Salt-induced gold nanoparticles aggregation lights up fluorescence of DNA-silver nanoclusters to monitor dual cancer markers carcinoembryonic antigen and carbohydrate antigen 125

In clinical diagnosis of cancer, the monitoring of single tumor marker may result in many false and missed results, while simultaneous detection of multiple tumor markers should be more accuracy and effective. Here, we report a new strategy that salt-induced gold nanoparticles (AuNPs) aggregation lights up fluorescence of dual-color DNA-silver nanoclusters-aptamer (DNA-AgNCs-apta) for the simultaneous monitoring of carcinoembryonic antigen (CEA) and carbohydrate antigen 125 (CA125). The dual-color aptasensor system is composed of green-emitting DNA-AgNCs with CEA aptamer (gDNA1-AgNCs-apta1) and red-emitting DNA-AgNCs with CA125 aptamer (rDNA2-AgNCs-apta2) in the ratio of 1:1 in volume. Upon addition of AuNPs, gDNA1-AgNCs-apta1 and/or rDNA2-AgNCs-apta2 are flexibly adsorbed onto the surface of AuNPs by terminal aptamer(s), which prevents salt-induced AuNPs aggregation under high salt condition and results in fluorescence quenching based on surface plasmon enhanced energy transfer (SPEET). With the addition of CEA and/or CA125, the target(s) and corresponding aptamer(s) coordinate to form the complex, keeping DNA-AgNCs-apta(s) far away from the surface of AuNPs and making AuNPs aggregated in high salt medium. The AuNPs aggregation leads to the recovery of fluorescence signals of DNA-AgNCs-apta(s) due to weakened SPEET. Utilizing the fluorescence aptasensor system, the limit of detection of CEA and CA125 are as low as 7.5 pg·mL-1 and 0.015 U·mL-1, respectively. The proposed method can be applied to the selective and simultaneous determination of CEA and CA125 in human serum.