CN116510696A - Hydrogel for adsorbing hemoglobin and preparation method thereof - Google Patents

Abstract

The invention discloses a hydrogel for adsorbing hemoglobin and a preparation method thereof, belonging to the technical field of medicine. The invention combines carbon nitride powder, chitosan and carrageenan, and forms a hydrogel capable of efficiently adsorbing free hemoglobin after cross-linking. Hydrogel, thus effectively avoiding the problems that carbon nitride powder is easy to leak into the blood, easy to aggregate and difficult to recover when the carbon nitride powder is used alone in the extracorporeal circulation filter device, and greatly improves the adsorption effect of free hemoglobin in the blood. The hydrogel for adsorbing hemoglobin of the invention can realize high-efficiency adsorption of free hemoglobin, has good blood compatibility and biological safety, and has clinical application potential.

Description

A kind of hydrogel adsorbing hemoglobin and preparation method thereof

technical field

The invention relates to the technical field of medicine, in particular to a hydrogel for absorbing hemoglobin and a preparation method thereof.

Background technique

Vascular bypass surgery is one of the ideal clinical treatment methods for cardiovascular diseases. However, the mechanical rupture of red blood cells in the extracorporeal circulation of heart surgery will inevitably lead to free hemoglobin (Hb). Most of them are excreted through the kidneys. When the threshold is exceeded, it can cause acute renal injury and cause certain toxicity to the kidneys. Several interventions are clinically available to treat elevated Hb levels in intraoperative patients, including drug therapy and adjuvant therapy, which aim to reduce the patient's Hb levels and prevent disease development. However, many such treatments are unsatisfactory, especially for old and weak patients. Due to the decline or insufficiency of the body's metabolic function, the side effects of the drugs accumulate in the body, causing adverse reactions and increasing the pain of the patients. In addition, there are obvious deficiencies in adjuvant therapy, for example, long-term oxygen inhalation is also interfered by other factors, which also brings economic burden to patients. Therefore, the use of adsorbents to adsorb hemoglobin in the blood circulation process as a therapeutic method has great prospects.

Graphite carbon nitride (gC ₃ N ₄ ) has excellent electronic structure, high specific surface area, large pore volume and chemical inertness. At the level of sample pretreatment, it has high performance in the removal of metal ions and the adsorption of aromatic compounds. In terms of the enrichment of biological samples, after research, graphite-type carbon nitride materials can separate and purify hemoglobin under certain circumstances, and hemoglobin and graphite-type carbon nitride materials mainly interact through hydrogen bond forces and hydrophobic forces. However, the micro/nano structure and morphology of carbon nitride, as an adsorbent during blood circulation, the biosafety of gC ₃ N ₄ is a problem to be solved, when powdered gC ₃ N ₄ is applied to blood circulation, It is easy to aggregate, difficult to recover, and inevitably leaks into the blood, which affects its clinical use. Chitosan (CS) is a natural polymer material with good biocompatibility. Chitosan has hydrophobic binding properties with hemoglobin. However, the main problems of CS adsorbents for hemoglobin removal are their low adsorption capacity and poor mechanical strength, which limit their applications. Carrageenan (k-Car) is a natural linear water-soluble sulfate polysaccharide, which can also form gel beads with chitosan to enhance the stability and elasticity of the gel. Because k-Car has a certain adsorption capacity, the electrostatic attraction between k-Car and hemoglobin is weak, and the adsorption capacity is still very limited. Therefore, the present invention provides a hydrogel adsorbing hemoglobin and a preparation method thereof.

Contents of the invention

The invention provides a hydrogel for adsorbing hemoglobin and a preparation method thereof, which effectively solves the problem that carbon nitride powder is easily leaked into blood, easily aggregated, and difficult to recycle when carbon nitride powder is used alone in an extracorporeal circulation filter device; chitosan and carrageenan For the technical problem of weak hemoglobin adsorption ability, a hydrogel with strong adsorption ability for free hemoglobin in blood, convenient recovery and good biological safety was constructed.

