A kind of NHS active ester modified polycitrate and its preparation method and application

Abstract

The present invention relates to an NHS active ester modified polycitrate and its preparation method and application. Citric acid and 1,8-octanediol, or citric acid, 1,8-octanediol and polyethylene glycol or poloxamer are reacted through melt polycondensation to prepare polycitrate, and polycitrate is reacted with N-hydroxysuccinimide to prepare NHS active ester modified polycitrate. The NHS active ester modified polycitrate can be used to prepare hydrogel adhesives, wet coacervate adhesives, dry coacervate adhesives, etc. When the NHS active ester modified polycitrate of the present invention is used, the NHS active ester modified polycitrate can be dissolved in water by adjusting the pH of the solution, and is safe to use. The bonding process can be completed without adding an oxidant. The dry adhesive can be prepared into a patch for use, utilizing the higher carrying capacity of the carrier to improve the bonding strength and blocking effect of the adhesive.

Description

Technical Field

[0001] The invention belongs to the technical field of tissue adhesives and relates to an NHS active ester modified polycitrate and a preparation method and application thereof. Background Art

[0002] The closure method for wounds and defects in human tissue directly impacts the restoration of their structure and function. Traditional wound closure methods primarily rely on mechanical closure methods such as suturing, clamping, and stapling. However, these methods are associated with complications due to fluid and air leakage, difficulty in accessing certain locations, postoperative removal, and cumbersome and time-consuming surgical procedures. Tissue adhesives, however, are readily available and are widely used in surgical wound closure, hemostasis, tissue sealing, microbial barrier, postoperative adhesion prevention, and implant fixation. Currently, clinically used tissue adhesives primarily include fibrin glue, α-cyanoacrylate glue, PEG glue, and polyurethane glue. These adhesives have demonstrated promising results in sealing, hemostasis, and assisting mechanical closure with leak prevention. However, their application is significantly limited by safety concerns, restricting them to skin surfaces, or by low wet bond strength, preventing them from being used for tensile tissue closure. Therefore, the development of biocompatible tissue adhesives with high wet bond strength to replace traditional mechanical closure methods holds great promise for clinical application.

[0003] Citric acid and diol monomers can be synthesized through melt polycondensation in the absence of catalysts to produce viscous polycitrate. Due to the abundance of hydroxyl and carboxyl groups on its macromolecules, polycitrate can form a network-like bioelastomer through thermal crosslinking. This bioelastomer exhibits excellent flexibility and deformability, has good biological evaluation, and has tunable mechanical properties that are compatible with tissues, making it a promising tissue repair material. Furthermore, it exhibits strong adhesion to soft tissues such as skin. A literature report (DOI 10.1007 / s10856-015-5649-2) reports that catechol groups can be introduced through a one-step melt polycondensation to form a polycitrate-based mussel biomimetic soft tissue adhesive. This adhesive exhibits high tissue adhesion strength and holds great potential for application. However, strong oxidants such as sodium periodate are required to promote curing and bonding. The presence of oxidants can produce cytotoxicity, compromising its safety in vivo. Furthermore, these adhesives, despite their high bonding strength, are generally hydrophobic and can only be dissolved in organic solvents, which also compromises their safety for human use.

[0004] Therefore, it is of great significance to develop a new polycitrate-based tissue adhesive that does not require an oxidant, is easy to use, and has water solubility and high wet bonding strength. Summary of the Invention

[0005] In order to solve the problems existing in the prior art, the present invention provides an NHS active ester modified polycitrate and its preparation method and application;

[0006] To achieve the above object, the present invention adopts the following scheme:

[0007] An NHS active ester modified polycitrate, the main chain of which includes citric acid units and 1,8-octanediol units, and the side groups are grafted with NHS active ester groups;

[0008] The molar ratio of the citric acid unit to the 1,8-octanediol unit is 1.0-2.5; and the grafting rate of the NHS active ester group is 5-30 wt%.

[0009] As the preferred technical solution:

[0010] An NHS active ester modified polycitrate as described above, wherein the main chain further comprises a polyethylene glycol (PEO) unit or a poloxamer unit;

[0011] The molar ratio of the PEO unit or the poloxamer unit to the 1,8-octanediol unit is not greater than 2.3. The PEO unit or the poloxamer unit can be used to adjust the hydrophilicity and hydrophobicity of the molecular structure.

[0012] The NHS active ester-modified polycitrate as described above has an acid dissociation constant (pKa) of 2 to 3. The NHS active ester-modified polycitrate can be completely dissolved in water with a pH of 3 to 7 (the pH of the system is adjusted to 3 to 7 with an alkali). This is because when the pH of the system is adjusted to 3 to 7 with an alkali, the carboxyl groups contained therein are deprotonated, allowing the NHS active ester-modified polycitrate to be completely dissolved in water.

