Viability of allergy (IgE) detection using an alternative aptamer receptor and electrochemical means

The current work describes the systematic development of a disposable electrochemical sensor based on an aptamer receptor (aptasensor). The optimal conditions for which aptamers perform have been thoroughly investigated by Enzyme Linked OligoNucleic Assay (ELONA) and manipulated to achieve sufficient sensitivity in the final sensor set-up. Parameters investigated included buffer type, reagent concentration profiling, pH, ionic effect and thermo-stability. Method transfer then allowed for the preparation of the aptasensor utilising differential pulse voltammetry as the transduction mode. The principle system chosen was for the detection of allergy (IgE), which is present in humans due to exposure to a multitude of allergens in food and/or the environment. The system incorporates a competitive format for IgE detection using a biotinylated form of the aptamer. Enzymatic role is completed by the subsequent use of an extravidin-alkaline phosphatase label for either colorimetric, or electrochemical detection. Through the careful choice of conditions the aptasensor functions at levels suitable for human testing (> 300 ng ml(-1)) and exhibits sensitivity similar to antibody-based sensors of this type. The thermo-stability of the aptamer is significantly better than a corresponding IgE antibody receptor. In addition the sensor using this aptamer receptor is robust (CV < 5%) and varies little from day-to-day (R.S.D. 8%). Recoveries of 100 5% or better were obtained for two types of ELONA. The facet that the final sensor is a disposable strip makes it a suitable candidate for decentralisation of assaying away for the laboratory environment to a point-of-care device. (c) 2006 Elsevier B.V. All rights reserved.