The present invention provides a kind of preparation method of the hydrogel that adsorbs hemoglobin, it is characterized in that, comprises the following steps:

S1, dissolving chitosan in an acetic acid solution to form a chitosan solution, adding calcium chloride to the chitosan solution, and mixing to obtain a mixed solution of calcium chloride and chitosan;

Ultrasonic dispersion of carbon nitride powder in distilled water to obtain a carbon nitride solution, adding carrageenan to the carbon nitride solution, and mixing to obtain a carrageenan carbon nitride mixture;

S2, at room temperature, add the carrageenan carbon nitride mixture of S1 dropwise to the mixed solution of calcium chloride and chitosan to form gel beads, cross-link, and wash to obtain a wet-like hydrogel;

S3, freeze-drying the wet hydrogel described in S2 to obtain a hydrogel that absorbs hemoglobin.

Preferably, in S1, the mass percentage of acetic acid in the acetic acid solution is 2%.

Preferably, in S1, in the mixed solution of calcium chloride and chitosan, the concentration of calcium chloride is 0.1 mol/L, and the concentration of chitosan is 10 mg/mL.

Preferably, in S1, in the mixture of carrageenan and carbon nitride, the mass percentage of carbon nitride is 0.2%-0.4%.

Preferably, in S1, the mass concentration of carrageenan in the carrageenan carbon nitride mixture is 20 mg/mL.

Preferably, in S2, the amount ratio of the carrageenan carbon nitride mixture to the mixed solution of calcium chloride and chitosan is 1:2.

Preferably, in S2, the crosslinking time is 20-30 minutes.

Preferably, in S3, the freeze-drying procedure is: the freeze-drying procedure is: put the wet sample hydrogel of S2 in a centrifuge tube, freeze at -20°C for 2-6 hours, and use the frozen centrifuge tube mouth Wrap in parafilm, tie the mouth with the parafilm, and dry in a freeze dryer for 6-8 hours.

The present invention also provides a hydrogel for absorbing hemoglobin prepared by the above preparation method.

Compared with prior art, the beneficial effect of the present invention is:

The invention provides a hydrogel for adsorbing hemoglobin and a preparation method thereof. In the invention, carbon nitride powder, chitosan and carrageenan are compounded to form a hydrogel capable of efficiently adsorbing free hemoglobin after cross-linking, thereby effectively It avoids the leakage of carbon nitride powder in the blood, is easy to gather, and is difficult to recover, and greatly improves the adsorption effect of free hemoglobin in the blood. The hydrogel adsorbing hemoglobin prepared in Example 2 of the present invention has an adsorption capacity of up to 178.82 mg/g for hemoglobin in 120 minutes; the activated partial thromboplastin of the hydrogel adsorbing hemoglobin prepared in Example 1 and Example 2 Time and plasma thrombin time have no significant difference with Control group and comparative example 1 (chitosan/carrageenan hydrogel); The hydrogel prepared by embodiment 1, embodiment 2 and comparative example 1 is added the red blood cell of equal amount respectively In the suspension, the hemolysis rate of Example 1 was only 1.721%, and the hemolysis rate of the three hydrogels did not exceed 5%. In summary, the hydrogel for adsorbing hemoglobin of the present invention can achieve efficient adsorption of free hemoglobin, and has good blood compatibility and biological safety, and has clinical application potential.

Description of drawings

Fig. 1 is the scanning electron micrograph of the hydrogel of adsorbed hemoglobin of the present invention; Wherein, A figure is comparative example 1 chitosan/carrageenan hydrogel (CS/K-car); B figure is the adsorbed hemoglobin prepared by embodiment 1 Hydrogel (CS/K-car/C ₃ N ₄ -0.2%); Figure C is the hydrogel (CS/K-car/C ₃ N ₄ -0.4%) prepared in Example 2 for adsorbing hemoglobin; Figure D is a macroscopic view of the hydrogel that absorbs hemoglobin in Example 2; Figure E is a diagram of the diameter and size of the hydrogel of Comparative Example 1, Example 1 and Example 2;

Figure 2 shows the comparison example 1 (CS/K-car), Example 1 (CS/K-car/C ₃ N ₄ -0.2%) and Example 2 (CS/K-car/C ₃ N ₄ - 0.4%) of the adsorption efficiency comparison chart of the hydrogel that adsorbs hemoglobin;

Figure 3 shows the Control group of the present invention, Comparative Example 1 (CS/K-car), Example 1 (CS/K-car/C ₃ N ₄ -0.2%) and Example 2 (CS/K-car/C ₃ N ₄ -0.4%) hydrogel activated partial thromboplastin time comparison chart;

Figure 4 shows the Control group of the present invention, Comparative Example 1 (CS/K-car), Example 1 (CS/K-car/C ₃ N ₄ -0.2%) and Example 2 (CS/K-car/C ₃ N ₄ -0.4%) of the plasma thrombin time comparison chart of the hydrogel;

Figure 5 shows the positive control group (+, sterile distilled water), negative control group (-, physiological saline) of the present invention, Comparative Example 1 (CS/K-car), Example 1 (CS/K-car/C ₃ N ₄ -0.2%) and the hydrogel of Example 2 (CS/K-car/C ₃ N ₄ -0.4%) are placed in the same amount of red blood cell suspension and the comparison chart of the hemolysis rate.

