Calculation of Mass Transfer and Cell-Specific Consumption Rates to Improve Cell Viability in Bioink Tissue Constructs

Abstract

Biofabrication methods such as extrusion-based bioprinting allow the manufacture of cell-laden structures for cell therapy, but it is important to provide a sufficient number of embedded cells for the replacement of lost functional tissues. To address this issue, we investigated mass transfer rates across a bioink hydrogel for the essential nutrients glucose and glutamine, their metabolites lactate and ammonia, the electron acceptor oxygen, and the model protein bovine serum albumin. Diffusion coefficients were calculated for these substances at two temperatures. We could confirm that diffusion depends on the molecular volume of the substances if the bioink has a high content of polymers. The analysis of pancreatic 1.1B4 β-cells revealed that the nitrogen source glutamine is a limiting nutrient for homeostasis during cultivation. Taking the consumption rates of 1.1B4 β-cells into account during cultivation, we were able to calculate the cell numbers that can be adequately supplied by the cell culture medium and nutrients in the blood using a model tissue construct. For blood-like conditions, a maximum of ~106 cells·mL−1 was suitable for the cell-laden construct, as a function of the diffused substrate and cell consumption rate for a given geometry. We found that oxygen and glutamine were the limiting nutrients in our model.

Optimized Cell Mixing Facilitates the Reproducible Bioprinting of Constructs with High Cell Viability

“…Besides the complexity of the surrounding material, the supply conditions for the cells have to be appropriate. Mass transfer and cell consumption models can be used to ensure sufficient nutrient supply [15]. Further, more detailed studies of cellular metabolism and functionality over time should be performed.…”

“…Pancreatic 1.1B4 cells were cultured and subcultured in high-glucose DMEM containing 10% v/v FBS, 4 mM glutamine, and 1 mM sodium pyruvate (all from Capricorn Scientific) as previously described [15] in a humified atmosphere containing 5% v/v CO 2 . Subcultivation was carried out at about 80% confluence by trypsinization.…”