# Microrheological study of human respiratory mucus

Milad Radiom, Romain Hénault, Salma Mani, Aline Grein-Iankovski, Xavier

Norel, Jean-François Berret

► To cite this version:

Milad Radiom, Romain Hénault, Salma Mani, Aline Grein-Iankovski, Xavier Norel, et al. Microrheological study of human respiratory mucus. Mucus, Cilia and Mucociliary Interactions, Feb 2023, Barga, Italy. hal-04005597

HAL Id: hal-04005597

https://cnrs.hal.science/hal-04005597

Submitted on 26 Feb 2023

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Distributed under a Creative Commons Attribution 4.0 International License
# Microrheological study of human respiratory mucus

Milad Radiom¹,², Romain Hénault¹, Salma Mani³, Aline Grein Iankovski,¹
Xavier Norel³, Jean-François Berret¹*

jean-francois.berret@u-paris.fr

¹Université de Paris, CNRS, Matière et systèmes complexes, 75013 Paris, France

²Institute for Food, Nutrition and Health, D-HEST, ETH Zürich, Zürich, Switzerland

³Université de Paris, INSERM, UMR-S 1148, CHU X. Bichat, 75018 Paris, France; Paris 13 University, 93430 Villetaneuse, France

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## ABSTRACT

Mucus is a viscoelastic gel secreted by the pulmonary epithelium in the tracheobronchial region of the lungs. The coordinated beating of cilia moves mucus upwards towards pharynx, removing inhaled pathogens and particles from the airways. The efficacy of this clearance mechanism depends primarily on the rheological properties of mucus. Here we use magnetic wire based microrheology to study the viscoelastic properties of human mucus collected from human bronchus tubes. The response of wires between 5 and 80 µm in length to a rotating magnetic field is monitored by optical time-lapse microscopy and analyzed using constitutive equations of rheology, including those of Maxwell and Kelvin-Voigt. The static shear viscosity and elastic modulus can be inferred from low frequency (3×10⁻³ – 30 rad s⁻¹) measurements, leading to the evaluation of the mucin network relaxation time. This relaxation time is found to be widely distributed, from one to several hundred seconds. Mucus is identified as a viscoelastic liquid with an elastic modulus of 2.5 ± 0.5 Pa and a static viscosity of 100 ± 40 Pa s. Our work shows that mucus exhibits secondary inhomogeneities associated with the relaxation time of the mucin network that may be important for its flow properties. The results of this work were published in the journal Soft Matter, under the reference: M. Radiom, R. Hénault, S. Mani, A.G. Iankovski, X. Norel, J.-F. Berret, Magnetic Wire Active Microrheology of Human Respiratory Mucus, Soft Matter 17 (2021) 7585-7595.

## INTRODUCTION

### Magnetic wires

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The magnetic wires are fabricated by electrostatic co-assembly between maghemite (γ-Fe₂O₃) nanoparticles and a cationic polymer (PDADMAC), the latter acting as a glue for the nanoparticles.

### Magnetic rotational spectroscopy

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### Human mucus samples

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## RESULTS

Comparison with literature

### Magnetic wire technology

Complex fluids studied by Magnetic Rotational spectroscopy

<table><thead><tr><th>Complex fluids</th><th>Quantities measured</th><th>Rheological class of materials</th><th>Ref.</th></tr></thead><tbody><tr><td>Surfactant wormlike micelles</td><td>η, G, τ</td><td>Maxwell fluid</td><td>A</td></tr><tr><td>Polysaccharide gels</td><td>G<sub>eq</sub>, G</td><td>Soft solid</td><td>B</td></tr><tr><td>Living mammalian cells</td><td>η, G, τ</td><td>Viscoelastic liquid</td><td>C</td></tr><tr><td>Pulmonary surfactant</td><td>η, G<sub>eq</sub>, G</td><td>Newtonian liquid<br>Soft solid</td><td>D</td></tr><tr><td>DNA and NAP proteins</td><td>η, G<sub>eq</sub>, G</td><td>Newtonian liquid<br>Soft solid</td><td>E</td></tr></tbody></table>

[A] L. Chevry et al., Phys. Rev. E 88 (2013) 062306 - [B] F. Loosli et al., ChemPhysChem 17 (2016) 4134-4143. - [C] J.-F. Berret, Nat. Commun. 7 (2016) 10134 - [D] L.-P.-A. Thai et al., ACS Nano 14 (2020) 466-475 - [E] O. El Hamoui et al., Biomacromolecules 21 (2020) 3668-3677.

Validation of wire constitutive equations

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Magnetic rotational spectroscopy performed on water-glycerol viscous fluid of static viscosity 250 mPa s revealed the 1/L*² dependence predicted by the constitutive equations of the wires submitted to a rotational magnetic field.

<figure><img src="image_8.png" /><figcaption>Magnetic wires dispersed in human mucus samples</figcaption></figure>

<table><caption>Magnetic wires dispersed in late Ex Vivo human mucus</caption><thead><tr><th>Mucus type</th><th>Number of wires studied</th></tr></thead><tbody><tr><td>Late Ex Vivo mucus</td><td>40</td></tr><tr><td>Early Ex Vivo mucus</td><td>58</td></tr></tbody></table>

### Optical time-lapse microscopy

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### Viscosity determination

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<table><thead><tr><th>Mucus type</th><th>Viscosity<br>η (Pa s)</th><th>Elastic modulus<br>G (Pa)</th><th>Relaxation time<br>τ (s)</th></tr></thead><tbody><tr><td>Late Ex Vivo mucus</td><td>100 ± 40</td><td>2.5 ± 0.5</td><td>47 ± 12</td></tr><tr><td>Early Ex Vivo mucus</td><td>180 ± 30</td><td>4.4 ± 0.5</td><td>49 ± 6</td></tr></tbody></table>

Comparison with literature

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## REFERENCES

R. Bansil and B. S. Turner, Adv. Drug. Deliv. Rev., 2018, 124, 3-15
B. Button, H. P. Goodell, E. Atieh, Y.-C. Chen, R. Williams, S. Shenoy et al., PNAS 2018, 115, 12501-12506
B. S. Schuster, J. S. Suk, G. F. Woodworth and J. Hanes, Biomaterials, 2013, 34, 3439-3446
J.-F. Berret, Nat. Commun., 2016, 7, 10134
L.-P.-A. Thai, F. Mousseau, E. Oikonomou, M. Radiom and J.-F. Berret, ACS Nano, 2020, 14, 466-475

**M. Radiom, R. Hénault, S. Mani, A.G. Iankovski, X. Norel, J.-F. Berret,**
*Soft Matter* 17 (2021) 7585-7595

## CONCLUSION

In this work we propose a new active microrheology technique to determine the rheological characteristics of human respiratory mucus. The probes used are remotely actuated magnetic wires of lengths between 5 and 80 µm, i.e. much greater than the size of the microcavities observed in mucus samples. Human mucus is identified as a viscoelastic liquid with an elastic modulus of a few Pa and a static viscosity of the order of 100 Pa s. This work also shows that mucus exhibits strong inhomogeneities associated with the relaxation times of the mucin network.