NaYF4:Yb,Er Upconversion Nanotransducer with in Situ Fabrication of Ag2S for Near-Infrared Light Responsive Photoelectrochemical Biosensor.

An innovative near-infrared (NIR) light-driven photoelectrochemical (PEC) aptasensor was constructed for sensitive screening of carcinoembryonic antigen (CEA) on the basis of in situ formation of Ag2S nanoparticles on the NaYF4:Yb,Er upconversion nanoparticles (UCNs), coupled with hybridization chain reaction (HCR) for the signal amplification. Utilization of UCN as the light nanotransducer could convert the NIR light into an applicable wavelength harvested by semiconductors. The multiemissions of NaYF4:Yb,Er UCN could match well with the absorption characteristics of Ag2S. In the presence of target CEA, a sandwich-type reaction was carried out between capture CEA aptamer/NaYF4:Yb,Er-modified electrode and trigger CEA aptamer, which underwent an unbiased strand-displacement reaction to open C-rich hairpin probes in sequence between two alternating hairpins with the assistance of C-Ag+-C chelation reaction. Upon addition of sulfide, the chelated Ag+ ions in the long-nicked DNA poly strands by hybridization chain reaction reacted with sulfide to generate Ag2S nanoparticles. The formed Ag2S could utilize effectively the upconversion emissions to amplify the photocurrent. Under optimal conditions, NaYF4:Yb,Er-based NIR light-responsive PEC aptasensing platform exhibited high sensitivity for the determination of CEA within a dynamic linear range of 0.005-5.0 ng mL-1. The limit of detection was 1.9 pg mL-1. Good precision and high specificity could be acquired in this system for the analysis of target CEA. Human serum samples containing target CEA were measured using our strategy and received well-matched results relative to human CEA enzyme-linked immunosorbent assay kits. Importantly, the NaYF4:Yb,Er-based NIR light-responsive PEC aptasensing system provides a new ideal for the detection of disease-related biomarkers using a nucleic acid-based amplification strategy.