Bone Tissue Scaffold Technologies Based on RP Adopted Droplet Assembly
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Bone Tissue Scaffold Technologies Based on RP Adopted Droplet Assembly1 Renji Zhang, Yongnian Yan and Feng Lin Dept. of Mechanical Engineering, Tsinghua University, Beijing 100084, P. R. China 1 Supported by the Hi-Tech Research and Development Program of China, No. 715-009-0160. ABSTRACT Tissue engineering tries to grow replacement tissues to repair damaged bones. In this paper, the fabrication technology of Multi-nozzle Deposition Manufacturing (MDM) was adopted to fabricate scaffolds of a tissue engineered bone at low temperature. The composite of poly(L-lactic acid) and tri-calcium phosphate (TCP) was chosen to form bone tissue engineering scaffolds. The new computer aided manufacturing process can make porous PLLA/TCP scaffolds. A new surface processing technology of apatite coating on bone tissue engineered scaffolds was also adopted. This digital forming technology was based on rapid prototyping (RP), in which a digital droplets assembly technology was introduced. The MDM technology of 4 nozzles was developed based on the layer-by-layer manufacturing principle of Solid Freeform Fabrication (SFF) in our laboratory. The bone scaffolds made by the multi-nozzle deposition process in the MDM system have good biocompatibility and bone conductive properties as a molecular scaffold for bone morphogenic protein (BMP) in the implantation experiment of repairing segment defects in rabbits’ and dogs’ radiuses.
INTRODUCTION Tissue Engineering has been developed and applied widely recently for the ability to provide medical implantations which repair, maintain and promote the function and morphology of injured tissues or organs. As one of the keystrokes of tissue engineering, scaffolds are important for the following functions: directing the growth of cells migrating from surrounding tissue or of cells seeded within the porous scaffold and providing a substrate for cell attachment, proliferation, differentiated function and, in certain cases, cell migration; for an article cartilage/bone transplant, the scaffold must have the proper mechanical properties to support the normal physiological functions. Research on scaffolds has been a hot arena[1-5]. The structure of human bone is built up with multi-phase composites of cells. There are three kinds of main structural elements: cells which constitute functional units, the extra-cellular matrix (ECM) and bone scaffolds. Traditional materials such as metals, ceramics, polymers and composites are always exotic materials in the human body. Implants with these materials could only replace functions partially. Traditional scaffold manufacturing technologies include fiber bonding, solvent casting, particulate leasing, membrane lamination, melt molding and emulsion freeze drying. These can hardly make customized scaffolds for different patients with specially designed functional
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gradient structure including gradient material structure and gradient morphology structure. Those features of bone scaffolds are important for the regeneration of the structural tissue. A
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