Method for inhibiting migration of toxic small molecules in plastics based on protein-based phase transition composite coating

Abstract

The application discloses a method for inhibiting the migration of toxic small molecules in plastics based on a protein-based phase transition composite coating, which is characterized by the following steps: inducing the rapid phase transition of proteins on the surface of plastics by a disulfide bond reducing agent to form a nanofilm, and adsorbing polysaccharides on the surface of the nanofilm to form a protein-based phase transition composite coating on the surface of the plastics, which can inhibit the migration of toxic small molecules in the plastics. The preparation method of the protein-based phase transition composite coating is simple, the cost is low, the inhibition effect on the migration of phthalate plasticizers and bisphenol A in plastics (such as PVC, PP, PE, PS and PET) is good, the adsorption of drugs on the surface of medical plastics can be prevented at the same time, the protein-based phase transition composite coating has good biocompatibility, is suitable for temperature-sensitive plastics, has universality, can be safely used on the surface of food and medical plastic products, and has a good popularization and application prospect on the surface of plastics.

Description

TECHNICAL FIELD

[0001] The present application relates to an application for inhibiting the migration of plasticizers and other toxic small molecules on the surface of plastics (such as PVC, PP, PE, PS, PET). BACKGROUND

[0002] Plasticizers are widely used as additives in various plastic products, but during use, plasticizers are prone to migrate and diffuse from plastic products to the medium, which poses problems such as environmental pollution and harm to human health. Phthalate plasticizers are the most widely used plasticizers on the market (90%), and the addition amount in soft polyvinyl chloride (PVC) usually reaches 30-50 wt.%. Soft PVC is widely used in food packaging and medical products, and studies have shown that such plasticizers can affect the endocrine system of organisms and belong to environmental hormones that can cause cancer, teratogenicity and mutagenicity. At present, other environmentally friendly plasticizers with migration resistance have been used to replace phthalate plasticizers, but their widespread use is limited due to their high price, and the environmentally friendly plasticizers are still small molecules, which also have the problem of easy migration. Therefore, developing a surface coating that can effectively block the migration of plasticizers is the key to achieving the safety and durability of plastic products.

[0003] In recent years, many studies have used methods such as plasma and ultraviolet irradiation to crosslink the surface of plastics, which is beneficial to inhibit the migration of plasticizers, but irradiation crosslinking can cause a decrease in material properties and affect the color of the product. In addition, hydrophilic groups (such as polyethylene glycol) can be introduced on the surface of plastics by surface grafting to reduce the release rate of plasticizers in hydrophobic solvents. Compared with this, the surface coating method is relatively simple, and studies have used chemical vapor deposition to coat a nanoscale titanium layer on the surface of PVC; in addition, a SiO2 coating can be prepared on the surface of PVC by sol-gel method to inhibit the release of plasticizers. The above methods can inhibit the migration of plasticizers in plastics to some extent, but despite this, these methods are not suitable for temperature-sensitive plastics. Therefore, developing a universal surface coating that can be applied to the surface of food and medical plastic products and has a good inhibitory effect on the migration of plasticizers is of great significance for the safe use of plastics. SUMMARY

[0004] The purpose of the present application is to provide a method that can inhibit the migration of phthalate plasticizers and other toxic small molecules such as bisphenol A on the surface of plastic products.

[0005] For the above purpose, the method adopted by the present application is to form a protein-based phase transition composite coating on the surface of plastic, specifically to form a nanofilm on the surface of plastic by inducing rapid phase transition of protein through a disulfide bond reducing agent, and to adsorb polysaccharide on the surface of the nanofilm, so as to form a protein-based phase transition composite coating on the surface of plastic to inhibit the migration of toxic small molecules in plastic.

[0006] The above-mentioned toxic small molecules are phthalate plasticizers, and the corresponding proteins are any one of lysozyme, bovine serum albumin, insulin, alpha-lactalbumin, human serum albumin, fibrinogen, and beta-amyloid protein; or the toxic small molecules are any one of phthalate plasticizers, bisphenol A, toluene diisocyanate, and benzene, and the corresponding proteins are any one of lysozyme grafted with cyclodextrin and bovine serum albumin grafted with cyclodextrin. Among them, the phthalate plasticizer is any one or more of di(2-ethylhexyl) phthalate, dibutyl phthalate, butyl benzyl phthalate, dimethyl phthalate, diisononyl phthalate, diisodecyl phthalate, and dioctyl phthalate.

