A synergetic lubricating effect between porcine gastric mucin (PGM) and chitosan based on their mucoadhesive interaction is reported at a hydrophobic interface comprised of self-mated polydimethylsiloxane (PDMS) surfaces. In acidic solution (pH 3.2) and low concentrations (0.1 mg mL(-1)), the interaction of PGM with chitosan led to surface recharge and size shrinkage of their aggregates. This resulted in higher mass adsorption on the PDMS surface with an increasing weight ratio of [chitosan]/[PGM + chitosan] up to 0.50. While neither PGM nor chitosan exhibited slippery characteristics, the coefficient of friction being close to 1, their mixture improved considerably the lubricating efficiency (the coefficient of friction is 0.011 at an optimum mixing ratio) and wear resistance of the adsorbed layers. These findings are explained by the role of chitosan as a physical crosslinker within the adsorbed PGM layers, resulting in higher cohesion and lower interlayer chain interpenetration and bridging.

The structural and mechanical properties of thin films generated from two types of mucins, namely bovine submaxillary mucin (BSM) and porcine gastric mucin (PGM) in aqueous environment were investigated with several bulk and surface analytical techniques. Both mucins generated hydrated films on hydrophobic polydimethylsiloxane (PDMS) surfaces from 2 spontaneous adsorption arising from their amphiphilic characteristic. But, BSM formed more elastic films than PGM at neutral pH condition. This structural difference was manifested from the initial film formation processes to the responses to shear stresses applied to the films.Acidification of environmental pH led to strengthening the elastic character of BSM films with increased adsorbed mass, whereas an opposite trend was observed for PGM films. We propose that this contrast originates from that negatively charged motifs are present for both the central and terminal regions of BSM molecule, whereas a similar magnitude of negative charges is localized at the termini of PGM molecule. Given that hydrophobic motifs acting as anchor are also localized in the terminal region, electrostatic repulsion between anchoring units of PGM molecules on nonpolar PDMS surface leads to weakening of the mechanical integrity of the films.

No abstract

No abstract