Speaker
Description
INTRODUCTION
Articular cartilage has limited regenerative potential and therefore does not restore upon damage. Biofabrication technologies offer promising strategies to engineer functional cartilage constructs to address also large defects [1]. Multicellular spheroids, or microtissues, are widely used as building blocks in these approaches to generate large volumes of cartilage-like matrix [1]. Their spatial arrangement within 3D constructs is important for regulating spheroid fusion, guiding tissue formation, and ensuring instant mechanical integrity of the printed structure. Our aim was to enable rapid and automated production of tissue constructs, facilitating future upscaling. Here, we demonstrate for the first time, the successful convergence between laser-induced forward transfer (LIFT) bioprinting and melt electrowriting (MEW) for the deposition of articular cartilage progenitor cell (ACPC) spheroids into reinforcing meshes.
METHODS
ACPC spheroids (125 cells (Æ~80 µm) and 1000 cells (Æ~150 µm)) were produced, pre-matured for 3 days, and mixed with GelMA prior to LIFT bioprinting (NGB-RTM, Poietis). The effects of laser energy (6-15 µJ), spheroid size, and concentration (80,000 - 160,000 spheroids/mL) on printing accuracy and spheroid deposition rate were studied. Post-LIFT viability and morphology were assessed (Day 1, 7, live/dead assay). To evaluate the feasibility of converging LIFT and MEW technologies, ACPC spheroids were deposited into PCL MEW meshes (internal box-size = 400x400 µm). Mesh coverage and printing accuracy were evaluated post-printing, and spheroid-viability was assessed. Furthermore, a LIFT adaptation and an AI-based imaging system, “target-and-shoot”, was used to automate spheroid recognition and control transfer.
RESULTS
Increasing laser energies increased deposition rates, but resulted in decreased printing accuracy and spheroid viability, particularly for the small spheroids. Lower laser energy improved printing accuracy, but resulted in low deposition rates (<10%). Printing at 12 μJ with higher concentrations resulted in adequate printing accuracy and good cell viability (>80%). Converged bioprinting was achieved with deposition rates similar to previous (non-converged) experiments and maintained spheroid viability. The implementation of a “target-and-shoot” system enabled image-guided spheroid selection and transfer to predefined locations within the MEW meshes, significantly improving transfer efficiency and precision.
DISCUSSION
This study presents a novel approach for engineering larger cartilage constructs through integration of LIFT and MEW technologies. Different sizes of ACPC spheroids with high cell viability and uniformity in size and shape were successfully generated. LIFT parameters, including laser energy, spheroid size and concentration, were optimized to ensure printing fidelity while minimizing cellular damage. Furthermore, we introduced into our printing workflow an AI-based automated detection system that enhances spatial control by selecting the spheroid and directing it to a pre-determined location of a MEW scaffold.
REFERENCES
[1] Burdis R, Kelly DJ. Biomaterials 2022
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