COMPOSITION AND METHOD FOR THE GENERATION OF CHLORINE DIOXIDE FROM THE OXIDATIVE CONSUMPTION OF BIOMOLECULES

Abstract

The composition and method for the use of stabilized chlorine dioxide as an antimicrobial agent against oral microorganisms for the treatment and prevention of halitosis and prevention of oral diseases, wherein the activation and release of chlorine dioxide from the composition a) occurs rapidly and without a period of induction, b) results from the oxidative reduction and consumption of amino acids and volatile sulfur compound precursors, and c) generates twice the available chlorine dioxide gas as that generated from simply lowering the pH of the composition. The preferred concentrations of stabilized chlorine dioxide in this invention are in the range of 0.005% to 2.0% (w/v) wherein the pH of the composition is initially lowered by a citrate and then stabilized by a peroxy compound.

Claims

1. (canceled)

2. A composition for reducing halitosis and diseases associated with oral bacteria and microorganisms resident in the oral cavity, said composition comprising: (a) stabilized chlorine dioxide in the range of above 0.1% to about 2.0% (w/v); and (b) a buffer composed to establish a pH for maintaining the stability of the stabilized chlorine dioxide, whereby the stabilized chlorine dioxide is capable of oxidatively consuming salivary biomolecules present in the oral cavity to produce chlorine dioxide gas for reducing growth and development of the oral bacteria and microorganisms.

3. The composition as set forth in claim 2 wherein the concentration of stabilized chlorine dioxide is approximately 0.4% (w/v).

4. The composition as set forth in claim 2 wherein said stabilized chlorine dioxide is an unreacted chlorite anion (ClO.sub.2.sup.−).

5. The composition as set forth in claim 4 wherein said composition is in a form selected from a group consisting of a wash, rinse, soak, paste, gel or aerosol spray.

6. A method for treatment of the oral cavity, said method comprising the steps of: (a) applying to the oral cavity a stabilized chlorine dioxide composition having a concentration in the range of above 0.1% to 2.0% (w/v) and a buffer composed to establish a pH for maintaining the stability of the stabilized chlorine dioxide; (b) mixing said stabilized chlorine dioxide and said buffer from step (a) with salivary biomolecules present in the oral cavity to generate chlorine dioxide for reducing growth and development of oral bacteria and microorganisms resident in the oral cavity.

Description

BRIEF DESCRIPTION OF FIGURES

[0037] FIG. 1, (a) and (b), illustrates the expanded 0.80-4.25 ppm regions of the 600.13 Mhz single-pulse .sup.1H NMR spectra of a human salivary supernatant specimen (pH value 6.78) acquired (a) prior to and (b) subsequent to treatment with oral rinse I according to the procedure outlined in the Materials and Methods section. Abbreviations: A. Acetate-CH.sub.3; Ala I and II, alanine-CH.sub.3 and —CH group proton respectively; Bu I, β-hydroxybutyrate proton γ-CH.sub.3 group protons; Bu II, III and IV, β-hydroxybutyrate β, β′, and α protons respectively (ABX coupling system); iso-But I and II, iso-butyrate-CH.sub.3 and —CH group protons respectively; n-But I, II and III, n-butyrate γ, β, and α protons respectively; Chol, choline-N.sup.+ (CH.sub.3).sub.3; Cit, Citrate-AB-CH.sub.2—CO.sub.2.sup.−; DMeN, dimethylamine-CH.sub.3; Eth I and II, ethanol-CH.sub.3 and —CH.sub.2 group protons respectively; Form, formate-H; Gly, glycine-CH; His I and II, histidine ABX system β protons; Lac I and II, lactate-CH.sub.3 and —CH protons respectively; Leu I, II, III and IV, leucine δ, γ, β, and α protons respectively; MeGu, methylguanidine-CH.sub.3; MeN, methylamine-CH.sub.3; Meth, methanol-CH.sub.3; N—Ac, spectral region for acetamido methyl groups of N-acetyl sugars; Phe I and II, phenylalanine ABX β protons; Prop I and II, propionate-CH.sub.3 and —CH.sub.2 group protons respectively; Pyr, pyruvate-CH.sub.3; Sar I and II, sarcosine-CH.sub.3 and —CH.sub.2 group protons respectively; Suc, succinate-CH.sub.2; Tau I and II, Taurine-CH.sub.2NH.sub.3.sup.+ and —CH.sub.2SO.sub.3.sup.− protons respectively; TMeN, trimethylamine-CH.sub.3, Tyr I and II, tyrosine ABX β protons; Tyr III, tyrosine ABX α proton; n-Val I and II, n-valerate δ and γ protons respectively.

[0038] FIG. 2 illustrates a plot of absorbance at 262 nm (A.sub.262) versus chlorite concentration for a series of calibration standards in the 1.60-8.00 mM concentration range

[0039] FIG. 3(a) illustrates a reversed-phase (RP) ion-pair (IP) chromatograms of a 1.00 mM chlorite standard solution. The retention time of ClO.sub.2.sup.− was 6.90 min.

[0040] FIG. 3(b) illustrates a reversed-phase (RP) ion-pair (IP) chromatograms of oral rinse I formulation (diluted ¼ with doubly-distilled water prior to analysis). The retention time of ClO.sub.2.sup.− was 6.90 min.

[0041] FIG. 3(c) illustrates a reversed-phase (RP) ion-pair (IP) chromatograms of a typical salivary supernatant sample (0.10 ml) pre-treated with 0.50 ml of the above oral rinse I. The retention time of ClO.sub.2.sup.− was 6.90 min.

