Hydrophobins as aqueous lubricant additive for a soft sliding contact

Seunghwan Lee, Troels Røn, Kirsi I. Pakkanen, Markus Linder

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    Two type II fungal hydrophobins, HFBI and FpHYD5, have been studied as aqueous lubricant additive at a nonpolar, compliant sliding contact (self-mated poly(dimethylsiloxane) (PDMS) contact) at two different concentrations, 0.1 mg/mL and 1.0 mg/mL. The two hydrophobins are featured as non-glycosylated (HFBI, m.w. ca. 7 kDa) vs glycosylated (FpHYD5, m.w. ca. 10 kDa) proteins. Far UV CD spectra of the two hydrophobins were very similar, suggesting overall structural similarity, but showed a noticeable difference according to the concentration. This is proposed to be related to the formation of multimers at 1.0 mg/mL. Despite ten-fold difference in the bulk concentration, the adsorbed masses of the hydrophobins onto PDMS surface obtained from the two solutions (0.1 and 1.0 mg/mL) were nearly identical, suggesting that a monolayer of the hydrophobins are formed from 0.1 mg/mL solution. PDMS-PDMS sliding interface was effectively lubricated by the hydrophobin solutions, and showed a reduction in the coefficient of friction by as much as ca. two orders of magnitude. Higher concentration solution (1.0 mg/mL) provided a superior lubrication, particularly in low-speed regime, where boundary lubrication characteristic is dominant via ‘self-healing’ mechanism. FpHYD5 revealed a better lubrication than HFBI presumably due to the presence of glycans and improved hydration of the sliding interface. Two type II hydrophobins function more favorably compared to a synthetic amphiphilic copolymer, PEO-PPO-PEO, with a similar molecular weight. This is ascribed to higher amount of adsorption of the hydrophobins to hydrophobic surfaces from aqueous solution.
    Original languageEnglish
    JournalColloids and Surfaces B: Biointerfaces
    Pages (from-to)264–269
    Publication statusPublished - 2015

    Bibliographical note

    The authors are grateful for the financial support from the Danish Council for Independent Research (DFF), Technology and Production Sciences (FTP) (10-082707), European Research Council (Funding scheme, ERC Starting Grant 2010, Project number 261152), and COST Action program (TD1003, Bioinspired Nanotechnologies).


    • Hydrophobin
    • Amphiphilic
    • FpHYD5
    • HFBI
    • Lubrication


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