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Handheld Device Adapted to Smartphone Cameras for the Measurement of Sodium Ion Concentrations at Saliva-Relevant Levels via Fluorescence

School of Biological and Health Systems Engineering, Ira A. Fulton Schools of Engineering, Arizona State University, Tempe, AZ 85287, USA
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Academic Editor: Anthony Guiseppi-Elie
Bioengineering 2015, 2(2), 122-138; https://doi.org/10.3390/bioengineering2020122
Received: 27 March 2015 / Revised: 30 April 2015 / Accepted: 25 May 2015 / Published: 2 June 2015
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. View Full-Text
Keywords: smartphone; saliva; sodium ions; fluorescence; oblate spheroid; non-axially-symmetric focusing; low-resource settings smartphone; saliva; sodium ions; fluorescence; oblate spheroid; non-axially-symmetric focusing; low-resource settings
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Lipowicz, M.; Garcia, A. Handheld Device Adapted to Smartphone Cameras for the Measurement of Sodium Ion Concentrations at Saliva-Relevant Levels via Fluorescence. Bioengineering 2015, 2, 122-138.

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