[0007] The above-mentioned disulfide bond reducing agent is any one of tris(2-carboxyethyl) phosphine hydrochloride, cysteine, glutathione, dimercaptosuccinic acid, 2-mercaptoethanol, sodium sulfite, and dithiothreitol, preferably any one of tris(2-carboxyethyl) phosphine hydrochloride, cysteine, and glutathione.

[0008] The above-mentioned polysaccharide is any one of sodium alginate, carboxymethyl chitosan, sodium carboxymethyl cellulose, sodium hyaluronate, sodium carboxymethyl starch, sodium chondroitin sulfate, sodium lignosulfonate, nanocellulose, and sodium heparin.

[0009] The preparation method of the protein-based phase transition composite coating is as follows: adding an equal volume of 15-100 mmol / L disulfide bond reducing agent aqueous solution with a pH value of 5.0-9.0 into a 2-50 mg / mL protein aqueous solution to obtain a protein phase transition solution; immersing a plastic film in the protein phase transition solution for 10 minutes to 12 hours at room temperature, then washing with water and immersing in a 0.5-4 mg / mL polysaccharide aqueous solution for 1-6 hours at room temperature, and finally washing with water, drying, and forming a protein-based phase transition composite coating on the surface of plastic.

[0010] Further preferably, the preparation method of the protein-based phase inversion composite coating is as follows: adding an equal volume of 50 mmol / L aqueous solution of a disulfide bond reducing agent with a pH value of 7.0 into 10-20 mg / mL aqueous solution of the protein to obtain a protein phase inversion solution; immersing a plastic film into the protein phase inversion solution for 2-4 hours at room temperature, then washing with water, and immersing into 2-3 mg / mL aqueous solution of the polysaccharide for 1-6 hours at room temperature, and finally washing with water and drying to form the protein-based phase inversion composite coating on the surface of the plastic.

[0011] The plastic is any one of polyvinyl chloride (PVC), polyethylene (PE), polypropylene (PP), polystyrene (PS), polyethylene terephthalate (PET), etc.

[0012] The present application has the following advantages:

[0013] The present application forms a nanometer film on the surface of the plastic by inducing the protein to rapidly phase invert through the disulfide bond reducing agent, and adsorbing the polysaccharide on the surface of the nanometer film, so as to form the protein-based phase inversion composite coating on the surface of the plastic to inhibit the migration of toxic small molecules in the plastic. The preparation method of the protein-based phase inversion composite coating is simple, low in cost, good in inhibition effect on the migration of phthalate plasticizers and bisphenol A in the plastic (such as PVC, PP, PE, PS, PET), etc., can simultaneously prevent the adsorption of drugs on the surface of the medical plastic, has good biocompatibility, is suitable for temperature-sensitive plastic, has universality, can be safely used on the surface of food and medical plastic products, and has good popularization and application prospect on the surface of the plastic. BRIEF DESCRIPTION OF DRAWINGS

[0014] Figure 1 FIG. 1 is a scanning electron microscope image of the PTL / SA composite coating in Example 1.

[0015] Figure 2 FIG. 2 is a pore size distribution graph of the PTL / SA composite coating in Example 1.

[0016] Figure 3 FIG. 3 is the DEHP leaching amount of the PTL / SA composite coating loaded on different plastics in 50% ethanol.

[0017] Figure 4 FIG. 4 is the DEHP leaching amount of the PTL / SA composite coating loaded on different plastics in 3% acetic acid.

[0018] Figure 5 FIG. 5 is the DEHP leaching amount of the blood bag, disposable infusion tube (10 cm long), and dialysis tube (10 cm long) loaded with the PTL / SA composite coating in 95% ethanol.

[0019] Figure 6Effect of solution pH on the inhibition of plasticizer migration in PVC loaded with PTL / SA composite coating.

[0020] Figure 7 Effect of different time on the inhibition of plasticizer migration in PVC loaded with PTL / SA composite coating.

[0021] Figure 8 Effect of different temperature on the inhibition of plasticizer migration in PVC loaded with PTL / SA composite coating.

[0022] Figure 9 Scanning electron microscope images of PVC plastic and PVC plastic loaded with PTL / SA composite coating incubated in platelet plasma.

