Simultaneous removal of nitrate and phosphate using cross-flow micellar-enhanced ultrafiltration (MEUF)

The feasibility of cross-flow micellar-enhanced ultrafiltration (MEUF) was investigated to remove nitrate and phosphate simultaneously. At the above critical micelle concentration (CMC), a cationic surfactant added in wastewater forms micelles, which have positive charge on their surface. Anionic contaminants such as nitrate and phosphate can be bound on the micelles by electrostatic interaction, and the micelle-pollutants complex is removed effectively by ultrafiltration. In this study, a cross-flow MEUF system was designed and investigated the feasibility of MEUF for field application. A cationic surfactant, cetylpyridinium chloride (CPC), was used, and the synthetic wastewater was treated by the polyacrylonitrile membranes with molecular weight cut-off (MWCO) of 30,000 Da and 10,000 Da. With the molar ratio of CPC to total pollutants of > 3, > 86% of nitrate and > 91% of phosphate were removed, respectively, and > 97% of CPC was also rejected. The flux was maintained 20-30% of the flux of distilled water. Therefore, it is feasible to remove nitrate and phosphate simultaneously using the cross-flow MEUF system.

The effect of antimicrobial pre-treatments on the performance of resin composite restorations

This study evaluated the effects of four cavity pre-treatments on the microleakage of a fifth generation adhesive system and accompanying resin composite. Sixty human molars were randomly selected for cavity pre-treatment for the following material groups: Ultra-Etch 35% phosphoric acid gel, Ultra-Etch AB 35% phosphoric acid gel with cetylpyridinium chloride antimicrobial agent, Ultra-Etch 35% phosphoric acid gel followed by Concepsis chlorhexidine gluconate antimicrobial solution, Ultra-Etch 35% phosphoric acid gel followed by Consepsis Scrub chlorhexidine gluconate antimicrobial slurry and no etchant and/or cavity pre-treatment. Circular preparations were cut on the facial or lingual surface of each tooth and treated with the appropriate etchant/cavity disinfectant. PQ1 self-priming adhesive was placed in the preparations followed by Vitalescence resin composite. The molars were thermocycled, sealed with nail varnish, placed in 5% methylene blue dye and sectioned. Leakage was assessed by dye penetration at the occlusal and gingival surface positions of the specimen blocks using a binocular microscope. The Consepsis Scrub and no pre-treatment groups revealed significantly greater leakage than the other groups treated with antimicrobial disinfectants or etchants. No significant differ. ences were shown in the two etchant groups that were compared, Ultra-Etch and Ultra-Etch AB. Significantly greater leakage was not exhibited by the same materials at the occlusal vs gingival surface positions.

Utility of formazans and cetylpyridinium chloride in rapid spectrophotometric determination of zinc in biological materials and pharmaceutical formulations

A facile, rapid and sensitive spectrophotometric method for the determination of zinc is performed, based on complexation reaction between the metal ion and 1,5-diphenyl-3-acetylformazan (I) 1-(o-carboxyphenyl)-3-acetyl-5-acetylformazan (II), 1-(o-carboxyphenyl)-3-acetyl-5-phenylformazan (III), and 1-(o-carboxyphenyl)-3-acetyl-5-m-tolylformazan (IV) in the presence of cationic surfactant cetylpyridinium chloride (CPC). The important analytical parameters and their effects on the reported system are investigated. Zinc reacts with the reagents (I-IV) and CPC in the ratio 1:1:2 (metal:reagent:CPC) in the pH range 8.5, 7.5, 5.5 and 6.5 to form a ternary complex with an absorption maximum 616, 656, 672 and 599 nm, respectively. The reaction was extremely rapid at room temperature, and the absorbance value remains unchanged for at least 1 week. The apparent stability constant of the complex were found to be 13.1 9.2, 11.4 and 12.3, and adheres to Beer's law for 0.05-3.50 microg per 10 ml of zinc. For more accurate analysis, Ringbom optimum concentration range was found from 0.08 to 3.20 microg per 10 ml of zinc. The apparent molar absorptivity, Sandell sensitivity, detection and quantification limits are also calculated. Taking a constant concentration of metal ion and determining its concentration in the presence of large number of foreign ions tested the effect of foreign ions. The method was applied for determination of zinc in serum, human hair and pharmaceutical formulations, where excellent agreements between reported and obtained results were achieved. The relative standard deviation was better than 1.67%.

