Study on composite hydrogel mixture of calcium alginate/gelatin/kappa carrageenan for 3D bioprinting

Regenerative medicine and tissue engineering are continuously advancing and utilizing new technologies to provide reliable solutions for replacing damaged tissues. Unlike subtractive manufacturing, additive manufacturing became an answer for creating complex shapes for many fields, such as tissue engineering, which requires the need to create body parts that are not geometrically simple. Three-dimensional (3D) bioprinting technology is a great additive manufacturing tool that will significantly benefit the field of regenerative medicine and tissue engineering once precision and feasibility are achieved. Printing a 3D structure narrows the range of material choices to meet the biomaterials criteria, including biocompatibility, biodegradability, printability, and low cytotoxicity. Hydrogels meet all requirements for biomaterials; however, they have weak mechanical properties that are hard to control, making it challenging to print a scaffold precisely, restricting their chance of being used as a potential reliable 3D bioprinting material. In this paper, composite scaffolds composed of calcium alginate/gelatin/κ-carrageenan are printed using an extrusion-based 3D bioprinter. Different concentrations of all three hydrogels are prepared and crosslinked with calcium chloride to transform it from sodium alginate/gelatin/κ-carrageenan to calcium alginate/gelatin/κ-carrageenan, then tested for their strength in tension. Printability is also tested for different concentrations to find the best printing parameters in terms of pressure, print speed, layer height, and printing temperature. The composite hydrogel mixture composed of 2.2% (w/v) calcium alginate/1% (w/v) gelatin/4% (w/v) κ-carrageenan exhibited a higher modulus of elasticity compared to the other tested concentrations and is printable using a 0.864 mm nozzle diameter, 62 °C printing temperature, and 48.2 kPa printing pressure.