Biomedical subjects

T Arnebrant

Publications and source records attributed to T Arnebrant.

At least 19 recordsLinked to original sources

PubMed2005

Ellipsometric characterization of ethylene oxide-butylene oxide diblock copolymer adsorption at the air-water interface.

Ellipsometry was used to determine the adsorbed layer thickness (d) and the surface excess (adsorbed amount, Gamma) of a nonionic diblock copolymer, E(106)B(16), of poly(ethylene oxide) (E) and poly(butylene oxide) (B) at the air-water interface. The results were obtained (i) by the conventional ellipsometric evaluation procedure using the change of both ellipsometric angles Psi and Delta and (ii) by using the change of Delta only and assuming values of the layer thickness. It was demonstrated that the calculated surface excesses from the different methods were in close agreement, independent of the evaluation procedure, with a plateau adsorption of about 2.5 mg/m(2) (400 A(2)/molecule). Furthermore, the amount of E(106)B(16) adsorbed at the air-water interface was found to be almost identical to that adsorbed from aqueous solution onto a hydrophobic solid surface. In addition, the possibility to use combined measurements with H(2)O or D(2)O as substrates to calculate values of d and Gamma was investigated and discussed. We also briefly discuss within which limits the Gibbs equation can be used to determine the surface excess of polydisperse block copolymers.

Journal Article↗

PubMed2001

Interactions between Local Anaesthetic Agents and Poly(N-isopropyl acrylamide) through Phase Behavior, Surface Tension, and Adsorption Measurement.

The interaction between the local anaesthetic agents prilocaine and lidocaine, on one hand, and poly(N-isopropyl acrylamide) (pNIPAM), on the other, is investigated through studies of the polymer phase behavior and through surface tension and adsorption measurements. In particular, the cloud points (CP) for pNIPAM in the presence of lidocaine and prilocaine under different conditions were compared to the effects of electrolytes and alcohols. It was found that the electrolytes affect the CP of pNIPAM in a lyotropic manner, whereas alcohols depress the CP of pNIPAM in an alkyl chain length dependent way; i.e., the longer the chain, the larger the decrease in CP. Lidocaine and prilocaine affect the CP of pNIPAM in a pH-dependent manner. Below the pK(a) of lidocaine and prilocaine, these cosolutes do not substantially affect the CP in the concentration range investigated, but rather behave analogous to simpler electrolytes. Above the pK(a), on the other hand, they strongly depress the CP already at low concentrations. In parallel, at low pH, the surface tension reduction due to lidocaine or prilocaine is marginal, whereas at high pH the surface tension is reduced considerably. Thus, the poor solubility of prilocaine and lidocaine at high pH causes these to become more surface active and simultaneously interact in a more pronounced way with pNIPAM. Furthermore, it was found from ellipsometry that an adsorbed pNIPAM layer contracts when lidocaine is added, presumably due to a lidocaine-pNIPAM interaction similar to that causing pNIPAM to phase separate. Analogous to this, it was demonstrated that an adsorbed pNIPAM layer shrinks and swells reversibly when the temperature is cycled above and beneath the CP. Copyright 2001 Academic Press.

Journal Article↗

PubMed2001

Proteolytic degradation of oral biofilms in vitro and in vivo: potential of proteases originating from Euphausia superba for plaque control.

This paper deals with enzymatic removal of dental plaque, in vitro as well as in vivo, using proteases from the Antarctic krill shrimp (Euphausia superba), referred to as Krillase. Krillase exhibits both endo- and exopeptidase activity but has no microbicidal effect. In model systems with pure cultures of oral microorganisms. Krillase demonstrated inhibition of microbial adhesion to saliva-coated hydroxyapatite. Furthermore, a protocol for the growth of reproducible in vitro plaque films has been developed, and effects of Krillase on the plaque film were investigated by means of scanning electron microscopy (SEM). The results showed that Krillase efficiently released microorganisms from plaque in vitro, the effect being dependent on the enzymatic activity. The surface energy of the substratum had a minor influence on the formation and removal of plaque in vitro. Ellipsometric studies on the formation and enzymatic removal of a salivary pellicle indicated that the enzymatic effect on plaque may partly depend on degradation of the salivary pellicle. Krillase was also able to remove plaque accumulated on dentures in vivo. Our results demonstrate the potential of Krillase for plaque control, and that these enzymes are worthy of further investigations including clinical studies and work to find a suitable vehicle.

