Low-cost, facile droplet modification of screen-printed arrays for internally validated electrochemical detection of serum procalcitonin

This manuscript presents the design and facile production of screen-printed arrays (SPAs) for the internally validated determination of raised levels of serum procalcitonin (PCT). The screen-printing methodology produced SPAs with six individual working electrodes that exhibit an inter-array reproducibility of 3.64% and 5.51% for the electrochemically active surface area and heterogenous electrochemical rate constant respectively. The SPAs were modified with antibodies specific for the detection of PCT through a facile methodology, where each stage simply uses droplets incubated on the surface, allowing for their mass-production. This platform was used for the detection of PCT, achieving a linear dynamic range between 1 and 10 ng mL^-1 with a sensor sensitivity of 1.35 × 10^-10 NIC%/ng mL^-1. The SPA produced an intra- and inter-day %RSD of 4.00 and 5.05%, with a material cost of £1.14. Internally validated human serum results (3 sample measurements, 3 control) for raised levels of PCT (>2 ng mL^-1) were obtained, with no interference effects seen from CRP and IL-6. This SPA platform has the potential to offer clinicians vital information to rapidly begin treatment for "query sepsis" patients while awaiting results from more lengthy remote laboratory testing methods. Analytical ranges tested make this an ideal approach for rapid testing in specific patient populations (such as neonates or critically ill patients) in which PCT ranges are inherently wider. Due to the facile modification methods, we predict this could be used for various analytes on a single array, or the array increased further to maintain the internal validation of the system.