Interactions of chlorhexidine with salivary films adsorbed at solid/liquid and air/liquid interfaces

Chlorhexidine is a cationic compound which has been shown to bind to salivary proteins and enamel through electrostatic interactions. The aims of this study were to investigate the interaction of chlorhexidine molecules with salivary films absorbed on solid surfaces with varying physico-chemical characteristics and to investigate the effect of different concentrations of chlorhexidine on the surface tension of saliva. The interactions between 0.2% chlorhexidine digluconate with films adsorbed from whole saliva were monitored by a Rudolph Thin-film ellipsometer equipped with a He-Ne laser (632.8 nm). The films were adsorbed on hydrophilic silica surfaces which were plasma cleaned or on methylated hydrophobic surfaces. Experiments of chlorhexidine adsorption on bare surfaces were also performed. The surface tension of mixtures of whole saliva with various concentrations of (0.1%, 0.2%, 1%) chlorhexidine was monitored with a tensiometer. The results show that chlorhexidine adsorbs on both types of studied substrates. Addition of the substance followed by rinsing caused a partial desorption of the adsorbed pellicles. Furthermore, at all studied concentrations chlorhexidine reduced the interfacial tension. There are indications that the amphiphilic characteristics of the molecule play an important role in the retention of the substance in the oral cavity.     

The deposition of oral bacteria at the solid/liquid and solid/liguid/air interfaces.

A technique for quantifying the deposition of microorganisms at the solid/liquid and solid/liquid/air interfaces enabled the deposition characteristics of representative strains of five oral species on glass from saline and saliva to be compared using single and mixed bacterial suspensions. The deposited bacteria were quantified microscopically and by viable counts. All the strains attached to the glass surfaces. Streptococcus sanguis NCTC 7868, Actinomyces viscosus WVU 371, and Streptococcus mutans NCTC 10449 generally attached or deposited more readily from saliva than Streptococcus salivarius NCTC 7366 or Lactobacillus casei L 8822 due perhaps to polymers on their cell surfaces forming bridges to the saliva-covered glass surfaces. The findings show that the quantity of deposited material cannot be correlated directly with its content of viable bacteria.     

Initial studies on the behavior of salivary proteins at liquid/air interfaces.

The mode of adsorption of salivary proteins at air/liquid interfaces was studied by using the drop volume technique to measure the kinetics of surface tension decay of aqueous salivary solutions. Adsorption of salivary proteins from whole saliva was fast, with a plateau value of the surface tension of 43 (+/- 2) mNm-1. As the concentration of saliva was reduced, the plateau value of surface tension increased and was achieved more slowly. The reduction in surface tension of aqueous solutions was larger for salivary proteins than for many other proteins reported.     

An in vitro study of salivary film formation at solid/liquid interfaces

The aim of this study was to use the technique of in situ null ellipsometry to study some aspects of salivary film formation at solid/liquid interfaces. Experiments were performed in a fused quartz cell, and hydrophilic plasma cleaned silica and methylated hydrophobic silica surfaces were used as substrates. Samples of unstimulated whole saliva were allowed to adsorb on the test surfaces for 30 min. After the adsorption period, rinsing was performed for 5 min. Recordings were continued for another 30 min, and then new saliva samples were added in the cell. The results showed that statistically significant higher amounts were adsorbed on the hydrophobic than on the hydrophilic surfaces. The adsorbed films on both types of tested substrates consisted of loosely associated parts which were removed after rinsing and of more tightly adsorbed fractions. A significantly larger fraction was desorbed from the films adsorbed on the hydrophobic than on the hydrophilic surfaces. When saliva was introduced again in the cell, it was shown that the amounts adsorbed attained the values obtained before the rinsings. Increase in the concentration of saliva in the cell without previous rinsing did not cause any further increase in the mass of the adsorbed film.     