Actinomyces↗

PubMed2001

Characterization of the binding of delmopinol to salivary precipitates.

The aim of this study was to quantify the amount of delmopinol recovered in different molecular weight ranges of salivary proteins in the supernatant and pellet of delmopinol-saliva mixes. Unstimulated whole saliva was collected from 5 subjects and mixed with radiolabeled delmopinol to obtain a final drug concentration of 9.7 mM. The salivary-delmopinol solutions were incubated and then centrifuged. The resulting pellets and supernatants were studied in an electrophoresis assay. Each individual sample was run in three different electrophoretic gel lanes. The first lane was stained with silver dyes; the second lane was used for electrophoretic blotting and autoradiography; the third lane was cut in standard slices that were dissolved and analyzed with scintillation counting. The scintillation results demonstrated that higher radioactivity levels were detected at high molecular weight ranges (700-600 kDa). Furthermore, pellet samples were found to contain the highest amounts of delmopinol. The autoradiography results confirmed that delmopinol was bound to proteins of high molecular weight (700-600 kDa).

Adult↗

PubMed2000

Film-forming properties and viscosities of saliva substitutes and human whole saliva.

Hypo-salivation, related to medical remedies, is an increasing clinical problem. Studies report a weak correlation between subjective mouth dryness and objective sialometry. This indicates that both quantity and quality of saliva are important for the surface-associated functions of saliva, such as lubrication and hydration, to be expressed. Film-forming properties and viscosities of three saliva substitutes were compared to human saliva. Adsorption to surfaces was measured by ellipsometry, infrared spectroscopy and drop-volume technique. Viscosity measurements were carried out using an oscillating rheometer. Saliva, with the lowest viscosity value and the highest protein content, presented superior film retention on both hydrophilic and hydrophobic surfaces. The carboxymethylcellulose-based MAS 84 showed intermediate values of viscosity, poorest ability to reduce surface tension, and negligible film-forming capacity. The porcine mucin-based Saliva Orthana showed about twice the viscosity of saliva and film-forming capability on preferably hydrophobic substrates. Salinum, a linseed extract, possessed the highest viscosity value and an initial surface tension close to that of saliva. The film retention on hydrophilic surfaces was not as effective as for saliva. The results indicate that the film-forming capacity of saliva substitutes is a property also to be considered in the exploration of clinically effective artificial salivas.

Adsorption↗

PubMed1999

Bioadhesion--a phenomenon with multiple dimensions.

This paper reviews some relevant citations regarding the non-specific forces that must be considered in oral bioadhesive events. These range from forces related to restorative dentistry to those related to prevention and molecular biology. Types of interactions discussed are: 1. Van der Waal's forces; 2. electrostatic double-layer forces; 3. solvent-dependent interactions; 4. hydrogen bonding; 5. hydrophobic interactions; 6. hydration forces; 7. steric forces; and 8. covalent bonds. Examples are given of the various types of interaction that occur at different surface separation (< or =400 A) between adsorbed films of a pure salivary protein fraction (PRP1).

Bacterial Adhesion↗

PubMed1999

The content of delmopinol and characterization of the molecular weight pattern of salivary protein precipitates.

