Engineering scaffolds for restorative tissue repair of tendon via polycaprolactone microfiber and polycaprolactone membrane
Date of Issue2012
School of Mechanical and Aerospace Engineering
In tendon repair surgeries, intra-operative graft replacement and post-operative adhesion prevention are two significant but challenging issues hindering the success of the therapies. Conventional practices involve the use of degradable natural materials (e.g. collagen and hyaluronic acid) or non-degradable synthetic materials (e.g. polyethylene terephthalate and polytetrafluoroethylene). However, these materials either mismatch the required mechanical strength or lack a preferred degradability in the body. Emerging medical solutions involve the use of scaffolds or degradable synthetic materials, which can demonstrate both required strength and desired biodegradability and serve a dual function. In this doctoral thesis, the two issues in tendon repair mentioned above will be addressed using this emerging approach. The issue of tendon graft is addressed by using a three dimensionally aligned polycaprolactone microfiber bundle, in which the fiber diameter is as low as 10 µm, largely resembling the collagen fibers found in native tendon tissues. An original and novel method, named microfiber melt drawing, has been developed to enable the fabrication of these microfibers. A mathematical model has been developed to understand this method and help optimize the fabrication process. Characterization experiments show that these microfibers have a fiber diameter of about 10 µm and are highly aligned in three dimensions. Mechanical testing shows that the ultimate tensile strength for a single microfiber bundle is 6.8 ± 1.84 N and that the breaking force of a microfiber bundle can be adjusted by the number of microfibers and tailored for different tendons. In vitro study shows that the microfibers are able to support the growth of fibroblasts over 7 days and align cells along the channels formed between them. In vivo study in a rabbit model shows that the microfiber bundle can be thoroughly infiltrated when implanted in the defect of the Achilles tendon, forming a tendon-like substance in as early as one month. This promising result suggests that microfiber bundle repair may be a better option than the existing therapies.