Voltammetric genosensor from silica nanocomposites for transgenic soybean analysis

Abstract

The introduction of genetically modified organisms (GMOs) to crops has rendered continuous concern and debates on GM foods, which led to the requirement of appropriate labelling of GMO-derived products and the demands of advanced technologies for on-site detection of transgenic crops. In this study, an electrochemical genosensor for rapid, ultrasensitive, and specific determination of cauliflower mosaic virus (CaMV35S) gene in GM soybean based on silica-gold nanoparticles composite electrode was developed. Colloidal gold nanoparticles were drop-coated onto a carbon screen-printed electrode (SPE) followed by amine-functionalized silica nanospheres to obtain a SiO₂-Au nanocomposite electrode (SiO₂-Au-SPE). Aminted DNA probes were grafted onto the SiO₂-Au-SPE using glutaric dialdehyde crosslinking agent. Meanwhile, thiolated DNA probes were directly chemisorbed onto the AuNPs-modified SPE for comparison purposes. Under optimum conditions, the DNA biosensor based on SiO₂-Au-SPE could determine the target CaMV35S gene in a linear DNA concentration range of 1.0 × 10⁻¹⁴ M to 1.0 × 10⁻⁸ M, with a limit of detection (LOD) of 2.37 fM cDNA. Glutaraldehyde crosslinking of aminated DNA probe to the aminated SiO₂ nanospheres attained stronger bonding strength with a 10-fold higher calibration sensitivity towards cDNA compared to direct chemisorption of thiolated DNA probe to the AuNPs by thiol chemistry. The validation study showed that the electrochemical DNA biosensor based on SiO₂-Au nanocomposite electrode was comparable to the conventional polymerase chain reaction (PCR) method for the evaluation of transgenic soybean contents in soy food samples, with 99.1–101.3 % recoveries of GM DNA.