[0023] Figure 10 Hemolysis test of PVC plastic and PVC plastic loaded with PTL / SA composite coating.

[0024] Figure 11 Effect of PTL / SA composite coating thickness on the inhibition of plasticizer migration.

[0025] Figure 12 Scanning electron microscope images of the coating formed on the surface of plastic film in the comparative example. DETAILED DESCRIPTION

[0026] The application will be further described in conjunction with the accompanying drawings and examples, but the scope of protection of the application is not limited to these examples.

[0027] Example 1

[0028] A 1 mL 20 mg / mL lysozyme (PTL) aqueous solution was added with 1 mL 50 mmol / L tris (2-carboxyethyl) phosphine hydrochloride aqueous solution with pH value of 7.0 to obtain a lysozyme phase inversion solution; a plastic film (polyvinyl chloride, polyethylene, polypropylene, polystyrene, polyethylene terephthalate) with a size of 1 cm x 1 cm was immersed in the lysozyme phase inversion solution, incubated at room temperature for 2 hours, then taken out, washed with water, and then immersed in 2 mL 2 mg / mL sodium alginate (SA) aqueous solution at room temperature for 2 hours, finally washed with water and dried to form a lysozyme phase inversion composite coating loaded with sodium alginate on the surface of the plastic film, denoted as PTL / SA, with a coating thickness of 210 nm (see Figure 1 ) and a coating pore size of 1.3 nm (see Figure 2 ).

[0029] Example 2

[0030] In this example, 2 mL of 1 mg / mL carboxylated chitosan aqueous solution is used to replace 2 mL of 2 mg / mL sodium alginate aqueous solution in Example 1, and other steps are the same as those in Example 1, to form a lysozyme phase inversion composite coating loaded with carboxylated chitosan on the surface of the plastic film.

[0031] Example 3

[0032] In this example, 2 mL of 0.5 mg / mL sodium carboxymethyl cellulose aqueous solution is used to replace 2 mL of 2 mg / mL sodium alginate aqueous solution in Example 1, and other steps are the same as those in Example 1, to form a lysozyme phase inversion composite coating loaded with sodium carboxymethyl cellulose on the surface of the plastic film.

[0033] Example 4

[0034] In this example, 2 mL of 4 mg / mL sodium hyaluronate aqueous solution is used to replace 2 mL of 2 mg / mL sodium alginate aqueous solution in Example 1, and other steps are the same as those in Example 1, to form a lysozyme phase inversion composite coating loaded with sodium hyaluronate on the surface of the plastic film.

[0035] Example 5

[0036] In this example, 2 mL of 2 mg / mL sodium heparin aqueous solution is used to replace 2 mL of 2 mg / mL sodium alginate aqueous solution in Example 1, and other steps are the same as those in Example 1, to form a lysozyme phase inversion composite coating loaded with sodium heparin on the surface of the plastic film.

[0037] Example 6

[0038] In this example, 1 mL of 50 mmol / L cysteine aqueous solution with pH value of 9 is used to replace 1 mL of 50 mmol / L tris(2-carboxyethyl)phosphine hydrochloride aqueous solution with pH value of 7 in Example 1, and other steps are the same as those in Example 1, to form a lysozyme phase inversion composite coating loaded with sodium alginate on the surface of the plastic film.

[0039] Example 7

[0040] In this example, 1 mL of 60 mmol / L glutathione aqueous solution with pH value of 7 is used to replace 1 mL of 50 mmol / L tris(2-carboxyethyl)phosphine hydrochloride aqueous solution with pH value of 7 in Example 1, and other steps are the same as those in Example 1, to form a lysozyme phase inversion composite coating loaded with sodium alginate on the surface of the plastic film.

[0041] Example 8

[0042] In this embodiment, 1 mL of 40 mmol / L dimercaptosuccinic acid aqueous solution with pH value of 7 was used to replace 1 mL of 50 mmol / L tris (2-carboxyethyl) phosphine hydrochloride aqueous solution with pH value of 7 in Example 1, and other steps were the same as those in Example 1, and a lysozyme phase inversion composite coating loaded with sodium alginate was formed on the surface of the plastic film.

[0043] Example 9

[0044] In this embodiment, 1 mL of 10 mg / mL bovine serum albumin aqueous solution was used to replace 1 mL of 20 mg / mL lysozyme aqueous solution in Example 1, and other steps were the same as those in Example 1, and a bovine serum albumin phase inversion composite coating loaded with sodium alginate was formed on the surface of the plastic film.

