Development of Quantum Dot-Based Lateral Flow Immunoassay System for Rapid Quantitative Detection of Human Chorionic Gonadotropin

In this work, we developed a novel fluorescent biosensor that integrates a lateral flow test strip with quantum dot (QD) and a home-made test strip reader for rapid, low-cost, quantitative, and sensitive human chorionic gonadotropin (HCG) detection. The serum HCG level is a reliable marker for detecting persistent gestational trophoblastic neoplasia (GTN) and reflects the clinical course of the disease. The biosensor is designed to combine the rapidness of lateral flow immunoassay and sensitivity of fluorescent immunoassay. The principle of this biosensor is on the basis of a sandwich immunoreaction that was performed on the test strip and the QDs are captured on the test line through antibody-antigen reaction and on the control line through the immobilized secondary antibody. Quantitative detection is realized by recording the intensity of the test line and control line with our home-made test strip reader. The results are determined by the ratio of the fluorescence intensity of the test line and control line (I-T/I-C), which would cancel out the influence of the stability of QDs and antibody. The immunoreaction time and the sample volume are optimized to get a higher sensitivity. Under optimal conditions, the QD-based lateral flow immunoassay system has a wide dynamic range and is capable of detecting a minimum 0.85 IU/L HCG standard analyte in 15 min with 50 mu l sample volume. The novel QD-based lateral flow immunoassay biosensor offers a rapid, sensitive and quantitative tool for point-of-care testing of the level of serum HCG and shows great promise in other protein markers.