Abstract
The use of saliva sampling as a minimally-invasive means for drug testing and monitoring physiology is a subject of great interest to researchers and clinicians. This study describes a new optical method based on non-axially symmetric focusing of light using an oblate spheroid sample chamber. The device is simple, lightweight, low cost and is easily attached to several different brands/models of smartphones (Apple, Samsung, HTC and Nokia) for the measurement of sodium ion levels at physiologically-relevant saliva concentrations. The sample and fluorescent reagent solutions are placed in a specially-designed, lightweight device that excludes ambient light and concentrates 470-nm excitation light, from a low-power photodiode, within the sample through non-axially-symmetric refraction. The study found that smartphone cameras and post-image processing quantitated sodium ion concentration in water over the range of 0.5–10 mM, yielding best-fit regressions of the data that agree well with a data regression of microplate luminometer results. The data suggest that fluorescence can be used for the measurement of salivary sodium ion concentrations in low-resource or point-of-care settings. With further fluorescent assay testing, the device may find application in a variety of enzymatic or chemical assays.
Original language | English (US) |
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Pages (from-to) | 122-138 |
Number of pages | 17 |
Journal | Bioengineering |
Volume | 2 |
Issue number | 2 |
DOIs | |
State | Published - Jun 2015 |
Keywords
- Fluorescence
- Low-resource settings
- Non-axially-symmetric focusing
- Oblate spheroid
- Saliva
- Smartphone
- Sodium ions
ASJC Scopus subject areas
- Bioengineering