Effect of toothpaste on the plaque inhibitory properties of a cetylpyridinium chloride mouth rinse

BACKGROUND AND AIMS

Cetylpyridinium chloride (CPC) mouth rinses have moderate plaque inhibitory activity when used alone but rarely have shown adjunctive benefits to tooth brushing with toothpaste. Several explanations for this apparent anomaly can be proferred, including loss of antiseptic activity due to interactions with toothpaste ingredients. The aim of this study was to measure the effect of toothpaste on the plaque inhibitory properties of a CPC mouth rinse using paired rinses of CPC, toothpaste slurry (TP) and water (W).

METHODS

The study was a single blind, randomised, seven-treatment, cross over design balanced for residual effects, involving 21 healthy, dentate subjects. The paired rinses were: W-CPC, CPC-W, TP-CPC, CPC-TP, W-TP, TP-W and W-W. Rinsing with solutions or slurries was done for 60 s twice per day. On day 1, subjects were rendered plaque free, suspended tooth cleaning and commenced the allocated rinse regimen. On day 5, plaque was scored by index. A 2(1/2) day wash out of normal oral hygiene was allowed between each regimen.

RESULTS

The order from lowest to highest plaque scores was as follows: W-CPC = CPC-W < CPC-TP < TP-CPC < or = W-TP < TP-W < W-W. Several differences in pairs of treatments were statistically significant, the most relevant of which were significantly less plaque with W-CPC compared to TP-CPC, TP-W and W-TP, and significantly more plaque with W-W compared to all other regimens except TP-W.

CONCLUSIONS

Toothpaste, whilst possessing some plaque inhibitory activity, when used immediately before a CPC mouth rinse adversely affected the plaque inhibitory action of this antiseptic. This in part may explain the reported lack of adjunctive benefits of CPC rinses to normal oral hygiene practices and supports the suggestion, made for chlorhexidine rinses, that their use should follow toothpaste by at least 60 min.

Interaction of cetylpyridine bromide with nucleic acids and determination of nucleic acids at nanogram levels based on the enhancement of resonance Rayleigh light scattering

Resonance Rayleigh light scattering (RRLS) spectra of cetylpyridine bromide (CPB)-nucleic acid system and their analytical application have been first studied. The effective factors and optimum conditions of the reaction have been investigated. After CPB and nucleic acid are mixed together, a new absorption peak located at 300 nm appeared, which is due to the formation of new ion associate of CPB-nucleic acid. The new associate can result in two apparent RRLS peaks at 310-400 and 460-480 nm. The RRLS peak of the corrected spectra located at 290-350 nm, which indicate that the RRLS is originated from the absorption of CPB-nucleic acid associate. The peak at 460-480 nm disappears in the corrected RRLS spectra, which indicated that this peak is originated from the strong line emission of the Xe lamp. Under the optimum conditions, the enhanced intensity of RRLS is proportional to the concentration of nucleic acid in the range of 5.0 x 10(-9)-5.0 x 10(-5) g ml(-1) for calf thymus DNA (ctDNA), 1.0 x 10(-8)-4.0 x 10(-5) g ml(-1) for fish sperm DNA (fsDNA) and 1.0 x 10(-8)-5.0 x 10(-5) g ml(-1) for yeast RNA (yRNA). The detection limits (S/N = 3) are 4.3, 8.7 and 7.4 ng ml(-1), respectively. Synthetic samples were determined satisfactorily.

Molecular alignment of denatured states of staphylococcal nuclease with strained polyacrylamide gels and surfactant liquid crystalline phases

Residual dipolar couplings reflect the orientation of vectors between pairs of magnetic nuclei relative to a unique set of molecular axes. Thus, unlike NOEs and scalar couplings, dipolar couplings provide access to long-range structural information. A prerequisite for measurement of these NMR parameters is imposition of a weak net alignment, most simply by forcing the macromolecules to tumble in an asymmetric environment that restricts some orientations more than others. In this report, several denatured forms of staphylococcal nuclease are aligned by using compressed and stretched polyacrylamide gels, a nonionic type of lipid bilayer disk or bicelle, and a liquid crystalline phase formed by a cationic lipid. All three types of media can be used at high urea concentrations. While polyacrylamide gels and bicelles produce similar alignment tensors through steric interactions, a liquid crystalline phase of cetylpyridinium bromide aligns denatured nuclease along a different set of axes, presumably through electrostatic effects. The analysis of residual dipolar couplings collected with two different alignment tensors may permit the calculation of ensembles of conformations. The dipolar couplings observed for staphylococcal nuclease denatured with urea, by low pH or by deletion of residues from both termini, suggest that all denatured forms share a common "topology", one which has been shown previously to be native-like. Although SDS/nuclease complexes give sharp and disperse (1)H-(15)N correlation spectra, only small couplings are observed in strained polyacrylamide gels.

