CN1176978C - A kind of degradable chemically cross-linked hydrogel and preparation method thereof - Google Patents

Abstract

The present invention relates to chemically crosslinked hydrogel having degradability and a preparation method thereof. The hydrogel belongs to the technical field of high molecular materials. The hydrogel is formed in a water phase at the body temperature (or the normal temperature) by a macromolecular monomer technology by adopting a hydrophilic or partially hydrophilic macromolecule or an oligomer as a main body combined with a degradable oligomer. The hydrogel is insoluble in water (chemically crosslinked), but the hydrogel is controllably degradable. The hydrogel can be widely suitable for the biologic material fields of cell culture brackets for tissue engineering, or drug controlled release carriers, etc.

Description

A kind of degradable chemically cross-linked hydrogel and preparation method thereof

technical field

The invention belongs to the technical field of polymer materials, and in particular relates to a chemically cross-linked hydrogel with degradation properties and a preparation method thereof.

technical background

The degradation products of polymers with degradation characteristics are low molecular weight compounds or eventually metabolized into small molecular compounds such as CO ₂ and H ₂ O, etc. If the degradation product is water-soluble, it can be directly excreted or absorbed by the body through various metabolic processes; if the degradation product is insoluble in water and has a large molecular weight, it can be further degraded by lysosomes through the phagocytosis of macrophages, thus It may cause sterile inflammatory reaction and has certain toxicity.

Biodegradable polymers have been widely used in the medical field (such as medical sutures, bone nails, plastic surgery and medicine, etc.) and as drug carriers to achieve controlled release of drugs in specific parts of the body for therapeutic purposes. The most widely studied and used biodegradable polymers are aliphatic polyesters, such as poly D, L-lactide (PDLLA), poly L-lactide (PLLA), polyglycolide (PGA), polyhexamethylene Lactones (PCL) and their copolymers. Chinese invention patent (publication number CN1271742A) synthesizes glycolide-L-lactide-caprolactone terpolymer, which has good biodegradability, mechanical properties and adjustable biodegradation speed. The Chinese invention patent (publication number CN1272384A) adopts the phase separation method to prepare the chitosan/gelatin porous cell scaffold material, which has good biocompatibility and can be pre-shaped in the field of tissue engineering, but the above-mentioned biomaterials do not have injectable properties. sex.

Hydrogel has good biocompatibility, the most widely studied and used is polyethylene glycol (PEG) or polyethylene oxide (PEO) and polypropylene oxide (PPO) copolymer (PEPO), low molecular weight ( ~10KDa) polyethylene glycol (PEG) or PEPO is easily excreted through the kidneys after being dissolved in the body. It is non-toxic, non-antigenic and immunogenic, and has been widely used in the fields of biomedicine and biotechnology. Appropriate hydrogel preparation methods can pre-mix ungelled polymer substances with cells or drugs, and then form a gel after injection into the human or animal body to naturally fix the cells or drugs, so it is also called injectable Hydrogels are generally physically cross-linked hydrogels. Even if it does not take advantage of its injectability, this kind of gel has the advantages of good biocompatibility, easy operation, and sufficient fixation of cells or drugs, so it has been widely valued in the fields of medical treatment and drug controlled release. US Patent No. 6,129,761 reported adding cross-linking agents such as divalent cations to modified polysaccharide compounds such as hyaluronic acid and alginate aqueous solutions to form hydrogels, which act as cell culture scaffolds in tissue engineering. However, the dissolution or degradation of physically cross-linked hydrogels is difficult to control. When used in in vitro tissue culture and other occasions, experiments cannot be carried out because they can be dissolved in water. A.S.Sawhney et al. (Macromolecules, 1993, 26, 581 [US]) prepared polyethylene glycol (PEG) macromonomers, which were cross-linked by ultraviolet or visible light to form chemically cross-linked hydrogels, and further discussed this Potential for hydrogels to be used as drug controlled release vehicles. However, it is inconvenient to use photoinitiation for tissue engineering and other occasions that need to be injected into the body; for larger gels, it is difficult to achieve uniformity in light and the resulting cross-linking reaction.

Contents of the invention

The object of the present invention is to propose a degradable chemically cross-linked hydrogel with good biocompatibility, water absorption and permeability and a preparation method thereof.

The degradable chemically cross-linked hydrogel proposed by the present invention is composed of hydrophilic or partially hydrophilic macromolecules or oligomers and degradable groups through chemical cross-linking. It is a polymer network structure, and its degradation rate It does not depend on the conditions of the formed gel and is independently controllable. Its chemical structural formula is:

表示处于任意形式化学交联点之间的链段。In the formula

Indicates a chain segment between arbitrary formal chemical cross-links.

