Designing Cost-Effective Open-Source Multihead 3D Bioprinters

Electrohydrodynamic Direct-Writing Micro/Nanofibrous Architectures: Principle, Materials, and Biomedical Applications

Electrohydrodynamic (EHD) direct-writing has recently gained attention as a highly promising additive manufacturing strategy for fabricating intricate micro/nanoscale architectures. This technique is particularly well-suited for mimicking the extracellular matrix (ECM) present in biological tissue, which serves a vital function in facilitating cell colonization, migration, and growth. The integration of EHD direct-writing with other techniques has been employed to enhance the biological performance of scaffolds, and significant advancements have been made in the development of tailored scaffold architectures and constituents to meet the specific requirements of various biomedical applications. Here, a comprehensive overview of EHD direct-writing is provided, including its underlying principles, demonstrated materials systems, and biomedical applications. A brief chronology of EHD direct-writing is provided, along with an examination of the observed phenomena that occur during the printing process. The impact of biomaterial selection and architectural topographic cues on biological performance is also highlighted. Finally, the major limitations associated with EHD direct-writing are discussed.

The Enderstruder: An accessible open-source syringe extruder compatible with Ender series 3D printers

Bioprinting has enabled the precise spatiotemporal deposition of cells and biomaterials, opening new avenues of research in tissue engineering and regenerative medicine. Although several open-source syringe extruder adaptations for bioprinters have been published and adopted by end users, only one has been specifically adapted for the Ender series, an affordable and open-source line of thermoplastic 3D printers. 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 an iterative process to fine-tune printing profiles for high-viscosity biomaterial inks. To facilitate the implementation of our work by other researchers, we provide fully editable Cura profiles for five commonly used biomaterials. Using these five materials to validate and characterize our design, we employ the Enderstruder to print established calibration patterns and complex shapes. 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.

Dynamically crosslinked thermoresponsive granular hydrogels

Granular hydrogels are a promising biomaterial for a wide range of biomedical applications, including tissue regeneration, drug/cell delivery, and 3D printing. These granular hydrogels are created by assembling microgels through the jamming process. However, current methods for interconnecting the microgels often limit their use due to the reliance on postprocessing for crosslinking through photoinitiated reactions or enzymatic catalysis. To address this limitation, we incorporated a thiol-functionalized thermo-responsive polymer into oxidized hyaluronic acid microgel assemblies. The rapid exchange rate of thiol-aldehyde dynamic covalent bonds allows the microgel assembly to be shear-thinning and self-healing, with the phase transition behavior of the thermo-responsive polymer serving as secondary crosslinking to stabilize the granular hydrogels network at body temperature. This two-stage crosslinking system provides excellent injectability and shape stability, while maintaining mechanical integrity. In addition, the aldehyde groups of the microgels act as covalent binding sites for sustained drug release. These granular hydrogels can be used as scaffolds for cell delivery and encapsulation, and can be 3D printed without the need for post-printing processing to maintain mechanical stability. Overall, our work introduces thermo-responsive granular hydrogels with promising potential for various biomedical applications.