Investigation and Characterization of Cell Aggregation During and After Inkjet-Based Bioprinting of Cell-Laden Bioink

Abstract

Recently, 3D bioprinting techniques have been broadly recognized as a promising tool to fabricate functional tissues and organs. The bioink used for 3D bioprinting consists of biological materials and cells. Because of the dominant gravitational force, the suspended cells in the bioink sediment resulting in the accumulation and aggregation of cells. This study primarily focuses on the quantification of cell sedimentation-induced cell aggregation during and after inkjet-based bioprinting. The major conclusions are summarized as follows: (1) as the printing time increases from 0 min to 60 min, the percentage of the cells forming cell aggregates at the bottom of the bioink reservoir increases significantly from 3.6% to 54.5%, indicating a severe cell aggregation challenge in 3D bioprinting, (2) during inkjet-based bioprinting, at the printing time of only 15 min, more than 80% of the cells within the nozzle have formed cell aggregates. Both the individual cells and cell aggregates tend to migrate to the vicinity of the nozzle centerline mainly due to the weak shear-thinning properties of the bioink, and (3) after the bioprinting process, the mean cell number per microsphere increases significantly from 0.38 to 1.05 as printing time increases from 0 min to 15 min. The maximum number of cells encapsulated within one microsphere is ten, and 29.8% of the microspheres with cells encapsulated have contained small or large cell aggregates at the printing time of 15 min.