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Biomedical subjects

Doron Steinberg

Publications and source records attributed to Doron Steinberg.

At least 19 recordsLinked to original sources
PubMed2006

Effect of oxazaborolidines on immobilized fructosyltransferase analyzed by surface plasmon resonance.

Dental diseases are among the most prevalent afflictions of humankind. These diseases are associated with the formation of biofilms harboring pathogenic bacteria. Fructosyltransferases (FTF) are extra cellular enzymes of several oral bacteria. FTF are associated with the formation of extracellular polysaccharide matrix (fructans) which play a role in biofilm formation and oral bacteria physiology. Oxazaborolidines have been shown to inhibit biofilm formation. The purpose of this study was to examine if the anti-biofilm effect is, in part, an effect on the immobilized enzymes synthesizing the extra cellular polysaccharide participating in biofilm formation. Eight different oxazaborolidines (BNO1-BNO8) were synthesized and evaluated for their affect on the synthesis of fructans by FTF using the biomolecular interaction analysis (BIAcore) system which involves the use of real-time surface plasmon resonance (SPR) technique. The tested oxazaborolidines demonstrated a significant and immediate inhibitory effect on immobilized FTF activity. This effect was reversible. Our results show that oxazaborolidines can act as enzymatic inhibitors of FTF immobilized on the surface, also at levels lower than their MIC. Part of the anti-biofilm effect of BNOs may be accounted for this enzymatic inhibition.

Anti-Bacterial Agents↗
PubMed2006

Soluble sustained release gene delivery system.

Delivery of genetic substance to target cells remains an obstacle for efficient utilization of gene therapy approaches. In this study, we describe a formulation of methacrylate acid copolymer carrier of DNA, in which the release rate of the gene can be controlled by pH. Plasmid release was coupled with the polymer's dissolution, which was accelerated in alkali conditions. The released plasmid was intact and bioactive, although alteration from closed circular supercoil to relaxed conformation was observed. Confocal laser scanning microscopy detected the plasmid DNA along the central layers of the polymeric film. Gene delivery systems controlled by the dissolution of the polymeric films offer flexibility in quantity and size of the incorporated DNA, and therefore could have a potential for in vivo use.

Biocompatible Materials↗
PubMed2006

Differential expression profiles of Streptococcus mutans ftf, gtf and vicR genes in the presence of dietary carbohydrates at early and late exponential growth phases.

Dental caries is one of the most common infectious diseases that affects humans. Streptococcus mutans, the main pathogenic bacterium associated with dental caries, produces a number of extracellular sucrose-metabolizing enzymes, such as glucosyltransferases (GTFB, GTFC and GTFD) and fructosyltransferase (FTF). The cooperative action of these enzymes is essential for sucrose-dependent cellular adhesion and biofilm formation. A global response regulator (vicR) plays important roles in S. mutans ftf and gtf expression in response to a variety of stimuli. A real-time reverse-transcription polymerase chain-reaction was used to quantify the relative levels of ftf, gtfB, gtfC, gtfD and vicR transcription of S. mutans in the presence of various dietary carbohydrates: sucrose, D-glucose, D-fructose, D-glucitol (D-sorbitol), D-mannitol and xylitol. Ftf was highly expressed at late exponential phase in the presence of sorbitol and mannitol. GtfB was highly expressed in the presence of all the above carbohydrates except for xylitol at early exponential growth phase and glucose and fructose at late exponential growth phase. Similar to gtfB, the expression of gtfC was also induced with the presence of all the tested carbohydrates except for xylitol at early growth and glucose and fructose at late exponential phase. In addition, no effect of mannitol on gtfC expression at early exponential phase was observed. GtfD was less influenced compared to the gtfB and gtfC, demonstrating enhanced expression especially in the presence of sorbitol, glucose, mannitol and xylitol at early exponential phase and mannitol at late exponential phase. VicR expression was induced only at the presence of xylitol at late exponential phase, and a decrease in expression was recorded at early exponential phase. Our findings show that dietary carbohydrates have a major influence on the transcription of ftf, gtfB, gtfC and gtfD, but less on vicR. Sorbitol and mannitol, which are considered as noncariogenic sugar substitutes, may indirectly affect caries by promoting biofilm formation via enhanced expression of gtfs and ftf. These results suggest regulatory circuits for exopolysaccharide gene expression in S. mutans.

Bacterial Proteins↗
PubMed2006

Effect of different iodine formulations on the expression and activity of Streptococcus mutans glucosyltransferase and fructosyltransferase in biofilm and planktonic environments.