(Y'-X') represents any form of copolymer composed of X' and Y', X' is a hydrophilic or partially hydrophilic macromolecule or oligomer, Y' is a degradable unit or its oligomer thing.

In the chemically cross-linked hydrogel of the present invention, hydrophilic or partially hydrophilic macromolecules or oligomers X' are the main body, accounting for 51%-99.5% (weight percent), degradable units or oligomers thereof Y' accounts for 49%-0.5% (percentage by weight). The water phase in the chemically cross-linked hydrogel is pure water, or buffer solution, or animal, plant or human body fluid, or tissue culture fluid, or other solvent media that do not contain organic solvents as the main body.

The present invention uses macromonomer technology to prepare the chemically cross-linked and degradable polymer hydrogel. Its preparation method is to use polyether hydrophilic or partially hydrophilic macromolecules or oligomers X with good biocompatibility as the central part of chemically cross-linked macromonomers, and combine them with biodegradable macromonomers by ring-opening polymerization. Aliphatic polyester Y is copolymerized to obtain a copolymer Y-X-Y; then a chemically crosslinkable double bond reactive group Z is connected to both ends of the main chain of the copolymer molecule to obtain a macromonomer Z-Y-X-Y-Z; a solution of a macromonomer is prepared, The cross-linking reaction is initiated by a water-soluble redox initiator to form a chemically cross-linked hydrogel. The hydrogel is insoluble in water at normal temperature (body temperature), but can be gradually degraded in a controlled manner, and is suitable for the fields of cell culture scaffolds for tissue engineering, drug controlled release carriers and the like.

In the above method, as the hydrophilic or partly hydrophilic macromolecule or oligomer X of the central part of the chemically crosslinked macromonomer, polyethylene glycol (PEO) with a molecular weight that is not too high can generally be used, and the molecular weight is from 100- 100000, or use PEPO block copolymer. Biodegradable aliphatic polyester Y can use oligomeric L-lactide (PLLA), oligomeric DL-lactide (PDLLA), oligomeric glycolide (PGA), oligomeric caprolactone (PCL) , any one of ε-alkyl substituted caprolactones, and any form of their copolymers. The chemically crosslinkable group Z can be acrylate, methacrylate, or other acrylate derivatives. The feed molar ratio between X and the monomer whose polymerization product is Y is 0.5:99.5-99.5:0.5.

In the above method, the conditions for ring-opening copolymerization of X and Y are: under 0.1mmHg vacuum and the action of a catalyst, the reaction temperature is 120°C-200°C, and the reaction time is 3-50 hours; the preferred reaction temperature is 140°C-160°C. The time is 15-24 hours, and the reaction product is Y-X-Y. Wherein, the catalyzer can adopt stannous isooctanoate, and its consumption is 0.1%-5% of the hydroxyl group mole number of X, and preferred consumption is 0.5%-1.5%; Catalyst also can use calcium hydride or zinc powder, its consumption and X The molar ratio of the hydroxyl groups of X is between 0.2:0.8-0.8:0.2, and the molar ratio of the preferred amount to the hydroxyl groups of X is 0.4:0.6-0.6:0.4.

In the above method, the copolymerization product Y-X-Y is dissolved in dichloromethane or chloroform, and the Y-X-Y solution reacts with Z (Z can be introduced by acryloyl chloride, methacryloyl chloride or other acryloyl chloride derivatives). The molar ratio of the amount of Z used to the hydroxyl groups of Y-X-Y is between 4:1-10:1. First add triethylamine in an equimolar amount to Z to the above Y-X-Y solution, add Z dropwise under stirring and nitrogen protection, react in an ice bath (0-5°C) for 10-12 hours, and then at room temperature (about 20°C) Under the reaction for 10-12 hours. After the reaction is completed, it is filtered and precipitated, and the precipitate is collected and vacuum-dried to obtain a macromonomer Z-Y-X-Y-Z.

In the above-mentioned method, the weight concentration of the solution of macromer Z-Y-X-Y-Z is 5-85%, and its solvent can be water, or buffer solution, or human body or animal and plant body fluid, or tissue culture fluid, or other not use organic solvent as One or more mixtures of the main solvent medium. The water-soluble redox initiator that adds in this macromolecular monomer solution can be persulfate, as potassium persulfate or ammonium persulfate etc., the consumption of initiator accounts for the 0.01-8% of macromolecular monomer solution weight, in Under the condition of 1-80°C, the cross-linking reaction is initiated to form a hydrogel.

The present invention has following characteristics:

1. The hydrogel proposed by the present invention is insoluble in water (chemical cross-linking), but can be degraded in normal temperature and water phase. Because polyethylene glycol or PEPO block copolymer is used as the central part of the macromonomer, the biocompatibility is good.

