Tendons are responsible for transmitting mechanical forces between muscles and bones, enabling body movement. Tendon injuries result in substantial morbidity, pain and disability, affecting athletes, active working people, and elder population. Tissue engineering efforts have been focused on mimicking tendon architecture and functionality by utilizing biomimetic materials. One of the technologies enabling engineering such biomimetic constructs is textile platforms . Therefore, the present study aims at developing cell-laden hybrid hydrogel fibers reinforced with a mechanically robust core fiber made from a biodegradable polymer and assembling them using textile technologies to fabricate constructs replicating tendon mechanical properties and architecture. Commercially available suture was coated with a cell-hydrogel mixture composed of methacryloyl gelatin (GelMA) and alginate. A two step process was used for the production of composite fibers (CFs) consisting of a first crosslinking of alginate in a calcium chloride bath and a second crosslikning step of GelMA by exposure to UV light. The biological performance of CFs was assessed using encapsulated cells (e.g., mesenchymal stem cells (MSCs) or MC-3T3 fibroblasts) to explore the potential of these cell-hydrogel matrices as artificial grafts for tendon tissue engineering applications. Cells were homogeneously distributed along the hydrogel layer, being viable up to 14 days in culture, as determined by live/dead staining and presto blue assay of metabolic activity. In addition, generated CFs were further assembled using braiding technique to enhance their tensile strength. The mechanical properties of single fibers and braided constructs were evaluated. Braiding CFs together allowed tuning the mechanical properties of the constructs to match those of native tendons. Furthermore, the presence of the hydrogel layer modified the extension properties of the material under tensile strength.
In conclusion, reinforced fibers can be used for braiding fibrous tissue-like constructs with tunable mechanical properties. Moreover, cellular behavior can be directed by modifying the composition of the hydrogel layer or by further incorporating bioactive cues like growth factors or adhesion peptides. We have also confirmed the matrix deposition and the expression of tendon-related genes, as well as the suturability of the constructs.
 Akbari, M.; Tamayol, A.; Laforte, V.; Annabi, N.; Najafabadi, A. H.; Khademhosseini, A.; Junker, D., Adv. Funct. Mater. 2014, 24, 4060-4067
The authors would like to thank Portuguese funds through FCT – Fundação para a Ciência e a Tecnologia in the framework of FCT-POPH-FSE, the PhD grant SFRH/BD/96593/2013 of R.C-A.