A Rheological Evaluation of Various Mucus Gels for Use in In‐vitro Mucoadhesion Testing

Abstract

Gastric mucus, obtained from various sources has been used in many bioadhesion studies, particularly those concerning rheological synergism between mucus and putative mucoadhesives. This study used dynamic oscillatory rheology to compare the behaviour of commercially obtained mucins with mucin samples prepared directly from porcine stomachs, with regard to their use in rheological studies of bioadhesion. All commercial mucins were found to be viscous sols, giving mechanical spectra typical of dilute polymer solutions with a non-ordered polymeric structure rather than the typical viscoelastic behaviour of native mucus, even at concentrations far in excess of those seen in-vivo. Homogenized mucus, containing protease inhibitors, behaved like a viscoelastic gel, giving tan δ values < 1, while a crude mucus sample showed markedly less gellike properties, presumably as a result of degradation processes that had occurred before testing. It was concluded that the homogenized mucus sample was the best rheological model for a mucus gel, and will be used in all further studies. Commercially obtained mucins showed little similarity to native mucus in their behaviour, and are therefore inappropriate models for use in rheological investigations.