CN113912864A

CN113912864A - Mussel foot protein-imitated modified lignin adhesion enhancing material and preparation method and application thereof

Info

Publication number: CN113912864A
Application number: CN202111250017.9A
Authority: CN
Inventors: 钱勇; 卢铭津; 邱学青; 杨东杰; 张艾程; 杨换仙; 楼宏铭
Original assignee: South China University of Technology SCUT
Current assignee: South China University of Technology SCUT
Priority date: 2021-10-26
Filing date: 2021-10-26
Publication date: 2022-01-11
Anticipated expiration: 2041-10-26
Also published as: CN113912864B

Abstract

The invention discloses a mussel foot protein-imitated modified lignin adhesion enhancing material and a preparation method and application thereof. According to the invention, firstly, an in-situ Lewis acid method is adopted to carry out structural modification on lignin, so that catechol structures in the lignin structures are obviously increased, and then residues such as Lys, Arg and the like are grafted at the ortho-position of a phenolic hydroxyl benzene ring through a Mannich reaction; or firstly grafting Lys, Arg and other residues at the ortho position of the phenolic hydroxyl benzene ring through a Mannish reaction, and then structurally modifying the lignin by adopting an in-situ Lewis acid method, thereby improving the biological adhesion performance of the lignin by utilizing the coulomb force-hydrophobic effect and the side chain antioxidation effect and obviously enhancing the acting force on skin tissues. Compared with common industrial alkali lignin, the mussel foot protein-like modified lignin adhesion reinforcing material disclosed by the invention enhances the acting force on skin tissues by 2.5-5.3 times, has an excellent adhesion reinforcing effect, and can be used for preparing a reinforcing material of an adhesion material.

Description

Mussel foot protein-imitated modified lignin adhesion enhancing material and preparation method and application thereof

Technical Field

The invention belongs to the field of fine chemicals, and particularly relates to a mussel foot protein-like modified lignin adhesion enhancing material, and a preparation method and application thereof.

Background

The adhesion with green, safety and high performance is the basis of accurate medical diagnosis and human-computer interaction, and nature endows a plurality of organisms with special molecular structures or micro-nano structures, so that the organisms have broad-spectrum and excellent adhesion performance. Since the super-strong adhesion performance of the mussel is reported for the first time in 1978, the mussel-like adhesive material is widely applied to the fields of materials, energy, environment and the like, and the material design is based on catechol adhesion enhancement modification inspired by mussel foot protein Mfps.

The broad spectrum adhesion mechanism of catechol structure is not well defined and typical explanations are four: 1) the phenolic hydroxyl forms strong coordination on the surfaces of the metal and the metal oxide to realize adhesion; 2) phenolic hydroxyl groups form hydrogen bonds on the surface of the inorganic nonmetal to realize adhesion; 3) benzene rings form pi-pi stacking hydrophobic effect on the surface of the organic polymer to realize adhesion; 4) the semiquinone free radical, the quinone and the amine group are subjected to Michael addition to generate Schiff base, so that adhesion is realized on the surface of an organism. As the research goes into, the actual situation is found to be different, and the situation is presumably related to other structures of the mussel foot adhesive protein. Therefore, the influence of the amino group, the mercapto group, and the like, which have been neglected in the past, on the adhesion is considered, and a new adhesion mechanism is proposed: coulomb force-hydrophobic effect, ion-pi effect, side chain antioxidant effect.

Dopamine with catechol structure has good biocompatibility and can be polymerized, and is the most common bionic mussel adhesion enhancing modifier at present. However, dopamine is industrially used as a drug intermediate and is relatively expensive, so that a more inexpensive dopamine substitute (Nanoscale,2020,12(3)) needs to be found, and lignin, which is used as a second major component and a unique aromatic polymer in plants, has great application potential. The lignin is connected with the hemicellulose in the plant cell wall through an ether bond, and is filled and bonded through the action of a hydrogen bond and the cellulose, so that the strength and the anti-erosion capability of the plant are improved. Therefore, the subject is to strengthen the adhesion function of lignin by grafting dopamine, and prepare the waterproof and impervious lignin-dopamine sunscreen microcapsule. Meanwhile, the lignin is a polymer formed by connecting three phenylpropane units of p-hydroxyphenylpropane, guaiacyl and syringyl through carbon-oxygen and carbon-carbon bonds, the guaiacyl and the syringyl can be changed into catechol structures through one-step demethylation modification, and the high-cost dopamine is expected to be replaced. However, three phenylpropane units in lignin molecules from different plant sources and at different parts of plants are distributed unevenly and connected differently, and the adhesion performance of catechol lignin prepared by simple demethylation needs to be improved, so that how to construct an adhesion structure of high-content mussel-foot-like protein to improve the adhesion performance of catechol lignin is an urgent problem to be solved.

