Author:

Keywords:

Aptamer, Biosensor, Human IgE, Electrochemical Impedance Spectroscopy, nanocrystalline diamond

Abstract:

Like antibodies, aptamersare highly valuable as bioreceptor molecules for protein biomarkers because of their high selectivity, specificity and stability. However, unlike antibodies, they also recognize a wide range of non-immunogenic targets such as small molecules and even whole cells.The integration of aptamers with semiconducting materials offers a great potential for the development of reliable aptasensors. Besides the wide target range, aptasensorsalso have the advantage of easy regeneration for multiple usedue to the stability and denaturation properties of the nucleic acid receptors. In this paper we presentan aptamer-based impedimetric biosensor using a nanocrystalline diamond (NCD) film as a working electrode for the direct and label-free detection of human IgE.About 1 to 3% of the adults and up to 8% of the children show an allergic reaction after the consumption of certain food products resulting in an increased level of IgE in the blood serum. IgE blood levels are typically in the nanomolar range. Amino-terminated IgEaptamersarecovalently attached to carboxyl-modified NCDsurfaces using carbodiimidechemistry, followed by BSA treatment to prevent non-specific binding of IgE. Electrochemical impedance spectroscopy is applied to measure the changes in interfacial electrical properties that arise when the aptamer-funtionalized NCDsurface is exposed to solutions containing human IgE. During incubation, the formation of aptamer-IgE complexes causesan increase in the imaginary part of the impedance signal. A corresponding electrical circuit analysis reveals a correlation between the complex formation and the capacitance of the double layer. The biosensor detection limit reaches physiologically relevant concentrations in the low nanomolar range (2.7 nM) and demonstrates to be highly selective even in the presence of a large excess of IgG. The integrationof the NCD substrate with aptamer technology results in an ultra-stable sensor allowingfor repeated measurements.