[0013] One of the technical problems addressed by the present invention is to provide a modified polycitrate for adhesion to human tissue surfaces. NHS active esters have high reactivity and can react with amino groups at room temperature and without a catalyst. Therefore, NHS active ester-modified polycitrate can exhibit tissue adhesion on human tissue surfaces by chemically bonding with amino groups in proteins. Furthermore, compounds containing diamino or polyamino groups can be used as crosslinking agents to crosslink linear NHS active ester-modified polycitrate to form a stable three-dimensional network structure, thereby improving the mechanical properties of the NHS active ester-modified polycitrate. Polycitrate is generally soluble only in organic solvents such as ethanol, acetone, and dioxane; it is not completely soluble in water and is prone to phase separation in water. However, the preparation of water-soluble polycitrate is of great significance in the biomedical field. Literature generally suggests that water solubility can be achieved by introducing highly water-soluble diols, such as PEO or poloxamer units, into the structure. However, this method of improving water solubility increases the complexity of the preparation process on the one hand, and dissolution in water can only be achieved when the molar ratio of the introduced hydrophilic unit to the 1,8-octanediol unit exceeds 7 / 3. The introduction of a large number of hydrophilic units changes the structure of the polycitrate, especially when used in a wet environment, the swelling degree increases and the mechanical properties decrease. After a large number of experimental investigations, the present invention creatively discovered that it is not necessary to change the chemical structure of the polycitrate, and the phase-separated polycitrate can be converted into a uniform and transparent polycitrate aqueous solution by simply adjusting the pH value of the water system. Analysis shows that this is because the chemical structure of the polycitrate contains carboxyl groups. Under slightly acidic conditions, the carboxyl groups are protonated, and the molecular chains attract each other through hydrophobic interaction, which manifests as phase separation from water on a macroscopic scale. However, as the pH value increases, the carboxyl groups are deprotonated and carry a negative charge, thereby generating electrostatic repulsion between the polycitrate molecular chains, causing the molecular chains to stretch, which manifests as complete dissolution on a macroscopic scale.

[0014] The present invention also provides a method for preparing NHS active ester modified polycitrate, comprising the following steps:

[0015] (1) preparing polycitrate by melt polycondensation reaction of citric acid and 1,8-octanediol, or further citric acid, 1,8-octanediol and polyethylene glycol (PEO) or poloxamer (PEO-PPO-PEO);

[0016] The molar ratio of the carboxyl group of citric acid to the hydroxyl group of the remaining reaction raw materials is 1.5 to 3.75:1;

[0017] When the reaction raw materials include polyethylene glycol or poloxamer, the molar ratio of 1,8-octanediol to polyethylene glycol or poloxamer is 0.3 to 1:1;

[0018] (2) Polycitrate and N-hydroxysuccinimide (NHS) are reacted in acetone solvent in the presence of a dehydrating agent, N,N-dicyclohexylcarbodiimide (DCC). There is no special requirement for the amount of acetone solvent used, as long as the reactants are completely dissolved. After the reaction, the product is purified by filtration, precipitation with ice ether, and dissolution in acetone to obtain NHS active ester-modified polycitrate.

[0019] The second technical problem to be solved by the present invention is to provide a method for preparing and purifying NHS active ester modified polycitrate.

[0020] Polycitrate is a polyester prepared by melt polycondensation of citric acid (containing three carboxyl groups and one hydroxyl group) and diol (containing two hydroxyl groups). By controlling the feed ratio of citric acid to diol, that is, the ratio of carboxyl groups to hydroxyl groups, the hydroxyl groups of the diol with higher reactivity react preferentially when there is an excess of carboxyl groups. The hydroxyl groups in the citric acid with lower reactivity then slowly participate in the polycondensation reaction, consuming the hydroxyl groups. Combined with controlling the reaction time to regulate the carboxyl group content, a polycitrate with a certain number of carboxyl groups and no active hydroxyl groups can be obtained.

[0021] Polycitrate with a defined carboxyl content is treated with N-hydroxysuccinimide (NHS) in the presence of the dehydrating agent N,N-dicyclohexylcarbodiimide (DCC). An esterification reaction occurs between the carboxyl groups on the polycitrate and the hydroxyl groups on the NHS, resulting in the grafting of NHS active ester groups onto the pendant groups of the polycitrate molecule. By controlling the ratio of carboxyl content to the amount of NHS added, the amount of NHS active ester groups grafted onto the citrate can be controlled.

[0022] The reactants (polycitrate and NHS) undergo a coupling reaction under the action of the dehydrating agent DCC to generate a product (NHS active ester-modified polycitrate). However, after the reaction, the reaction system includes the two reactants, the dehydrating agent, the product, and by-products, which require purification. Experimental exploration has found that the by-products are insoluble in acetone and can be removed by filtration; the reactants, dehydrating agent, and product are all soluble in acetone; the product is not soluble in glacial ether, while the unreacted monomer and dehydrating agent are soluble in glacial ether. Therefore, taking advantage of the different solubility of the product in glacial ether and acetone, the present invention uses filtration, glacial ether precipitation, and acetone dissolution to purify the product. No peaks of reactants and by-products are found in the 600M nuclear magnetic resonance hydrogen spectrum.

