An upconversion FRET biosensor using ATRP-grafted polymer brushes as a signal amplifier for ultrasensitive detection...

The rapid and sensitive detection of cytokeratin 19 fragment (CYFRA21-1) is essential for the early screening and diagnosis of lung cancer. Herein, we developed a novel fluorescence resonance energy transfer (FRET) biosensor based on upconversion nanoparticles (UCNPs), incorporating an atom transfer radical polymerization (ATRP) signal amplification strategy for the rapid and sensitive detection of CYFRA21-1. The FRET biosensor employs UCNPs, which exhibit a low biological background signal and high quantum yield, as the energy donor, and gold nanoparticles (AuNPs) as the energy acceptor. The distance between the energy donor and acceptor is reduced through specific antigen/antibody interactions, leading to the quenching of the donor luminescence signal. The grafting of UCNPs on specific antibodies via ATRP can significantly enhance the quenching of fluorescence signal, thus improving the detection sensitivity. Under optimal conditions, the biosensor demonstrated a linear range of 1 ng/mL ∼ 60 ng/mL with a detection limit of 0.66 ng/mL. Furthermore, the biosensor exhibited high accuracy, selectivity, and robust anti-interference capabilities in the presence of complex biological matrices. This versatile sensing platform can be readily adapted for various targets, holding great promise for applications in medical diagnostics, environmental monitoring, and food safety.