Improving Uniformity of Cell Distribution in Post-Inkjet-Based Bioprinting

Advancements in additive manufacturing enable the fabrication of in vitro biomimetic grafts leveraging biological materials and cells for various biomedical applications. The realization of such biofabrication typically requires time from minutes to hours depending on the scale and complexity of the models. During direct biofabrication, cell sedimentation with the resultant aggregation is extensively deemed to be one of the acute problems for precise and reliable inkjet-based bioprinting. It often results in highly unstable droplet formation, nozzle clogging, and non-uniformity of post-printing cell distribution. Our previous study has implemented active bioink circulation to mitigate cell sedimentation and aggregation within the bioink reservoir. This study focuses on the comparison of post-printing cell distribution within formed microspheres and one-layer sheets with and without active circulation. The experimental results have demonstrated a significant improvement in post-printing cell distribution under implemented active circulation. Moreover, the printed sheet samples are subject to three-day incubation to investigate the effect of cell distribution on cell viability and proliferation. It shows that compared to non-uniform cell distribution, the uniform cell distribution significantly improves cell viability (92% versus 77% at Day 3) and cell proliferation (3.3 times versus 1.7 times at Day 3). The preliminary results in this paper have demonstrated not only the high effectiveness of the active bioink circulation to improve post-printing cell distribution within microspheres and one-layer sheets, but also the critical role of the uniform post-printing cell distribution in promoting cell viability and proliferation.