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

Fabrication of Tubular Nanofibrous Scaffolds Via Thermally Induced Phase Separation and Their Biological Evaluation for Vascular Tissue Engineering

Author HuJinWei
Tutor HeChuangLong
School Donghua University
Course Biochemistry and Molecular Biology
Keywords PLLA PLCL phase separation vascular scaffold tissue engineering
CLC R318.08
Type Master's thesis
Year 2013
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Tubular nanofibrous poly(L-lactic acid)(PLLA) scaffold, which fabricated through a combination of thermally induced phase separation (TIPS) and sugar-leaching techniques, has been proposed as a potential scaffold for blood vessel regeneration. However, PLLA is a rigid polymer that is unable to provide intrinsic viscoelasticity for vascular graft, which is of utmost importance for its long-term patency and overall biological performance. Blends of PLLA with more flexible biocompatible polymers have been demonstrated to improve certain mechanical properties of PLLA. In this study, we fabricated the tubular nanofibrous scaffolds of PLLA and poly(ε-caprolactone)(PCL) or PLLA and poly(L-lactide-co-ε-caprolactone)(PLCL,50:50) blends with varying weight ratios by using TIPS technique. Then, heparin was cross-linked on the surface of tubular scaffold to resist thrombosis. We also evaluated the biocompatibility of the resulting scaffolds by respectively seeding pig iliac artery endothelial cell (PIECs) and human vascular smooth muscle cells (HVSCs) on the scaffolds. The main contents are as follows:1. PLLA/PCL and PLLA/PLCL nanofibrous tubular scaffolds were fabricated using a TIPS technique. The results indicated that the obtained tubular scaffold of PLLA/PCL possessed porous nanofibrous structure, and the pore size and porosity of scaffolds increased with the increased ratio of PCL. Since PLLA and PCL is incompatible polymer, the phase separation of PLLA and solvent can be explained as spinodal decomposition mechanism when the polymer solution phase separated under-80℃, resulting in composite scaffolds with a nanofibrous structure, whereas PCL component was in a metastable region, the phase separation can be produced in a manner of nucleation-growth transition. Thus, the PCL component formed microparticles and distributed in PLLA nanofibrous structure, resulting in nanofibrous scaffolds with sea-island structure. However, PLLA and PLCL are compatible materials when phase separation occured, whose mechanism of phase separation is spinodal decomposition. So the blending of PLLA/PLCL tends to form a uniform nanofibrous structure, which favored to increase their tensile mechanical properties.2. In order to prevent thrombosis in vivo, we chose heparin as anticoagulant drug. Heparin was cross-linked on the surface of scaffold by EDC cross-linking agent and the content was3.0±0.13μg/cm2by toluidine blue staining test. In addition, the protein adsorption ability on the heparinized scaffold reduced, thus improved thier anticoagulant ability. 3. PIECs and HVSMCs were cultured respectively on the surface of the scaffolds to evaluate the biocompatibility of scaffolds. The results showed that PIECs and HVSMCs grown on the scaffolds exhibited a regular morphology. Cells could grow, proliferate on the scaffold and maintain the phenotype. Therefore, the heparinized PLLA/PLCL nanofibrous vascular scaffold has the potential for vacular tissue engineering applications.

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