可降解锌合金的关键基础科学问题

国内外50余篇文章初步表明：锌合金在体液中降解速度适中，生物相容性良好。但可降解锌合金目前处于成分设计“炒菜”阶段，在体试验研究缺乏，材料与机体交互作用基础科学问题尚不明清。申请人从11种元素中优化出Mg、Ca、Sr和Li（获4项授权发明专利），发现Zn-Li合金抗拉强度>500MPa，降解速度0.02-0.03mm/y，材料100%浸提液培养4天的前成骨细胞相对增殖率130-180%。据此本项目将以Zn为基体，以Li作为力学强化元素，加之以Mg、Ca或Sr作为协同促进成骨的生物功能化元素研发新型骨修复用锌合金，优化成分配比与加工工艺，研究其在动物体内骨环境下的降解行为，阐明其力学行为（拉压强度、蠕变抗力、腐蚀疲劳）和组织稳定性，探明其降解产物对周围骨组织生长和吸收的影响关系，最终揭示可降解锌合金与机体化学、力学和生物学交互作用机制及其合金化设计准则，拓展可降解金属在骨科领域的适应症范畴。

Till now the researchers from 10 countries including the USA and China had published 50 plus papers, preliminarily proved that the zinc alloys could be degraded by body fluid, and exhibited good biocompatibility, and showed scientific phenomena different from biomedical magnesium alloys due to the low melting point of element zinc. The research work on biodegradable zinc alloys is now at the initial stage, focusing on alloying design by "element cooking", and insufficiency on animal testing to better understand the material-host interaction mechanisms. The preliminary study by the applicant on 11 kinds of alloying elements to zinc (Mg, Ca, Sr, Li, Mn, Cu, Ag, Y, Fe, Gd, Dy）indicated that the best alloying elements are Mg, Ca, Sr and Li(4 issued Chinese inventation patents), and the binary Zn-Li alloys exhibited excellent properties, such as ultimate tensile strength over 500MPa, the degradation rate measured by immersion testing in simulated body fluid are between 0.02-0.03 mm/year, the relative cell proliferation rate of MC3T3-E1 Pre-osteoblasts cultured with 100% extract from material at day 4 can reach 130-180%. Based on aforementioned facts, the aim of the present work is to develop new kinds of biodegradable zinc alloys for bone repair, with the zinc as base material, the element Li as mechanical strengthening alloying element, and element Mg, Ca or Sr as bio-functionalized alloying elements, and optimizing the best composition recipe and hot/cold working technology. After that the biodegradable zinc alloys will be implanted into the bone microenvironment with different animal models (rat, rabbit, goat), the in vivo degradation behavior will be studied, the degeneration of the mechanical behavior (tensile and compression strength, creeping resistance, corrosion fatigue resistance) of the biodegradable zinc alloys with implantation time and the stability of the microstructure will be measured, and the influence law of the degradation products of biodegradable zinc alloys on the surrounding host bone tissue, either new bone formation or bone resorption, will be evaluated, and finally the chemical, mechanical and biological interaction mechanisms between biodegradable zinc alloys and the host will be expatiated, and the principle of biomedical zinc alloying design, and it may extend the application of biodegradable metals in the field of orthopedic surgery from the non-load bearing into the load-bearing categories.