Nanoengineered electrochemical sensor for trace-level monitoring of perfluorooctanoic acid in aqueous environments using electroactive molecularly imprinted nanoparticles

Summary

A new voltammetric sensor was developed for the sensitive and selective detection of perfluorooctanoic acid (PFOA) in water. The sensor is based on molecularly imprinted polymer nanoparticles (nanoMIPs) labelled with a redox-active moiety, which imparts electrochemical properties to the polymer. These nanoMIPs were synthesized using solid-phase polymerization, with their size optimized through chemometric modelling, including functional monomer screening and recognition cavity design. The optimization aimed to minimize the nanoMIP size, which is directly influenced by the amount of polymerization initiator, and to enhance sensor response. A commercially available screen-printed platinum electrode (SPPtE) served as the transducer element, functionalized with APTES to enable covalent attachment of nanoMIPs. The sensor demonstrated a detection capability for PFOA concentrations as low as 0.40 ± 0.03 pg mL⁻¹, and a linear response up to 7.5 pg mL⁻¹. Furthermore, the calibration curve was fitted to the Michaelis-Menten model, thanks to the allosteric behavior of the nanoparticles mimicking enzyme-substrate interactions. A Km of 4.34 pg mL⁻¹ for MIP and 17.73 pg mL⁻¹ for the control were obtained. Its selectivity was evaluated in samples containing structurally similar PFAS compounds, showing high effectiveness also in contaminated water. Additionally, a successful regeneration strategy was developed, enabling the sensor to be used across at least 3 work cycles. The successful adaptation of the developed method to a handheld miniaturized potentiostat connected to an Android phone enables on-site inspections of surface waters at the point of need.