Preparation Of Biomimetic Hydrogel Coatings On The Surface Of Titanium Alloy Implants

As a metal based biomedical composite,titanium alloy has the advantages of high strength,low density,excellent corrosion resistance and low elastic modulus.It is the most widely used metal implant material for medical devices.Because most biomedical materials need to be used in the complex physiological environment in the body,the requirements for their performance are very strict.For example,titanium alloy implants entering the human body will cause adverse reactions with the host,including crevice corrosion,wear corrosion,inflammatory reaction,allergic reaction,etc.,and then cause irreversible damage to the patient's body.According to the contact and action position of the implants,it may further aggravate cardiovascular and cerebrovascular diseases and digestive tract malignant tumors.Based on the above problems,it is necessary to construct a functional coating on the surface of titanium alloy implant materials,which not only has good bioactivity and tribological properties,but also can quickly and efficiently sterilize.Natural polymer hydrogel is a new biomedical material with good biocompatibility,which can be used as an ideal carrier for drugs and antibacterial substances.Therefore,this paper will design a three-layer implant structure imitating the inner,middle and outer membranes of the blood vessel wall.The middle layer is a titanium alloy matrix,which plays a role in supporting the implant structure.The upper and lower layers are biomedical chitosan/gelatin/aldehyde hyaluronic acid titanium dioxide(CS/Gel/AHA-Ti O₂)composite hydrogel coatings prepared on the surface of titanium alloy by sol gel,dip pull and UV curing.On this basis,Ti O₂nanoparticles were loaded on the hydrogel coating as the carrier,so that the hydrogel coating can effectively and rapidly sterilize while having drug release and lubrication,thus giving the implant excellent antibacterial properties and higher service life.At the same time,the Ti O₂content and curing method are adjusted according to the living environment of the film layer to realize the functions of friction reduction,drug release,bacteriostasis and protection,so as to provide the possibility for patients to reduce the inflammatory or toxic reactions caused by implants in the postoperative recovery period.The main results are as follows:(1)biocompatible chitosan(CS),gelatin(Gel)and aldehyde hyaluronic acid(AHA)were prepared by Schiff base reaction to prepare composite hydrogels.The effects of CS and Gel components on the structure and properties of the composite hydrogel were also investigated.The increase of gel content provides denser and smaller pore structure.With the increase of temperature,it shows more obvious difference in phosphate buffer(PBS)with different p H,and the denser pore structure also provides faster release rate.The increase of CS content provided a more regular and larger pore structure,increased the initial swelling rate and initial release rate of hydrogel,and gave priority to the completion of the release process.The antibacterial effect of CS3 on Staphylococcus aureus was 90.6%±0.85%.In addition,the temperature changes in the sol state affect the viscosity of the hydrogel solution,which is possible for the successful attachment of the hydrogel on the substrate.(2)CS/Gel/AHA-TiO₂hydrogel coating on titanium alloy surface was prepared by immersion pulling method and modified nano Ti O₂was added.The addition of Ti O₂affects the regular arrangement of the polymer chains.In addition,Ti O₂can also enhance the molecular interaction among the hydrogels,improve the surface roughness of the coating,reduce the swelling rate,prolong the release time of lemon yellow,and inhibit the rate of Staphylococcus aureus and Escherichia coli to 96%±1.02%and 97%±0.96%.At the same time,the increase of Ti O₂will also improve the adhesion between the coating and the substrate.The pressure when Ti O₂-3 is scratched reaches 1.46 N,which is 1.5 times higher than that of Ti O₂free hydrogel coating,and effectively improves the hardness of the coating itself.The hydrogel coating can also effectively reduce the friction coefficient up to 93.6%,and compared with titanium alloy,the corrosion resistance has been significantly improved.(3)The adhesion,wear and corrosion resistance,swelling release and antibacterial properties of the coating were investigated by different curing methods.It is found that UV light curing can reduce the coating thickness,improve its hardness,reduce the roughness to 18 nm,and improve the adhesion with the substrate.UV light coating can further improve the antibacterial rate of the coating while maintaining the original corrosion resistance and friction reduction effect.As the density of the coating increased under UV light,the drug release rate of the coating exposed to UV light was the lowest,and the drug release rate of the coating exposed to(NH₄)₂SO₄solution was the highest.This paper provides a new idea for the construction of new functional coatings on titanium implants.CS/Gel/AHA hydrogel coatings loaded with Ti O₂nanoparticles with different contents were prepared on the surface of titanium alloy by imitating the three-layer structure design of blood vessel wall;Through a variety of curing methods,the hydrogel coating can not only release drugs on demand and improve lubrication,but also effectively and rapidly inhibit bacteria,thus giving the implant a higher service life.