[0042] FIG. 4 illustrates a plot of chlorite peak area (μV.Math.s.sup.−1) obtained from the HPLC analysis versus chlorite concentration for a series of chlorite calibration standards

DESCRIPTION OF THE INVENTION

[0043] This invention relates to the discovery through research of the composition for and methodology of generating of chlorine dioxide by a stabilized chlorine dioxide composition through the oxidatively consuming salivary biomolecules in the oral cavity and producing antimicrobial affects on oral bacteria and microorganisms concerned with halitosis and oral disease with the reduction of growth and development. Chlorine dioxide is known to be a strong oxidizer and is capable of oxidizing amino acids. The work of Lynch et al. proves so with the degradation of cysteine and methionine into pyruvate in the presence of an admixture of stable free radical species chlorine dioxide with chlorite anions (1997). This was confirmed with the following evidence of research suggesting oxidative consumptions of salivary biomolecules and interactions of stabilized chlorine dioxide as chlorite with human salivary biomolecules. The oxidative decarboxylation of salivary pyruvate by stabilized chlorine dioxide composition indicates a mechanism of action of the interaction of this invention with salivary biomolecules as an antimicrobial agent.

[0044] The specific mechanism of action of ‘stabilized’ chlorine dioxide (specifically, chlorite anion) on oral organisms and biomolecules has not been fully investigated. The present invention research evidence suggests that stabilized chlorine dioxide oxidatively consumes salivary biomolecules and creates products that may exert bactericidal and bacteriostatic effects on the oral bacterial cells which ultimately gives rise to cell death. These effects can lead to control over the formation of bacterial plaque and the adverse generation of malodorous volatile sulfur compounds, major contributors to oral diseases.

[0045] The purpose of researching the oxidentive consumption of salivary biomolecules this investigation was to determine: (1) the metabolic profile of human saliva and the capacity of salivary biomolecules to react with stabilized chlorine dioxide oral rinse, (2) the amount of chlorine dioxide generated from chlorite when the oral rinse is mixed with saliva, and how much chlorine dioxide is consumed or chlorite remains, and (3) an assay technique for monitoring chlorine dioxide activity in saliva, as well as determining the level of volatile sulfur compounds after being treated with a stabilized chlorine dioxide rinse. The oral rinse compositions included a concentration of 0.1% (w/v) and 0.4% (w/v) stabilized chlorine dioxide. These formulations are designated as oral rinse I and II, respectively.

[0046] This research suggested that the stabilized chlorine dioxide composition has the capacity to clinically alleviate oral malodor by the direct oxidative inactivation of volatile sulfur compounds and their amino acid precursors. These results also reveal a new mechanism of action of stabilized chlorine dioxide (chlorite), specifically its reaction with human salivary biomolecules to produce chlorine dioxide.

Materials and Methods

Spectrophotometric Determination of Chlorite Concentrations in Oral Rinse Formulations

[0047] For oral rinse I, 1.00 ml aliquots were diluted to a total volume of 3.00 ml with doubly-distilled water and electronic absorption spectra of these solutions were recorded on a Unicam UV-2 spectrophotometer in the 190-400 nm wavelength range. Similarly, 0.20 ml volumes of oral rinse II were diluted to a final volume of 3.00 ml with doubly-distilled water and electronic absorption spectra were also acquired in this manner. Chlorite concentrations were determined via measurement of its absorbance at 262 nm [ε=160 M.sup.−1 cm.sup.−1, as determined in this study]. A further series of these oral rinse solutions were pre-treated with the amino acid L-glycine (final concentration 2.00 mM) to remove hypochlorous acid/hypochlorite (HOCl/OCl.sup.−) and chlorine dioxide (ClO.sub.2.sup.•), the former generating glycine monochloroamine via equation A.

H.sub.3N.sup.+—CH.sub.2—CO.sub.2.sup.−+OCl.sup.−.fwdarw.Cl—NH—CH.sub.2—CO.sub.2.sup.−+H.sub.2O  (A)

[0048] Results acquired revealed that there were no differences between spectra obtained before and after glycine treatment, indicating that these potentially interfering, further oxohalogen oxidants were absent from the oral rinse formulations examined.

Volunteer Recruitment and Collection of Samples

[0049] A series of non-medically-compromised volunteers (n=20) without any form of active periodontal disease or active dental caries were recruited to the study. To avoid interferences arising from the introduction of exogenous agents into the oral environment, volunteers were requested to collect all saliva available, i.e., (‘whole’ saliva expectorated from the mouth) into a plastic universal tube immediately after waking in the morning on a pre-selected day.

[0050] Each volunteer was also requested to refrain completely from oral activities (i.e., eating, drinking, tooth-brushing, oral rinsing, smoking, etc.) during the short period between awakening and sample collection (ca. 5 min.). Each collection tube contained sufficient sodium fluoride (15 μmol.) to ensure that metabolites are not generated or consumed via the actions of micro-organisms or their enzymes present in whole saliva during periods of sample preparation and/or storage.

[0051] Saliva specimens were transported to the laboratory on ice and then centrifuged immediately (3,000 r.p.m for 15 min.) on their arrival to remove cells and debris, and the resulting supernatants were stored at −70° C. for a maximum duration of 18 hr. prior to analysis. The pH values of each supernatant were determined prior to .sup.1H NMR analysis.