Disclosure of Invention

In order to overcome the defects and shortcomings in the prior art, the invention aims to provide a preparation method of a mussel foot protein-like modified lignin adhesion enhancing material.

The lignin contains a large amount of aromatic methyl ether and the distribution mode of the functional groups is mainly ortho-position and vicinal-position, so the lignin has great potential for modifying the structure of catechol. The invention imitates the amino acid composition structure of Mfp-3, 5 and 6, firstly adopts an in-situ Lewis acid method to carry out structural modification on lignin, so that catechol structure in the lignin structure is obviously increased, and then Lys and Arg residues are grafted at the ortho position of a phenolic hydroxyl benzene ring through a Mannich reaction; or Lys and Arg residues are grafted at the ortho position of the phenolic hydroxyl benzene ring through a Mannish reaction, and then the lignin is structurally modified by adopting an in-situ Lewis acid method, so that the biological adhesion performance of the lignin is improved by utilizing the coulomb force-hydrophobic effect and the side chain antioxidant effect, and the acting force on skin tissues is obviously enhanced.

The invention also aims to provide the mussel foot protein-imitated modified lignin adhesion enhancing material prepared by the method.

The invention further aims to provide application of the mussel foot protein-imitated modified lignin adhesion enhancing material in the field of biological material adhesion.

The purpose of the invention is realized by the following technical scheme:

a preparation method of a mussel foot protein-imitated modified lignin adhesion enhancing material comprises the following steps:

(1) dissolving lignin in a polar solvent, deoxidizing, heating to 100-150 ℃, adding halogenated alkane and/or halogen acid, carrying out reflux reaction for 8-24 hours, purifying, and drying to obtain catechol lignin;

(2) dissolving catechol lignin, non-enol aldehyde and amino acid salt in an alkaline solution, deoxidizing, heating to 40-80 ℃, reacting for 3-6 hours, adjusting the pH to be about neutral, centrifuging, dialyzing, and drying to obtain the mussel foot protein-like modified lignin adhesion enhancing material.

The second method comprises the following steps:

(1) dissolving lignin, non-enol aldehyde and amino acid salt in an alkaline solution, deoxidizing, heating to 40-80 ℃, reacting for 3-6 hours, adjusting the pH to be about neutral, centrifuging, dialyzing, and drying to obtain amino acid grafted lignin;

(2) dissolving amino acid grafted lignin in a polar solvent, deoxidizing, heating to 100-150 ℃, adding halogenated alkane and/or halogen acid, carrying out reflux reaction for 8-24 hours, purifying, and drying to obtain the mussel foot protein-like modified lignin adhesion enhancing material.

Preferably, the weight ratio of the lignin grafted by the amino acid in the first step (1) of the method and the weight ratio of the lignin grafted by the amino acid in the second step (2) of the method to the halogenated alkane and/or the halogen acid are both 1-8: 6-24; more preferably 1: 1-1: 5; more preferably 3 to 6: 9 to 12.

Preferably, the weight ratio of the lignin in the first step (1) of the method and the weight ratio of the amino acid grafted lignin to the polar solvent in the second step (2) of the method are both 1-10: 5-45; more preferably 3 to 6: 24.

preferably, the lignin in the first and second steps (1) is at least one of Kraft lignin, enzymatic lignin and alkali lignin.

More preferably, the alkali lignin is at least one of wood pulp alkali lignin, bamboo pulp alkali lignin, wheat straw pulp alkali lignin, reed pulp alkali lignin, bagasse pulp alkali lignin, asparagus pulp alkali lignin and cotton pulp alkali lignin.

Different treatment modes are used for treatment in the papermaking and pulping industry, lignin which is a byproduct in the biological fermentation ethanol industry is collectively called industrial lignin, and further the lignin is divided according to different pulping processes, so that different industrial lignin spatial structures, types and contents of active functional groups have great differences. There are three more common types of industrial lignins: firstly, lignosulfonate: the byproduct of the sulfite (acid) pulping process, alkali lignin and Kraft lignin: respectively adopting sulfate method and sulfate method (alkaline method) to prepare a byproduct of pulping process, and organic solvent lignin: extracting lignin from plant by organic reagent such as fatty alcohol and ketone under high temperature and high pressure, and fermenting with cellulose hydrolase and bioethanol to obtain the final product.

Preferably, the polar solvent used in the first step (1) and the second step (2) is at least one of N, N-dimethylformamide, dimethyl sulfoxide and 1, 4-dioxane.