OBJECTIVES: The glucosyltransferase (GTF) and fructosyltransferase (FTF) enzymes play a pivotal role in dental biofilm formation as they synthesize polysaccharides that act as the extracellular matrix of the biofilm. Iodine is a unique antibacterial agent that has distinct properties from other conventional antibacterial agents. In this study we have examined the effect of iodine and povidone iodine (PI) on gtf and ftf expression in biofilm and planktonic environments and on immobilized and unbound GTF and FTF activity. METHODS: Real-time reverse transcription-PCR was used to investigate the effect of iodine and PI on ftf, gtfB and gtfC expression. The effect of iodine and PI on GTF and FTF activity was tested using radioactive assays. RESULTS: Our results indicate that iodine and PI in a tetraglycol carrier cause enhancement of expression of gtfB in Streptococcus mutans in biofilms but not in planktonic bacteria. PI in water induced expression of gtfB and gtfC in planktonic bacteria. However, iodine and PI strongly inhibit polysaccharide production by GTF and to a lesser extent by FTF activity. The inhibitory effect on GTF activity was similar in solution compared to its activity in the immobilized environment. This unique effect may be attributed to the distinct chemical properties of iodine compared with other antibacterial agents. CONCLUSIONS: This study indicates that iodine at sub-bactericidal concentrations demonstrates molecular and enzymatic effects that are highly associated with biofilm formation.

Anti-Bacterial Agents↗
PubMed2006

Synergic antibacterial effect between visible light and hydrogen peroxide on Streptococcus mutans.

OBJECTIVES: To evaluate the possibility of enhancing the phototoxic effect on Streptococcus mutans using a potentially antibacterial synergic effect between blue light and hydrogen peroxide (H2O2), and to investigate the antibacterial mechanism involved. METHODS: Growth of S. mutans samples was determined after exposure to light in the presence and absence of H2O2. The effect of such light on H2O2 degradation, on reactive oxygen species (ROS) generation and on the exposed-medium temperature was examined. RESULTS: The combination of light exposure for 20 s (approximately 23 J/cm2) and a concentration of 0.3 mM H2O2 yielded 96% growth inhibition, whereas, when applied separately, light exposure decreased bacterial growth by 3% and H2O2 by 30% compared with the control. The results showed no direct effect of the light on H2O2 degradation, a partial protective effect of ROS scavengers on S. mutans and a non-lethal increase in the medium temperature after light exposure. CONCLUSIONS: An antibacterial synergic effect between blue light and H2O2 was observed. The mechanism of the phototoxic effect on S. mutans was basically a photochemical process, in which ROS were involved. Application of such light in combination with H2O2 to an infected tooth could be an alternative to or serve as an additional minimally invasive antibacterial treatment.

Anti-Bacterial Agents↗
PubMed2006

Sustained-release delivery systems of triclosan for treatment of Streptococcus mutans biofilm.

Dental diseases are chronic infections caused by oral bacteria harboring the dental biofilm. Local sustained-release delivery systems prolong the duration of a drug in the oral cavity, thus enhancing its therapeutic potential, while reducing its side effects. Triclosan is an agent that was found to have an antibacterial effect against oral bacteria. However, its substantivity in the oral cavity is low, resulting in reduced antibacterial efficiency. The purpose of this study was to develop a local sustained release device containing triclosan and to test its antibacterial efficacy on Streptococcus mutans biofilm. Our results show that we can formulate an ethylcellulose-based, nondegradable, sustained-release device in which 80% of the loaded triclosan is released over a 10-day period. The release rate of triclosan corresponded to the Higuchi's planar homogenous diffusion release model (r2 = 0.998). A degradable local sustained-release delivery based on a methacrylate ester matrix was also developed for a faster release rate of triclosan. The release kinetics in those types of sustained-release delivery systems was erosion control. The local sustained-release delivery system significantly affected the viability of S. mutans in biofilm compared to placebo as was tested by confocal laser scanning microscopy. Our in vitro results show that triclosan can be incorporated into degradable or nondegradable sustained-release drug delivery systems. The release of triclosan from the local sustained-release delivery system can be controlled, thus extending its antibacterial properties.

Biodegradation, Environmental↗
PubMed2006

The in vitro effect of fluoridated milk in a bacterial biofilm--enamel model.

OBJECTIVES: The purpose of this study was to investigate the effect of milk and fluoridated milk on bacterially induced caries-like lesions. SAMPLE AND METHODS: Extracted impacted human molars were cut in half and covered with a varnish leaving a 4*4 mm window. The samples were coated with biofilm of S. sobrinus and were further divided into three experimental groups of S. sobrinus, S. sobrinus and milk and S. sobrinus and fluoridated milk. As negative controls served teeth incubated in saline. Of twenty tooth halves serial ground sections were cut through the lesions and investigated with polarization light microscopy (PLM) and scanning electron microscopy (SEM) and EDX element analysis. The PLM photographs were used for 3D reconstruction, volumetric assessment and determination of the extension of the lesion zones. Of eight tooth halves the biofilm on the enamel surface was studied with SEM and EDX element analysis. RESULTS: Volumetric assessment showed a statistically significant difference in the volume of the body of the lesion and the translucent zone between the milk group and fluoridated milk group. Quantitative element analysis demonstrated significant differences between sound enamel and the superficial layer in the fluoridated milk group. The biofilm on the enamel surface showed an increased Ca content in the milk group and fluoridated milk group. CONCLUSIONS: Milk as a common nutrient seems to play a complex role in in-vitro biofilm--enamel interactions stimulating bacterial demineralization on one hand, and, as effective fluoride carrier, inhibits caries-like demineralization.

