An ultrasensitive fluorescence aptasensor for carcino-embryonic antigen detection based on fluorescence resonance energy transfer from upconversion phosphors to Au nanoparticles
A novel fluorescence resonance energy transfer (FRET)-based aptasensor was proposed for carcino-embryonic antigen (CEA) detection utilizing NaYF4:Yb3+, Er3+ upconversion nanoparticles (UCNPs) and gold nanoparticles (Au-NPs) as the energy donor and acceptor, respectively. The FRET process occurs when the single-stranded DNA modified UCNPs and Au-NPs are linked together by the CEA aptamer, which leads to the fluorescence quenching of UCNPs. However, the presence of CEA splits the above fluorescence-suppressed Au-NPs–aptamer–UCNPs sandwich complex, resulting in the fluorescence recovery of UCNPs. The recovery of fluorescence intensity is linearly correlated to the concentration of CEA in the range of 0.05–2.0 ng mL−1, enabling the detection and quantification of CEA. Such a sandwich-type FRET-based assay possesses a low limit of detection (0.02 ng mL−1) and satisfactory selectivity and reproducibility, indicating that this biosensor is applicable for the trace detection of the CEA protein.