Morphology of three lyotropic liquid crystalline biological NMR media studied by translational diffusion anisotropy

The morphologies of three dilute liquid crystalline phases, which are widely used for biological NMR spectroscopy, are investigated by the study of tracer self-diffusion. The aqueous liquid crystalline media investigated include the common phospholipid bicelle medium, a phase consisting of a mixture of pentaethyleneglycol mono dodecyl ether and hexanol, and a medium containing cetylpyridinium bromide and hexanol. Threonine and water were used as tracer molecules for probing the aqueous environment, and tetramethylsilane (TMS) was for probing the lipophilic environment. Pulsed field gradient NMR was used to measure tracer self-diffusion rates in three orthogonal directions. Although results for the water-soluble tracers in bicelle media do not contradict the widely accepted disk-shaped bicelle model, the high TMS diffusion rate observed in the bilayer plane requires extensive transient edge-to-edge contacts of such disks. This morphology is essentially that of a heavily perforated lamellar bilayer phase and explains why this medium remains liquid crystalline well below the Onsager limit for disk-shaped nematogens. Below 25 degrees C, a bicelle mixture consisting of dimyristoyl phosphatidyl choline and dihexanoyl phosphatidyl choline remains isotropic, but tracer diffusion obstruction indicates that the particles are significantly oblate. The diffusion anisotropy in the penta(ethyleneglycol) mono dodecyl ether liquid crystals confirms the previously proposed alpha-lamellar phase. However, weak inhibition of aqueous-phase self-diffusion in the z direction points to the presence of bridge- or caplike obstructions, and the bilayers appear slightly permeable to water. If the previously proposed concentric cylinder superstructure of bilayers applies, the diffusion data indicate that the most outer cylinder must have a diameter greater than 50 microm. The tracer self-diffusion data for the cetylpyridinium bromide/hexanol medium is only compatible with a planar alpha-lamellar phase, with its local director orthogonal to the magnetic field, and a very large domain size over which the director remains parallel.

Effect of dental unit waterline biocides on enamel bond strengths

This study evaluated the effects of chemical biocides used to control dental unit waterline biofilm on the bond strength of resin to enamel. Sixty bovine teeth were randomly assigned to six treatment groups. One-way ANOVA revealed a significant difference in means (p < 0.001) and Tukey's multiple range test indicated that three of the experimental groups had significantly lower mean shear bond strengths than the control (p < 0.05). This finding suggests that dental unit waterline biocides may adversely affect adhesion of resin to enamel.

Adsorption of Salmonella enteritidis by cetylpyridinium-exchanged montmorillonite clays

Recent experiments in our laboratory have suggested that certain montmorillonite clays, when exchanged with the cationic surfactant cetylpyridinium (CP), may be useful in removing bacteria from aqueous solution. During an initial study, screening various CP-exchanged products for potential antibacterial activity, three CP-exchanged clays - CP*AAM (acid-activated montmorillonite), CP*STx-1 (Ca(++)-montmorillonite), and CP*SWy-2 (Na(+)-montmorillonite), proved to be the most effective. Binding studies were performed using 1mg each of CP-exchanged AAM, STx-1, and SWy-2 with a standardized Salmonella enteritidis solution containing approximately 40,000 colony forming units (CFU)/ml. The modified clays reduced bacterial numbers 98.1, 97.6, and 95.2%, respectively. In contrast, the parent clays only produced reductions of 39.8, 16.9, and 16.6%, respectively. Attempts were made to desorb CP from the modified clays by washing in sterile physiological saline for 24h. The resulting wash solutions failed to produce any significant reduction in bacterial colony counts; while, the washed clays retained their full antimicrobial activity. These findings suggested that the antibacterial effect of the clays is localized on the clay surface and is not due to CP dissociating from the clay. Electron microscopy revealed that the bacteria adhered to the surface of the CP-exchanged clays, but not the parent clays. Results from timed binding studies showed that the antibacterial effect was stable over the period observed. Rates of binding were positively influenced by increasing temperature, not affected by changes in pH, and negatively influenced by the presence of organic contaminants. The mechanism by which bacterial counts are reduced may involve the enhanced hydrophobicity and affinity of the CP-exchanged clay for Salmonella and the antibacterial activity of CP.

