Page 287 - IJB-10-3

International Journal of Bioprinting Design and optimization of 3DP bioscaffolds

analyze and simulate light-cured 3D-bioprinted scaffolds • The entire system is assumed to contain sufficient
under dynamic in vitro cultivation conditions. The model nutrients, considering only oxygen as the sole
was validated by comparing the predicted results with substrate for cell metabolism and growth.
those observed in experiments of C2C12 cell culture, • Oxygen molecules are considered to be uniformly
demonstrating high capability in modeling cell growth dissolved in the nutrient solution at a specific
behaviors. Utilizing this multi-physics model, parametric concentration.
scanning simulations of nutrient flow rate were conducted
to determine appropriate wall shear stress levels that • The system environment is maintained at 37°C
promote C2C12 cell growth. Furthermore, the impact and 5% carbon dioxide, an optimal condition for
of different dynamic parameters, such as inlet flow rate, cell survival.
geometric feature size, and initial cell density, on scaffold- • The maximum absorption rate of oxygen by cells
based tissue engineering outcomes was examined. Lastly,
based on the modeling system proposed in this study, a linearly increases from zero until a certain time
two-step optimization strategy is proposed for structural point, where it remains constant.
optimization of scaffolds and applied for designing • The cells within the scaffold experience an initial
channeled scaffold with maximum cell proliferation. adhesion phase for the first 3 hours of cultivation,
This strategy offers a novel framework for designing during which their maximum growth rate is zero,
and optimizing multi-channel bioprinted scaffolds followed by linear growth until a certain time
encapsulated with cells for advanced tissue engineering. point where it remains constant.

2. Model physics and implementation • The influence of cell death is not considered in
the model.
2.1. Model assumptions
The multi-physics coupling model for cell growth • The effects of material swelling are ignored.
considers fluid convection, oxygen mass transfer, cellular 2.2. Computational domain
oxygen consumption, and cell growth involved in the In the geometric assembly of the multi-physics model, as
dynamic cultivation process of DLP 3D-printed scaffolds. shown in Figure 1a, the entire geometric space is divided
In practice, the physical processes involved in the entire into two domains: Ω representing the uniform medium
1
cultivation process are more complex. To reduce the flow region of the nutrient solution, and Ω expressing the
2
complexities of the modeling process while maintaining porous medium flow region of the scaffold. The scaffold
satisfactory prediction results, the following assumptions structure in the model is a circular block with a diameter
are made: of 4 mm and a thickness of 2 mm. The chamber is a hollow
• The pores within the scaffold are assumed to be cylindrical structure with an inner diameter D of 5 mm
1
uniformly distributed. and a total length L of 10 mm. The scaffold is placed at the

Figure 1. Geometric assembly of the scaffold in dynamic in vitro cultivation and physical processes of cell growth to be modeled. (a) Schematic diagram
showing the geometry of the computational domain for model simulation. Ω represents the homogeneous medium flow region of the nutrient solution,
1
and Ω is the porous medium flow region of the scaffold. (b) Physical processes incorporated in the model, including fluid convection occurred in domain
2
Ω and Ω , oxygen diffusion in the scaffold, oxygen consumption by cells, and cell growth.
1 2
Volume 10 Issue 3 (2024) 279 doi: 10.36922/ijb.1838