| 1. |
- Andoralov, Viktor, et al.
(author)
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Flexible micro(bio)sensors for quantitative analysis of bioanalytes in a nanovolume of human lachrymal liquid
- 2013
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In: Analytical and Bioanalytical Chemistry. - : Springer. - 1618-2642 .- 1618-2650. ; 405:11, s. 3871-3879
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Journal article (peer-reviewed)abstract
- A flexible electrochemical micro(bio)sensor has been designed for determination of several biological compounds, specifically, ascorbate, dopamine, and glucose, in human lachrymal liquid (tears). The microsensor for simultaneous determination of ascorbate and dopamine concentrations was based on a gold microwire modified with the tetrathiafulvalen–7,7,8,8-tetracyanoquinodimethane complex as a catalyst. To monitor glucose concentration in tears, glucose dehydrogenase was immobilized on a gold microwire modified with carbon nanotubes and an osmium redox polymer. A capillary microcell was constructed for sampling tears. The cell had a working volume of 60–100 nL with a sampling deviation of 6.7 %. To check if the microcell was properly filled with buffer or tear sample, a control electrode was introduced into the construction. The electrode was used to measure the electrical resistance of a fully filled nanovolume cell. The mechanical flexibility is one of the most important features of the prototype and allowed direct collection of tears with minimized risk of damage to the eye.
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| 2. |
- Arnebrant, Thomas, et al.
(author)
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Adsorption of chlorhexidine and black tea onto in vitro salivary pellicles, as studied by ellipsometry
- 2006
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In: European Journal of Oral Sciences. - : Wiley. - 0909-8836 .- 1600-0722. ; 114, s. 337-342
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Journal article (peer-reviewed)abstract
- The adsorption from 0.2% (w/w) chlorhexidine and black tea solutions onto an in vitro pellicle from whole unstimulated saliva on hydroxyapatite discs was studied by ellipsometry. It was found that chlorhexidine adsorbed to the pellicle causing a modification of the pellicle properties, leading to a subsequent increase in adsorption of salivary and black tea components. There was a distinct order of addition effect, whereby chlorhexidine followed by black tea gave an overall greater adsorption of components compared to black tea followed by chlorhexidine. This increase in adsorption gave a concomitant increase in colour or stain as measured by a reflectance chromameter. The increase in adsorbed amounts and stain was modified in part by the adsorption of salivary fractions between the chlorhexidine and black tea treatments. In all cases, the chlorhexidine and black tea modified pellicles were not readily removed by either phosphate or sodium dodecyl sulphate rinses. Thus, following chlorhexidine exposure, the accelerated adsorption of salivary and black tea components can ultimately lead to increased staining of the pellicle.
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| 3. |
- Arnebrant, Thomas, et al.
(author)
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Lubricating Properties of the Initial Salivary Pellicle
- 2003
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In: Biofouling (Print). - : Harwood Academic Publishers. - 0892-7014 .- 1029-2454. ; 19:6, s. 365-369
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Journal article (peer-reviewed)abstract
- The role of saliva in the oral cavity is manifold; an important function is to serve as lubricant between hard (enamel) and soft (mucosal) tissues. Intraoral lubrication is of crucial importance in order to maintain functions such as deglutition, mastication and the faculty of speech. A large number of people suffer from impaired salivary functions, displaying symptoms such as 'dry mouth'. This results in a need for methods to assess the lubricating properties of both native saliva and potential artificial saliva formulations. Here, normal as well as lateral forces, acting between adsorbed salivary films, have been measured for the first time by means of colloidal probe atomic force microscopy (AFM). It was found that the presence of salivary pellicles between hard surfaces reduces the friction coefficient by a factor of 20. This reduction of friction is consistent with the long-range purely repulsive nature of the normal forces acting between the salivary films. The lubricating mechanism is presumably based on a full separation of the sliding surfaces by the salivary films. The friction between salivary films has been investigated at normal loads that cover the clinical jaw closing forces, and it can be concluded that the lubricating properties are maintained within this load interval. The present study indicates the usefulness of colloidal probe AFM, which offers a direct and quantitative measure of lubrication at a molecular level, in the study of biotribological phenomena. In particular, the results obtained here may have implications for the development of saliva substitutes.
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| 4. |
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| 5. |
- Aroonsang, Watcharapong, et al.
(author)
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Influence of substratum hydrophobicity on salivary pellicles : organization or composition?