[0045] Example 10

[0046] In this embodiment, 1 mL of 20 mg / mL lysozyme grafted with cyclodextrin (PTL-CD, the grafting method is described in the reference “Qingmin Yang, Jian Zhao, Arif Muhammad, Rongrong Qin, Juanhua Tian, Ling Li, Qianhui Zhang, Lixin Chen, Peng Yang, An Amyloid-Like Proteinaceous Adsorbent for Uranium Extraction from Aqueous Medium, J. Mater. Chem. A. 2022, 10, 14906.”) was added with 1 mL of 25 mmol / L cysteine aqueous solution with pH value of 9.0 to obtain a lysozyme phase inversion solution grafted with cyclodextrin; a plastic film (polyvinyl chloride, polyethylene, polypropylene, polystyrene, polyethylene terephthalate) with a size of 1 cm x 1 cm was immersed in the lysozyme phase inversion solution grafted with cyclodextrin, taken out after incubation at room temperature for 2 hours, washed with water, and then immersed in 2 mL of 0.5 mg / mL sodium carboxymethyl cellulose aqueous solution for reaction at room temperature for 2 hours. Finally, the plastic film was washed with water and dried, and a lysozyme phase inversion composite coating grafted with cyclodextrin loaded with sodium carboxymethyl cellulose was formed on the surface of the plastic film, which was denoted as PTL-CD / CMC.

[0047] Example 11

[0048] In this example, 1 mL of 50 mg / mL grafted cyclodextrin bovine serum albumin (PTB-CD, the grafting method is referred to the grafting method of PTL-CD) was added with 1 mL of 100 mmol / L tris(2-carboxyethyl)phosphine hydrochloride aqueous solution with pH value of 5.0 to obtain a grafted cyclodextrin bovine serum albumin phase inversion solution; other steps were the same as those in Example 10 to form a grafted cyclodextrin bovine serum albumin phase inversion composite coating loaded with sodium carboxymethyl cellulose on the surface of a plastic film, which was denoted as PTB-CD / CMC.

[0049] In order to prove the beneficial effects of the present application, the surface of a plastic (polyvinyl chloride, polyethylene, polypropylene, polystyrene, polyethylene terephthalate), a blood bag, a disposable infusion tube (10 cm long), and a dialysis tube (10 cm long) was respectively formed with a lysozyme phase inversion composite coating (PTL / SA) loaded with sodium alginate according to the method of Example 1, and then the following experiments were performed:

[0050] 1. Effect of different leaching media on the inhibition of plasticizer migration by PTL / SA

[0051] 1) The plastic (polyvinyl chloride, polyethylene, polypropylene, polystyrene, polyethylene terephthalate) with the surface formed with a PTL / SA composite coating was respectively immersed in 2 mL of 50% ethanol aqueous solution, and then the plastic was taken out and the concentration of di(2-ethylhexyl) phthalate (DEHP) in the 50% ethanol aqueous solution was detected after the plastic was placed at 37°C for 1 hour. The results showed that, compared with the blank plastic (i.e. without coating), the amount of DEHP leached by the plastic with the surface formed with a PTL / SA composite coating was reduced (see Table 1). Figure 3 ) Table 1. Effect of different leaching media on the inhibition of plasticizer migration by PTL / SA

[0052] 2) The plastic (polyvinyl chloride, polyethylene, polypropylene, polystyrene, polyethylene terephthalate) with the surface formed with a PTL / SA composite coating was respectively immersed in 2 mL of 3% acetic acid aqueous solution, and then the plastic was taken out and the concentration of DEHP in the 3% acetic acid aqueous solution was detected after the plastic was placed at 37°C for 10 days. The results showed that, compared with the blank plastic (i.e. without coating), the amount of DEHP leached by the plastic with the surface formed with a PTL / SA composite coating was reduced (see Table 2). Figure 4 ) Table 2. Effect of different leaching media on the inhibition of plasticizer migration by PTL / SA

[0053] 3) Blood bags, disposable infusion tubing (10 cm long), and dialysis tubing (10 cm long) with PTL / SA composite coatings were immersed in a 95% ethanol aqueous solution and left to stand at 37°C for 1 hour. The concentration of DEHP in the 95% ethanol aqueous solution was then measured. The results showed that, compared to the control group (i.e., no coating), the leaching of DEHP from blood bags, disposable infusion tubing, and dialysis tubing with the PTL / SA composite coating was reduced by 50–1000 times (see...). Figure 5 ).

