The method for preparing the chitosan/heparinized graphene oxide composite multilayer film on the surface of the medical magnesium alloy of claim 1, which is characterized in step 1), a method for preparing the heparinized graphene oxide comprises the following steps: 1.1) firstly, ultrasonically dispersing graphene oxide in an Na O H solution having a concentration in the range of 0.1 to 0.5 mol/L for 2 hours; 1.2) then adding excess ch l oroacetic acid to ultrasonically react for 2 to 4 hours; 1.3) repeatedly and centrifugally washing the solution to be neutral to remove impurities to obtain carboxylated graphene oxide; 1.4) ultrasonically dispersing the resulting carboxylated graphene oxide; 1.5) adding to a mixed solution of N,N'- dicyclohexylcarbodiimide and 4-(dimethylamino)pyridine to perform an oscillation reaction for 2 to 4 hours; 1.6) repeatedly and centrifugally washing the solution to remove impurities; 1.7) adding the activated graphene oxide to a heparin solution to fully react for 4 to 12 hours; and 1.8) finally obtaining heparinized graphene oxide after repeatedly centrifugal washing.

The method for preparing the chitosan/heparinized graphene oxide composite multilayer film on the surface of the medical magnesium alloy of claim 1, which is characterized in step 2), the chemical treatment on the magnesium alloy surface comprises the following steps: firstly washing the magnesium alloy and then immersing in the Na O H solution having a concentration in the range of 1 to 5 mol/L and treating at a temperature of 60 to 85 ° C for 8 to 24 hours.

The method for preparing the chitosan/heparinized graphene oxide composite multilayer film on the surface of the medical magnesium alloy of claim 1, which is characterized in step 2), the self-assembly method comprises the following steps: immersing the magnesium alloy treated by Na O H into a 16-phosphonohexadecanoic acid solution having a concentration in the range of 1 to 10 mmol/L for 12 to 24 hours, and taking a sample out and then treating in vacuum at a temperature of 110 0 C for 12 to 24 hours.

The method for preparing the chitosan/heparinized graphene oxide composite multilayer film on the surface of the medical magnesium alloy of claim 1, which is characterized in step 3), the covalent immobilizing method of chitosan comprises the following steps: 3.1) immersing the surface-modified sample obtained in step 2) in a mixed solution of N-(3- dimethylaminopropyl)- N'-ethylcarbodiimide/N-hydroxysuccinimide to react; 3.2) drying after reacting for 2 to 8 hours; 3.3) after drying, continuously reacting by immersing in a chitosan solution having a concentration in the range of 1 to 5 g/L; 3.4) after continuously reacting for 2 to 8 hours, washing and drying the sample to obtain a chitosan- modified positively charged magnesium alloy.

The method for preparing the chitosan/heparinized graphene oxide composite multilayer film on the surface of the medical magnesium alloy of claim 1, which is characterized in step 4), the method for preparing the chitosan/heparinized graphene oxide composite multilayer film comprises the following steps: alternately immersing the material obtained in step 3) in the heparinized graphene oxide having a concentration in the range of 0.1 to 1 mg/m l and the chitosan solution having a concentration in the range of 1 to 5 g/L, adsorbing for 20 to 60 minutes every time, and then fu ll y drying after adsorbing every time, thereby obtaining the chitosan/heparinized graphene oxide composite multilayer film.

The method for preparing the chitosan/heparinized graphene oxide composite multilayer film on the surface of the medical magnesium alloy of claim 1, which is characterized in step 1), a method for preparing the heparinized graphene oxide comprises the following steps: 1.1) firstly, ultrasonically dispersing graphene oxide in an Na O H solution having a concentration in the range of 0.1 to 0.5 mol/L for 2 hours; 1.2) then adding excess ch l oroacetic acid to ultrasonically react for 2 to 4 hours; 1.3) repeatedly and centrifugally washing the solution to be neutral to remove impurities to obtain carboxylated graphene oxide; 1.4) ultrasonically dispersing the resulting carboxylated graphene oxide; 1.5) adding to a mixed solution of N,N'- dicyclohexylcarbodiimide and 4-(dimethylamino)pyridine to perform an oscillation reaction for 2 to 4 hours; 1.6) repeatedly and centrifugally washing the solution to remove impurities; 1.7) adding the activated graphene oxide to a heparin solution to fully react for 4 to 12 hours; and 1.8) finally obtaining heparinized graphene oxide after repeatedly centrifugal washing.

