Screen-printed electrode modified with a composite based on Amburana cearensis gum, multi-walled carbon nanotubes, and gold nanoparticles for electrochemical determination of total isoflavones in soybean cultivars

Soy isoflavones (Glycine max) are important bioactive compounds that benefit human health and contribute to the plant’s defense against herbivory. However, the concentration of these isoflavones can vary depending on the soybean strain and growing conditions, making it important to develop alternative methods for monitoring their content. This study developed a portable sensor capable of amplifying the isoflavone analytical signal 10 times from the chemical modification of a commercial screen-printed electrode (SPE). The modification of the SPE surface was carried out using a composite based on multi-walled carbon nanotubes (MWCNTs) associated with gold nanoparticles (AuNPs) stabilized with Amburana cearensis gum (GAmb). After its preparation, the SPE/AuNPs-MWCNTs-GAmb was electrochemically characterized and evaluated for the presence of genistein, the isoflavone aglycone majority present in soybeans, and was therefore adopted as an experimental model. This study also suggested the oxidation-reduction mechanism of genistein on the surface of the developed electrode and evaluated the detection of genistein in the presence of rutin, one of its main interferents. Genistein recovery was close to 100% in soy extract samples, and the sensor exhibited a linear range between 0.15 and 20.0 µM and an LD (detection limit) of 0.046 µM. Finally, the total isoflavone content was quantified in three different soybean seed samples, demonstrating that the portable sensor can support genetic improvement studies regarding the production of these bioactive compounds.