Animals↗
PubMed2005

Evaluation of oxazaborolidine activity on Streptococcus mutans biofilm formation.

Dental diseases are among the most prevalent afflictions of humankind. These diseases are associated with the formation of biofilms harbouring pathogenic bacteria. Eight different derivatives of oxazaborolidines were synthesised and evaluated for their affect on Streptococcus mutans adhesion and biofilm formation. Structure-activity relationship was observed. The B-butyl moiety of the oxazaborolidines contributed an anti-adhesion effect for all derivatives, whilst its effect diminished when the boron atom was incorporated in a fused heterocyclic ring. The B-phenyl group induced bacterial adhesion in all tested compounds Oxazaborolidines may serve as novel agents for affecting oral biofilm formation. Moreover, the ability to alter the oxazaborolidine molecule and thus affect biofilms offers an excellent opportunity to study biofilm formation.

Anti-Bacterial Agents↗
PubMed2005

Cranberry high molecular weight constituents promote Streptococcus sobrinus desorption from artificial biofilm.

Dental biofilm harbouring oral bacteria is highly correlated with the progression of dental diseases. Disruption of biofilm formation via anti-adhesion agents is an alternative means to the antibacterial approach. Previous studies have shown that high molecular weight non-dialysable material (NDM) derived from cranberry juice inhibits the adhesion of Escherichia coli and the coaggregation of a variety of oral bacteria. In addition, it inhibits the formation of glucans and fructans synthesised by GTF and FTF. In the present study, we examined the anti-adhesion effect of NDM on S. sobrinus. NDM promoted desorption of S. sobrinus from biofilm in the presence and absence of extracellular glucans and fructans, although the effect was more pronounced in the absence of these polysaccharides. Precoating of the bacteria with NDM reduced their ability to form biofilm. Our results indicate that NDM could be exploited as an anti-biofilm agent.

Bacterial Adhesion↗
PubMed2005

Biodynamics of biofilm formation on nasogastric tubes in elderly patients.

BACKGROUND: We previously reported on the high propensity of pathogenic oral flora in the oropharynx of nasogastric tube-fed patients, and subsequently showed biofilm formation on the NGTs of these patients. There is a close relationship of biofilm and oropharyngeal colonization with pathogenic bacteria, aspiration pneumonia and antibiotic resistance. OBJECTIVES: To investigate the time relation between the insertion of a new NGT and formation of the biofilm. METHODS: We examined sequential samples on NGTs that were forcibly pulled out by the patients themselves during any of the 7 days after insertion. Scanning electron micrography and confocal laser scanning microscopy were used for biofilm detection. RESULTS: Biofilm was identified on 60% of the five samples of day 1 and on all the samples of the following days, by both microscopic methods. CONCLUSIONS: Biofilms form within a single day on most NGTs inserted for the feeding of elderly patients with dysphagia. Further research should be devoted to prevention of biofilm formation on NGTs.

Aged↗
PubMed2004

Effect of carbohydrates on fructosyltransferase expression and distribution in Streptococcus mutans GS-5 biofilms.

Streptococcus mutans produces a fructosyltransferase (FTF) enzyme, which synthesizes fructan polymers from sucrose. Fructans contribute to the virulence of the biofilm by acting as binding sites for S. mutans adhesion and as extracellular nutrition reservoir for the oral bacteria. Antibodies raised against a recombinant S. mutans FTF were used to test the effect of glucose, fructose, and sucrose on FTF expression in S. mutans GS-5 biofilms. Biofilms formed in the presence of fructose and glucose showed a higher ratio of FTF compared to biofilms formed in the presence of sucrose. Confocal laser scanning microscopy images of S. mutans biofilms indicated a carbohydrate-dependent FTF distribution. The layer adjacent to the surface and those at the liquid interface displayed high amounts cell-free FTF with limited amount of bacteria while the in-between layers demonstrated both cell-free FTF and cells expressing cell-surface FTF. Biofilm of S. mutans grown on hydroxyapatite surfaces expressed several FTF bands with molecular masses of 160, 125, 120, 100, and 50 kDa, as detected by using FTF specific antibodies. The results show that FTF expression and distribution in S. mutans GS-5 biofilms is carbohydrate regulated.

Antibodies, Bacterial↗
PubMed2004

Effect of a high-molecular-weight component of cranberry on constituents of dental biofilm.

