Morphological Characterization of a Novel Scaffold for Anterior Cruciate Ligament Tissue Engineering

Abstract

Tissue engineering offers an interesting alternative to current anterior cruciate ligament (ACL) surgeries. Indeed, a tissue-engineered solution could ideally overcome the long-term complications due to actual ACL reconstruction by being gradually replaced by biological tissue. Key requirements concerning the ideal scaffold for ligament tissue engineering are numerous and concern its mechanical properties, biochemical nature, and morphology. This study is aimed at predicting the morphology of a novel scaffold for ligament tissue engineering, based on multilayer braided biodegradable copoly(lactic acid-co-(e-caprolactone)) (PLCL) fibers The process used to create the scaffold is briefly presented, and the degradations of the material before and after the scaffold processing are compared. The process offers varying parameters, such as the number of layers in the scaffold, the pitch length of the braid, and the fibers' diameter. The prediction of the morphology in terms of pore size distribution and pores interconnectivity as a function of these parameters is performed numerically using an original method based on a virtual scaffold. The virtual scaffold geometry and the prediction of pore size distribution are evaluated by comparison with experimental results. The presented process permits creation of a tailorable scaffold for ligament tissue engineering using basic equipment and from minimum amounts of raw material. The virtual scaffold geometry closely mimics the geometry of real scaffolds, and the prediction of the pore size distribution is found to be in good accordance with measurements on real scaffolds. The scaffold offers an interconnected network of pores the sizes of which are adjustable by playing on the process parameters and are able to match the ideal pore size reported for tissue ingrowth. The adjustability of the presented scaffold could permit its application in both classical ACL reconstructions and anatomical double-bundle reconstructions. The precise knowledge of the scaffold morphology using the virtual scaffold will be useful to interpret the activity of cells once it will be seeded into the scaffold. An interesting perspective of the present work is to perform a similar study aiming at predicting the mechanical response of the scaffold according to the same process parameters, by implanting the virtual scaffold into a finite element algorithm.

Hierarchically Structured Electrospun Scaffolds with Chemically Conjugated Growth Factor for Ligament Tissue Engineering

“…Similarly, Bosworth et al reported that tightly wound PCL yarn could be utilized as a substrate for tendon fibroblast adhesion and proliferation 37 . Modifications to traditional PCL have also been investigated as materials for ligament scaffolds, particularly ultra-high molecular weight PCL (UHMWPCL) and PCL with the addition of L-lactic acid (PCLC) with promising results 38,39 . In the current study, a scaffold composed of multiple nanofiber bundles was created to better mimic the hierarchal structure of the collagen in the native ACL on macro, micro, and nano size scales, and provide space for matrix deposition between and around the nanofiber bundles.…”

Virtual testing of advanced composites, cellular materials and biomaterials: A review

“…The authors treated the ACL scaffold as a multi-layered braided structure with explicit modelling of the constituent fibres that make up the structure, as shown in Figure 29. The braided structure provides a network of pores adapted for tissue ingrowth [158]. Accurate model representation is central to replicating the expected mechanical response of a typical ACL scaffold, hence resulting in computer-aided tissue engineering of ACLs.…”

Towards a Tissue-Engineered Ligament: Design and Preliminary Evaluation of a Dedicated Multi-Chamber Tension-Torsion Bioreactor

“…A cell suspension (200,000 cells in 15 µL of culture medium of the same composition as above) was deposited within the periphery of the scaffolds. Due to the pore size gradient offered by the scaffold architecture (see [26]), the cell suspension immediately penetrated the scaffold center and spread along the scaffold. The seeded scaffolds were placed in the incubator for 30min after which small amounts of medium were progressively added.…”

“…The bioreactor presented above aims at culturing novel scaffolds for ligament tissue engineering recently proposed and evaluated in our group [26]. Briefly, the scaffold is made of concentric braided layers of PLCL fibers.…”

“…Some future enhancements will be envisaged starting from the present study. Firstly, numerical studies that we recently reported on the braided scaffold [26,27] will be used to determine the best-suited design for the specific application that we target here. We have indeed observed that, for instance, the pore size distribution of the scaffolds used in the present study may not perfectly prevent the obstruction of external pores after 28 days.…”