Abstract

Bioprinting technologies enable precise delivery of bio-inks for the fabrication of living constructs. An open challenge in the bioprinting field is to fabricate a vascular network. For this, ability to print a wide range of viscosity, micrometric printing resolution, negligible impact on the cell viability, high-speed and multi-scale printing are required. The current research aims to simulate, develop and validate a novel laser induced side transfer (LIST) technique for bioprinting. The method uses low energy nanosecond laser pulses to generate a transient microbubble inside a microcapillary that contains the bio-ink. Microbubble expansion results in the ejection of the bioink perpendicular to the irradiation axis. We presented a hybrid model to simulate the technique. We investigated the dynamics of the laser-induced bubble in confining geometries, to show the self-limiting effect on the growth of the bubble. Understanding the effect of geometry confinement on bubble dynamics is required to optimize existing and engineer future applications.
We developed LIST setup and determined optimal conditions of bioprinting and investigated the functionality of LIST-printed human umbilical vein endothelial cells (HUVECs). Our investigations show that LIST-printed HUVECs present negligible loss of viability and maintain their abilities to migrate, proliferate and form intercellular junctions. We explored the effect of hydrogel-based matrices on the LIST-printed HUVECs. Our investigation showed that printing Fibrinogen/HUVECs droplets on Matrigel/Thrombin-based matrix provided firm adhesion maintaining the initial printing pattern. This matrix also led the HUVECs to form intercellular junctions. We investigated the effects of pro- and anti-angiogenic factors on sprouting in the LIST-printed lines and in the formation of the tube-like structures. In all conditions, the cells were able to partially create the tube-like formation. However, bone morphogenetic protein9 (BMP9) as an anti-angiogenic factor significantly increased the lumen length.
In the present study, we showed that LIST is capable of printing cells with negligible loss in viability (>93.1 %), with micrometric resolution (165 and 325 µm) and with high speed (potentially 2500 Hz) for bioinks with viscosity upto 300 mPa.s. These features make LIST complementary to existing bioprinting approaches and pave the path to fabricate functional tissues/organs for drug screening and tissue regeneration.