Spectrophotometric Analysis of Residual (Unreacted) Chlorite Anion (ClO.sub.2.sup.−) in Oral Rinse/Salivary Supernatant Mixtures

[0052] An ATI Unicam UV-VIS UV-2 spectrophotometer was employed for the determination of residual chlorite in each of the salivary supernatants collected in order to determine its level of consumption by biomolecules therein on equilibration.

[0053] 0.09 ml aliquots of each salivary supernatant specimen were treated with 0.450 ml of oral rinse I. This mixture was thoroughly rotamixed and diluted to a final volume of 1.20 ml to yield an absorbance value of approximately 1 at 262 nm. The reference cell contained an equivalent volume of corresponding salivary supernatant diluted to a final volume of 1.20 ml with doubly-distilled H.sub.2O. Initially, scans were made over the wavelength range of 190-300 nm.

[0054] Since oral rinse II contained exactly four times the concentration of ClO.sub.2.sup.− [0.4% (w/v)], 0.10 ml aliquots of each salivary supernatant specimen were treated with 0.500 ml of this product, and once thoroughly rotamixed, a 0.135 ml aliquot of this mixture was diluted to a final volume of 1.20 ml with H.sub.2O. The reference cell contained 22.5 μl of salivary supernatant diluted to 1.20 ml with H.sub.2O.

[0055] ClO.sub.2.sup.− has a wavelength of maximum absorbance (λ.sub.max) at 262 nm (ε=160 M.sup.−1 cm.sup.−1) and therefore was readily detectable at the volumes (and hence concentrations of ClO.sub.2.sup.−) of each oral rinse added.

[0056] Where required, the pH value of samples were adjusted to a value of 1.00 and samples were then equilibrated at ambient temperature for a 24 hr. period (to ensure conversion of each mole of ClO.sub.2.sup.− remaining to 0.50 of an equivalent of ClO.sub.2.sup.•) in order to improve the sensitivity of this assay system [ClO.sub.2.sup.• has a λ.sub.max value in the visible region (360 nm) with ε=1,150 M.sup.−1 cm.sup.−1].

HPLC Monitoring of the Interaction of the Oral Rinse Oxohalogen Oxidants with Intact Human Saliva

[0057] The chlorite level remaining in each salivary supernatant sample was also determined using a novel high-performance liquid chromatographic (HPLC) technique employing a reversed-phase C18 column with the ion-pair reagent hexadecyl-trimethylammonium bromide (HTB) present in the mobile phase. The operating system utilised was a Waters Millennium HPLC system, consisting of a Waters 626 Pump, Waters 996 Photodiode Array Detector and a Waters in-line degasser remotely operated using Waters unique Millennium software.

[0058] Samples were prepared via the treatment of 0.10 ml volumes of saliva supernatants with 0.50 ml aliquots of ¼ diluted oral rinses I and II. Once thoroughly rotamixed, 10 μl aliquots of the resulting solutions were injected using a remotely-operated automated auto-sampler with injector onto a reversed-phase C18 ODS Column (4.6×75 mm). A Spherisorb S5-ODS 1 guard column was employed to remove any potential analytical column contaminants.

[0059] The mobile phase was de-gassed using an in-line degasser. The mobile phase consisted of 2% (w/v) borate/gluconate buffer with 2% (v/v) butan-1-ol and 12% (v/v) acetonitrile (final pH 7.2) and operated at a flow rate of 1.10 ml/min. The ion-pair reagent (Hexadecyl-trimethylammonium Bromide) was added at a final concentration of 50.00 mM in order to ensure that ClO.sub.2.sup.− is readily separated from interfering salivary components. This analyte was identified by comparisons of its peak's absorption spectrum generated by the photo-diode array detector (λ.sub.max. 262 nm) with that of an authentic chlorite standard.

Preparation of Human Salivary Supernatant Samples for .SUP.1.H NMR Analysis

[0060] Each individual salivary supernatant sample was divided into three equivalent portions (0.60 ml). In total, there were three separate specimen reaction mixtures: 3.0 ml of oral rinses I and II were added to the first and second salivary supernatant samples respectively, whilst the third served as an untreated control in which 3.0 ml of H.sub.2O was added to the original 0.6 ml volume of salivary supernatant. The samples were then thoroughly rotamixed to ensure a homogenous mixture and then equilibrated at 37° C. for a period of 30 s.

[0061] Samples were prepared by adding 0.05 ml of deuterium oxide (.sup.2H.sub.2O, providing a field frequency lock) and 0.05 ml of a 5.0 mM solution of sodium 3-trimethylsilyl [2,2,3,3-.sup.2H.sub.4] propionate [TSP, chemical shift reference (δ=0.00 ppm) and internal quantitative standard] in .sup.2H.sub.2O to a 0.60 ml volume of each sample examined.

[0062] Each sample was then subjected to multicomponent high resolution .sup.1H NMR analysis in order to identify the nature of salivary biomolecules which react with ClO.sub.2.sup.− and/or ClO.sub.2.sup.•. i.e., via oxidative consumption or otherwise, together with the products generated from such reaction systems.

.SUP.1.H NMR Measurements

[0063] One-dimensional (1-D) .sup.1H NMR spectra were acquired on a Bruker AMX-600 spectrometer (ULIRS, Queen Mary, University of London facility, U.K) operating at a frequency of 600.13 MHz and a probe temperature of 298 K. The intense water signal (δ=4.80 ppm) was suppressed by presaturation via gated decoupling during the delay between pulses.

