Advances Toward Forming Synthetic Mimetic Tendon
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Advances Toward Forming Synthetic Mimetic Tendon Dilinazi Aishanjiang1, Emily C. Green1, Heng Li1, and Marilyn L. Minus1 1
Mechanical and Industrial Engineering Department, Northeastern University, Boston, MA
02115, U.S.A ABSTRACT Collagen is the most abundant protein present in the human body and found in connective tissues, bone, and tendon. It is also known as a natural resource for healing damaged skin tissues [1]. In this study, under specific microenvironment conditions, mimetic collagen gels were successfully formed synthetically from reconstituted Bovine type I collagen monomers. This was achieved by controlling ionic strength, temperature and pH, allowing fibrils with native mimetic D periodic banding structure to assemble spontaneously within the gels. In addition, by providing appropriate aging temperatures and times, mature collagen fibril growth is also realized in the gels in vitro. Mimetic gels were subsequently formed into fibers through a wetspinning process. These spun fibers were found to preserve the native mimetic D periodic banding and fibrillar structure formed in the initial gels. As a result, the synthetic fibers resemble native tendon. Here structural development within the gel samples and fibers as a function of processing was analyzed by scanning electron microscopy (SEM). Results in this study also show a potentially new route for the fabrication of synthetic collagen fibers mimicking tendon, which may find applications as engineered tissues or scaffolding materials. INTRODUCTION Native tendon fibers exhibit a multi-scale micro-structure comprised of varying levels of collagen fibril formation starting from the collagen monomer. Native formation of collagen fibers involves several steps: (1) polypeptide α-chains assemble to form the procollagen molecule; (2) procollagen molecule ends cleave to form tropocollagen (3) tropocollagen selfassembles to form collagen fibrils; and (4) collagen fibrils pack to form larger collagen fibers. Collagen fibrils have several important structural features, which arise due to proper assemble from the molecular to macroscopic level. These features include, D periodic banding, tapered ends, fibrillar organization, and various final fiber diameter distributions specific to different native tissue functions. D periodic banding is observed in collagen fibrils due to lateral stacking of the ordered triple helices (tropocollagen). Tapered ends exist mostly within the fibrils of young tendon in order to assist in reinforcement of the extracellular matrix (ECM) and fibril axial growth by tip-to-tip fusion [2, 3]. Fibrillar arrangement and orientation is important for mechanical stability in some native tissues. Research related to synthetic fabrication of collagen fibers is important to the fast growing field of tissue regeneration (e.g., engineering of ECM-like materials). Synthetically engineered ECM materials from collagen sources can be more favorable for use than native counterparts due to the lack of availability of native materials, and due to compatibili
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