Preferably, the oxygen removing treatment in the first and second steps (1) to (2) is: and repeatedly vacuumizing and filling nitrogen for treatment.

Preferably, in the first step (1) and the second step (2), the halogenated alkane is at least one of iodocyclohexane and bromocyclohexane, and the hydrohalic acid is at least one of hydroiodic acid and hydrobromic acid.

Preferably, the reflux reaction in the first step (1) and the second step (2) is carried out at 120-150 ℃ for 8-12 hours.

Preferably, the purification method in the first method step (1) and the second method step (2) is as follows: washing the reaction product mixed solution by using normal hexane to remove unreacted halogenated alkane, then dropwise adding the reaction solution into a saturated sodium metabisulfite solution to remove halogenated methane and/or halogen acid, separating out a product, filtering, retaining a precipitate and washing.

Preferably, the weight ratio of the catechol lignin in the first step (2) of the method and the lignin to the amino acid salt in the second step (1) of the method is 10: 2-10; more preferably 10: 4 to 8.

Preferably, the non-enol aldehyde in step (2) and step (1) is at least one of formaldehyde, acetaldehyde and glyoxal.

Preferably, the amino acid salt in the first step (2) and the second step (1) is at least one of lysine (Lys), arginine (Arg), histidine (His), and phosphoserine (PSer).

Preferably, the molar ratio of the amino acid salt to the non-enolic aldehyde in process one step (2) and process two step (1) is 1: 0.8-1: 2; more preferably 1: 1-1: 1.5.

preferably, the alkaline solution in the first step (2) and the second step (1) is at least one of a NaOH solution and a KOH solution having a pH of 12 to 13.

Preferably, the catechol lignin in the first step (2) of the method and the lignin and the alkaline solution in the second step (1) of the method are both in a ratio of 1-2 g: 20 mL.

Preferably, the reaction temperature in the first step (2) and the reaction temperature in the second step (1) are both 50-60 ℃ and the reaction time is 4-5 hours.

Preferably, the methods for adjusting the pH to about neutral in the first method step (2) and the second method step (1) are both: adjusting the pH value of the reaction product mixed solution to 7-8 by using concentrated hydrochloric acid and/or concentrated sulfuric acid; the mass concentrations of the concentrated hydrochloric acid and the concentrated sulfuric acid are respectively 37% and 98%.

Preferably, the centrifugation in method one step (2) and method two step (1) is performed by: centrifuging for 10-20 minutes at 8000-10000 rmp.

Preferably, the dialysis treatment time in the first method step (2) and the second method step (1) is 3-7 days, the dialysate is water, and the dialysis is carried out until the conductivity of the dialysate is similar to or consistent with that of deionized water.

The invention provides a mussel foot protein-imitated modified lignin adhesion enhancing material prepared by the method.

Compared with common industrial alkali lignin, the mussel foot protein-like modified lignin adhesion reinforcing material disclosed by the invention enhances the acting force on skin tissues by 2.47-5.31 times, has an excellent adhesion reinforcing effect, and can be used for preparing a reinforcing material of an adhesion material.

The invention provides an application of the mussel foot protein-like modified lignin adhesion enhancing material in the field of biological adhesion, wherein the adhesion enhancing material takes biological tissues as adhesion objects.

The lignin is an aromatic high-molecular polymer with a large number of etherified phenolic hydroxyl functional groups, and has good biocompatibility and oxidation resistance. After the lignin is subjected to demethylation chemical modification, the content of phenolic hydroxyl in the lignin can be obviously improved, and the lignin is etherified with ortho-position and vicinal-position of the phenolic hydroxyl to form a catechol structure. Then a specific amino acid side chain is introduced to the ortho position of the phenolic hydroxyl group, the chemical structure of the mussel foot adhesive protein is simulated in the lignin, and the coulomb force-hydrophobic action mechanism is utilized to realize the adhesion enhancement.

Compared with the prior art, the invention has the following advantages and beneficial effects:

(1) the lignin has good biocompatibility and a large number of phenolic hydroxyl modified sites, the phenolic hydroxyl active sites in molecules are increased to be 150% or more of the original sites after demethylation modification, so that the adhesion of the lignin to biological skin tissues is obviously enhanced, amino acid residues with positive charges are introduced, the chemical structure of mussel foot adhesive protein is simulated, and the adhesion enhancement is realized according to a coulomb force-hydrophobic action mechanism.