[0064] Pulsing conditions for 1-D spectra acquired on salivary supernatant and oral rinse samples were: 128 free induction decays (FIDS); 16,384 data points; 3-7 μs pulses; 1.0 s pulse repetition rate. Line-broadening functions of 0.30 Hz were routinely utilised for the processing of experimental NMR data. Where present, the methyl group resonances of lactate (δ=1.330 ppm) and alanine (δ=1.481 ppm) served as secondary internal references for the control and oral rinse-treated salivary supernatant samples examined.

Results

.SUP.1.H NMR Analysis of Oral Rinse Formulations I and II

[0065] .sup.1H NMR spectra acquired on the oral rinse I formulation contained clear, prominent resonances ascribable to citrate [—CH.sub.2CO.sub.2.sup.− protons, δ=2.65 ppm (dd, AB coupling system)] which serves as a buffering agent, with lower intensity signals arising from acetate [—CH.sub.3 group, singlet (s) located at 1.92 ppm] and formate [.sup.−O.sub.2C—H singlet (s), δ=8.46 ppm]. Ethanol [—CH.sub.3 and —CH.sub.2OH group protons, δ=1.21(t) and 3.66(q) respectively] was also detectable at trace levels.

[0066] Spectra acquired on the oral rinse II product also contained resonances ascribable to citrate [—CH.sub.2CO.sub.2.sup.− protons, δ=2.65 ppm (dd, AB coupling system)] and lower intensity signals arising from trace levels of acetate [—CH.sub.3 group, singlet (s) located at 1.92 ppm] and formate [.sup.−O.sub.2C—H singlet (s), δ=8.46 ppm].

.sup.1H NMR Analysis of the Interaction of ClO.sub.2.sup.−-Containing Oral Rinse Formulations with Human Salivary Supernatant Specimens

[0067] 600 MHz .sup.1H NMR spectra were acquired for every salivary supernatant sample examined (i.e., a total of 60, 3 daily specimens collected from each of 20 human volunteers). A typical .sup.1H NMR spectrum of a human salivary supernatant sample is shown in FIG. 2(a); that of the same saliva specimen pre-treated with Oral Rinse I is displayed in FIG. 2(b). These .sup.1H NMR investigations [of the oxidative consumption of salivary biomolecules by oxohalogen oxidants present in Oral Rinses I and II tested (predominantly ClO.sub.2)] revealed that: [0068] 1. Pyruvate was oxidatively decarboxylated to acetate and CO.sub.2 [0069] 2. The volatile sulphur compound (VSC) precursor methionine was oxidised to its corresponding sulphoxide [0070] 3. A resonance ascribable to malodorous trimethylamine (s, δ=2.91 ppm) was reduced in intensity (a process presumably resulting in its transformation to trimethylamine oxide) [0071] 4. Tyrosine was oxidised (presumably to a quinone species) [0072] 5. The Glycine α-CH.sub.2 group resonance was reduced in intensity, an observation possibly attributable to its reaction with trace levels of hypochlorite/hypochlorous acid present in the oral rinses (generating mono- and/or dichloroamine species) [0073] 6. The concentrations of creatinine and 3-D-hydroxybutyrate were diminished following treatment with each oral rinse, an observation consistent with their oxidative consumption by oxohalogen species present therein. [0074] 7. Salivary taurine decreased in concentration post treatment. [0075] 8. Lactate-CH.sub.3 and —CH signals were diminished in intensity following treatment. [0076] 9. Resonances ascribable to lysine were reduced in intensity post-treatment.

[0077] With regard to these .sup.1H NMR analysis results acquired, the consumption of salivary methionine by chlorite is of much importance to oral hygiene and clinical periodontology since both CH.sub.3SH and H.sub.2S are generated from this amino acid via metabolic pathways operational in gram-negative micro-organisms. Hence, data acquired here indicates that the oral rinses examined have the capacity to clinically alleviate oral malodour via the direct oxidative inactivation of VSCs and their amino acid precursors.

[0078] As demonstrated here, the techniques employed are of much value concerning multicomponent assessments of the interactions of chlorite with human salivary biomolecules, and the oxidative decarboxylation of salivary pyruvate by this oxohalogen oxidant serves as an important example of this which may be of some relevance to its mechanisms of action.

Spectrophotometric Analysis of Chlorite Calibration Standards

[0079] Prior to spectrophotometric analysis of Oral Rinses I and II, the extinction coefficient of chlorite (ClO.sub.2.sup.−) was determined at its λ.sub.max value of 262 nm. This was conducted by analysing authentic ClO.sub.2.sup.− calibration standards (1.60-8.00 mM, Table 1 and FIG. 2). Each measurement was made in triplicate in order to ensure the reproducibility of data acquired. Plots of absorbance at 262 nm (A.sub.262) versus chlorite concentration were clearly linear: the extinction coefficient was determined as ε=160 M.sup.−1 cm.sup.−1, and the correlation coefficient (r) for the plot shown in Table 1 was 0.9955.

TABLE-US-00001 TABLE 1 Absorbance values at 262 nm for replicate (n = 3) determinations obtained for a series of chlorite calibration standards (1.60-8.00 mM) Concentration (mM) 1st 2nd 3rd 1.60 0.274 0.274 0.273 2.40 0.405 0.404 0.403 3.20 0.509 0.509 0.508 4.00 0.632 0.63 0.631 4.80 0.784 0.783 0.783 5.60 1.032 1.034 1.033 6.40 1.055 1.056 1.055 7.20 1.161 1.163 1.161 8.00 1.253 1.252 1.252

[0080] Treatment of the water diluent with up to 20% (v/v) ethanol exerted no influence on the final absorbance values obtained, an observation which confirmed that this potential contaminant exerted no influence on the spectrophotometric assay of chlorite performed in this manner (i.e., no reaction between these agents was noted under our experimental conditions).