The method for preparing the chitosan/heparinized graphene oxide composite multilayer film on the surface of the medical magnesium alloy of claim 1, which is characterized in step 2), the chemical treatment on the magnesium alloy surface comprises the following steps: firstly washing the magnesium alloy and then immersing in the Na O H solution having a concentration in the range of 1 to 5 mol/L and treating at a temperature of 60 to 85 ° C for 8 to 24 hours.

The method for preparing the chitosan/heparinized graphene oxide composite multilayer film on the surface of the medical magnesium alloy of claim 1, which is characterized in step 2), the self-assembly method comprises the following steps: immersing the magnesium alloy treated by Na O H into a 16-phosphonohexadecanoic acid solution having a concentration in the range of 1 to 10 mmol/L for 12 to 24 hours, and taking a sample out and then treating in vacuum at a temperature of 110 0 C for 12 to 24 hours.

The method for preparing the chitosan/heparinized graphene oxide composite multilayer film on the surface of the medical magnesium alloy of claim 1, which is characterized in step 3), the covalent immobilizing method of chitosan comprises the following steps: 3.1) immersing the surface-modified sample obtained in step 2) in a mixed solution of N-(3- dimethylaminopropyl)- N'-ethylcarbodiimide/N-hydroxysuccinimide to react; 3.2) drying after reacting for 2 to 8 hours; 3.3) after drying, continuously reacting by immersing in a chitosan solution having a concentration in the range of 1 to 5 g/L; 3.4) after continuously reacting for 2 to 8 hours, washing and drying the sample to obtain a chitosan- modified positively charged magnesium alloy.

The method for preparing the chitosan/heparinized graphene oxide composite multilayer film on the surface of the medical magnesium alloy of claim 1, which is characterized in step 4), the method for preparing the chitosan/heparinized graphene oxide composite multilayer film comprises the following steps: alternately immersing the material obtained in step 3) in the heparinized graphene oxide having a concentration in the range of 0.1 to 1 mg/m l and the chitosan solution having a concentration in the range of 1 to 5 g/L, adsorbing for 20 to 60 minutes every time, and then fu ll y drying after adsorbing every time, thereby obtaining the chitosan/heparinized graphene oxide composite multilayer film.

The method for preparing the chitosan/heparinized graphene oxide composite multilayer film on the surface of the medical magnesium alloy of claim 1, which is characterized in step 1), a method for preparing the heparinized graphene oxide comprises the following steps: 1.1) firstly, ultrasonically dispersing graphene oxide in an Na O H solution having a concentration in the range of 0.1 to 0.5 mol/L for 2 hours; 1.2) then adding excess ch l oroacetic acid to ultrasonically react for 2 to 4 hours; 1.3) repeatedly and centrifugally washing the solution to be neutral to remove impurities to obtain carboxylated graphene oxide; 1.4) ultrasonically dispersing the resulting carboxylated graphene oxide; 1.5) adding to a mixed solution of N,N'- dicyclohexylcarbodiimide and 4-(dimethylamino)pyridine to perform an oscillation reaction for 2 to 4 hours; 1.6) repeatedly and centrifugally washing the solution to remove impurities; 1.7) adding the activated graphene oxide to a heparin solution to fully react for 4 to 12 hours; and 1.8) finally obtaining heparinized graphene oxide after repeatedly centrifugal washing.

The method for preparing the chitosan/heparinized graphene oxide composite multilayer film on the surface of the medical magnesium alloy of claim 1, which is characterized in step 2), the chemical treatment on the magnesium alloy surface comprises the following steps: firstly washing the magnesium alloy and then immersing in the Na O H solution having a concentration in the range of 1 to 5 mol/L and treating at a temperature of 60 to 85 ° C for 8 to 24 hours.

The method for preparing the chitosan/heparinized graphene oxide composite multilayer film on the surface of the medical magnesium alloy of claim 1, which is characterized in step 2), the self-assembly method comprises the following steps: immersing the magnesium alloy treated by Na O H into a 16-phosphonohexadecanoic acid solution having a concentration in the range of 1 to 10 mmol/L for 12 to 24 hours, and taking a sample out and then treating in vacuum at a temperature of 110 0 C for 12 to 24 hours.

