Study On Preparation And Properties Of Silane / Sodium Hyaluronate Composite Coatings On Pure Magnesium

Compared with traditional medical metal materials,magnesium and its alloys have the advantages of light weight,high biocompatibility and non-toxicity,and their greatest characteristic is that they can be completely degraded in human body,which relieve the pain and economic burden caused by the second operation and the avoid the hidden danger caused by the long-term existence of implants in the body,so have been paid more and more attention in biomedical field.Meanwhile,it is significant that magnesium ions released slowly during the magnesium-based materials degradation also play a positive role in the treatment of ophthalmic diseases.At present,in the treatment of implantation of inert aqueous humor drainage device in the eye,the reason for the failure of the treatment is the scarring of scarby fibroblasts proliferation caused by persistent effects of inflammatory mediators and cytokines induced by foreign bodies,so the development of biodegradable drainage devices made of pure magnesium has great potential in biomedical applications.However,magnesium and its alloys will corrode immediately after implantation into the human body for their high activity,and producing a large amount of hydrogen and increasing the pH value,which is harmful to the implantation and surrounding position.Therefor,this text will control degradetion rate and improve biocompatibility by surface modification.The main resreach work is divided into the following parts:?1?Magnesium hydroxide film with active hydroxyl groups was prepared on the surface of pure magnesium by hydrothermal method,which can be used as a pre-treatment layer to protect the substrate and improve the bonding power to silane.Secondly,orthogonal experiment was used to optimize the preparation of silane film,the results showed that the optimum parameters were silane volume fraction 7%,hydrolysis time 48h,curing temperature 120?and curing time 90min.At last,the sodium hyaluronate of cross-linking modification by EDC/NHS was prepared on the silane coating,compared with the normal temperature drying method,the sodium hyaluronate film prepared by freeze-drying method had better corrosion resistance.?2?The corrosion resistance and physical-chemical properties of pure magnesium before and after modification were studied by a series of test methods.The results show that the corrosion current density of the composite film decreased by two orders of magnitude and the impedance value increased by three orders of magnitude,indicated that corrosion resistance of pure magnesium is greatly improved.The magnesium hydroxide prepared by hydrothermal method was composed of hexagonal nano-flakes with a roughness of 380.0nm and a thickness of 17.3?m.The silane was arranged in a fibrous structure,and the roughness decreased to about 2?m and with a roughness of96.2nm,and sodium hyaluronate film with a thickness of 1?m presented a spatial reticular structure,the roughness decreased further to 48.5nm.The hydroxyl groups were on the surface of Mg-OH,which made the sample show hydrophilicity,and the hydrophobicity groups Si-O-Si in Mg-B made the material show hydrophobicity.Hydrophilic groups in Mg-B-CHA made the surface of the material show hydrophilic.The adhesion of the composite coating increased from 17.8N of Mg-OH to 27.9N of Mg-B-CHA,suggeting that the composite coating had good bonding strength,which was beneficial to the collapse of the material under the severe environment.?3?The results of hydrogen evolution,pH value and Mg²⁺concentration all showed that the change rate of the measured values increased gradually at the early stages of immersion of the all samples due to the corrosion of magnesium matrix,and then due to the blocking effect of the composite coatings on water molecules and chloride ions,the growth rate of the measured values became slower,and all less than that of the unmodified pure magnesium.In the long-term immersion,Mg,Mg-OH and Mg-B mainly falled off in the form of blocks,while the number of seeds in Mg-B-CHA decreased gradually,the coating becomed thinner and finally breaked into pieces.And there were composite coatings after soaking 28 day,suggested that the modified pure magnesium had good corrosion resistance.?4?The results of cell experiment showed that the magnesium modified by composite coatings cytotoxicity level was 1,which showed good cell compatibility.The preliminary results of implatation experienment showed that compared with Mg,Mg-B-CHA had a lower rate of corrosion degradation and lower inflammatory cell response;During the implantation,the eye function of an animal was normal and without obvious rejection and adverse reactions.The results show that pure magnesium modified by silane/sodium hyaluronate composite coatings is promising to be used in aqueous humor drainage device,which brings a new direction for the treatment of ophthalmological diseases.