Antibacterial activities and release kinetics of a newly developed recoverable controlled agent-release system

We attempted to develop a resin with a recoverable antibacterial activity based on the desorption/adsorption of a cationic bactericide by the ion-exchange mechanism. The aims of this study were to investigate the release kinetics of the agent and the antibacterial activity of this newly designed resin system. An experimental resin was prepared by the addition of methacrylic acid as a cation-exchanger and a cationic antibacterial agent, cetylpyridinium chloride (CPC), to triethyleneglycol dimethacrylate. The amount of CPC desorbed from the experimental resin into buffer solutions at pH 4-8 was measured. The adsorption of CPC to control resin and re-adsorption of CPC to the experimental resin, which had once desorbed the agent, were also determined. The antibacterial activity of experimental resin against Streptococcus mutans was evaluated, and the relationship between bacterial acid production and antibacterial effect was assessed. The experimental resin desorbed CPC at pH < or = 6, and the amount of agent desorbed increased with increasing acidity. The control resin adsorbed CPC when immersed in CPC aqueous solution at a rate determined by the concentration of the agent and immersion time. The experimental resin, once desorbed CPC, could re-adsorb the bactericide by being exposed to a solution of the agent. Less plaque formed on the experimental resin, and the growth and survival of S. mutans was inhibited in the condition in which acid was produced. These results demonstrate that the resin system proposed was able to desorb and re-adsorb the cationic bactericide by an ion-exchange mechanism and could show an inhibitory effect on S. mutans growth and plaque formation.

Fragmentation of polyatomic molecules by grazing incidence surface-induced dissociation (GI-SID)

The grazing incidence surface-induced dissociation (GI-SID) of n-hexadecylpyridinium and verapamil ions generated by fission fragment desorption was studied. These molecules show the effect of enhanced surface-induced dissociation at grazing incidence as it was observed in former experiments with metal organic ions. A liquid film of perfluorinated polyether is used as collision surface. Small hydrocarbon fragment ions predominate in the GI-SID spectra. Pyridine ions appear as specific fragment ions in the GI-SID spectrum of n-hexadecylpyridinium. The GI-SID conversion efficiency varies in the range 40-70%. The experimental results are discussed within the scope of a quantum mechanical model which is based on the accumulation of internal molecular energy by resonant excitation of collective vibrational states and energy transfer to a trap bond due to dipole-dipole interactions. In this context the GI-SID spectra of n-hexadecylpyridinium and verapamil ions are compared with the fragmentation occurring in regular (252)Cf plasma desorption mass spectrometry.

Assessment of the effects of cetylpyridium chloride on water content of the collagen-keratocyte matrix of the mammalian corneal stroma ex vivo

The effects of cationic surfactants on the time-dependent increases in hydration of the corneal stroma were investigated to assess if the contribution of the proteoglycans could be titrated and how it might relate to the maximum and minimum swelling properties of the corneal stroma. From recent post-mortem eyes from adult sheep, square (8 x 8 mm) samples of corneal stroma were prepared and incubated in isotonic neutral pH mixed salts solution with added glucose, or pure water, at 37 degrees C. The time-dependent changes in wet mass were assessed over 24 h in the absence or presence of 0. 001-2% w/v cetylpyridium chloride (CPC) or benzalkonium chloride (BAC). The rate and magnitude of stromal swelling was reduced in a concentration-dependent fashion by the surfactants. In mixed salts solution, 100% inhibition of swelling could be achieved at 2% CPC and BAC. In pure water, the relative swelling was much more substantial and could only be attenuated by CPC.

Determination of heparin in aqueous solutions

OBJECTIVE

To develop a volumetric method for assaying heparin in aqueous media.