[0054] 2. The effect of solution pH on plasticizer migration

[0055] Polyvinyl chloride (PVC) plastics with a PTL / SA composite coating were immersed in aqueous solutions of different pH values ​​and left to stand at 37°C for 10 days. The plastics were then removed, and the concentration of DEHP in the aqueous solution was measured. The results showed that, compared to the blank PVC plastic (i.e., uncoated), the leaching amount of DEHP from the PVC plastics with the PTL / SA composite coating was reduced (see...). Figure 6 ).

[0056] 3. Effect of soaking time on plasticizer migration

[0057] Polyvinyl chloride plastic with a PTL / SA composite coating on its surface was immersed in a 95% ethanol aqueous solution and left to stand at 37°C for different times. The plastic was then removed and the concentration of DEHP in the 95% ethanol aqueous solution was measured. Figure 7 The results showed that the leaching rate of DEHP in PVC plastics with a PTL / SA composite coating on the surface was slowed down.

[0058] 4. The effect of temperature on plasticizer migration

[0059] Polyvinyl chloride (PVC) plastics with a PTL / SA composite coating were immersed in a 95% (v / v) ethanol aqueous solution and left to stand at 27°C and 40°C for 1 hour, respectively. The plastics were then removed, and the concentration of DEHP in the 95% ethanol aqueous solution was measured. The results showed that although the leaching amount of DEHP in the PVC plastics with the PTL / SA composite coating increased with increasing temperature, the leaching amount was still 66% lower than that in uncoated PVC plastics (see...). Figure 8 ).

[0060] 5. The influence of different external force environments on plasticizer migration

[0061] Polyvinyl chloride (PVC) plastic with a PTL / SA composite coating was subjected to various external forces, including stretching, bending at 90° for 500 cycles, tape tearing for 5 times, and agitation in flowing water for 5 hours. It was then immersed in a 95% ethanol aqueous solution and allowed to stand at 37°C for 1 hour. The plastic was then removed, and the concentration of DEHP in the 95% ethanol aqueous solution was measured. The results showed that, compared to the control, the DEHP leaching rate of the PVC plastic with the PTL / SA composite coating remained essentially unchanged after these external forces, with a leaching rate of approximately 8%.

[0062] As can be seen from the above, the PTL / SA composite coating has a good inhibitory effect on the migration of plasticizers in plastics.

[0063] Further testing was conducted to investigate the effects of different leaching media on the migration of bisphenol A and benzene. The specific experiments are as follows:

[0064] The PC plastic with the PTL-CD / CMC composite coating from Example 10 was immersed in 2 mL of 95% (v / v) ethanol aqueous solution and 2 mL of 50% (v / v) ethanol aqueous solution, respectively, and allowed to stand at 37°C for 1 hour. The plastic was then removed, and the concentration of bisphenol A in the solution was measured using gas chromatography-mass spectrometry (GC-MS). The results showed that, compared with the blank PC plastic (i.e., uncoated), the leaching amount of bisphenol A in the PC plastic with the PTL-CD / CMC composite coating was reduced by 20 times.

[0065] The PS plastic with the PTB-CD / CMC composite coating from Example 11 was immersed in 2 mL of 95% ethanol aqueous solution and 2 mL of n-hexane, respectively, and allowed to stand at 37°C for 1 hour. The plastic was then removed, and the concentration of benzene in the solution was measured using gas chromatography-mass spectrometry (GC-MS). The results showed that, compared with the blank PS plastic (i.e., uncoated), the leaching amount of benzene from the PS plastic with the PTB-CD / CMC composite coating was reduced by 35 times.

