The Design And Property Research Of A Scaffold For Tendon Tissue Engineering

Injures to tendons are very common in the physically active population. However, some limitations exist in the present therapies. The tissue engineering keeps the promise for tendon repair. Using the tissue engineering for tendon repair is as follows: combined the expanded cells and a biodegradable scaffold to form a composite, and cells proliferate, differentiate and produce the extracellular matrices to form a new tissue after grafting it in the injury position. The scaffold plays a key role in tissue engineering. It not only plays a support role to keep the original tissue shape, but also plays a template role to provide a place for cell attachment, growth, proliferation and differentiation. The scaffold which can conduct the tissue regeneration and control the structure of the tissue is a key factor to determine whether the tissue engineering can be used in clinical treatment or not. The present scaffold for tendon tissue engineering possessed the good biocompatibility, and cells could attach, proliferate and produce extracellular matrices. However, those scaffolds could not meet the mechanical requirements during degradation. This paper designed and prepared a novel scaffold for tendon tissue engineering. It not only could provide a place for cell attachment, proliferation and producing extracellular matrices, but also could meet the mechanical requirements during degradation.This paper designed a novel scaffold for the tendon tissue engineering according to the design principles of tissue engineering scaffolds. The scaffold composed of polyglycolide (PGA) and polylactide (PLA) fibers possessed a "core-sheath" structure. The "core" provided a place for cell attachment and proliferation, and the "sheath" was a scaffold reinforcement, which provided sufficient strength before tissue formation. The "core" was composed of PGA fibers, and the "sheath" was a small-diameter circular plain knitted fabric which is made from PGA/PLA braided yarns.This paper studied the basic properties, performance during degradation in vitro, and cell-fiber reaction of PGA and PLA fiber. The results showed that both PGA and PLA fiber possessed the good mechanical properties, and could be used in textile technologies. The PGA fiber degraded faster than PLA fiber. It lost almost all the mass after 8-week degradation, but lost almost all the tensile strength after 2-week degradation. The morphology changed obviously during degradation. The crystallinity increased firstly and then decreased with the degradation time, which indicated the degradation occurred in the amorphous region. However, the PLA fiber changed not obviously during degradation. Cells attached on PGA fibers much better than on PLA fibers, and cells on PGA fibers produced more matrix. Drawing multiple, drawing temperature and inherent viscosity of polymer had the influence on the performance of PGA fiber during degradation. The PGA fiber produced on higher drawing multiple degraded more slowly. The PGA fiber produced on higher drawing temperature degraded faster. The PGA fiber made from higher inherent viscosity polymer degraded more slowly.This paper studied the preparation of the braided yarns used in the reinforcement of scaffold for tendon tissue engineering, discussed the influence of braiding process on the performance of PGA fiber during degradation, and studied the influence of proportion of PGA and PLA fiber on the performance of braided yarns during degradation. The results showed that PGA fiber and PGA braided yarn had the same trend during degradation, and the degradation could be divided into three stages named as strength decrease stage, mass loss of amorphous region stage and mass loss of crystallinity region stage. In first stage, the strength remaining of fiber in braided yarn was higher than unbraided fiber, and the crystallinity decreased more obviously. In second stage, the mass loss rate of unbraided fiber was higher than fiber in braided yarn, and the crystallinity increased faster. In third stage, the crystallinity of unbraided fiber was nearly same as braided yarn, but the mass loss rate of braided yarn was faster. The results of the degradation test of 4 kinds of braided yarn with different proportion of PGA and PLA fiber indicated that with increase of PGA fiber component, the degradation rate of braided yarn increased.This paper prepared the reinforcement of scaffold for tendon tissue engineering on the circular and flat knitting machine respectively, and discussed the influence of knitting parameters on the geometric shape and mechanical property of the reinforcement. In the process of preparation of the reinforcement on the circular knitting machine, sinking depth, drawing force and feeding tension had the influence on the geometric shape and mechanical property. The fabric prepared on smaller sinking depth, smaller drawing force and larger feeding tension, possessed the smaller stitch length, the regular stitch shape, the closer structure and higher strength. By contraries, the fabric prepared on larger sinking depth, larger drawing force and smaller feeding tension possessed the larger stitch length; the more loosen structure and lower strength. In the process of preparation of the reinforcement on the flat knitting machine, the influence of sinking depth, drawing force and feeding tension on the geometric shape and mechanical property was the same as on the circular knitting machine. The diameter of the reinforcement could be controlled by changing the number of knitting needles on the flat knitting machine, which was suitable for preparation of the reinforcement that had specific geometric requirement.This paper studied the performance during degradation in vitro and cell attachment of the reinforcement of scaffold for tendon tissue engineering, and set up a geometric model of a small-diameter circular plain knitted fabric. The influence of proportion of PGA and PLA fiber on the performance during degradation in vitro and cell attachment was studied. The results showed that with the increase of the PGA fiber component, the degradation rate of the reinforcement of scaffold increase, and cells attached on the reinforcement better. A geometric model of a small-diameter circular plain knitted fabric was set up to analyze the geometric shape of the stitch. The geometric characteristics under extreme condition for both transverse and longitudinal extension were given. The formula for calculating surface porosity was developed.This paper prepared an integrated scaffold for tendon tissue engineering, and studied its properties. The results showed that the scaffold for tendon tissue engineering with a "core-sheath" structure possessed reasonable geometric shape, high porousity and excellent mechanical performance. The degradation could be divided into three stages. The main characteristic of the first stage was the sharp decrease of strength, which could be named as "strength decrease stage". The main characteristic of the second stage was the sharp increase of mass loss, which could be named as "mass loss stage". The mass loss and strength were stable in third stage which could be named as "quasi-stable stage".This paper constructed a tissue engineered tendon by cell-seeding on the scaffold, and evaluated the feasibility of clinical application of the scaffold. The maximum tensile load of the cell-scaffold was 63N. The surface of the cell-scaffold was smooth, and the reinforcement and PGA fibers combined closely. The geometric shape of the cell-scaffold changed obviously during construction. The diameter became smaller, and the length became longer. Cells attached well both on the reinforcement and PGA fibers, and produced a lot of extracellular matrices. The tissue constructed using the scaffold for tendon tissue engineering with a "core-sheath" structure, possessed the close structure, the arrangement of the collagen along the mechanical axis direction, and the similar proportion of cell/ collagen with a normal tendon. The scaffold was feasible for the clinical application.