(388) Rapid Viscoelastic Characterization of Airway Mucus Using a Benchtop Rheometer

Background: In muco-obstructive lung diseases (e.g., CF, asthma, COPD) and other respiratory conditions (e.g., viral/bacterial infections), mucus biophysical properties are altered by goblet cell hypersecretion, airway dehydration, pH alteration, and inflammation that elicits oxidative stress and the release of extracellular DNA. Previous studies showed that sputum viscoelasticity correlated with pulmonary function. In addition, treatments affecting sputum rheology (e.g., rhDNase in CF) resulted in remarkable clinical benefits. In general, rheological measurements of non-Newtonian fluids rely on elaborate, time-consuming approaches (e.g., parallel/cone-plate rheometers and/or microbead particle tracking) that require extensive training to perform the assay and interpret the data. This study tested the reliability, reproducibility, and sensitivity of Rheomuco, a user-friendly benchtop device that is designed to perform rapid viscoelastic measurements of mucus and sputum in a fast-paced clinical setting. The straightforward protocol and standardized calibration were developed to generate accurate viscoelastic measurements of mucus samples by non-rheology specialists.

Methods: Rheomuco operates by measuring torque and displacement following oscillations with controlled angular displacement to produce a standardized strain sweep curve and establish a linear viscoelastic region (LVR). The dynamic oscillation with a shear-strain sweep provides linear viscoelastic moduli (G’, G”, G^*, tan δ) and gel point characteristics (γ_c and σ_c) for clinical samples within 5 min. Device performance was validated using different concentrations of a mucus simulant, 8 MDa polyethylene oxide (PEO) against a traditional bulk rheometer (DHR-3, TA Instruments). A clinical isolate harvested from an intubated patient suffering from status asthmaticus was assessed in triplicate measurements, as well as the effects of a potent mucus reducing agent, tris (2-carboxylethyl) phosphine hydrochloride (TCEP).

Results: PEO solutions were viscous-dominated (G” >G') and values were comparable between Rheomuco and DHR-3 traditional rheometer. Triplicate measurements performed on 1.5% PEO solution and asthmatic mucus confirmed that linear viscoelastic characteristics (G*, G’, and G”) were repeatable, with < 10% coefficient of variation for the biological sample TCEP treatment (Final concentration of 20 μM for 20 min at 37°C) of asthmatic mucus resulted in a 5-fold decrease in elastic modulus and a change toward a more “liquid-like” behavior overall (e.g., higher tan δ).

Conclusions: These results demonstrate that Rheomuco performs rapid and reliable viscoelasticity measurements of mucus samples. Therefore, Rheomuco could be used to explore the effects of approved mucolytic drugs (e.g., rhDNase, N-acetyl cysteine) in clinics to adapt treatment on a case-by-case basis, or in laboratory preclinical studies to test the efficacy of novel mucoactive compounds.

Acknowledgements: This work was supported by grants from Vertex Pharmaceuticals (Ehre RIA Award) and CFF-supported Research EHRE20XX0.

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