Study On Low-temperature Deposition Manufacturing Of Vascular Tissue Engineering Scaffold

Cardiovascular disease remains the leading cause of threatening human healthy all over the world, and vessel transplantation is the main clinical treatment for this. Recently, the tissue-engineered vascular graft (TEVG) is considered to be the most potential vascular substitute. Since there is a clinical need for the TEVG, fabricating the vascular scaffold individually appears to be necessary. But the present methods of designing and processing vascular scaffold are too simple and crude to meet this need. In this paper, the rapid prototyping (RP) technology was employed to resolve the problem of fabricating individual scaffold. Vascular scaffold was fabricated utilizing the low-temperature deposition manufacturing (LDM), which is a novel RP technique with the assistance of computer aided design (CAD). Then the morphological characteristics, physical properties and biocompatibility of the scaffold fabricated by this approach were deeply studied.The research status about materials, design and processing methods of vascular scaffold were introduced systematically, as well as the application of RP technology in medical domain. LDM was proposed to develop the traditional tubular scaffold, bifurcated blood vessel scaffold and vascular network scaffold. Based on the theory of vascular anatomy, physiology and hemodynamics, the resistance distribution in the bifurcated blood vessel was analyzed; the optimization design of branch vascular structure was devised with the purpose of minimal energy cost; and the blood flow simulation for branch vascular was carried out by COSMOSFloWorks software. The results of all those works were used to provide direction for CAD modeling.LDM is essentially a forming process that the computer-aided 3D model is transformed into numerical control (NC) information to drive the LDM machine to extrude and deposit the material in low temperature environment. In order to obtain the NC information, CAD software SolidWorks was used to design the 3D models for each scaffold, and stratifying software Aurora was used to stratify the models. Among several designing and stratifying proposals, the contour line scan was proved to be the best way to form the vascular scaffold. Then the tubular scaffold model was improved according to the analysis of scaffold freezing process in low temperature environment. The forming results showed that the scaffolds reproduced the structure of 3D models accurately; all scaffolds had integrated wall, continuous structure and unobstructed lumen.Tubular scaffold was selected as the object to research the impacts of different process parameters on vascular scaffold morphological characteristics (including wall thickness, micropore structure and wall adhesive strength), and physical properties (including porosity, water permeability and mechanical properties). And comparative experiments were carried out for verifying the conclusion above. It was been found that wall thickness was positively correlated with the nozzle temperature, and performed great linear relationship with velocity ratio (screw speed/scanning speed); slurry concentration and temperature parameter affected the micropore structure directly and could change its size; nozzle temperature played a key role to regulate and control the wall modality and adhesive strength. Meanwhile, the scaffold porosity, water permeability and mechanical properties were related with its morphological characteristics, so could be control by all kinds of process parameters. Finally, it was been proved that vascular scaffold fabricated by LDM could meet the needs of vascular tissue engineering, according to the evaluating of scaffold physical properties and biocompatibility.