OFF-ON on-the-fly aptassay for rapid and accurate determination of procalcitonin in very low birth weight infants with sepsis suspicion

A fast and reliable OFF-ON micromotors (MM)-based aptassay for rapid, sensitive, and accurate determination of procalcitonin (PCT) as one of the leading neonatal sepsis biomarkers in very low birth weight infants’ serum samples is proposed. MM were composed of three specific functional layers: graphene oxide (GO) as sensing layer, Ni for magnetic guidance and platinum nanoparticles (PtNPs) as catalytic layer for self-propulsion (MMGO/Ni/PtNPs). The OFF-ON strategy relies on the binding of the aptamer tagged with alexa-405 as fluorescent label (AptPCT, λem=447 nm) onto the GO outer layer of the MM (GOMM) to induce its fluorescence quenching (GOMM-AptPCT, OFF state); which is next recovered due to selectively binding of the aptamer to the PCT and their separation from the GOMM surface (PCT-AptPCT, ON state). The fast OFF-ON on-the-fly aptassay allowed in just 5 min a highly selective and sensitive (LOD = 0.01 ng mL−1) PCT determination in clinical samples from very low birth weight infants with sepsis suspicion, using only 25 µL of sample in a clinically relevant range of concentrations (0.03–1280 ng mL−1). The high concordance between the PCT levels obtained by our MMGO/Ni/PtNPs-based aptassay and those obtained by the Hospital, demonstrated the analytical potency of our approach for the analysis of neonatal samples as well as its potential to be used as a pre-diagnostic tool for sepsis.