All-solid-state blood calcium sensors based on screen-printed poly(3,4-ethylenedioxythiophene) as the solid contact

An all-solid-state sensor based on screen-printing technique for rapid blood calcium test was studied. The sensor consists of a thick film calcium ion-selective electrode and a pseudo-reference electrode. Poly(3,4-ethylenedioxythiophene) (PEDOT) doped with poly(styrenesulfonate) (PSS) was screen-printed on carbon paste electrodes as internal solid contacts for both the ion-selective and reference electrodes. PVC membranes with and without neutral carrier ETH129 were coated on the PEDOT (PSS) layer to form calcium ion-selective and pseudo-reference electrodes, respectively. The properties of screen-printed PEDOT (PSS) film on carbon paste electrode were studied by electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV) methods. The response time of the calcium sensors was 15 s while less than 15 μL sample was applied. And the sensitivity was 30.0 ± 1.0 mV per decade, while the potentiometric log selectivity coefficients were −3.80, −3.35 and −4.60 for Na+, K+ and Mg2+. Other properties of the calcium sensors were evaluated, including the temperature effect, repeatability, reproducibility and stability. The testing results with the calcium sensors were compared with those with a routine hospital electrolyte analyzer. The clinical trial results reveal that the all-solid-state calcium sensor is promising for the point of care testing.