Modeling of time dependent localized flow shear stress and its impact on cellular growth within additive manufactured titanium implants.
Bottom Line: The model's effectiveness is demonstrated for two additive manufactured (AM) titanium scaffold architectures.The results demonstrate that there is a complex interaction of flow rate and strut architecture, resulting in partially randomized structures having a preferential impact on stimulating cell migration in 3D porous structures for higher flow rates.This novel result demonstrates the potential new insights that can be gained via the modeling tool developed, and how the model can be used to perform what-if simulations to design AM structures to specific functional requirements.
Affiliation: Department of Materials, Imperial College London, London, SW7 2AZ, UK.Show MeSH
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Mentions: Figure 1 shows a schematic of bone with mechanical deformation induced interstitial fluid flow. The mechanical movement induces the interstitial fluid flow and applies shear on cells. Similar to the mechanical loading system, flow-induced shear stress applied on the implant structure via in vitro three-dimensional (3D) perfusion systems has also been found to have important stimulatory effects on cell and tissue growth.3,11,12 Raimondi et al.13,14 was first to perfuse the culture medium through the 3D inner structure of the chondrocyte-seeded scaffold and predicted that a wall shear stress in the range 1.5–13.5 mPa was required for the stimulation of higher cell viability. By assessing the MC3T3-E1 osteoblast-like cell viability qualitatively by confocal microscopy and measuring the DNA content within the scaffolds, Cartmell et al.15 suggested that for a positive effect on seeded cell viability and proliferation in vitro, fluid shear stress ranging from 0.05 to 25 mPa was desired. Knowledge of how shear stress relates to bone precursor cell migration, attachment and proliferation (termed cellular growth from here on) in various design architectures can help optimize both implant design and manufacture. An understanding of fluid-induced shear stress within porous structures and induced bone ingrowth, is therefore of great importance and has been studied numerically by several prior authors.14,16–23
Affiliation: Department of Materials, Imperial College London, London, SW7 2AZ, UK.