title: Atomic force microscopy of gastric mucin and chitosan mucoadhesive systems.
abstract: Atomic force microscopy has been utilized to probe, at a molecular level, the interaction between purified pig gastric mucin (PGM) and a mucoadhesive cationic polymer, chitosan (sea cure 210+), with a low degree (approx. 11%) of acetylation. Images were produced detailing the structures of both PGM and chitosan in 0.1 M acetate buffer (pH 4.5), followed by the complex of the two structures in the same buffer. PGM in 0.1 M acetate buffer revealed long linear filamentous structures, consistent with earlier electron microscopy and scanning tunnelling micoscopy studies. The chitosan molecules also adopted a linear conformation in the same buffer, although with a smaller average length and diameter. They appeared to adopt a stiff-coil conformation consistent with earlier hydrodynamic measurements. The complexes formed after mixing PGM and chitosan together revealed large aggregates. In 0.1 M ionic strength buffer they were of the order of 0.7 microm in diameter, consistent with previous electron microscopy studies. The effect of ionic strength of the buffer on the structure of the complex was also studied and, together with molecular hydrodynamic data, demonstrates that the interaction is principally electrostatic in nature.
authors.affiliation: University of Nottingham, NCMH Physical Biochemistry Laboratory, School of Biosciences, Sutton Bonington LE12 5RD, UK.
authors.forename: M P
authors.initials: MP
authors.lastname: Deacon
authors.forename: S
authors.initials: S
authors.lastname: McGurk
authors.forename: C J
authors.initials: CJ
authors.lastname: Roberts
authors.forename: P M
authors.initials: PM
authors.lastname: Williams
authors.forename: S J
authors.initials: SJ
authors.lastname: Tendler
authors.forename: M C
authors.initials: MC
authors.lastname: Davies
authors.forename: S S
authors.initials: SS
authors.lastname: Davis
authors.forename: S E
authors.initials: SE
authors.lastname: Harding
mesh_terms: D000818:Animals; D002686:Chitin / Q000031:analogs & derivatives* / Q000737:chemistry; D048271:Chitosan; D018625:Microscopy, Atomic Force; D009077:Mucins / Q000737:chemistry*; D013270:Stomach / Q000737:chemistry*; D013552:Swine; D014014:Tissue Adhesives
chemical_list: D009077:Mucins; D014014:Tissue Adhesives; D002686:Chitin; D048271:Chitosan