(2) The catechol structure prepared by the in-situ demethylation method can be mutually converted with a semiquinone free radical and a quinoid structure, the semiquinone and quinoid structure is favorable for biological tissue adhesion but not favorable for the continuity of the adhesion effect, amino acid residues with sulfydryl are introduced into the catechol structure lignin to prevent the catechol structure from being excessively oxidized into the semiquinone and quinoid structure, the effective action time is prolonged according to the side chain antioxidation action mechanism, and the adhesion enhancement is realized.

(3) Compared with expensive dopamine, lignin, amino acid salt and fatty amine are cheap and easily available raw materials, and the cheap materials can be used for partially replacing the expensive materials through two-step general modification, so that the cost of the adhesion enhancing materials is reduced, and the high-efficiency high-performance high-efficiency high-performance high-efficiency high-performance high-efficiency high-performance high-efficiency high-performance high-efficiency high-performance high-efficiency high-performance high-efficiency high-performance high-efficiency high-performance high.

Drawings

Fig. 1 is a schematic diagram of a hydrocarbon heteronuclear single-quantum two-dimensional nuclear magnetic spectrum, chemical shift statistics and a structure of an alkali lignin raw material and catechol alkali lignin in example 1.

FIG. 2 is a nuclear magnetic hydrogen spectrum of the raw material of alkali lignin, catechol alkali lignin in examples 1 to 4, and the adhesion-enhancing materials of mussel foot protein-modified lignin in comparative examples 3 to 4 in example 1.

FIG. 3 is a Fourier infrared spectrum of the alkali lignin raw material, catechol alkali lignin and the mussel foot protein-modified lignin adhesion-enhancing material of examples 1 to 4 and comparative examples 3 to 4 in example 1.

FIG. 4 is a histogram of the statistical frequency distribution of the acting force of the alkali lignin raw material, catechol alkali lignin and the mussel foot protein-modified lignin adhesion enhancing material in the PBS buffer solution on the pigskin tissue in example 1 and examples 1 to 4.

FIG. 5 is a histogram of the statistical frequency distribution of the acting force of the modified lignin adhesion enhancing material of comparative examples 1-4 on the pigskin tissue in the PBS buffer solution.

In the figure, lysine bionic modification is a sample of example 1, arginine bionic modification is a sample of example 2, cysteine bionic modification is a sample of comparative example 3, a lysine bionic modification method 2 is a sample of example 3, an arginine bionic modification method 2 is a sample of example 4, and a cysteine bionic modification method 2 is a sample of comparative example 4.

Detailed Description

The present invention will be described in further detail with reference to examples and drawings, but the embodiments of the present invention are not limited thereto.

Those who do not specify specific conditions in the examples of the present invention follow conventional conditions or conditions recommended by the manufacturer. The raw materials, reagents and the like which are not indicated for manufacturers are all conventional products which can be obtained by commercial purchase.

Example 1

(1) 3g of alkali lignin is dissolved in 24g N, N-dimethylformamide solution, the reaction device is repeatedly vacuumized and filled with nitrogen for three times, the mixture is heated for 15min at 150 ℃, then 12ml of iodocyclohexane is slowly added, and the reaction is refluxed for 12 hours. And after the reaction liquid is cooled, using n-hexane as a detergent to wash away unreacted iodocyclohexane. And then, dropwise adding the reaction solution into a saturated sodium metabisulfite solution to wash out iodomethane and a polar organic solvent, filtering, retaining precipitate, washing to remove salt, and freeze-drying to obtain the catechol alkali lignin.

(2) 1g of catechol-alkali lignin was dissolved in 20mL of 2.5 wt% NaOH solution, 0.8g of arginine and 0.132g of glyoxal liquid were added, the reaction apparatus was subjected to repeated vacuum-nitrogen charging treatment for three times, and heated at 60 ℃ for 4 hours. Then, the pH of the reaction solution was adjusted to 7.5 by using 37% by mass concentrated hydrochloric acid, and the reaction solution was centrifuged at 10000rmp for 10 minutes, and the supernatant was dialyzed in pure water for 5 days until the conductivity of the dialysate approached that of the pure water. Concentrating, and freeze-drying to obtain the mussel foot protein-like modified lignin adhesion enhancing material.

Figure 1 is an HSQC two-dimensional nuclear magnetic spectrum of the alkali lignin feedstock and catechol alkali lignin of example 1. The alkali lignin raw material is found to contain a large amount of guaiacol structures and ferulic acid structures, and simultaneously has a strong etherified phenolic hydroxyl signal peak, the guaiacol structures and the ferulic acid structures are retained after demethylation modification, and the etherified phenolic hydroxyl signal peak is greatly reduced, so that the catechol structures can be presumed to appear in the ferulic acid and guaiacol structures.