METHOD

Heparin is precipitated out with an aqueous solution of an organic amine by titration and the end-point is based on the measurement of the medium dielectric permittivity. We studied the titration of a 500 IU/ml heparin solution with a 0.08 M cetylpyridinium chloride solution at pH 6.8. Then, we assayed sulphate groups selectively at pH 2. The results were compared against a classical method of SO2 determination. The sensitivity and reproducibility of the volumetric method were evaluated at pH 6.8 and compared with the characteristics of a chromogenic method, usually used for the assay of heparin in biological fluids.

RESULTS

A linear relationship between anticoagulant activity and sulphate and carboxyl group concentration was observed. The method was less sensitive but more reproducible than the chromogenic method.

CONCLUSION

The proposed method can be used for aqueous solutions and is easy to carry out. It can be fully automated and applied to formulation studies.

Chondroitin sulfate isomers in synovial fluid of healthy and diseased human temporomandibular joints

Synovial fluid was collected from the superior articular cavity of the temporomandibular joint in patients with unilateral internal derangement and joint pain whose contralateral joint was healthy. Glycosaminoglycans were liberated by digestion with pronase E, and precipitated with cetylpyridinium chloride and ethanol. Unsaturated disaccharide isomers of chondroitin sulfate, obtained following chondroitinase ACII digestion, were analyzed by high-performance liquid chromatography. Analytic data indicated that deltaDi-0S and deltaDi-6S were often found in chondroitin sulfate from the fluid of the diseased joints. The amounts of deltaDi-0S and deltaDi-6S differed significantly between synovial fluid samples from the diseased and healthy joints. Comparison of the relative proportions of the unsaturated disaccharides in the synovial fluid with previously reported values for several tissues, indicated that the chondroitin sulfate originated from articular cartilage, with possibly some contributions from soft connective tissues and serum present in the synovial fluid. These results suggest that chondroitin sulfate in the synovial fluid provides a useful indicator of the degree of internal derangement of the temporomandibular joint.

Application of terbium sensitized fluorescence for the determination of fluoroquinolone antibiotics pefloxacin, ciprofloxacin and norfloxacin in serum

A simple, rapid and sensitive spectrofluorimetric method for the determination of fluoroquinolone antibiotics, norfloxacin (NOR), ciprofloxacin (CIP) and pefloxacin (PEF) is described. The method is based on the radiative energy transfer from fluoroquinolones to terbium ions (Tb3+) in the presence of tri-n-octylphosphine oxide (TOPO) in weakly acidic (pH 5.5) micellar solution of cetylpyridinium chloride (CPCI). Optimum conditions for the formation of the fluoroquinolone-Tb(3+)-TOPO ternary complexes have been investigated. Under optimized conditions the detection limits are 1.7, 1.2 and 4.4 nM for NOR, CIP and PEF, respectively, while the range of application for all three drugs is 0.05-10 microM. The method has been successfully applied to the determination of NOR, CIP and PEF in serum samples after deproteinization with acetonitrile (serum-acetonitrile; 1:2, v/v). The mean recoveries from serum samples spiked with NOR, CIP and PEF (5.0-50.0 microM) were (90.3 +/- 4.9), (105.0 +/- 3.6), and (95.3 +/- 1.5)% respectively. Within-run and day-to-day s, values for 5.0, 25.0 and 50.0 microM of each fluoroquinolone varied from 1.7 to 5.4% and from 3.3 to 12.8%, respectively. The influence of several usually coadministered drugs on the determination of fluoroquinolones in serum has been investigated.

Evaluation of Cetylpyridinium Chloride-Containing Mouthwashes Using In Vitro Disk Retention and Ex Vivo Plaque Glycolysis Methods