[0066] 6. Antifouling performance of protein-based phase transition composite coatings

[0067] 1) Adsorption of the drug: First, a PTL / SA composite coating was loaded onto the QCM chip according to the method in Example 1. During the test, the QCM chip was placed in the sample cell. Before introducing the sample, ultrapure water was first introduced into the sample cell, and this was used as a baseline after the signal stabilized. Then, 0.9% sodium chloride aqueous solution and 0.9% sodium chloride aqueous solution containing ciprofloxacin hydrochloride were introduced, and the changes in signal frequency and energy dissipation were recorded. After the signal stabilized, the chip was rinsed with ultrapure water, and the signal changes were recorded. The results showed that the PTL / SA composite coating could resist the adsorption of more than 95% of ciprofloxacin hydrochloride. Furthermore, the PTL / SA composite coating did not adsorb sucrose molecules in a 5% (w / w) sucrose aqueous solution.

[0068] 7. Biocompatibility of protein-based phase transition composite coatings

[0069] 1) Platelet adhesion: Fresh rabbit blood (or human blood) was added to sodium citrate anticoagulant tubes and centrifuged at 1000 rpm for 10 min. Equal amounts of platelet-rich mid-layer plasma were then added to the surfaces of blank PVC plastic and PVC plastic coated with a PTL / SA composite coating. The surfaces were incubated at 37℃ for the same time (30 min, 1 h, 2 h). The surfaces were then rinsed with physiological saline for the same amount of time, followed by fixation with 1% glutaraldehyde for 8 h. Dehydration was then performed using a gradient of 50%, 70%, 90%, and 100% ethanol, with each concentration set for 10 min. After drying, platelet adhesion was characterized by SEM. The results showed that the PTL / SA composite coating resisted platelet adhesion (see...). Figure 9 ).

[0070] 2) Coagulation test: Fresh rabbit blood (or human blood) was added to a sodium citrate anticoagulant tube and centrifuged at 1000 rpm for 10 min. Then, 200 μL of plasma was added to a PVC plastic surface coated with PTL / SA. After incubation at 37℃ for 1 h, the coagulation time was tested using a coagulation analyzer, APTT, and PT kits. The results showed that compared to uncoated PVC plastic, the PTL / SA composite coating prolonged the coagulation time by 12 s.

[0071] 3) Hemolysis test: A 12cm² area... 2 PVC plastic coated with a PTL / SA composite was immersed in 2 mL of physiological saline and incubated at 37°C for 72 h to obtain an extract. Fresh anticoagulated rabbit blood was centrifuged at 3000 rpm for 5 min, and rabbit erythrocytes were prepared with physiological saline to contain 2% erythrocytes. These were then added to the extract, ultrapure water, and physiological saline, respectively, and incubated at 37°C for 1 h. The absorbance at 545 nm was measured. The results showed that the PTL / SA composite coating did not exhibit significant hemolysis (see...). Figure 10 ).

[0072] 8. The effect of PTL / SA composite coating thickness on plasticizer migration

[0073] The preparation process of the lysozyme phase inversion solution was the same as in Example 1, except that the lysozyme concentration was changed to 2, 5, 10, 20, 30, and 50 mg / mL. Polyvinyl chloride (PVC) plastic films measuring 1 cm × 1 cm were immersed in different concentrations of lysozyme phase inversion solutions, incubated at room temperature for 2 hours, then removed, rinsed with water, and then immersed in 2 mL of 2 mg / mL sodium alginate aqueous solution. The reaction was carried out at room temperature for 2 hours, and finally the plastic films were rinsed with water and dried, forming PTL / SA composite coatings of different thicknesses on the surface of the plastic films. PVC plastic films with different thicknesses of PTL / SA composite coatings were then immersed in 2 mL of 95% ethanol aqueous solution and allowed to stand at 37°C for 1 hour. The plastic films were then removed, and the concentration of DEHP in the 95% ethanol aqueous solution was measured. The results showed that as the thickness of the composite coating increased, the leaching rate of DEHP gradually decreased (see...). Figure 11 ).

[0074] Comparative Example

[0075] In the coating preparation process, 1 mL of 20 mg / mL lysozyme aqueous solution and 1 mL of 2 mg / mL sodium alginate aqueous solution were first mixed, and then 1 mL of 50 mmol / L tris(2-carboxyethyl)phosphonic acid hydrochloride aqueous solution with a pH of 7.0 was added. A 1 cm × 1 cm polyvinyl chloride (PVC) plastic film was then immersed in the resulting solution and incubated at room temperature for 2 hours. Afterward, the film was removed, rinsed with water, and dried. Compared to Example 1, this preparation process only changed the order of addition of sodium alginate and tris(2-carboxyethyl)phosphonic acid hydrochloride, resulting in a coating thickness of 100 nm on the plastic film surface (see Example 1). Figure 12 The plastic film was immersed in 2 mL of a 50% ethanol aqueous solution and left to stand at 37°C for 1 hour. The leaching rate of DEHP was 2.3 ppm, which was higher than the 0.1 ppm leaching rate of DEHP in Example 1. This indicates that the order of sample addition during coating preparation significantly affects its effect on inhibiting plasticizer migration. This may be attributed to the initial interaction of proteins and polysaccharides; for example, the electrostatic interaction between lysozyme and sodium alginate leads to trace amounts of sedimentation, resulting in a reduction in the amount of protein in the bulk phase, thus reducing the coating thickness.

