Determination of progesterone in saliva using an electrochemical immunosensor and a COTS-based portable potentiostat

Highlights: • Reliable determination of progesterone (P4) in undiluted saliva with a disposable immunosensor. • Portable device/potentiostat constructed with commercial-off-the-shelf (COTS) components. • Fast (45 min) and sensitive determination of P4 using amperometry in stirred solutions or drops of quiescent solutions. • Determination of endogenous P4 in saliva with highly variable contents of the target hormone. -- Abstract: This paper describes the reliable determination of progesterone (P4) in undiluted saliva making use of a disposable amperometric immunosensors implemented on low-cost and portable device/potentiostat constructed with commercial-off-the-shelf (COTS) components. The immunosensor allows the fast (45 min), selective and sensitive determination (5 pg mL⁻¹ LOD) of P4 using amperometry in stirred solutions. The immunosensor was coupled to the COTS-based potentiostat and amperometry was made into drops of quiescent solutions. No significant differences were apparent between the analytical performance achieved with the immunosensor for P4 using both a conventional and the COST-based potentiostats. The practical applicability of the immunosensor coupled with the COTS-based potentiostat was demonstrated by determining the endogenous P4 content in different undiluted saliva samples with highly variable endogenous contents of the target hormone. The obtained results were in good agreement with those provided by the conventional ELISA methodology and with the contents reported in the literature for samples with similar characteristics. This validated the combined device for the reliable and minimally invasive determination of the target hormone involving a very simple protocol and taking only 45 min.