Composite Diaphragm Inflation: A Method for Probing the Rheological Functions of Cell -Cell Anchoring Junctions and Cytoskeletal Networks Within a Living Normal Human Epidermal Keratinocyte Sheet
Selby, John Christopher
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https://hdl.handle.net/2142/83889
Description
Title
Composite Diaphragm Inflation: A Method for Probing the Rheological Functions of Cell -Cell Anchoring Junctions and Cytoskeletal Networks Within a Living Normal Human Epidermal Keratinocyte Sheet
Author(s)
Selby, John Christopher
Issue Date
2007
Doctoral Committee Chair(s)
Shannon, Mark A.
Department of Study
Mechanical Engineering
Discipline
Mechanical Engineering
Degree Granting Institution
University of Illinois at Urbana-Champaign
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(s)
Biophysics, General
Language
eng
Abstract
In this thesis, we validate a new method for the exploration of keratinocyte rheology, referred to as the technique of composite diaphragm inflation (CDI). Sheets of living NHEKs were reconstituted in vitro on tensed but highly compliant, freestanding polydimethylsiloxane (PDMS) elastomer membranes, 5.0 mm in diameter and 10.0 mum thick. NHEK-PDMS composite diaphragm (CD) specimens were then subjected to a series of quasi-static axisymmetric inflation tests to examine the stress response of the epithelial sheet at physiologically severe deformations (∼50% nominal biaxial strains). During these experiments, living NHEK sheets exhibited several unique rheological behaviors, including viscoelasticity, plasticity, and the process of biological adaptation and recovery or a restitutio ad integrum. In addition to a rigorous accounting of the experimental instrumentation and protocol distinct to CDI, a finite elasticity model is proposed for analyzing the mechanics of the associated inflation test. Numerical solution procedures are formulated to predict the quasi-static load-deformation response of a prestretched clamped circular isotropic incompressible hyperelastic membrane inflated into a horizontally semi-infinite incompressible liquid reservoir of finite vertical depth. Assuming a Mooney-Rivlin (MR) constitutive model, we quantitatively demonstrate a new non-traditional regression analysis for estimating values of the MR material parameters and residual membrane tension that best describe a set of experimental inflation response data. Combining improved culture techniques with the more advanced tools of the molecular cell biologist, CDI experiments can potentially transform morphological observations of NHEK cytoarchitecture into well-posed boundary value problems amenable to mechanical experimentation and hypothesis testing.
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