Fast impedimetric immunosensing of IgGs associated with peanut and hazelnut allergens

Food allergies trigger a variety of clinical adverse symptoms and clinical evidence suggests that the presence of food allergy-related IgG can be helpful in the diagnosis when analyzed at the peptide-epitope level. To validate and select the peptides based on their specificity toward hazelnut or peanut epitopes, the authors of this study developed a silicon-based microchip coupled with click-chemistry bound peptides identified by the Fraunhofer Institute for Cell Therapy and Immunology. Peptides related to hazelnut and peanut allergies were identified and used to develop a silicon-based microchip. Peptides were coupled with click-chemistry to the sensor surface. The immunosensor was developed by electrografting diazotized amino phenylacetic acid and subsequently, dibenzocyclooctyne-amine (DBCO-NH2) was used as click-chemistry to allow coupling of the peptides with a C-terminal linker and azide structure. Energy-dispersive X-ray spectroscopy, electrochemical impedance spectroscopy (EIS), and fluorescence microscopy techniques have been used to analyze the bio-functionalization of the developed electrode. The peptide-epitope recognition was studied for seven allergen-derived peptides. The electrochemical responses were studied with sera from rabbits immunized with hazelnut and peanut powder. The microchips functionalized with the chosen peptides (peanut peptides T12 and EO13 and hazelnut peptides S4 and EO14 with an RSD of 4%, 3%, 9%, and 1% respectively) demonstrated their ability to specifically detect prevalent anti-nut related IgGs in rabbit sera in a range of dilutions from 1:500000 (0.0002%) until 1:50000 (0.002%). In addition, the other peptides showed promising differentiation abilities which can be further studied to perform multivariable detection fingerprint of anti-allergens in blood sera.