Development of an Immunomagnetic Electrochemical Sensor for Detection of BT‐CRY1AB/CRY1AC Proteins in Genetically Modified Corn Samples

Abstract

The aim of the present work was the development of an immunomagnetic electrochemical sensor (IMES) for a simple and fast detection of Bt‐Cry1Ab/Cry1Ac proteins in genetically modified corn flour. The IMES is based on a sandwich format using magnetic beads as immobilization support and disposable screen‐printed electrodes (SPEs) as electrochemical transducers. An alkaline phosphatase labeled antiglobulin (Ab₂‐AP) was used to reveal the sandwich complex between monoclonal anti‐Cry1Ab antibodies (MAb), Cry1Ab protein, and polyclonal anti‐Cry1Ab antibodies (PAb). After the immunochemisty steps, the beads were localized onto the surface of the SPEs with the aid of a magnet, prior to the addition of the enzyme substrate (1‐naphthylphosphate) and the measurement of the electroactive product. The current response was found to be directly proportional to the concentration of Cry1Ab protein. The limit of detection was calculated to be 0.1 ng mL⁻¹ with a working range between 0.25 and 4 ng mL⁻¹ and a total analysis time of about 3 h.

This method, which was also able to detect Cry1Ac protein, was applied to genetically modified corn samples. After optimization of the extraction procedure certified reference materials (CRMs) with different mass fractions (0.5%, 1%, 2%, 5%) of dried powder prepared from genetically modified (MON 810) maize, were treated and analyzed in replicate in order to assess, in our conditions, the correspondence between the % of genetically modified material and the concentration of Cry1Ab protein (ng g⁻¹). Finally, certified reference material with 0% of genitically modified organism (GMO), two maize samples with unknown % of GMO and the two corresponding control samples (with no GMO) were analyzed in order to verify the effectiveness of the IMES‐based assay.

Keywords:

• GMO
• screen‐printed electrodes
• immunomagnetic beads

This work was supported by the Ministry of Health, Programma di Ricerca Finalizzata 2002, Project: Metodi analitici rapidi e innovativi per l'analisi e il controllo di OGM ed alimenti contenenti o prodotti a partire da OGM.