Abstract
We provide qualitative predictions on the rheology of mucus of healthy individuals (Wild Type or WT-mucus) versus those infected with Cystic Fibrosis (CF-mucus) using an experimentally guided, multi-phase, multi-species ionic gel model. The theory which accounts for mucus (as polymer phase), water (as solvent phase) and ions, H$^+$, Na$^+$ and Ca$^{2+}$, is linearized to study the hydration of spherically symmetric mucus gels and calibrated against the experimental data of mucus diffusivities. Near equilibrium, the linearized form of the solution reduces to an expression similar to the well known kinetic theory of neutral gels. Numerical studies reveal that the Donnan potential is the dominating mechanism driving the mucus swelling/deswelling transition. However, the altered swelling kinetics of the Cystic Fibrosis infected mucus is not merely governed by the hydroelectric composition of the swelling media, but also due to the altered movement of electrolytes as well as due to the defective properties of the mucin polymer network.
Highlights
Mucus is a polyelectrolyte biogel that plays a critical role as a protective, exchange and transport medium in the digestive, respiratory and reproductive systems of humans and other vertebrates [1, 2]
The purpose of this paper is to provide a new comprehensive model detailing the swelling kinetics of mucin-like ionic gels and use it to calibrate the rheological data of spherically symmetric mucin granules, exocytosed from the goblet cells of cystic fibrosis (CF)-patients versus those released from the non-CF individuals
The effect of the calcium and the sodium ions in the solvent on the equilibrium size of the mucus blob are detailed in §3.2 and §3.3, respectively
Summary
Mucus is a polyelectrolyte biogel that plays a critical role as a protective, exchange and transport medium in the digestive, respiratory and reproductive systems of humans and other vertebrates [1, 2]. Experiments confirm that this rapid and massive expansion of the mucus gel is driven by an exchange of calcium in the vesicle for a monovalent ion (e.g., Na+) in the extracellular environment [9]. This is because, calcium being divalent, must balance two negative charges rather than one. Experiments demonstrate that the exocytosed mucin is recondensed if the calcium concentration of the ionic medium is increased sufficiently [10] These observations indicate that the amount and the nature of the salt dissolved in the solvent determines the initial and the equilibrium configuration of these gels
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