[0023] As the preferred technical solution:

[0024] The method for preparing the NHS active ester modified polycitrate as described above, wherein the melting temperature in step (1) is 160° C., the polycondensation reaction temperature is 140° C., and the polycondensation reaction time is 1 to 10 hours;

[0025] In step (2), the reaction temperature is 10-40° C. and the reaction time is 6-24 h;

[0026] In step (2), the molar ratio of N-hydroxysuccinimide to N,N-dicyclohexylcarbodiimide is 1:1, and the molar ratio of N-hydroxysuccinimide to polycitrate carboxyl is 0.1 to 1.5.

[0027] The present invention also provides an application of NHS active ester modified polycitrate, wherein an aqueous solution of NHS active ester modified polycitrate is used as component A, and an aqueous solution of a natural molecule containing multiple amino groups is used as component B. Components A and B are mixed to form an in-situ hydrogel adhesive; the molar ratio of the amino groups in component B to the NHS groups in component A is 0.2 to 0.8;

[0028] Natural molecules containing polyamino groups are polylysine, cystine, chitosan, hydroxypropyl chitosan, carboxymethyl chitosan, gelatin, collagen or silk protein;

[0029] The lap-shear bond strength of the hydrogel adhesive tested according to YYT0729.1-2009 is 20 to 100 KPa.

[0030] The third technical problem to be solved by the present invention is to provide a type of two-component synthetic soft tissue adhesive. The hydrogel adhesive belongs to the category of water-based glue. The materials used are safe, it has in situ injectability, and has excellent bonding properties. The lap-shear bonding strength of the hydrogel adhesive tested in accordance with YYT0729.1-2009 is 20 to 100 KPa, which is better than the currently commercial fibrin glue. The bonding mechanism of the hydrogel adhesive: On the one hand, the NHS active ester group in component A and the amino group in component B form a stable amide bond through a chemical reaction, causing the body of the hydrogel adhesive to crosslink and solidify; on the other hand, the NHS active ester group in component A and the amino group on the surface of the adherend (tissue) form a stable amide bond through a chemical reaction, which enables the hydrogel adhesive to have adhesion ability at the interface. The bulk crosslinking and curing of the hydrogel adhesive and the interface adhesion process are carried out simultaneously.

[0031] As the preferred technical solution:

[0032] The specific preparation steps of the hydrogel adhesive using the NHS active ester modified polycitrate as described above are as follows:

[0033] (1) adding NHS active ester modified polycitrate to deionized water, adjusting the pH of the aqueous solution to 3-7 and then dissolving the solution to obtain an aqueous solution of NHS active ester modified polycitrate with a concentration of 10-50 wt%;

[0034] (2) dissolving the natural molecule containing polyamino groups in deionized water to obtain an aqueous solution of the natural molecule containing polyamino groups having a concentration of 10 to 50 wt %;

[0035] (3) The aqueous solution of NHS active ester modified polycitrate and the aqueous solution of natural molecules containing polyamino groups are mixed on the surface of the adherend to react and form a hydrogel adhesive.

[0036] The present invention also provides an application of NHS active ester modified polycitrate, wherein an aqueous solution of the NHS active ester modified polycitrate is mixed with an aqueous solution of tannic acid (TA) to form a wet coagulant adhesive; the aqueous solution of the NHS active ester modified polycitrate is obtained by adding the NHS active ester modified polycitrate to deionized water, adjusting the pH of the aqueous solution to 3-7, and then dissolving the solution; the concentration of the aqueous solution of the NHS active ester modified polycitrate is 10-50 wt %; the concentration of the aqueous solution of the tannic acid is 10-30 wt %; and the mass ratio of the NHS active ester modified polycitrate to the tannic acid is 0.25-4.

[0037] The fourth technical problem addressed by the present invention is to provide a single-component synthetic soft tissue adhesive. This coacervate adhesive is simple to prepare, incorporates tannic acid components to impart antioxidant and antibacterial properties, and possesses self-healing properties through dynamic hydrogen bonds within its structure. The wet coacervate adhesive is also injectable, while the dry coacervate adhesive facilitates storage and is convenient to use.

[0038] The wet coacervate adhesive can be directly injected into the tissue defect to achieve bonding or sealing effects; the dry coacervate adhesive can be sprayed on the surface of the tissue defect, absorbing water from the surface water layer to restore to the wet coacervate adhesive and produce bonding or sealing effects.

[0039] The bonding mechanism of the dry coagulant adhesive is as follows: on the one hand, the bulk cohesion is restored after absorbing surface water; on the other hand, the NHS active ester groups in the coagulant adhesive react with the amino groups on the tissue surface to form stable amide bonds, generating adhesion at the interface, and the adhesion is further enhanced through the hydrogen bonding and hydrophobic effect formed between tannic acid and the tissue surface.

[0040] NHS active ester-modified polycitrate and TA form a cohesive gelling agent through hydrogen bonding and hydrophobic interactions. Water plays a key role in this system, including plasticization and hydrogen bonding. Unlike NHS active ester-modified polycitrate, the cohesive adhesive forms a solid upon dehydration and drying, whereas NHS active ester-modified polycitrate remains a viscous liquid after drying. This means that TA, acting as a crosslinker, crosslinks the NHS active ester-modified polycitrate, forming a network structure and enhancing cohesion. A higher TA content results in a denser network and higher rigidity, but also results in brittle properties. Therefore, the dried gel is brittle and can be mechanically crushed into a fine powder. However, when the fine powder of the cohesive adhesive absorbs water, the water acts as a plasticizer and hydrogen bond donor, promoting self-healing of the cohesive structure, restoring cohesion and generating adhesive properties.

