Abstract
Three-dimensional (3D) bioprinting is driving major innovations in the area of cartilage tissue engineering. Extrusion-based 3D bioprinting necessitates a phase change from a liquid bioink to a semi-solid crosslinked network achieved by a photo-initiated free radical polymerization reaction that is known to be cytotoxic. Therefore, the choice of the photocuring conditions has to be carefully addressed to generate a structure stiff enough to withstand the forces phisiologically applied on articular cartilage, while ensuring adequate cell survival for functional chondral repair. We recently developed a handheld 3D printer called “Biopen”. To progress towards translating this freeform biofabrication tool into clinical practice, we aimed to define the ideal bioprinting conditions that would deliver a scaffold with high cell viability and structural stiffness relevant for chondral repair. To fulfill those criteria, free radical cytotoxicity was confined by a co-axial Core/Shell separation. This system allowed the generation of Core/Shell GelMa/HAMa bioscaffolds with stiffness of 200KPa, achieved after only 10 seconds of exposure to 700 mW/cm2 of 365 nm UV-A, containing >90% viable stem cells that retained proliferative capacity. Overall, the Core/Shell handheld 3D bioprinting strategy enabled rapid generation of high modulus bioscaffolds with high cell viability, with potential for in situ surgical cartilage engineering.
Highlights
Three-dimensional (3D) bioprinting is driving major innovations in the area of cartilage tissue engineering
The modulus of GelMa/HAMa in which the Adipose-derived Mesenchymal Stem/Stromal Cells (ADSCs)-derived chondrogenic cells are to be delivered to the osteochondral lesion via the Biopen needs to be sufficient to withstand compressive forces within the joint so as to sufficiently protect chondrocyte development in situ and prevent the collapse of the implanted scaffold
Our Biopen device was designed to print stem cells in 3D constructs directly into damaged cartilage during surgery in situ. To translate this freeform biofabrication tool into the clinical setting, in this work we aimed to define a bioprinting process that delivered a cell-laden structure with adequate structural integrity to support viable cell delivery to the highly compressive osteochondral lesion environment
Summary
Three-dimensional (3D) bioprinting is driving major innovations in the area of cartilage tissue engineering. To progress towards translating this freeform biofabrication tool into clinical practice, we aimed to define the ideal bioprinting conditions that would deliver a scaffold with high cell viability and structural stiffness relevant for chondral repair To fulfill those criteria, free radical cytotoxicity was confined by a co-axial Core/Shell separation. Crosslinking can be achieved by physical crosslinking (reversible), chemical crosslinking (irreversible) or a combination of both[12] and promotes a robust state change of hydrogels from (viscous) liquid to semi-solid This provides otherwise-absent structural stability in 3D hydrogel material configurations that retain native cell adhesion properties and otherwise mimic extracellular matrix. The major challenge facing chemical photo-cross-linking of cell-containing hydrogels is compromised cell viability due to cytotoxic by-products generated in-process by the cross-linking chemistry[17]
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