. Use of a zwitterionic polymeric injectable hydrogel according to claim 4 as a vitreous substitute, characterized in that, During the polymerization process initiated by the initiator, the corresponding polymerization reaction temperature of the UV initiator is 20-40 ℃, and the corresponding polymerization reaction temperature of the thermal initiator is 40-80 ℃.

6. Use of a zwitterionic polymeric injectable hydrogel according to claim 1 as a vitreous substitute, characterized in that, The reaction time of the polymerization process initiated by the initiator is 2400-4800 s.

7. Use of a zwitterionic polymeric injectable hydrogel according to claim 1 as a vitreous substitute, characterized in that, The swelling equilibration time is 3 d-21 d; and / or, the swelling equilibration temperature is 20-40 ℃.

8. Use of a zwitterionic polymeric injectable hydrogel according to any one of claims 1 to 7 as a vitreous substitute, characterized in that, One of the zwitterionic monomers shown in formula (1), (2), (3), (4), (5) is dissolved in an aqueous phase, and a hydrogel is obtained by initiating polymerization of the carbon-carbon double bond by an initiator, and the solid content of the hydrogel is 0.30-0.60 g / ml, 0.30-0.70 g / ml, 0.30-0.70 g / ml, 0.35-0.70 g / ml, 0.40-0.80 g / ml, respectively.

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