On the adsorption behaviour of saliva and purified salivary proteins at solid/liquid interfaces

Salivary proteinaceous substances are known to play important roles in the formation of the salivary pellicle. The aim of this study was to investigate some aspects of the interfacial behaviour of selected purified salivary proteins, as well as human saliva secretions, using time-resolved in situ ellipsometry. Hydrophobic methylated silica and hydrophilic pure silica were used as test substrates. Experiments were performed in vitro, preferentially in the low concentration range, with samples of fresh human whole resting saliva, parotid resting saliva and submandibular/sublingual resting saliva. The protein fractions investigated were human MUC5B, PRP-1, PRP-3 and statherin, as well as bovine submaxillary mucin (BSM). The results indicate that the amount of material adsorbed was strongly related to the protein concentration in the range investigated for both pure proteins and secretions. Generally, a larger amount of material was adsorbed onto hydrophobic surfaces than onto hydrophilic ones. However, pure PRP-1 adsorbed in similar amounts to both hydrophilic and hydrophobic surfaces in the concentration range investigated and BSM adsorbed in larger amounts at high concentrations on hydrophilic surfaces. Comparison of the observed adsorption rates for salivary secretions and calculated diffusion rates for individual proteins suggested initial adsorption of low-molecular-weight proteins/peptides. On hydrophilic surfaces the data indicate adsorption of proteins with diffusion rates corresponding to those of statherin, PRP-3 and PRP-1. MUC5B adsorbs at a later stage from both HWS and the individual secretions, which can be explained by a "Vroman effect"-like phenomenon. On hydrophobic surfaces, adsorption rates were found to be faster than those calculated for any of the proteins, and thus smaller proteins/peptides appear to be involved. The similar adsorption behaviour of PRP-1 and parotid saliva (HPS) on hydrophilic surfaces may suggest that long aPRPs account for a substantial portion of the film-forming capacity of HPS. Effects of added electrolyte could be explained by general screening effects and specific Ca2+ binding to serine phosphates in aqueous solutions, but were complex in phosphate buffer. Inter-individual differences in amounts adsorbed from HWS, HPS and HSMSLS, respectively, were not found to be statistically significant.     

In vitro interactions of anionic and cationic surfactants with salivary fractions on well-defined solid surfaces.

Ellipsometry was used to study the interaction of one anionic (SDS) and one cationic (CTAB) surfactant with films adsorbed from six different salivary fractions obtained after fractionation of whole unstimulated saliva on a Superdex 200 Hiload gel filtration column. Experiments were performed on both hydrophilic silica and hydrophobic methylated silica surfaces. The results of this study indicate that the adhesive and cohesive properties of the films adsorbed from the individual fractions were strongly dependent on the surface characteristics of the substrates and that the outcome of protein/surfactant interactions was dependent on factors such as protein composition, surfactant charge, and substrate characteristics. These interactions probably involve replacement of the adsorbed proteins by surfactants or protein/surfactant complex formation. The anionic surfactant seemed to be more efficient in removing adsorbed salivary proteins than the cationic one.     

Voltammetry for surface-active ions at polarisable liquid|liquid interfaces

Adsorption of charged species at the interface between two immiscible electrolyte solutions (ITIES) is simulated taking into account both the mutual influence between the potential dependent surface excess charge and the potential distribution between the two phases and the partition equilibrium of the surface-active molecules. The electrical potential profiles are calculated assuming a single adsorption plane separating two electrical diffuse layers following the modified Verwey–Niessen model (MVN). The interfacial boundary potential is obtained from the electroneutrality condition. The interplay between adsorption and partition under steady-state conditions is addressed yielding voltammetric responses for the adsorption–desorption processes along with the faradaic response.     

Adsorption of salivary proteins and serum proteins to titanium.

Titanium (Ti) is very effective as a dental implant material owing to its low toxicity and high biocompatibility. I carried out in vitro experiments on the adsorption of salivary proteins and serum proteins to Ti to better understand how this material reacts in the oral cavity. I found that when Ti that had adsorbed serum proteins was exposed to salivary proteins, there was an exchange of the proteins on the Ti surface. The same thing happened when Ti that had adsorbed salivary proteins was exposed to serum proteins. These results suggest that both human salivary proteins and serum proteins adsorb to Ti with different affinity, and that protein already adsorbed to Ti might mask binding sites for other proteins.     

Adsorption of human salivary proteins to hydroxyapatite: a comparison between whole saliva and glandular salivary secretions.

