Label-free colorimetric aptasensor for IgE using DNA pseudoknot probe

Abstract

The development of simple and low-cost approaches to the detection of immunoglobulin E (IgE) would provide a method for the early diagnosis and prevention of atopic diseases. The current methods of detection are generally tedious, multi-step processes and are limited by the high cost of the labeled proteins. We describe here a label-free structure-switching colorimetric method for the simple measurement of IgE using DNA pseudoknot probes and gold nanoparticles. In the absence of a target the IgE aptamer probe adopts a pseudoknot conformation that dissociates a capture probe from the unmodified gold nanoparticles. However, when IgE binds to the aptamer probe, the pseudoknot is resolved, leading to a favorable hybridization between the 3' terminal loop of the aptamer probe and the capture probe; this induces the aggregation of the gold nanoparticles. As a result, the colorimetric IgE sensor using this structure-switching mechanism is sensitive, specific and convenient, and the assay works even when challenged with complicated biological matrixes such as vaginal fluids. The proposed method is expected to be of great clinical value for IgE detection and could be used, after appropriate design, for sensing applications of other structured aptamers.

Aptamers against Immunoglobulins: Design, Selection and Bioanalytical Applications

“…In colorimetric detections, nanoparticles are also frequently used as reporting agents including silver [102], gold [103,104] and carbon nanoparticles [105] and aptamer-labeled bacteriophages [106]. Aptamer-modified silver nanoparticles were used for rapid, visual IgE detection, where anti-human IgE antibodies were spotted on solid support to capture IgE and form antibody/IgE/aptamer-AgNP complex.…”

Affinity Biosensors for Detection Immunoglobulin E and Cellular Prions. Antibodies vs. DNA Aptamers

“…Although in a less extend the colorimetric and fluorescence based detection of IgE using DNA aptamers has been reported as well . Table summarizes the sensitivity of immuno and aptamer based biosensor for IgE detection.…”

A review on immobilised aptamers for high throughput biomolecular detection and screening

“…Aptamers possess the inherent ability to form secondary structures which enables them to detect and bind onto specific targets [27]. Aptamers, with the aid of their secondary structural conformation, are able to distinguish between variant targets or enantiomers based on the conformational differences in the structures of target molecules [28][29][30].…”

“…Rationally, aptamers can be modified to conformational switching with their ligand binding abilities preserved. In the absence of a target, the thermodynamically stable conformation of the aptamer is maintained [27]. In the presence of the target, the affinity between the duo induces binding to form an aptamer-target complex.…”