Mucus is a biomaterial with peculiar, gel-like viscoelastic properties, and bearing different functionalities, depending on the different mucosae it covers. It is clear that these functionalities have to stay effective throughout the in vivo broad range of physiological pH values at which the mucus is exposed. We sought here to determine the effect of pH on the rheological properties of ex vivo mucus. We demonstrate that viscoelastic properties of gastric mucus are quite "stable" to pH changes, in marked contrast with the pH sensitivity of purified mucin gels. We also find that the rheological features of porcine gastric mucus are reversible when the system is first alkalized up to solubilization (pH > 8.5) and then re-acidified to its initial pH value.

We investigate the spontaneous restructuring and aging behavior of pig gastric mucus gels by combining rheology and nonconventional static and dynamic light scattering. We find that the mucus elasticity weakens over time, concomitantly to structural evolution toward a locally more compact configuration and the onset of large scale density fluctuations. We interpret this behavior as stemming from an arrested phase separation, as observed in many gel-forming polymer systems. This scenario is confirmed by space and time resolved dynamic light scattering data, showing that the gel restructuring is due to intermittent bursts of spatially correlated rearrangements, leading to ballistic dynamics.

Background: In CF patients, the defective ion transport causes a simultaneous reduction of fluid, Cl- and HCO3- secretion. We aimed to demonstrate that the resulting altered properties of mucus can be recovered using lumacaftor, a CFTR corrector. Methods: The micro-rheology of non-CF and CF mucus was analysed using Multiple Particle Tracking. Results: The diffusion coefficient of nano-beads imbedded in mucus from CF human bronchial epithelium was lower than in non-CF mucus, and the elastic and viscous moduli were higher. We found that 25% correction of F508del-CFTR mutation with lumacaftor was enough to improve significantly CF mucus properties. Surprisingly, also incubation with amiloride, a compound that reduces fluid absorption but might not change the secretion of HCO3- towards the airway surface fluid, improved CF mucus properties. Conclusion: CF mucus properties can be recovered by either improving the hydration of the airways or recovering Cl- and HCO3- secretion across the mutated protein treated with a corrector compound

The polychaete Myxicola infundibulum (Renier) produces a large amount of dense mucus which forms a gelatinous envelope where the worm lives. In the present study we evaluated some of the physical-chemical properties of this matrix such as viscosity, osmolarity, electrical conductivity, and protein, carbohydrate and total lipid content The presence of an antibacterial lysozyme-like activity as well as the density of culturable bacteria at 22 degrees C and vibrios and associated macrofauna were also investigated. The water content of M. infundibulum mucus was 95 +/- 0.5%. By dry weight, 38 +/- 1.2% was protein, 2 +/- 021% was carbohydrate and only 3% was lipid. Most of the remainder of the dry weight (about 57%) was inorganic. The mucus of M. infundibulum exerted a lysozyme-like activity evidenced on Petri dishes inoculated with Micrococcus luteus cell walls with a diameter of lysis of 8.4 +/- 0.3 mm, corresponding to 1.15 mg ml(-1) of hen egg white lysozyme. Notwithstanding this high antibacterial activity, the mucous tubes of M. infundibulum contained a high density of culturable heterotrophic bacteria at 22 degrees C, of which presumptive culturable vibrios accounted for 4.6 +/- 0.2 x 10(3) CPU ml(-1). Moreover, tubes were found to be colonized by several specimens of the polychaete Lumbrineris cfr. latreilli. Therefore the mucus of M. infundibutum appears to provide defence against some bacteria and food supply for the growth of others, that in turn could be utilized by macrofaunal organisms. On account of these features this matrix represents an accessible and renewable resource that could repay further exploration from several points of view. (C) 2014 Elsevier B.V. All rights reserved.