Spectrophotometric Determination of the Consumption of Oral Rinse Chlorite by Human Salivary Supernatant Specimens

[0081] Following the establishment of ClO.sub.2.sup.−'s extinction coefficient (via the acquisition of electronic absorption spectra on a series of its calibration standards), difference spectrophotometric analysis of chlorite in each of the salivary supernatant/oral rinse mixtures was performed in order to determine its level of consumption by biomolecules therein on equilibration. In this manner, the decrease in absorbance at 262 nm observed following equilibration of the oral rinse formulations with human salivary supernatants according to the procedure outlined in methods was employed to estimate the level of oral rinse chlorite (ClO.sub.2.sup.−) consumption by this biofluid. Table 2(a) gives the concentrations of chlorite consumed (per ml of saliva) for reaction mixtures containing a 5:1 volume ratio of oral rinse:salivary supernatant.

TABLE-US-00002 TABLE 2(a) Spectrophotometric determination of the consumption of oral rinse ClO.sub.2.sup.− by human salivary supernatant samples (μmol. ClO.sub.2.sup.− consumed per ml of saliva). Patient Code Oral Rinse I Oral Rinse II J1 0.1640 0.1504 0.1776 0.0944 0.1168 0.1192 J2 0.0200 0.0096 0.0176 0.0360 0.0280 0.0472 J3 0.3040 0.3152 0.3040 0.3552 0.3024 0.3024 BR1 0.0400 0.0760 0.0600 0.0696 0.0584 0.1136 BR2 0.1136 0.0752 0.1008 0.1392 0.1136 0.1808 BR3 0.2968 0.2800 0.3096 0.0976 0.0504 0.0776 G1 0.0008 0.0104 0.0168 0.0584 0.1448 0.1168 G2 0.0168 0.0080 0.0112 0.1528 0.1664 0.1640 G3 0.0392 0.0624 0.0584 0.0864 0.0720 0.0920 U1 0.0200 0.0112 0.0200 0.0528 0.0360 0.0248 U2 0.0168 0.0040 0.0072 0.0168 0.0304 0.0392 U3 0.0168 0.0216 0.0144 0.4504 0.3888 0.4056 M1 0.0696 0.0728 0.0704 0.1000 0.1528 0.1280 M2 0.0072 0.0016 0.0080 0.2024 0.1504 0.1608 M3 0.0000 0.0048 0.0016 0.0192 0.0224 0.0224 L1 0.0064 0.0040 0.0128 0.0248 0.0024 0.0112 L2 0.0104 0.0064 0.0056 0.0416 0.0832 0.0696 L3 0.0296 0.0320 0.0352 0.0664 0.064 0.0608 SB1 0.1408 0.1576 0.1272 0.0720 0.0416 0.0664 SB2 0.1400 0.1496 0.1336 0.2888 0.3584 0.2776 SB3 0.0240 0.0240 0.0264 0.0224 0.0248 0.0336 I1 0.0336 0.0424 0.0296 0.1112 0.1336 0.1528 I2 0.0856 0.0752 0.0544 0.0448 0.0336 0.0248 I3 0.0264 0.0216 0.0240 0.072 0.0976 0.0808 R1 0.0376 0.0536 0.0368 0.0080 0.0224 0.0056 R2 0.0056 0.0016 0.0000 0.1000 0.0752 0.0888 R3 0.0056 0.0104 0.0104 0.0224 0.0112 0.0192 ZK1 0.0088 0.0096 0.0096 0.0664 0.0552 0.0608 ZK2 0.1032 0.1376 0.1248 0.0976 0.0752 0.1136 ZK3 0.0232 0.0192 0.0264 0.1168 0.0808 0.0832 V1 0.2000 0.2128 0.2264 1.4808 1.4888 1.4696 V2 0.0328 0.0408 0.0472 0.2168 0.1552 0.1976 V3 0.0704 0.0680 0.0672 0.7000 0.6528 0.6304 Z1 0.0120 0.0096 0.0128 0.0664 0.0528 0.0552 Z2 0.0240 0.0224 0.0184 0.0056 0.0024 0.0000 Z3 0.0232 0.0184 0.0104 0.0504 0.0472 0.0552 GG1 0.0344 0.0216 0.0328 0.2000 0.1752 0.1944 GG2 0.1400 0.1296 0.1296 0.2392 0.2584 0.2472 GG3 0.0088 0.0136 0.0104 0.0024 0.0136 0.008 N1 0.0056 0.0064 0.0040 0.1976 0.2080 0.2000 N2 0.0112 0.008 0.0048 0.0696 0.0752 0.0528 N3 0.0184 0.0200 0.0120 0.0112 0.0168 0.0056 ED1 0.0792 0.0576 0.0920 0.2752 0.2720 0.2448 ED2 0.3184 0.3352 0.3288 0.3168 0.4640 0.4808 ED3 0.0288 0.0224 0.0160 0.1080 0.1248 0.0608 AB1 0.0112 0.0232 0.0256 0.2112 0.1608 0.1080 AB2 0.0024 0.0032 0.0048 0.0584 0.1000 0.0944 AB3 0.008 0.0104 0.0072 0.0552 0.0696 0.0696 S1 0.2512 0.2736 0.2624 0.964 0.9832 1.0304 S2 0.1952 0.1728 0.1584 0.1472 0.1696 0.1056 S3 0.1176 0.1744 0.1440 0.5448 0.5776 0.5696 DG1 0.1104 0.1144 0.0880 0.0504 0.0392 0.0664 DG2 0.0192 0.0328 0.0208 0.0552 0.1360 0.0080 DG3 0.0088 0.0120 0.0096 0.0808 0.0832 0.0888 SG1 0.0336 0.0456 0.0544 0 0 0.0024 SG2 0.0744 0.0944 0.0656 0.1136 0.1080 0.1080 SG3 0.0144 0.0120 0.0120 0.1504 0.1168 0.1392 P1 0.0128 0.0112 0.0152 0.1112 0.1336 0.1304 P2 0.0176 0.0200 0.0248 0.0472 0.0392 0.0504 P3 0.0600 0.0504 0.0408 0.0640 0.1024 0.1472 Abbreviations: patient codes in the rows refer to volunteers, whilst columns represent oral rinse treatments, with three independent sampling days ‘nested’ within each treatment.
Multifactorial Analysis-of-Variance of Difference Spectrophotometric Data Involving the Determination of ClO.sub.2.sup.− Consumption by Salivary Biomolecules

