Biopolymer Mucoadhesives

Atomic force microscopy of gastric mucin and chitosan mucoadhesive systems

“…The findings in the present study, based on AFM imaging, clearly support the earlier molecular data based on molecular hydrodynamics, electron microscopy and scanning tunnelling microscopy [7]. Molecular imaging, which ' visualizes ' macromolecules, coupled with molecular hydrodynamics, which refers to macromolecules in their ' natural physiological state ' unperturbed by sample preparation protocols, is clearly a powerful combination for the study of this and other heterogeneous molecular systems.…”

“…Molecular imaging, which ' visualizes ' macromolecules, coupled with molecular hydrodynamics, which refers to macromolecules in their ' natural physiological state ' unperturbed by sample preparation protocols, is clearly a powerful combination for the study of this and other heterogeneous molecular systems. The main contribution towards the interaction is clearly electrostatic, with some hydrophobic contribution [7]. The AFM data also support the macroscopic tensiometric measurements [9].…”

“…150 nm (visualized in the same way as those structures at 0.1 M). Noticeably there is a greater number of these ' mucoadhesive complexes ' at 0.1 M ionic strength, suggesting a reduction in interaction between the mucin and chitosan as the ionic strength increases beyond physiologically relevant conditions, and consistent with what was observed earlier by molecular hydrodynamics [7,29]. Charge suppression clearly reduces the amount of electrostatic interaction.…”

“…As has been previously indicated [7,19,20,29] a significant interaction has been shown between the purified PGM and this form of chitosan on the basis of molecular hydrodynamics, electron microscopy and scanning tunnelling microscopy, consistent with macroscopic tensiometry studies [9]. Figure 4 illustrates the complex formed between the chitosan and mucin structures when mixed together in solution and then immobilized to the APTES-coated substrate.…”

“…Prime targets have been the gastrointestinal tract and also the ocular surface to (1) retard the natural clearing action of the body, slowing down the transit through the optimal sites of absorption in the stomach, intestine and colon [7] and (2) slow down the washing away action on the surface of the eye [8], respectively. In order to develop the most efficient systems, a sensible approach is to take advantage of the considerable advances in our knowledge of the structure and molecular Abbreviations used : AFM, atomic force microscopy ; PGM, pig gastric mucin ; APTES, aminopropyl-triethoxysilane ; RMS, root-mean-square ; SC210j, sea cure j210 ; z, vertical displacement.…”