3D Hybrid Bioprinting with Composite Material Technology

Introduction:: Bioprinting is an emerging biomedical technology with promising applications in bioengineering, regenerative medicine, and tissue engineering. The technology of 3D bioprinting is a crucial need in addressing musculoskeletal disorders that involve both hard and soft tissues for the growing aging population and approximately 1.71 billion people with musculoskeletal medical conditions worldwide. This study involves implementation of a 3D Hybrid Bioprinter (Hybprinter) technology to address musculoskeletal tissue regeneration including hard and soft tissues as well as hard-soft tissue interfaces by fabrication of 3D orthopedic composite constructs. Despite great progress of bioprinting for musculoskeletal applications, integration of hard and soft multifunctional components in a tissue-like structure is still an ongoing challenge. Here, we discuss the Hybprinter technology which is specifically designed and developed for fabrication of integrated soft and hard tissue engineering constructs. In this study, two bioprinting technologies are combined into a single 3D bioprinter which enables fabrication of hybrid constructs. It is shown that the Hybprinter enables seamless integration and customization of soft and hard components with complex configurations. In this approach, printability of biocompatible hybrid scaffold-hydrogel constructs is investigated, and the printed structures are characterized for musculoskeletal tissue engineering applications.

Materials and Methods:: In the Hybprinter technology, the Fused Deposition Modeling (FDM) is integrated with Stereolithography (SLA) in one 3D bioprinter technology. The FDM module 3D prints biodegradable mechanically robust polymer/ceramic scaffolds with controlled porosity. A specific thermoplastic material is used for FDM printing which is a composite of polycaprolactone (PCL) and β-tricalcium phosphate (β-TCP) to provide a suitable balance between 3D printability, biodegradation, and bone regeneration. Due to the complex and delicate PCL/β-TCP synthesis process a mechatronic system is developed and implemented to produce PCL/β-TCP filaments for 3D bioprinting. The FDM module alone is tested by 3D printing different scaffold structures. The 3D-printed PCL/β-TCP constructs are then optimized through a systematic experimental characterization to achieve the composition, porosity, and mechanical performances required for bone tissue engineering applications. On the other hand, the Hybprinter technology utilizes the digital light processing-based stereolithography (DLP-SLA) for 3D printing of integrated soft hydrogel constructs. The SLA module employs visible light projection in conjunction with the poly-ethylene glycol diacrylate (PEGDA) as the base polymer which is made crosslinkable by lithium phenyl-2,4,6-trimethylbenzoylphosphinate (LAP) photoinitiator. The light penetration is controlled by Tartrazine photo absorber. The effect of light exposure time on physical and mechanical characteristics of hydrogel component is optimized. Then a sample hybrid construct with integrated hard scaffold and soft hydrogel is 3D printed through a sequential combinatory process and mechanical properties of the hybrid construct are characterized.

Results, Conclusions, and Discussions:: In this study the 3D Hybprinter technology is developed to fabricate hybrid composite hard-soft constructs that integrate both solid mechanically robust scaffolds and soft bioactive hydrogels for bone and musculoskeletal tissue regeneration. The FDM technology is utilized for 3D printing the solid mechanically robust part of the hybrid construct using biodegradable PCL/β-TCP material which is synthesized and experimentally characterized. The Young’s modulus of PCL/β-TCP is measured and compared with PCL in Fig1. Moreover, a mechatronic system is developed for PCL/β-TCP filament preparation which exhibits an acceptable accuracy for FDM bioprinting with less than 15% error in filament diameter, as well as, reliable continuous filament production beyond 50 m. On the other hand, the soft part of the hybrid construct is fabricated using DLP-SLA technology where an integrated hydrogel construct is 3D printed. The SLA print parameters and polymer properties are experimentally optimized. Lastly, the performance of the Hybprinter technology is demonstrated by 3D printing a sample construct consisting of 90% hydrogel and 10% solid scaffold. Mechanical properties of the fabricated construct are experimentally characterized and provided in Fig 1. The results show that the compressive mechanical stiffness of the hybrid construct with 90% hydrogel is significantly higher than hydrogel itself. Results obtained from this preliminary study suggest various potential applications of Hybprinter in tissue engineering where the solid scaffold provides mechanical support and the soft hydrogel can be utilized to enhance biological functionality of the construct as a diffusible component to deliver bioagents such as cells, drug, and growth factor.

Acknowledgements (Optional): : This project is partially supported by National Institutes of Health grant R01AR057837, U01AR069395, R01AR072613, R01AR074458, and Department of Defense grant W81XWH-22-1-0189 (YPY).

References (Optional): :

• Shanjani, Y., Pan, C.C., Elomaa, L. and Yang, Y.P. "A novel bioprinting method and system for forming hybrid tissue engineering constructs. Biofabrication, 7 (4): 045008." (2015).


• Bruyas, A., Lou, F., Stahl, A.M., Gardner, M., Maloney, W., Goodman, S. and Yang, Y.P. "Systematic characterization of 3D-printed PCL/β-TCP scaffolds for biomedical devices and bone tissue engineering: Influence of composition and porosity." Journal of materials research 33, no. 14 (2018): 1948-1959.