Improving the Mechanical Properties of Wire-Rope Silk Scaffold by Artificial Neural Network in Tendon and Ligament Tissue Engineering

Finding an appropriate model to assess and evaluate mechanical properties in tissue engineered scaffolds is a challenging issue. In this research, a structurally based model was applied to analyze the mechanics of engineered tendon and ligament. Major attempts were made to find the optimum mechanical properties of silk wire-rope scaffold by using the back propagation artificial neural network (ANN) method. Different samples of wire-rope scaffolds were fabricated according to Taguchi experimental design. The number of filaments and twist in each layer of the four layered wire-rope silk yarn were considered as the input parameters in the model. The output parameters included the mechanical properties which consisted of UTS, elongation at break, and stiffness. Finally, sensitivity analysis on input data showed that the number of filaments and the number of twists in the fourth layer are less important than other input parameters. INTRODUCTION Damages to tendon and ligament are among the most frequent injuries, specifically in the young and physically active population. These damages result in the lost job and income, great pain, large health care costs and medical expenses, incomplete healing, and recurrent injuries [1]. Ligaments connect bones to each other in order to restrict their relative motions and tendons link muscles to bones and they are soft and elastic connective tissues composed of dense bundles of collagen fibers. Both of these tissues have similar compositions and hierarchical structures that contribute to motion. They are comprised of cell parts with fibroblasts particularly as its major component and ECM component [2]. Tendons and ligaments are extremely strong in resisting against tensile loads due to the unique hierarchical structure of fiber bundles with the long main axis of tissues. This structure is known as a crimp pattern and causes some especial mechanical properties like viscoelastic and non-linear behavior [3]. Repairing these tissues is generally regarded as the formation of a tissue that has adequate physical and mechanical properties to restore function, but may not have the exact structure of the original tissue. Therefore, the natural healing of these injuries is insufficient since many tendons and ligaments possess a limited capacity to regenerate [4]. Tissue engineering merges the fields of engineering, materials science, cell biology and surgery to fabricate new functional tissue using living cells and a matrix or scaffold. It is concerned with the creation of biological substitutes designed to maintain, restore, or improve the function of damaged tissues and organs [5]. Besides remodeling of the cell, designing 3D scaffold construction is one of the key components in tissue engineering that should provide minimum requirements for biomechanical as well as chemical and physical properties [6]. An ideal scaffold should be designed successfully to match the complex and demanding mechanical requirements of a native human tissue in tissue regeneration that is an essential element for providing temporary and proper mechanical properties and support [7]. Therefore mechanical behavior in tissue engineering is more important for some engineered tissues like tendon and ligament during the healing process [8]. Recently, due to their porous structures, good biocompatibility and excellent mechanical properties, some fabrication textile techniques and structures have been used to design different tendon and ligament scaffolds. This is because of the similar mechanical properties of textile structures with tendons and ligaments such as having the same viscoelastic and Non-linear behaviors [9]. That is why textile-based scaffolds like braided, woven or knitted structures have been widely used for tendon and ligament tissue engineering in the last decade