Combination of quantum dot fluorescence with enzyme chemiluminescence for multiplexed detection of lung cancer biomarkers

A new concept is proposed in this article to detect multiple cancer markers in a single sample. Quantum dot (QD) fluorescence (FL) labels were successfully combined with enzyme chemiluminescence (CL) labels for simultaneous detection of three cancer markers in human serum using just a common 96-well plate reader and with equal detection limits for the three markers. As a proof-of-concept, herein we coupled one QD FL label with two enzyme CL labels for hybrid multiplexed detection of lung cancer markers as exemplified by neuron-specific enolase (NSE), carcinoembryonic antigen (CEA) and cytokeratin fragment (Cyfra21-1). A homogeneous “sandwich-type” detection strategy was employed herein, where the bead–antibody mixture first reacts with NSE, CEA and Cyfra21-1 to initiate three immunoreactions in a single tube; and then the formed conjugates sandwiches with biotin, digoxin and fluoresceinisothiocyanate (FITC)-modified detection antibodies, and further reacts with a mixture of streptavidin QD, anti-FITC horseradish peroxidase (HRP) and anti-digoxin alkaline phosphatase (ALP) for subsequent CL and FL detection. The results show that NSE, CEA and Cyfra21-1 could be sensitively determined with a common 96-well plate reader and with equal detection limits down to the ng mL−1 level. Furthermore, the proposed method has been successfully applied to the determination of three cancer markers in human samples without cross-reaction. Because it is straightforward to adapt this strategy to detect a spectrum of other proteins by using different antibodies or aptamers, this new CL strategy might create a universal technology for developing simple biosensors in the sensitive and selective detection of multiple targets in a variety of clinical, environmental, and biodefense applications.