[0082] Statistical analysis of data acquired regarding the difference spectrophotometric determination of ClO.sub.2.sup.− consumption by salivary biomolecules [i.e., multifactorial analysis-of-variance (ANOVA)] revealed highly significant differences between (1) the ClO.sub.2.sup.− content of each oral rinse investigated (p<<0.001), (2) volunteers (p<0.01) and (3) ‘days nested within volunteers’ (p<0.001). Indeed, estimates of the overall mean consumption of ClO.sub.2.sup.− determined for a reaction mixture containing a 5:1 (v/v) ratio of oral rinse:human salivary supernatant were 6.334×10.sup.−2 and 1.626×10.sup.−1 μmol. ClO.sub.2.sup.− per ml of salivary supernatant for Oral Rinses I and II respectively. The ‘between replicates’ mean square value was only 1.266×10.sup.−4, indicating a high level of reproducibility on repeat (triplicate) determinations conducted on each sample tested. The full ANOVA table is shown in Table 2(b).

TABLE-US-00003 TABLE 2(b) Multifactorial analysis-of-variance (ANOVA) table for data acquired from the study involving the difference spectrophotometric determination of ClO.sub.2.sup.− consumption by salivary biomolecules. Source of Variation d.f SS MS F p EMS (1) Between ClO.sub.2.sup.− 1 1.3839 1.3839 64.37 <<0.001 concentrations (Fixed Effect) (2) Between 19 6.5421 0.3443 2.54 <0.01 σ.sup.2 + 6σ.sub.o.sup.2 + 18σ.sup.2.sub.v Volunteers (Random Effect) (3) Between 40 5.4146 0.1354 6.30 <0.001 σ.sup.2 + 6σ.sub.o.sup.2 Sampling Days within Volunteers (Random Effect) (4) Error 295 6.3504 0.0215 σ.sup.2 (Residual) (5) Between 4 5.065 × 10.sup.−4 1.266 × 10.sup.−4 Replicates Total 359 19.6915 Abbreviations: d.f., degrees-of freedom; SS, sum of squares values; MS, mean square values; F, F variance ratio statistic; EMS, expected mean square.
Development of a Novel HPLC Method for Monitoring Oral Rinse Chlorite Consumption and its Oxidative Interaction with Salivary Biomolecules

[0083] In this section, the development of an HPLC method for the determination of ClO.sub.2.sup.• in human saliva specimens (i.e., prior and subsequent to its treatment with the oral rinse formulations) is described.

[0084] The chlorite level remaining in each salivary supernatant sample was determined using a high-performance liquid chromatographic (HPLC) technique employing a reversed-phase C18 column with the ion-pair reagent hexadecyl-trimethylammonium bromide (HTB) present in the mobile phase.

[0085] Experiments involving alteration of the ion pair reagent concentration from 5.00 to 50.00 mM showed that a concentration of 50.00 mM gave rise to a good resolution of ClO.sub.2.sup.− from salivary components in all samples investigated. Identification of the ClO.sub.2.sup.− peak was based on its retention time (6.9 min) and the diode-array spectrum of its HPLC peak (λ.sub.max 262 nm). Injection of authentic sodium chlorite calibration standards (1.00-10.00 mM) demonstrated a clear linear relationship between peak intensity and concentration. Typical chromatograms of a 1.00 mM chlorite standard solution, the oral rinse I formulation (diluted ¼ with doubly-distilled water prior to analysis) and a typical salivary supernatant sample (0.10 ml) pre-treated with 0.50 ml of the above oral rinse (I) are shown in FIGS. 3(a), (b) and (c) respectively. The retention time of ClO.sub.2.sup.− was 6.90 min.

[0086] Plots of chlorite peak area (Table 3) versus its concentration were clearly linear (FIG. 4).

TABLE-US-00004 TABLE 3 Area under chlorite peak (μV/sec.) values obtained via HPLC analysis of known chlorite calibration standards Concentration (mM) Mean value uV/sec 0.80 70833 69102 69879 1.60 151673 151878 153334 2.40 208530 209419 210975 3.20 259823 258413 259662 4.00 326322 326592 326771 4.80 394229 394023 394386 5.60 514239 510086 513058 6.40 535511 535418 530565 7.20 586871 592830 585209 8.00 628810 628254 622356

CONCLUSIONS

[0087] Results acquired on the consumption of (relatively) simple amino acids such as glycine, alanine and taurine by the oral rinse tested here (predominantly containing ClO.sub.2.sup.− as an oxidant) are explicable by previous investigations conducted on the kinetics and mechanisms of the reactions of such biomolecules with oxyhalogen oxidants (including ClO.sub.2.sup.−) as outlined below.

