One-Component Dual-Readout Aggregation-Induced Emission Nanobeads for Qualitative and Quantitative Detection of C-Reactive Protein at the Point of Care.

Fluorescent lateral flow immunoassay (LFA) systems are versatile tools for sensitive and quantitative detection of disease markers at the point of care. However, traditional fluorescent nanoparticle-based lateral flow immunoassays are not visible under room light, necessitate an additional fluorescent reader, and lack flexibility for different application scenarios. Herein, we report a dual-readout LFA system for the rapid and sensitive detection of C-reactive protein (CRP) in clinical samples. The system relied on the aggregation-induced emission nanobeads (AIENBs) encapsulated with red AIE luminogen, which possesses both highly fluorescent and colorimetric properties. The AIENB-based LFA in the naked-eye mode was able to qualitatively detect CRP levels as low as 8.0 mg/L, while in the fluorescent mode, it was able to quantitatively measure high-sensitivity CRP (hs-CRP) with a limit of detection of 0.16 mg/L. The AIENB-based LFA system also showed a good correlation with the clinically used immunoturbidimetric method for CRP and hs-CRP detection in human plasma. This dual-modal AIENB-based LFA system offers the convenience of colorimetric testing and highly sensitive and quantitative detection of disease biomarkers and medical diagnostics in various scenarios.

Fluorescent Lateral Flow Immunoassay Based on Quantum Dots Nanobeads.

Quantum dots, also known as semiconductor nanocrystals, are novel fluorescent labels for biological imaging and sensing. However, quantum dot-antibody conjugates with small dimensions (~10 nm), prepared through laborious purification procedures, exhibit limited sensitivity in detecting certain trace disease markers using lateral flow immunoassay strips. Herein, we present a method for the preparation of quantum dot nanobeads (QDNB) using a one-step emulsion evaporation method. Using the as-prepared QDNB, a fluorescent lateral flow immunoassay was fabricated to detect disease biomarkers using C-reactive protein (CRP) as an example. Unlike single quantum dot nanoparticles, quantum dot nanobead-antibody conjugates are more sensitive as immunoassay labels due to signal amplification by encapsulating hundreds of quantum dots in one polymer composite nanobead. Moreover, the larger size of QDNBs facilitates easier centrifugation separation when conjugating QDNBs with antibodies. The fluorescent lateral flow immunoassay based on QDNBs was fabricated, and the CRP concentration in the sample was measured in 15 min. The test results can be qualitatively assessed under UV light illumination and quantitatively measured using a fluorescent reader within 15 min.