[0041] As the preferred technical solution:

[0042] In the application of the NHS active ester modified polycitrate as described above, the wet coacervate adhesive is sequentially subjected to vacuum freeze drying or vacuum drying and mechanical crushing to form a dry coacervate adhesive; further, the dry coacervate adhesive is dissolved in a volatile organic solvent and then coated on a carrier, and dried to form a self-adhesive patch;

[0043] The mechanical crushing method is ball milling or low temperature (-196 ~ 0 ℃) crushing method;

[0044] The T-type bonding strength of the self-adhesive patch tested in accordance with YYT0729.2-2009 is ≥1N / cm;

[0045] The dry coagulation adhesive is dissolved in a volatile organic solvent to obtain a solution concentration of 10 to 50 wt %;

[0046] The volatile organic solvent is methanol, acetone, dioxane or tetrahydrofuran;

[0047] The coating method is spin coating, dip coating or spray coating;

[0048] The drying temperature is 25-80℃.

[0049] The application of the NHS active ester modified polycitrate as described above is to dissolve the wet coacervate adhesive in an organic solvent to control the concentration to be 10-50 wt%, and spray-dry to obtain a dry coacervate adhesive;

[0050] The organic solvent is methanol, acetone, dioxane, tetrahydrofuran or N,N-dimethylformamide.

[0051] The fifth technical problem to be solved by the present invention is to provide a medical self-adhesive patch, which is easy to use and has good bonding and sealing properties. The T-type bonding strength tested according to YYT0729.2-2009 is ≥1N / cm, which is better than commercially available fibrin glue and is similar to the strongest liquid bandage currently reported.

[0052] The bonding mechanism of the self-adhesive patch is as follows: on the one hand, when the patch comes into contact with a wet tissue surface, the adhesive layer restores its intrinsic cohesion due to water absorption; on the other hand, the NHS active ester groups in the adhesive layer chemically react with the amino groups on the tissue surface to form stable amide bonds, generating adhesion at the interface, and further enhancing the adhesion through the hydrogen bonding and hydrophobic effect formed between tannic acid and the tissue surface; thirdly, the mechanical bearing capacity of the carrier is utilized to further enhance the bonding strength.

[0053] Beneficial effects

[0054] (1) The NHS active ester modified polycitrate of the present invention has a linear structure and can be dissolved in water by adjusting the pH of the solution, making it safe to use;

[0055] (2) In the preparation process of the NHS active ester modified polycitrate of the present invention, the content of the NHS active ester group of the NHS active ester modified polycitrate can be controlled by controlling the carboxyl content in the melt polycondensation and controlling the amount of N-hydroxysuccinimide in the coupling reaction;

[0056] (3) When the NHS active ester modified polycitrate of the present invention is used, the NHS active ester modified polycitrate, the natural molecule containing polyamino groups or tannic acid are dissolved in water, which is safe and non-toxic;

[0057] (4) When the NHS active ester modified polycitrate of the present invention is used, the bonding process can be completed without adding an oxidant;

[0058] (5) The dry coagulant adhesive prepared in the application of the present invention is easy to store and can be directly sprayed on the wound, making it convenient to use;

[0059] (6) The dry coacervate adhesive prepared in the application of the present invention absorbs water on the tissue surface to promote close contact with the tissue surface, while using the adsorbed water to restore the cohesion of the body and promote chemical bonding with the tissue surface. No external substances are required, and it is safe and efficient.

[0060] (7) The dry coagulant adhesive prepared in the application of the present invention can be prepared into a patch for use, and the higher load-bearing capacity of the carrier is utilized to improve the bonding strength and sealing effect of the adhesive. BRIEF DESCRIPTION OF THE DRAWINGS

[0061] Figure 1This is the hydrogen nuclear magnetic resonance spectrum of the purified NHS active ester modified polycitrate in Example 4. DETAILED DESCRIPTION

[0062] Below in conjunction with specific embodiment, further set forth the present invention.Should be understood that these embodiments are only used to illustrate the present invention and are not used in limiting the scope of the present invention.In addition, should be understood that after reading the content taught by the present invention, those skilled in the art can make various changes or modifications to the present invention, and these equivalent forms fall equally within the scope limited by the appended claims of the application.

[0063] In the embodiment of the present invention, polyethylene glycol: Mn=400; poloxamer is Pluronic L64.