The Disk Retention Assay (DRA) is an in vitro method developed to measure the available level of cetylpyridinium chloride (CPC) in mouthwash formulations. This method is based on the binding of the cationic CPC molecule to the anionic surface of a cellulose filter disk. Aqueous CPC solutions demonstrate a linear response (A545) for concentrations up to 0.3%. Higher levels of CPC showed no increased response in the assay. Among common oral product ingredients, at relevant concentrations, surfactants are the primary compounds which inhibit CPC detection and hence, chemical availability. Poloxamer-407 decreased CPC availability to 60% at 0.1%, to 10% at 0.5%, and to 24-33% for 0.2-0.4%. Polysorbate-80 decreased CPC availability to 30% at 0.1% and 6% at 0.25%. A range (4-54%) of available levels of CPC were determined for several commercial products containing 0.045-0.05% nominal levels of CPC indicating significant formulation excipient influence. A plaque glycolysis (PG) assay was used to determine the biological activity of all mouthwash products analyzed by DRA. An experimental series of mouthwash formulations having nominal CPC levels of 0-0.10% demonstrated a good correlation (r2 = 0.955) between the calculated available level of CPC (DRA) and inhibition of plaque glycolysis. The calculated available level of CPC from select commercial mouthwash products, also fit the established correlation with biological activity. The combination of DRA and plaque glycolysis methods are valuable tools which can be used during development to maximize the biological activity of CPC mouthwash formulations prior to clinical evaluation.

[Competitive binding of tetrabutylammonium and cetylpyridinium cations on C18 surfaces]

The adsorption behavior of tetrabutilammonium (TBA) and cetylpyridinium (CP) cations was studied on Hypersil 5-ODS sorbent. After establishing, that CP has about 5 fold stronger affinity to the C18 surface, than the structurally different, symmetric, spheric molecule of TBA, the adsorption from their common solution was also examined. The data of "competitive binding" seem to show, that TBA should have certain selective binding sites on the C18 surface, from which, it can not be displaced by the CP even in the case the latter is present in a 4 fold excess in the mobile phase. The maximal coverage was found 52.9% (CP) and 12% (TBA) i.e. every second of C18 groups is covered by CP cations and only 1/8th of C18 groups may interact with TBA. The accessible, proton releasing silanol content, related to the total C18 content of the column, was found very low.

Ocular and dermal irritation studies of some quaternary ammonium compounds

The primary ocular and dermal irritations of four quaternary ammonium compounds, namely cetylpyridinium chloride (CPC), stearylphenylethyldimethylammonium tosylate (SPDAT), dimethyldistearylammonium bisulfate (DDABS) and tri(N-butyl)benzylammonium 4-hydroxynapththalene-1-sulfonate (TBAHNS), were studied. Both CPC and SPDAT were extremely or severely irritating to the eyes of the test animals, whereas DDABS and TBAHNS were mildly or minimally irritating. Both CPC and SPDAT were also severely or extremely irritating to the skin of the test animals, while DDABS and TBAHNS were non-irritating. These quaternary ammonium compounds have little similarity in chemical structure and possess different solubilities. CPC is very soluble in both lipid and water; SPDAT is very soluble in lipid but only slightly soluble in water; and DDABS and TBAHNS are poorly soluble in either lipid or water. The irritancy of these compounds is likely to be related to their solubility, in addition to the cationic characteristics. It appears that not all quaternary ammonium compounds in this study are irritants. Those that are not soluble are not expected to be absorbed in eye/skin tissues and thus irritation reactions will not take place. The use of in vitro alternatives should be considered when assessing the ocular and dermal irritancy potential of water- and lipid-soluble quaternary ammonium compounds.

[Comparison of in vitro action of cetylpyridinium chloride containing preparations]

The fungicidal efficacy on Candida albicans of cetylpyridinium chloride (CAS 123-03-5) solution (CPC I solution, Dobendan) in various dilutions was tested with help of the quantitative suspension test and compared with CPC containing self-made preparations with or without addition of alcohol. The dilution of all test preparations caused an impairment of antimicrobial efficacy; the activity was reduced distinctly: due to a 50% dilution a decrease of 2-3 ten's powers was observed. The reduction of efficacy of the self-made preparation was less pronounced. The addition of 1% albumin as well impaired the fungicidal activity of all test preparations. CPC + alcohol revealed the most pronounced fungicidal efficacy; no differences were seen between CPC (without alcohol) and CPC I solution.