The protein compositions of in vitro pellicles formed from whole saliva and parotid and submandibular secretions were determined by use of synthetic hydroxyapatite as a model for dental enamel. The adsorbed and unadsorbed protein fractions were analyzed by amino acid analysis and both anionic and cationic discontinuous polyacrylamide gel electrophoresis. For further characterization of the in vitro pellicle, the adsorbed fractions were subjected to gel filtration on Sephadex G-100 and reversed-phase chromatography on C18 columns. Amylase, acidic and glycosylated proline-rich proteins, statherins, and histatins were identified in the parotid-derived pellicle. Detailed analysis of the statherin-containing fractions resulted in the observation of several statherin-like proteins. The use of cationic gel electrophoresis allowed for the identification of histatin 3 and histatin 5, which have not been previously detected in pellicle formed in vitro. The protein composition of submandibular-derived pellicle was similar to that of parotid-derived pellicle except for the presence of cystatins and the absence of glycosylated proline-rich proteins. In contrast, in vitro pellicle derived from whole saliva exhibited a vastly different composition, consisting primarily of amylase, acidic proline-rich proteins, cystatins, and proteolytically-derived peptides. The results indicate that acidic phosphoproteins as well as neutral and basic histatins from pure secretions selectively adsorb to hydroxyapatite, whereas in whole saliva some of these proteins are proteolytically degraded, dramatically changing its adsorption pattern.     

人唾液α-淀粉酶与红/绿茶多酚相互作用的吸附动力学研究

目的 探索茶黄素(TF)和表没食子儿茶素没食子酸酯(EGCG)与人唾液α-淀粉酶(HSA)反应所引起的口腔收敛性感觉的驱动力.方法利用表面等离子共振仪CSPR)和吸附动力学原理,测量Langmuir、Freundlich吸附等温线常数(K<,L>、K<,t>和M<,m>)和吸附反应速率及平衡常数(K<,a>、K<,d>...     

Gel phase formation at resin-modified glass-ionomer/tooth interfaces

Ionic bonding between polyalkenoic acid and hydroxyapatite may explain the excellent bonding retention of glass-ionomers in clinical trials. We have here investigated the extent to which the self-adhesiveness of resin-modified glass-ionomers (RMGIs) can be attributed to this chemical bonding capacity. Therefore, the interaction of 3 RMGIs with tooth substrates was comprehensively characterized, with electron and atomic force microscopy correlated with x-ray photoelectron spectroscopy (XPS). Interfacial ultrastructural analysis for 2 RMGIs disclosed a shallow hybridization of hydroxyapatite-coated collagen, on which a submicron gel phase was deposited through reaction of the polyalkenoic acid with calcium extracted from the dentin surface. One RMGI, however, bonded to dentin without hybrid layer or gel phase formation. XPS indicated that polycarboxylic acids included in the RMGIs electrostatically interacted with hydroxyapatite. We conclude that the self-adhesiveness of RMGIs should be attributed to ionic bonding to hydroxyapatite around collagen, and to micro-mechanical interlocking for those RMGIs that additionally hybridize dentin.     

Micromechanics of implant/tissue interfaces.

A series of finite element models was developed for evaluation of the micromechanics of implant/tissue interfaces. Conventional finite element global models of a dental implant, assuming a continuum implant/bone interface, were developed so that general stress patterns in the implant and surrounding tissue could be obtained. Stresses in bone were concentrated on the alveolar crest and apex region for all global models having a direct bone/implant contact. The addition of a 100-microns-thick layer of fibrous tissue into the bone/implant interface concentrated the stresses in the middle third of the bone adjacent to the implant surface. Stresses in the middle third were ten times higher than in the cases without fibrous tissue. Interfaces modeled under the assumption of a volume-weighted average material stiffness of bone tissue and metal confirmed these general stress patterns, but provided no stress details of the interfacial zone. Finally, the equivalent material constants of the interfacial zone with and without fibrous tissue were calculated by homogenization theory. From these equivalent constants, local strains around single threads were calculated. These equivalent material properties are sensitive to the microstructure. Therefore, it is now possible for stress patterns within the interfacial zone to be quantified and the local micromechanical behavior around individual surface structures for whole implants accounted for.     

Adsorption of two human parotid salivary macromolecules on hydroxy-, fluorhydroxy- and fluorapatites.

The adsorption isotherms (37 °C) for a tyrosine-rich peptide (statherin, mol. wt 5380) and a proline-rich protein (PRP-3, mol. wt 11,320), both isolated from human parotid saliva, were obtained by using hydroxyapatite, fluorapatite and two fluorhydroxyapatites containing 0.49 and 1.55 per cent fluoride, respectively, as adsorbents. An adsorption model based on the Langmuir isotherm adequately fitted the experimental data. The adsorption affinity of PRP-3 for the adsorbents tested was considerably higher than the affinity of statherin for these adsorbents. The reverse was true for the maximum number of adsorption sites. The adsorption affinities increased substantially with increased fluoride content in the crystalline lattice of the apatites, whereas only modest increases in the maximum number of sites were obtained. This behaviour is ascribed to a reduction in the surface free energy of the adsorbent with a concomitant decrease of the interaction with water and, as a consequence, an enhanced adsorption bond (presumably electrostatic) between the macromolecule and the adsorbent. As the relative increases in the adsorption affinities with increasing fluoride content of the adsorbents for the two macromolecules were markedly different, it is hypothesized that the composition of the acquired tooth pellicle may be different in fluoridated and non-fluoridated areas. This difference may be of significance in relation to the cariostatic effect of fluoride.     