FIG. 2 is a nuclear magnetic hydrogen spectrum of the alkali lignin raw material, catechol alkali lignin and mussel foot protein-modified lignin adhesion-enhancing material of example 1. The alkali lignin raw material has a wide and strong etherified phenolic hydroxyl signal peak at 3.75ppm, almost disappears in catechol alkali lignin, and a phenolic hydroxyl active hydrogen peak signal appears at 7-8 ppm, which shows that the catechol alkali lignin has stronger chemical reaction activity and is successfully modified. After biomimetic modification, a plurality of new signal peaks such as 2.1ppm, 2.5ppm, 2.9ppm and the like appear in the side chain region of lignin and belong to the amine group and the adjacent carbon protons.

FIG. 3 is a Fourier infrared spectrum of the alkali lignin feedstock, catechol alkali lignin, and mussel foot protein-modified lignin adhesion enhancing material of example 1. Absorption peak of phenolic hydroxyl group before and after demethylation modification is 3500cm^-1And 1370cm^-1Stronger absorption occurs, and no obvious change occurs in other places, which shows that only phenolic hydroxyl groups are increased by modification without damaging the benzene ring structure of lignin. 1623cm corresponding to secondary amine after biomimetic modification^-1Shows strong absorption at 1755cm^-1Aldehyde group characteristic absorption appears, which indicates that the bionic modification is successful.

FIG. 4 is a histogram of the statistical frequency distribution of the forces exerted by the alkali lignin feedstock, catechol alkali lignin, and mussel foot protein-modified lignin adhesion enhancing material of example 1 on pigskin tissue in PBS buffer. Preparing a pigskin tissue substrate by using 503 biological glue, testing the acting force of a sample on the pigskin tissue by using an atomic force microscope 2D torque curve test mode in a PBS7.4 buffer solution environment at the temperature of 25 ℃, and selecting effective test results for counting after 150 times of testing. The result shows that the acting force of the alkali lignin raw material on the skin is the minimum, the acting force of the demethylated catechol alkali lignin on the skin is enhanced by 1.78 times, and the adhesion enhancing material of the mussel foot protein-like modified lignin is further enhanced to be 2.68 times of the acting force of the alkali lignin raw material on the skin, which shows that the biological adhesion is obviously enhanced.

FIG. 5 is a histogram of the statistical frequency distribution of the force of comparative example material in PBS buffer on porcine skin tissue.

Example 2

(1) 3g of alkali lignin is dissolved in 24g of N, N-dimethylformamide solution, the reaction device is subjected to repeated vacuumizing-nitrogen filling treatment for three times, air is isolated, the reaction device is heated at 150 ℃ for 15min, then 12mL of iodocyclohexane is slowly added under the stirring condition, and then the reflux reaction is carried out for 12 hours. And after the reaction liquid is cooled, using n-hexane as a detergent to wash away unreacted iodocyclohexane. And then, dropwise adding the reaction solution into a saturated sodium metabisulfite solution to wash out iodomethane and a polar organic solvent, filtering, retaining and washing the precipitate, and then, carrying out freeze drying to obtain the catechol alkali lignin.

(2) 1g of catechol-alkali lignin was dissolved in 20mL of 2.5 wt% NaOH solution, 0.8g of lysine and 0.160g of glyoxal liquid were added, the reaction apparatus was subjected to repeated vacuum-nitrogen filling treatment for three times, and heated at 60 ℃ for 4 hours. Then, the pH of the reaction solution was adjusted to 7.5 with concentrated hydrochloric acid, and the reaction solution was centrifuged at 10000rmp for 10 minutes, and the supernatant was dialyzed in pure water for 5 days until the conductivity of the dialysate approached that of the pure water. Concentrating, and freeze-drying to obtain the mussel foot protein-like modified lignin adhesion enhancing material.

The results of the nmr hydrogen spectroscopy, the fourier spectroscopy, the AFM probe modification preparation method, and the AFM 2D torque curve test mode, which are the same as those in example 1, are shown in fig. 2, fig. 3, and fig. 4, respectively. The acting force of the mussel foot protein-imitated modified lignin adhesion enhancing material on the pigskin tissue is 2.47 times of that of the alkali lignin raw material.

Example 3

(1) 2g of alkali lignin was dissolved in 20mL of 2.5 wt% NaOH solution, 1.6g of lysine and 0.320g of glyoxal liquid were added, the reaction apparatus was subjected to three times of repeated vacuum-nitrogen charging treatment, and heated at 60 ℃ for 4 hours. Then, the pH of the reaction solution was adjusted to 7.5 with 37% by mass of concentrated hydrochloric acid, and the reaction solution was centrifuged at 10000rmp for 10 minutes, and the supernatant was dialyzed in pure water for 5 days until the conductivity of the dialysate approached that of pure water. And concentrating, and freeze-drying to obtain the lysine grafted lignin.