An approach to efficacy screening of mouthrinses: studies on a group of French products (I). Staining and antimicrobial properties in vitro

There is a large and increasing number of oral hygiene products available to the general public. As such, it is difficult to demonstrate efficacy for all in long-term home-use studies. The aim of this project was to determine whether screening studies could position the activity and efficacy of a number of antiseptic mouthrinses, available in France, by comparison with an established product. This study reports the experiments in vitro. The products under test were, 4 containing chlorhexidine (Eludril, Hibident, Parodex and Prexidine) with Hibident considered the positive control, one containing cetylpyridinium chloride (Alodont) and one containing hexetidine (Hextril). The 1st study determined the antibacterial profile of the chlorhexidine products against a panel of oral bacteria using an agar dilution method. The 2nd study recorded, by optical density, the propensity of all products to induce tea staining on clear acrylic specimens. The maximum inhibitory dilution (MID) of the chlorhexidine products against the test organisms, once adjusted for initial concentration differences, were essentially similar. One exception was Eludril which had an increased MID against Capnocytophaga sputigena, an organism normally less sensitive to chlorhexidine. Hibident and Prexidine produced expected levels of tea staining; that produced by Parodex was lower than the expected. Staining by Eludril was little different than water controls suggesting markedly reduced availability of chlorhexidine in this product.(ABSTRACT TRUNCATED AT 250 WORDS)

A filter paper assay for hyaluronic acid synthetase: application to the enzyme from Swiss 3T3 fibroblasts

An improved assay for hyaluronic acid (HA) synthetase is described that is suitable for rapid processing of large numbers of samples. High background levels of unincorporated radioactivity are removed by passage of the reaction through a Sephadex G-50 spin column. The labeled HA product is then precipitated onto glass fiber filters with cetylpyridinium chloride. Apparent Km values for HA synthetase from Swiss 3T3 fibroblasts are 10.8 and 58.4 microM for UDP-glucuronic acid and UDP-N-acetylglucosamine, respectively. HA synthetase activity of quiescent cells is 4.5% of that found in actively growing cells and is stimulated in response to 10% calf serum. There is a greater than 10-fold increase in HA synthetase activity when cells are harvested with hyaluronidase as compared with trypsin.

Alcohol-containing mouthwasheses: effect on composite color

This study investigated whether commercially available mouthwashes could affect or change the color of a hybrid composite resin. Twenty-four disks were fabricated and divided into eight equal groups for testing. At baseline, six colorimetric recordings and color parameters (L*, a*, b*) were recorded for each grouping of disks using a Chroma Meter CR-300 in reflectance mode. The groups of disks were immersed in their respective mouthwashes for 2 minutes a day in a vibratory fashion over a 6-month period. At the end of 6 months, color differences, delta E, were calculated between the base line and test recordings. The results indicate that rinsing with mouthwashes for 6 months can cause a hybrid resin to undergo color variations. Except for one product the color variations were not clinically significant.

Activation and stabilization of enzymes entrapped into reversed micelles. Studies on hydrolyzing enzymes--protease and alpha-amylase

Observations of the activity of two hydrolyzing enzymes-protease and alpha-amylase--entrapped inside the reversed micelles formed by surfactants in hexane, benzene, and cyclohexane are reported. The surfactants chosen for this study are: Tween 80, a nonionic surfactant, Cetyl pyridinium chloride, a cationic surfactant, and two anionic surfactants, sodium lauryl sulfate and Aerosol OT. Tween 80 enhances the activity of both protease and alpha-amylase. Sodium lauryl sulfate and Aerosol OT, which are ionic surfactants, enhance the activity of protease, but inhibit the activity of alpha-amylase. Cetyl pyridinium chloride, however, enhances the activity of alpha-amylase, but inhibits the activity of protease. Enhanced activity is generally severalfold greater in comparison to the activity observed in the usual aqueous system in the absence of reversed micelles. It has also been observed that the enhanced activity of the enzymes entrapped inside the reversed micelles remains preserved for a much longer period of time in comparison to the activity in the usual aqueous systems. These observations, which support the view that with proper choice of surfactant and the organic solvent, reversed micelles act like a microreactor that provides a favorable aqueous micro-environment for enzyme activity, have biotechnological overtones.