2. The degradation rate of the hydrogel prepared by the present invention in vivo can be adjusted by controlling factors such as the type and chemical composition of the copolyester, the length of the polyester chain, and the crosslinking density.

3. The hydrogel prepared by the present invention uses non-toxic, commercially available stannous isooctanoate or calcium hydride or zinc powder as a catalyst, and the equipment is simple. The chemical properties of the copolymer are modified by reacting acryloyl chloride or methacryloyl chloride or other acryloyl chloride derivatives with a copolymer of polyethylene glycol or PEPO and aliphatic polyester, and the post-reaction treatment is simple. It is beneficial to large-scale industrial production.

4. In the present invention, a water-soluble redox initiator is added to the macromonomer aqueous solution, and a cross-linking reaction is initiated at human body temperature or normal temperature, thereby immobilizing inclusions (cells or medicines).

5. The degradable chemically cross-linked hydrogel of the present invention is realized in normal temperature, normal pressure, and aqueous solution, and can be processed into various complex The shapes are used in medicine, tissue engineering or other applications, and the operation is simple and convenient.

6. The chemically cross-linked hydrogel of the present invention has good water absorption, permeability and biocompatibility, is a new type of artificially synthesized polymer hydrogel, and has a wide range of biomedical applications.

Detailed ways

Embodiments of the present invention are further described below through examples, but are not limited to these examples.

Example 1, the molar ratio of reactants is PEG10K: L-lactide: stannous octoate = 1:32:0.02 (see the last "note" for the description of PEG10K and other codes), and vacuumize at 60°C after mixing uniformly 6 hours to remove volatile matter, then replace with inert gas (nitrogen or argon) several times, and finally heat seal the ampoule tube under vacuum (0.1 mmHg). The copolymerization reaction was carried out at 140° C. for 24 hours. The dichloromethane solution of the copolymerization product is reacted with acryloyl chloride (molar ratio: 1:10), filtered after the reaction, and the filtrate is precipitated in anhydrous ether (-10~0°C), the precipitate is collected, and vacuum-dried to obtain a macromonomer PEG10K-L32. In this macromonomer phosphate buffer solution (PBS) with a weight concentration of 30%, add a redox initiator ammonium persulfate with a weight concentration of 2%, chemically cross-link at 37° C. to obtain a hydrogel. After the hydrogel reached swelling equilibrium in PBS solution at 37°C, the water absorption rate was 98%, and the volume swelling ratio was 3.7.

Embodiment 2, operation is the same as embodiment 1, and reactant feed molar ratio is PEG8K: ε-caprolactone: D, L-lactide: stannous octoate=1: 2: 2: 0.02, obtain macromolecular monomer PEG10K-CL2-DL2. Add redox initiator ammonium persulfate with a weight concentration of 2% to the macromer PBS solution with a weight concentration of 40%, and chemically cross-link at 37° C. to obtain a hydrogel. After the hydrogel reached swelling equilibrium in PBS solution at 37°C, the water absorption rate was 92%, and the volume swelling ratio was 3.5.

Embodiment 3, operation is the same as embodiment 1, the molar ratio of reactant feeding is PEO-PPO-PEO (block length ratio is EO: PO: EO=99: 65: 99): glycolide: stannous octoate=1 :8:0.02, the macromer PEO-PPO-PEO-G8 was obtained. The macromonomer PBS solution with a weight concentration of 30% was added with a redox initiator potassium persulfate with a weight concentration of 1%, and chemically cross-linked at 37° C. to obtain a hydrogel. After the hydrogel reached swelling equilibrium in PBS solution at 37°C, the water absorption rate was 80%, and the volume swelling ratio was 2.4.

Example 4, the operation is the same as in Example 1, the molar ratio of the reactants is PEG6K:D, L-lactide:CaH ₂ =1:8:2, the reaction temperature is 160°C, and the time is 15 hours to obtain macromolecules Monomer PEG6K-DL8. Be that 1% redox initiator ammonium persulfate is added in this macromer PBS solution that weight concentration is 25%, adopt RS75 type Rheometrics rheometer, under 37 ℃, constant humidity, carry out mechanical test ( Frequency 1Hz, stress 10N), after the chemical crosslinking reaction occurs, its static elastic modulus is 203KPa [comparison: 30wt% PEPO tri-block copolymer (block length ratio is EO:PO:EO=99:65:99) The PBS solution physically cross-links the hydrogel, and the static elastic modulus is 31KPa].

The chemically cross-linked hydrogel was subjected to an in vitro degradation experiment under the conditions of pH 7.4 phosphate buffer solution and 37°C, and the weight loss after degradation of the hydrogel was used to represent the degradation rate. The results are shown in Table 1.

