Transmission electron microscopy studies on pig gastric mucin and its interactions with chitosan

Atomic force microscopy of gastric mucin and chitosan mucoadhesive systems

“…The images were selected at random and are representative of a large library of images, which portray similar structural information and surface coverage. The PGM appears as long filamentous strands, which is in good agreement with previous studies using electron and scanning tunnelling microscopy [18][19][20][21], and consistent with the swollen coil array\linear random coil model for mucins [4,23]. The characteristic flattened areas along the backbone seen earlier from electron microscopy for PGM and earlier for bronchial mucins [23] were notably absent.…”

“…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. Instead of the characteristic filamentous nature of both the chitosan and PGM (Figures 2 and 3, respectively) large clump-like aggregates were observed, consistent with the electron microscopy observations of Fiebrig et al [19,20]. The average diameter of these aggregates, determined by taking two diameter measurements (x and y) on a large number of aggregates (20) was approx.…”

“…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.…”

“…In order to reveal both the thin filamentous nature of the gastric mucin structure previously shown with transmission electron [ [18][19][20] and scanning tunnelling microscopy [21], together with the previously unvisualized characteristics of chitosan, an extremely flat sample substrate is required. To this end, mica was chosen for this study.…”

“…With the previous imaging studies on PGMs by transmission electron microscopy [18][19][20], to facilitate visualization it had been necessary to coat the substrate with a thin layer of conductive material, and the mucins themselves were sprayed onto the surface of this substrate. The advantage of AFM over this is that the mucins may be adsorbed directly from solution and do not require further sample treatment prior to visualization.…”