Concentration dependence of adsorption from human whole resting saliva at solid/liquid interfaces: An ellipsometric study

Abstract

The rates and plateau values of adsorption at the solid/ liquid interface from human whole resting saliva from three male donors were studied in vitro. The influence of saliva concentration, the total protein content and the wettability of the exposed solids was investigated. Ellipsometry was used to study the rate and plateau values of the adsorption process in situ. The solid surfaces used were hydrophilic, negatively charged, silica and hydrophobic methylated silica. Salivary films were formed by adsorption from solutions of 0.05%, 0.10%, 0.20%, 0.50%, 1.0% and 2.0% (v/v) saliva in phosphate buffered saline. The results revealed that adsorption onto both types of surfaces was a rapid and, as expected, a concentration dependent process. The adsorbed amounts were in the range of monomolecular layers and were found to be larger onto the hydrophobic than the hydrophilic surfaces (p 0.0062). A strong concentration dependence was denoted in all cases (p< 0.0001). Inter-individual differences were found not to be significant (0.0636 p 0.8508) at any of the saliva concentrations. However, an interaction was shown (p < 0.0001) between the protein concentrations and the donors, indicating qualitative differences in protein content and surface activity.

Adsorption behaviour and surfactant elution of cationic salivary proteins at solid/liquid interfaces, studied by in situ ellipsometry

“…On hydrophilic silica surfaces the steep slopes of the isotherms and the high adsorbed amounts of the investigated proteins (correlating to side-on and end-on monolayer at concentrations relevant in saliva) suggests that these proteins have strong driving forces for adsorption, comparable to those observed for salivary secretions [14,33,34,38] and single key-pellicle proteins [41,48].…”

“…To obtain hydrophilic and hydrophobized (methylated) silica surfaces, the surfaces were treated as previously described [33][34][35]. Before use, substrates were rinsed with water, ethanol and water and the hydrophilic surfaces were also plasma cleaned in a Harrick Plasma Cleaner PDC-32G (Harrick Scientific Corporation, Ossining, NY, USA).…”

Lactoperoxidase and Histatin 5 – their Adsorption Behaviour on Silica and Hydrophobized Silica Surfaces, and Implications on their Role in the Initial Salivary Film Formation

“…A more correct value would be the hydrodynamic radius, which would be expected to be slightly larger than the estimated R g . Mass transport controlled adsorption rates of lactoperoxidase and histatin 5 were calculated and compared to the initial adsorption of HWS [15], HPS [16], HSMSLS [16], and HPalS [17]. The model of Trurnit was applied for the mass transport controlled adsorption calculations [20].…”

“…To obtain hydrophilic and methylated (hydrophobized) silica surfaces, the surfaces were treated as previously described [15,17,23]. Before use, substrates were rinsed with water, ethanol and water and the hydrophilic surfaces were also plasma cleaned (Harrick Plasma Cleaner PDC-32G, Harrick Scientific Corporation, Ossining, NY, USA).…”

“…To investigate the influence of surface wettability on the adsorption process, two different substrates were used for the adsorption experiments, pure (hydrophilic) and methylated (hydrophobized) silica surfaces. Further, the theoretical mass transport controlled adsorption of lactoperoxidase and histatin 5 were compared to the initial adsorption kinetics of human whole saliva (HWS) [15] and glandular saliva (human parotid saliva (HPS) [16], human submandibular/sublingual saliva (HSMSLS) [16] and human palatal saliva (HPalS) [17]), to investigate the possible importance of these proteins in the initial adsorption from these secretions. HPS is known to be a watery secretion, containing high amounts of small salivary proteins such as proline-rich proteins (PRPs) and amylase.…”