[0064] Example 1

[0065] A method for preparing NHS active ester modified polycitrate, comprising the following steps:

[0066] (1) Citric acid, 1,8-octanediol, and polyethylene glycol (PEO) were melted at 160°C, and then polycondensed at 140°C for 4 h to prepare polycitrate;

[0067] The molar ratio of the carboxyl group of citric acid to the hydroxyl group of the other reaction raw materials is 1.5:1; the molar ratio of PEO to 1,8-octanediol is 1;

[0068] (2) Polycitrate and N-hydroxysuccinimide (NHS) were reacted in acetone at 10°C for 6 h in the presence of N,N-dicyclohexylcarbodiimide (DCC). After the reaction, the product was purified by filtration, precipitation with glacial ether, and dissolution in acetone to obtain NHS active ester-modified polycitrate.

[0069] The molar ratio of N-hydroxysuccinimide to N,N-dicyclohexylcarbodiimide is 1:1, and the molar ratio of N-hydroxysuccinimide to polycitrate carboxyl group is 0.1.

[0070] The grafting rate of NHS active ester groups in the prepared NHS active ester modified polycitrate is 5wt%; the acid dissociation constant of the NHS active ester modified polycitrate is 2-3; and the NHS active ester modified polycitrate can be completely dissolved in water with a pH value of 3-7.

[0071] Example 2

[0072] A method for preparing NHS active ester modified polycitrate, comprising the following steps:

[0073] (1) Citric acid, 1,8-octanediol, and polyethylene glycol (PEO) were melted at 160°C, and then polycondensed at 140°C for 2 h to prepare polycitrate;

[0074] The molar ratio of the carboxyl group of citric acid to the hydroxyl group of the other reaction raw materials is 3.75:1; the molar ratio of PEO to 1,8-octanediol is 0.1;

[0075] (2) Polycitrate and N-hydroxysuccinimide (NHS) are reacted in acetone at 40°C for 24 hours in the presence of N,N-dicyclohexylcarbodiimide (DCC). After the reaction, the product is purified by filtration, precipitation with glacial ether, and dissolution in acetone to obtain NHS active ester-modified polycitrate.

[0076] The molar ratio of N-hydroxysuccinimide to N,N-dicyclohexylcarbodiimide is 1:1, and the molar ratio of N-hydroxysuccinimide to polycitrate carboxyl group is 1.5.

[0077] The grafting rate of NHS active ester groups in the prepared NHS active ester modified polycitrate is 30 wt %; the acid dissociation constant of the NHS active ester modified polycitrate is 2-3; and the NHS active ester modified polycitrate can be completely dissolved in water with a pH value of 3-7.

[0078] Example 3

[0079] A method for preparing NHS active ester modified polycitrate, comprising the following steps:

[0080] (1) Citric acid, 1,8-octanediol, and poloxamer (PEO-PPO-PEO) were melted at 160°C, and then polycondensed at 140°C for 10 h to prepare polycitrate;

[0081] The molar ratio of the carboxyl group of citric acid to the hydroxyl group of the other reaction raw materials is 2.5:1; the molar ratio of poloxamer to 1,8-octanediol is 2;

[0082] (2) Polycitrate and N-hydroxysuccinimide (NHS) were reacted in acetone at 30°C for 18 hours in the presence of N,N-dicyclohexylcarbodiimide (DCC). After the reaction, the product was purified by filtration, precipitation with glacial ether, and dissolution in acetone to obtain NHS active ester-modified polycitrate.

[0083] The molar ratio of N-hydroxysuccinimide to N,N-dicyclohexylcarbodiimide is 1:1, and the molar ratio of N-hydroxysuccinimide to polycitrate carboxyl group is 1.

[0084] The grafting rate of NHS active ester groups in the prepared NHS active ester modified polycitrate is 20 wt %; the acid dissociation constant of the NHS active ester modified polycitrate is 2-3; and the NHS active ester modified polycitrate can be completely dissolved in water with a pH value of 3-7.

[0085] Example 4

[0086] A method for preparing NHS active ester modified polycitrate, comprising the following steps:

[0087] (1) Citric acid, 1,8-octanediol, and polyethylene glycol (PEO) were melted at 160°C, and then polycondensed at 140°C for 6 h to prepare polycitrate;

[0088] The molar ratio of the carboxyl group of citric acid to the hydroxyl group of the other reaction raw materials is 2:1; the molar ratio of PEO to 1,8-octanediol is 2.3;

[0089] (2) Polycitrate and N-hydroxysuccinimide (NHS) were reacted in acetone at 25°C for 6 h in the presence of N,N-dicyclohexylcarbodiimide (DCC). After the reaction, the product was purified by filtration, precipitation with ice ether, and dissolution with acetone to obtain NHS active ester modified polycitrate. Its H NMR spectrum is shown in Figure 2. Figure 1 As shown;

[0090] The molar ratio of N-hydroxysuccinimide to N,N-dicyclohexylcarbodiimide is 1:1, and the molar ratio of N-hydroxysuccinimide to polycitrate carboxyl group is 0.8.

[0091] The grafting rate of NHS active ester groups in the prepared NHS active ester modified polycitrate is 15 wt %; the acid dissociation constant of the NHS active ester modified polycitrate is 2-3; and the NHS active ester modified polycitrate can be completely dissolved in water with a pH value of 3-7.