Claims

1. A method for inhibiting the migration of toxic small molecules in plastics based on protein-based phase transition composite coating, characterized in that, The method is to form a nanofilm on the plastic surface by inducing the protein to rapidly phase transition through a disulfide bond reducing agent, and to adsorb polysaccharides on the surface of the nanofilm, so as to form a protein-based phase transition composite coating on the plastic surface to inhibit the migration of toxic small molecules in the plastic. The preparation method of the protein-based phase transition composite coating is as follows: 2-50 mg / mL of a protein aqueous solution is added with an equal volume of a 15-100 mmol / L disulfide bond reducing agent aqueous solution with a pH value of 5.0-9.0 to obtain a protein phase transition solution; a plastic film is soaked in the protein phase transition solution and incubated at room temperature for 10 minutes to 12 hours, taken out, washed with water, and then soaked in a 0.5-4 mg / mL polysaccharide aqueous solution to react at room temperature for 1-6 hours, and finally washed with water and dried to form a protein-based phase transition composite coating on the plastic surface. The toxic small molecules are phthalate plasticizers, and the corresponding protein is any one of lysozyme, bovine serum albumin, insulin, alpha-lactalbumin, human serum albumin, fibrinogen, and beta-amyloid protein; or the toxic small molecules are any one of bisphenol A and benzene, and the corresponding protein is any one of lysozyme grafted with a cyclodextrin and bovine serum albumin grafted with a cyclodextrin. The disulfide bond reducing agent is any one of tris(2-carboxyethyl)phosphine hydrochloride, cysteine, glutathione, dimercaptosuccinic acid, 2-mercaptoethanol, sodium sulfite, and dithiothreitol. The polysaccharide is any one of sodium alginate, carboxymethyl chitosan, and sodium carboxymethyl cellulose.

2. The method for inhibiting the migration of toxic small molecules in plastics based on protein-based phase transition composite coating according to claim 1, characterized in that, The toxic small molecules are phthalate plasticizers, and the corresponding protein is any one of bovine serum albumin and lysozyme.

3. The method for inhibiting the migration of toxic small molecules in plastics based on protein-based phase transition composite coating according to claim 1 or 2, characterized in that, The phthalate plasticizer is any one or more of di(2-ethylhexyl) phthalate, dibutyl phthalate, butyl benzyl phthalate, dimethyl phthalate, diisononyl phthalate, diisodecyl phthalate, and dioctyl phthalate.

4. The method for inhibiting the migration of toxic small molecules in plastics based on protein-based phase transition composite coating according to claim 1, characterized in that, The disulfide bond reducing agent is any one of tris(2-carboxyethyl)phosphine hydrochloride, cysteine, and glutathione.

5. The method for inhibiting the migration of toxic small molecules in plastics based on protein-based phase transition composite coating according to claim 1, characterized in that, The preparation method of the protein-based phase transition composite coating is as follows: 10-20 mg / mL of a protein aqueous solution is added with an equal volume of a 50 mmol / L disulfide bond reducing agent aqueous solution with a pH value of 7.0 to obtain a protein phase transition solution; a plastic film is soaked in the protein phase transition solution and incubated at room temperature for 2-4 hours, taken out, washed with water, and then soaked in a 2-3 mg / mL polysaccharide aqueous solution to react at room temperature for 1-6 hours, and finally washed with water and dried to form a protein-based phase transition composite coating on the plastic surface.

6. The method for inhibiting the migration of toxic small molecules in plastics based on protein-based phase transition composite coating according to claim 1, characterized in that, The plastic is any one of polyvinyl chloride, polyethylene, polypropylene, polystyrene, and polyethylene terephthalate.

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