Detailed ways

In order to enable those skilled in the art to better understand that the technical solutions of the present invention can be implemented, the present invention will be further described below in conjunction with specific examples and accompanying drawings, but the given examples are not intended to limit the present invention. The following test methods and detection methods, if not specified, are conventional methods; the reagents and raw materials, if not specified, are commercially available.

Example 1 (CS/K-car/C ₃ N ₄ -0.2%)

A preparation method for adsorbing hemoglobin hydrogel, comprising the following steps:

S1, dissolving chitosan in an acetic acid solution with a mass percentage of 2% to form a chitosan solution, adding calcium chloride to the chitosan solution, and mixing to obtain a mixture of calcium chloride and chitosan solution; in the above mixed solution, the molar concentration of calcium chloride is 0.1mol/L, and the mass concentration of chitosan is 10mg/mL;

Ultrasonic disperse the carbon nitride powder in distilled water to obtain a carbon nitride solution, add carrageenan to the carbon nitride solution, and mix well to obtain a carrageenan carbon nitride mixture; the amount of carbon nitride in the above mixture The mass percentage is 0.2%, and the mass concentration of carrageenan is 20mg/mL;

S2, at room temperature, according to the mass ratio of 1:2, the carrageenan carbon nitride mixture of S1 is added dropwise to the mixed solution of calcium chloride and chitosan to form gel beads, cross-linked for 20min, and washed to obtain Wet-like hydrogel;

S3, freeze-drying the wet hydrogel described in S2 to obtain a hydrogel that absorbs hemoglobin.

The freeze-drying procedure is: the freeze-drying procedure is: put the wet sample hydrogel of S2 in a centrifuge tube, freeze at -20°C for 2 hours, wrap the mouth of the frozen centrifuge tube with a parafilm, and seal it with the parafilm , put into freeze drier and dry for 6h.

Example 2 (CS/K-car/C ₃ N ₄ -0.4%)

A preparation method for adsorbing hemoglobin hydrogel, comprising the following steps:

S1, dissolving chitosan in an acetic acid solution with a mass percentage of 2% to form a chitosan solution, adding calcium chloride to the chitosan solution, and mixing to obtain a mixture of calcium chloride and chitosan solution; in the above mixed solution, the molar concentration of calcium chloride is 0.1mol/L, and the mass concentration of chitosan is 10mg/mL;

Ultrasonic disperse the carbon nitride powder in distilled water to obtain a carbon nitride solution, add carrageenan to the carbon nitride solution, and mix well to obtain a carrageenan carbon nitride mixture; the amount of carbon nitride in the above mixture The mass percentage is 0.4%, and the mass concentration of carrageenan is 20mg/mL;

S2, at room temperature, according to the mass ratio of 1:2, the carrageenan carbon nitride mixture of S1 is added dropwise to the mixed solution of calcium chloride and chitosan to form gel beads, cross-linked for 20min, and washed to obtain Wet-like hydrogel;

S3, freeze-drying the wet hydrogel described in S2 to obtain a hydrogel that absorbs hemoglobin.

The freeze-drying procedure is: the freeze-drying procedure is: put the wet sample hydrogel of S2 in a centrifuge tube, freeze at -20°C for 2 hours, wrap the mouth of the frozen centrifuge tube with a parafilm, and seal it with the parafilm , put into freeze drier and dry for 6h.

