Search

CN-121971704-A - Preparation method of magnesium alloy bracket composite coating

CN121971704ACN 121971704 ACN121971704 ACN 121971704ACN-121971704-A

Abstract

The invention relates to a preparation method of a magnesium alloy stent composite coating, and belongs to the technical field of biomedical materials. Aiming at the technical problems of degradation and acid production and acceleration of corrosion of magnesium alloy brackets of the existing polyester coating, the composite coating with the piezoelectric-pH cooperative protection function is provided. The coating comprises a PVDF-g-APTES base coat, a pH regulating intermediate layer composed of PVDF, PDLLA and alkaline nano particles, and a drug-loaded PDLLA outer coating. According to the invention, the pH of an interface is actively raised to a passivation area through the on-demand release of the alkaline nano particles, and a positive feedback mechanism of 'more stress and more protection' is realized by utilizing a piezoelectric effect. Compared with the prior art, the dynamic corrosion resistance of the invention is enhanced by more than 40%, the synergistic effect improves the protection effect by more than 60%, the piezoelectric and alkaline synergistic protection is realized, and a long-acting corrosion-resistant intelligent response comprehensive solution is provided for the degradable magnesium alloy implantation instrument.

Inventors

  • SHEN XIN
  • CHEN XIANHUA
  • She jia

Assignees

  • 重庆大学

Dates

Publication Date
20260505
Application Date
20260409

Claims (7)

  1. 1. The preparation method of the magnesium alloy bracket composite coating is characterized by comprising the following steps: s1, preparation of a bottom coating: Dissolving 3-aminopropyl triethoxysilane modified polyvinylidene fluoride in N-methyl pyrrolidone to prepare a solution with the mass fraction of 5-10%, and spraying the solution on the surface of the pretreated magnesium alloy bracket to prepare a compact bottom coating with the thickness of 1-3 mu m; S2, preparation of an intermediate coating: preparing a middle coating solution: Dissolving polyvinylidene fluoride and poly-DL-lactic acid in a mixed solvent of N, N-dimethylformamide and acetone in a mass ratio of 3:7-7:3 to prepare a solution of 8-15% of the total mass fraction of the polyvinylidene fluoride and the poly-DL-lactic acid, adding 5-20% of LDH nano-sheets in mass fraction, 0.5-2% of photoinitiator Irgacure 2959 in mass fraction and 1-5% of crosslinking agent trimethylolpropane triacrylate in mass fraction, and performing ultrasonic dispersion for 30-60min at power of 200-400W to prepare an intermediate coating solution; And (2) coating an intermediate coating: Sequentially carrying out gradient spraying and depositing an intermediate coating solution with the mass ratio of polyvinylidene fluoride to poly-DL-lactic acid of 3:7-7:3 on the surface of the base coat, pre-baking 5-10 min layers at 60-80 ℃ after each layer of spraying, spraying 5-10 layers, wherein the thickness of the coating is 5-15 mu m, then adopting a high-pressure mercury lamp with the main wavelength of 365 nm and the power of 500-1000W, irradiating for 10-15 cm, irradiating for 10-30 min, and applying an electric field in the vertical direction in 30-60 min after spraying to prepare and form an intermediate coating; S3, preparation of a drug-loaded poly-DL-lactic acid surface layer: Rapamycin and poly-DL-lactic acid are dissolved in hexafluoroisopropanol to prepare a solution with the mass fraction of rapamycin of 3-8%, the solution is sprayed on the surface of an intermediate coating, and the intermediate coating is dried in vacuum at 40-60 ℃ for 12-24 h ℃ to remove residual solvent, so that the drug-loaded PDLLA surface layer with the thickness of 2-5 mu m is prepared.
  2. 2. The preparation method of the magnesium alloy bracket according to claim 1, wherein the electric field takes a magnesium alloy bracket substrate as a lower electrode and aluminum foil or copper foil as an upper electrode, the electric field strength is 10-50 MV/m, the temperature is increased to 80-120 ℃ at a temperature rising rate of 2-5 ℃ per minute, the time is 30-120 min, and the electric field is kept to be reduced to below 40 ℃ and then removed.
  3. 3. The method of claim 1, wherein the spray gun has a diameter of 0.3-0.5 mm, a spray distance of 10-15 cm, a gas pressure of 0.2-0.4 MPa, and a coating flow rate of 0.5-2 mL/min.
  4. 4. The preparation method of claim 1, wherein the preparation method of the LDH nanosheets comprises the following steps: Preparing Mg (mixed aqueous solution of NO 3 ) 2 ·6H 2 O and Al (NO 3 ) 3 ·9H 2 O), slowly dripping the mixed aqueous solution into NaNO 3 solution under the protection of nitrogen at 60-80 ℃, simultaneously dripping NaOH solution, adjusting pH=9.5-11.0, crystallizing 12-24 h at 80-100 ℃, centrifugally washing to pH=7, and vacuum drying at 60-80 ℃ to 12-24 h to obtain the LDH nanosheets.
  5. 5. The method of claim 4, wherein the molar ratio of Mg 2+ to Al 3+ is from about 2:1 to about 4:1, and the total concentration of Mg 2+ and Al 3+ metal ions is from about 0.5 to about 1.5 mol/L.
  6. 6. The preparation method of the magnesium alloy bracket is characterized in that the magnesium alloy bracket is sequentially subjected to grinding and polishing, acetone ultrasonic treatment of 10-15 min and absolute ethyl alcohol cleaning, then is placed in an ethanol solution of 3-aminopropyl triethoxysilane with the volume fraction of 2-5%, is soaked at 40-60 ℃ for 2-6 h, is washed by absolute ethyl alcohol, and is dried at 60-80 ℃ in vacuum for 2-4 h.
  7. 7. The magnesium alloy stent composite coating prepared by the preparation method according to any of claims 1-6.

