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Start Over Topic viscosity Journal theranostics
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1. Development of Paper-Based Analytical Devices for Minimizing the Viscosity Effect in Human Saliva.

Author

Noiphung J, Nguyen MP, Punyadeera C, Wan Y, Laiwattanapaisal W, and Henry CS

Subjects
Australia, Humans, Hydrogen-Ion Concentration, Sensitivity and Specificity, Chemistry Techniques, Analytical instrumentation, Nitrites analysis, Paper, Saliva chemistry, Specimen Handling methods, Viscosity
Abstract

Rationale: Saliva as a sample matrix is rapidly gaining interest for disease diagnosis and point-of-care assays because it is easy to collect (non-invasive) and contains many health-related biomarkers. However, saliva poses particular problems relative to more common urine and blood matrices, which includes low analyte concentrations, lack of understanding of biomolecule transportation and inherent viscosity variability in human samples. While several studies have sought to improve assay sensitivity, few have addressed sample viscosity specifically. The goal of this study is to minimize the effect of sample viscosity on paper-based analytical devices (PADs) for the measurement of pH and nitrite in human saliva. Methods: PADs were used to measure salivary pH from 5.0 to 10.0 with a universal indicator consisting of chlorophenol red, phenol red and phenolphthalein. Nitrite determination was performed using the Griess reaction. Artificial saliva with viscosity values between 1.54 and 5.10 mPa∙s was tested on the proposed PAD. To ensure the proposed PADs can be tailored for use in-field analysis, the devices were shipped to Australia and tested with human specimens. Results: Initial experiments showed that viscosity had a significant impact on the calibration curve for nitrite; however, a more consistent curve could be generated when buffer was added after the sample, irrespective of sample viscosity. The linear range for nitrite detection was 0.1 to 2.4 mg/dL using the improved method. The nitrite measurement in artificial saliva also showed a good correlation with the standard spectrophotometry method ( p =0.8484, paired sample t -test, n=20). Measured pH values from samples with varying viscosities correlated well with the results from our pH meter. Conclusions: The inherent variation of salivary viscosity that impacts nitrite and pH results can be addressed using a simple washing step on the PAD without the need for complex procedures., Competing Interests: Competing Interests: The authors have declared that no competing interest exists.

Published
2018
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2. Development of Paper-Based Analytical Devices for Minimizing the Viscosity Effect in Human Saliva

Author

Michael P. Nguyen, Wanida Laiwattanapaisal, Julaluk Noiphung, Charles S. Henry, Yunxia Wan, and Chamindie Punyadeera

Subjects
Paper, Calibration curve, Inherent viscosity, Medicine (miscellaneous), 02 engineering and technology, 01 natural sciences, pH meter, Sensitivity and Specificity, Chemistry Techniques, Analytical, Specimen Handling, chemistry.chemical_compound, Viscosity, Universal indicator, Griess test, oral cancer biomarkers, Nitrite Measurement, Humans, Nitrite, Saliva, Paper-based analytical devices, nitrite, Pharmacology, Toxicology and Pharmaceutics (miscellaneous), Nitrites, Chromatography, 010401 analytical chemistry, Australia, pH testing, Hydrogen-Ion Concentration, 021001 nanoscience & nanotechnology, 0104 chemical sciences, chemistry, saliva analysis, 0210 nano-technology, Research Paper
Abstract

Rationale : Saliva as a sample matrix is rapidly gaining interest for disease diagnosis and point-of-care assays because it is easy to collect (non-invasive) and contains many health-related biomarkers. However, saliva poses particular problems relative to more common urine and blood matrices, which includes low analyte concentrations, lack of understanding of biomolecule transportation and inherent viscosity variability in human samples. While several studies have sought to improve assay sensitivity, few have addressed sample viscosity specifically. The goal of this study is to minimize the effect of sample viscosity on paper-based analytical devices (PADs) for the measurement of pH and nitrite in human saliva. Methods : PADs were used to measure salivary pH from 5.0 to 10.0 with a universal indicator consisting of chlorophenol red, phenol red and phenolphthalein. Nitrite determination was performed using the Griess reaction. Artificial saliva with viscosity values between 1.54 and 5.10 mPa∙s was tested on the proposed PAD. To ensure the proposed PADs can be tailored for use in-field analysis, the devices were shipped to Australia and tested with human specimens. Results : Initial experiments showed that viscosity had a significant impact on the calibration curve for nitrite; however, a more consistent curve could be generated when buffer was added after the sample, irrespective of sample viscosity. The linear range for nitrite detection was 0.1 to 2.4 mg/dL using the improved method. The nitrite measurement in artificial saliva also showed a good correlation with the standard spectrophotometry method (p=0.8484, paired sample t-test, n=20). Measured pH values from samples with varying viscosities correlated well with the results from our pH meter. Conclusions : The inherent variation of salivary viscosity that impacts nitrite and pH results can be addressed using a simple washing step on the PAD without the need for complex procedures.

Published
2018