[0088] Of much relevance to the substantial extent of salivary taurine consumption by the oral rinses investigated in the studies are experiments reported by Chinake and Simoyi (1997) on the oxidation of this β-amino acid by ClO.sub.2.sup.− (at neutral to acidic pH values, i.e., those which are relevant to the oral environment). Indeed, the stoichiometry of this reaction system was found to involve the consumption of 3 molar equivalents of ClO.sub.2.sup.− per mole of taurine to generate 1 of taurine's N-monochloroamine [Cl(H)NCH.sub.2CH.sub.2SO.sub.3H] and 2 of ClO.sub.2.sup.• (the production of N-monochlorotaurine is rapid when expressed relative to that of ClO.sub.2.sup.• accumulation); at the lower pH values investigated, N-monochlorotaurine disassociated to taurine and N-dichlorotaurine. An important characteristic of this reaction system involves a significant induction period in which both HOCl and the reactive intermediate H(OH)NCH.sub.2CH.sub.2SO.sub.3H are produced, a process leading to the formation of N-chlorotaurine and ClO.sub.2.sup.• autocatalytically. As expected for redox reactions involving ClO.sub.2.sup.−, this autocatalysis is mediated by a Cl.sub.2O.sub.2 intermediate species, and interestingly, taurine's C—S bond is not cleaved, despite the availability of the powerful oxidant HOCl.

[0089] Hence, these previously reported studies clearly explain the substantial .sup.1H NMR-detectable reductions in salivary taurine observed on treatment of human salivary supernatant specimens with the tested oral rinse ClO.sub.2.sup.−. They also indicate that the oral rinse-induced oxidative consumption of a range of α-amino acids present in this biofluid also detected in this investigation, specifically free (non-protein-incorporated) alanine, arginine, aspartate, cysteine, glutamate, glutamine, histidine, hydroxyproline, isoleucine, leucine, lysine, methionine, ornithine, phenylalanine, proline, tyrosine and valine, also proceed via this mechanism.

[0090] However, since many N.sup.α-monochloroamines generated in this manner are unstable at physiological temperature (37° C.) (Hazen et. al. (1998)), and decompose to corresponding aldehydes (equation 1), and hence further investigations focused on the detection and quantification of such species corresponding to the side-chains of α-amino acids (e.g., formaldehyde from salivary glycine, acetaldehyde from alanine, etc.) are required in order to demonstrate this.

Cl(H)N—CHR—CO.sub.2.sup.−+H.sub.2O.fwdarw.RCHO+NH.sub.3+CO.sub.2+Cl.sup.−  (1)

[0091] Interestingly, it is well known that aldehydes act as potent microbicidal agents, and hence those derived from the above processes may also exert this activity in the oral environment. Indeed, a 2.0% (w/v) solution of this agent is frequently employed as a disinfectant (Follente et. al.).

[0092] Similarly, the oxidative consumption of γ-aminobutyrate (GABA) noted here is likely to proceed via a similar mechanism. However, the amino acids cysteine, methionine and tyrosine, each with redox-active side-chains can, of course, also be oxidatively modified by ClO.sub.2.sup.− (and also ClO.sub.2.sup.• and HOCl/OCl.sup.− produced via its reaction with these and/or further α-amino acids, together with GABA and particularly taurine) to cysteine sulphonate (and cysteine), methionine sulphoxide (equation 2) and a tyrosine-derived quinone species respectively.

H.sub.3N.sup.+CH(CH.sub.2CH.sub.2SCH.sub.3)CO.sub.2.sup.−+ClO.sub.2.sup.−.fwdarw.H.sub.3N.sup.+CH(CH.sub.2CH.sub.2SOCH.sub.3)CO.sub.2.sup.−+OCl.sup.−  (2)

[0093] With regard to the oxidative consumption of salivary α-keto acid anions, particularly pyruvate and α-ketoglutarte, by ClO.sub.2.sup.− present in the tested oral rinses, which was also observed in our investigations, it has been previously noted that an intense green Cl.sub.2/OCl.sup.− colouration is generated on reaction of ClO.sub.2.sup.− with pyruvate (equation 3) [Lynch et. al. 1997]. Hence, such reaction systems clearly generate HOCl/OCl.sup.− which can, of course, subsequently produce N-monochloro- and -dichloroamines from free or, in selected cases, protein-incorporated amino acids, the former decomposing to corresponding aldehydes under physiological conditions.

CH.sub.3COCO.sub.2.sup.−+ClO.sub.2.sup.−.fwdarw.CH.sub.3CO.sub.2.sup.−+CO.sub.2+OCl.sup.−  (3)

[0094] Therefore, it should be noted that the production of reactive HOCl/OCl.sup.− during an induction period observed during the reaction of ClO.sub.2.sup.− with the β-amino acid taurine (Chinake and Simoyi (1997)) (and also presumably the salivary α-amino acids and γ-aminobutyrate consumed on reaction with tested oral rinse ClO.sub.2.sup.−) will also serve to further reduce the amino acid concentrations of human saliva. Indeed, even if this mechanistic process only proceeds in the reactions of selected free amino acids with ClO.sub.2.sup.− (or those located at the N-termini of salivary proteins), the HOCl/OCl.sup.− generated will, of course, be available to react with a much wider range of such HOCl/OCl.sup.− ‘scavenger’ species in a (relatively) unselective manner to form N.sup.α-monochloro- and dichloroamines, together with N.sup.ε-monochloro- and -dichloroamines in lysine residues (either free or protein-incorporated). As noted above, specific aldehydes arising from the decomposition of their parent amino acid N.sup.α-monochloroamine precursors will serve as valuable indicators of the activity of HOCl/OCl.sup.− arising from these reaction systems (RCHO, where R represents an amino acid side-chain moiety).