[0092] Example 5

[0093] A method for preparing NHS active ester modified polycitrate, comprising the following steps:

[0094] (1) Citric acid, 1,8-octanediol, and polyethylene glycol (PEO) were melted at 160°C, and then polycondensed at 140°C for 6 h to prepare polycitrate;

[0095] The molar ratio of the carboxyl group of citric acid to the hydroxyl group of the other reaction raw materials is 2:1; the molar ratio of PEO to 1,8-octanediol is 2.3;

[0096] (2) Polycitrate and N-hydroxysuccinimide (NHS) were reacted in acetone at 25°C for 6 hours in the presence of N,N-dicyclohexylcarbodiimide (DCC). After the reaction, the product was purified by filtration, precipitation with glacial ether, and dissolution in acetone to obtain NHS active ester-modified polycitrate.

[0097] The molar ratio of N-hydroxysuccinimide to N,N-dicyclohexylcarbodiimide is 1:1, and the molar ratio of N-hydroxysuccinimide to polycitrate carboxyl group is 1.

[0098] The grafting rate of NHS active ester groups in the prepared NHS active ester modified polycitrate is 22 wt %; the acid dissociation constant of the NHS active ester modified polycitrate is 2-3; and the NHS active ester modified polycitrate can be completely dissolved in water with a pH value of 3-7.

[0099] Example 6

[0100] A method for preparing NHS active ester modified polycitrate, comprising the following steps:

[0101] (1) Citric acid, 1,8-octanediol, and polyethylene glycol (PEO) were melted at 160°C, and then polycondensed at 140°C for 6 h to prepare polycitrate;

[0102] The molar ratio of the carboxyl group of citric acid to the hydroxyl group of the other reaction raw materials is 2:1; the molar ratio of PEO to 1,8-octanediol is 2.3;

[0103] (2) Polycitrate and N-hydroxysuccinimide (NHS) were reacted in acetone at 25°C for 6 hours in the presence of N,N-dicyclohexylcarbodiimide (DCC). After the reaction, the product was purified by filtration, precipitation with glacial ether, and dissolution in acetone to obtain NHS active ester-modified polycitrate.

[0104] The molar ratio of N-hydroxysuccinimide to N,N-dicyclohexylcarbodiimide is 1:1, and the molar ratio of N-hydroxysuccinimide to polycitrate carboxyl group is 1.2.

[0105] The grafting rate of NHS active ester groups in the prepared NHS active ester modified polycitrate is 25wt%; the acid dissociation constant of the NHS active ester modified polycitrate is 2-3; and the NHS active ester modified polycitrate can be completely dissolved in water with a pH value of 3-7.

[0106] Example 7

[0107] A method for preparing NHS active ester modified polycitrate, comprising the following steps:

[0108] (1) Citric acid and 1,8-octanediol were melted at 160°C, and then polycondensed at 140°C for 1 hour to prepare polycitrate;

[0109] (2) Polycitrate and N-hydroxysuccinimide (NHS) were reacted in acetone at 20°C for 10 h in the presence of N,N-dicyclohexylcarbodiimide (DCC). After the reaction, the product was purified by filtration, precipitation with glacial ether, and dissolution in acetone to obtain NHS active ester-modified polycitrate.

[0110] The molar ratio of N-hydroxysuccinimide to N,N-dicyclohexylcarbodiimide is 1:1, and the molar ratio of N-hydroxysuccinimide to polycitrate carboxyl group is 1.

[0111] The grafting rate of NHS active ester groups in the prepared NHS active ester modified polycitrate is 23wt%; the acid dissociation constant of the NHS active ester modified polycitrate is 2-3; and the NHS active ester modified polycitrate can be completely dissolved in water with a pH value of 3-7.

[0112] Example 8

[0113] An application of NHS active ester modified polycitrate, the specific steps are as follows:

[0114] (1) Preparation of raw materials:

[0115] NHS active ester modified polycitrate prepared in Example 1;

[0116] Natural molecules containing multiple amino groups: polylysine;

[0117] (2) adding the NHS active ester modified polycitrate to deionized water, adjusting the pH of the aqueous solution to 4, and then dissolving the solution to obtain an aqueous solution of the NHS active ester modified polycitrate with a concentration of 50 wt%;

[0118] (3) dissolving the natural molecule containing polyamino groups in deionized water to obtain an aqueous solution of the natural molecule containing polyamino groups having a concentration of 50 wt %;

[0119] (4) An aqueous solution of NHS active ester modified polycitrate and an aqueous solution of a natural molecule containing multiple amino groups are mixed on the surface of the adherend to react and form a hydrogel adhesive; wherein the molar ratio of the amino groups in the aqueous solution of the natural molecule containing multiple amino groups to the NHS groups in the aqueous solution of NHS active ester modified polycitrate is 0.2.

[0120] The lap-shear bond strength of the hydrogel adhesive tested according to YYT0729.1-2009 is 20KPa.

