CN113717966B - Preparation method and application of hydrogel/metal organic framework composite carrier - Google Patents

Abstract

The invention relates to an enzyme immobilization method, in particular to a preparation method and application of a hydrogel/metal organic framework composite carrier. The composite carrier is prepared by taking hydrogel as an enzyme immobilized substrate material, carrying out surface modification treatment on the hydrogel by using dopamine, and then growing a metal organic framework layer on the surface of the dopamine in situ. The existence of the metal organic framework layer can effectively protect the catalytic activity and stability of the immobilized enzyme, and the hydrogel can provide a reaction microenvironment with good biocompatibility so as to maintain the spatial conformation of the enzyme and reduce the loss of the enzyme activity in the immobilization process. The hydrogel/metal organic framework composite carrier prepared by the invention has the advantages of high enzyme loading efficiency, good enzyme stability, simple operation, mild condition, easy realization and the like.

Description

Preparation method and application of hydrogel/metal organic framework composite carrier

Technical Field

The invention relates to an enzyme immobilization method, in particular to a preparation method and application of a hydrogel/metal organic framework composite carrier.

Background

The multienzyme cascade is a major class of chemical transformations in living cells that mediate signal transduction and metabolic pathways; unlike stepwise synthesis, efficient transport of intermediates between active sites allows cascade reactions to be completed with unparalleled efficiency, while eliminating cumbersome intermediate isolation and purification procedures. Because of its catalytic advantages, people are devoted to constructing an artificial multi-enzyme cascade system by using different materials such as mesoporous silica, organic polymer, hydrogel and DNA as enzyme carriers. Among them, hydrogels are a favored enzyme immobilization carrier. This is because the hydrogel has a biocompatible microenvironment and a macroporous structure similar to those of cells, and can enable the immobilized enzyme to maintain the original natural conformation, thereby representing higher catalytic activity. However, the poor mechanical strength of hydrogels has prevented its practical use as an enzyme immobilization carrier. In recent years, the preparation of hydrogel hybrids using inorganic materials is becoming a new method for improving the mechanical strength of hydrogels. However, it remains a great challenge to maintain the original macroporous structure and aqueous microenvironment of the hydrogel in the inorganic hybrid.

The metal organic framework is a novel enzyme immobilization carrier material developed in recent years. Compared with the traditional enzyme immobilization such as silicon dioxide, the metal organic framework has the unique advantages of large surface area, controllable surface chemistry, high thermal stability and chemical stability and the like. However, during enzyme immobilization, the metal-organic frameworks often interact with enzymes in some specific or non-specific ways, thereby limiting the spatial conformational changes of the enzyme. While this restriction condition is advantageous for improving the stability of the enzyme, it can negatively affect the catalytic activity of the enzyme. Therefore, researchers at home and abroad propose to overcome the defect of small pore volume of the metal-organic framework by preparing a hollow or layered porous structure. Although these studies have achieved interesting results, the conformational independence of enzymes is still extremely limited and the enzymes inevitably aggregate in limited space, affecting the spatial conformation of the enzyme.

Disclosure of Invention

Aiming at the defects of the existing enzyme immobilization carrier, the invention provides a preparation method of a hydrogel/metal organic framework composite carrier, and the composite carrier prepared by the method has the characteristic of protecting the spatial conformation of the enzyme, and can effectively enhance the catalytic activity and stability of the enzyme.

In order to achieve the above purpose, the present invention adopts the following technical scheme.

The preparation method of the hydrogel/metal organic framework composite carrier uses hydrogel as an immobilized substrate material of enzyme, and after the surface modification of polydopamine, the metal organic framework structure grows on the surface of the dopamine in situ, and the preparation method comprises the following specific steps:

1) Dissolving enzyme in a pregelatinized solution to prepare an enzyme/pregelatinized solution, and utilizing a microfluidic technology to promote gelation of the enzyme/pregelatinized solution so as to prepare an enzyme immobilized hydrogel material;

2) Placing the hydrogel material prepared in the step 1) into 1.5 mg/mL-2 mg/mL of dopamine solution according to the volume ratio of material/dopamine solution=1/10, stirring for 1h, and washing to obtain the surface modified enzyme immobilized hydrogel modified material;

3) Mixing and stirring the modified material prepared in the step 2) and 125mM zinc nitrate solution with the volume ratio of 1/10 for 3 hours, and then adding 2-methylimidazole solution with the same volume concentration as the metal salt solution of 500mM, and continuously stirring for 7 hours to obtain the composite material. The composite material is the hydrogel/metal organic framework composite carrier.

Preferably, the enzyme solutions are glucose oxidase (GOx) and horseradish peroxidase (HRP).

Preferably, the pregelatinized agent comprises acrylamide, N-methylenebisacrylamide, and 2-hydroxy-4- (2-hydroxyethoxy) -2-methylpropionyl ketone.

Preferably, the mass ratio of the acrylamide to the N, N-methylene bisacrylamide to the 2-hydroxy-4- (2-hydroxyethoxy) -2-methyl propiophenone is 15:1:1.

preferably, the molar ratio of the metal salt to the ligand is 1:4.