[0095] Aldehydes produced from the interaction of HOCl/OCl.sup.− with salivary α-amino acids and the decomposition of the primary N.sup.α-monochloroamine products can also react with ClO.sub.2.sup.−, and the oxidation of formaldehyde (HCHO) by this oxyhalogen oxidant was critically examined by Chinake et. al. (1998) in both mildly acidic and alkaline media. This reaction gave rise to CO.sub.2 and ClO.sub.2.sup.• as products, the latter in virtually quantitative yield, and was autocatalytic with respect to hypochlorous acid/hypochlorite (HOCl/OCl.sup.−). Indeed, the primary phase of the process generated HOCl which facilitated (catalysed) the production of ClO.sub.2.sup.• and the additional oxidation of formic acid/formate (HCO.sub.2H/HCO.sub.2.sup.−); ClO.sub.2.sup.• rapidly accumulated in view of its (relative) lack of reactivity towards both HCHO and HCO.sub.2H/HCO.sub.2.sup.−. Although with excess HCHO the stoichiometry of this process was determined to be 3ClO.sub.2.sup.−+HCHO.fwdarw.HCO.sub.2H+2ClO.sub.2 (aq.).sup.•+Cl.sup.−+2H.sub.2O, when large excesses of ClO.sub.2.sup.− were present [as, of course, expected in the case of 5:1 (v/v) mixtures of tested oral rinses:human salivary supernatant], the stoichiometric profile involved in the consumption of 6 molar equivalents of ClO.sub.2.sup.− per mole of HCHO to generate 4 of ClO.sub.2.sup.•, 2 of Cl.sup.− and 1 of CO.sub.2.

[0096] With regard to the oral rinse-mediated decrease in the intensities of salivary cysteine resonances observed here (and also in previously-conducted chemical model studies (Lynch et. al., 1997), Darkwa et. al. (2003) investigated the oxidative consumption of N-acetylcysteine by ClO.sub.2.sup.−, and found that the final product generated from this reaction system was N-acetylsulphonate and that the process had a stoichiometry of 3ClO.sub.2.sup.−+2RSH.fwdarw.3Cl.sup.−+2RSO.sub.3H; as expected, there was no evidence for the production of N-chloroamine derivatives. This oxidation proceeds via a mechanism involving a stepwise S-oxygenation process involving the consecutive generation of sulphenic and sulphonic acid adducts. Intriguingly, a notable characteristic of the reaction is the rapid, immediate formation of chlorine dioxide (ClO.sub.2.sup.•) without a monitorable induction period since oxidation of the thiol by this oxyhalogen free radical species is sufficiently slow for it to accumulate without such a time lag which, in general, represents a characteristic of the oxidation of organosulphur compounds by ClO.sub.2.sup.−. A full description of the ‘global’ dynamics of this system involves 8 reactions in a truncated mechanism.

[0097] In conclusion, evidence provided in our investigations clearly demonstrate that the generation of ClO.sub.2.sup.• from ClO.sub.2.sup.− in the oral environment is not entirely dependent on entry of the latter into acidotic environments therein (equations 4 and 5, the pK.sub.a value of the ClO.sub.2.sup.−/HClO.sub.2 system being 2.31 (Lynch et al. 1997)). Although the mean pH value of this biofluid is ca. 7 when unchallenged with oral stimuli (i.e., ‘resting’), the consumption of relatively large volumes of beverages of lower pH value (ca. pH 4) can clearly exert a significant influence on this parameter. However, it should also be noted that the pH value of primary root caries lesions can approach a limit of 4.5, and therefore this represents an environment in which there are expected to be marked elevations in the level of HClO.sub.2 generated (i.e., from 0.0020% at pH 7.00 to 0.64% of total available oxyhalogen oxidant at pH 4.50), although it should be noted that, in view of the pK.sub.a value of the ClO.sub.2.sup.−/HClO.sub.2 couple, this value still remains very low when expressed relative the total amount of oxyhalogen oxidant available (the remainder being ClO.sub.2.sup.− in the absence of alternative means of producing ClO.sub.2.sup.•, or HOCl/OCl.sup.−, from the interaction of ClO.sub.2.sup.− with α-, β- and γ-amino acids available). Of course, from the stoichiometry of equation 5, 2 molar equivalents of ClO.sub.2.sup.• are generated per 4 of HClO.sub.2, and hence the above figures for HClO.sub.2 generation represent double that of the total ClO.sub.2.sup.• producible (i.e., maximum percentages of 0.0010 and 0.32% of total oxyhalogen oxidant at pH values of 7.00 and 4.50 respectively). Clearly, the rate of ClO.sub.2.sup.• generation from HClO.sub.2 should also be considered in view of the short oral rinse-salivary supernatant equilibration time involved in our studies.

ClO.sub.2.sup.−+H.sup.+.fwdarw.HClO.sub.2(pK.sub.a=2.31)  (4)

4HClO.sub.2.fwdarw.2ClO.sub.2.sup.•+ClO.sub.3.sup.−+Cl.sup.−+H.sub.2O  (5)