UCLA

There stands considerable opportunity in the medical field for the rapidly expanding scope of additive manufacturing technology such as 3D bioprinting, as the capacity for fabricating patient-unique tissue engineered scaffolds in a rapid, direct manner may expand the availability and applicability of surgical techniques. In this work, a 3D bioprinting technique was used to fabricate tubularized constructs for the urethral tissue regeneration. In particular, an elastic hydrogel-based biomaterials were optimized to be used as bioinks for 3D bioprinting of a construct for urethral reconstruction. Two radially distinct regions were determined to be necessary for this tissue-engineered construct, to provide cellular proliferation and structural support to the graft while de-facto partitioning two distinctive tissue regions in the urethra, one made of gelatin methacryloyl (GelMA) for the urothelium, and another layer made of methacrylated elastin-like polypeptide (mELP) and GelMA for smooth muscle cells (SMCs). GelMA and mELP were selected for the hydrogel blend to ensure mechanical durability while attaining a greater extensibility desirable for the urethral tissue region. Chemical characterization via H-NMR analysis provided evidence of the photocrosslinking mechanism which was utilized to crosslink the bioink and solidify the construct with the degree of crosslinking as 55% for GelMA and 68% for mELP/GelMA. Mechanical characterization allowed us to select an optimal ratio of GelMA/mELP and achieve the mechanical properties close to native urethra. Following this stage, the optimization of printing parameters for each bioinks yielded for temperature 30 and 8 �C, printing speed of 8 mm/s and 5 mm/s, and extrusion pressure 4 psi and 15 psi for the 10% (w/v) GelMA bioink and 15% (w/v) 1:1 mELP/GelMA bioink, respectively. Future studies will focus on in vitro cellular studies to ascertain the cytocompatibility of this material, as well as quantify the construct’s efficacy in future applications surgically.