Example 3

A preparation method for adsorbing hemoglobin hydrogel, comprising the following steps:

S1, dissolving chitosan in an acetic acid solution with a mass percentage of 2% to form a chitosan solution, adding calcium chloride to the chitosan solution, and mixing to obtain a mixture of calcium chloride and chitosan solution; in the above mixed solution, the molar concentration of calcium chloride is 0.1mol/L, and the mass concentration of chitosan is 10mg/mL;

Ultrasonic disperse the carbon nitride powder in distilled water to obtain a carbon nitride solution, add carrageenan to the carbon nitride solution, and mix well to obtain a carrageenan carbon nitride mixture; the amount of carbon nitride in the above mixture The mass percentage is 0.3%, and the mass concentration of carrageenan is 20mg/mL;

S2, at room temperature, according to the mass ratio of 1:2, the carrageenan carbon nitride mixture of S1 is added dropwise to the mixed solution of calcium chloride and chitosan to form gel beads, cross-linked for 30min, and washed to obtain Wet-like hydrogel;

S3, freeze-drying the wet hydrogel described in S2 to obtain a hydrogel that absorbs hemoglobin.

The freeze-drying procedure is: the freeze-drying procedure is: put the wet sample hydrogel of S2 in a centrifuge tube, freeze at -20°C for 6 hours, wrap the mouth of the frozen centrifuge tube with a parafilm, and seal it with the parafilm , put into the freeze dryer and dry for 8h.

Example 4

A preparation method for adsorbing hemoglobin hydrogel, comprising the following steps:

S1, dissolving chitosan in an acetic acid solution with a mass percentage of 2% to form a chitosan solution, adding calcium chloride to the chitosan solution, and mixing to obtain a mixture of calcium chloride and chitosan solution; in the above mixed solution, the molar concentration of calcium chloride is 0.1mol/L, and the mass concentration of chitosan is 10mg/mL;

Ultrasonic disperse the carbon nitride powder in distilled water to obtain a carbon nitride solution, add carrageenan to the carbon nitride solution, and mix well to obtain a carrageenan carbon nitride mixture; the amount of carbon nitride in the above mixture The mass percentage is 0.25%, and the mass concentration of carrageenan is 20mg/mL;

S2, at room temperature, according to the mass ratio of 1:2, the carrageenan carbon nitride mixture of S1 is added dropwise to the mixed solution of calcium chloride and chitosan to form gel beads, cross-linked for 22min, and washed to obtain Wet-like hydrogel;

S3, freeze-drying the wet hydrogel described in S2 to obtain a hydrogel that absorbs hemoglobin.

The freeze-drying procedure is: the freeze-drying procedure is: put the wet sample hydrogel of S2 in a centrifuge tube, freeze at -20°C for 4 hours, wrap the mouth of the frozen centrifuge tube with a parafilm, and seal it with the parafilm , put into freeze drier and dry for 6.5h.

Example 5

A preparation method for adsorbing hemoglobin hydrogel, comprising the following steps:

S1, dissolving chitosan in an acetic acid solution with a mass percentage of 2% to form a chitosan solution, adding calcium chloride to the chitosan solution, and mixing to obtain a mixture of calcium chloride and chitosan solution; in the above mixed solution, the molar concentration of calcium chloride is 0.1mol/L, and the mass concentration of chitosan is 10mg/mL;

Ultrasonic disperse the carbon nitride powder in distilled water to obtain a carbon nitride solution, add carrageenan to the carbon nitride solution, and mix well to obtain a carrageenan carbon nitride mixture; the amount of carbon nitride in the above mixture The mass percentage is 0.35%, and the mass concentration of carrageenan is 20mg/mL;

S2, at room temperature, according to the mass ratio of 1:2, the carrageenan carbon nitride mixture of S1 is added dropwise to the mixed solution of calcium chloride and chitosan to form gel beads, cross-linked for 28min, and washed to obtain Wet-like hydrogel;

S3, freeze-drying the wet hydrogel described in S2 to obtain a hydrogel that absorbs hemoglobin.

The freeze-drying procedure is: the freeze-drying procedure is: put the wet sample hydrogel of S2 in a centrifuge tube, freeze at -20°C for 5 hours, wrap the mouth of the frozen centrifuge tube with a parafilm, and seal it with the parafilm , put into the freeze dryer and dry for 7.5h.

