Sensing creatinine in urine via the iontronic response of enzymatic single solid-state nanochannels

In this study, we investigate the integration of the enzyme creatinine deiminase into solid-state nanopore walls through electrostatic assembly for the development of creatinine sensors. In these asymmetric single nanochannels, ionic transport is determined by the surface charge inside the channel, resulting in diode-like behavior that rectifies ionic current. The efficiency of such rectification depends on the surface charge density. In the presence of creatinine, the enzymatic reaction generates ammonium, leading to an increase in local pH near the channel, which can be detected through changes in transmembrane ionic transport response. Changes in rectification efficiency can be well correlated with the analyte concentration, allowing for a detection limit of 5 nM creatinine. Furthermore, this solid-state nanopore-based device is capable of sensing in diluted urine samples, showing a good linear correlation between the response and the logarithm of the creatinine concentration over a wide range of concentrations (50 nM-100 μM). These results demonstrate the potential of systems based on the integration of enzymes that induce pH changes and solid-state nanopores for the development of biomarker sensors capable of operating in complex real samples.