The aims of this investigation were: a) To quantify the amount of radiolabelled delmopinol in precipitates formed in a mixture of saliva and delmopinol at two concentrations, b) To analyze the precipitates by polyacrylamide gel electrophoresis. Unstimulated whole saliva was collected from 5 individuals and the samples were clarified by centrifugation. In a first series of experiments radiolabelled delmopinol hydrochloride at the final concentrations of 1.6 mM and 6.4 mM was incubated with the saliva samples and centrifuged. The supernatants and the pellets were immediately transferred to scintillation vials and radiolabelled delmopinol was detected by using scintillation counting. In a second series of experiments, similar saliva-delmopinol mixtures were centrifuged and the supernatants and pellets were prepared for electrophoresis. Videodensitometry was used to quantify the relative density of stained protein in the pellet samples within four ranges of molecular weight (10-21.5, 21.5-26, 26-45, 45-300 kDa). The results of this study showed that the amounts of labeled delmopinol found in the precipitates were higher at 6.4 mM delmopinol than at 1.6 mM. The amount of salivary protein precipitated by delmopinol was found to depend on delmopinol concentration as well as salivary composition. Delmopinol interactions to salivary proteins could influence protein availability on oral cavity surfaces.

Adult↗

PubMed1998

Delmopinol hydrochloride- and chlorhexidine digluconate-induced precipitation of salivary proteins of different molecular weights.

Gel electrophoresis was used to analyze precipitates formed of delmopinol hydrochloride or chlorhexidine digluconate mixed with unstimulated whole saliva samples from five test subjects. Final concentrations of delmopinol (6.4 mM) or chlorhexidine (6.4 mM, 2.2 mM) mixed with whole saliva were incubated for 10 min at 37 degrees C. The precipitates were pelleted by centrifugation and resuspended to a similar protein density. The protein patterns in the pellets were analyzed by sodium dodecyl sulfate polyacrylamide gel electrophoresis, using 12.3% gels. The amount of pellet protein was determined by densitometry in four molecular weight ranges (10-21.5, 21.5-26, 26-45, and 45-300). The results indicated that high molecular weight (45-300) proteins dominated in the precipitate and that 2.2 mM chlorlhexidine precipitated more salivary protein than 6.4 mM. At equimolar concentration (6.4 mM) delmopinol precipitated more high molecular weight salivary proteins than chlorhexidine.

Adult↗

PubMed1997

Time-dependent interfacial tension of whole saliva and saliva-bacteria mixes.

Using a tensiometer in accordance with the drop volume principle, the surface tension decrease with time was determined for whole and for 2%, 10%, and 50% aqueous solutions of saliva from one healthy donor. The reduction of surface tension with time was also measured for 10% and 20% saliva solutions with added samples of Streptococcus salivarius KRF2, S. sanguis KRF3, and Actinomyces naeslundii 2t-55. The results show that 1) there is a time dependence of the surface tension reduction of both whole saliva and diluted saliva, 2) an increase of the concentration of whole saliva in salivary solutions gives rise to larger and more rapid surface tension reduction, 3) the proteinaceous components of saliva appear to have a dominant contribution on surface tension in whole saliva and diluted saliva, and 4) the surface-active proteinaceous components in saliva have the ability to dominate the air-saliva interface also in the presence of high concentrations of salivary bacteria.

Actinomyces↗

PubMed1996

Adsorption during Heat Treatment Related to the Thermal Unfolding/Aggregation of beta-Lactoglobulins A and B

Adsorption onto chromium surfaces during heat treatment (65-68°C) of beta-lactoglobulin A and B in phosphate buffer, pH 6.88, was investigated by in situ ellipsometry. Thermal unfolding and in situ heat-induced aggregation under the same conditions were studied by differential scanning calorimetry and dynamic light scattering, respectively. A lag phase was observed for buildup of the thickness of the adsorbed layer of beta-lactoglobulin A and B at 68°C. The lag period was found to increase with decreasing temperature. The difference in adsorption rate between the variants was found to be in agreement with the aggregation difference in solution, that is, the A variant aggregated more rapidly after a somewhat slower beginning. These results could be related to a difference in the thermal unfolding behavior. By applying a non-two state model the second of two transitions was suggested to involve the activation of the free sulfydryl group. The results indicated that fouling proceeds via attachment of aggregates with an activated free sulfydryl group through an interchange reaction with a disulfide bond in the adsorbed protein layer.

Journal Article↗

PubMed1993

The binding of delmopinol and chlorhexidine to Streptococcus mutans and Actinobacillus actinomycetemcomitans strains with varying degrees of surface hydrophobicity.