The method for preparing the chitosan/heparinized graphene oxide composite multilayer film on the surface of the medical magnesium alloy of claim 1, which is characterized in step 3), the covalent immobilizing method of chitosan comprises the following steps: 3.1) immersing the surface-modified sample obtained in step 2) in a mixed solution of N-(3- dimethylaminopropyl)- N'-ethylcarbodiimide/N-hydroxysuccinimide to react; 3.2) drying after reacting for 2 to 8 hours; 3.3) after drying, continuously reacting by immersing in a chitosan solution having a concentration in the range of 1 to 5 g/L; 3.4) after continuously reacting for 2 to 8 hours, washing and drying the sample to obtain a chitosan- modified positively charged magnesium alloy.

The method for preparing the chitosan/heparinized graphene oxide composite multilayer film on the surface of the medical magnesium alloy of claim 1, which is characterized in step 4), the method for preparing the chitosan/heparinized graphene oxide composite multilayer film comprises the following steps: alternately immersing the material obtained in step 3) in the heparinized graphene oxide having a concentration in the range of 0.1 to 1 mg/m l and the chitosan solution having a concentration in the range of 1 to 5 g/L, adsorbing for 20 to 60 minutes every time, and then fu ll y drying after adsorbing every time, thereby obtaining the chitosan/heparinized graphene oxide composite multilayer film.

The method for preparing the chitosan/heparinized graphene oxide composite multilayer film on the surface of the medical magnesium alloy of claim 1, which is characterized in step 1), a method for preparing the heparinized graphene oxide comprises the following steps: 1.1) firstly, ultrasonically dispersing graphene oxide in an Na O H solution having a concentration in the range of 0.1 to 0.5 mol/L for 2 hours; 1.2) then adding excess ch l oroacetic acid to ultrasonically react for 2 to 4 hours; 1.3) repeatedly and centrifugally washing the solution to be neutral to remove impurities to obtain carboxylated graphene oxide; 1.4) ultrasonically dispersing the resulting carboxylated graphene oxide; 1.5) adding to a mixed solution of N,N'- dicyclohexylcarbodiimide and 4-(dimethylamino)pyridine to perform an oscillation reaction for 2 to 4 hours; 1.6) repeatedly and centrifugally washing the solution to remove impurities; 1.7) adding the activated graphene oxide to a heparin solution to fully react for 4 to 12 hours; and 1.8) finally obtaining heparinized graphene oxide after repeatedly centrifugal washing.

The method for preparing the chitosan/heparinized graphene oxide composite multilayer film on the surface of the medical magnesium alloy of claim 1, which is characterized in step 2), the chemical treatment on the magnesium alloy surface comprises the following steps: firstly washing the magnesium alloy and then immersing in the Na O H solution having a concentration in the range of 1 to 5 mol/L and treating at a temperature of 60 to 85 ° C for 8 to 24 hours.

The method for preparing the chitosan/heparinized graphene oxide composite multilayer film on the surface of the medical magnesium alloy of claim 1, which is characterized in step 2), the self-assembly method comprises the following steps: immersing the magnesium alloy treated by Na O H into a 16-phosphonohexadecanoic acid solution having a concentration in the range of 1 to 10 mmol/L for 12 to 24 hours, and taking a sample out and then treating in vacuum at a temperature of 110 0 C for 12 to 24 hours.

The method for preparing the chitosan/heparinized graphene oxide composite multilayer film on the surface of the medical magnesium alloy of claim 1, which is characterized in step 3), the covalent immobilizing method of chitosan comprises the following steps: 3.1) immersing the surface-modified sample obtained in step 2) in a mixed solution of N-(3- dimethylaminopropyl)- N'-ethylcarbodiimide/N-hydroxysuccinimide to react; 3.2) drying after reacting for 2 to 8 hours; 3.3) after drying, continuously reacting by immersing in a chitosan solution having a concentration in the range of 1 to 5 g/L; 3.4) after continuously reacting for 2 to 8 hours, washing and drying the sample to obtain a chitosan- modified positively charged magnesium alloy.

The method for preparing the chitosan/heparinized graphene oxide composite multilayer film on the surface of the medical magnesium alloy of claim 1, which is characterized in step 4), the method for preparing the chitosan/heparinized graphene oxide composite multilayer film comprises the following steps: alternately immersing the material obtained in step 3) in the heparinized graphene oxide having a concentration in the range of 0.1 to 1 mg/m l and the chitosan solution having a concentration in the range of 1 to 5 g/L, adsorbing for 20 to 60 minutes every time, and then fu ll y drying after adsorbing every time, thereby obtaining the chitosan/heparinized graphene oxide composite multilayer film.