Fibrinolytic activity of salivary euglobulin fractions precipitated at pH 5.9 or 6.4 before and after mixing with blood

Mixed saliva was collected from 20 healthy young persons before oral surgery, immediately after the operation and at control 5 days later. The fibrinolytic activity of untreated whole saliva and salivary euglobulin fractions precipitated at pH 5.9 (10 patients) or at pH 6.4 (10 patients) was measured on human fibrin plates. The salivary euglobulin fractions were also processed on plasminogen-free fibrin plates. The concentrations of alpha 1-antitrypsin, antithrombin III, C1-esterase inhibitor, alpha 2-macroglobulin, alpha 2-plasmin inhibitor and plasminogen were measured in pooled plasma and four postoperative saliva samples before and after preparing the corresponding dissolved euglobulins precipitated at pH 5.9 or pH 6.4. Dissolved euglobulins from the pooled plasma were subjected to crossed immunoelectrophoresis with antisera to plasminogen in the second-dimension gel. Normal mixed saliva showed unaltered fibrinolytic activity after euglobulin precipitation, whereas euglobulins prepared from postoperative samples had higher activity than the untreated specimens. No significant differences of fibrinolytic activity between salivary euglobulins precipitated at pH 5.9 and 6.4 were demonstrated. The recovery of proteinase inhibitors in the euglobulin fractions of plasma is lower than 2.1% except C1-esterase inhibitor, which is precipitated, but only at pH 5.9. The mixing with saliva does not seem to change this relative quantity of precipitated inhibitors from plasma. Plasminogen precipitated from plasma is not proteolytic degraded and the yield is higher at pH 5.9 than at pH 6.4. Salivary euglobulins precipitated at pH 5.9 or 6.4 are superior to untreated saliva to measure the fibrinolytic activity of mixed saliva, especially in samples contaminated with blood.     

Surface reconstruction at metal|solid polymer electrolyte interfaces: Au(111)|Nafion? interface1

The structure of the Au(111) surface in contact with a recast Nafion® film has been studied as a function of potential by using grazing incident angle X-ray diffraction. The high penetration depth of X-ray makes it possible to probe the electrode surface covered by a 1 to 3 μm thick Nafion® film. The Nafion®-coated Au(111) electrode surface is not reconstructed at open circuit potential. However, the $\text{(23×}\text{3}\text{)}$ reconstruction can be generated at sufficiently negative potentials. In comparison with the Au(111) electrode in NaClO₄ solution, the lifting of reconstruction is shifted positively by about 0.2 V. This fact supports the view of the primary effect of surface charge on the Au(111) reconstruction lifting. Adding chloride to the solution shifts the phase transition potential negatively after several hours, indicating a moderate ion permselectivity of the Nafion® film in NaCl solution. These results demonstrate that the Nafion® coating is stable over a large potential range and is suitable for studying surface properties and the effects of ion distribution on surface electrochemical processes at single crystal surfaces. © 1997 Elsevier Science S.A.     

Adsorption from black tea and red wine onto in vitro salivary pellicles studied by ellipsometry

The adsorption of black tea and red wine components onto a pellicle-like protein layer formed in vitro by adsorption from whole unstimulated saliva on hydroxyapatite discs were studied by in situ ellipsometry. It was found that components from black tea readily adsorbed to the pellicle. Subsequent exposure to saliva led to further adsorption of salivary components to give an overall increase in the amounts adsorbed. The amounts adsorbed increased still further following a third tea and saliva exposure. Components of red wine gave significantly greater amounts of adsorption to the pellicle than black tea. The adsorption of components of black tea gave a concomitant increase in colour or stain as measured by a reflectance chromameter. In all cases, the black tea- and red wine-modified pellicles were not eluted by either phosphate buffer or sodium dodecyl sulphate (SDS) rinses. Thus, black tea and red wine components have been shown to have a profound effect on in vitro pellicle maturation, causing thickened layers of stained material to build up, which are not readily removed.