Comparison of a Brush-with-Anchor and a Train-of-Brushes Mucin on Poly(methyl methacrylate) Surfaces: Adsorption, Surface Forces, and Friction

摘要

Interracial properties of two types of mucins have been investigated at the aqueous solution/poly(mefhyl methacrylate) (PMMA) interface. One is commercially available bovine submaxillary mucin, BSM, which consists of alternating glycosylated and non- glycosylated regions. The other one is a recombinant mucin-type fusion protein, PSGL-1/mIgG_(2b), consisting of a glycosylated mucin part fused to the Fc part of an immunoglobulin. PSGL-l/mIgG_(2b) is mainly expressed as a dimer upon production. A quartz crystal microbalance with dissipation was used to study the adsorption of the mucins to PMMA surfaces. The mass of the adsorbed mucin layers, including the adsorbed mucin and water trapped in the layer, was found to be significantly higher for PSGL-l/mIgG_(2b) than for BSM. Atomic force microscopy with colloidal probe was employed to study interactions and factional forces between mucin-coated PMMA surfaces. Purely repulsive forces of steric origin were observed between PSGL-l/mIgG_(2b) mucin layers, whereas a small adhesion was detected between BSM layers and attributed to bridging. Both mucin layers reduced the friction force between PMMA surfaces in aqueous solution. The reduction was, however, significantly more pronounced for PSGL-l/mIgG_(2b). The effective friction coefficient between PSGL-l/mIgG_(2b)-coated PMMA surfaces is as low as 0.02 at low loads, increasing to 0.24 at the highest load explored, SO nN. In contrast, a friction coefficient of around 0.7 was obtained between BSM-coated PMMA surfaces. The large differences in interracial properties for the two mucins are discussed in relation to their structural differences.