Fabrication of immunogolobulin E (IgE) Aptasensor Based on Immobilization of Aptamer and Methylene Blue onto Glassy Carbon Electrode Modified with Ionic Liquid/Multi-Walled Carbon Nanotubes/Chitosan Nanocomposite

Aptamers are synthetic RNA or DNA single-stranded oligonucleotide sequences folding into different three-dimensional shapes that exhibit high specificity and affinity for a target molecule [1]. In recent years, aptamers, single-stranded oligonucleotides, have been promoted as ideal diagnostic reagents and potential antibody replacements for the development of biorecognition nanosensors due to their high affinity, specificity and stability [2].Aptamers are obtained by an in vitro process called SELEX (Systematic Evolution of Ligands by EXponential enrichment) that, in principle, allows the selection of an aptamer against any kind of target molecule, ranging from ions to whole cells or bacteria. The use of aptamers for the detection of small molecules still represents a challenge because of the lower affinity interaction when compared with large molecules[3]. Immunoglobulin E (IgE), one of the five classes of antibodies in the human immune system, which accounts for a minute proportion of immunoglobulin in the blood, is mainly responsible for immediate-type hypersensitivity reactions, causing common allergic diseases such as asthma and hay fever [4].In this paper, a simple, label-free and regenerative method was proposed to study the interaction between aptamer and small molecule, using methylene blue (MB+) as an electrochemical indicator. An amino aptamer and (MB+) was immobilized on glassy carbon electrode which modified with nanocomposite containing ionic liquids, multi-walled carbon nanotubes and chitosan. Using this system, sensitive quantitative detection of IgE is realized by monitoring differences of differential pulse voltammetric responses of electrostatically trapped MB+ cations to the MB can specically bind with G base backbone of the conjugated aptamer before and after IgE binding. The peak current of MB+ linearly decreased with the concentration of IgE over a range of 0.5-30nMwith a detection limit of 37pM. In ddition, we examined the selectivity of this electrochemical biosensor for bovine serum albumin (BSA), lysozyme that belonged to the nucleosides family and possessed a similar structure with IgE. Finally the proposed aptasensor was used to detect IgE in human serum samples.

Aptamer Immunoglobulin E (IgE) methylene blue