Dual-readout lateral flow immunoassay based on upconversion nanoparticle-gold nanoparticle luminescence resonance energy transfer for rapid determination of 17β-estradiol.

A luminescence resonance energy transfer (LRET)-regulated dual-readout lateral flow immunoassay (LFIA) is reported that integrates naked-eye colorimetric screening and near-infrared (NIR)-excited quantitative luminescence analysis on a single test strip. Core-shell upconversion nanoparticles (UCNPs) functionalized with E2-bovine serum albumin conjugates were immobilized on the test line as luminescent donors, while gold nanoparticle (AuNP)-labeled anti-E2 monoclonal antibodies served dually as colorimetric labels and efficient LRET acceptors. Time-resolved luminescence measurements confirmed an LRET efficiency of 18.8%, with the donor lifetime decreasing from 720 to 585 µs upon immunocomplex formation. Under optimized conditions, the assay was completed within 10 min. The luminescence mode exhibited a linear response over 1-500 ng/mL with a limit of detection of 1.37 ng/mL, while the visual mode enabled naked-eye discrimination at 20-40 ng/mL. This UCNP-AuNP LRET strategy provides a practical dual-readout format that balances operational simplicity and quantitative performance, offering a versatile platform for rapid on-site screening of small-molecule contaminants in complex matrices.