Dissertation > Medicine, health > Basic Medical > Medical science in general > Biomedical Engineering > General issues > Biomaterial

Research of Biocompatibility of the Biodegradable Fixation Materials Made by Magnesium Alloys

Author LiuJunYang
Tutor ZhaoJianWu
School Jilin University
Course Surgery
Keywords Magnesium alloy Hemolysis test Vivo test Histocompatibility
CLC R318.08
Type Master's thesis
Year 2013
Downloads 43
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Background: biomedical materials are the products of thecombination of the medicine and materials science. They have a veryimportant position in the clinical works, particularly surgicalworks. The most commonly used biomedical materials are including:medical metallic materials, medical organic materials, inorganicnon-metallic materials and bio-composites. Because of the highstrength, good toughness and good corrosion resistance, metallicmaterials are more suitable for the repair and replacement of humanbone tissue. The most widely used medical metallic materialsapplications, mainly including titanium, stainless steel,cobalt-chromium alloys. they faced many problems, such as thecorrosion of the physiological environment of heavy metal ionsdiffuse to the organization, and damaging to human health due tothe elastic modulus of bone tissue.It was significantly causingstress shielding, leading to the failure of internal fixation andcausing stress fractures. Metallic fixations are important infracture healing, and removing the internal fixation out ofpatients body increase the economic burden of patients. Therefore,the research and development of novel metal-based biologicalimplant material is required. Especially the biological properties are similar to human bones. If it can play a perfect fixed function,and even be able to promote bone and tissue repair, accelerate newbone tissue healing. when bone tissue are complete healed, theimplantation of biological material degraded. The degradationproducts are absorbed by the body, and non-toxic harmless. Magnesiumand magnesium alloys become the focus of biomedical materialsresearch. Its advantages are outstanding. The obvious advantagescompared with existing medical metallic materials are: firstly,magnesium as nutrients required of the body, are high bio-safety.It is the fourth metal ion contented in the human body. The WorldHealth Organization recommended adult daily magnesium intake of280~300mg, the Child need250mg and the infant need80mg. Magnesiumis obviously importance. The physiological function of themagnesium ions is embodied in a part of the enzyme involved inmetabolism. Secondly, magnesium excretion is through the urinarysystem. If the intake of magnesium too much, the body will notsignificantly elevate serum magnesium content. Thirdly, magnesiumand its alloys have a good bio-mechanical compatibility, the mostlikely to the metal material of the bone tissue, and effectivelyreducing stress shielding. Magnesium resources, is one of the mostreadily available metal elements. In view of the above advantages,magnesium and its alloys have being an important research direction in the field of biological material. But they also have shortcomings,such as localized corrosion, degradation behavior which is notcontrollable, plasticity, and poor mechanical properties.Magnesium alloy need a large number of work in vitro and in vivostudies to work in the clinical, such as magnesium alloy corrosionresistance, mechanical properties and tissue compatibility. Inrecent years, Mg-Zn-Mg-Ca-based alloys, is excellent in the fieldof biomedical materials performance. But there are some defects,so the detection of magnesium alloy s histocompatibility becomesthe focus. Mg-Zn-Ca-Y alloy made by Mg/Ca/Zn and a rare earth elementY. Alloy compatibility make the Mg-Zn-Ca-Y alloy body tissuecompatibility test system evaluation, observed as the likelihoodof the medical implant to provide impetus for the development ofbiomedical materials.Objective: This study of the relationship between the new Mg-Zn-Ca-Yalloys hemolysis rate and concentration of extracts andhistocompatibility system evaluation, while observing themeasurement of new alloy implanted in animals, animals, local tissueand systemic change of state, to analyze the effects on the body.Do the necessary testing and preparation, made the clinical safetyand satisfaction biodegradable alloys provide a scientific basisfor new materials used in clinical. Method: The first part, the extract liquid of the magnesium alloyprepared for different concentrations of100%,75%,50%,25%,10%,5%,2.5%,1%. According to GBT16886.4-2003" The Evaluation ofMedical Devices "Part4" Selection of tests for interactions withblood ", a hemolysis test. The second part, the implantations ofMg alloy are produced into some short rods. They are put into thesacral crest muscle.Though observation and measurement, we knowthe condition of white rabbits after implantation: weight, diet,ions level, liver function, renal function level, implant pointlocal tissue reactions, liver and kidney. We test the vein bloodof white rabbits to analyse the rabbits liver function afterimplantation, the ions and renal function to make sure whether thereis a change. After HE staining, we observe the fiber membranethickness and inflammatory changes. The fiber membrane thicknessand the decomposition of magnesium alloys is observed again byscanning electron microscopy.Results: The Mg-Zn-Ca-Y alloy extracts at100%,75%,50%,25%,10%,5%,2.5%and1%dilution rate of hemolysis were64.7%,62.4%,58.0%,34.2%,10.6%,4.7%,0.7%and0.2%. With the reduction of theconcentration of Mg+concentration gradually decreased, while thesodium ions in a substantially stable state, consider Mg+concentration is one of the principal factors affect the in vitro test hemolysis. After implanting in the sacral spine muscle, thecondition of Japanese white rabbits is good. HE staining resultsshowed that the fiber membrane is formed gradually after2weeks.The fiber membranes were thinner after12weeks. Magnesium alloysamples have no significant changes in the surface by the naked eyeafter implantation2weeks, but by the electron microscope, we cansee that the surface has many small cracks. As time goes on, thesamples were visually observed that the surface corrosion isincreasingly severe. The control group of titanium does not appearto corrosion with the naked eye, but though the electron microscopy,there are also some corrosions being observed. The experimentalgroup fiber membrane thickness is15.1μm, control group is11.4μm.Gas production was not observed with the naked eye after4weeks.Conclusion: In the vitro hemolytic test, the properties of theMg-Zn-Ca-Y alloy is not very well. It needs to improve. The reasonwhy it has a poor hemolytic property may be the decomposition ofMg+ions. Biocompatibility of Mg-Zn-Ca-Y alloys meet to the nationalstandards. After implantation, the ions of the animals and thefunction of liver and kidney are not obviously abnormal.

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