In order to further illustrate the technical effect of the present invention, the present invention is also provided with comparative examples, as follows:

Comparative example 1 (CS/K-car)

A preparation method for a hydrogel adsorbing hemoglobin, comprising the following steps:

S1, dissolving chitosan in an acetic acid solution with a mass percentage of 2% to form a chitosan solution, adding calcium chloride to the chitosan solution, and mixing to obtain a mixture of calcium chloride and chitosan solution; in the above mixed solution, the molar concentration of calcium chloride is 0.1mol/L, and the mass concentration of chitosan is 10mg/mL;

Prepare a carrageenan solution with a mass concentration of 20 mg/mL;

S2, at room temperature, add the carrageenan solution of S1 dropwise to the mixed solution of calcium chloride and chitosan according to the mass ratio of 1:2 to form gel beads, crosslink for 20min, and wash to obtain wet sample hydrogel glue;

S3, freeze-drying the wet hydrogel described in S2 to obtain a hydrogel that absorbs hemoglobin.

The freeze-drying procedure is: the freeze-drying procedure is: put the wet sample hydrogel of S2 in a centrifuge tube, freeze at -20°C for 2 hours, wrap the mouth of the frozen centrifuge tube with a parafilm, and seal it with the parafilm , put into freeze drier and dry for 6h.

1. Morphological characteristics of the hydrogel adsorbing hemoglobin of the present invention

The technical effects of the hemoglobin-absorbing hydrogels prepared in the above-mentioned Examples 1-5 are similar. The present invention only takes Examples 1 and 2 as examples, and the prepared hemoglobin-absorbing hydrogels and the shell The scanning electron micrograph of the polysaccharide/carrageenan hydrogel is shown in Figure 1.

As can be seen from Figure 1, it can be seen from Figure A in Figure 1 that the dry CS/K-Car in Comparative Example 1 has particles and is not smooth, and it can be seen from Figures B and C in Figure 1 that the compound with carbon nitride added The surface of the hydrogel is relatively smooth and the texture is uniform.

Two, the adsorption property test of the hydrogel of the present invention adsorbing hemoglobin

Take 2 mL of blood from the rat heart, centrifuge at 800rpm for 5 minutes, discard the supernatant, collect red blood cells, suspend the red blood cells with diluted phosphate buffered saline (PBS), oscillate to break the red blood cells and release hemoglobin, and centrifuge at 13000rpm for 5 minutes to obtain the hemoglobin supernatant liquid. Take 5 mg of Comparative Example 1 (CS/K-Car), Example 1 (CS/K-Car/C ₃ N ₄ -0.2%), Example 2 (CS/K-Car/C ₃ N ₄ -0.4% ) hydrogel adsorbent into centrifuge tubes, add 2mL hemoglobin supernatant respectively, shake the shaker at 37°C for adsorption, centrifuge the suspension regularly at different time periods, measure the concentration in the solution supernatant with a microplate reader, Hb The absorbance was measured at 540nm, and the adsorption capacity (mg/g) of Hb was calculated by the mass balance equation to calculate the adsorption capacity of different hydrogels to hemoglobin, as shown in Figure 2. Calculate the adsorption capacity of the hemoglobin of the composite hydrogel pair according to the formula, which is calculated by the following formula:

q _t =[(C ₀ -C ₁ )×V]/m

Among them, C ₀ is the concentration of hemoglobin in the sample solution before adsorption; C ₁ is the concentration of hemoglobin in the sample supernatant after adsorption at different time periods; V is the volume (L) of the added solution; m is the weight of the hydrogel.

It can be seen from Figure 2 that the CS/K-car of Comparative Example 1, the CS/K-car/C ₃ N ₄ -0.2% of Example 1, and the CS/K-car/C ₃ N ₄ -0.4% of Example 2 The adsorption equilibrium was reached at 120 minutes, and the adsorption amounts to hemoglobin were 120.60mg/g, 150.39mg/g, and 178.82mg/g, respectively. It can be seen that the hydrogels added with carbon nitride in Examples 1 and 2 have a higher adsorption capacity for hemoglobin than the hydrogel without carbon nitride added in Comparative Example 1.

3. Blood compatibility test

(1) Activated partial thromboplastin time (APTT) and plasma thrombin time (TT) tests

Take 5 mg of the three hydrogel materials of Comparative Example 1, Example 1, and Example 2 respectively, place them in 1 mL of platelet-poor plasma and incubate at 37°C for 1 hour, and use a blank tissue culture plate (TCP) without specimens as a control group (Control group) , using the coagulation analysis system for APTT and TT tests, the results are shown in Figure 3 and Figure 4.

