Fabrication and Characterization of Knitted Silk-Based Composite Scaffold for Bone-Ligament-Bone (B-L-B) Graft

Abstract

The Anterior Cruciate Ligament (ACL) is one of the four major ligaments of the knee. Owing to its central position and key role in load bearing and flexing of the knee, it is known to be one of the most widely injured ligaments of the body. Scientists have been trying to engineer artificial ligaments by using novel scaffolds as a replacement of injured ligaments beyond repair, but have failed in the post-operative recovery stages due to the inability of the ligament-alone graft to satisfactorily integrate with the bone and provide adequate insertional strength. This was found to be due the lack of formation of a specialized fibrocartilaginous tissue known as the ‘enthesis’ at the junction between the bone and the ligament. The current project has focused on the fabrication of a silk-based knitted scaffold which comprises of three compartments, one each for the bone, ligament and enthesis tissues. With a motive to differentiate the MSCs into fibrocartilage lineages in enthesis compartment amidst the mature cell lines, an array of methods were adopted for surface modification of the compartmentalized knitted silk scaffold by using bio-polymers such as silk solution, chitosan, polyvinyl alcohol and hydroxyapatite on the appropriate compartments. The ligament and bone compartments were reserved for mature cell line culture. The various methods used for coatings of polymers over the knitted-silk were alternate soaking, plain coating and freeze-drying. The scaffold was characterized for various parameters such as water absorption, biodegradability, tensile strength, purity of coatings, and biocompatibility. It was concluded that the multi-compartment silk based scaffold developed in house has the novelty for tissue engineering the bridge component between bone and ligament i.e. fibrocartilaginous enthesis.