A label-free and enzyme-free ratiometric fluorescence biosensor for sensitive detection of carcinoembryonic antigen based on target-aptamer complex recycling amplification

Sensitive detection of cancer biomarker is of great importance for early accurate diagnostics and therapy of cancer patients. Herein, a label-free and enzyme-free ratiometric fluorescence biosensor is developed for the detection of carcinoembryonic antigen (CEA) based on a recycling amplification strategy. CEA could trigger the release of G-quadruplex sequences from a DNA machine in the presence of hairpin DNA (H-DNA) with an aptamer fragment and the split of the silver nanoclusters (AgNCs) pair in the presence of fuel DNA (F-DNA), resulting in an enhanced fluorescence of Thioflavin T (THT) and a decline fluorescence of the AgNCs pair. The novel ratiometric fluorescence biosensor prevents the cumbersome functionalization process and the shortcoming of enzyme-based amplification strategy. Under the optimal conditions, the present biosensor achieves a detection limit of 0.1 ng mL(-1) and a linear range of 0.5-20 ng mL(-1) for CEA, which is superior to the single-signal strategy based on THT or AgNCs. The practical applicability of the present biosensor is demonstrated by the detection of CEA in human serum with satisfactory results, thus it shows great potential in future clinical diagnosis. (C) 2017 Elsevier B.V. All rights reserved.