A comparison of cetylpyridinium chloride, triclosan and chlorhexidine mouthrinse formulations for effects on plaque regrowth

A relatively small number of agents are used in mouthrinse products, although the possible variability in the final formulations is enormous. The aim of this study was to compare equal concentrations of 3 antimicrobial agents, in simple formulations, for plaque inhibition. This 4-day plaque regrowth study was a 5-cell, randomised, double blind cross-over design, involving 20 healthy human volunteers. The mouthrinse formulations were aqueous 0.05% solutions of cetylpyridinium chloride (CPC), chlorhexidine and triclosan, together with a 0.1% CPC and a minus active control rinse. On Day 1, from a zero plaque baseline, volunteers ceased normal oral hygiene and rinsed 2x daily for 1 min. with 10-ml volumes of the allocated rinses. On Day 5, plaque was scored by index and area. All rinses produced lower mean plaque values compared to control, but unlike the CPC and chlorhexidine rinses, the differences with triclosan did not always reach significance. The CPC and chlorhexidine rinses were always significantly more effective than the triclosan rinse. The greatest plaque inhibition was with 0.1% CPC although rarely significantly greater than the 0.05% CPC and chlorhexidine rinses which were similar in efficacy. The results indicate that further studies on lower concentration chlorhexidine solutions are warranted.

Use of the triiodide-cetylpyridinium chloride micellar system for the determination of benzoyl peroxide in pharmaceutical preparations

A kinetic spectrophotometric method for the determination of benzoyl peroxide in acne preparations is proposed. The method is based on the reduction of benzoyl peroxide by iodide in the cationic micellar medium provided by cetylpyridinium chloride (CPC). The triiodide ion produced associates with CPC micelles, which gives rise to an absorption maximum at 500 nm in addition to substantially increased absorptivity and stability constant for the triiodide complex. Acne preparations can be analyzed directly after dissolution of the samples in ethanol. The detection limit thus achieved is 0.033 microgram.mL-1, so the proposed method surpasses existing alternative methods in sensitivity. The relative standard deviation for 0.25 microgram.mL-1 is 2.1%.

Inhibition of plaque formation by local application of a degradable controlled release system containing cetylpyridinium chloride

The effect of a degradable controlled release system containing cetylpyridinium chloride (CPC) on plaque accumulation and gingivitis was evaluated when applied on the anterior teeth of volunteers (16-17 years) over 4 weeks. At baseline, plaque index (PI) and gingival index (GI) of the Ramfjord teeth were measured in the experimental and placebo groups, including 23 and 21 participants respectively. Following scaling and root planning, the participants were instructed to brush, using one brush stroke, the film-forming solution on the buccal surface of the maxillary and mandibular incisors, 1 x a day before bedtime. The applied active solution contained 9 mg of CPC (approximately 80 mg of 11% CPC solution), while the placebo solution was identical in formation, but without the active agent. After 4 weeks, in the CPC-applied group, the recorded PI scores were 0.52 (+/- 0.56) in the anterior area and 1.31 (+/- 0.80) in the posterior area, whereas the corresponding areas in the placebo group reached 1.25 (+/- 0.74) and 1.51 (+/- 1.00), respectively. The PI = 0 frequency in the buccal anterior surfaces after 4 weeks was 54.6% (+/- 38.7%) in the experimental group as compared with 21.9% (+/- 29.0%) in the placebo group (p = 0.005). In contrast to the anterior teeth, there was no significant difference between groups with respect to the PI scores in the non-applied posterior teeth. It may be postulated that the impressive 58% inhibition of plaque accumulation at the site of application is the result of an increase of the substantivity of the CPC due to its incorporation in the film-forming degradable controlled release system.

A spectrophotometric modification of a sensitive densitometric Safranin O assay for glycosaminoglycans

Recently, an assay for quantification of glycosaminoglycans has been reported based on precipitation with Safranin O (Lammi, M. and Tammi, M. (1988) Anal. Biochem. 168, 352-357). In this procedure, the precipitate which forms when the glycosaminoglycan or proteoglycan is mixed with the Safranin O is collected with a dot-blot apparatus onto a membrane filter. The intensity of the color in the dots is measured densitometrically and is proportional to the amount of glycosaminoglycan or proteoglycan in the sample. This report describes a modification of the densitometric Safranin O assay which allows its use as a spectrophotometric assay. For this, the precipitates are solubilized in cetylpyridinium chloride and the absorbance determined for the resulting solutions. As with the densitometric method, guanidinium chloride diminishes the color intensity. However, the color is stable, even after solubilization, for at least one week. The precipitates collected from as much as 10 micrograms of material can be solubilized in as little as 100 microliters of cetylpyridinium chloride, so that increased sensitivity may be obtained if the solubilized precipitate is measured in a microcuvet. Thus, solubilization with cetylpyridinium chloride allows use of the Safranin O assay for glycosaminoglycans and proteoglycans even when a densitometer is unavailable.