Aptamer-modified gold nanoparticles for rapid aggregation-based detection of inflammation: an optical assay for interleukin-6.

Abstract

A proof-of-concept aptamer-based optical assay is described for the determination of the immune signalling molecule interleukin-6 (IL-6), a key marker of acute inflammation. The optical assay is based on the aggregation of gold nanoparticles (AuNP) coated in two complimentary “sandwich-style” aptamers, each with different IL-6 target moieties. IL-6 will recognise the complimentary aptamer pair and bind to it causing the aggregation of the corresponding functionalised nanoparticles. The aggregation of the AuNPs after exposure to IL-6 induces a visible colour change from red to pink, with a corresponding change in the extinction maximum from 520 to 540 nm. The change in the extinction maximum can be monitored visually, or using a spectrophotometer or a plate reader. The optimal size and functionalisation method of aptamer-coated AuNP, and potential assay format were investigated using UV-Vis spectrophotometry, transmission electron microscopy, and dynamic light scattering. The optical assay was applied for detecting mouse IL-6 in a mixed protein 6 concentration range, and the detection limit (at S/N = 3) is 1.95 μg·mL-1. This study was performed as a proof-of-concept demonstration of this versatile assay design, with a view to developing a similar assay for use in clinical samples in future.