Fabrication of label-free electrochemical food biosensor for the sensitive detection of ovalbumin on nanocomposite-modified graphene electrode

In this work a highly sensitive label-free electrochemical food biosensor for the detection of egg allergen ovalbumin (Ova) was developed using nanocomposite consisting of iron oxide (Fe3O4) and palladium (Pd) nanoparticles with conducting polymer chitosan (CS). Pd nanoparticles were synthesized and seeded onto Fe3O4 nanoparticles, and dispersed in CS to form the nanocomposite. The nanocomposite (Fe3O4-Pd/CS) was drop-casted onto a screen printed graphene electrode (SPGE). Subsequently, 4-ABA was electrografted onto the modified SPGE/Fe3O4-Pd/CS. Carbodiimide chemistry was performed for the covalent conjugation of Ova-antibody (Ova-Ab) onto the electrode surface. The bimetallic nanocomposite portrayed excellent electrocatalytic effect due to the synergistic conductive effect of the Fe3O4-Pd nanomaterials and CS polymers and facilitated the electron movement between electrode surface and redox buffer. Additionally, ABA also enhanced electronic current on the surface of the electrode. Featuring high electron conductivity, the developed food biosensor demonstrated a large linear range to detect the Ova between 0.01 pg/mL – 1 µg/mL with a low limit of detection of 0.01 pg/mL. Furthermore, the proposed food biosensor portrayed very good selectivity with a high potential to detect Ova in real food sample.