Deposition and structural formation of 3D alginate tissue scaffolds

Tissue engineering is considered to be one of the most innovative approach for tackling many diseases and body parts that need to be replaced. Biopolymeric scaffolds have been utilized in tissue engineering as a technique to confide the desired proliferation of seeded cells in vitro and in vivo into its architecturally porous three-dimensional structures. Novel freeform fabrication methods for tissue engineering polymeric scaffolds have been an interest because of its repeatability and capability of high accuracy in fabrication resolution at the macro and micro scales.A novel multi-nozzle biopolymer deposition system which is capable of extruding biopolymer solutions and living cells for bioactive fabrication of 3D alginate tissue scaffolds is presented. The deposition process is biocompatible and occurs at room temperature and low pressures to reduce damage to cells. Sodium alginate aqueous solution is deposited into calcium chloride solution using 3DD to form hydrogel structures. Feasibility studies showed that the system is capable of extruding Manugel alginate between 0.4% and 3% (w/v). The flow rate, nozzle diameter, and nozzle velocity were studied and a model was developed to design 3D scaffolds with controlled strut diameters (D = 250 - 410 microns) and pore sizes. In addition, rat heart endothelial cells were deposited through the system with alginate to form gel scaffold structures with encapsulated cells in a bioactive fabricated manor. The study showed that the suitable bioactive parameters preferred 1.5% (w/v) sodium alginate with 0.5% (w/v) calcium chloride. Cell viability studies were conducted on the cell encapsulated scaffolds for validating the bioactive freeform fabrication process that sowed viability up to 85%. The bioactive scaffold supported proliferation up to 21 days of incubation time. The elastic modulus was studied over degradation time that showed that the stiffened during the 24 hours due to crosslinking and degraded then on up to 21 days of incubation at 37 oC.The system showed potential use for accurate cell placement in tissue engineering applications and promote regenerative medicine based on CAD systems.Ph.D., Mechanical Engineering -- Drexel University, 200