Research On The Critical Process For In-vitro Engineering Cardiac Tissue Based On The Assembly Of Fibers

Based on the analysis of the composition and structure of native myocardial tissue,according to the biomimetic design principle and the “bottom-up” strategy in modulartissue engineering, this dissertation presents a novel approach for the fabrication of abunchy cardiac tissue by ordered assembly of hydrogel fibers. In this dissertation, thescientific and technologic issues about the design, forming and application of thebunchy cardiac tissue were studied systematically. Above all, the main work includedthe material and structural design of the bunchy construct. Then the forming process ofhydrogel fibers and the device were developed, on which the principle analysis andparametric study were carried out. The bunchy construct was built and its mechanicalproperties were characterized and evaluated. Applying the self-developed process, aringlike bunchy cardiac tissue and its preliminary biological assessment were obtainedin the end.The main conclusions of this dissertation were as follow:(1) The bunchy cardiactissue was designed to mimic the composition, structure and microenvironment ofnative myocardial tissue. It was fabricated by ordered assembly of hydrogel fiberswhich were made of the “Alginate-Fibrin-Matrigel” biomemitic material system. Witha diameter of150~250μm, the fibers were expected to address the limitation of oxygendiffusion in hydrogel material. The micro channel network was formed directly bytaking advantage of the space among fibers. Through the FLUENT software andtheoretical calculation, the flow field in every micro channel and the transport ofoxygen were analyzed and evaluated. It showed conducive that oxygen-enrichedmicroenvironment throughout the bunchy construct can be achieved.(2) Thewinding-wet-spinning process was developed to produce the alginate-based hydrogelfibers, in which the fibers were formed continuously and stably and then collected inorder around a rotor. The slender fibers and the cell-laden fibers were successivelyproduced. Fibers were used as modules and assembled into various bunchy constructs.(3) The relationship between the forming result and the parameters was deeply studied.According to the experimental results, suitable forming parameters were confirmed.The mechanical properties of the bunchy construct were researched as well, in order to meet the demands for the follow-up in-vitro culture and training.(4) The fabrication,in-vitro culture and stretch training for the ringlike bunchy cardiac tissue wereperformed, as well as the biological assessment. Results showed that the materialsystem owned good biocompatibility with the cells. After the stretch training underculture condition containing calcium, the construct was capable to maintain long andthe oriented alignment and interconnectivity of cardiac myocytes was promoted atsome representative locations, as well as the formation of oriented histomorphology.