Macro-scale Topology Optimization for Controlling Internal Shear Stress in a Porous Scaffold Bioreactor

TL;DR

This paper presents a novel macro-scale topology optimization method for controlling shear stress distribution in porous scaffold bioreactors, enhancing the ability to mimic physiological conditions for improved cell culture outcomes.

Contribution

It introduces a topology optimization approach coupled with CFD simulations to design scaffold channels for uniform shear stress, validated by MRI experiments.

Findings

Optimized channel topologies achieve targeted shear stress levels.

The method improves uniformity of shear stress distribution.

Experimental validation confirms the effectiveness of the optimization.

Abstract

Shear stress is an important physical factor that regulates proliferation, migration and morphogenesis. In particular, the homeostasis of blood vessels is dependent on shear stress. To mimic this process ex vivo, efforts have been made to seed scaffolds with vascular and other cell types in the presence of growth factors and under pulsatile flow conditions. However, the resulting bioreactors lack information on shear stress and flow distributions within the scaffold. Consequently, it is difficult to interpret the effects of shear stress on cell function. Such knowledge would enable researchers to improve upon cell culture protocols. Recent work has focused on optimizing the microstructural parameters of the scaffold to fine tune the shear stress. In this study, we have adopted a different approach whereby flows are redirected throughout the bioreactor along channels patterned in the porous scaffold to yield shear stress distributions that are optimized for uniformity centered on a target value. A topology optimization algorithm coupled to computational fluid dynamics simulations was devised to this end. The channel topology in the porous scaffold was varied using a combination of genetic algorithm and fuzzy logic. The method is validated by experiments using magnetic resonance imaging (MRI) readouts of the flow field.