This study evaluated the binding of chlorhexidine and the new surface-active anti-plaque agent delmopinol hydrochloride to Streptococcus mutans and Actinobacillus actinomycetemcomitans cells with various cell surface hydrophobicities. The influence of saliva concentration on the binding of these compounds was also investigated. The radiolabeled compounds were incubated with bacteria and the cells were recovered using a centrifugal filtering technique. Delmopinol had higher binding to the hydrophilic variant strains than to the hydrophobic parent strains; chlorhexidine had higher binding to hydrophobic than to hydrophilic A. actinomycetemcomitans strains and higher binding to hydrophilic than to hydrophobic S. mutans strains. The presence of salivary films decreased the binding of both compounds. Both delmopinol and chlorhexidine had stronger affinity to A. actinomycetemcomitans cells than to S. mutans cells. At equimolar concentrations, delmopinol had a lower binding to all strains tested than chlorhexidine. The high reversibility of the delmopinol binding might be related to a higher diffusion rate and solubility compared with that of chlorhexidine. The amphiphilicity of both molecules is an important feature in their retention to S. mutans and A. actinomycetemcomitans strains of varying hydrophobicities and could play an important role in the substantivity of delmopinol or chlorhexidine in the oral cavity.

Aggregatibacter actinomycetemcomitans↗

PubMed1993

Reflectometry: a new method for quantitative determinations of intraoral film formation.

A simple optical method--reflectometry--is described to determine the thickness and mass of salivary films formed on solid surfaces at oral exposure. Reflectometry is based on the fact that p-polarized light is reflected with minimum intensity at an interface when the angle of incidence equals the so-called pseudo-Brewster angle. Hydrophilic and hydrophobized silica surfaces were used as substrates and the reflectometer was calibrated against a null ellipsometer. A linear relation was found between the square of the ellipsometrically measured thickness of silicon oxides on silicon substrates and the reflectometrically registered intensity of the reflected light at these surfaces. Thirty volunteers participated in the study of the thickness of films formed on the test substrates at oral exposure. The test silica surfaces were positioned in the vestibular sulcus of each test subject for periods of 1, 5, 15, 30, 60, and 120 min. The results show that films formed on hydrophobic surfaces leveled-off to a thickness value of 140 A after 60 min. Films formed on hydrophilic surfaces, however, reached a plateau value of approximately 100 A after only 300 min. Reflectometry seems to be an accurate and valid, yet inexpensive and quick method for quantitative investigations and thickness measurements of early salivary pellicles in large subject groups.

Adsorption↗

PubMed1993

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.

Adsorption↗

PubMed1993

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 adsorbed 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.

Adsorption↗

PubMed1993

In vitro interactions of delmopinol hydrochloride with salivary films adsorbed at solid/liquid interfaces.

Delmopinol hydrochloride is a highly surface active substance which has been shown to reduce the amount of plaque in vitro and in vivo and the level of gingivitis in vivo. Ellipsometry was used to evaluate the effect of delmopinol on films formed from whole, parotid and sublingual/submandibular saliva on solid surfaces. Hydrophilic plasma cleaned silica and methylated hydrophobic substrates were used. The adsorption processes of the salivary proteins and their interactions with delmopinol were monitored in situ with a Rudolph thin-film ellipsometer. The adsorption of delmopinol on bare substrates with out previous salivary adsorption was also investigated and the results indicate that delmopinol molecules were adsorbed on both hydrophilic and hydrophobic surfaces. When delmopinol interacted with the films formed from the different types of saliva an initial increase in the adsorbed amounts was observed in the majority of the cases indicating binding to the salivary pellicles and/or substrate surface. The noted increases were largest for the films adsorbed from whole and sublingual/submandibular saliva. After rinsing in the system, partial desorption of the salivary films took place. It is thus indicated that delmopinol binds to salivary proteins within the pellicles and alters the cohesive and adhesive properties of these films.

Dental Deposits↗

PubMed1992

Adsorption from salivary fractions at solid/liquid and air/liquid interfaces.