Description

Preparation method of magnesium alloy bracket composite coating Technical Field The invention belongs to the technical field of biomedical materials, and relates to a preparation method of a magnesium alloy bracket composite coating. Background The magnesium alloy has wide application prospect in the field of medical implant materials due to good biodegradability and mechanical properties similar to human bones. However, magnesium alloys have too high corrosion rates in physiological environments and have limited clinical applications due to local pH elevation associated with hydrogen evolution reactions. In the prior art, patent CN201210184904. X discloses a medical magnesium alloy surface phytic acid micro-arc anodic oxide film, a polylactic acid coating and a process, wherein the technology prepares the phytic acid micro-arc anodic oxide film and the polylactic acid coating in a nanofiber network form on the magnesium alloy surface, and aims to regulate and control the corrosion rate. However, polylactic acid is degraded to generate lactic acid, which may cause the acidification of local microenvironment of a coating/magnesium alloy interface and accelerate the corrosion of magnesium alloy, a nanofiber network is of a continuous phase structure, has high porosity and can not effectively block moisture permeation, the fiber network itself forms a coating main body, the accurate load and controllable release of functional units are difficult to realize, in addition, the polylactic acid coating and the magnesium alloy substrate have limited binding force, moisture permeation is easy to amplify and adhere to defects, the coating is peeled off, microcracks are easy to generate under the action of mechanical stress such as stent expansion, no self-repairing mechanism exists, and the protection function is lost due to crack expansion. Patent CN201910168650.X proposes a preparation method of a magnesium alloy surface micro-arc oxidation film-LDHs composite film, wherein the method prepares a Mg-Al LDHs protective film by an in-situ growth mode to close holes of the micro-arc oxidation film. However, the LDHs exists in a continuous film form instead of a disperse phase, alkaline substances are exposed at one time, pH responsiveness regulation and control of release according to needs cannot be achieved, a polymer matrix is lacking in a coating system, interface combination of the LDHs film and a magnesium alloy matrix mainly depends on physical adsorption and mechanical interlocking, and binding force is limited, an inorganic salt coating is formed by stacking crystals, the porous characteristic of the inorganic salt coating limits the exertion of water blocking performance of the coating, pitting corrosion can be caused once moisture reaches a substrate through porous channels in the coating, the main functions of the coating are physical barrier and ion exchange, and the capability of actively regulating micro environments is lacking, so that the problem of pH dependency of magnesium alloy corrosion cannot be fundamentally solved. Patent CN202010404879.1 provides a medical magnesium alloy modified by a phytic acid/calcium phosphate composite film layer and a preparation method thereof, wherein the magnesium alloy is modified by a phytic acid conversion film on the inner layer and a calcium phosphate conversion film on the outer layer. However, the technology only adjusts pH in the preparation process, the coating has no dynamic response capability, the micro environment cannot be actively regulated in the service process, the pH buffering capability of the calcium-phosphorus salt conversion film is limited, the buffering function of the calcium-phosphorus salt conversion film is gradually lost along with degradation and ion exchange of the coating, the coating function is single, and the coating has insufficient toughness due to lack of mechanical enhancement and barrier cooperation of a polymer matrix, so that cracks are easy to generate under dynamic load. In addition, patent CN202410026507.8 discloses a medical magnesium alloy surface antibacterial corrosion-resistant coating and a preparation method thereof, wherein the coating is a double-layer composite coating formed by an inorganic porous inner layer and a flexible piezoelectric polymer outer layer. The technology introduces piezoelectric polymer, but the porosity defect of the inorganic inner layer is not overcome, water can still permeate through the pores of the inner layer, and meanwhile, the technology lacks the specific design for the key problem of 'pH dependency' in the corrosion behavior of magnesium alloy, and the problem of fluctuation of the pH value of an interface in the corrosion process cannot be effectively solved. Disclosure of Invention In view of the above, the invention aims to provide a magnesium alloy composite coating with piezoelectric-pH cooperative protection function and a preparation method thereof, by constructing a systema