Excessive shear rate, not shear stress, influences cell mechanical damage in small-bore needle injections
File(s)
Published version
Author(s)
Type
Journal Article
Abstract
Cell therapies and 3D bioprinting often require suspended cells to be delivered through needles of 20-gauge and smaller. This often damages cells, affecting their short and long-term viability. Most researchers have attributed this to excessive viscous stresses encountered entering or within the needle, but the experimental evidence contradicts that, as higher viscosity suspension fluids generally yield higher cell viabilities when injected at the same flow rate. We therefore sought to determine the most relevant fluid flow parameter influencing cell mechanical damage. A combination of reprocessing published results and cell injection experiments were conducted. Human umbilical vein endothelial cells (HUVECs) were suspended in Newtonian fluids of varying viscosities and injected through 30-gauge syringe needles in experiments that controlled for either shear stress or shear rate (a kinematic quantity expressing relative velocity of adjacent fluid layers). Based on evidence from injection experiments using a variety of fluids, it is shown that increasing shear rate better explains reductions in cell viability than increasing shear stress. Knowledge that shear rate is a more relevant fluid mechanical parameter governing mechanical damage provides a rational basis for designing injection protocols (injectors and suspension fluid rheological properties) to maximize cell viability.
Date Issued
2026-06-01
Date Acceptance
2026-02-11
Citation
Journal of Biomechanical Engineering, 2026, 148 (6)
ISSN
0148-0731
Publisher
American Society of Mechanical Engineers
Journal / Book Title
Journal of Biomechanical Engineering
Volume
148
Issue
6
Copyright Statement
© 2026 by ASME; reuse license CC-BY 4.0 (https://creativecommons.org/licenses/by/4.0/)
License URL
Identifier
10.1115/1.4071455]
Subjects
cell therapy
bioprinting
biofluid mechanics
bioinks
viability
Publication Status
Published
Article Number
061005
Date Publish Online
2026-04-08