- 2014
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In: Biofouling (Print). - : Taylor & Francis. - 0892-7014 .- 1029-2454. ; 30:9, s. 1123-1132
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Journal article (peer-reviewed)abstract
- Different physico-chemical properties (eg adsorption kinetics, thickness, viscoelasticity, and mechanical stability) of adsorbed salivary pellicles depend on different factors, including the properties (eg charge, roughness, wettability, and surface chemistry) of the substratum. Whether these differences in the physico-chemical properties are a result of differences in the composition or in the organization of the pellicles is not known. In this work, the influence of substratum wettability on the composition of the pellicle was studied. For this purpose, pellicles eluted from substrata of different but well-characterized wettabilities were examined by means of sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS-PAGE). The results showed that substratum hydrophobicity did not have a major impact on pellicle composition. In all substrata, the major pellicle components were found to be cystatins, amylases and large glycoproteins, presumably mucins. In turn, interpretation of previously reported data based on the present results suggests that variations in substratum wettability mostly affect the organization of the pellicle components.
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| 6. |
- Barrantes, Alejandro, et al.
(author)
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Characteristics of saliva films adsorbed onto different dental materials studied by QCM-D
- 2014
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In: Colloids and Surfaces A. - : Elsevier. - 0927-7757 .- 1873-4359. ; 442:Special issue: Selected papers from the 26th European Colloid and Interface Society conference (26th ECIS 2012), s. 56-62
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Journal article (peer-reviewed)abstract
- The formation of salivary films onto different surfaces relevant in dental research like titania, hydroxyapatite, gold, zirconia, silica, and hydrophobized silica has been studied by means of QCM-D. Human whole saliva (HWS), and sterile filtered HWS (sHWS) both diluted in water to a final concentration of 25% (v/v) were used. Main differences between the salivary films formed from the two saliva types were observed with the help of ΔD vs Δf plots where sHWS samples showed an almost linear adsorption regime for most of the surfaces whereas most of the HWS samples had a marked multi-regime nature indicating that the former ones are homogenous and the later are heterogeneous supporting previous data on a multi-phase adsorption process. The films with highest shear elastic modulus, μ > 105 N m−2, shear viscosity, η ∼ 3 × 10−3 N s m−2, and lowest thickness (∼10 nm) were formed for both types of saliva onto hydroxyapatite and for sHWS on titania. Furthermore, the ratio between the loss, G″, and the storage modulus, G′, indicates that these films have a solid-like behavior (G″/G′ ≤ 0.5). In contrast, for the remaining surfaces the adsorbed films show higher d values and are also characterized by low μ ∼ 104 N m−2, η ∼ 10−3 N s m−2, and by high ratios, G″/G′ > 2, that indicate a fluid like behavior. These observations might be expected to have influence on the lubricating properties of the salivary films. The SDS induced elutability also indicates a different interaction strength and composition of the adsorbed films and is likely associated with the ease by which these surfaces can be cleaned. Our results suggest that, among the relevant materials, zirconia and titania would yield the more lubricious films whereas hydroxyapatite will be the most easily cleaned.
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| 7. |
- Barrantes, Alejandro, et al.
(author)
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Influence of pH on the build-up of poly-L-lysine/heparin multilayers
- 2012
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In: Journal of Colloid and Interface Science. - : Elsevier. - 0021-9797 .- 1095-7103. ; 388:1, s. 191-200
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Journal article (peer-reviewed)abstract
- The effect of pH on the build-up-of polyelectrolyte multilayers, PEMs, composed by poly-L-lysine and heparin onto two different substrates, silica and gold, has been studied by means of ellispmetry and quartz crystal microbalance with dissipation, QCM-D. Ellipsometry results indicate that the dry mass grows exponentially with the number of layers, and that this amount is larger as the pH values are raised. From QCM-D data the viscoelastic properties of the multilayered structure have been obtained. These data reflect that PEMs become more viscoelastic as the pH values are increased for silica substrates, while for gold the highest viscoelastic behavior is obtained at neutral pH and the elastic behavior becomes dominant as the pH is further increased or decreased. By combining these two surface techniques it has been also possible to determine the solvent content in the multilayers and reach a deeper understanding of the internal structure.
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| 8. |
- Barrantes, Alejandro, et al.
