A promising voltammetric biosensor based on glutamate dehydrogenase/Fe3O4/graphene/chitosan nanobiocomposite for sensitive ammonium determination in PM2.5.

Abstract A novel NH 4 + voltammetric electrochemical biosensor was constructed by immobilizing glutamate dehydrogenase (GLDH)/Fe 3 O 4 /graphene (GR)/chitosan (CS) nanobiocomposite onto a glassy carbon electrode (GCE). On the GLDH/Fe 3 O 4 /GR/CS/GCE, GLDH catalyzed the reversible reaction, i.e., the reductive amination of α-ketoglutaric acid and the oxidative deamination of L-glutamate. The electrons produced in the enzymatic reactions were transferred to the surface of the electrode via the [Fe(CN) 6 ]3−/4− couple, which helped for the amplification of the electrochemical signal. The electrochemical detection of NH 4 + was based on the fact that the enhanced response current was proportional to the NH 4 + concentration. Owing to the combination of the advantages of the synergistic effects of Fe 3 O 4 nanospheres, GR and CS, a promising platform for NH 4 + sensing was provided. Under optimum conditions, the introduced biosensor had a linear range of 0.4–2.0 μM for NH 4 + with the detection and quantification limits of 0.08 and 0.27 μM, respectively. Moreover, the biosensor exhibited good sensitivity and excellent reproducibility. It could retain 91.8% of its original response after two weeks of storage at 4 °C, suggesting satisfactory stability. Additionally, the proposed biosensor was successfully applied to detect NH 4 + levels in PM 2.5 samples, indicating its feasibility for application in NH 4 +monitoring in the environmental fields. Graphical abstract fx1 Highlights • Fe 3 O 4 /graphene/chitosan nanocomposite was synthesized and characterized. • The proposed composite provided a good loading platform for glutamate dehydrogenase. • NH 4 + in PM 2.5 was successfully assayed by the developed biosensor. • This biosensor provided a convenient and low-cost method for NH 4 + detection in PM 2.5. [ABSTRACT FROM AUTHOR]