Conditioning materials with biomacromolecules: Composition of the adlayer and influence on cleanability

Abstract

AbbreviationsBSA: bovine serum albumin RFC: radial flow cell XPS: X-ray photoelectron spectroscopy 2 ABSTRACTThe influence of substrate hydrophobicity and biomacromolecules (dextran, bovine serum albumin -BSA) adsorption on the cleanability of surfaces soiled by spraying aqueous suspensions of quartz particles (10 to 30 µm size), then dried, was investigated using glass and polystyrene as substrates. The cleanability was evaluated using radial flow cell (RFC).The surface composition was determined by X-ray photoelectron spectroscopy (XPS). The interpretation of XPS data allowed the complexity due to the ubiquitous presence of organic contaminants to be coped with, and the surface composition to be expressed in terms of both the amount of adlayer and the mass concentration of adlayer constituents.When soiled with a suspension of particles in water, glass was much less cleanable than polystyrene, which was attributed to its much lower water contact angle, in agreement with previous observations on starch soil. Dextran was easily desorbed and did not affect the cleanability. The presence of BSA at the interface strongly improved the cleanability of glass while the contact angle did not change appreciably. In contrast, soiling polystyrene with quartz particles suspended in a BSA solution instead of water did not change markedly the cleanability, while the contact angle was much lower and the aggregates of soiling particles were more flat. These observations are explained by the major role of capillary forces developed upon drying, which influence the closeness of the contact between the soiling particles and the substrate and, thereby, the adherence of particles. The capillary forces are proportional to the liquid surface tension and depend in a more complex way on contact angles of the particles and of the substrate. The dependence of cleanability on capillary forces, and in particular on the liquid surface tension, is predominant as compared with its dependence on the size and shape of the soiling aggregates, which influence the efficiency of shear forces exerted by the flowing water upon cleaning.

Influence of substrate nature and β-lactoglobulin on cleanability after soiling by suspension spraying and drying

“…The presence of bovine serum albumin (BSA) had little effect on the particles adherence to a hydrophobic substrate (polystyrene) but decreased drastically their adherence to a more hydrophilic substrate (glass), bringing it to the range observed for polystyrene. There was no significant difference in particle adherence depending on whether BSA was involved by conditioning the substrate before soiling, or by its presence in the soiling suspension, or both ways (Touré et al, 2014a). BSA did adsorb on quartz particles and on glass and polystyrene but its influence on particle adherence to glass was attributed to the lowering of the liquid surface tension, leading to a decrease of capillary forces created during drying.…”

“…The choice of β-LGB concentration in the quartz suspension was based on β-LGB concentration in bovine milk (3 g/L) (Walstra and Jenness, 1984). The soiling procedure, cleanability assessment and data processing are detailed in previous studies (Detry et al, 2011;Touré et al, 2011Touré et al, , 2013Touré et al, , 2014a. Briefly, suspension droplets were deposited by spraying at room temperature.…”

“…In order to get a better quantitative representation of the composition of the organic layer, the relative mass concentration of its constituents was computed from the mole fraction of markers and the related molar mass as shown in previous work for BSA (Touré et al, 2014a). The marker used for β-LGB was nitrogen.…”

“…The influence of β-lactoblobulin (β-LGB) on quartz adherence to glass was analogous to that of BSA (Touré et al, 2013). The effect of dextran was weak in accordance with a weak effect on liquid surface tension and with a low adsorption by solids or easy desorption (Touré et al, 2014a(Touré et al, , 2011.…”

“…The influence of macromolecules (Touré et al, 2014a(Touré et al, , 2013(Touré et al, , 2011 on the adherence of model particulate soils (quartz particles) was examined using substrates which differed according to hydrophobicity. The presence of bovine serum albumin (BSA) had little effect on the particles adherence to a hydrophobic substrate (polystyrene) but decreased drastically their adherence to a more hydrophilic substrate (glass), bringing it to the range observed for polystyrene.…”