Table 1 In vitro degradation performance of PEG6K-DL8 chemically cross-linked hydrogel

Degradation time (days) 0 2 12 19 25 33

Hydrogel weight loss (%) 0 0.5 44 84 95 99

Note: PEG2K, PEG6K, PEG8K, and PEG10K represent polyethylene glycols with molecular weights of 2,000, 6,000, 8,000, and 10,000, respectively.

Gn means that both ends of the polyethylene glycol molecular chain are connected with n glycolic acid ester units on average;

Ln means that both ends of the polyethylene glycol molecular chain are connected with n L-lactic acid copolymerization units on average;

DLn means that both ends of the polyethylene glycol molecular chain are connected with n D, L-lactic acid copolymerization units on average;

CLn means that both ends of the polyethylene glycol molecular chain are connected with n caprolactone copolymerization units on average.

Claims (11)

1. A degradable chemically cross-linked hydrogel, characterized in that it consists of a polymer chemically cross-linked network structure composed of hydrophilic or partially hydrophilic macromolecules or oligomers and degradable groups, and its degradation rate is lower than Depending on the conditions of the formed gel, it is independently controllable, and its chemical structural formula is abbreviated as:

In the formula: Indicates the chain segments between arbitrary formal chemical cross-links; (Y'-X') means any form of copolymer composed of X' and Y'; X' is a hydrophilic or partially hydrophilic macromolecule or oligomer; Y' is a degradable unit or its oligomer. 2. The chemically crosslinked hydrogel according to claim 1, characterized in that the hydrophilic or partially hydrophilic macromolecule or oligomer X' is the main body in the chemically crosslinked hydrogel, and the weight content is 51%-99.5%, and the weight content of the degradable unit or oligomer Y' in the chemically cross-linked hydrogel is 49%-0.5%. 3. The chemically cross-linked hydrogel according to claim 1, wherein the water phase is pure water or buffer solution or body fluid or tissue culture fluid or other solvent media not mainly composed of organic solvents. 4. A method for preparing a degradable chemically crosslinked hydrogel as claimed in claim 1, using macromonomer technology, characterized in that polyether X containing polyethylene glycol repeating units is used as the chemically crosslinked macromer The central part of the molecular monomer is copolymerized with the biodegradable aliphatic polyester Y by ring-opening polymerization to obtain the copolymer Y-X-Y; , to obtain macromolecular monomer Z-Y-X-Y-Z; prepare the solution of macromolecular monomer, trigger cross-linking reaction through water-soluble redox initiator, and form chemical cross-linked hydrogel; wherein, Y is poly DL-lactide, poly L- Any one of lactide, polyglycolide, polyε-caprolactone, ε-alkyl substituted caprolactone, and any form of copolymer of the above-mentioned types of polymers; Z is acrylate, methacrylic acid esters or other acrylate derivatives. 5. The preparation method of hydrogel according to claim 4, characterized in that X in the central part of the composed macromonomer is polyethylene glycol, the molecular weight is from 2000 to 10000, or it is polyethylene oxide and polypropylene oxide copolymer. 6. The preparation method of hydrogel according to claim 4, characterized in that the molar ratio of the copolymerization unit of the prepared macromonomer is X: the monomer whose polymerization product is Y is 0.5: 99.5-99.5: 0.5. 7. The preparation method of hydrogel according to claim 4, characterized in that the catalyst used in the copolymerization reaction is stannous isooctanoate, the amount of which is 0.1-5% of the mole number of hydroxyl groups of X, and the reaction temperature is 120 -160°C, the reaction time is 3-50 hours. 8. The preparation method of hydrogel according to claim 4, characterized in that the catalyst used in the copolymerization reaction is calcium hydride or zinc powder, and the molar ratio of its dosage to the hydroxyl group of X is 0.2:0.8-0.8:0.2 , the reaction temperature is 120-160° C., and the reaction time is 3-50 hours. 9. The preparation method of hydrogel according to claim 4, characterized in that the molar ratio of the amount of Z used to the hydroxyl groups of Y-X-Y is between 4:1-10:1. 10. The preparation method of hydrogel according to claim 4, characterized in that the weight concentration of the macromer solution is 5-85%, and its solvent is water, buffer solution, human body or animal and plant body fluid, tissue culture fluid 1. One or more mixtures of solvent media that do not use organic solvents as the main body. 11. The preparation method of hydrogel according to claim 10, characterized in that the added water-soluble redox initiator is persulfate, the dosage is 0.01-8% of the weight of the macromonomer solution, and the crosslinking reaction temperature 1-80°C.