• Different macro- and micro-rheological properties of native porcine respiratory and intestinal mucus.

      Bokkasam, Harish; Ernst, Matthias; Guenther, Marco; Wagner, Christian; Schaefer, Ulrich F; Lehr, Claus-Michael; Helmholtz-Institut für pharmazeutische Forschung Saarland, Universitätscampus E8.1, 66123 Saarbrücken. (2016-06-13)
      Aim of this study was to investigate the similarities and differences at macro- and microscale in the viscoelastic properties of mucus that covers the epithelia of the intestinal and respiratory tract. Natural mucus was collected from pulmonary and intestinal regions of healthy pigs. Macro-rheological investigations were carried out through conventional plate-plate rheometry. Microrheology was investigated using optical tweezers. Our data revealed significant differences both in macro- and micro-rheological properties between respiratory and intestinal mucus.
    • A Model for the Transient Subdiffusive Behavior of Particles in Mucus.

      Ernst, Matthias; John, Thomas; Guenther, Marco; Wagner, Christian; Schaefer, Ulrich F; Lehr, Claus-Michael; HIPS, Helmholtz-Institut für pharmazeutische Forschung Saarland, Universitätscampus 8.1, 66123 Saarbrücken, Germany. (2017-01-10)
      In this study we have applied a model to explain the reported subdiffusion of particles in mucus, based on the measured mean squared displacements (MSD). The model considers Brownian diffusion of particles in a confined geometry, made from permeable membranes. The applied model predicts a normal diffusive behavior at very short and long time lags, as observed in several experiments. In between these timescales, we find that the "subdiffusive" regime is only a transient effect, MSD∝τ
    • Optical tweezers reveal relationship between microstructure and nanoparticle penetration of pulmonary mucus.

      Kirch, Julian; Schneider, Andreas; Abou, Bérengère; Hopf, Alexander; Schaefer, Ulrich F; Schneider, Marc; Schall, Christian; Wagner, Christian; Lehr, Claus-Michael (2012-11-06)
      In this study, the mobility of nanoparticles in mucus and similar hydrogels as model systems was assessed to elucidate the link between microscopic diffusion behavior and macroscopic penetration of such gels. Differences in particle adhesion to mucus components were strongly dependent on particle coating. Particles coated with 2 kDa PEG exhibited a decreased adhesion to mucus components, whereas chitosan strongly increased the adhesion. Despite such mucoinert properties of PEG, magnetic nanoparticles of both coatings did not penetrate through native respiratory mucus, resisting high magnetic forces (even for several hours). However, model hydrogels were, indeed, penetrated by both particles in dependency of particle coating, obeying the theory of particle mobility in an external force field. Comparison of penetration data with cryogenic scanning EM images of mucus and the applied model systems suggested particularly high rigidity of the mucin scaffold and a broad pore size distribution in mucus as reasons for the observed particle immobilization. Active probing of the rigidity of mucus and model gels with optical tweezers was used in this context to confirm such properties of mucus on the microscale, thus presenting the missing link between micro- and macroscopical observations. Because of high heterogeneity in the size of the voids and pores in mucus, on small scales, particle mobility will depend on adhesive or inert properties. However, particle translocation over distances larger than a few micrometers is restricted by highly rigid structures within the mucus mesh.