Mechanical Properties,Biodegradation And Biocompatibility Evaluation Of Biodegradable Zn-1.2Mg-0.1Ca Alloy For Medical Application

Part?: Preparation and mechanical properties of biodegradable Zn-1.2Mg-0.1Ca alloy for medical applicationBackground: Once the permanent metal implant enters human body,it will slowly release the metal ion,causing the inflammation of the surrounding tissues and organs.In order to achieve the purpose of fixing treatment,the patients need to remove the implant by reoperation,which will not only bring pain to the patients,but also bring economic burden.Biodegradable metal has good mechanical properties and biocompatibility,and biodegradability.In recent years,it gradually came into the eyes of researchers.The mechanical properties of magnesium and its alloys are similar to those of normal bone tissue,and the ions produced by degradation are highly biocompatible.However,the biggest drawback of magnesium based alloys is that the degradation rate is too fast to complete the target before bone healing.Zinc and its alloys have become a new choice because of their inertia and similar mechanical properties.In addition,zinc is one of the essential elements of the human body,plays a great role in the metabolism of the human body.According to the existing literature,Mg is an effective alloying element to enhance the mechanical properties of zinc alloy,and the mass percentage of magnesium alloy shows good strength and hardness at 0.93% and 1.55%.In addition,Ca is an essential element for human life,and it is the most abundant metal elements content.Ca exists in 99% teeth and bones,to maintain the support function of the teeth and bones,while Ca is a kind of important alloying element and it is used to improve the mechanical properties of zinc and zinc alloys.Objective: The Zn-1.2Mg-0.1Ca alloy was prepared and the properties of the composites were further improved by hot rolling.The effects of hot rolling on the microstructure and mechanical properties of Zn-1.2Mg-0.1Ca alloy were investigated.Methods: Zn-Mg-Ca alloy with the nominal composition of Zn-1.2Mg-0.1Ca alloy was melted at 460oC-480 oC under the protection of CO2 with pure Zn,pure Mg and pure Ca as the raw materials.The actual chemical composition of the alloy ingots by inductively coupled plasma atomic emission spectroscopy was Zn-1.13Mg-0.11 Ca.In addition,X ray diffraction and electron microscope was used to scan the alloy specimen,observe the microstructure and phase structure.The cast and rolled zinc alloys were made into tensile specimen,and the tensile test was made in the universal material testing machine.Scanning electron microscope was used to observe the sample fractography after tensile test.Microhardness test was carried out in a microhardness tester.Results: Because of the introduction of Ca,Zn-1.2Mg-0.1Ca alloy in the dendrites formed clear water chestnut Ca Zn13 phase,which will enhance the strength and hardness of the alloy.After the rolling processing,the microstructure showed a certain orientation,the eutectic microstructure and precipitates along the grain boundary arrangement,showed more excellent mechanical energy(YS 209.04 MPa,UTS 331.51 MPa 35.43%,EL and 103.47 Hv).Conclusion: The preparation of Zn-1.2Mg-0.1Ca alloy and the experimental study show that the rolled Zn-1.2Mg-0.1Ca alloy has relatively good mechanical properties,and can be used as a new biodegradable material.Part?: In vitro degradation behavior and biocompatibility evaluation of biodegradable Zn-1.2Mg-0.1Ca alloy for medical applicationBackground:Compared with polymer materials and ceramics,metal has high strength and hardness.So as a biomedical material,biodegradable metals are widely used as cardiovascular interventional devices and in the department of orthopedics.However,the traditional metal materials such as stainless steel,cobalt chromium alloy and titanium alloy,with high corrosion resistance,are used for permanent plants,applling to the human body.Once entered into the human body,the implant may release metal ions,causing inflammation of the surrounding tissues and organs.In order to achieve the purpose of fixing treatment,the patients need to be remove the implant by reoperations,which will not only bring pain to the patient,but also bring economic burden.Medical degradable metal has good mechanical properties,biocompatibility and biodegradability.In recent years,it gradually came into the eyes of researchers.The mechanical properties of magnesium and its alloys are similar to those of normal bone tissue,and the ions produced by degradation are highly biocompatible.However,the biggest drawback of magnesium based alloys is that the degradation rate is too fast,and it can not complete the fixing goal before the bone heals.Compared with magnesium alloys,zinc and its alloys have been selected for their metal inertia and similar mechanical properties.In addition,zinc is one of the essential elements of the human body,plays a great role in the metabolism of the human body.Considering the above factors,zinc can be used as a component of degradable metal.However,it is found that the mechanical properties of pure zinc are poor and can not be directly processed into plant equipment.Therefore,alloying treatment has become an essential process to increase the mechanical properties of