A complete lab-made point of care device for non-immunological electrochemical determination of cortisol levels in salivary samples

Abstract

In this work, we describe a portable and microfluidic electrochemical device for cortisol determination in saliva samples. The non-immunological methodology was developed using a nickel modified screen-printed electrode coupled to a microfluidic platform obtained by 3D printing. The lab-made screen-printed electrodes were based on a conductive ink obtained from nail polish and graphite, in an optimized proportion of 70:30 % (w / w), and appropriate solvent. Amperometric measurements were performed by a lab-made portable electrochemical device, PotSensE, based on the Texas Instruments LMP91000 chip as a front-end analog device and the Raspberry Pi as a controller. Under optimized conditions, an analytical curve with a linear dynamic range from 0.25 to 25.0 μmol L−1 of cortisol was obtained, with the calculated limits of detection and quantification of 74.0 and 240 nmol L-1, respectively. Analysis of salivary cortisol from artificial and natural spiked samples was possible, ranging from good recovery values. As a proof-of-concept, the lab-made setup was employed as a POC-like device, showing the application potential with good recovery values for the adopted methodology.