The invention also provides the hydrogel/metal organic framework composite material of the immobilized enzyme prepared by the method.

The invention also comprises application of the hydrogel/metal organic framework composite material for immobilizing the enzyme in the field of enzyme immobilization.

The invention has the beneficial effects that:

the preparation method of the composite carrier is simple, has mild condition requirements and is easy to realize. The hydrogel/metal organic framework composite material is prepared, and the hydrogel can protect the space conformation of the immobilized enzyme; the metal organic framework layer can improve the mechanical strength of the hydrogel, and can effectively retain the micro water environment of enzyme immobilization, thereby improving the catalytic activity and stability of the immobilized enzyme.

Drawings

FIG. 1 is a scanning electron microscope image of the hydrogel (pAAm), dopamine-modified hydrogel (pAAm@PDA), hydrogel/metal-organic framework composite (pAAm@ZIF-8) of example 1 of the present invention.

FIG. 2 shows the free GOx/HRP, GOx/HRP@pAAm,

GOx/HRP@pAAm@PDA, GOx/HRP@pAAm@ZIF-8.

FIG. 3 shows the free GOx/HRP, GOx/HRP@pAAm,

GOx/HRP@pAAm@PDA, GOx/HRP@pAAm@ZIF-8.

FIG. 4 shows the free GOx/HRP, GOx/HRP@pAAm,

GOx/HRP@pAAm@PDA, GOx/HRP@pAAm@ZIF-8 cycle stability comparison.

Detailed Description

In order that the above-recited objects, features and advantages of the present invention will be more clearly understood, a more particular description of the invention will be rendered by reference to the appended drawings and appended detailed description. In the following description, numerous specific details are set forth in order to provide a thorough understanding of the present invention, however, the present invention may be practiced in other ways than those described herein, and therefore the present invention is not limited to the specific embodiments disclosed below.

In the following examples, glucose oxidase was labeled GOx, horseradish peroxidase was labeled HRP, acrylamide was labeled AAm, N, N-methylenebisacrylamide was labeled BIS, 2-hydroxy-4- (2-hydroxyethoxy) -2-methylpropionacetone was labeled PI, hydrogels immobilized glucose oxidase and horseradish peroxidase were labeled GOx/HRP@pAAm, GOx/HRP@pAAm after dopamine surface modification was labeled GOx/HRP@pAAm@PDA, and hydrogel/metal-organic framework composites immobilized glucose oxidase and horseradish peroxidase were labeled GOx/HRP@pAAm@ZIF-8.

Example 1

The hydrogel/metal organic framework composite (GOx/HRP@pAAm@ZIF-8) of immobilized glucose oxidase and horseradish peroxidase was prepared as follows:

(1) Weighing 3mg/mL GOx and 5mg/mL HRP, AAm (15% wt), BIS (1% wt), and PI (1% wt) to prepare 1mL enzyme/pregel mixed solution;

(2) Curing the enzyme/pregelatinized solution by utilizing an ultraviolet polymerization technology to prepare GOx/HRP@pAAm;

(3) 200. Mu.L of GOx/HRP@pAAm was immersed in 2mL of Tris-HCl buffer (10 mM, pH=8.5), and 4mg of dopamine was added for hydrogel surface modification; after reacting for 1h under mild stirring, obtaining GOx/HRP@pAAm@PDA by centrifugal collection, and washing 3 times by using ultrapure water;

(4) Placing the obtained washed GOx/HRP@pAAm@PDA into 2ml 125mM zinc nitrate aqueous solution for incubation for 3 hours at normal temperature; after centrifugal washing, 2mL of 500mM 2-methylimidazole aqueous solution was added for further reaction for 7 hours, and finally washed with ultrapure water to obtain GOx/HRP@pAAm@ZIF-8.

Example 2

And (3) combining with a 2,2' -biazal-bis-3-ethylbenzothiazoline-6-sulfonic Acid (ABTS) oxidation experiment, recording the absorbance corresponding to the maximum absorption peak by using an ultraviolet spectrophotometer to detect the catalytic activity of GOx/HRP@pAAm@ZIF-8. The specific method comprises the following steps:

(1) Phosphate (PBS) with ph=7.4 was used as buffer solution for a total volume of 300 μl, a reaction temperature of 37 ℃ and a reaction time of 30min;

(2) Under the reaction conditions of the step (1), using 4 centrifuge tubes with the concentration of 0.5mL and the number of a, b, c, d;

(3) The preparation method of the solution in the centrifuge tube a comprises the following steps: 10. Mu.L of ABTS (35 mM), 10. Mu.L of glucose (100 mM) and 2. Mu.L of GOx/HRP mix in 278. Mu.L of PBS buffer at pH=7.4;

(4) The preparation method of the solution in the centrifuge tube b comprises the following steps: mu.L of ABTS (35 mM), 10. Mu.L of glucose (100 mM) and 2. Mu.L of GOx/HRP@pAAm were taken in 278. Mu.L of PBS buffer at pH=7.4;

(5) The preparation method of the solution in the centrifuge tube b comprises the following steps: mu.L of ABTS (35 mM), 10. Mu.L of glucose (100 mM) and 2. Mu.L of GOx/HRP@pAAm@PDA were taken in 278. Mu.L of PBS buffer at pH=7.4;

(6) The preparation method of the solution in the centrifuge tube b comprises the following steps: mu.L of ABTS (35 mM), 10. Mu.L of glucose (100 mM) and 2. Mu.L of GOx/HRP@pAAm@ZIF-8 were taken in 278. Mu.L of PBS buffer at pH=7.4;

(7) After the 4-branch separation tube was placed at a reaction temperature of 37℃for 30 minutes, their maximum absorbance at 405nm was measured by an ultraviolet spectrophotometer, respectively.

