成功的组织工程骨是支架材料、种子细胞与细胞因子三者的有机结合。本研究从基因修饰干细胞、纳米改良支架以及组织工程骨构建三方面对组织工程骨进行全面改良。首次利用超顺磁性氧化铁纳米颗粒（SPIO）同时作为基因递送载体和MRI造影剂，介导BMP2基因转染牙髓干细胞（DPSCs）实现基因传递和磁性标记的双重功能，使种子细胞长期稳定表达BMP2且MRI可检测。其次，以SPIO改良磷酸钙骨水泥（CPC）赋予其超顺磁性和更加接近细胞外基质形貌的微纳米结构，提高其物理机械性能，并促进种子细胞的黏附、增殖和分化，独特的磁力作用还可吸附磁性标记后的种子细胞而实现磁性靶向。最后，用基因修饰的DPSCs与纳米CPC复合构建组织工程骨，检测其骨修复能力并用MRI无创性在体追踪植入的DPSCs，探索组织工程骨复合体对骨修复的作用机理。这将为组织工程骨的构建、表征，以及植入细胞的无创性实时监测提供新思路。

Successful tissue engineered bones should be designed to include a combination of scaffolds, stem cells and cytokines. In this study, scaffolds and stem cells will be improved and modified by superparamagnetic iron oxides nanoparticles (SPIO) before constructing tissue engineered bone. It is the first time to use of SPIO as both gene delivery system and MRI contrast agent. Dental pulp stem cells (DPSCs) will be gene transfected with bone morphogenetic protein 2 (BMP2) and magnetic marked at the same time by the application of SPIO. The gene modified DPSCs can express BMP2 stably for a long time, while they can be detected by magnetic resonance imaging (MRI). Secondly, calcium phosphate cement (CPC) will be improved by SPIO addition. The modification can endow CPC superparamagnetic properties and micro-nano-structure which is more similar to the morphology of extracellular matrix, so as to achieve enhanced physical and mechanical properties, and better cell adhesion, proliferation and differentiation behaviors. Additionally, the magnetic scaffolds can be the targets of magnetic marked cells. Finally, tissue engineered bone will be constructed with gene-modified DPSCs and nano CPC. Bone regeneration effects will be detected and DPSCs will be tracked noninvasively by MRI. The mechanisms of tissue engineered bone construct on bone repair will be explored. This will give new ideas on real time in vivo tracking of seed cells, and provide new inspiration for the construction and characterization of tissue engineered bones.