(author)
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Poly-L-lysine/heparin multilayer coatings prevent blood protein adsorption
- 2017
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In: Journal of Colloid and Interface Science. - : Elsevier. - 0021-9797 .- 1095-7103. ; 485, s. 288-295
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Journal article (peer-reviewed)abstract
- The adsorption of blood proteins, serum albumin (BSA), immunoglobulin G (IgG) and fibrinogen (FGN), onto model SiO2 planar surfaces coated with poly-L-lysine/heparin multilayers (PLL/HEP) has been investigated by means of ellipsometry and quartz crystal microbalance with dissipation. Aiming at the development of low fouling coatings, this study has been focused on the effects that the number of layers and the type of polyelectrolyte present on the topmost layer have on the adsorption of these proteins. The three proteins interact with PLL-ended coatings whereas HEP-ended coatings prevent the adsorption of both BSA and IgG and induce a decrease in the adsorbed amount of FGN, down to 0.4 mg/m(2) for three bilayers, as the number of PLL/HEP bilayers increases. These results suggest that heparin-ended multilayers prevent protein adsorption, which is an indicative of good blood compatibility. As a consequence we propose that PLL/HEP coatings could be used for the development of vascular medical devices. (C) 2016 Elsevier Inc. All rights reserved.
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| 9. |
- Boyd, Hannah, 1994-, et al.
(author)
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A comparison between the structures of reconstituted salivary pellicles and oral mucin (MUC5B) films.
- 2021
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In: Journal of Colloid and Interface Science. - : Elsevier. - 0021-9797 .- 1095-7103. ; 584, s. 660-668
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Journal article (peer-reviewed)abstract
- HYPOTHESIS: Salivary pellicles i.e., thin films formed upon selective adsorption of saliva, protect oral surfaces against chemical and mechanical insults. Pellicles are also excellent aqueous lubricants. It is generally accepted that reconstituted pellicles have a two-layer structure, where the outer layer is mainly composed of MUC5B mucins. We hypothesized that by comparing the effect of ionic strength on reconstituted pellicles and MUC5B films we could gain further insight into the pellicle structure.EXPERIMENTS: Salivary pellicles and MUC5B films reconstituted on solid surfaces were investigated at different ionic strengths by Force Spectroscopy, Quartz Crystal Microbalance with Dissipation, Null Ellipsometry and Neutron Reflectometry.FINDINGS: Our results support the two-layer structure for reconstituted salivary pellicles. The outer layer swelled when ionic strength decreased, indicating a weak polyelectrolyte behavior. While initially the MUC5B films exhibited a similar tendency, this was followed by a drastic collapse indicating an interaction between exposed hydrophobic domains. This suggests that mucins in the pellicle outer layer form complexes with other salivary components that prevent this interaction. Lowering ionic strength below physiological values also led to a partial removal of the pellicle inner layer. Overall, our results highlight the importance that the interactions of mucins with other pellicle components play on their structure.
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| 10. |
- Boyd, Hannah, 1994-, et al.
(author)
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Effect of nonionic and amphoteric surfactants on salivary pellicles reconstituted in vitro
- 2021
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In: Scientific Reports. - : Nature Publishing Group. - 2045-2322. ; 11:1
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Journal article (peer-reviewed)abstract
- Surfactants are important components of oral care products. Sodium dodecyl sulfate (SDS) is the most common because of its foaming properties, taste and low cost. However, the use of ionic surfactants, especially SDS, is related to several oral mucosa conditions. Thus, there is a high interest in using non-ionic and amphoteric surfactants as they are less irritant. To better understand the performance of these surfactants in oral care products, we investigated their interaction with salivary pellicles i.e., the proteinaceous films that cover surfaces exposed to saliva. Specifically, we focused on pentaethylene glycol monododecyl ether (C12E5) and cocamidopropyl betaine (CAPB) as model nonionic and amphoteric surfactants respectively, and investigated their interaction with reconstituted salivary pellicles with various surface techniques: Quartz Crystal Microbalance with Dissipation, Ellipsometry, Force Spectroscopy and Neutron Reflectometry. Both C12E5 and CAPB were gentler on pellicles than SDS, removing a lower amount. However, their interaction with pellicles differed. Our work indicates that CAPB would mainly interact with the mucin components of pellicles, leading to collapse and dehydration. In contrast, exposure to C12E5 had a minimal effect on the pellicles, mainly resulting in the replacement/solubilisation of some of the components anchoring pellicles to their substrate.
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