Development of tendon derived natural extracellular matrix hydrogels for 3D bioprinting applications

Biomaterials development for 3D bioprinting processes has become one of the major objectives of tissue engineering in recent years, as biomaterials play pivotal role in determining the long term durability and the functionality of printed biological constructs. Hydrogel materials are frequently used in 3D bioprinting either as support structures for providing shape fidelity to printed cell aggregates or cell-encapsulating agents for mimicking the biochemical and biomechanical aspects of extracellular matrix (ECM). Mechanical properties of synthetic and commercially available natural hydrogels can be tuned easily for 3D bioprinting purposes; however, in most cases they fail to represent the natural environment of ECM. In spite of the biochemical wealth of the ECM hydrogels derived from animal or human tissues, they are not the best candidates to be used in 3D bioprinting processes due to the very slow gelation kinetics. This thesis work addresses this problem by describing the production of bovine tendon derived ECM solution by presenting the optimized decellularization and enzymatic digestion procedures. Decellularization conditions were used for the efficient removal of cellular content in order to suppress the immunogenic potential of the native tissue. Furthermore, morphological and structural studies showed that the natural architecture of the ECM was also preserved. Based on the rheological studies, the prepared ECM solution was observed to form stable hydrogel in about three minutes under physiological conditions. Besides, biocompatibility of developed ECM hydrogels was verified on encapsulated NIH 3T3 fibroblast cells. Normal fibroblast morphology was observed in ECM hydrogels indicating their high biomimicry. Additionally, 3D printing of ECM hydrogels by using a custom built 3D printer proved their high printability. The results showed that the developed naturally derived ECM hydrogel possesses fast gelation kinetics which makes it a promising candidate for 3D bioprinting practices, and as an alternative injectable hydrogel for augmented treatment of tendon injuries. Moreover, this is the first report on 3D bioprinting of naturally derived ECM hydrogels by employing a piston driven extrusion based deposition system, without using any additional crosslinking agents or support polymer structures