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Graphene quantum dots-based nano-biointerface platform for food toxin detection

Bhardwaj, Hema, Singh, Chandan, Kotnala, R. K., Sumana, Gajjala
Analytical and bioanalytical chemistry 2018 v.410 no.28 pp. 7313-7323
European Union, Raman spectroscopy, aflatoxin B1, chemical bonding, corn, detection limit, dielectric spectroscopy, electrochemistry, electrodes, electron transfer, electrophoresis, glass, graphene, graphene oxide, immunosensors, indium tin oxide, monoclonal antibodies, photoluminescence, quantum dots, scanning electron microscopy, transmission electron microscopy, ultraviolet-visible spectroscopy
Due to the similar electrochemical properties to graphene oxide (GO), graphene quantum dots (GQDs) are considered as a highly potential candidate for designing an electrochemical biosensor. In this report, GQDs were synthesized having an average diameter of 7 nm and utilized for the fabrication of an electrochemical immunosensor for the detection of food toxin, aflatoxin B₁ (AFB₁). An electrophoretic deposition technique was utilized to deposit the chemically synthesized GQDs onto indium tin oxide (ITO)-coated glass substrate. Further, the monoclonal antibodies of AFB₁ were covalently immobilized onto deposited electrode GQDs/ITO using EDC-NHS as a crosslinker. The structural and morphological studies of GQDs and conjugated anti-AFB₁ with GQDs have been investigated using UV-visible spectroscopy, photoluminescence spectroscopy, Raman spectroscopy, transmission electron microscopy, scanning electron microscopy techniques, etc. The electrochemical impedance spectroscopy and cyclic voltammetry measurements were carried out for electrical characterization and biosensing studies. This simple monodisperse GQDs-based platform yields heterogeneous electron transfer (97.63 × 10⁻⁵ cm s⁻¹), the time constant (0.005 s) resulting in improved biosensing performance. The electrochemical immunosensor shows high sensitivity 213.88 Ω (ng mL⁻¹)⁻¹ cm⁻². The limit of detection for standard samples and contaminated maize samples was found to be 0.03 ng mL⁻¹ and 0.05 ng g⁻¹, respectively, which is lower than the maximum acceptable limit according to the European Union. This result indicates its potential application for aflatoxin B₁ detection in food contents. Graphical abstract ᅟ