zinc.The first part of the experiment proved that the extruded alloy has relatively better mechanical properties.This part of the experiment puts emphasis on the corrosion performance of the alloy,blood compatibility and cell toxicity research.The in vitro degradation behavior and biocompatibility in vitro was also observed.Objective: The Zn-1.2Mg-0.1Ca alloy was prepared,and the comprehensive properties of Zn-1.2Mg-0.1Ca alloy were further improved by hot rolling treatment.The corrosion properties,blood compatibility and cytotoxicity of Zn-1.2Mg-0.1Ca alloy were investigated.Methods: We evaluated the in vitro degradation by electrochemical test and immersion test of the alloy,the water contact angle experiment,the hydrophilicity of the alloys evaluation.By hemolysis rate test and platelet adhesion rate,we evaluated the blood compatibility of the alloy.The cytotoxicity experiments was carried out to evaluate cell tolerance of the alloy.Results:1.The Zn-1.2Mg-0.1Ca alloy has ideal corrosion rate.Electrochemical experimental results indicated that the corrosion rate of rolled Zn-1.2Mg-0.1Ca alloy is 0.250 mm/year,immersion experiment results showed that the corrosion rate is 0.103 mm/year.2.Zn-1.2Mg-0.1Ca alloy had hydrophilic.The hemolysis rate of the alloy was far lower than 5%,so it would not lead to the destruction of blood components.The platelet adhesion performance of the alloy was good,it would not cause blood coagulation,exhibiting good blood compatibility;3.The cytotoxicity of Zn-1.2Mg-0.1Ca alloy in vitro showed that MG63 cells had good tolerance to the alloy,and the 3T3 cells had the tolerance to the diluted extract,and had no obvious cytotoxicity.Conclusion: The above results showed that Zn-1.2Mg-0.1Ca alloy has good corrosion resistance and biocompatibility in vitro.The alloy can be used as a new biodegradable material for further study.Part ?: In vivo biocompatibility of biodegradable Zn-1.2Mg-0.1Ca alloy for medical applicationBackgrounds: The evaluation methods of biocompatibility of biomaterials can be divided into three parts: in vitro biocompatibility,in vivo biocompatibility and clinical trials.Through the first two parts of the study,it has been proved that the rolled Zn-1.2Mg-0.1Ca alloy has not only good mechanical properties and appropriate corrosion rate,but also has good biocompatibility in vitro.In order to further observe the biological properties,understand the interaction between Zn-1.2Mg-0.1Ca alloy and internal environment,study the process of degradation and the impact of degradation on bone and surrounding tissues,the compatibility test of rolled Zn-1.2Mg-0.1Ca alloy in vivo environment was carried out.In vivo biocompatibility test was used to evaluate the biological response of tissue to test materials.So far,in vivo implantation is still the main method to study the relationship between biomaterials and organism.Objective: To study the biocompatibility and safety of the alloy in New Zealand white rabbits.Methods: Rolled Zn-1.2Mg-0.1Ca alloy and WE43 magnesium alloy(as a reference)were made into columnar sample and implanted into the bone marrow of the femoral condyle of New Zealand rabbits.Regular monitoring of blood magnesium and zinc ion concentration was carried.By biochemical detection,slice observation of important organs,we evaluated the changes of liver and kidney function.Through Micro-CT scanning and hard tissue slice observation,we evaluated the degradation behavior and compatibility of the two kinds of alloys in rabbits.Results: After the operation,the vital signs of the rabbits were stable.The operation area was dry,and there was no swelling and infection.At 2 months,the wound healing of the experimental animals in the two groups was good.The trace of the wound disappeared,and the muscle and bone were well combined.There was no obvious subcutaneous bubble.X-ray observation was performed 1 week later,it showed that the prosthesis was Located in the marrow cavity.The biochemical test of peripheral blood showed that the liver and kidney function of rabbits were not affected,and the HE staining of vital organ slices showed that the structure and function of heart,liver,kidney and spleen were not significantly affected.Micro-CT scanning showed that compared with the magnesium alloy,the degradation rate of zinc alloy was slow,there was a small amount of bone formation,and the gas cavity was less than magnesium alloy.Hard tissue slices showed that there was a small amount of bone formation around the zinc alloy bar.Conclusion: 1.Implantted into the bone of New Zealand rabbits,zinc alloy had a low corrosion rate,and could provide enough mechanical support during the bone healing period.2.There was no inflammatory cell infiltrating in the interface between the zinc alloy and the bone tissue,and the formation of the membrane like substance was found not in the body.It had good binding ability with the bone tissue in vivo,and promoted the formation of new bone.3.There was no affecttion on the peripheral blood zinc ion concentration,liver and kidney function when the zinc alloy was implantting into the bone of animals.4.There was no change in the structure of the heart,liver and kidney of the New Zealand rabbits.It showed that the zinc alloy had good biocompatibility and biological security to the important tissues.