Ellipsometry and the drop-volume technique were used to study the interfacial behaviour of fractions obtained from unstimulated whole saliva. Fractionation was by gel filtration on a Superdex 200 Hiload column equilibrated with 10 mM potassium phosphate buffer, pH 6.8, containing 0.15 M NaCl. The fractions were reconstituted to have the same absorbance at 215 nm (estimated molecular-weight range, F1 greater than 760-460 K, F2 205-39 K, F3 14-4.5 K, F4 4.5-2.5 K, F5 1.5-0.85 K, F6 0.85 less than or equal to 0.5 K). The fractions were analysed for amino acid composition and studied by hydrophobic interaction chromatography on a Phenyl-Superose column. Fraction 3 contained the largest amounts of proline, followed by fractions 4 and 2. Fraction 3 showed the highest relative hydrophobicity. Ellipsometric measurements on negatively charged silica surfaces and methylated hydrophobic surfaces revealed that larger amounts of material adsorbed on hydrophobic than on hydrophilic surfaces. On hydrophilic surfaces the largest amounts were adsorbed from the high molecular-weight fraction 1. Fractions 4 and 6 did not give any adsorption at all on these surfaces. Fraction 3 gave the largest amounts adsorbed on the hydrophobic surfaces. Drop-volume measurements showed distinct differences in the ability of the salivary fractions to lower the surface tension. Fractions 2 and 3 showed the greatest reduction in surface tension. It was concluded that the adsorption behaviour of salivary proteins showed a wide variation among the different fractions and that it is influenced by the physicochemical characteristics of the interfaces present in the mouth.

Adsorption↗

PubMed1992

Adsorption of whole saliva onto hydrophilic and hydrophobic solid surfaces: influence of concentration, ionic strength and pH.

The influence of the concentration of salivary proteinaceous material from solutions of whole saliva on the kinetics of in vitro pellicle formation were studied together with the effects of ionic strength, pH and certain substrate characteristics. The pellicle formation was monitored by an automated Rudolph ellipsometer, equipped with a He-Ne laser (wavelength 632.8 nm). The substrates compared in the study were hydrophilic negatively charged silica surfaces and hydrophobic methylated silica surfaces. The results show that the adsorption of salivary proteins is a very rapid process on both types of surfaces. Part of the formed biofilm, however, desorbed upon rinsing, indicating that the proteinaceous material was adsorbed with varying binding strengths. Larger adsorbed amounts were recorded on hydrophobic than on hydrophilic surfaces. Increase of ionic strength caused larger amounts to be adsorbed on both types of surfaces but change of pH did not affect the adsorption on either of the studied surfaces. Ellipsometry was found to be a suitable technique to monitor the adsorption of salivary proteins at solid/liquid interfaces.

Adsorption↗

PubMed1992

Effect of delmopinol on the viscosity of extracellular glucans produced by Streptococcus mutans.

The surfactant delmopinol, which is a new antiplaque agent with a low anti-microbial profile, was tested for its effects on the viscosity of bacterial extracellular glucans. Glucans were isolated from Streptococcus mutans broth supernatants incubated with 0.15 M sucrose in 50 mM sodium phosphate buffer at pH 6. The viscosity was measured in a shear rate range from 15 to 230 reciprocal seconds. The viscosity of the water-soluble glucan was found to be independent of shear rate whereas the water-insoluble glucan showed a strong shear thinning. The addition of delmopinol to preformed glucans did not affect the viscosity nor the shear rate dependence of the glucans. However, when present during synthesis of the polysaccharides, delmopinol was found to reduce the viscosity of both water-soluble and water-insoluble glucans by approximately 50% at the shear rates investigated. The reduction in viscosity for the water-soluble glucans was obtained at a delmopinol concentration of 0.32 mM (0.01%) and for the water-insoluble glucans at 3.2 mM delmopinol. The observed reduction of viscosity of glucans indicates that the in vivo stability of plaque matrix after delmopinol treatment would be lowered, which may lead to a reduction of plaque cohesion and thus facilitate mechanical plaque removal.

Glucans↗