(2) Dissolving 2g of lysine grafted lignin in 12g of N, N-dimethylformamide solution, repeatedly vacuumizing and filling nitrogen for three times in a reaction device, isolating air, heating at 150 ℃ for 15min, then slowly adding 8mL of iodocyclohexane under stirring, and then refluxing for reaction for 12 hours. And after the reaction liquid is cooled, using n-hexane as a detergent to wash away unreacted iodocyclohexane. And then, dropwise adding the reaction solution into a saturated sodium metabisulfite solution to wash out iodomethane and a polar organic solvent, filtering, retaining and washing the precipitate, and then carrying out freeze drying to obtain the mussel foot protein modified lignin adhesion enhancing material.

The results of the nmr hydrogen spectroscopy, the fourier spectroscopy, the AFM probe modification preparation method, and the AFM 2D torque curve test mode, which are the same as those in example 1, are shown in fig. 2, fig. 3, and fig. 4, respectively. The acting force of the mussel foot protein-imitated modified lignin adhesion enhancing material on the pigskin tissue is 5.31 times of that of the alkali lignin raw material.

Example 4

(3) Dissolving 2g of alkali lignin in 20mL of 2.5 wt% NaOH solution, adding 1.6g of arginine and 0.264g of glyoxal liquid, carrying out three times of repeated vacuum-nitrogen filling treatment on a reaction device, and heating for 4 hours at 60 ℃. Then, the pH of the reaction solution was adjusted to 7.5 with concentrated hydrochloric acid, and the reaction solution was centrifuged at 10000rmp for 10 minutes, and the supernatant was dialyzed in pure water for 5 days until the conductivity of the dialysate approached that of the pure water. Concentrating, and freeze drying to obtain arginine grafted lignin

(4) Dissolving 2g of arginine grafted lignin in 12g of N, N-dimethylformamide solution, repeatedly vacuumizing and filling nitrogen in a reaction device for three times, isolating air, heating at 150 ℃ for 15min, then slowly adding 8mL of iodocyclohexane under stirring, and then carrying out reflux reaction for 12 hours. And after the reaction liquid is cooled, using n-hexane as a detergent to wash away unreacted iodocyclohexane. And then, dropwise adding the reaction solution into a saturated sodium metabisulfite solution to wash out iodomethane and a polar organic solvent, filtering, retaining and washing the precipitate, and then carrying out freeze drying to obtain the mussel foot protein modified lignin adhesion enhancing material.

The results of the nmr hydrogen spectroscopy, the fourier spectroscopy, the AFM probe modification preparation method, and the AFM 2D torque curve test mode, which are the same as those in example 1, are shown in fig. 2, fig. 3, and fig. 4, respectively. The acting force of the mussel foot protein-imitated modified lignin adhesion enhancing material on the pigskin tissue is 3.14 times of that of the alkali lignin raw material.

Comparative example 1

(1) 3g of alkali lignin was dissolved in 24g of N, N-dimethylformamide solution, the reaction apparatus was heated at 150 ℃ for 15min without air isolation, and then 12mL of iodocyclohexane was slowly added under stirring, followed by reflux reaction for 12 hours. And after the reaction liquid is cooled, using n-hexane as a detergent to wash away unreacted iodocyclohexane. And then, dropwise adding the reaction solution into a saturated sodium metabisulfite solution to wash out iodomethane and a polar organic solvent, filtering, retaining and washing the precipitate, and then, carrying out freeze drying to obtain the catechol alkali lignin.

(2) 1g of catechol-alkali lignin was dissolved in 20mL of a 2.5 wt% NaOH solution, 0.160g of glyoxal liquid was added, the reaction apparatus was deoxygenated, and the mixture was heated at 60 ℃ for 4 hours. Then, the pH of the reaction solution was adjusted to 7.5 with concentrated hydrochloric acid, and the reaction solution was centrifuged at 10000rmp for 10 minutes, and the supernatant was dialyzed in pure water for 5 days until the conductivity of the dialysate approached that of the pure water. Concentrating, and freeze-drying to obtain the mussel foot protein-like modified lignin adhesion enhancing material.

The 2D moment curve test mode of the atomic force microscope, which is the same as that of the example 1, is adopted, and the result shows that oxygen in the air reacts with catechol alkali lignin at high temperature to form quinoid lignin due to the fact that no nitrogen filling reaction step is carried out, and positive charge groups or antioxidant groups of amino acids are not introduced, so that the adhesion enhancement effect is not obvious, the effective test times are fewer, and only 1.65 times of that of alkali lignin raw materials are used.

