HPLC analysis of some sulphur compounds in saliva: comparison between healthy subjects and periodontopathic patients

Development of analytical methods to study the salivary metabolome: impact of the sampling

Advances in metabolomics have allowed the identification and characterization of saliva metabolites that can be used as biomarkers. However, discrepancies can be noted with the content of the same biomarker being increased or decreased for a given disease. Differences in the way saliva is collected, stored, and/or treated could cause these discrepancies. Indeed, there is no standardized method for saliva sampling and analysis. In this work, two chromatographic modes were used, i.e., RP-LC and HILIC both coupled to MS used in positive and negative ionization modes. The analytical conditions were optimized with a mixture of 90 compounds naturally present in saliva, representative of the wide range of molecular mass and polarity of salivary metabolites and being described as having a differential expression in various pathologies. These four methods were applied to the analysis of saliva samples collected by spitting, aspiration, or Salivette® with or without prior rinsing of the mouth. Rinsing had an effect on some metabolite concentrations. As it can induce an additional parameter of variability to the sampling, it seems therefore preferable to use methods without rinsing while effects of these parameters on the metabolites are investigated. Saliva obtained by spitting and aspiration gave statistically equivalent results for 84% of the metabolites studied. Conversely, Salivette® gave different results since the majority of the metabolites chosen for the study were not quantified in the samples. The Salivette® does not seem therefore to be a suitable sampling method for an untargeted analysis of the salivary metabolome, unlike aspiration and spitting.

Molecular Probes, Chemosensors, and Nanosensors for Optical Detection of Biorelevant Molecules and Ions in Aqueous Media and Biofluids

Synthetic molecular probes, chemosensors, and nanosensors used in combination with innovative assay protocols hold great potential for the development of robust, low-cost, and fast-responding sensors that are applicable in biofluids (urine, blood, and saliva). Particularly, the development of sensors for metabolites, neurotransmitters, drugs, and inorganic ions is highly desirable due to a lack of suitable biosensors. In addition, the monitoring and analysis of metabolic and signaling networks in cells and organisms by optical probes and chemosensors is becoming increasingly important in molecular biology and medicine. Thus, new perspectives for personalized diagnostics, theranostics, and biochemical/medical research will be unlocked when standing limitations of artificial binders and receptors are overcome. In this review, we survey synthetic sensing systems that have promising (future) application potential for the detection of small molecules, cations, and anions in aqueous media and biofluids. Special attention was given to sensing systems that provide a readily measurable optical signal through dynamic covalent chemistry, supramolecular host-guest interactions, or nanoparticles featuring plasmonic effects. This review shall also enable the reader to evaluate the current performance of molecular probes, chemosensors, and nanosensors in terms of sensitivity and selectivity with respect to practical requirement, and thereby inspiring new ideas for the development of further advanced systems.

Tween 20-capped gold nanoparticles for selective extraction of free low-molecular-weight thiols in saliva followed by capillary electrophoresis with contactless conductivity detection

Low-molecular-weight thiols are widely present in human fluids, and are regarded as a kind of potential broad-spectrum evaluation indicators for some clinical diseases. In this work, gold nanoparticles capped with Tween 20 were used for purification and microextraction of the main free thiols (cysteine, homocysteine, glutathione and methionine) in saliva based on Au-S bond formation. Ultrasound further sped up the releasing of the target analytes, and the releasing time needed was only 10 min, and the required sample volume was only 40 µL. The desorption solution could be directly injected for electrophoretic analysis without derivatization, and field-amplified sample stacking of electrophoretic online enrichment technology further improved the detection sensitivity. The synergistic enrichment effect made the enrichment factors of four analytes reach 1119-2067 times. This developed method was applied for the analyses of saliva samples of healthy volunteers. Acceptable sensitivity (LODs: 0.15-1.5 ng mL^-1) and recoveries (97.6-116%) were obtained in the saliva sample matrix. This proposed method provides an alternative for the sensitive detection of low-molecular-weight thiols in noninvasive body fluids, which has potential application prospect in the preliminary noninvasive diagnosis of diabetes, cardiovascular diseases, etc.

Selective electrochemical determination of cysteine with a cyclotricatechylene modified carbon electrode

We report the selective electrochemical detection of cysteine in the presence of homocysteine and glutathione with the use of an electrode modified with cyclotricatechylene (CTC).

Salivary thiols and enzyme markers of cell damage in periodontal disease

OBJECTIVES

Recent studies describe the potential use of biochemical markers in the evaluation of the severity of periodontitis; moreover, patients suffering from periodontitis frequently complain of halitosis (breath malodour), mainly depending on volatile compounds (e.g. hydrogen sulphide, methyl mercaptan, etc.) produced by anaerobic metabolism of oral bacteria and involving sulphur-containing amino acids. In this study, salivary sulphur compounds, such as cysteine, cysteinylglycine and glutathione and some markers of cellular damage (lactate dehydrogenase and aspartate amino transferase), were measured in periodontitis patients and correlated with the periodontal probing pocket's depth.

DESIGN AND METHODS

Twenty-two periodontitis patients and forty control subjects were studied for the salivary activities of lactate dehydrogenase and aspartate aminotransferase and cysteine, cysteinylglycine and glutathione concentrations. The periodontitis patients were divided into two subgroups based on the severity of periodontal disease, expressed as median periodontal probing pocket depth (> or <5 mm). Enzyme activities were measured by using an automated clinical analyzer; cysteine, cysteinylglycine and glutathione concentrations were measured by HPLC equipped with fluorescence detector.

RESULTS

A statistically significant increase of the salivary parameters level (cysteine, cysteinylglycine, glutathione, aspartate aminotransferase and lactate dehydrogenase) was found in the patient subgroup with periodontal probing pocket depth >5 mm, the salivary cysteine concentrations showing the most significant correlation.

CONCLUSIONS

Salivary cysteine, a direct precursor of hydrogen sulphide, could be considered reliable markers for the oral tissue damage severity in periodontitis patients.

Analysis of glutathione and glutathione disulfide in human saliva using hydrophilic interaction chromatography with mass spectrometry

A sensitive method for the determination of glutathione (GSH) and glutathione disulfide (GSSG) in human saliva was developed and validated. GSH was captured and stabilized by the addition of N-ethylmaleimide (NEM). Solid-phase extraction (SPE) using an Oasis MAX extraction cartridge was employed for sample preparation and analysis was performed on a Shimadzu LCMS-2010 A that was operated in the single ion monitoring mode using positive ion electrospray ionization (ESI) as the interface. The monitored ion for GSH-NEM was m/z 433 and that for GSSG was m/z 613. Chromatography was carried out on an Atlantis HILIC silica column (150 mm x 2.1 mm, 5 microm) with acetonitrile and formate buffer as the mobile phase at the flow rate of 0.2 ml/min. The calibration curve was linear over the range of 0.1-100 microM for GSH-NEM. The extraction recoveries of GSH-NEM spiked at concentrations of 25 and 50 microM were 97.1 and 104.4%, respectively. Similar results were obtained for GSSG. The newly developed hydrophilic interaction chromatography with mass spectrometry (HILIC/MS) method showed superior sensitivity for the determination of GSH and GSSG in human saliva samples.