A rapid triple-mode fluorescence switch assay for immunoglobulin detection by using quantum dots-gold nanoparticles nanocomposites

Abstract

The immunoglobulins, most of them are glycoprotein, play an important role on humoral immune. We herein report a triple-modenano sensor with a fluorometric readout based on CdTe quantum dots (QDs) and gold nanoparticles (AuNPs) for discriminative detection of immunoglobulin. Immunoglobulins fall into several classes, each with its own functional characteristics. In this research, we use chicken egg yolk immunoglobulin (IgY) as an example to establish the specific detection methods. IgY is the only antibody existing in chicken egg yolk, which has many significant advantages. We used anti-IgY and staphylococcal protein A (SPA) to make the detection discriminatively to IgY. The immune interaction between QDs-SPA and anti-IgY-AuNPs leads to drastic quenching (turning off) of the donor by a fluorescence resonance energy transfer (FRET) process. After the addition of IgY, anti-IgY-AuNPs peel off from the QDs-SPA surface and bind to IgY due to competitive immunoreactions, resulting in the restoration of the fluorescence intensity of QDs (turning on). Consequently, this process can be utilized for the selective detection of IgY via optical responses. This proposed assay demonstrated a favorable anti interference ability and highly selectivity toward IgY with a detection limit of 1.16ng/mL. More importantly, the nanosensor could not only function in aqueous solution for IgY detection with high sensitivity but also exhibit sensitive responses toward IgY in complicated biological environments, demonstrating its potential in bioanalysis, which might be significant in biochemical field in the future.