It can be seen from Figure 3 and Figure 4 that the CS/K-Car of Comparative Example 1, the CS/K-Car/C ₃ N ₄ -0.2% of Example 1, and the CS/K-Car/C ₃ N ₄ of Example 2 -0.4% activated partial thromboplastin time (APTT) were 25.33s, 25.83s, 25.52s, plasma thrombin time (TT) were 16.47s, 16.51s, 16.40s. Compared with the control group, the hydrogel did not cause large changes in activated partial thromboplastin time (APTT) and plasma thrombin time (TT), and had good hemocompatibility.

(2) Hemolysis rate

Collect blood from the heart of SD rats with a blood collection needle, inject it into a centrifuge tube containing heparin, centrifuge the tube at 5000rpm for 8min, discard the supernatant, then dilute the normal saline and precipitated red blood cells into an appropriate concentration of red blood cell suspension, and at the same time, the control sample 1. Take 5 mg of the three hydrogel materials of Embodiment 1 and Embodiment 2, and add 2 mL of the prepared erythrocyte suspension respectively. Add 2 mL of sterile distilled water to the positive control group (+), and add 2 mL of normal saline to the negative control group (-). At the same time, all test tubes were incubated in a water bath at 37°C for 2h. The samples to be tested were centrifuged at 2000 rpm for 10 min in turn, the supernatant was taken and placed in a 96-well plate, and the absorbance value was detected at 540 nm using a microplate reader. The hemolysis rate (HR) was calculated as follows:

A ₀ is the absorbance of the experimental group; A ₁ is the absorbance of the positive control group; A ₂ is the absorbance of the negative control group, each group is calculated 3 times to obtain the HR value, and the results are shown in Figure 5.

It can be seen from Figure 5 that the CS/K-Car of Comparative Example 1, the CS/K-Car/C ₃ N ₄ -0.2% of Example 1, and the CS/K-Car/C ₃ N ₄ -0.4% of Example 2 The hemolysis rates were 1.78%, 1.62%, and 1.72%, respectively. It can be seen that the addition of carbon nitride and the increase of the content will not cause the increase of the hemolysis rate.

Obviously, those skilled in the art can make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if these modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalent technologies, the present invention also intends to include these modifications and variations.

Claims (9)

1. A preparation method for a hydrogel adsorbing hemoglobin, comprising the following steps: S1, dissolving chitosan in an acetic acid solution to form a chitosan solution, adding calcium chloride to the chitosan solution, and mixing to obtain a mixed solution of calcium chloride and chitosan; Ultrasonic dispersion of carbon nitride powder in distilled water to obtain a carbon nitride solution, adding carrageenan to the carbon nitride solution, and mixing to obtain a carrageenan carbon nitride mixture; S2, at room temperature, add the carrageenan carbon nitride mixture of S1 dropwise to the mixed solution of calcium chloride and chitosan to form gel beads, cross-link, and wash to obtain a wet-like hydrogel; S3, freeze-drying the wet hydrogel described in S2 to obtain a hydrogel that absorbs hemoglobin. 2. The preparation method according to claim 1, characterized in that, in S1, the mass percentage of acetic acid in the acetic acid solution is 2%. 3. preparation method according to claim 1 is characterized in that, in S1, in the mixed solution of described calcium chloride and chitosan, the amount concentration of the substance of calcium chloride is 0.1mol/L, and chitosan The mass concentration is 10mg/mL. 4. The preparation method according to claim 1, characterized in that, in S1, in the carrageenan carbon nitride mixture, the mass percentage of carbon nitride is 0.2%-0.4%. 5. The preparation method according to claim 1, characterized in that, in S1, the mass concentration of carrageenan in the carrageenan carbon nitride mixture is 20 mg/mL. 6. preparation method according to claim 1 is characterized in that, in S2, the consumption ratio of the mixed solution of described carrageenan carbon nitride mixed solution and calcium chloride and chitosan is 1:2. 7. The preparation method according to claim 1, characterized in that, in S2, the cross-linking time is 20-30 minutes. 8. The preparation method according to claim 1, characterized in that, in S3, the freeze-drying procedure is as follows: put the wet sample hydrogel of S2 in a centrifuge tube, freeze at -20°C for 2-6 hours, freeze the frozen The mouth of the centrifuge tube was wrapped with a parafilm, tied with the parafilm, and dried in a freeze dryer for 6-8 hours. 9. A hydrogel for absorbing hemoglobin prepared by the preparation method according to any one of claims 1-8.