Comparative example 2

(2) 1g of catechol-hydrolyzed lignin was dissolved in 20mL of a 2.5 wt% NaOH solution, 0.8g of ethylenediamine and 0.160g of glyoxal liquid were added, the reaction apparatus was subjected to repeated vacuum-nitrogen filling treatment for three times, and heated at 60 ℃ for 4 hours. The reaction solution was then adjusted to pH 7.5 with concentrated hydrochloric acid and dialyzed in pure water for 5 days until the conductivity of the dialysate approached that of pure water. And concentrating, and freeze-drying to obtain the demethylation-amination modified lignin adhesion reinforcing material.

The 2D moment curve test mode of the atomic force microscope, which is the same as that of the example 1, is adopted, and the result shows that the intramolecular and/or intermolecular crosslinking of lignin during the Mannich reaction is caused due to the same activity of two primary amine groups in the ethylenediamine molecule, so that the molecular weight is increased, the solubility is weakened, the probe modification is not facilitated, in addition, the primary amine groups are less, the flexibility of catechol benzene rings is poor, the adhesion effect is weaker than that of the modification by using amino acid with a single reaction active site, and only 1.29 times of that of the alkali lignin raw material is obtained.

Comparative example 3

(1) 3g of alkali lignin is dissolved in 24g of N, N-dimethylformamide solution, the reaction device is subjected to repeated vacuumizing-nitrogen filling treatment for three times, air is isolated, the reaction device is heated at 150 ℃ for 15min, then 12mL of iodocyclohexane is slowly added under the stirring condition, and then the reflux reaction is carried out for 12 hours. And after the reaction liquid is cooled, using n-hexane as a detergent to wash away unreacted iodocyclohexane. And then, dropwise adding the reaction solution into a saturated sodium metabisulfite solution to wash out iodomethane and a polar organic solvent, filtering, retaining and washing the precipitate, and then carrying out freeze drying to obtain the catechol hydrolyzed lignin.

(2) 1g of catechol-hydrolyzed lignin was dissolved in 20mL of 2.5 wt% NaOH solution, 0.8g of cysteine and 0.160g of glyoxal liquid were added, the reaction apparatus was subjected to repeated vacuum-nitrogen filling treatment for three times, and heated at 60 ℃ for 4 hours. Then, the pH of the reaction solution was adjusted to 7.5 with concentrated hydrochloric acid, and the reaction solution was centrifuged at 10000rmp for 10 minutes, and the supernatant was dialyzed in pure water for 5 days until the conductivity of the dialysate approached that of the pure water. Concentrating, and freeze-drying to obtain the mussel foot protein-like modified lignin adhesion enhancing material.

The results of the nmr hydrogen spectroscopy, the fourier spectroscopy, and the afm 2D torque curve test mode, which are the same as those of example 1, are shown in fig. 2, fig. 3, and fig. 5, respectively. The acting force of the mussel foot protein-imitated modified lignin adhesion enhancing material on the pigskin tissue is only 1.29 times of that of the alkali lignin raw material.

Comparative example 4

(1) 2g of alkali lignin was dissolved in 20mL of 2.5 wt% NaOH solution, 1.6g of cysteine and 0.320g of glyoxal liquid were added, the reaction apparatus was subjected to three times of repeated vacuum-nitrogen charging treatment, and heated at 60 ℃ for 4 hours. Then, the pH of the reaction solution was adjusted to 7.5 with concentrated hydrochloric acid, and the reaction solution was centrifuged at 10000rmp for 10 minutes, and the supernatant was dialyzed in pure water for 5 days until the conductivity of the dialysate approached that of the pure water. And concentrating, and freeze-drying to obtain the cysteine grafted lignin.

(2) Dissolving 2g of cysteine grafted lignin in 12g of N, N-dimethylformamide solution, repeatedly vacuumizing and filling nitrogen for three times in a reaction device, isolating air, heating at 150 ℃ for 15min, then slowly adding 8mL of iodocyclohexane under stirring, and then carrying out reflux reaction for 12 hours. And after the reaction liquid is cooled, using n-hexane as a detergent to wash away unreacted iodocyclohexane. And then, dropwise adding the reaction solution into a saturated sodium metabisulfite solution to wash out iodomethane and a polar organic solvent, filtering, retaining and washing the precipitate, and then carrying out freeze drying to obtain the mussel foot protein modified lignin adhesion enhancing material.

