The Enderstruder: An accessible open-source syringe extruder compatible with Ender series 3D printers Domenic J. Cordova1,B.S., Angel A. Rodriguez1,2, Sabrina C. Woodward1, Cody O. Crosby*1,3, Ph.D. 1 Department of Physics, Southwestern University, Georgetown, TX, United States 2 Department of Mathematics, Southwestern University, Georgetown, TX, United States 3 Department of Biomedical Engineering, The University of Texas at Austin, Austin, TX, United States Bioprinting has enabled the precise spatiotemporal deposition of cell-containing bioinks, opening new avenues of research in tissue engineering and regenerative medicine. Although several open-source extruder designs have been published and adopted by end users, only one extruder has been specifically adapted for the affordable open-source Ender series, a line of machines that are affordable, open-source, and available internationally. Here, we introduce the Enderstruder, a cost-effective extruder attachment that uses a standard 10 mL BD syringe, positions the stepper motor at the level of the gantry, enhances x-axis stability with a linear rail, and uses the originally included stepper motor, resulting in reduced cost and simplified assembly. Furthermore, we present a rigorous iterative process to fine-tune printing profiles for high-viscosity biomaterial inks. To facilitate the implementation of our work by other groups, we provide fully editable Cura profiles for five commonly used biomaterials. To validate and characterize our design, we employ the Enderstruder to print established calibration patterns and complex shapes using each of these five materials. By presenting the Enderstruder and its iterative development process, this study contributes to the growing repository of open-source bioprinting solutions, fostering greater accessibility and affordability for researchers in tissue engineering and beyond.