In the field of bioprinting, which is growing very rapidly, the bioextrusion technology represents more than 80% of the market. The other technologies (e.g. microvalve or inkjet) are used for their ability to print droplets. Among them, laser-assisted bioprinting (LAB) represents the most advanced technology to achieve high resolution printing and high cell viability . Poietis, a leading company in LAB technology, has developed a unique machine combining all bioprinting technologies in a single instrument to take advantage of their complementary performances paving the way toward personalized ATMPs for therapeutic applications . In this context, bioprinting of spheroids is of great interest to produce efficacious tissue constructs for clinical applications . The objective of this talk is to present the capabilities of the LAB approach to print spheroids in a reproducible manner while ensuring post-printing structural maintenance of spheroids and cell viability.
Spheroid LAB printing is possible by raising the laser energy to 25 µJ, the deposited volume to 30 µL and ablated gold surface to 7000 μm². First, a very thin, high speed jet appeared followed by a thicker jet at lower speed which is capable to transport the spheroid onto the receiver surface. These settings resulted in the formation of a jet with a diameter of 200µm and spheroid transfer success of 94%. The ultra-short laser was limited in the size of spheroid printing capability while the nanosecond laser gave a broader range.
Spheroids with different chondrogenic maturation were tested and day 7 ones exhibit the best printing efficiency possibly due to a trade-off in their composition (# cells, ECM) and size. Semi-quantification of viability staining demonstrated that printing using ultra-fast laser resulted in a similar viability as non-printed spheroids. Although the nanosecond laser resulted in a slightly lower cell viability after printing, the broader range of spheroid printability motivated its use for further experiments.
Furthermore, time resolved imaging technique enabled quantification of the jet dynamics to get experimental behavior laws for each condition. Next, numerical simulations contributed with physical interpretation to the experimental data.
DISCUSSION & CONCLUSION:
We provide proof-of-concept for the use of LAB technology for spheroid-based tissue production, providing a reproducible and precise manner of transferring spheroids. A better understanding of the underlying physical processes and specific biological conditions have been obtained through dedicated experiments and simulations.
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Joint Promise European Project (RIA, N°H2020-SC1-BHC-2018-2020) / BPI / Nouvelle-Aquitaine Council"