Influence of ionic strength changes on the structure of pre-adsorbed salivary films. A response of a natural multi-component layer

Lubrication and load-bearing properties of human salivary pellicles adsorbed ex vivo on molecularly smooth substrata

“…The differences between the SAL-I and SAL-D systems could have arisen from the additional rinsing steps, use of pure water as the solvent, or saliva ageing in the SAL-I study, which removed or gave rise to a structural change in the adsorbed salivary film, resulting in a mechanically more dense and rapidly-relaxing layer for SAL-I. The possibility of a structural change owing to the use of pure water is supported by a QCM-D study by Macakova et al (2010), where rinsing with pure water led to an irreversible expulsion of water from the film and collapse in the layer thickness. The postcollapse film thickness in that study was 5.7 nm, very similar to the 6 nm compressed layer thickness deduced under comparable conditions in the SAL-I measurements.…”

“…The postcollapse film thickness in that study was 5.7 nm, very similar to the 6 nm compressed layer thickness deduced under comparable conditions in the SAL-I measurements. Post-collapse, Macakova et al (2010) found that subsequent addition of salt had only a minor effect on restoring the layer thickness and solvent content. These observations are also consistent with the present results that show nearly-identical behaviour for the SAL-I system under pure water and 70 mM salt.…”

“…Large molecules such as mucins may have been removed by the SAL-D filtration, and rinsing with pure water (SAL-I) has been shown (Macakova et al 2010) to affect the structure of an adsorbed salivary film formed under intact saliva. The SAL-I investigation nonetheless allowed the use of the highly-sensitive SFB to provide detailed insight into the properties of an adsorbed salivary film under conditions that may reflect those experienced when teeth are rinsed, for example, during the consumption of beverages, and provides information on the structural changes in a layer that may give rise to high friction.…”

“…Though ellipsometry and amino acid analysis have shown (So¨nju and Glantz 1975;Vassilakos et al 1992;Lindh et al 2001) that the material that adsorbs from saliva to surfaces can be markedly dependent on the surface chemistry of the substratum, there is a growing body of evidence that, at least under ex vivo conditions, material adsorbs from saliva to form an asymmetric two-layer structure (Vassilakos et al 1992(Vassilakos et al , 1993Ca´rdenas et al 2007a;Macakova et al 2010;Santos et al 2010). This structure comprises a tightly-bound lower layer encompassing low molecular weight proteins and a highly diffuse and hydrated upper layer encompassing high molecular weight glycoproteins.…”

“…The adsorbed structure of material adsorbed from saliva has been studied using electron microscopy (Lie 1975(Lie , 1977Hannig 1999) and has established certain features of in vivo pellicle, such as a rough globular structure (Rølla and Rykke 1994) but this varies somewhat from ex vivo work performed using neutron reflectometry, quartz crystal microbalance with dissipation monitoring ('QCM-D') and AFM that suggest thinner, smoother layers form ex vivo (Ca´rdenas et al 2007a(Ca´rdenas et al , 2007bMacakova et al 2010). Though ellipsometry and amino acid analysis have shown (So¨nju and Glantz 1975;Vassilakos et al 1992;Lindh et al 2001) that the material that adsorbs from saliva to surfaces can be markedly dependent on the surface chemistry of the substratum, there is a growing body of evidence that, at least under ex vivo conditions, material adsorbs from saliva to form an asymmetric two-layer structure (Vassilakos et al 1992(Vassilakos et al , 1993Ca´rdenas et al 2007a;Macakova et al 2010;Santos et al 2010).…”