Establishing a Xanthan Gum-Locust Bean Gum Mucus Mimic for Cystic Fibrosis Models: Yield Stress and Viscoelasticity Analysis

Abstract

Airway mucus plays a critical role in respiratory health, with diseases such as cystic fibrosis (CF) being characterized by mucus that exhibits increased viscosity and altered viscoelasticity. In vitro models that emulate these properties are essential for understanding the impact of CF mucus on airway function and for the development of therapeutic strategies. This study characterizes a mucus mimic composed of xanthan gum and locust bean gum, which is designed to exhibit the rheological properties of CF mucus. Mucus concentrations ranging from 0.07% to 0.3% w/v were tested to simulate different states of bacterial infection in CF. Key rheological parameters, including yield stress, storage modulus, loss modulus, and viscosity, were measured using an HR2 rheometer with strain sweep, oscillation frequency, and flow ramp tests. The results show that increasing the concentration enhanced the mimic's elasticity and yield stress, with values aligning with those reported for CF mucus in pathological states. These findings provide a quantitative framework for tuning the rheological properties of mucus in vitro, allowing for the simulation of CF mucus across a range of concentrations. This mucus mimic is cost-effective, readily cross-linked, and provides a foundation for future studies examining the mechanobiological effects of mucus yield stress on epithelial cell layers, particularly in the context of bacterial infections and airway disease modeling.

Keywords: biomimetic mucus; cystic fibrosis; mucus rheology; viscoelasticity; yield stress.

Figure A1

Nuclei segmentation tool count from a sample image on day 5, demonstrating cell viability fluorescence quantification: (a) DAPI fluorescence staining showing nuclei, with the corresponding nuclei count overlay below; (b) FITC fluorescence staining indicating live cells, with the corresponding nuclei count overlay below.

Figure A2

Particle size analysis of 1:3 xanthan–gum mixture.

Figure 1

Oscillation frequency test results among 5 concentrations of 1:3 xanthan–locust bean gum: (a) 0.07% concentration with angular frequency (rad/s) plotted against Moduli (Pa) (the 0.1–1 rad/s range was cut out due to the rheometer operating at its limit; the data were not supportive of behavior); (b) 0.10% concentration; (c) 0.15% concentration; (d) 0.20% concentration; and (e) 0.30% concentration.

Figure 2

Flow ramp test displaying all 5 tested concentrations as shear rate (s⁻¹) vs. viscosity (Pa·s).

Figure 3

Oscillation amplitude test across all concentrations as oscillation strain % vs. moduli (Pa): (a) 0.07% concentration; (b) 0.10% concentration; (c) 0.15% concentration; (d) 0.20% concentration; and (e) 0.30% concentration.

Figure 4

Stress ramp test as a function of time (s) vs. viscosity (Pa·s): (a) 0.07% concentration; (b) 0.10% concentration; (c) 0.15% concentration; (d) 0.20% concentration; and (e) 0.30% concentration.

Figure 5

Viability of 16HBE14o- cells treated with control, thin mucus (0.07%), or thick mucus (0.3%) at days 0, 1, 3, and 5. Data reported as arithmetic mean ± standard deviation. Significance was determined using the Kruskal–Wallis test, and no significant differences between conditions were observed (p > 0.05).