Cu-N-doped graphene/prussian blue interface enables molecularly imprinted electrochemical sensing of L-kynurenine

L-kynurenine is a key metabolite of the tryptophan-kynurenine pathway and an emerging biomarker associated with immune dysregulation, inflammation, and metabolic disorders. However, its quantification typically relies on chromatographic or mass spectrometric techniques that require complex instrumentation and centralized laboratories. Here we report a molecularly imprinted electrochemical sensing platform enabled by a Cu-N-doped graphene (Cu-N-Gr)/Prussian Blue (PB) interfacial architecture for sensitive detection of L-kynurenine. The Cu-N-Gr layer provides a conductive scaffold with abundant electroactive sites that promote uniform PB deposition and facilitate efficient interfacial electron transfer. A molecularly imprinted polypyrrole layer was formed by electropolymerization in the presence of L-kynurenine and 3-aminophenylboronic acid, followed by electrochemical template removal to generate selective binding cavities. Using square wave voltammetry, the sensor exhibits a linear response from 0.001 to 10 μM with a limit of detection of 0.5 nM and an imprinting factor of 5.44. The platform shows good reproducibility and stability (RSD <5%) and enables reliable detection in phosphate buffer and artificial urine. Integration into a capillary-driven microfluidic chip enables analysis of 100 μL samples within ∼16 min using portable electrochemical readout, supporting decentralized metabolite monitoring.