[0121] Example 9

[0122] An application of NHS active ester modified polycitrate, the specific steps are as follows:

[0123] (1) Preparation of raw materials:

[0124] NHS active ester modified polycitrate prepared in Example 2;

[0125] Natural molecules containing multiple amino groups: polylysine;

[0126] (2) adding the NHS active ester modified polycitrate to deionized water, adjusting the pH of the aqueous solution to 4.5, and then dissolving the solution to obtain an aqueous solution of the NHS active ester modified polycitrate with a concentration of 50 wt%;

[0127] (3) dissolving the natural molecule containing polyamino groups in deionized water to obtain an aqueous solution of the natural molecule containing polyamino groups having a concentration of 30 wt %;

[0128] (4) An aqueous solution of NHS active ester modified polycitrate and an aqueous solution of a natural molecule containing multiple amino groups are mixed on the surface of the adherend to react and form a hydrogel adhesive; wherein the molar ratio of the amino groups in the aqueous solution of the natural molecule containing multiple amino groups to the NHS groups in the aqueous solution of NHS active ester modified polycitrate is 0.6.

[0129] The lap-shear bond strength of the hydrogel adhesive tested according to YYT0729.1-2009 is 100KPa.

[0130] Example 10

[0131] An application of NHS active ester modified polycitrate, the specific steps are as follows:

[0132] (1) Preparation of raw materials:

[0133] NHS active ester modified polycitrate prepared in Example 3;

[0134] Natural molecules containing polyamino groups: hydroxypropyl chitosan;

[0135] (2) adding the NHS active ester modified polycitrate to deionized water, adjusting the pH of the aqueous solution to 5, and then dissolving the solution to obtain an aqueous solution of the NHS active ester modified polycitrate with a concentration of 10 wt%;

[0136] (3) dissolving the natural molecule containing polyamino groups in deionized water to obtain an aqueous solution of the natural molecule containing polyamino groups having a concentration of 10 wt %;

[0137] (4) The aqueous solution of NHS active ester modified polycitrate and the aqueous solution of natural molecules containing polyamino groups are mixed on the surface of the adherend to react and form a hydrogel adhesive; wherein the molar ratio of amino groups in the aqueous solution of natural molecules containing polyamino groups to NHS groups in the aqueous solution of NHS active ester modified polycitrate is 0.8.

[0138] The lap-shear bond strength of the hydrogel adhesive tested according to YYT0729.1-2009 is 45KPa.

[0139] Example 11

[0140] An application of NHS active ester modified polycitrate, the specific steps are as follows;

[0141] (1) Preparation of raw materials:

[0142] NHS active ester modified polycitrate prepared in Example 4;

[0143] Tannic acid (TA);

[0144] (2) adding the NHS active ester modified polycitrate to deionized water, adjusting the pH of the aqueous solution to 4.3, and then dissolving the solution to obtain an aqueous solution of the NHS active ester modified polycitrate with a concentration of 10 wt %;

[0145] (3) dissolving tannic acid in deionized water to obtain an aqueous solution of tannic acid with a concentration of 10 wt %;

[0146] (4) an aqueous solution of NHS active ester modified polycitrate is mixed with an aqueous solution of tannic acid (TA) to form a wet cohesive adhesive; wherein the mass ratio of NHS active ester modified polycitrate to tannic acid is 0.25;

[0147] (5) The wet coacervate adhesive is subjected to vacuum freeze drying and ball milling to form a dry coacervate adhesive;

[0148] (6) The dry coacervate adhesive was dissolved in methanol to obtain a solution with a concentration of 10 wt % and then spin-coated on a polyurethane film. After drying at 25° C., a self-adhesive patch was formed.

[0149] The T-type bonding strength of the self-adhesive patch tested according to YYT0729.2-2009 is 1N / cm.

[0150] Example 12

[0151] An application of NHS active ester modified polycitrate, the specific steps are as follows;

[0152] (1) Preparation of raw materials:

[0153] NHS active ester modified polycitrate prepared in Example 5;

[0154] Tannic acid (TA);

[0155] (2) adding the NHS active ester modified polycitrate to deionized water, adjusting the pH of the aqueous solution to 4.6, and then dissolving the solution to obtain an aqueous solution of the NHS active ester modified polycitrate with a concentration of 50 wt%;

[0156] (3) dissolving tannic acid in deionized water to obtain an aqueous solution of tannic acid with a concentration of 30 wt %;

[0157] (4) an aqueous solution of NHS active ester modified polycitrate is mixed with an aqueous solution of tannic acid (TA) to form a wet cohesive adhesive; wherein the mass ratio of NHS active ester modified polycitrate to tannic acid is 2;

[0158] (5) The wet coacervate adhesive is dissolved in acetone to a concentration of 50 wt %, and spray-dried to obtain a dry coacervate adhesive.

[0159] The prepared dry coacervate adhesive is placed in a powder spray bottle and directly sprayed on the tissue defect to seal the wound.

