Construction And Properties Of PDMS Hydrophobic Layer On Biomedical Magnesium Surface

With the continuous progress of medical technology,people's requirements for medical treatment are gradually improved.They requirements for human implantable materials have gradually developed from non-degradable materials to degradable and absorbable materials.After the implantation of non-biodegradable materials into the human body,the implantation materials need to be removed from the human body through a second operation,it can lead to severe pain and complicated treatment.Biodegradable absorbent materials can avoid these problems,so biodegradable absorbent implant materials have become a hot topic in recent years.Magnesium and its alloys have good mechanical properties and biocompatibility.In addition,magnesium is an essential element in human body,so it has great potential as a biodegradable implantation material.Magnesium is a relatively active metal,and its rapid degradation rate is a key factor limiting its application.Rapid degradation of magnesium in vivo will release more hydrogen and lead to the increase of pH value around,which will affect the repair of surrounding tissues.Therefore,the key factor is improving the corrosion resistance of magnesium and its alloy.In this paper,two surface treatment methods,alkali treatment and silanization treatment,were used to modify the surface of pure magnesium sheet.Hydrophobic layers containing amino groups were constructed on the surface of 4,4,-diphenylmethane diisocyanate?MDI?and amino-terminated polydimethylsiloxane?H₂N-PDMS-NH₂?respectively by using the properties of MDI and amino reactions.The corrosion rate of magnesium is reduced by reducing the contact between magnesium substrate and water.The modified surface contains more amino groups,and the biocompatibility and the inducing ability of endothelial cells can be improved by grafting biological polypeptide molecules.The results showed that the water contact Angle of the pure magnesium tablets obtained by three times of recirculation graft of MDI and H₂N-PDMS-NH₂ after alkali treatment and silanization treatment respectively could reach 117.3°and 134.6°.Compared with the sample after alkali treatment and the sample surface after silanization treatment?28.7°,89.9°?.The hydrophobic property of grafted samples was improved obviously.The electrochemical test results showed that the impedance value of the samples that were cycled and grafted three times after alkali treatment was 98 Kohm/cm²,and the impedance value of the samples that were cycled and grafted three timesafter silanization was 165 Kohm/cm²,which was significantly higher than that of the samples that were treated with alkali and silanization?10Kohm/cm²,30 Kohm/cm²?.Compared with pure magnesium tablets,it increased by 14 and23.6 times respectively.The results of hydrogen evolution soaking for 10 days showed that the total volume of hydrogen released by the pure magnesium sheet was 3 times that of the sample after surface grafting modification.It can be seen that the surface modification of pure magnesium tablets using alkali treatment followed by silanization and then cyclic grafting of MDI and H₂N-PDMS-NH₂ can better improve the corrosion resistance.Biopeptides were grafted on the surface of samples that had been grafted three times after silanization.It was found that the number and survival rate of endothelial cells on the surface of samples grafted with biopeptides were higher than that of pure magnesium tablets by the growth of endothelial cells on the surface of samples.These results suggest that surface grafted polypeptides can increase the biocompatibility of magnesium.The results of subcutaneous implantation showed that the inflammatory response around the modified samples was smaller than that of the pure magnesium tablets and the vesicles were smaller than that of the pure magnesium tablets.In this paper,the hydrophobic layer is constructed on the surface of magnesium to reduce the contact between water and the magnesium substrate,reduce the corrosion rate of magnesium and improve the corrosion resistance of magnesium.The surface of the hydrophobic layer contains a large number of amino groups,which can provide a good platform for subsequent biological functionalization.