The above embodiments are preferred embodiments of the present invention, but the present invention is not limited to the above embodiments, and any other changes, modifications, substitutions, combinations, and simplifications which do not depart from the spirit and principle of the present invention should be construed as equivalents thereof, and all such changes, modifications, substitutions, combinations, and simplifications are intended to be included in the scope of the present invention.

Claims

1. A preparation method of a mussel foot protein-imitated modified lignin adhesion enhancing material is characterized in that,

the first method comprises the following steps:

(2) dissolving catechol lignin, non-enol aldehyde and amino acid salt in an alkaline solution, deoxidizing, heating to 40-80 ℃, reacting for 3-6 hours, adjusting the pH to be about neutral, centrifuging, dialyzing, and drying to obtain the mussel foot protein-like modified lignin adhesion reinforcing material;

the second method comprises the following steps:

2. The method for preparing the mussel foot protein-modified lignin adhesion-enhancing material according to claim 1, wherein the weight ratio of the catechol lignin in the first step (2) and the weight ratio of the lignin to the amino acid salt in the second step (1) are 10: 2-10;

the molar ratio of the amino acid salt to the non-enol aldehyde in the first step (2) and the second step (1) of the method is 1: 0.8-1: 2;

in the first step (2) and the second step (1), the non-enol aldehyde is at least one of formaldehyde, acetaldehyde and glyoxal;

in the first step (2) and the second step (1), the amino acid salt is at least one of lysine, arginine, histidine and phosphoserine.

3. The method for preparing the mussel foot protein-modified lignin adhesion-enhancing material according to claim 2, wherein the weight ratio of the catechol lignin in the first step (2) and the weight ratio of the lignin to the amino acid salt in the second step (1) are 10: 4-8;

the molar ratio of the amino acid salt to the non-enol aldehyde in the first step (2) and the second step (1) of the method is 1: 1-1: 1.5.

4. the method for preparing the mussel foot protein-like modified lignin adhesion-enhancing material according to claim 1, wherein the weight ratio of the lignin in the first step (1) and the amino acid-grafted lignin in the second step (2) to the halogenated alkane and/or halogen acid is 1-8: 6-24;

in the first step (1) and the second step (2), the halogenated alkane is at least one of iodocyclohexane and bromocyclohexane, and the hydrohalic acid is at least one of hydroiodic acid and hydrobromic acid.

5. The method for preparing the mussel foot protein-like modified lignin adhesion-enhancing material according to claim 1, wherein the weight ratio of the lignin in the first step (1) and the amino acid-grafted lignin in the second step (2) to the polar solvent is 1-10: 5-45;

in the first and second steps (1), the lignin is at least one of Kraft lignin, enzymatic lignin and alkali lignin.

6. The method for preparing the mussel foot protein-like modified lignin adhesion enhancing material according to claim 1, wherein the reflux reaction in the first step (1) and the second step (2) is carried out at 120-150 ℃ for 8-12 hours;

the reaction temperature in the first step (2) and the reaction temperature in the second step (1) are both 50-60 ℃ and the reaction time is 4-5 hours.

7. The method for preparing the mussel foot protein-modified lignin adhesion-enhancing material according to claim 1, wherein in the first step (2) and the second step (1), the alkaline solution is at least one of a NaOH solution and a KOH solution with pH of 12-13;

the catechol lignin in the first step (2) of the method and the lignin and the alkaline solution in the second step (1) of the method are both in a proportion of 1-2 g: 20 mL;

in the first step (1) and the second step (2), the polar solvent is at least one of N, N-dimethylformamide, dimethyl sulfoxide and 1, 4-dioxane.

8. The method for preparing the mussel foot protein-like modified lignin adhesion-enhancing material according to claim 1, wherein the oxygen-removing treatment in the first and second steps (1) - (2) is: repeatedly vacuumizing and filling nitrogen for treatment;

the methods for adjusting the pH to about neutral in the first method step (2) and the second method step (1) are both as follows: adjusting the pH value of the reaction product mixed solution to 7-8 by using concentrated hydrochloric acid and/or concentrated sulfuric acid; the mass concentrations of the concentrated hydrochloric acid and the concentrated sulfuric acid are respectively 37% and 98%;

the centrifugation method in the first method step (2) and the second method step (1) is as follows: centrifuging for 10-20 minutes at 8000-10000 rmp;

the dialysis treatment time in the first method step (2) and the second method step (1) is 3-7 days, and the dialysate is water.

9. A mussel foot protein-like modified lignin adhesion enhancing material prepared by the method of any one of claims 1 to 8.

10. The use of the mussel foot protein-modified lignin adhesion-enhancing material of claim 9 in the field of bioadhesive.