A Promising CdSe@CdS-Quantum Dots-Cysteine for the Determination of Trace IgE by Solid Substrate Room Temperature Phosphorescence Immunoassay

摘要

The labelling reagent CdSe@CdS-QDs-Cys (QDs-Cys) with the grain diameter of 4.5 nm was synthesized by modifying CdSe@CdS quantum dots (QDs) with cysteine (Cys). At the same time, QDs-Cys-Ab_IgE, a phosphorescent quantum dot probe, was developed based on the labelling reaction between -COOH of QDs-Cys and -NH₂ of goat anti human IgE antibody (Ab_IgE). This probe with excellent biocompatibility and high specificity could not only emit strong and stable room temperature phosphorescence (RTP), but also could carry out specific immunoassay (IA) with immunoglobulin E (IgE), causing the RTP of the system to sharply enhance. Thus, a new solid substrate room temperature phosphorescence immunoassay (SSRTPIA) for the determination of IgE was established. The limit of quantification (LOQ) of the method was 0.12 fg spot−1, corresponding concentration was 3.0 × 10−13 g mL−1 and sampling quantity was 0.40 μL spot−1. This highly selective, sensitive and accurate SSRTPIA has been applied to determine IgE in biological samples and diagnose diseases, and the results agreed well with those obtained by enzyme-link immunoassay (ELISA). Meanwhile, the mechanisms of QDs-Cys labelling Ab_IgE and the determination of IgE by SSRTPIA were also discussed.