Abstract
A proof-of-concept aptamer-based optical assay is described for the determination of the immuno 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, thereby 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 absorption maximum from 520 to 540 nm. The change in the absorption maximum can be monitored visually, or by using a spectrophotometer or a plate reader. The optimal size and functionalisation of aptamer-coated AuNPs, and the potential assay formats 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 solution as a representative biological sample. The assay works in the 3.3 to 125 μg·mL−1 IL-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.Graphical abstractSchematic representation of the aggregation of aptamer-functionalised nanoparticles in the presence of interleukin-6 (IL-6). The presence of mouse IL-6 in a mixed protein solution leads to a visible colour change, and a change in the absorption spectrum of the nanoparticles.
Highlights
IntroductionInflammation, the body’s immune response to infection or injury, plays a key role in almost all pathological conditions
Electronic supplementary material The online version of this article contains supplementary material, which is available to authorized users.Inflammation, the body’s immune response to infection or injury, plays a key role in almost all pathological conditions
High levels of IL-6 measured in cerebrospinal fluid (CSF) and plasma have been associated with pathological inflammation leading to poor clinical outcome in patients with brain injuries, such as traumatic brain injury (TBI)
Summary
Inflammation, the body’s immune response to infection or injury, plays a key role in almost all pathological conditions. There is increasing evidence that early detection of inflammatory molecules can enable timely clinical intervention with potentially life-saving consequences for patients. This is true for pathological conditions in hidden environments such as the brain, where changes in inflammatory processes are not always immediately obvious from a clinical perspective. Interleukin-6 (IL-6) is an immune molecule associated with acute inflammation, in response to recent infection or injury [1]. High levels of IL-6 measured in cerebrospinal fluid (CSF) and plasma have been associated with pathological inflammation leading to poor clinical outcome in patients with brain injuries, such as traumatic brain injury (TBI)
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