BACKGROUND: Previous studies have shown that high molecular-weight non-dialysable material derived from cranberry juice (NDM) inhibits co-aggregation of a variety of oral bacteria. OBJECTIVES: In the present study, we examined the effect of NDM on several constituents of the dental biofilm, glucosyltransferase (GTF) and fructosyltransferase (FTF), as well as on the adhesion of Streptococcus sobrinus. RESULTS: The activity of immobilized and soluble GTF and FTF was inhibited by NDM (P > 0.05). NDM also inhibited adhesion of S. sobrinus to hydroxyapatite (P < 0.05). CONCLUSIONS: Our results indicate that NDM may affect biofilm formation. One of the proposed mechanisms is via inhibition of extracellular polysaccharide synthesis, which promote the sucrose-dependent adhesion of oral bacteria as S. sobrinus.

Bacterial Adhesion↗
PubMed2004

A high molecular mass cranberry constituent reduces mutans streptococci level in saliva and inhibits in vitro adhesion to hydroxyapatite.

Previous investigations showed that a high molecular mass, non-dialyzable material (NDM) from cranberries inhibits the adhesion of a number of bacterial species and prevents the co-aggregation of many oral bacterial pairs. In the present study we determined the effect of mouthwash supplemented with NDM on oral hygiene. Following 6 weeks of daily usage of cranberry-containing mouthwash by an experimental group (n = 29), we found that salivary mutans streptococci count as well as the total bacterial count were reduced significantly (ANOVA, P < 0.01) compared with those of the control (n = 30) using placebo mouthwash. No change in the plaque and gingival indices was observed. In vitro, the cranberry constituent inhibited the adhesion of Streptococcus sobrinus to saliva-coated hydroxyapatite. The data suggest that the ability to reduce mutans streptococci counts in vivo is due to the anti-adhesion activity of the cranberry constituent.

Adult↗
PubMed2004

Streptococcus mutans fructosyltransferase interactions with glucans.

Streptococcus mutans utilizes sucrose to synthesize glucans by glucosyltransferase and fructans by fructosyltransferase (FTF). Antibodies raised against a recombinant FTF were used to study S. mutans FTF secretion. Low amounts of cell-free FTF were found in culture of S. mutans grown with sucrose, while an increase in bacteria displaying cell surface FTF was detected. FTF added to S. mutans cultures was adsorbed to bacteria grown with sucrose but not to bacteria grown with glucose or fructose or to a gtf inactivated mutant grown with sucrose. Recombinant FTF was found to have high affinity for glucans suggesting that fructans and glucans are an integral part of the polysaccharide matrix of oral biofilms.

Biofilms↗
PubMed2004

Factors affecting mercury release from dental amalgam exposed to carbamide peroxide bleaching agent.

PURPOSE: To assess, in vitro, the effects of aging and surface polishing on mercury release from dental amalgams exposed to 10% carbamide peroxide at two pH levels. METHODS: Samples of fresh and aged amalgam, polished and unpolished, were treated with 10% carbamide peroxide at pH 4.5 and at pH 6.5 for periods of 1, 4, 7, 10 and 13 days. At each time period, mercury concentrations in solution were measured using a cold-vapor atomic absorption mercury analyzer system and compared to control samples treated with phosphate buffer. RESULTS: Amalgam samples exposed to 10% carbamide peroxide released significantly more mercury in solution than samples exposed to phosphate buffer controls. Mercury release was time-dependent and significantly higher in aged amalgam than in fresh amalgam (P < 0.001). Mercury release was also pH-dependent and higher in unpolished amalgam.

Analysis of Variance↗
PubMed2003

Influence of dental biofilm on release of mercury from amalgam exposed to carbamide peroxide.

Tooth bleaching is a popular procedure in modern aesthetic dentistry. Bleaching agents may affect amalgam restorations by altering the release of mercury. The aim of this study was to explore the effect of biofilm-coated amalgam restorations on the release of mercury in the presence of carbamide peroxide. Samples of SDI and Valliant amalgams were submerged for either 14 days or 7 months in buffered KCl after which they were coated with saliva, bacteria, and polysaccharides. The samples were exposed to 10% carbamide peroxide (CP) for 24 h. The amount of mercury released was examined for 120 h. Results showed that most of mercury release occurred within the first 24 h, after which the release rate decreased sharply. After 120 h the release of mercury from the tested samples was minimal and similar to the control group. The presence of biofilm coating on the amalgam samples did not induce the release of mercury but tended to reduce mercury release into the surrounding environment. CP induces the release of mercury from amalgam samples. However, the presence of biofilm did not prevent large amounts of mercury release from amalgam coated with biofilms and exposed to CP. This study indicates that dental biofilm may retard the release of mercury from amalgam restorations.

Biofilms↗