Melt-Spun, Cross-Section Modified Polycaprolactone Fibers for Use in Tendon and Ligament Tissue Engineering

Abstract

Tissue Engineering is considered a promising route to address existing deficits of autografts and permanent synthetic prostheses for tendons and ligaments. However, the requirements placed on the scaffold material are manifold and include mechanical, biological and degradation-related aspects. In addition, scalable processes and FDA-approved materials should be applied to ensure the transfer into clinical practice. To accommodate these aspects, this work focuses on the high-scale fabrication of high-strength and highly oriented polycaprolactone (PCL) fibers with adjustable cross-sectional geometry and degradation kinetics applying melt spinning technology. Four different fiber cross-sections were investigated to account for potential functionalization and cell growth guidance. Mechanical properties and crystallinity were studied for a 24-week exposure to phosphate-buffered saline (PBS) at 37 °C. PCL fibers were further processed into scaffolds using multistage circular braiding with three different hierarchical structures. One structure was selected based on its morphology and scaled up in thickness to match the requirements for a human anterior cruciate ligament (ACL) replacement. Applying a broad range of draw ratios (up to DR9.25), high-strength PCL fibers with excellent tensile strength (up to 69 cN/tex) could be readily fabricated. The strength retention after 24 weeks in PBS at 37 °C was 83–93%. The following braiding procedure did not affect the scaffolds’ mechanical properties as long as the number of filaments and the braiding angle remained constant. Up-scaled PCL scaffolds resisted loads of up to 4353.88 ± 37.30 N, whilst matching the stiffness of the human ACL (111–396 N/mm). In conclusion, this work demonstrates the fabrication of highly oriented PCL fibers with excellent mechanical properties. The created fibers represent a promising building block that can be further processed into versatile textile implants for tissue engineering and regenerative medicine.

3D-Braided Poly-ε-Caprolactone-Based Scaffolds for Ligament Tissue Engineering

“…The PCL monofilaments are manufactured at Institut für Textiltechnik of RWTH Aachen University, Germany. PCL-pellets with a molecular weight of 80,000 Da (CAPA 6800 ® , Perstorp Holding AB, Malmö, Sweden) were used for the melt-spinning process described in [ 35 ]. Seven monofilaments were folded per bobbin to achieve the mechanical properties of the ACL in a single braiding step.…”

“…The use of melt-spun PCL fibers in tissue engineering has rarely been reported [ 33 , 34 ]. We have presented promising results on the fabrication of melt-spun PCL fibers with different cross-section geometries for tissue engineering applications [ 35 ]. Similar fibers were used in the present study.…”

“…Our overall approach to the design of functional ACL scaffolds was focused on several parameters: polymer material, scaffold shape, mechanical properties, porosity, and pore size, as well as degradability [ 35 ]. In this paper, the particular focus is on understanding the effects of varying the parameters of 3D-braiding geometry and braiding position on the mechanical properties of the fabricated scaffold.…”

Amination of Polymeric Braid Structures to Improve Tendon Healing: An Experimental Comparison

“…Commonly reported problems include insufficient long‐term mechanical durability and lack of biointegration capacity to enable appropriate biological tissue ingrowth into their structure. [ 5,6 ]…”

“…Commonly reported problems include insufficient long-term mechanical durability and lack of biointegration capacity to enable appropriate biological tissue ingrowth into their structure. [5,6] To address these shortcomings, fibrous textile structures as tissue scaffolds have been popular targets due to their versatility, morphological similarity to the natural extracellular matrix (ECM), and mechanical anisotropy to resemble biological tissues. [7] An innovative medical device produced from hybrid textile braids based on PET and PLA yarns was developed in previous work.…”