Investigation of Cell Concentration Change and Cell Aggregation Due to Cell Sedimentation during Inkjet-Based Bioprinting of Cell-Laden Bioink

Abstract

Recently, even though 3D bioprinting has made it possible to fabricate 3D artificial tissues/organs, it still faces several significant challenges such as cell sedimentation and aggregation. As the essential element of 3D bioprinting, bioink is usually composed of biological materials and living cells. Guided by the initially dominant gravitational force, cells sediment, resulting in the non-uniformity of the bioink and the decrease in the printing reliability. This study primarily focuses on the quantification of cell sedimentation-induced cell concentration change and cell aggregation within the bioink reservoir during inkjet-based bioprinting. The major conclusions are summarized as follows: (1) with 0.5% (w/v) sodium alginate, after around 40-min printing time, almost all the cells have sedimented from the top region. The cell concentration at the bottom is measured to be more than doubled after 60-min printing time. On the contrary, due to the slow cell sedimentation velocity with 1.5% and 3% (w/v) sodium alginate, the uniformity of the bioink is still highly maintained after 60-min printing; and (2) more cell aggregates are observed at the bottom with the printing time, and severe cell aggregation phenomenon has been observed at the bottom using 0.5% (w/v) sodium alginate starting from 40-min printing time. With the highest cell concentration 2 × 106 cells/mL, 60.9% of the cells have formed cell aggregates at 40-min printing time. However, cell aggregation is dramatically suppressed by increasing the polymer concentration.

Tumor-on-a-chip models combined with mini-tissues or organoids for engineering tumor tissues

“…Xu et al investigated the piezoelectric-actuated bioprinting of cell-bearing alginate bioink directly into a crosslinking agent to develop cell-laden microspheres (Fig. 1 C) 32 . However, the current forms of DOD bioprinting are limited by inconsistent droplet volumes and negative effects on cell viability after dispensing at high pressures.…”

“…( C ) Schematic illustration of inkjet bioprinting system containing several components including piezoactuator-attached inkjet nozzle, a waveform generator, a pneumatic controller, a bioink reservoir. Adapted with permission from 32 , copyright MDPI 2022. ( D ) (i) Schematical diagram and (ii) optical images of drop-on-demand bioprinting method.…”

Investigation of Cell Aggregation on the Printing Performance in Inkjet-Based Bioprinting of Cell-Laden Bioink

“…Moreover, cell aggregation was observed using 0.5% (w/v) sodium alginate at 120 min printing time. Recently, Xu et al 45 investigated the effect of cell sedimentation on the cell concentration and cell aggregation within the bioink reservoir. It was reported that only within 40 min of printing time, almost all of the cells within the bioink containing 0.5% (w/v) sodium alginate have sedimented to the bottom, significantly increasing the cell concentration and facilitating cell aggregation.…”