Human Laryngeal Mucus from the Vocal Folds: Rheological Characterization by Particle Tracking Microrheology and Oscillatory Shear Rheology

Abstract

Mucus consistency affects voice physiology and is connected to voice disorders. Nevertheless, the rheological characteristics of human laryngeal mucus from the vocal folds remain unknown. Knowledge about mucus viscoelasticity enables fabrication of artificial mucus with natural properties, more realistic ex-vivo experiments and promotes a better understanding and improved treatment of dysphonia with regard to mucus consistency. We studied human laryngeal mucus samples from the vocal folds with two complementary approaches: 19 samples were successfully applied to particle tracking microrheology (PTM) and five additional samples to oscillatory shear rheology (OSR). Mucus was collected by experienced laryngologists from patients together with demographic data. The analysis of the viscoelasticity revealed diversity among the investigated mucus samples according to their rigidity (absolute G’ and G”). Moreover some samples revealed throughout solid-like character (G’ > G”), whereas some underwent a change from solid-like to liquid-like (G’ < G”). This led to a subdivision into three groups. We assume that the reason for the differences is a variation in the hydration level of the mucus, which affects the mucin concentration and network formation factors of the mucin mesh. The demographic data could not be correlated to the differences, except for the smoking behavior. Mucus of predominant liquid-like character was associated with current smokers.

Drop-of-sample rheometry of biological fluids by noncontact acoustic tweezing spectroscopy

“…Small volume rheology is also required for pathological analysis of the vitreous, a fluid that fills the eye [63][64][65][66][67] as well as severity analysis of lung infection 68 and vocal disorders. 69 The total vitreous volume in human eyes is about 4 ml, 70 while the collected volume of human laryngeal mucus ranges from 10 μl to 1.8ml. 69 The ATS enables safe and reliable analysis of these fluids.…”

“…69 The total vitreous volume in human eyes is about 4 ml, 70 while the collected volume of human laryngeal mucus ranges from 10 μl to 1.8ml. 69 The ATS enables safe and reliable analysis of these fluids.…”

Passive and Active Microrheology for Biomedical Systems

“…Additionally, rheological properties of lung and airway mucus have been tied to disease states for many respiratory ailments: cystic fibrosis, laryngeal tuberculosis, bronchitis, asthma, chronic obstructive pulmonary disorder (COPD), voice disorders, and lung plaque buildup from smoking ( Lai et al, 2009b ; Lin et al, 2020 ; Peters et al, 2021 ). The microrheology of pulmonary mucus also directly affects the movement of this protective barrier throughout the lung and airway and, therefore, its effectiveness as a protective barrier.…”

“…Respiratory mucus originating from the vocal cords plays an essential role in voice disorder pathology in smokers. Recently, researchers investigated laryngeal mucus collected from the vocal folds of smokers and non-smokers using both VPT and bulk rheology ( Peters et al, 2021 ). Both methods uncovered gel-like characteristics in all groups; however, mucus rigidity varied depending on the smoking habits of the subject.…”

Special Issue on Computational Methods and Engineering Solutions to Voice II

“…The influence of laryngeal mucus towards vocal fold oscillations has been discussed during the last few years. Peters et al [14] perform rheological characterization by particle tracking micro-rheology and oscillatory shear rheology on human mucus to gain further insight into viscoelasticity. In their preliminary study, they found great diversity and grouped the mucus samples in three categories.…”