As shown in FIG. 3, the catalytic activities of GOx/HRP@pAAm, GOx/HRP@pAAm@PDA and GOx/HRP@pAAm@ZIF-8 systems are close, and the measured catalytic activity is higher than that of a GOx/HRP mixed system, so that the cascade catalytic activity of GOx/HRP is greatly enhanced by taking the hydrogel as a carrier, and the cascade reaction activity of the immobilized GOx/HRP is not influenced by the ZIF-8.

Example 3

Comparison of the recycling stability of the free GOx/HRP, GOx/HRP@pAAm, GOx/HRP@pAAm@PDA, GOx/HRP@pAAm@ZIF-8 systems followed by recording the absorbance corresponding to the maximum absorbance peak using an ultraviolet spectrophotometer. The specific method comprises the following steps:

(1) Phosphate (PBS) with ph=7.4 was used as buffer solution for a total volume of 300 μl, a reaction temperature of 37 ℃ and a reaction time of 30min;

(2) Using 4-branch 0.5mL centrifuge tubes, 2. Mu.L GOx/HRP, 2. Mu.L GOx/HRP@pAAm, 2. Mu.L GOx/HRP@pAAm@PDA, 2. Mu.L GOx/HRP@pAAm@ZIF-8 were added to each of the 4-branch centrifuge tubes;

(3) After adding 10. Mu.L of ABTS (35 mM) and 10. Mu.L of glucose (100 mM) to each test tube for reaction, the maximum absorption peak at 405nm was recorded by an ultraviolet spectrophotometer;

(4) During repeated use of the immobilized GOx/HRP assay, samples were collected, washed 3 times with PBS (10 mM, pH 7.4) to remove residual substrate for the next reaction cycle.

As shown in FIG. 4, after the reaction cycle is performed for 6 times, only the GOx/HRP@pAAm@ZIF-8 system still has more than 90% of the initial enzyme cascade reaction activity, which proves that pAAm@ZIF-8 serving as a carrier material can maintain the stability of efficient catalysis of the enzyme to a great extent.

In summary, the invention provides a new preparation method of the composite carrier, which prepares the hybrid pAAm@ZIF-8 material for co-immobilization of GOx and HRP by utilizing the protection effect of hydrogel on enzyme space conformation and the enhancement of MOFs layer on composite material stability. In the preparation process, the conditions are mild, and the space conformation of the immobilized enzyme is not changed, so that the enzyme still maintains high-efficiency catalytic activity and stability.

The above description is only of the preferred embodiments of the present invention and is not intended to limit the present invention, but various modifications and variations can be made to the present invention by those skilled in the art. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims (4)

1. The preparation method of the hydrogel/metal organic framework composite carrier is characterized by using a hydrogel material as an immobilized substrate of enzyme, and growing a metal organic framework layer structure on the surface of the modified hydrogel through polydopamine surface modification, wherein the preparation method comprises the following specific steps of:

1) Dissolving enzyme in a pregelatinized solution to prepare an enzyme/pregelatinized solution, and utilizing a microfluidic technology to promote gelation of the enzyme/pregelatinized solution so as to prepare an enzyme immobilized hydrogel material;

2) Placing the hydrogel material prepared in the step 1) into a dopamine solution, stirring for 1h, and washing to obtain an enzyme immobilized hydrogel modified material subjected to surface modification treatment;

3) Placing the modified material prepared in the step 2) into zinc nitrate solution, stirring for 3 hours, adding 2-methylimidazole solution, and continuously stirring for 7 hours to obtain a composite material;

the pregel comprises acrylamide, N-methylene bisacrylamide and 2-hydroxy-4- (2-hydroxyethoxy) -2-methylpropionne; the mass ratio of the acrylamide to the N, N-methylene bisacrylamide to the 2-hydroxy-4- (2-hydroxyethoxy) -2-methyl propiophenone is 15:1:1, a step of; the molar ratio of the zinc nitrate to the 2-methylimidazole is 1:4.

2. The method for preparing a composite carrier according to claim 1, wherein the enzyme comprises glucose oxidase and horseradish peroxidase.

3. A hydrogel/metal organic framework composite of immobilized enzymes, prepared according to the method of any one of claims 1 or 2.

4. Use of the enzyme immobilized hydrogel/metal organic framework composite material according to claim 3 in the field of enzyme immobilization.

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