[0160] Example 13

[0161] An application of NHS active ester modified polycitrate, the specific steps are as follows;

[0162] (1) Preparation of raw materials:

[0163] NHS active ester modified polycitrate prepared in Example 6;

[0164] Tannic acid (TA);

[0165] (2) adding the NHS active ester modified polycitrate to deionized water, adjusting the pH of the aqueous solution to 4.2, and then dissolving the solution to obtain an aqueous solution of the NHS active ester modified polycitrate with a concentration of 20 wt %;

[0166] (3) dissolving tannic acid in deionized water to obtain an aqueous solution of tannic acid with a concentration of 20 wt %;

[0167] (4) an aqueous solution of NHS active ester modified polycitrate is mixed with an aqueous solution of tannic acid (TA) to form a wet cohesive adhesive; wherein the mass ratio of NHS active ester modified polycitrate to tannic acid is 4;

[0168] (5) The wet coacervate adhesive is subjected to vacuum freeze drying and ball milling to form a dry coacervate adhesive;

[0169] (6) The dry coacervate adhesive was dissolved in acetone to obtain a solution with a concentration of 50 wt % and then sprayed on a polyurethane film. After drying at 30° C., a self-adhesive patch was formed.

[0170] The T-type bonding strength of the self-adhesive patch tested according to YYT0729.2-2009 is 1.5N / cm.

Claims

1. An application of NHS active ester modified polycitrate, characterized by: The aqueous solution of NHS active ester modified polycitrate is mixed with the aqueous solution of tannic acid to form a wet cohesive adhesive; The main chain of NHS active ester modified polycitrate includes citric acid unit and 1,8-octanediol unit, and the side groups are grafted with NHS active ester group; The molar ratio of the citric acid unit to the 1,8-octanediol unit is 1.0 to 2.5; the grafting rate of the NHS active ester group is 5 to 30 wt%; The aqueous solution of NHS active ester modified polycitrate is prepared by adding NHS active ester modified polycitrate to deionized water, adjusting the pH of the aqueous solution to 3-7, and then dissolving the solution. The concentration of the aqueous solution of NHS active ester modified polycitrate is 10-50 wt %; the concentration of the aqueous solution of tannic acid is 10-30 wt %. The mass ratio of NHS active ester modified polycitrate to tannic acid is 0.25-4.

2. The use of a NHS active ester modified polycitrate according to claim 1, characterized in that: The NHS active ester modified polycitrate backbone further comprises polyethylene glycol units or poloxamer units; The molar ratio of the polyethylene glycol unit or the poloxamer unit to the 1,8-octanediol unit is not greater than 2.

3.

3. The use of a NHS active ester modified polycitrate according to claim 1 or 2, characterized in that: The acid dissociation constant of the NHS active ester modified polycitrate is 2 to 3; the NHS active ester modified polycitrate can be completely dissolved in water with a pH of 3 to 7.

4. The use of a NHS active ester modified polycitrate as claimed in claim 1 or 2, characterized in that: The preparation method of NHS active ester modified polycitrate comprises the following steps: (1) preparing polycitrate by melt polycondensation reaction of citric acid and 1,8-octanediol, or further citric acid, 1,8-octanediol and polyethylene glycol or poloxamer; The molar ratio of the carboxyl group of citric acid to the hydroxyl group of the remaining reaction raw materials is 1.5 to 3.75:1; When the reaction raw materials include polyethylene glycol or poloxamer, the molar ratio of 1,8-octanediol to polyethylene glycol or poloxamer is 0.3 to 1:1; (2) Polycitrate and N-hydroxysuccinimide are reacted in acetone solvent in the presence of a dehydrating agent, N,N-dicyclohexylcarbodiimide. After the reaction, the product is purified by filtration, precipitation with ice ether, and dissolution with acetone to obtain NHS active ester-modified polycitrate.

5. The use of a NHS active ester modified polycitrate according to claim 4, characterized in that: In step (1), the melting temperature is 160° C., the polycondensation reaction temperature is 140° C., and the polycondensation reaction time is 1 to 10 hours; In step (2), the reaction temperature is 10-40° C. and the reaction time is 6-24 h; In step (2), the molar ratio of N-hydroxysuccinimide to N,N-dicyclohexylcarbodiimide is 1:1, and the molar ratio of N-hydroxysuccinimide to polycitrate carboxyl is 0.1 to 1.

5.

6. The use of a NHS active ester modified polycitrate according to claim 1, characterized in that: The wet coacervate adhesive is subjected to vacuum freeze drying or vacuum drying and mechanical crushing to form a dry coacervate adhesive; further, the dry coacervate adhesive is dissolved in a volatile organic solvent and then coated on a carrier, and dried to form a self-adhesive patch; The mechanical pulverization method is ball milling or low temperature pulverization; The T-type bonding strength of the self-adhesive patch tested in accordance with YYT0729.2-2009 is ≥1N / cm; The dry coagulation adhesive is dissolved in a volatile organic solvent to obtain a solution concentration of 10 to 50 wt %; The volatile organic solvent is methanol, acetone, dioxane or tetrahydrofuran; The coating methods are spin coating, dip coating or spray coating.

7. The use of a NHS active ester modified polycitrate according to claim 1, characterized in that: The wet coacervate adhesive is dissolved in an organic solvent to a concentration of 10 to 50 wt%, and spray-dried to obtain a dry coacervate adhesive; The organic solvent is methanol, acetone, dioxane, tetrahydrofuran or N,N-dimethylformamide.

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