An electrochemical biosensor with engineered Co-N active sites loaded on humic acid for catalyzing and detecting of biomolecules

Humic acid (HA), a natural organic matter (NOM), exhibits high biocompatibility, low toxicity and antioxidant properties, making it highly suitable as a biosensing interface for capturing, binding, catalyzing and detecting diverse biomolecules. However, the inherently poor conductivity of HA has resulted in very few studies on its electrochemical catalysis and detection of biomolecules. This study focused on the Co-N active sites supported on nitrogen-doping HA (N-HA), primarily investigating their electrochemical catalytic performance towards various biomolecules and biosensing capability for characteristic biomolecules. Both N doping and Co loading on HA increased surface area, enhanced conductivity, promoted electron transfer, and boosted detection sensitivity. The engineered Co-N active sites possessed the capability to selectively catalyze diverse biomolecules including dopamine (DA), ascorbic acid (AA), uric acid (UA) and 5-hydroxytryptamine (5-HT), which improved the anti-interference property. Developed biosensor based on Co@N-HA achieved sensitive detecting of DA and AA with the extremely low catalyzing potentials (0.20 V for DA, 0.25 V for AA), the wide linear ranges, the low limits of detection (LODs, 1.03 μM for AA, 1.21 μM for DA) and limits of quantification (LOQs, 3.40 μM for AA, 4.03 μM for DA), accompanied by high reproducibility and stability. Biosensor enabled reliable target detection in biological fluids, including artificial sweat and kiwifruit juice, with high selectivity and sensitivity, declaring its robustness for practical applications. The work expanded the application of HA in electrochemical biosensing field.